..^a^^''^'^"^

Nitrogen and Carbon Changes

in Great Plains Soils as

Influenced by Cropping

and Soil Treatments

Technical Bulletin

No. 1164

UNITED STATES DEPARTMENT OF AGRICULTURE

in cooperation with State Agricultural Experiment Stations
Technical Bulletin No. 1164

September T957 ,

Hi

Nitrogen and Carbon Changes

in Great Plains Soils as

Influenced by Cropping

and Soil Treatments^

by H. J. Œ[aaB aod C. !Çl.\JËvansy Boil scientists.

Soil and Water Conservation ¡Research Division» j

Agricultural Research Service; and E. F4jfliles, -

former physicist. Agricultural Research Service

Uî«TED-SJ:ATê&- DEPARTMENT OF AGRICULTURE ,

In cooperation with the Agricultural Experiment Stations ofNorth Dakota, South

Dakota, Montana, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, and Texas
CONTENTS

Page

Description of experimental areas 2

Locations 2

Climate 5

Collection and preparation of samples 6

Total nitrogen and carbon study. 6

Soluble-nitrogen study 7

Analytical procedures 8

Relationship between soil nitrogen and particle size 8

Comparison of nitrogen and carbon content of virgin and cropped soils 11

Rate of decline in soil nitrogen with years of cropping 15

Influence of specific cropping practices on the total nitrogen and carbon content

and the carbon/nitrogen ratio of the soil 16

Effects of small grains 17

Continuous cropping versus fallow for small grains and row crops 18

Barnyard manure versus no manure 22

Effects of green-manure crops on soil nitrogen and carbon 24

Effects of grass and alfalfa on nitrogen and carbon changes 27

Soil nitrogen in relation to nitrification rate and uptake of nitrogen by plants.. 30

Laboratory studies 30

Relationship of total nitrogen in the soil and nitrate production during a 6-

week incubation period 31

Relationship of total nitrogen in the soil and nitrate-nitrogen production

during 6, 12, 18, and 24 weeks of incubation 33

Nitrate-nitrogen production from cropped soils as compared with that from

virgin sod 36

Effects of previous crop or fallow on nitrate production 37

Field studies 38

Nitrogen uptake by wheat in relation to nitrogen content of soil 38

Effects of barnyard manure on nitrogen content and yield of wheat during

one season at several locations 39

Effects of soil-nitrogen changes on crop yields 42

Summary 53

Literature cited 55

Appendix tables 58

For sale by the Saperintendent of Docnmenta, U. S. Goyeinment Printing Office

Waahington 25, D. G. - Price 35 centa
Nitrogen and Carbon Changes in Great

Plains Soils as Influenced by Cropping

and Soil Treatments^

By H. J. Haas and C. E. Evans, soil scientists. Soil and Water Conservation Research

Division, Agricultural Research Service; and E. F. Mues,* former physicist. Agricultural Research Service.

Numerous investigations have shown that there has been a sharp

decUne in nitrogen and carbon content of the soil after the land has been

Sut under cultivation. The majority of these investigations were conucted in the more humid regions. A few such studies, however, were

carried on in the Great Plains. In some instances, these studies showed

nitrogen and carbon losses as high as those in the more humid regions.

Rüssel (37y reported that the soils studied in Nebraska had lost from

25 to 30 percent of their organic matter after 30 years of cropping.

Gainey and coworkers (iô), working with soils from experiment stations

in western Kansas, showed that large losses of nitrogen had resulted from

cropping. Myers and coworkers (33) showed that these same soils

continued to decline with further cropping. Newton and coworkers (34)

reported upon analyses of soils in Alberta, Saskatchewan, and Manitoba,

Canada. The average period of cultivation was a Uttle over 22 years.

Nitrogen lost, compared with that lost from virgin sod, ranged from 0 to

40 percent. The average loss in soil nitrogen was 18 percent for brown,

dark brown, and black soils, and 30 percent for gray soils. Volkerding

and Stoa (47) studied the changes in soil nitrogen imder rotation systems

of farming at Fargo, N. Dak., and found that, over a 33-year period,

soil nitrogen had been reduced 20 percent. Chang (9), working in the

Tucumcari region in northeastern New Mexico, reported that surface

soils which had been cropped for an average of 22 years lost 31 percent

nitrogen and 44 percent organic matter.

In contrast to these results, Stewart (43) and Stewart and Hirst (44)

reported on early work done in Utah, where no decline in soil nitrogen

occurred when wheat had been grown for periods of 10 to 50 years. They

stated that the deep-rooted wheat plants were able to secure a portion

of their nitrogen from the lower depths of soil. They also stated that

the plowing under of the straw and stubble tended to maintain the

nitrogen content of cultivated surface soils.

As large losses of nitrogen and carbon from dryland soils in the Great

Plains were measured at several locations, it was decided in 1947 to make

a comprehensive study of the problem.^

*Mr. Miles is deceased. He was a member of the former Bureau of Plant Industry,

Soils, and Agricultural Engineering.

^ Submitted for publication December 1956.

^ Italic numbers in parentheses refer to Literature Cited, p. 55.

' The authors are indebted to Lyle T. Alexander, Chief, Soil Survey Laboratories,

Sou Conservation Service, and O. R. Mathews (retired), former agronomist. Soil and

Water Conservation Research Branch, Agricultural Research Service, for assistance

and guidance in planning and conducting this study.

1
2 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

The purposes of the study were: To determine the effect of cropping

on the total nitrogen and carbon contents of various dryland soils; to

evaluate the relationship of total nitrogen in the soil to the capacity of

that soil to produce nitrate-nitrogen; and to show the influence of the

soil-nitrogen changes on crop yields.

The majority of the soil and plant samples reported upon were collected from selected experimental stations located throughout the Great

Plains. Soil samples were also collected from privately owned farmland

in North Dakota.

Description of Experimental Areas

Locations

In the early part of the 20th century, experimental stations were

estabUshed at various locations throughout the Great Plains to study

the effects of different rotations and tillage practices on crop production

under dryland conditions. Where practicable, cropping treatments were

similar at all stations and were in effect for a period of 30 to 40 years.

These stations provided excellent opportunities to study nitrogen problems as influenced by different cropping treatments over a wide range of

soil and climatic conditions. However, there were two rather serious

limitations; the lack of repUcation of rotations at each station; and the

fact that, in most instances, no soil samples were taken at the time the

rotations were estabhshed.

In 1947, a survey * of these experimental stations was made to aid

in selecting the stations and rotations from which samples were to be

collected for the total-nitrogen and organic-carbon study. Each experimental field was surveyed to determine the soil type or types, imiformity, degree of erosion, and any other factors which would influence

the selection of the plots for sampling.

At a given station, only those rotations were selected which were comparable as far as the above factors were concerned. An attempt was

made to include rotations which were uniform for all stations. This

was not always possible because of differences between stations in adaptable crops, and also because some rotations were so located as not to be

comparable with other rotations.

The following Ust shows the designations and locations of the 17

stations selected. Throughout this bulletin, in both text passages and

tables, the place name alone is generally used to designate the experimental stations.

Experimental station Location

United States Northern Great Plains Field Station Mandan, N. Dak.

Dickinson Substation Dickinson, N. Dak.

North Montana Branch Station Havre, Mont.

Central Montana Branch Station Moccasin, Mont.

Huntley Branch Station Huntley, Mont.

Newell Irrigation and Dryland Field Station NeweU, S. Dak.

Sheridan Substation Sheridan, Wyo.

^ The survey was conducted by Lyle T. Alexander, Chief, Soil Survey Laboratories,

Soil Conservation Service, Beltsville, Md., who visited all the dryland stations. He

was assisted by soU correlators from the Division of Soil Survev andf by a representative

from each of the State agricultural ejcperiment stations. The soil correlators were:

James Thorp, who assisted in Colorado, Nebraska, and Wyoming; E. H. Templin,

who assisted at the Great Plains stations; W. I. Watkins, who assisted in Kansas,

South Dakota, and North Dakota; B. H. WiUiams, who assisted in Montana; and

Willis J. Leighty, who assisted in the Northwestern States.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 3

Experimented station Location

Archer Substation Archer, Wyo.

North Platte Experiment Station North Platte, Nebr.

United States Akron Field Station Akron, Colo.

Colby Branch Station Colby, Kans.

Fort Hays Branch Station Hays, Kans.

Garden City Branch Station (main field and annex) Garden City, Kans.

United States Southern Great Plains Field Station Woodwfird, Okla.

United States Lawton Field Station Lawton, Okla.

United States Dalhart Field Station Dalhart, Tex.

United States Big Spring Field Station Big Spring, Tex.

A map showing the locations of the stations selected is presented

(fig. 1). Newell, S. Dak., and North Platte, Nebr., were not included in

the study of the effects of cropping on the total nitrogen and carbon

content of the soil, but were included in the soluble-nitrogen studies.

The year the sod was broken at each station, the year the experimental

plots were initiated, the soil series and texture, and the native vegetation

of the area are presented (table 1). It will be noted that the experimental

TABLE 1.—IdentificcUion of soils and native vegetation of 17 stations in the Great

Plains. The year in which the native sod was broken and experimental plots initiated is also given for each station

Location

Year

sod

broken

Year

QTpeñmental

plots

initiated

1913 1914

1906 1907

1916 1916

1907 1908

1911 1912

1907 1908

1916 1917

1912 1913

1896 1935

1907

1906

1903

1908

1914

1906

1907 1907

1930 1931

1914

1915

1907

1914

1916

1908

1906 1915

Soil series Soil texture Native vegetation

Mandan, N. Dak.

Dickinson,

N. Dak.

Havre, Mont.

Moccasin, Mont—

Huntley, Mont—

Newell, S. Dak...

Sheridan, Wyo

Archer, Wyo

North Platte,

Nebr.

Akron, Colo

Colby, Kans

Hays, £ans

Garden City,

Elans.

Garden City,

Kans., annex.

Woodward, Okla.

I-Awton, Okla

Dalhart, Tex

Big Spring, Tex..

Cheyenne—.

Morton

Joplin _.

Judith

Nunn I

Pierre

BridgeportAltvan

Holdrege—

Rago

Sherman

Munjor i

Keith, Ulysses, Colby,

—do

Pratt

Lawton

Dalhart,

Otero,

Mansker.

Amarillo

Fine sandy loam..

Loam

60 percent clay

loam, 30 percent

loam.

85 percent clay

loam, 15 percent

gravelly clay

loam.

Clay loam to silty

clay.

Clay

Loam to silt loamLoam

Very fine sandy

loam.

Silt loam

Do.

Silty clay loam,

silt loam.

Very fine sandy

loam.

.—doFine sandy loam..

Sût loam

Loam to fine

sandy loam.

Fine sandy loam..

Blue grama, needlegrass, and

threadgrass.

Blue grama, western wheatgrass,needlegrass, and threadgrass.

Short grasses.

Blue grama, Sandberg bluegrass,needlegrass, andthreadgrass.

Mostly short grasses.

Buffalograss, blue grama, and

western wheatgrass.

Buffalograss, blue grama,

western wheatgrass, needlegrass, and threadgrass.

Blue grama and western wheatgrass.

Buffalograss, blue grama, and

wefîtem wheatgrass.

Buflalograss and blue grama.

Do.

Do.

Do.

Do.

Tall grasses.

Do.

Short grasses.

Short grasses and mesquite.

' Tentative imcorrelated classification.
4 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

FIGURE l.--Map of the Great Plains region, showing the location of the stations

included in this study. The western boundary is indicated by the shaded line.

which is also the 5,000-foot contour.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 5

f)lot8 were initiated in the same year that the sod was broken or 1 year

ater at all stations except North Platte, Colby, Hays, and Big Spring.

Between the time the sod was broken and the e^merimental plots were

established at these stations, the land was uniformly cropped.

Qimate

Generally speaking, the Great Plains region is subject to wide fluctuations in precipitation, temperature, and wind velocity. Temperatures

over 100 F. are not uncommon and occur even in the northern portion.

Temperatures below 0° are not uncommon in the central and northern

portions, and lows of more than 50° below zero have been recorded at

some locations. Precipitation is generally limited, and long periods of

drought may occur. The heavier rains are often of the thunderstorm

type which fall rapidly and result in considerable nmoff from the more

sloping lands. Wind velocity is rather high at times; and this, together

with high temperatures during the summer months, promotes evaporation and reduces the effectiveness of the rainfall. Prevention oi soil

blowing is a frequent problem in certain areas; and during prolonged

periods of drought with sparse plant cover, duststorms reach destructive

proportions over a wide area.

Climatic and elevation data for each location are presented (table 2).

For the years covered by these data, annual precipitation ranged from

11.5 inches at Havre, Mont., to 28.7 inches at Lawton, Okla., with an

average of 17.9 inches. In the areas studied, approximately three-fourths

of the precipitation falls during the period April to Septeinber, inclusive.

TABLE 2.—Climatic and elevation data for 17 stations in the Great Plains

Location Years of

record

Precipitation

Annual Apr.-

Sept.

Evaporation i"

Apr.-

Sept.

Evaporation/precipitation

ratio«

Apr.-

Sept.

Temperature

Mean

annual

Elevation

Mandan, N. Dak...

Dicklnson, N. Dak..

Havre, Mont

Moccasin, Mont

Huntley, Mont

Newell, S. Dak

Sheridan, Wyo

Archer, Wyo

North Platte, Nebr.

Akron, Colo

Colby, Kans

Hays, Kans

Garden City, KansWoodward, Okla.

Lawton, Okla

Dalhart, Tex

Big Spring, Tex

1915-61

1907-47

1917-60

1909-61

1910-61

1908-52

1917-61

1913-51

1907-62

1908-61

1914-50

1907-51

1908-49

1915-48 1916-Í9

1906-50

1916-50

Inches

16.82

16.63

11.50

15.12

13.13

16.78

16.17

14.78

19.34

17.40

18.48

23.11

18.02

23.76

28.70

18.09

18.87

Inches

10.88

12.09

8.86

11.20

8.82

12.13

11.26

11.66

16.42

13.81

14.24

17.79

13.70

16.09

18.18

14.14

12.79

Inches

32.99

34.73

37.33

33.67

32.65

35.20

36.31

35.30

41.10

43.19

44.96

47.75

54.42

51.28

45.29

60.89

64.37

3.03

2.87

4.21

3.01

3.70

2.90

3.14

3.03

2.67

3.13

3.16

2.68

3.97

3.19

2.49

3.60

4.26

41.0

40.3

42.0

42.2

45.0

45.0

44.3

45.0

49.6

48.8

61.0

53.9

53.8

68.1

61.3

54.3

63.0

Average (all stations) 1911-50 17.86 13.12 41.79 3.24 49.3

Feet

1,760

2,543

2,505

4,228

3,018

2,880

3,790

6,012

3,026

4,660

3,145

2,000

2,836

1,900

1,111

4,000

2,396

3,046

1 Inches of evaporation from a free-water surface, using the standard Bureau of Plant Industry type

evaporation pan.

* Evaporation divided by precipitation for the period April through September.
6 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

As would be expected, there was a general increase in evaporation from

north to south. These values ranged from 32.7 inches at Huntley, Mont.,

to 54.4 inches at Garden City, Kans., with an average for all stations

of 41.8 inches*

The evaporation/precipitation ratio ranged from 2.49 at Lawton, Okla.,

to 4.25 at Big Spring, Tex., with an average of 3.24 for all stations.

Garden City, Kans., and Havre, Mont., also had high ratios, indicating

that the rainfall received at these stations may be less effective than at

the stations with lower ratios.

The average annual temperatures generally increased from north to

south, as expected, and ranged from 40.3° F. at Dickinson, N. Dak., to

63.0° at Big Spring, Tex. The average for all stations was 49.3°.

Elevation ranged from 1,111 feet at Lawton, Okla., to 6,012 feet at

Archer, Wyo., with an average for all stations of 3,046 feet. The region

as a whole slopes from west to east.

Collection and Preparation of Samples

Total Nitrogen and Carbon Study

Soil samples were collected at the time the rotations were estabhshed

at Sheridan, Wyo.; at Woodward, Okla.; and at the Garden City (Kans.)

annex. The rotation plots at Colby, Hays, and the Garden City (Kans.)

main field were sampled in 1916 after being cropped for several years.

These 1916 data (33) were used as the basis for determining the loss of

nitrogen at the three Kansas stations.

At each of the other stations, it was necessary to locate a virgin-sod

area representative of the site where the rotations were located. This

was done dm-ing the survey described (p. 2). The data from these virgin

areas were used to determine the loss of nitrogen or carbon that resulted

from cropping.

To use these data from the virgin areas, it was necessary to assume

that the nitrogen and carbon values obtained for the virgin sod in 1947

accurately represented the original condition of the rotation field; also,

that the original nitrogen and carbon contents of all the plots in the

field were the same. As such assumptions are subject to considerable

error, only large differences between values should be regarded as significant. Greater confidence can be placed in results that are similar

at a number of locations.

At Mandan, N. Dak., a high correlation was found between both the

nitrogen content and the carbon content of the virgin sod and the percentage by weight of particles less than 0.005 mm. in diameter. The percentage of particles less than 0.005 mm. in diameter in the soil from the rotation plots was also determined. By substituting these values in the

regression equation for virgin sod, the percentage of nitrogen or carbon

that was in the soil at the time the sod was broken was calculated for

each plot. A more complete description of this procedure is presented

later in this bulletin (p. 8).

A grid system was used on each virgin area to determine sampling

locations. Each grid was composed of 9 points—3 parallel rows of 3

Joints each. The points were spaced at 100- to 200-foot intervals,

epending upon the size of the area. A pit was dug in each virgin area to

study the characteristics of the profile. Soil samples were collected from

the grids at the time the survey was made in 1947. A 1-quart sample
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 7

was taken at each of the 9 points for each of the 0- to 6-inch and 6- to

12-inch depths. The selection of the samphng sites on the general farmlands in North Dakota was made in 1950.^ Only those sites were selected

which were near a virgin sod area of the same soil type. All sites were

located on Barnes, Morton, or WiUiams soils. Samples were taken from

the 0- to 6-inch, 6- to 12-inch, and 12- to 18-inch depths. Each depth

was a composite of several borings.

The rotation plots were sampled by or mider the direction of key personnel at each station.®

Samples for the present study were collected in 1947 except those from

Colby, Garden City, and Hays, Kans., which were collected in 1946 in

connection with a separate study conducted by the Kansas Agricultural

Experiment Station; and those from Mandan, N. Dak., which were

collected in 1943.

In most instances, a 1-quart sample of soil was collected from each

plot for each depth of 0 to 6 inches and 6 to 12 inches. It was sometimes

necessary to alter the depth of sampling to conform to previous samplings.

Each sample was a composite of several borings, usually 9 or more.

The soil samples were air-dried and shipped to the laboratory at Mandan, N. Dak., for analysis, with the exception of those from the 3 Kansas

stations and those from Mandan, N. Dak.; these were analyzed at Beltsville, Md. The soil samples were crushed and passed through a 2-mm.

screen; and all material that remained on the screen, such as rocks and

undecomposed organic matter, was discarded.

Soluble-Nitrogen Study

In 1949, 100 wheat plants were collected from manured and nonmanured rotations at 11 of the stations, to determine the effect of barnyard manure on the uptake of nitrogen by the plants. These samples

were shipped to Mandan, N. Dak., where they were oven-dried at 65 C.

and ground for analysis.

In 1950, approximately 5 pounds of soil was collected from the 0- to

6-inch depth on a number of rotations at 13 of the stations. These

samples were used for evaluating the effects of different levels of soil

5 The selecting of the sampling sites, as well as the coUecting of the samples, was

done by Dr. G. A. Johnsgard, formerly professor of soils. North Dakota Agricultural

College, Fargo, N. Dak.

• Tne authors are indebted to the personnel who collected soil and plant samples

from the rotation plots and suppUed information regarding the rotations. (Place

names are used instead of the füll designations of the respective stations; see list on

p. 2.) These personnel were: Leroy Moomaw (retired), former superintendent,

Dickinson, N. Dak.; V. C. Hubbard (deceased), former agronomist, M. A. Bell (deceased), former superintendent, and J. J. Sturm, superintendent, Havre, Mont.;

R. M. WiUiams (retired), former superintendent. Moccasin, Mont.; A. E. Seamans

(retired), agronomist, Huntley, Mont.; A. Osenbruff (retired), agronomist, NeweU,

S. Dak.; C. R. Hills, former acting superintendent, Sneridan, Wyo., and O. A. Beath,

head. Department of Agricultural Research Chemistry, University of Wyomiog,

Laramie, Wyo.; A. L. Nelson (retired), former superintendent, Archer, Wyo., and R.

D. Lewis, soil scientist, Laramie, Wyo.; L. L. Zook (retired), former superintendent,

and R. E. Ramig, soil scientist. North Platte, Nebr.; J. F. Brandon, superintendent,

Akron, Colo.; J. B. Kuska (retired), agronomist, Colby, Kans.; A. B. Erhart, former

agronomist, and P. L. Brown, soil scientist, Hays, Kans.; H. L. Stout, former agronomist, and W. L. Rock, soil scientist. Garden Cfity, Kans.; L. F. Locke, soil scientist.

Woodward, Okla.; W. M. Osbom (retired), former superintendent, Lawton, Okla.;

B. F. Barnes, former superintendent, and Grady L. Randel, former farm foreman,

Dalhart, Tex.; and F. E. Keating, superintendent. Big Spring, Tex.
8 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

nitrogen on the ability of the soils to produce nitrates, as determined by

incubation in a room at constant temperature. These soils were airdried immediately and shipped to Mandan, N. Dak., for incubation and

analysis. They were passed through a 2-mm. screen, and all material

that remained on the screen, such as rocks and imdecomposed organic

matter, was discarded.

Analytical Procedures

The total nitrogen content of the soil was determined by the Gunning

method (3) with a few modifications. The catalyst used in digestion was

10 parts K2SO4, 1 part FeS04 and 0.5 parts CuSO^. The NH3 was distilled into a 4-percent solution of boric acid, and titrated with N/7 H2SO4

or N/10 HCl. A mixture of bromcresol green and methyl red was used

as the indicator.

At first, carbon determinations were made by the dry-combustion

method, which included both the inorganic and organic carbon. It was

then necessary to determine the inorganic carbon and deduct this from

the total carbon value, to obtain the organic-carbon content. Later,

the wet-combustion procedure (35), which was more raj)id, was used to

estimate the organic-carbon content.

The incubation procedure for determining the quantity of nitratenitrogen produced by the soil for a given period of time was essentially

the same as that used by Allison and Sterling (2) with a few modifications.

The procedure used was as follows:

A cjuantity of sou, equivalent to 50 gm. oven-dried, was placed in 8-ounce jars*

This included 1 gm. of garden soU to assure the presence of nitrifying organisms*

To this was added 12.0 mg. of dipotassiumphosphate and 0.5 gm. of CaCOa. The

samples were kept in a room held at a constant temperature of 28° C. and moisture

was maintained m the soil at the moisture equivalent hy weekly additions of water.

The soil w^as shaken or stirred once a week to promote aeration. All the soils were

incubated for a 6-week period and a few for 12-, 18-, and 24-week periods. The

nitrate-nitrogen was determined hy the usual phenol-disulfonic acid procedure at the

beginning and again at the end of each period. The quantity of nitrate in the soil

at 0 weeks, as well as the quantity produced by 1 gm. of garden soil, was deducted

from the total quantity produced at the end of each period to obtain the quantity of

nitrates produced during each period.

The nitrogen content of the plant material was determined by a modification of the

procedure used for soil so as to include nitrate-nitrogen (3). JPhosphorus content of

the wheat plants was determined by the vanadomolybdate method.

The standard pipette procedure was used for mechanical analysis.

Relationship Between Soil Nitrogen and Particle Size

As mentioned previously (p. 6), a high correlation was obtained at

Mandan, N. Dak., between the nitrogen or carbon content of the virgin

sod and the percentage of particles less than 0.005 mm. in diameter.

The relationship for nitrogen is shown (fig. 2), The percentage of particles less than 0.005 mm. in diameter was then determined on each of

the rotation plots studied. By substituting these values in the regression

equation obtained jfrom the virgin sod, an estimate of the nitrogen

content prior to the time the sod was broken could be obtained for

each plot. It was assumed that the nitrogen content of the virgin sod

did not change appreciably during the 30-year period of study, and that

the quantity of less than 0.005-mm. material in the plots had not changed

during the period of cultivation.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 9

It was hoped that such a procedure could be used at the other stations

where original soil samples were not collected. However, poor correlations were obtained at many of the other stations, and the procedure

was used only at Mandan. Perhaps if more samples had been collected

from the virgin sod, the correlations would have become significant.

To obtain an overall estimate of the relationship between soil nitrogen

and particle size, the data from the virgin-sod areas at all of the stations

were groined together. A total of 118 samples were available. The

data are plotted (fig. 3), together with^the regression line. The data

Particles less than 0.005 mm. in diameter (percent)

FIGURE 2.—^Relationship of percentage of total nitrogen in virgin soil to the percentage

of particles less than 0.005 mm. in diameter at Mandan, N. Dak.

from the individual stations are identified by different symbols, and the

poor relationship between the 2 variables at some stations can be noted.

For example, at Dickinson and Hays, the points are widely scattered,

while at Moccasin, the correlation is negative. Although the data from

Sheridan are arranged in a linear group, the regression line for these data

would be nearly horizontal and the correlation coeflBcient nonsignificant.

The correlation coefficient for all samples was 0.617 which was much

higher than required to be significant at the 1-percent level. Although

the coefficient was highly significant, only 36 percent of the variation

in nitrogen content could be accounted for by differences in the content

of particles less than 0.005 mm. in diameter. It will be noted that in

general the relationship was much closer for coarser textured soils that

contained less than 30 percent of particles under 0.005 mm, in sizç.
o

oc

o

o

0.45 • MANDAN. NORTH DAK. o COLBY, KAN.

* DICKINSON, N. DAK. ô HAYS, KAN.

0.40

f HAVRE, MONT.

•-MOCCASIN, MONT.

<> L/WTON, OKLA.

-o-DALHART, TEX.

•# HUNTLEY, MONT. ^BIG SPRING, TEX.

0.35 SHERIDAN. WYO. ^= 118

ARCHER, WYO. J:= Ö.0472 +0.0043 Jr

0.30

0.25

-f AKRON, COLO. ^•0.617**

0.20

0.1 5

^

-<*'

^

X I

24 28 32 36

PARTICLES OF LESS THAN 0.005 MM. (PERCENT)

FIGURE 3.—Relationship of percentage of nitrogen to percentage of particles less than 0.005 mm. in diameter in the surface soil of virgin

sod at 13 locations m the Great Plains. (The 2 asterisks (**) indicate significant at 1-percent level.)

H

M

>

os

d

GO

Ö

o

>

o
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 11

This method of determining what the nitrogen content of cultivated

soils was prior to the time the sod was broken may have merit on certain

soils, but if it is used, a rather large number of samples should be collected.

Comparison of Nitrogen and Carbon Content of Virgin

and Cropped Soils

A comparison of the total nitrogen content of unmanured cropped and

virgin surface soils at 14 locations in the Great Plains is shown (table 3).

The average loss of total nitrogen in surface soils at the 14 locations over

a 36-year cropping period was 39 percent. This represents a 1.07-

percent loss of soil nitrogen for each year of crop production.

TABLE 3.—Total nitrogen changes in surface soils {0- to 6-inch depthy except as

indicated) at 14 locations in the Great Plains, as affected by 36 years of cropping

Location Cropping

period

Years of

cropping

Total nitrogen content

Virgin

soils!

Cropped

sous»

Change

with

cropping

Change

per year of

cropping

Mandan, N. Dak...

Dickinson, N. Dak.

Havre, Mont

Moccasin, Mont

Sheridan, Wyo

Archer, Wyo

Akron, Colo

Colby, Kans

Hays, Kans

Garden City, Kans..

Woodward. Okla.

Lawton, Okla

Dalhart, Tex

Big Spring, Tex—

19ia-43

1907-47

1916-47

1908-47

1917-47

1013-47

1908-47

1905-46

1903-46

1907-46

1914-47

1916-47

1908-47

1906-47

Number

30

40

31

39

Percent

0.160

.293

.151

.300

.159

.122

.134

.166

.220

.120

8.080

.154

.067

.060

Percent

0.116

.149

.090

.205

.121

.082

.086

.105

.122

.077

5.032

.074

.042

.041

Percent

-28

-49

-40

-32

-24

-33

-36

-36

-45

-62

-37

-32

Percent

-0.93

-1.23

-1.29

-.82

-.80

-.97

-.92

-.88

-1.06

-.92

-1.82

-1.68

-.95

-.78

Average. 36 .166 .096 -1.07

1 Except at Mandan, Sheridan, and Woodward, virgin areas closely comparable in soil characteristics to

each of the cropped-soil areas were sampled in 1947. At Mandan, the samplmg date was 1943. At Sheridan

and Woodward, virgin- and cropped-soil samples were taken from the same field; the virgin samples were

collected when the sod was originally broken in 1917 and 1914, respectively.

» Cropped soils sampled at the end of the cropping period. Values reported for cropped soils are averages

of all cropping treatments except those receiving manure.

» Values are for 0- to 12-inch depth.

Soil nitrogen losses due to cropping have varied among locations,

ranging from 60 percent at Woodward, Okla., to only 24 percent at

Sheridan, Wyo. These percentage loss values, however, are relatively

constant when compared with the wide range in nitrogen contents of

virgin and cropped soils imder investigation. For example, virgin soils

varied in total nitrogen content between 0.300 percent at Moccasin,

Mont., and 0.060 percent at Big Spring, Tex.; cropped soils varied

between 0.205 percent at Moccasin, Mont., and 0.032 percent at Woodward, Okla. Even though the total nitrogen content of virgin soils

showed a five-fold variation among locations, cropping and cultivating

have caused a relatively constant percentage reduction in nitrogen level.

Variations among locations in the nitrogen content of virgin sous, as

well as the degrees of change of this soil constituent because of cropping,

may be somewhat related to climate, soil, and other environmental factors.
12 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

In general, the nitrogen content ofthe coarse-textured soils was lower than

that of the silt loam, loam, and clay loam soils. Soils from the more

southerly locations were generally lower in total nitrogen in their virgin

state than from those locations in the north. These results were in

agreement with those of Jenny (24). While there were many notable

exceptions, the decline in soil nitrogen with cropping was most striking

at locations having the hi^est annual precipitation. The high rates of

loss at Havre, Mont., and Dickinson, N. Dak., however, were not explainable on this basis.

At 11 locations where the organic carbon contents of unmanured cultivated andjjvirgin soils|were investigated (table 4), the average loss per

year over a 37-year croppijig period was 1.15 percent. Results obtained

by Smith and coworkers (42) from the Texas Blacklands showed aa

average annual decline in organic matter of 1.50 percent in the plow layer.

At all locations, cropping caused a greater percentage reduction in organic

carbon than in nitrogen content. As an average of the 11 soils, 42 percent

of the organic carbon in virginfsoils was lost in 37 years of cropping. For

this same period and group of soils, 36 percent of the nitrogen was lost.

The relationship between the carbon and nitrogen contents of the

cultivated aod virgin soils and the changes in these relationships with

cropping are shown by the carbon/nitrogen (C/N) ratios (table 5). The

average C/N ratio of 7 virgin soils was 11.1; that of comparable cidtivated

soils was 10.1. Thus, the reduction in the C/N ratio of these soils after

37 years of cropping has averaged 1.0; this is approximately a 9-percent

reduction based on the average C/N ratio of the virgin soils. While the

magnitude of the change in the C/N ratio is not great, it would appear to

be a significant one in view of the similarity in trend for all of the 11 soils

under investigation.

TABLE 4.—Organic carbon changes in surface soils (0- to 6-inch devth) at 11 locations

in the Great Plains, as affected by 37 years of cropping

Location Cropping

period

Years of

cropping

Organic-carbon content

Virgin Cropped

Change

with

cropping

Change

per year o f

cropping

Mandan, N. Dak—_

Dickinson, N. Dak.

Havre, Mont

Moccasin, Mont

SheridaivWyo-.

Archer, W3^

Akron, Colo

Colby, Kans—

Hays, Kans..-

Garden City, Kans.,

Dalhart, Tex _

1913-43

1907-47

1916-47

190&-47

1917-47

1913-47

1908-47

1905-46

1903-46

1907-46

1908-47

Number

30

40

31

39

30

34

39

41

43

Percent

2.11

3.64

1.75

3.24

1.66

1.33

1.42

1.83

2.47

1.13

.72

Percent

1.45

1.51

.83

2.19

1.19

.78

.77

1.01

1.21

.69

.44

Percent

-31

-59

-53

-32

-28

-41

-46

-45

-61

-39

-39

Percent

-1.03

-1.48

-1.71

-.85

-1.21

-1.18

-1.10

-1.19

-1.00

-1.00

Average. 37 1.94 1.10 -42 -1.15

Cropping has also been associated with decline in carbon and

nitrogen fractions of subsurface layers of soil (table 6). The average

annual loss at 7 stations was 0.40 percent of nitrogen and 0.53 percent of

organic carbon. The average period of years of cropping at these 7 sta-
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 13

tions was 35. During this period an average of 15 percent of the nitrogen

was lost as well as 20 percent of the organic carbon. Here again, the

greater loss of carbon than nitrogen is evident even in the subsurface soils.

TABLE 5.—Carbon/nitrogen ratio of cropped and virgin surface soils (0- to S-inch

depth) at 11 locations in the Great Plains

Location Years of

cropping

Carbon/nitrogen ratio

Virgin

sous

Cropped

soils

Change

with

cropping

Mandan, N. Dak..

Dickinson, N. Dak.

Havre, Mont

Moccasin, Mont...

Sheridan/Wyo

Archer, Wyo

Akron, Colo

Colby, Kans

Hays, Elans

Garden City, Kans.

Dalhart, Tex

Average

Number

30

40

31

39

30

34

37

13.2

12.4

11.6

10.8

10.4

10.9

10.6

11.1

11.2

9.4

10.7

11.1

12.5

10.9

9.2

10.7

9.8

9.5

9.9

9.6

9.9

9.0

10.5

10.1

-0.7

-1.5

-2.4

-.1

-1.4

-.6

-1.5

-1.3

-.4

-.2

-1.0

TABLE 6.—Total nitrogen and organic-carbon changes in subsurface layers of soil

at 7 locations in the Great Plains, as affected by 35 years of cropping

TOTAL NITROGEN CONTENT

Station

Years of

cropping

Sou

depth

Virgin

sous ^ ^r' Change

with

cropping

Change

per year of

cropping

Mandan, N. Dak

Number

30

40

31

30

34

39

39

Inches

f 6-12

\ 12-24

6-12

6-12

7-20

6-12

6-12

6-12

Percent

0.119

.084

.163

.108

.117

.089

.087

.059

Percent

0.109

.080

.107

.090

.105

.084

.081

.050

Percent

-8

-6

-34

-17

-10

-6

-7

-15

Percent

-0.27

-.17

Dickinson, N. Dak . _ -.80

Havre, Mont -.56

ShOTJdan, Wyo . -.33

Archer. Wvo - - -.18

Akron, Colo -.18

Dalhart. Tex . -.38

Average 35 6-12 .104 .087 -15 -.40

ORGANIC-CARBON CONTENT

Mandan, N. Dak 30

40

31

30

34

39

39

f 6-12

\ 12-24

6-12

6-12

7-20

6-12

6-12

6-12

1.49

LOI

L87

.99

L21

.83

.79

.60

L36

.95

.98

.82

L07

.76

.65

.48

-6

-6

-48

-17

-12

-8

-18

-20

-0.20

-.20

Dickinson, N. Dak -L20

Harve, Mont -.55

Sheridan, Wyo -.40

Archer, Wyo -.24

Akron, Colo -.46

Dalhart. Tex .. -.51

Average 35 6-12 LIO .84 -20 -.53

To compare the results obtained from experimental stations with those

obtained imder general farm conditions, virgin and cropped soils from

farms in North Dakota were analyzed for nitrogen and carbon. These

farms were located on Barnes, Morton, and WilHams soils. A summary

of the results is presented (table 7).
TABLE 7.—Summary of average percentage of nitrogen and carbon and the carbon/nitrogen ratio for S soil series under virgin sod and cropped

land in North Dakota

Fields

Years

cropped

Depth

Nitrogen Carbon Carbon/nitrogen ratio

Soil Series

Virgin

land

Cropped

land

Virgin

land

Cropped

land

Change Virgin

land

Cropped

land

Change Virgin

land

Cropped Change

Barnes

Number

8

6

6

Number

7

7

7

Number

57

40

33

Inches

Í 0-6

\ 6-12

I 12-18

Í 0-^

\ 6-12

I 12-18

Í 0-6

\ 6-12

I 12-18

Percent

0.415

.210

.120

.242

.147

.114

.285

.146

.110

Percent

0.254

.130

.088

.186

.134

.102

.193

.115

.091

Percent

-39

-38

-27

-23

-9

-11

-32

-21

-17

Percent

4.97

2.22

1.12

2.88

1.54

1.17

3.35

1.42

1.02

Percent

2.77

1.12

.72

2.02

1.39

.99

1.99

1.00

.78

Percent

-44

-50

-36

-30

-10

-15

-41

-30

-24

12.0

10.6

9.3

11.9

10.5

10.3

11.8

9.7

9.3

10.9

8.6

8.2

10.9

10.4

9.7

10.3

8.7

8.6

-1.1

Morton _ _ _

—2.0

-1.1

-1.0

Williams

—. 1

-.6

-1.5

—1.0

-.7

Average, all soils 20 21 43

0-6

6-12

12-18

.324

.172

.115

.211

.126

.094

-35

-27

-18

3.86

1.77

1.11

2.26

1.17

.83

-41

-34

-25

11.9

10.3

9.7

10.7

9.3

8.8

-1.2

—1.0

-.9

Fi^
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 15

It will be noted that these results are somewhat in line with those obtained from the experimental stations. The average nitrogen loss for

all surface soils was 35 percent, and the average carbon loss 41 percent.

The carbon/nitrogen ratio for all surface soils was reduced 1.2 by cropping.

The higher nitrogen Barnes soils have been cropped for a longer period,

which would no doubt increase nitrogen losses; but there is evidence that

the soils with greater nitrogen content lost a higher percentage of their

nitrogen. Thus, cropping tends to decrease the variability in nitrogen

between soils. It is also apparent that comparatively high losses have

occurred in the subsurface soils.

These results, together with those from the experimental stations,

emphasize the fact that sizable losses of nitrogen and carbon occiu'red in

the Great Plains soils after they were placed under cultivation. This

verifies the findings mentioned in the literature (5, 9, 18, 21, 25, 31, 33,

34, 37, 47).

Rate of Decline in Soil Nitrogen with Years of Cropping

Earlier work by Gainey and coworkers (18), Sewell and Gainey (40),

and Myers and coworkers (33) at 3 Kansas stations, as well as periodic

sampling and analyses by Prof. O. A. Beath on the rotation plots at

Sheridan, Wyo., made it possible to show graphically the trend in the

nitrogen content of the soil over a period of years at these 4 locations.

The decline in nitrogen content of the soil with years of cropping at Hays,

Colby, and Garden City, Kans., and at Sheridan, Wyo., is presented

(fig. 4). At Garden City, 2 experimental fields were available.

The soil was not analyzed for nitrogen at the time the sod was broken

at Hays and Colby, Kans., and at the Garden City, Kans., main field;

therefore the nitrogen content of virgin-sod areas sampled in 1946 was

used for the beginning of the period. It was therefore assumed that the

nitrogen content of the sod had not changed from the time the sod was

broken until 1946, and that the virgin-sod area at each station was representative of the experimental plots.

Samples were collected from the Garden City annex and from the plots

at Sheridan at the time the sod was broken; the data at these 2 locations

were therefore complete. Each curve (fig. 4) represents an average of a

number of rotations at each station. Rotations to which barnyard

manure had been applied were excluded.

It is evident from thefgraph that at^the 3 Kansas stations, the nitrogen

content declined sharply during the first 10 to 20 years. After that, the

rate of decline decreased. This was particularly true of the 2 locations at

Garden City. At Sheridan,Jthe decline was almost a straight line with no

tendency to level off.

It will also be noted that, with increasing years of cropping at the 3

Kansas stations, the differences in nitrogen content of the sou between

locations become narrower. Near the end of the period, however, the

curves are nearly parallel.

The period covered by these curves is too short to provide any indication of future trends. The higher nitrogen soil could continue to lose

nitrogen at a greater rate than the lower-nitrogen soil, so that at some

time in the distant futiu*e the soils at these 3 Kansas locations would be

similar in nitrogen content. Or it is possible that the soils would reach

equilibrium levels with different nitrogen contents.

418061—57 2
16 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

Jenny (24) has discussed trends of soil nitrogen, and Woodruff (50) has

presented a formula for calculating the equilibrium level of a soil under a

given cropping treatment. In discussing the equilibrium concept, Jenny

states (p. 255} that ''nitrogen may reach a definite level or stationary

state that depends on the productivity variables, climate, plant, soil, and

'S»

c

sO)

o

0.22 -

0.T8

0.14

aio

1 - Hays, Kans.

2 - Sheridan, Wyo.

3 - Colby, Kans.

4 - Garden City, Kans.f annex

5-Garden City, Kans., main field

10 20 30 40.

Years of cropping

FIGURE 4.—Decline in nitrogen percentage^of the soil at Hays, Colby»JandJ^Garden

City, Kans., and Sheridan, Wyo.,^with years of cropping.

management." Thus, according to this statement, each of these soils

would eventually reach different equilibrium levels of nitrogen if the

same cropping systems were continued that had been used in the past.

Influence of Specific Cropping Practices on the Total

Nitrogen and Carbon Content^and the Carbon/Nitrogen Ratio of the Soil

Detailed data from each location are presented in appendix tables 29 to

44, inclusive. Several comparisons were made of the effects of different

crops or cropping practices on the nitrogen and^carbon^contentsof the

soil; these are discussed separately in the following sections.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 17

Eflfects of Small Grains

At a number of locations, several types of small grains were grown both

continuously and alternating with faUow. To determine whether there

was any difference in the loss of soil nitrogen and carbon under various

small grains, the percentage change in nitrogen and carbon was determined for each small grain. The average values of 2 continuously

cropped and 2 alternately cropped and fallowed plots were used for each

type of small grain. The nitrogen and carbon results are presented

(tables 8 and 9, respectively).

TABLE 8.—Effects of various types of small grains on percentage loss of nitrogen

in surface and subsurface soils under continuous and alternate cropving and

fallow, compared with virgin sod ^ at 9 locations in the Great Plains

SURFACE SOILS 2

Location

Years

of

cropping

Continuous cropping

Winter

wheat

Spring

wlieat Oats

Barley Spring

rye

Alternate fallow

Winter

wheat

Sprhig

wheat Oats Barley

Spring

rye

Mandan, N. Dak

Dickinson, N. Dak

Havre, Mont„- __.

Moccasin, Mont __.

Sheridan, Wyo

Archer, Wvo

Akron, Colo

Colby, Kans

Hays, Kans

Average of 4 locations.

Average of 7 locations.

Number

30

40

31

Percent

-27

-33

-27

-28

Percent

-20

-46

-42

-29

-21

-30

-31

-9

Percent

-20

-47

-32

-26

-20

-23

-26

-2

-10

Percent

-16

-41

Percent

Percent

-24

-22

-30

-25

-14

-7

-23

-41

-26

-3

Percent

-26

-49

-42

-35

-27

Percent

-28

-53

-39

-37

-25

-33

-33

-14

-8

Percent

-48

Percent

-28

-35

-30

-15

-8

-42

-37

35

-28 -22

-26

-18

-23

-23

-25

-26

-32 -31

SUBSURFACE SOILS»

Mandan, N. Dak

Dickinson, N. Dak

Havre, Mont

Sheridan, Wyo

Archer, Wyo

Akron, Colo

Average of 2 locations

Average of 5 locations

34

35

-9

-11

-10

+4

-28

-19

-1

+3

-2

+1

-6

0

-30

-11

+4

+6

+1

+5

-4

+3

-19

+3

-1

+3

+1

-2

-4

-2

-5

-37

-12

-9

-9

-13

-10

-41

-17

-14

-2

-13

-8

-16

-38

-16

-9

-8

-12

-16

-31

1 The plots at Colby and Hays were sampled in 1916, and these values were used for determining percentage of change for the period 1916-46. The land had been cropped for several years prior to 1916. AH other

values are based on virgin sod.

* The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches, and the subsurface

samples from 6 or 7 to 12 inches. At Sneridan, the subsurface samples were taken from a depth of 6% to

20 inches.

The results show that the losses of nitrogen or carbon were not consistently greater for any one type of small grain at all locations. The

extent of loss was influenced to a certain extent by the adaptabiHty and

production of each small grain at a given location. No doubt sou variability also affected the results at some of the stations. It is difficult to

determine from these results whether any one type of small grain influenced nitrogen and carbon losses more than any other type for the

region as a whole.
18 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

TABLE 9.—Effects of various types of small grains on percentage loss of carbon in

surface and subsurface soils under continuous and alternate cropping and fallow^

compared with virgin sodj^ at 6 locations in the Great Plains

SURFACE SOILS 3

Years

of

cropping

Continuous cropping Alternate faUow

Location Winter

wheat

Spring

wheat Oats Barley

Spring

rye

Winter

wheat

Spring

wheat Oats

Barley Spring

rye

Mandan, N. Dak

Number

30

31

30

34

30

30

Percent

"-4Ö'

-29

-37

-38

-19

Percent

-22

-60

-27

-32

-13

Percent

-24

-46

-25

-35

-3

-25

Percent

-18

-33"

-37

-20

-33

Percent

Percent

Percent

-28

-53

-36

-41

-23

Percent

-32

-53

-34

-43

-14

-18

Percent

-30

-37'

-46

-12

-27

Percent

Havre, Mont -49 -50

-28

-40

-40

-17

—55

Sheridan, Wyo

Archer, Wyo

Colby, Kans

Hays, KftTis

Average of 3 locations

Average of 4 locations-. _

31

31

-35 -24

-24

-21

-22

-30

-27

-36 -33

-32

-30

-31

-32

-31

SUBSURFACE SOILS a

Mandan, N. Dak . 30

31

34

Ó'

-13

+2

-16

+6

-2

-9

+1

+4 -6

-9

-12

-11

-20

-11

-8

"-ii' Havre, Mont ___ -16 -6

-11

-31

Archer, Wyo

Average of 2 locations 32 -6 -6 -4 -8 -10 -16

1 The plots at Colby and Hays were sampled in 1916, and the values obtained were used for determining

percentage of change for the period 1916-46. The land had been cropped for several years prior to 1916.

AH other values are based on virgin sod.

* The majority of the surface-sou samples were taken at depths from 0 to 6 or 7 inches, and the subsurface

samples from 6 or 7 to 12 inches. At Sheridan, the subsurfece samples were taken from a depth of 6% to 20

inches.

At several of the locations, the differences are probably within the

experimental error, while at others there may be a real difference. Myers

and coworkers (33), reporting on ¿he results from Hays and Colby, Kans.,

for a shorter period of time, stated that the several small grains had

essentially the same effect on the soil nitrogen. Their conclusions were

based on adjusted nitrogen values to compensate for soil variation.

Continuous Cropping Versus Fallow for Small Grains and Row

Crops

A comparison of the effects of small grains and row crops, grown continuously or alternating with fallow, on the nitrogen content of the soil

is shown (table 10), Loss of nitrogen from surface soils under small

grains was considerably less than under row crops* The same was true

for the subsurface soils at most of the locations. Loss of nitrogen from

the subsurface soils was considerably less than from the surface soils at

nearly all locations, as would be expected.

It will also be noted that the loss of nitrogen under small grains was

greater for the alternate-cropping and fallow treatment than, for continuous cropping at all stations except Big Spring. Moisture-equivalent

data from Big Spring indicate that soil from both the continuous and

alternate wheat and fallow plots was of finer texture than that from

virgin sod, and that soil from alternate fallow plots was of finer texture

than that from the continuous plots. It is possible that the original

nitrogen content of the wheat plots was higher than that of the virgin sod,
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 19

which would account in part for the small loss presented (table 10). It

is also possible that the original nitrogen content of the alternate fallow

plots wafc higher than that of the continuous plots; this would explain the

greater loss shown for continuous cropping than for alternate fallow.

TABLE 10.—Percentage change in nitrogen of surface and subsurface soils compared

with virgin sod,^ -under continuous and alternate cropping and fallow for small

grains and row crops at 14 locations in the Great Plains

Years

of

cropping

Surface soils > Subsurface soils >

Small grains Row crops Small grains Row crops

Location

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

fallow

Mandan, N. Dat

Number

30

40

31

39

30

34

39

30

30

30

33

31

39

41

Percent

-18

-44

-36

-27

-22

-26

-28

-9

-10

-11

Percent

-27

-60

-40

-36

-33

-34

-34

-26

-15

-13

Percent

-36

-59

-60

Percent

-40

-60

-63

Percent

+2

-25

-12

Percent

-8

-39

-16

Percent

-14

-49

-24

Percent

—18

Dickinson, N. Dak —44

Havre, Mont —32

Moccasin, Mont _ _ .

Sheridan, Wyo -35

-41

-48

-30

-33

-28

-55

-62

-36

-47

-35

-41

-56

-26

-38

-27

-64

-60

-40

-43

-4

0

+1

-16

-6

-11

-10

-12

-16

-13

Archer, Wyo _.__ —11

Akron, Colo . -20

Colby, KftTis

Hays, Kan s

Garden City, T^ans

Woodward, Okla __ _

Lawton, Okla . _ .- -47 -49 -17 -24 -23

-14

-10

-21

Dalhart, Tex —17

Big Spring, Tex -15 0 0 +8 —6

Average of 11 locations,. . 33

34

-24

-29

-29

-33

-43

-47

-43

Average of 8 locations -48 -7 -14 -20 -21

1 The plots at Colby, Hays, and Garden City were sampled in 1916, and these values were used for determining percentage of change for the period 1916-46. The land had been cropped for several years prior to

1916. All other values are based on virgin sod.

* The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The values for

Woodward are for the 0- to 12-inch depth. The majority of the subsurface samples were taken from 6 or 7

to 12 inches. At Sheridan, the depth was 6% to 20 inches.

The loss of nitrogen was greater under alternate row crop and fallow

than under continuous row crops at only 7 out of 13 stations. The

average loss of nitrogen from the surface soil for those locations where

data were available for all treatments in both depths was 29 percent for

continuous small grains, 33 percent for alternate small grains and fallow,

47 percent for continuous row crops, and 48 percent for alternate row

crops and fallow. For the subsurface soil, the losses were 7, 14, 20, and

21 percent, respectively.

The fact that small grains, especially those grown continuously, have

been much less destructive to soil nitrogen than row crops, verifies the

findings of previous investigators (i8, 24^ 33, and 39). The wheat at

most of the locations was generally harvested with a binder, and the

straw removed for the major portion of the period was reported.

A few of the stations began using combines in the early 1930'8, about

midway in the period. If combines had been used during the entire

period, perhaps the loss of nitrogen would have been even less under

wheat. Most of the row crops were harvested with a binder and the

entile crops removed? leaving httle crop residue on the land.
20 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

The greater loss of nitrogen from row-crop land than from small-grain

land was due to several factors. The amount of nitrogen removed by

row crops may have been greater than that removed by small grains,

which would account for part of the difference in loss. If cultivation

promotes loss of nitrogen by volatilization, a greater loss could be expected

under intertilled crops than under small grains. Leaching of the nitrogen

below the depth of sampling may have been greater under row crops, and

wind and water erosion may also have been more severe under these crops

at some locations.

The fact that alternate small grains and fallow may show a greater loss

of nitrogen than continuous small grains has been known for some time.

Thatcher (45) reported in 1912 that workers in Minnesota, North Dakota,

and Nebraska found a greater loss of nitrogen under fallow. He stated

that this was probably caused almost entirely by volatilization, inasmuch

as leaching would not account for the loss under dryland conditions.

Smith and Vandecaveye (41) reported on data obtained in Washington,

and Newton and coworkers (34) referred to residts obtained in Canada,

which showed higher losses under alternate small grains and fallow than

under continuous small grains.

Lyon (28), reporting on an investigation conducted at Cornell in

lysimeters, showed that soil which was kept bare for 10 years and cropped

for 5 years had an average annual loss of 25 pounds of nitrogen per acre;

this could not be accounted for by removal of crops and drainage water.

When the soil was cropped throughout the period, there was no loss that

could not be accounted for by removal in crops and drainage water. He

stated that the lack of vegetation is evidently a factor in increasing the

loss of nitrogen in gaseous form. He also stated that other factors may

contribute to the loss of nitrogen in gaseous form—tilling or stirring the

soil, high nitrogen content of the soil, application of large quantities of

nitrogenous manures, and possibly the application of lime to some soils,

Broadbent (7), working with certain soils in California, concluded that

part of the large losses of nitrogen from those soils is probably the result

of aerobic denitrification.

At Sheridan, Wyo., 1 plot had been continuously fallowed for 30 years;

that is, no crop had been grown, and the plot was cultivated to control

weeds. This plot had lost 43 percent of its nitrogen from the surface 7

inches of the soil during that period; this was a greater loss than had

occurred on any of the other cropping treatments. This plot, however,

was subject to considerable wind and water erosion, which would account

in part for the high loss of nitrogen.

Naturally, the less cover there is on a soil, the more subject that soil

is to wind and water erosion. Nimierous investigators have reported on

such losses (12, 13, 14, 23, 27, 32, 36, 38, 49). Although no actual

measurements were made, it is believed that in most instances the loss

of soil by wind or water erosion from the plots reported on in this study

was sKght and certainly would not be as great as from large fields. Volatilization may account for a portion of the greater loss of nitrogen from

fallowland, and it is possible that leaching of nitrogen to depths below

those which were sampled may also have been a factor. This nitrogen
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 21

would probably still be available to the plants in most years under dryland

conditions, but it could not be accounted for in the depths sampled in

this study.

The loss of nitrogen under alternate small grains and fallow may

appear to be only sHghtly greater than under continuous cropping; but

considering the fact that at most locations less crop is removed from

the land under a fallow system, the differences in nitrogen loss become

more significant. These differences emphasize the importance of factors

other than crop removal. The average amount of wheat removed per

plot at 8 locations under the alternate crop and fallow system was approximately 86 percent of that under continuous cropping. Where corn was

used, the amount of grain removed was approximately 62 percent.

A comparison of the effect of small grains and row crops, grown continuously or alternating with fallow, on the organic-carbon content of the

soil is presented (table 11). The situation for organic carbon was much

the same as for nitrogen, although the percentage loss of carbon was

greater than for nitrogen with a few exceptions in the subsurface soil.

TABLE 11.—Percentage change in organic carbon of surface and svbsurface soils

compared with virgin sodj^ vnder continuoiLS and alternate cropping and fallow

for small grains arid row crops at 7 locations in the Great Plains

Years

of cropping

Surface soils » Subsurface soils a

Location

Small grains Row crops Small grains Row crops

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

faUow

Continuous

cropping

Alternate

fallow

Mandan, N. Dak

Number

30

31

30

34

30

30

30

Percent

-22

-46

-28

-35

-21

-25

-32

Percent

-28

-53

-34

-43

-28

-28

-25

Percent

-38

-62

-41

-52

-40

-42

-46

Percent

-44

-65

-44

-52

-44

-52

-40

Percent

+2

-10

Percent

-6

-17

Percent

-18

-27

Percent

—19

Havre, Mont -34

Sheridan, Wyo _ _ _

Archer, Wyo _ -2 -11 -19 -19

fîolby, KftTis

TTays, TTftTis

Gftfílén (^Aty, Karis.

Average of 3 locations

Average of all 7 locations32

32

-34

-30

-41

-34

-51

-46

-54

-49

-3 -11 -21 -24

1 The plots at Colby, Hays, and Garden City were sampled in 1916, and these values were used for determining percentage change for the period 1916-46. The land had been cropped for several years prior to

1916. All other values are based on virgin sod.

> The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The majority of

subsurface-soil samples were taken from 6 or 7 to 12 tuches. \ At Sheridan, the depth was 6% to 20 Incnes.

The carbon/nitrogen ratios of surface and subsurface soils under continuous and alternate cropping and fallow for small grains and row crops,

at the beginning and at the end of the cropping period, are presented

(table 12). The greater loss of carbon than of nitrogen is apparent in

the carbon/nitrogen ratios. During the period, all ratios were reduced

in the surface sou, and most of them in the subsurface soil. There was

less reduction in the lower depth than in the upper. The greatest reduction occurred under row crops alternating with fallow.
22 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

TABLE 12.—Carhon!nitrogen ratios of surface and subsurface soils under continuous

and alternate cropping and fallow for small grains and row crovs^ at the beginning ^

and at the end of the cropping period^ at 7 locations in the Great Plains

SURFACE SOILS r

Years

of

cropping

Small grains Row crops

Location

Continuous

cropping

Alternate

fallow

Continuous

cropping

Alternate

fallow

Beginning

End BeginningEnd Beginning

End Beginning

End

Mandan N Dak

Number

30

31

30

34

30

30

30

13.1

11.6

10.3

10.9

11.4

11.7

11.9

12.6

9.6

9.5

9.7

9.8

9.8

9.0

13.1

11.6

10.0

10.9

10.7

11.7

10.9

12.6

9.1

9.9

9.4

10.3

10.0

9.4

13.2

11.6

10.3

10.9

11.6

11.8

11.1

12.6

8.8

9.3

8.9

9.8

10.2

8.3

13.2

11.6

10.4

10.9

11.0

12.6

11.0

12.3

2avr6 Mont - - 8.7

Sheridan, Wyo 9.0

Archer, Wyo

Colby, Kans

8.9

8.2

Havs T^fln.^ 9.8

Graden Citv. Kans 9.0

Averaee 31 11.6 10.0 11.3 10.1 11.6 9.7 11.5 9.4

SUBSURFACE SOIL S3

Mandan. N. Dak - _ - 30

31

34

12.6

9.2

9.3

12.6

9.4

9.1

12.6

9.2

9.3

12.6

9.0

8.8

12.6

9.2

9.3

12.0

8.8

8.6

12.4

9.2

9.3

12.2

Harve, Mont 8.8

Archer, Wyo 8.6

Average - - 32 10.4 10.3 10.3 10.1 10.4 9.8 10.3 9.8

1 Carbon/nitrogen ratios for Mandan, Havre, and Archer for the beginning of the period are based on

samples collected from virgin sod at end of the period and are assumed to be the same as at the beginning

of the period.

» The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 üiches. The majority of

the subsurface samples were taken from 6 or 7 to 12 inches. At Sheridan, the depth was 6% to 20 Inches.

Barnyard Manure Versus No Manure

The effect of barnyard manure in a rotation on the loss of nitrogen and

organic carbon from the soil, as compared with a similar rotation without

manure, is presented (table 13).

The rotations were 2-, 3-, or 4-year rotations. Manure was appUed

to 1 plot in a rotation each year. That is, a given plot in a 2-year rotation

would receive manure every 2 years; in a 3-year rotation, a given plot

would receive manure every 3 years; and so on. The average annual rate

of appUcation for a given plot ranged from approximately 2^ to 5 tons

of barnyard manure per acre. This amounted to approximately 25 to

50 pounds of nitrogen per acre annually.

The data presented show that the appUcation of manure reduced the

loss of nitrogen and carbon at all locations and in both depths. At some

locations the benefit from manure was only sUght, while at others it was

considerable. Both nitrogen and carbon data were available for both

treatments and depths at only 5 of the 12 locations. The mean loss of

nitrogen from the surface soils at these 5 locations was 33 percent from

the rotation without manure and 14 percent from the rotation with

manvire. For the subsurface soils, the values were 14 and 7 percent,

respectively. The average loss of organic carbon at those same 5 stations

was 39 percent from the rotation without manure and 19 percent from

the rotation with manure for the surface soils. For the subsurface soils,

the values were 15 and 8 percent, respectively. Although the loss of
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 23

nitrogen from the manured rotations has been approximately one-half

that of the rotations without manure, total crop removal from the former

has been only 11 percent greater.

TABLE 13.—Percentage change in nitrogen and organic carbon of surface and svbsurface soilsy'^ compared with virgin sodj^ in rotations with and without manure

at 12 locations in the Great Plains

Years

of

cropping'

Total nitrogen Organic carbon

Location

Surface soils Subsurface soils Surface soils Subsurface soils

Without

manure

With

manure

Without

manure

With

manure

Without

manure

With

manure

Without

manure

With

manure

Mandan, N. Dak

Number

30

40

31

39

30

34

39

30

30

33

31

39

Percent

-31

-49

-43

-32

-26

-34

-38

-24

-32

-63

-52

-31

Percent

-4

-39

-32

-21

+6

-19

-22

-16

-29

-60

-48

-22

Percera

-13

-30

-20

Percera

+7

-10

-18

Percera

-35

Percera

-9

Percent

-12

Percera

+7

Dickinson, N. Dak

Havre, Mont -. -63 -43 -21 —17

Mocftfwin, Mont

Sheridan,'Wyo - -9

-6

-8

-10

+2

+3

-30

-41

+8

-27

-10

-6

-8

Archer, Wyo -2

Akron, Colo

Colby, Kans -30

-37

-26

Hays, Kans -33

Woodard, Okla

Lawton, Okla -20

-20

-19

Dftlhftit, Tftx _ _ -17 -38 -26 -26 -18

Average of all 12 locationsAverage of 5 locations

Average of 8 locations

34

33

34

-37

-33

-38

-25

-14

-22

-14

-16

-7

-8

-39 -19 -16 -8

1 The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The values at

Woodward are for the 0- to 12-lnch depth. The majority of the subsurface samples were taken at depths

from 6 or 7 to 12 inches. At Sheridan, the depth was 6?» to 20 inches.

> The plots at Colby and Hays were sampled in 1916, and these values were used for determining percentage change for the period 1916-46. The land had been cropped for several years prior to 1916. All

other values are based on virgin sod.

* The cropping period began with the year the land was broken except at the Kansas stations. Manure

was applied during the entire cropping period shown at all stations, except Akron where it was applied 23

years, "W oodward where it was applied Û& years, Lawton where it was applied 28 years, and Dalh¿rt where

It was applied 33 years.

Sheridan was the only station where the manure increased the nitrogen

and carbon contents of the surface soil above the increase for virgin sod.

At Mandan, there was only a sUght reduction in these elements where

manure was appUed. The nitrogen content of the subsurface soil was

increased sUghtly at 3 of the locations where manure was applied. Brage

and coworkers (6) pointed out that numerous investigators reported

difficulty in increasing the nitrogen or carbon content of the soil by

appUcations of barnyard manure. In the study in Minnesota, however,

they showed that where manure had been appUed to a 4-year rotation

over a period of 30 years at different rates, the nitrogen content of the

soil was progressively higher than the check treatment with each additional

increment of manure appUed.

The quantity of nitrogen in the manure should have been sufficient to

meet the needs of the crops. It is therefore apparent that considerable

nitrogen has been lost by means other than crop removal. As mentioned

earher, Lyon {28) stated that the appUcation of large quantities of

maniu-e may contribute to losses of nitrogen in the gaseous form. The

rates of application were not excessive, but these amounts on soils that

had been broken from sod for a relatively short time may have been
24 TECHNICAL BULLETIN 1164, U. S. DEFT. OP AGRICULTURE

sufficient for volatilization to occur. Russell (3Ö, pp. 299-300) states

that where much organic matter occurs, as in soils heavily manured or

in certain virgin soils, it is difficult to account for the lost nitrogen. It

was assumed that part of the nitrogen was lost as gas during oxidation of

organic matter.

It is possible that volatilization may have accoimted for some loss of

nitrogen from manured land. Leaching from the depth of sampling may

also have been a factor; butinasmuch as Uttle of the nitrogen at this level

would have been lost from the root zone, most of it was still available for

plant use. Wind and water erosion may account for nitrogen losses in

some instances.

The carbon/nitrogen ratios at the beginning and at the end of the

cropping periods, for soils in rotations with and with out manure, are

presented (table 14). In the surface soils, the ratios were reduced at

every location in both treatments. In the subsurface soils, the ratios

were reduced at some locations and increased at others. The average

ratio of the surface soils for 5 of the locations was reduced approximately

1.0 by cropping, whereas the average ratio for the subsurface soils was

only reduced approximately 0.1 or 0.2. The carbon/nitrogen ratio at

the end of the period was usually only sHghtly higher under the manured

rotation than under the rotation without manure.

TABLE 14.—Carhon/nitrogen ratios of surface and subsurface soilsy at the beginning ^

and at the end of the cropping period^ for rotations with and without manure,

at 7 locations in the Great Plains

Years

of

cropping

Surface soils ' Subsurface soils >

Location Withoutmanure With manure Withoutmanure With manure

Beginning

End BeginnlngEnd Beginning

End Beginning

End

Mandan, N. Dak _

Number

30

31

30

34

30

30

39

13.1

11.6

10.4

10.9

10.1

10.6

10.9

12.4

9.6

9.9

9.7

9.3

9.8

9.9

13.2

11.6

10.5

10.9

10.6

10.7

10.9

12.6

9.8

10.7

9.8

9.4

10.1

10.4

12.5

9.2

10.3

9.3

12.6

9.1

10.3

9.2

12.5

9.2

10.2

9.3

12.6

Havre, Mont 9.2

Sheridan, Wyo 10.4

Archer, wyo 8.0

Colby, Kans

Havs. Kans

Dalhart, Tex 10.2 9.6 10.2 10.0

Average of all 7 locationsAveraee of 5

32

33

11.1

11.4

10.1

10.3

11.2

11.4

10.4

10.6 iÖ.3 10.1 10.3 10.2

1 Carbon/nitrogen ratios for Mandan, Havre, Archer, and Dalhart for the beginning of the period are

based on samples collected from virgin sod at the end of the period and are assumed to be the same as at the

beginning of the period.

2 The majority of the surface soil samples were taken at depths from 0 to 6 or 7 inches. The majority of the

subsurface samples were taien from 6 or 7 to 12 inches. At Sheridan, the depth was 6^ to 20 inches.

Effects of Green-Manure Crops on Soil Nitrogen and Carbon

The percentage change in nitrogen and carbon content of the surface

and subsurface soils, in rotations with and without green manure, is

presented (tables 15 and 16, respectively). The carbon/nitrogen ratios

at the beginning and at the end of the period are presented (table 17).

In these investigations, 2-, 3-, or 4-year rotations were used, the 4-year

rotation being predominant. The legumes used were sweetclover,

cowpeas, or field peas; these were usually plowed in spring or early

sunmier and fallowed the remainder of the season.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 25

TABLE 15.—Percentage change in nitrogen of surface and subsurface soils compared

with virgin sody^ in rotations with and without green manure^ ai 13 locations in

the Great Plains

Years of

cropping»

Surface soils s Subsurface soils »

Location

No green

manure

Rye,

green

manure

Legume,

green

manure

No green

manure

Rye,

green

manure

Legume,

green

manure

Mi^ndftn, N, Dak

Number

30

40

31

39

30

34

39

30

30

30

15

33

31

Percent

-31

-50

-37

-32

-21

-34

-37

-28

-18

-18

-25

-62

-48

Percent

-32

-48

<-36

Percent

-30

-50

Percent

-13

-37

-15

Percent

-13

-31

<-6

Percent

-8

Dickinson, N. Dak -35

Havre, Mont

Moccasin. Mont -32

-19

-33

-33

-30

-17

SherldftTi, Wyo -18

-30

-37

-27

-14

-22

-25

-10

-6

-8

-6

-4

-8

-7

Archer, Wyo ___ -6

Akron, Oolo -3

fJolhy, ITftTis _ __

TTavsVlTans

Garden f^ity, T^aTis

Garden City, Kans., Annex _ _.

Woodward, Okla

-24

-61

T^iwton, O^la. -47 -12 -16

Average of 8 locations

Average of 6 locations

31

35

-30

-35

-29

-33

-30

-33 -15 -12 -12

1 The plots at Colby, Hays, and Garden City, Kans., were sampled in 1916, and these values were used

for determining percentage change for the period 1916-46. The land had been cropped for several years

prior to 1916. All other values are based on virgin sod.

« The green manure rotations were in effect for the entire cropping period at all stations except Woodward where they were in effect for 29 years, and Lawton where they were in effect for 28 years.

« The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The values at

Woodward are for the 0- to 12-mch depth. The majority of the subsurface samples were taken from 6 or

7 to 12 inches. At Sheridan, the depth was 6% to 20 inches.

* For the first 20 years, the area occupied by this rotation was in a rotation in which peas were plowed

under for green manure.

TABLE 16.—Percentage change in organic carbon in surface and subsurface soils

compared with virgin sodj^ in rotations with and without green manure^ at 8 locations

in the Great Plains

Years of

cropping

Surface soils » Subsurface soils »

Location

No green

manure

Rye,

green

manure

Legume,

green

manure

No green

manure

Rye,

green

manure

Legume,

green

manure

Mandan, N. Dak

Number

30

31

30

34

30

30

30

15

Percent

-33

-50

-24

-41

-37

-30

-32

-31

Percent

-36

-51

-22

-40

-34

-29

-35

-30

Percent

-33

Percent

-11

-16

-9

-6

Percent

-14

-12

-7

-8

Percent

-10

Havre, Mont

Sheridan, Wyo - - - - -26

-40

-43

-29

-9

Archer, Wyol „ -7

Colby, Kans

Hays, Kans _ _ _

Garden Oitv. Kans

(Jarden City, Kans., Annex -35

Average of 6 locations

Average of 3 locations—

28

31

-33

-33

-32

-33

-34

-33 -9 -10 -9

Í The plots at Colby, Hays, and Garden City, Kans., were sampled in 1916, and these values were used

for determining percentage change for the period 1916-46. The land had been cropped for several years

prior to 1916. All other values are based on virgin sod.

* The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The majority of

the subsurface samples were taken from 6 or 7 to 12 inches. At Sheridan, the depth was 6^ to 20 inches.

The data show that neither rye with green manure nor legume with

g'een manure were eflE^ective in reducing the losses of nitrogen and carbon,

arbon/nitrogen ratios in the green-manure rotations were approximately
26 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

the same as in rotations without green manure. At Sheridan, Wyo.

(see appendix table 34), 1 plot had been grown continuously to peas for

a 30-year period. All the crop was plowed under for green manure each

year. The soil from this plot lost 28 percent of its nitrogen, which was

as high as from row-crop and small-grain rotations where the crops had

been removed. Wind and water erosion, however, was a problem on this

plot, which probably would account for some of the loss.

TABLE 17.—Carbon/nitrogen ratios of surface and subsurface soils^ at the beginning ^

and at the end of the cropping period, for rotations with and without green manure

at 8 locations in the Great Plains

Years

of

cropping

Surface soils » Subsurface soils >

Location

No green

manure

Rye, green

manure

Legume,

green manure

No green

manure

Rye, green

manure

Legume,

green manure

Beginning

End Beginning

End Beginning

End BeginningEnd Beginning

End Beginning

End

Mandan, N. Dak..

Havre, Mont

Number

30

31

30

34

30

30

30

16

13.1

11.6

10.3

10.9

11.3

10.8

11.6

9.9

12.6

9.3

9.9

9.7

9.8

9.2

9.8

9.1

13.2

11.6

10.6

10.9

10.7

11.9

11.1

10.1

12.4

8.9

10.1

9.4

9.8

9.8

9.2

9.4

13.1 12.6 12.5

9.1

10.0

9.3

12.9

8.7

10.1

9.2

12.6

9.1

10.0

9.3

12.6

8.6

9.9

8.9

12.6 12.3

Sheridan, Wyo

Archer, Wyo

Oolby, Kans

Hays, Kans

Garden City,

Kans

10.3

10.9

11.6

11.3

9.4

9.8

9.3

9.6

10.1

9.3

9.9

9.2

(harden City,

Kans., Annex 10.3 8.9

Average of 6

locations 28

31

11.0

11.4

10.0

10.7

11.2

11.6

10.2

10.6

11.2

11.4

9.9

10.6

Average of 3

locations 10.6 10.7 10.6 10.4 10.7 10.6

1 Carbon/nitrogen ratios for Mandan, Havre, and Archer for the beginning of the period are based on

samples collected fix)m virgin sod at the end of the period, and are assumed to be the same as at the beginning

of the period.

» The majority of the surface soil samples were taken at depths from 0 to 6 or 7 inches. The majority of the

subsurface samples were taken from 6 or 7 to 12 inches. At Sheridan, the depth was 6% to 20 inches.

These results are, in general, contrary to those obtained in more humid

regions. Tidmore and Volk (46)^ working in Alabama, reported that at

the end of a 9-year period, soils on which legumes were plowed under

contained about 30 percent more nitrogen than soils that received no

legumes. The nitrogen content of the nontreated plot was 0.035 percent.

Jones {26)^ also working with soils in Alabama, found that growing

vetch on the Hartsells and Decatur soils resulted, respectively, in net

annual gains of 66 pounds and 52 pomids of nitrogen per acre. When

vetch was grown following fall-turned soybeans, the annual net gain in

nitrogen amounted to 43 pounds on Norfolk, 66 pounds on Hartsellc, and

104 pounds on Decatur soil. The nitrogen content of these soils was

0.019, 0.039, and 0.078 percent, respectively. Chapman and Liebig (JO),

working in California with purple vetch and annual yellow sweetclover

in lysimeters, reported that over a 10-year period there had been a net

unaccounted-for gain of over 100 pounds of nitrogen per acre where

these legumes had been plowed under as green manure.

Greaves and Jones (20), working with legumes grown in jars over a

16-year period in Utah, found that where the legimie was removed, no
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 27

gains in soil nitrogen were obtained; but if the legume crop was plowed

under, appreciable gains resulted.

Greaves and Bracken (19) reported results from Nephi, Utah, which

showed that peas in rotation witn wheat tended to maintain the nitrogen

content of the soil over a 25-year period.

Lyon and Wilson (29), working at the Agricultural Experiment Station

of Cornell University, found that where various legmnes and oonlegumes

were plowed under each year over an 11-year period, the vetch plots lost

42 pounds of nitrogen per acre; the rye plots, 217 pounds per acre; the

plots planted to peas, 380 pounds per acre; the oats plots, 382 pounds per

acre; and the buckwheat plots, 412 pounds per acre. This would indicate

that rye was more effective than peas in reducing nitrogen losses.

The question may logically be raised as to why results from the Great

Plains are contrary to those from other regions. There are several

possible reasons for this discrepancy: (1) Moisture is generally limited

in the Great Plains, and nitrogen may not be fixed by the symbiotic

organisms as readily under this condition. Satisfactory stands of greenmanure crops are not always obtained; this is especially true of sweetclover. Furthermore, the growth and development of the root system

may be restricted under dryland conditions which might influence the

fixation of nitrogen. (2) Inasmuch as these soils have been broken from

sod for a comparatively short time, it is possible that the organisms may

be able to obtain their nitrogen requirements from the soil and do not need

to fix nitrogen from the air. (3) Nitrogen that has been fixed by the

organisms may have been leached below the depth of sampling. (4)

Nitrogen may have been fixed by the organisms, but lost by volatihzation

during the fallow period following the plowing under of the green manure.

(5) Nitrogen may have been fixed, but the crops removed following the

green-manure rotation may have coatained a higher percentage of nitrogen. In general, green manure has not increased the yield of crops which

follow, but the total pounds of nitrogen per acre removed in the crops may

have beea greater.

The results obtained in this study indicate that green manures have

been of Httle or no value in reducing the loss of nitrogen under dryland

conditions in the Great Plains. These results also suggest the need for

further study of this problem to determine why greater benefit has not

been received from the use of green-manure crops.

Effects of Grass and Alfalfa on Nitrogen and Carbon Changes

The percentage change in the nitrogen and carbon content of the

surface and subsurface soils of rotations with or without grass or alfaKa

are presented (table 18). The corresponding carbon/nitrogen ratios

are also presented (table 19).

The grass or alfalfa rotations contained 6 plots each. Of these plots, 3

were in grass or alfalfa, aad 3 were in a rotation of com, wheat, oats.

Un il 1937, 1 plot of grass or alfalfa was broken each year, and 1 of the

annual crop plots was seeded to grass or aKalfa each year. The annual

crop rotation was moved 1 plot each year, to include the plot that had been

broken from sod. By this system, a specified plot was in grass or alfaKa

for 3 years.
28 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICXJLTUBE

In 1937, the rotations at some ofthe stations were changed to a deterred

type in which a sod plot was plowed every 4 years. Thus, the grass or

alfaKa remained on a given plot for 12 years.

The rotation without grass or alfalfa was a 3-year rotation of com,

wheat, oats. The crops were harvested and removed from the land in

each rotation.

TABLE 18.—Percentage change in nitrogen and organic carbon in surface and subsurface soils compared with t irgin sod, in rotaHons with and without grass or alfalfa^

at 4 locations in the Great Plains

NITROGEN

Surface soils 1 Subsurface soils i

Location

Years of

cropping

Rotation

without

grass or

alfalfa

Grass

and

graincrop

rotation

Alfalfa

and

graincrop

rotation

Rotation

without

grass or

alfalfa

Grass

and

graincrop

rotation

AlfaKa

and

graincrop

rotation

Mandan, N. Dak„^

Number

30

40

30

34

Percent

-31

-49

-27

-34

Percent

-25

Percent

-18

-44

-18

-35

Percent

-13

-30

-10

-6

Percent

-6

Percent

+3

Dickinson, Nt Dak, -31

Phfirlflan^ Wyo . -13

-30

-8

-3

-5

Arclifir, Wyo" -9

Average of 3 locations 31 -31 -23 -24 -10 -6 -4

ORGANIC CARBON

Mandan, N. Dak 30

30

34

-36

-31

-41

-29

-20

-38

-24

-26

-44

-13

-10

-6

-8 +3

Sheridan, Wyo

Ajcher, Wyo -4 -8

Average of 2 locations 32 -38 -34 -34 -10 -6 -2

1 The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The majority

of the subsurface samples were taken from 6 or 7 to 12 inches. At Sheridan the depth was 6^ to 20 inches.

The data presented indicate that the grass or alfalfa rotations reduced

the loss of nitrogen and carbon at Mandan and Sheridan but had Httle

effect at the other stations. At Sheridan and Archer, there was less

loss of nitrogen from the gross rotation than from the alfalfa rotation.

This is difl&cult to explain unless it is because the amount of nitrogen

removed by crops in the aKalfa rotation was considerably greater than

in the grass rotations. At Mandan, the aKalfa rotation was more effective in reducing the loss of nitrogen than was the grass rotation, and

the total amount of crop removed was greater. The nitrogen content

of the crops was not determined, but it is assumed that the amount of

nitrogen removed in the crops would have been greater in the alfalfa

rotation. It would appear, then, that the alfaKa is adding nitrogen to

the soil at Mandan, but not in sufl&cient quantities to maintain the soil

at its original level.

The greater loss of carbon than of nitrogen is reflected in the decrease

in the carbon/nitrogen ratio from the beginning to the end of the cropping

period in the surface soils. The ratios at the end of the period for the

grass and aKalfa rotations were approximately the same as for the rotation without these crops. Cropping had httle effect on the C/N ratio

in the subsurface soils, but the ratio was shghtly higher in the aKaKa

rotation than in the others at the end of the period.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 29

TABLE 19.—Carhonjnitrogen ratios of surf ace and subsurface soilst at the beginning ^

and at the end of the cropping periodj for rotations with and without gra^s or alfalfa,

at S locations in the Great Plains

SURFACE SOILS «

Location Years of

cropping

Rotation without

grass or alfalfa

Grass- and graincrop rotationAlfalfa and graincrop rotation

Begin,

nlng

End Beginning

End Beginning

End

MftTifii^Ti, N. Dak:

Number

30

30

34

13.1

10.6

10.9

12.3

9.9

9.7

13.2

10.8

10.9

12.6

9.9

9.6

13.2

10.6

10.9

12.3

Sheridan, Wyo . _ 9 6

Archer, Wyol 9.6

Average of all 3 locations- 31 11.6 10.6 11.6 10.7 n.6 10.4

SUBSURFACE SOILS «

30

30

34

12.6

10.4

9.3

12.6

10.4

9.2

12.6

"9.T

12.3

10.0

9.3

12.6 12.6 SherldíiTÍ, Wyo 10.0 Àrfihftr, Wyrr __ . _ _ 9.3 9.4

Average of 2 locations 32 10.9 10.8 10.9 10.8 10.9 11.0

Í Carbon/nitrogen ratios for Mandan and Archer for the beginning of the period are based on samples

collected from virgin sod at the end of the period and are assumed to be the same as at the beghmlng of the

period.

» The majority of the surface-soil samples were taken at depths from 0 to 6 or 7 inches. The majority

of the subsurface samples were taken from 6 or 7 to 12 inches. At Sheridan, the depth was 6% to 20 inches.

The number of locations having grass or alfalfa rotations was so

limited, and the results so variable, that it is diflScult to draw definite

conclusions.

It is apparent, however, that neither grass nor alfalfa grown in rotation

with annual crops was able to maintain the nitrogen or carbon content

of the soil at the same level as virgin sod. In fact, the losses from these

rotations were substantially the same as from plots continually cropped

to small grains. (Compare table 18 with table 10.) Grass grown

continuously on the same soil would be expected to maintain the nitrogen

at a level approximately equal to that at the time the grass was seeded;

but where annual grain crops are rotated with the grass, a decline in

nitrogen would be expected. McHenry and coworkers (30), working

at North Platte, Nebr., with grass stands ranging in age from 1 to 9

years, found that losses of nitrogen occurred in aU plots except one.

Those plots which had been in grass more than 6 years out of the 9 contained significantly more nitrogen than those which had been in continuous cultivation, although they had actually lost some of their original

nitrogen.

Results at Mandan, N. Dak./ showed that the nitrogen content of

the surface 6 inches of soil, which had been in grass for 6 years, was

approximately the same as at the time it was seeded to grass. Land

wmch had been cropped to com and wheat during that period lost 6

percent of its nitrogen.

Thus, since annual crops were rotated with grass in those rotations

reported upon (table 18), the results are not too surprising. It was expected, however, that alfalfa in rotation with annual crops would ma-

^ Unpublished experimental data on file at United States Northern Great Plains

Field station. Mandan, N. Dak.
30 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

terially reduce the loss of nitrogen and carbon. Bracken and Larson

(5), working in Utah, reported that where aKalfa was grown in rotation

with wheat, the nitrogen content of the soil was maintained at a level

approximately 7 percent below that of virgin sod.

Earher work by Stewart (43) ^ on selected Utah farms, showed that

alfalfa caused a decrease in the nitrogen content of the soil compared to

that of virgin soil, whereas wheat continuously cropped, or alternately

cropped and fallowed, did not decrease the nitrogen content of the surface

foot of the soil.

Atkinson and Wright (4) reported results from Ottawa, Canada, which

showed that land which had been in grass with some alfalfa for 15 years

increased in soil nitrogen, while that under cultivation lost nitrogen.

Greaves and Jones (20), working with a Utah soil in jars, found that

the growth of alfalfa on this soil for 16 years and the removal of the crop

did not measurably increase the total nitrogen content. Where the

crop was returned to the soil, a highly significant gain in soil nitrogen

resulted. They state that '^probably there is a certain nitrogen balance

in some soils below which legumes may increase the soil nitrogen even

where the complete crop is removed; for this soil it is undoubtedly below

0.105 percent."

Soil Nitrogen in Relation to Nitrification Rate and

Uptake of Nitrogen by Plants

Laboratory Studies

In 1947, Allison and Sterling (2) conducted a study in which they used

soils from the rotation plots at Mandan, N. Dak., to determine whether

nitrate formation in a soil is markedly influenced by past cropping and

cultural practices or, on the other hand, is largely independent of such

treatments but correlated closely with total soil nitrogen. They concluded: '*In a given soil type and under like climatic conditions, thoroughly humified soil organic matter is fairly uniform in quahty regardless

of past agronomic treatment. The total nitrogen content under these

conditions appears to be a rough index of the nitrate-furnishing powers

of variously treated soils."

Earher work done by such investigators as Gainey (17) and Fraps

(15) showed a relationsriip between the nitrogen content of the soil and

its abiUty to produce nitrate. Fraps and Steiges (16) hsted several

factors which affected the nitrifying capacity of the soil. Waksman

(48) showed a definite relationship between the nitrifying capacity of

the soil and crop productivity. Albrecht (1), working with soils in Missouri, found that nitrate production of a soil decreased rapidly with

cropping, and that at the end of a 13-year period it had declined as much

as 50 percent.

To obtain further information on this problem, studies were undertaken in 1950 to determine the relationship of total nitrogen and nitrate

production in soils that varied widely as to type and total nitrogen

content. Soil samples were collected from selected rotation plots at 13

experimental stations in the Great Plains, which had been cropped for

30 years or more. Where possible, 1 row-crop plot and 1 small-grain

plot were sampled from each rotation; in the instance of alternate crop

and fallow, both the cropped and the fallow plots were sampled. In
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 31

most instances, sampling was done as soon as possible after harvest of

each crop.

From 8 to 12 samples were collected at the 0- to 6-inch depth from

9 of the stations, and from 27 to 33 samples were collected at 4 stations.

These samples were incubated in a constant-temperature room at Mandan,

N. Dak., by the procedure described earher in this pubHcation (p. 6).

Relationship of Total Nitrogen in the Soil and Nitrate Production

During a 6~Weeh Incubation Period

The total nitrogen percentage of the soils studied and the parts per

miUion of nitrate-nitrogen produced during a 6-week incubation period

are presented (appendix tables 45 and 46). The correlation coefficient

and regression equation for each location were computed to show the

relationship between the total nitrogen percentage of the soil and the

abiUty of the soil to produce nitrate. These values are presented

(table 20).

TABLE 20.—Correlation coefficients and regression equations showing the relationship

of the total nitrogen percentage (X) oj the 0- to Ô-inch depth of sou and the nitratenitrogen expressed in parts per million ( Y) produced during a 6-week incubation

period

Location

Number Correlation

of coeflaclent

samples (r)»

11 0.610*

29 .791**

10 .779**

11 .841**

7 .881**

12 .982**

12 .956**

29 .736**

11 . 816**

33 .564**

10 .338NS

11 .441NS

27 .933**

213 .562**

Regression

equation

Havre, Mont

Moccasin, Mont

Huntley, Mont

Sheridan, Wyo_ _

Archer, Wyo --

Newell, S. Dak

North Platte, NebrAkron, Colo

Colby, Kans

Hays Kans-_

Garden City, Kans..

Dalhart, Tex

Big Spring, Tex

All 13 locations.

r=270.71X-f4.9

F=229.41-X'-7.4

F=311.97X-8.7

y=401.09Jf-0.1

r=634.16Jr+0.2

y=473.48X-29.9

F=348.58^-1.1

r=362.14X+2.1

r=406.26X-7.ñ

y=313.73X+5.6

F=540.04X+18.2

r=320.5lX+4.8

r=369.92X-1.4

y=166.15X+15.4

» 1 asterisk (*) indicates significant at 6-percent level; 2 asterisks (**) indicate significant at 1-percent level;

NS indicates nonsignificant.

The correlation coefficient was significant at the 1-percent level at each

location except Havre., Mont., where it was significant at the 5-percent

level; and Garden City, Kans., and Dalhart, Tex., where it was nonsignificant. Too much confidence should not be placed in the data at

those locations where only 8 to 12 samples were collected, but these data

do indicate that there was a definite relationship between the 2 variables

at most locations.

However, nitrogen and other factors that were controlled during

incubation are not the only factors that may afiFect nitrification. For

example, although the correlation coefficient (r) at Hays tested highly

significant, r^ was only 0.307. This indicates that only about 31 percent

of the variation in nitrate production among the soils was associated with

total nitrogen. Inasmuch as phosphorus and calcium carbonate were

added, neither phosphorus nor high acidity should have been limiting.

418061—57 3
100

80 -

60 -

•S

a

e

i 40

•

1

a:

Z

20 -

•

"

•

-

•

•

"•

"

•

• •

•• ^^1

•

- V •

^^^^00""^^

-

• •

•

•. •.

•

.» , •.

• ••'^•V .*¿>^^''^^^ •

.. • •

• ••••* fL.>*^ • m

. '"è*^^"^ m

•

*

*

^

Y = 166.15X + 15.4

*•• r = 0.562** "

1 1 1 1 1 1 1 1 -L. 1 1 1 1 1 -JL0.04 0.12 0.16 0.20

Nitrogen in soil (percent)

0.24 0.28 0.32

FIGURE 5.—Regression of nitrate-nitrogen formed during a 6-week incubation period on the total nitrogen percentage

of the soil from all stations studied. (The 2 asterisks (**) indicate significant at 1-percent level.)

00

to

1^

O

Ir«

t^M

H

d

m

Ö

O

>

O

i
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 33

The carbon/nitrogen ratio may have been a factor, but carbon was not

determined on those particular samples.

It was also noted that at some locations the virgin-sod samples did not

produce as much nitrate-nitrogen in relation to their nitrogen content as

did the cropped soils. As discussed in a previous section of this publication (p. 12), virgin-sod samples had a higher carbon/nitrogen ratio than

did cropped soils. This might well account for a temporary depression

in nitrification rate.

The regression coefficients showed that the increase in nitrate production for each increase in percent total nitrogen varied considerably among

locations. Thus, the influence which total nitrogen had on nitrate

production depended somewhat on soil type. Possibly the quaUty of the

organic matter varied among soil types in such a way as to influence

nitrification, but no determinations were made of the quaUty of organic

matter.

Soil texture and structure may have also influenced nitrification indirectly by their effect on aeration, although the samples were shaken

periodically to increase aeration as much as possible.

To determine the relationship of nitrate production to total nitrogen

during the 6-week incubation period, the data from aU locations were

grouped together and the linear regression was computed. These data

are plotted and the regression line is shown (fig. 5). Although the correlation coefficient was significant at the 1-percent level, the points were

rather widely separated. The square of the coefficient would indicate

an association of about 32 percent.

The points were too numerous to attempt to differentiate between

locations, but there were 2 locations which were of considerable interest—

Garden City, Kans., and Moccasin, Mont. The data from 6 of the

samples from Garden City are shown in the upper left-hand side of the

chart, while Moccasin is represented by the numerous points in the lower

right-hand side. Surprisingly, most of the samples from Garden City

produced fairly large quantities of nitrate, even though the nitrogen content of the soil was below the group average. Most of the soils from

Moccasin were higher in nitrogen than were soils from any of the other

locations, yet the quantity of nitrate produced by these soils was comparatively low.

Relationship of Total Nitrogen in the Soil and Nitrate^Nitrogen

Production During 6, 12, 18, and 24 Weeks of Incubation

To determine the effects of incubation periods greater than 6 weeks

on nitrate formation, 1 high- and 1 low-nitrogen soil from each location

were incubated for 6, 12, 18, and 24 weeks. In most instances the highnitrogen soil was that from virgin sod and the low-nitrogen soil from

continuous row crop. DupUcate samples were incubated for each

period. The nitrate-nitrogen produced during each period is given in

parts per miUion (table 21).

It wiU be noted that in almost every instance, the greatest quantity of

nitrate per 6-week period was produced during the first 6-week period.

The exceptions were the high-nitrogen soils from Moccasin and the lownitrogen soils from Colby. The average values showed that the rate of

nitrification per 6-week period decreased with each succeeding period,

but this was not true of all locations. In some instances, production
34 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

during the third 6-week period was greater than during the second; in

other instances, production during the fourth period was greater than

during the third. This may have been due to an error in laboratory or

incubation procedures, or to some inherent property of the soil or some

type of organic matter.

TABLE 21.—Parts per million (p. p. m.) of nitrate-nitrogen produced by the 0- to

6-inch depth of high- and low-nitrogen soils from various stations during incubation periods of different length

Station

Havre, Mont

Moccasin, Mont

Huntley, Mont

Sheridan, Wyo

Archer, Wyo

NeweU, S. Dak

North Platte, Nebr..

Akron, Colo

Colby, Kans _.

Hays, Kans -..

Garden City, Kans..

Dalhart, Tex

Big Spring, Tex

Average of low-nitrogen soils. ..

Average of high-nitrogen soils..

Correlation coefficients for total

nitrogen versus nitrate-nitrogen i..

Nitrogen

In soil

Percent

0.075

.121

.179

.284

.076

.088

.100

.171

.077

.116

.101

.164

.074

.180

.066

.126

.071

.153

.094

.181

.064

.098

.044

.068

.024

.058

N itrate nitrogen produced during incubation for—

6 weeks

P. p. m.

21.3

39.7

43.2

44.1

10.7

19.2

41.3

73.6

30.3

60.1

14.1

45.8

22.6

66.7

27.1

38.1

16.1

42.3

27.0

44.4

59.3

85.5

11.3

25.5

9.0

23.8

25.6

46.1

. 514*"

12 weeks 18 weeks 24 weeks

P. p. m.

34.8

59.7

57.8

92.0

15.4

30.1

64.6

103.5

39.8

87.0

23.6

80.7

36.0

101.6

34.6

68.4

25.1

71.8

37.0

83.0

67.9

106.3

18.2

41.7

14.3

33.2

36.1

73.8

.725*-

. p. m.

39.5

67.4

76.1

165.1

25.6

47.8

79.8

138.7

58.4

99.1

29.6

105.7

44.0

131.9

44.1

78.3

30.4

97.7

47.3

97.3

80.0

108.0

21.2

54.9

19.4

42.6

45.8

95.0

.855*^

P. p. m.

42.3

80.7

77.4

196.8

28.6

48.6

87.6

141.1

60.7

112.7

33.2

113.9

63.1

143.2

46.8

95.9

47.7

118.6

53.6

106.4

84.7

127.5

25.6

67.1

20.9

48.1

50.9

107.0

.869*'

1 2 asterisks (**) indicate significant at 1-percent level.

EarUer in this pubUcation (p. 33), mention was made of the Garden

City soils, with a comparatively low total nitrogen content, as having

the abihty to produce large quantities of nitrate. It was also mentioned

that the soils at Moccasin, by contrast, had a high total nitrogen content

but produced much less nitrate. This was evident for the first 6-week

period; but for longer periods, the soil at Garden City reacted in about

the same way as did other soils of similar nitrogen content, and nitrate

production was well below that of the soils at Moccasin.

The correlation coefiicients showing the relationship between total

nitrogen and nitrate-nitrogen production were highest for either the 18-

or the 24-week incubation period. This would suggest that in order to

obtain the maximum relationship between these 2 variables, the incubation

period should have been greater than 12 weeks.

It will also be noted that the high-nitrogen soils at most of the locations maintained a higher level of production than did the low-nitrogen

soils. This proves that high-nitrogen soils not only produce a greater

quantity of nitrate, but are also able to maintain production over a longer
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 35

period oftime (fig. 6). The data for this chart were obtained by separating

the values shown in table 21 into 3 groups irrespective of location—those

soils with low, medium, or high total soil-nitrogen content. The mean

total nitrogen contents of the 3 groups of soils were 0.063, 0.106, and 0.187

percent, respectively.

For the high-nitrogen soils, the rate of nitrate production was much

greater than for the other soils, and it declined only sUghtly during the

Incubotion p*riod (w**ks)

FiGURB 6.—Nitrate-nitrogen formation as influenced by length of incubation and

nitrogen content of the soil.

12- and 18-week periods. During the 18- to 24-week periods, however,

there was a sharp drop in production. The low-nitrogen soils produced

approximately half the quantity of nitrate during the first 6-week period

as did the high-nitrogen soils. After the first period, the rate of production declined considerably, and it was nearly uniform throughout the

3 remaining periods. The rate of nitrate production during the first

6-week period for the medium-nitrogen soils was high, but it declined

after that time and closely approximated the average values for all soils«
36 TECHNICAL BULLETIN 1164, U. S, DEPT. OF AGRICULTURE

Allison and Sterling (2) and Carpenter and coworkers (8) found that

not only do high-nitrogen soils produce greater quantities of nitrate than

do low-nitrogen soils, but they continue nitrate production over longer

periods of time. The residts of the present study are in agreement with

their findings. AUison and Sterling also found that lime added to the

soil during incubation increased nitrification to a greater extent on lownitrogen soils than on high-nitrogen soils. It is possible that the

differences shown (fig. 6) would have been greater if Ume had not been

added to these soils.

Nitrate^Nitrogen Production from Cropped Soils as Compared

with Thatfrom Virgin Sod

Since it was shown that cropping caused a marked decline in the total

nitrogen content of several dryland soils, it appeared desirable to determine the effect of cropping on the abihty of such soils to produce nitrate.

The data from one rotation at each location were used, and these data

were compared with the values obtained from virgin sod. The results

are presented (table 22). Too much confidence should not be placed

on the limited data obtained from each location, but the combined residts from the various locations as a whole should at least be indicative.

TABLE 22.—Percentage of total nitrogen in the 0- to 6-inch depth of virgin sod and

cropped soil ^ at different locations in the Great Plains, the parts per million of

nitrate nitrogen produced by these soils during a 6-week incubation period, and

the percentage change ^ in total nitrogen and nitrate-nitrogen

Total nitrogen Nitrate-nitrogen Percent change »

Location

Virgin

sou

cropped Virgin

sou

Cropped Total

nitrogen

Nitratenitrogen

Havre, Mont.. __

Percent

0.121

.284

.171

.116

.166

.176

.126

.153

.181

.068

.068

Percent

0.083

.194

.121

.072

.103

.080

.089

.087

.098

.042

.026

P. p. m.

39.7

44.1

73.6

60.1

49.3

58.8

38.1

42.3

44.4

25.5

23.8

P. p. 771.

33.0

36.0

40.0

34.5

19.1

28.4

33.4

36.3

34.0

19.6

9.4

-31

-32

-29

-38

-38

-55

-29

-43

-46

-38

-65

-17

Moccasin, Mont - _ » _ _ -18

Ptieridan, Wyo . , -46

Archer, Wyo . -43

Newell, S. Dak -61

North Platte, Nebr -52

Akron, Colo _ -12

Colby, Kans -14

Hays, 'K'ftTis -23

Daíhárt, Tex_ ___ -23

Big Spring, Tex _ -60

Average _ _ .147 .090 45.4 29.4 -39 -35

1 Average of 2 plots from 1 rotation at each location. 2 Calculated by dividing the difference between the vh-gln-sod and cropped-soil values by the virgin sod

value, and multiplying by 100.

The loss of total nitrogen was more uniform between locations than

that of nitrate-nitrogen. The former ranged from 29 to 55 percent,

whereas the loss in nitrate production ranged from 12 to 61 percent.

At some locations, cropping had influenced nitrification less than total

nitrogen, while at other locations the reverse was true. The average

values were remarkably similar, however, being —39 percent for total

nitrogen and —35 percent for nitrate production. These results therefore indicate that not only was the total nitrogen content of the soils
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 37

reduced by an average of 39 percent, but the quantity of nitrate-nitrogen

these soils are able to produce was also reduced by almost the same

amount.

Effects of Previous Crop or Fallow on Nitrate Production

It was thought that the type of crop growing on the land immediately

prior to the time of sampling might iimuence nitrification during incubation. Since differences in total nitrogen content of the soil would influence the results, data were used only where the crops compared occurred

in the same rotation. That is, in order to compare nitrification in

soil from row-crop land with that from fallow, the data from the alternate row-crop and fallow plots were used. The same was true for comparing small-grain land and fallow. However, the inmoiediate effects

of row crops or fallow could not be compared with those of small grain

or fallow because of differences in total nitrogen content of the soil. To

get a direct comparison between row-crop and small-grain land, data

from a rotation containing both crops were used. Even with these precautions, there was still variation in nitrogen content of the soil at some

locations.

Data showing the influence of previous crop or fallow on nitratenitrogen production during a 6-week incubation period are presented

(table 23), together with the total nitrogen content of the soils. The

results were variable, but a portion of this variabiUty may have resulted

from differences in total nitrogen content of the soils compared. However, there was an indication that nitrate production was less after fallow

than after the alternate crop. This was true for 8 out of 11 locations for

the alternate row crop and fallow treatment, and for 7 out of 12 locations

for the alternate small-grain and fallow treatment. The average value

for fallow land was similar to that for the respective cropped land; these

values, however, were influenced to some extent by the extreme differences in the results at Garden City, particularly in the instance of alternate

row crop and fallow.

Crops growing on fallow land generally have a more abundant supply

of nitrate than those growing on previously cropped land; but the results

of this study suggest that this greater abundance of nitrate on fallow may

result from the greater quantity of nitrate present at seeding time of the

crop. After the crop has used this initial available nitrogen, the supply

may be no greater, or possibly not as great, on fallow land as on cropped

land.

The results from row-crop and small-grain land in a rotation also

varied from location to location. At 6 of the locations, nitrate production

was greater after row crops; at the other 6, it was greater after small

grains. The average for small-grain land was greater than for row-crop

land, but this value too was influenced by the extreme differences at

Garden City. With the results from this location omitted, the average

values would have been approximately the same.

In summarizing these results, it is apparent that nitrate production in

incubated soils was lower from fallow samples than from cropped samples,

from most locations; and except for a few instances, there was little

difference in nitrate production between row-crop and small-grain land.
38 TECHNICAL BULLETIN" 1164, U. S. DEFT. OF AGRICULTURE

TABLE 23.—Effects of previous crop or fallow on the parts per million (p. p. m,)

of nitrate-nitrogen produced during a 6-week incubation period by the 0- and

6-inch depth of soil from different locations in the Great Plains in 1950, and the

percentage total nitrogen content of these soils

Nitrate-nitrogen Total nitrogen

Location

Kow crop and

faUow

Small grain and

faUow Kotation

Row crop

and fallow

SmaU

grain and

fallow

Rotation

I'd

5^ H 11

o

1 02 5 =1

-d

o

o

1 Sfeb

QQ

Havre, Mont ..

Moccasin, Mont

Huntley, Mont

Sheridan, Wyo

Archer, Wyo

p.p.m.

28.3

22.3

16.5

40.6

P.p.m.

24.2

23.4

7.8

35.1

p.p.m.

21.2

31.1

17.1

48.3

45.1

19.9

31.8

35.1

33.9

58.5

51.7

22.8

15.6

P.p.m.

20.5

35.8

16.7

41.1

47.8

19.3

""24.'3

38.9

44.1

66.5

28.3

12.9

P.p.m.

33.7

41.8

23.2

40.4

31.8

18.4

31.7

31.6

37.9

35.3

52.9

18.4

P.p.m.

32.3

39.8

19.9

39.7

37.2

19.8

25.1

34.7

34.7

44.6

95.8

20.8

Percent

0.070

.136

.066

.100

Percent

0.073

.142

.064

.086

Percent

0.083

.197

.078

.105

.083

.106

.096

.076

.099

.125

.083

.045

.045

Percent

0.091

.192

.078

.091

.091

.098

'.'Ó76

.100

.113

.082

.046

.045

Percent

0.082

.214

.099

.126

.074

.102

.082

.086

.084

.113

.058

.042

Percent

0.084

.208

.100

.118

070

NeweU, 8. Dak

North Platte, Nebr.

Akron, Colo

Colby Kans

Hays, KaTis

11.3

20.5

24.2

11.4

28.1

30.1

14.0

8.0

14.7

'""is.'i

9.9

25.5

62.0

10.3

7.8

.082

.074

.057

.063

.075

.059

.043

.026

.091

'.'Ó57

.068

.089

.070

.038

.026

.104

.078

.089

.090

114

Garden City, Kans.

Dalhart. Tex

Big Spring, Tex

.065

.042

Average (10 locations) i 22.7 23.1 34.0 33.6 33.4 38.2 .075 .078 .100 .097 .101 .101

1 Archer, North Platte, and Big Spring omitted.

Field Studies

Nitrogen Uptake by Wheat in Relation to Nitrogen Content of Soil

Carpenter and coworkers (8) reported on the field study conducted in

1948 at Mandan, N. Dak., in which they showed the relationship between

the nitrogen taken up by wheat and the total nitrogen content of the soil.

They found that the quantities of nitrogen in wheat plants at tillering,

jointing, heading, and dough stages of growth were correlated with the

nitrogen content of the top 6 inches of soil and, except at heading, with

the 6- to 12-inch layer. The uptake of nitrogen on the low-nitrogen soils

fell off rapidly after the wheat reached the* heading stage while uptake

continued on the high-nitrogen soils. High correlations were obtained

between grain yield and the quantity of nitrogen in plants at all stages,

with the amount in the plants at jointing giving the best estimate of

yield. Although correlations significant at the 1-percent level were obtained between yield of grain and the nitrogen content of the soil for the

0- to 6-inch and the 6- to 12-inch depths, the relationships were not as

close as those between yield and nitrogen uptake by plants.

As previously stated (p. 36), results were in close agreement with those

obtained by Allison and Sterling (2), working with many of the same soils

and using the incubation procedure. The similarity in conclusions from

these two methods of study suggests that either procedure has merit.

The field study, however, seems more subject to variation from adverse

climatic conditions.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 39

Effects of Barnyard Manure on Nitrogen Content and Yield of

Wheat During One Season at Several Locations

It has been shown previously in this pubHcation (p. 22) that the application of barnyard manure reduced the loss of soil nitrogen more than

did a nonmanured cropping treatment, at every location where such a

comparison could be made. To estimate the effects of manure on the uptake of nitrogen, wheat plants grown in a manured and a nonmanured

rotation at each of 11 locations were analyzed for nitrogen content.

Information so obtained should give an indication of the beneficial

effects of mamuje on the liberation of available nitrogen in the soil.

Since early differences resulting from nutrients are often obscured by

shortages of moisture before final yields are obtained, samples were collected at an early stage of growth. The work of DeTm"k (ll) indicated

the probabiUty diat differences in available nutrients, brought about by

manure, would be reflected in the composition of the wheat plants during

the early growth stage.

In 1949, therefore, 100 wheat plants from a manured rotation and 100

from a nonmanured rotation were obtained from each of the 11 locations

in the Great Plains. The plan was to cUp the plants when they were from

6 to 8 inches tall, but this could not be done at some locations. Consequently, there was considerable variation in height and stage of growth of

the plants received. The samples were dried at 65° C, and were ground,

weighed, and analyzed for nitrogen.

The weight and the nitrogen content of the plant samples, as well as the

grain yields obtained from the plots, are presented (table 24). The weight

of 100 plants was greater on tne manured plots than on the unmanured

(check) plots at aU locations except Havre and Archer. At these 2 locations, the samples were not collected untü heading. It is possible that the

results would have been different if they had been collected at an earher

stage of growth.

The effect of manure, expressed as percentage increase over the check

plots, ranged from a decrease of 18 percent at Archer to an increase of

l46 percent at Sheridan. Although there was a wide range in results,

the data show that sizable increases in early growth were obtained on

manured land at the majority of the locations. Both winter and spring

wheat were sampled at North Platte; the former showed the greater

response to manure. Samples from Hays included 2 rates of manure

appUcation—6 and 12 tons. The increase from the 12-ton rate was more

than twice that from the 6-ton rate.

The weight of nitrogen in the 100 plants was increased at all locations

by the use of manure, except at Archer where there was no difference in

the results of the 2 treatments. The percentage increase over the check

Îlots ranged from 0 at Archer to 211 percent for winter wheat at North

latte.

The percentage of nitrogen in the plants was increased by the use of

manure at all locations except Mandan and Dickinson. The percentage

increase over the check plots ranged from a reduction of 10 percent at

Mandan to an increase of 40 percent at North Platte.

It is evident from these results that manure favorably influenced both

the weight and nitrogen content of the immature wheat plants at the
TABLE 24.—Weight and nitrogen content of immature wheat fiants, and final grain yields, from manured and nonmanured (check) rotations,

at 11 locations in the Great Plains. 1949

[Grain yields for various periods at the different locations are given for comparative purposes]

ê

Rotation

number Treatment

Stage of growth at

sampling

100 plants Grain jdelds per acre

Location

Weight Nitrogen Nitrogen Period Average

yield

Yield for

1949 only

/ 71

1 19

MiiTinrftd JEarly joüitüig {

Grams

63.1

24.6

Orams

1.65

.79

Percent

2.91

3.22

Years

} 191&-49

Bushels

f 18.8

\ 16.3

Bushels

U2.2 Mandan, N. Dak unecK—_ Í7.3

Percentaee increase over check 116 96 -10 23 67

/ 71

I 1Ö

M?"iiireil JTlllerlng {

23.4

12.1

0.80

.42

3.40

3.46 1 1924-49 f 17.9

I 14.5

12.0 Dickinson, N. Dak _ _ _

onecK J 8.5

PfiTcentace increase over check

r

93

164.5

172.0

90 -2 23 41

Manured „_._

JHeaded / 71

I 19

6.25

5.06

3.19

2.94 } 1916-49 Í 10.1

\ 10.6

2.2

Havre, Mont unecK J 2.8

Percentage Increase over check.

r

-4

68.8

46.0

4

3.02

2.09

8

6.13

4.66

-4

/ 12.3

\ 13.4

-21

} 1915-49 f 69

I 13

MftTiiired JEarly johitlng 10.8 Huntley, Mont 9.6

Fercentase Increase over checks

r

28

163.0

62.2

44 13 -8 14

[jointing f 71

I 19

Mftnnred 3.23

1.26

2.11

2.03 } 1918-49 Í 22.0I 20.8

32.2 Sheridan. "Wvo _ - - Check 26.2

Percentftpre increftsft ov^r check

r

146

263.0

310.0

166 4 6 28

/ 71

1 19

Manured JHeaded —-

4.00

4.00

1.68

1.29 } 1914-47 / 7.4 Archer, Wyo -— J \ 10.3 S

Percentage Increase over check . _ _

r

-18

36.4

20.9

0

1.49

.76

22

4.20

3.64

-27

/ 16.2

I 17.2 } 1909-49 / 71

I 19

Manured. ..-. JTUlerlng 13.0 Newell, S. Dak Check 13.5 J

Percentace tncrease over check 69 96 16 -6 -4

—

Ö

O

>

H

gH
^orth Platte, Nebr f »268

\ » MF-I

Manured ..

jjolntlng f 448.6

I 202.0

13.64

4.36

3.02

2.16 } 1937-49 f 28.2

\ 30.9

19.7

Check _ 12.2

Percentage Increase over check.. .._ . .. 122 211 40 -9 61

-North Platte. Nebr f <43

I 43

Manured- — xTftintlru? f 90.2

t 60.3

2.00

1.06

2.22

2.10 } 1937-49 f 8.8

I 8.0

8.8

Check 1.8

Percentage increase over check -„ .__ 79 89 6 10 389

Oolby, TTf^ns. / 664

\ 665

Manured JEarly jointing f 108.6

\ 98.6

3.80

3.04

3.50

3.09 } 1932-49 f 7.7\ 6.9

(*)

Check _ __

Percentage Increase over check 10 25 13 31

Hays, TTans .. ..... . ,,......„.

f 556

t 553

Manure (6 tons)...

Check _

jjointtng / 32.6

I 27.6

1.24

.98

3.80

3.68 } 1914-49 f 22.6

1 24.2

2.8

2.7

Percentage Increase over check 18 26 6 -7 4

Hays, Kans .. .. . . . ,. ..^ .....

f 560

I 553

Manure (12 tons).

Check jlnlTitiTig r 41.0

I 27.6

1.69

.98

4.13

3.68 1 1914-49 f 20.2\ 24.2

3.8

2 7

Percentage Increase over check 49 72 16 -17 41 "

Woodward. Okla f H-7/311-0

\ H-6/309-C

Manured }Prebooting-._ / 763.5

I 373.9

11.91

5.68

1.66

1.52 } 1932-49 f 24.1

1 23.1

25.8

Check __. 24.2

Percentage Increase over check . 104 110 3 4 7

1 Damaged by hall.

« Hailed out.

» Winter wheat. Stands were poor In 1949.

* Spring wheat. Severely Injured by greenbugs.
42 TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

majority of the locations, indicating a greater abundance of available

nitrogen in the soil. This favorable effect in the earUer stages of growth

was reflected in some instances in the yields of grain obtained in 1949.

For example, at Mandan, Dickinson, Sheridan, and North Platte, marked

increases were noted in growth early in the season from the use of manure;

and these locations showed the greatest increase in grain yields. At

Newell, however, there was a marked increase in early growth but a shght

reduction in grain yield. At Woodward, there was also a marked increase

in early growth due to manuring, but only a shght increase was obtained

in yield. These residts show that increased growth in the early stages of

the wheat plant is not always indicative of higher grain yields, particularly in the Great Plains region where moisture is an important factor.

The longtime average yields show that in 7 of the 13 comparisons, the

check plot outyielded the plots receiving manure. In 1949 there were

only 2 such instances. Furthermore, the percentage increase in 1949

was greater in every instance than that for the longtime average. Because

the 1949 data are for 1 year only, they should not be considered conclusive; but they do indicate that the response to manure should become

greater with time, inasmuch as nonmanured land declines in fertihty at

a more rapid rate. The effects of barnyard manure on crop yields are

discussed more fully in the next section.

Efifects of Soil-Nitrogen Changes on Crop Yields

Probably the first question to be raised in connection with changes

in soil nitrogen is, "What effect have these changes had on crop yields?"

That is, have the losses or gains in soil nitrogen over a period of years had

any marked effect on crop yields? Jenny {24) referred to work done at

Wooster, Ohio, which showed an almost linear relationship between the

decline in soil nitrogen and com yields under a continuous-cropping

system. Smith and coworkeis (42) reported on organic matter and yield

trends with cropping on the Texas Blacklands, and stated that during a

20-year period of continuous cropping to corn, cotton, or oats, there was

no obvious trend in yield with the passing of time. In one instance,

however, they were able to detect a tendency toward lower com yields

with time when extremely poor yields caused by weather were eliminated.

Hill (22), reporting on wheat-yield trends in Canada, showed that where

an alternate wheat and fallow system has been practiced for a 40-year

period, there has been no important change in yield. He beheves that

this practice can be continued profitably for many years in western

Canada if soil erosion and weeds are controlled.

To determine yield trends with the passing of time in the Great Plains,

where variations in weather are extreme, seemed to be an almost impossible

task. Rainfall is the main limiting factor—not only the amount that falls

during the crop year, but also its distribution. However, as long as no

trends in the weather develop with time, perhaps an estimate of yield

trends can be made. Or, if trends in weather do develop, these can be

eliminated to some extent by the use of multiple regression. Other

factors which add to the difficulties of determining yield trends are insect

pests, the occurrence of new strains of plant diseases, changes in varieties,

and weeds.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 43

To simplify the task of determining yield trends, the data from only

6 locations were analyzed ^ and their results are given (table 25).

Because of the possibiUty of a trend in precipitation with the passing

of time, multiple regression was used. Thus, there were 2 independent

variables—precipitation (Xi) and years of cropping (X2). The dependent

variable was yield (Y).

The yields of com grain, com stover, and wheat grain imder 4 different

cropping systems were used in the computations. The 4 systems were

continuous cropping, alternate crop and fallow, a 3-year rotation without

manure, and a similar rotation with manure. The 3-year rotations consisted of com, wheat, oats, at all locations except Hays, where it was

kafir, fallow, wheat. Years with zero yields in which hail damage occurred

were omitted.

From time to time, changes were made in varieties at some of the

stations, and these no doubt influenced the results to a certain extent.

However, it was felt that these changes were not of sufficient magnitude

to be serious; fairly large differences would be required to be significant,

because of the extreme variations in annual yields.

In these computations, the amount of precipitation assigned to each

year of cropping was that amount which fell between harvest of one

crop and harvest of the next. Thus, the amounts varied, not only with

the crop but also with the cropping system. (See appendix table 47.)

For example, in the instance of continuous wheat, the amount of precipitation for a given year would be that which fell between one wheat harvest

and the next. In the instance of alternate wheat and fallow, it would

be that which fell during a 2-year period. It was thought that these

values were the best obtainable under the circumstances and would be

better than those obtained by using annual or seasonal precipitation,

although it was recognized that intensity of rainfall, distribution, runoff,

and evaporation play important parts in determining the amount of water

available for plant use.

The results obtained from the multiple-regression analysis (table 25)

are based on the assumption that the regression was linear. This may or

may not be correct for all locations. The regression was tested for

curvilinearity at one location, but only sUght evidence of this was found.

The simple correlation coefficients (r) show the relationship between

any two of the variables. The correlation coefficients for precipitation

and years of cropping {Xi and X2) show that there was very little relationship between these two variables at all locations, except for a few

instances at Sheridan, Wyo., and Hays, Kans. In other words, there

were no marked trends in precipitation with the passing of time, except

as just explained.

The correlation coefficients for yield and precipitation ( Y and Xi) show

the high dependency of yield on moisture in most instances. There was

only one instance in which the relationship between yield of wheat and

precipitation did not show significance, Dut there were several such

instances with respect to row-crop yields and precipitation. The rela8 The authors are indebted to D. D. Mason, former biometrician, and E. J. Koch,

associate biometrician, Bureau of Plant Industry, Soils, and Agricultural Engineering,

Beltsville, Md., for their assistance in the statistical analyses.
TABLE

cropping 26,-'Simple correlation coefficients (r) for comparing the relationship between any 2 of the variables—precipitation (Xi), years of

mg (X2) and yield (Y) ; multiple-correlation coefficients (R) ; and the multiple-regression equation; at 6 locations in the Great Plains

MANDAN, N. DAK. (1916-46)

Crops and treatment Number

of years 1

Simple correlation (r)» Multiple

correlation

(Ä)»

Multiple-regression equation »

Xi and Xs FandXi YaxidXi

Com (grain):

Continuous 29

29

29

29

30

30

30

30

29

30

29

27

0.267

.118

.178

.178

.203

.086

.231

.231

.178

.062

.116

.167

0.142

-.133

.366

.469*

-.033

-.277

.160

.469*

.718**

.687**

.633**

.486*

-0.272

-.386*

-.072

-.122

-. 616**

-. 627**

-.279

.026

.283

.206

-.022

.331

0.349

.396

.392

.613*

.622**

.676**

.366

.467*

.736**

.613**

.640**

.648*

F=24.464-a69 Xi-0.34 Xi

F=43.19-0.16 Xi-0.41 Xj*

F=10.91-fl.l4 Xi*-0A5 Xi

F=-6.64-1-2.26 Xi**-0.33 Xi

F=2,603.1-}-16.9 Xi-41.0 Xi**

F=3,866.8-33.2 Xi-47.2 Xi**

F=l,608.2-h29.6 Xi-16.6 Xi

F=l,164.8-hll0.8 Xi*-7.6 Xi

r=-17.41+1.94 Xi**+0.16 Xi

F=-14.37+1.07 Xi**+0.21 Xj

r=-3.29+1.60 Xi**-OM Xi

F=-6.06+1.69 Xi*+0.27 Xi

Alternate fallow ___

Rotation without manure _

Rotation with manure __

Com (stover):

Continuous

Alternate fallow

Rotation without manure

Rotation with manure

Spring wheat (grain):

Continuous

Alternate faUow

Rotation without manure

Rotation with manure ___

DICKINSON, N. DAK. (1908-49)

Com (grain):

Continuous

Alternate fallow

Rotation without manure. __

Rotation with manure

Com (stover):

Continuous

Alternate fallow

Rotation without manure

Rotation with manure _

Spring wheat (grain):

Continuous ___

Alternate fallow

Rotation without manure

Rotation with manure

-0.041

.047

-.006

-.006

.072

.046

.028

.028

.062

.068

.144

.139

0.637**

-.061

.646**

.667**

.427**

-.076

. 673**

.766**

.694*"

.663*'

-0.268

-.273

-.109

-.013

-.202

-.073

-.190

-.001

-.120

-.082

-.109

+.066

0. 691*'

.277

.664*-

.667*"

.103

. 705*'

.766*'

.706**

.697**

.726**

.664**

F=5.69+1.68 Xi**-0.24 Xi

F=37.80-0.09 Xi-0.27 Xi

F=-18.23+2.30 Xi**-0.11 Xi

r=-33.10+3.21 Xi**-0.01 Xi

F=l,625.8+156.6 Xi**-26.6 Xi

F=4,640.8-19.4 Xi-10.1 Xi

r=-987.1+282.6 Xi**-27.0 Xi

r=-3,307.3+466.2 Xi**-4.2 Xi

F=-12.07+1.72 Xi**-0.10 Xi

F=-16.60+1.26 Xi**-0.11 Xi

F=-9.09+1.93 Xi**-0.16 Xi

F=-18.13+2.77 Xi**-0.03 Xi

ÇQ

Ö

o

i>

o

&
HAVRE, MONT. (1917-49)

Com (grain):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Com (stover):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Spring wheat (grain):

Continuous

Alternate faUow

Rotation without manure

Rotation with manure

-0.227

-.157

-.352

-.352

-.182

-.287

-.207

-.207

-.146

-.270

-.125

-.125

0.645**

.581**

.681**

.718** . 479**

.047

.708**

.710**

.787**

.737**

.764**

.670**

-0.165

-.058

-.143

-.272

-.648**

-.431*

-.447*

-.417*

-.130

.025

-.151

-.250

0.645**

.582*

.689* . 718**

.746**

.438* . 772** . 762** . 787** . 773**

.766** . 691**

F=-10.09+2.25 Xi**-0.02 Xt

F=-7.83+1.31 Xi**+0.04 Xt

F=-21.11+2.70 Xi**+0.14 Xi

y=-29.73+3.46 Xi**-OM Xt

y=1,579.0+127.5 Xi**-58.S Xt**

F=4,167.4-25.2 Xi-59.6 Xt*

y=-372.0+223.5 Xi**-33.6 Xt*

y=-833.7+288.6 Xi**-dS.5 Xt*

y=-14.81+1.99 Xi**-0.01 Xt

y=-36.05+2.02 Xi**+0.25 Xt

y=-13.01+2.43 Xi**-0.05 Xt

F=-9.72+2.36 Xi**-0.17 Xt

SHERIDAN, WYO. (1918-49)

Corn (grain):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Corn (stover) :

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Spring wheat (grain):

Continuous

Alternate fallow

Rotation without manure.

Rotatlim with manure—

0.094 -0.698**

.099 -.488**

.408* -.604**

.460* -.442*

.279 -.464**

-.120 -.427*

.642** -.326

.657** -.164

.575** -.036

.656** .263

.594** .086

.726** .247

0.747**

.696**

.760**

.760**

.644**

.433*

.768** . 776**

.667**

.600**

.727**

r=17.71+0.82X1-0.68 Xt**

F=14.22+0.48 Xi*-0.49 Xt**

y=-3.78+1.78 Xi*-0.63 Xt**

y=-6.36+1.83 Xi**-0.66 Xt**

y=631.7+76.1 Xx** -41.0 Xt**

y=l,368.6+7.2 Xi-26.6 Xt*

F=-86.8+116.0 Xx** -38.7 Xt**

y»-409.9+162.1 Xi**-36.4 Xt*'

F=-6.18+1.42 Xi**-0.22 Xt

F=-13.97+1.22 Xi**-0.04 Xt

y»-8.49+1.88 Xi-0.09 Xt

y=-16.19+2.30 Xi**+0.07 Xt

See footnotes at end of table.
TABLE 25.—Simple correlation coefficients (r) for comparing the relationship between any 2 of the variables—precipitation (Xi), years of cropping (X2) and yield (Y) ; multiple-correlation coefficients (R) ; and the multiple-regression equation; at 6 locations in the Great Plains—Con.

ARCHER, WYO. (1914-45)

Crops and treatment Number

of years 1

Simple correlation (r)^ Multiple

correlation

(Ä)i

Multiple-regression equation a

Xi and Xi FandXi FandXa

Corn, (grain):

Continuous ___ _ 27

28

26

26

30

30

30

30

29

30

29

29

0.208

.141

.105

.105

.117

.076

.000

.000

.081

.032

.163

.163

0.178

.203

.350

.460*

.056

.136

.282

.350

.431*

.400*

.566**

.553**

-0.309

-.090

-.266

-.072

-.449*

-.326

-. 513**

-. 374*

-.154

.041

-.121

-.155

0.396

.235

.464

.476

.462*

.364

.585**

.512*

.471*

.401

.606**

.606**

F=12.84+0.50 Xi-0.27 Xj

Alternate fallow _ _ __ _ _ _ _ ___ _ F=7.94+0.37 Xi—0.09 Xt

Rotation without manure F=3.90+0.89 Xi-0.25 Xi

Rotation with mauurpi .. F=—6.61+1.23 Xi*—0.11 Xt

Corn, (stover):

Continuous r=1,736.0+28.8 Xi-43.2 Xi*

A Iternate fallow F=1,105.0+29.7 Xi—27.7 Xi

Rotation without manure. _._ .._ F=960.9+77.8 Xi-48.6 Xi**

Rotation with manurft , F=412.6+97.8 Xi*-36.9 Xi*

F=—3.87+0.98 Xi*—0.14 Xi

Spring wheat, (grain):

CoT»tinuous _ . ... . .,,.

A iternate fallow .. - ... ... F=-5.89+0.65 Xi*+0.02 Xi

Rotation without manure. y=-1.94+1.37 Xi**-0.17 Xi

Rotation with manure _ _ __ __ __ __ _ F=-2.61+1.48 Xi**-0.21 Xi

HAYS, KANS. (1914r48)

Ö

O

>

O

d

Kafir (grain):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Kafir (stover):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

Winter wheat (grain):

Continuous

Alternate fallow

Rotation without manure.

Rotation with manure

0.296 0.623**

.439* .357

.375 .460*

.399 .437*

.110 .537**

.142 .527**

.087 .682**

.087 .680**

.274 .400*

.175 .163

.168 .463**

.168 .395*

0.062

.042

.105

.194

-.402*

-. 361*

-.101

.022

-.012

-.094

.027

-.102

0. 636**

.379

.466

.438

. 710**

.687**

. 701**

.681**

.419

.205

.466*

.430*

y=-29.51+2.35 Xi**-0.26 Xi

y=-26.13+1.45 Xi-0.34 Xi

r=-32.64+2.04 Xi*-0.16 Xi

F=-37.97+2.08 Xi+0.06 Xi

F=+l,017.9+202.1 Xi**-86.5 Xi*'

r=-637.8+179.1 Xi**-98.4 Xi**

F=-3,354.8+283.6X1**-37.6 Xi

y=-3,949.1+294.8 Xi**-9.2 Xi

F=-0.72+0.91 Xi*-0.16 Xi

y=+13.16+0.32 Xi-0.16 Xi

F=-8.23+0.90 Xi**-0.07 Xi

F=-2.01+0.72 Xi*-0.21 Xi

1 Number of years of data used In multiple regression. Years with zero yields, or when crops were damaged by hall, were omitted.

21 asterisk (*) indicates significant at 6-percent level; 2 asterisks (**) indicate significant at 1-percent level.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 47

tionship between yield on summer fallow and precipitation was lower

in many instances, as would be expected.

The relationship between yield and years of cropping is shown by

the r value for i and X2. These coefficients, however, are not independent of the effect of precipitation, although precipitation would

influence the results only in instances in which it was related to years of

cropping. As these correlations are not independent of the effects of

precipitation, the effects of years of cropping on yield for a constant

precipitation value are discussed fully in a later paragraph.

The multiple correlation coefficients (JR) show the combined relationship

of both precipitation and years of cropping to yield. Although many

of these tested highly signfficant, the largest coefficient was 0.787 for

continuous wheat at Havre, Mont. The square of this coefficient would

indicate that 62 percent of the variation in yield is the result of precipitation and years of cropping. Thus, even though many of the coefiGicients

tested highly significant, precipitation and years of cropping did not

account for a particularly large percentage of the variation in yield.

In the regression equation for calculating yield from precipitation and

years of cropping, the coefficient of Xi indicates the yield change per

inch of change in precipitation for a constant number of years of cropping.

The negative values for alternate com and fallow at some locations are

difficult to explain. It was expected that com on fallow would not

be influenced as much by precipitation as com on cropped land, but it

was not expected that a negative relationship would be obtained. Also,

the regression coefficients for precipitation were higher in the rotation

receiving manure than in the rotation without manure, in every instance

except two. This was to be expected, inasmuch as the greater fertihty

from maniiring should result in greater increases in yield per inch of

water.

The coefficient of X2 indicates the change in yield per year of cropping

for a constant precipitation value. It mil be noted that com or kafir

grain and stover yields declined in every instance except three. However,

not all of these tested significant. When the crop was wheat, both increases and decreases were obtained, but none tested significant. From

these results, it is apparent that com or kafir yields were sigmficantly

reduced by cropping at some locations, whereas wheat yields were not.

Many of the yield changes per year appeared high but were found to be

nonsignificant. Apparently, the variation in yield was so great that

extremely large yield changes were required to test significant.

(See appendix table 47 for actual average yields and calculated yields

for the first and last years of the cropping periods shown.)

A clearer picture of the effect of years of cropping on yields is presented

(table 26), together with the changes that occurred in soil nitrogen.

The percentage change in soil nitrogen was computed as shown earlier

(p. 16), and the percentage change in yield was calculated (see footnote 1

to table 26). The data are not comparable across stations, as yield

change is a direct function of years of cropping.

It will be noted that the decline in yield was greater under continuous

cropping than under alternate cropping and fallow in nearly every instance, and the difference was more striking for wheat than for row crops.

These results are in agreement with those obtained by Greaves and

418061—57 4
48 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

TABLE 26.—Comparison of the percentage change in soil nitrogen with the percentage

change in yield ^ of row crops ^ and wheat under 4 cropving systems at 6 locations

ROW CROP, GRAIN

Period

Continuous Alternate faUow Rotation

Location

Sounitrogen

change

Yield

change

SoUnitrogen

change

Yield

change

Without manureWith manure

SoUnitrogen

change

Yield

change

Sounitrogen

change

Yield

change

Mandan, N. Dak

DipkinsnTi, N. Dak

Years

30

40

31

30

34

30

Percent

-35

-58

-50

-30

-43

-29

Percent

-29

-31

-4

-67

-46

-36

Percent

-40

-60

-53

-35

-43

-40

Percent

-32

-31

+5

-50

-17

-27

Percent

-34

-49

-48

-30

-37

-35

Percent

-15

-20

32

-73

-43

-17

Percent

0

-39

-26

-2

-19

-22

Percent

-32

-2

Havre, Mont__ - -- -8

Sheridan, Wyo -69

Archer, Wyo -24

TTays, Kans 7

Average 33 -41 -36 -45 -25 -39 -23 -18 —21

ROW CROP, STOVER

MftTidftTi, N. Dak 30

40

31

30

34

30

-35

-58

-50

-30

-43

-29

-45

-25

-61

-68

-69

-50

-40

-60

-53

-35

-43

-40

-51

-10

-53

-50

-48

-41

-34

-49

-48

-30

-37

-35

-24

-27

-42

-63

-72

-22

0

-39

-26

-2

-19

-22

-8

Dickinson, N. Dak

Havre, Mont

-3

-42

Sheridan, Wyo -50

Archer, Wyo

Hays, TTaTis

-57

-6

Average -- 33 -41 -53 -45 -42 -39 -42 -18 -28

WHEAT, GRAIN

Mandan, N. Dak

DIckiTison, N. Dak._

30

40

31

30

34

30

-19

-44

-44

-21

-32

-10

37

-26

-4

-40

-47

-24

-26

-50

-42

-27

-33

-7

34

-19

66

-5

5

-18

-34

-49

-48

-30

-37

-35

-14

-33

-13

-13

-43

-9

0

-39

-26

-2

-19

-22

49

-6

Havre, Mont__ __ -36

Sheridan, Wyo 10

Archer, Wyo . _-_ _ -60

TTftys, R'ftTis -26

Average 33 -28 -17 -31 11 -39 -21 -18 -10

1 The percentage yield change was computed by dividing the calculated yield change for the period by the

calculated yield hi the first year and multiplying by 100. The yield change was determined by multiplying

the regression coeflacient for Xt. hi the multiple-regression equation, by the number of years in the period.

The yield in the first year was determined from the multiple-regression equation, by substituting the average precipitation for the period for Xu and by substituting 1 for Xt.

> The row crop was com at all locations except Hays, in which it was kafir.

Bracken (19) in Utah and by Hill (22) in Canada. The authors of this

bulletin agree with Hill's explanation (p. 15): "The fact that yields of

wheat on fallow have been maintained, whereas those of wheat following

wheat have fallen off, may be due partially to the improved availabiUty

of nutrients after the fallow season. As the native fertiUty is gradually

reduced, this factor may become more important."

Growing the crops in rotation without manure reduced the decUne in

yield at some locations more than did either continuous or alternate

fallow, but increased it at others. The average values show that the

decUne in yield for crops in rotation was similar to that of alternate fallow in the instance of row crops but greater in the instance of wheat.

In comparing the nonmanured and the manured rotations, the results
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 49

were found to be variable. The most consistent results were those for

row-crop stover, for which the decline in yield was equal to or less than

that ofthe nonmanured rotation at every location. Why manuring should

cause a greater decrease in yield with the passing of time than nonmanuring at some locations is not known, for the nitrogen content of the soil had

not been increased above its original value at any of the locations, and

therefore the tendency for burning should not have increased. Hill

(22, p. 15) stated: '^Yields [of wheat at Brandon, Manitoba], have been

somewhat better in the manured rotation as compared to the unmanured,

but not enough to warrant the cost of applying the manure." This

statement is no doubt true for some of the locations reported on in this

Sublication. With continued cropping of the soil, however, the benefit

erived from manuring should increase.

In comparing the percentage change in soil nitrogen with the percentage

change in yield, it will be noted that there is no apparent relationship

between the two. At one location a low percentage change in nitrogen

may result in a large change in yield, whereas at another location the

reverse may be true. Climate and the adaptibiUty of the crop may be

factors influencing the results. For example, the soil at one location may

have had greater fertility than was necessary to produce maximum yields

under the climatic conditions at that location. Thus, fairly large declines in fertility could occur without seriously influencing yields. On

the other hand, at another location the fertiUty may have originally been

barely adequate to produce good yields, in which instance even small

declines in fertility may have reduced yields considerably.

Since periodic soil-nitrogen determinations had been made at Sheridan,

Wyo., and at Hays, Kans., it was possible to compare periodic changes in

nitrogen with changes in crops yields. To make them comparable, both

the nitrogen and the yields were placed on a relative basis. In other

words, the nitrogen content of the soil at each sampling date was expressed as a percentage of the nitrogen content on the first sampling

date. The yield for each subsequent date was calculated from the multiple-regression equation, the average precipitation for the period being

used as Xi, and the calculated yield for each date being expressed as a

percentage ofthe yield on the first date. The results are presented (table

27). Sou-nitrogen data were not available for all sampling dates for

some of the cropping treatments.

At Sheridan, the relative values for com and stover yields were lower

than for soil nitrogen in every instance, while those for wheat yields were

higher in every instance except for that which was continuously cropped.

This would indicate that com yields have decUned at a greater rate than

soil nitrogen, while the reverse is true for wheat. The com and wheat

grain yields are presented graphically (figs. 7 and 8, respectively), together

with the relative soil-ntirogen values, to bring out these points more

clearly.

In the manured rotation, the extreme contrast in yield trends of com,

as compared with those of wheat, is difl&cult to explain. Both the corn

and the wheat were grown in the same rotation on the same soil; yet com

yields dropped sharply and wheat yields increased shghtly with Uttle

change ia soil nitrogen. Apparently, there is some factor that influences

com yields but does not affect wheat yields.
50 TECHNICAL BULLETIN 1164, IT. S. DEPT. OF AGRICULTURE

TABLE 27.—Comparison of relative content of soil nitrogen with relative yield of

row crops and wheai under 4 cropping treaiments during different years at

Sheridany Wyo.j and Hays, Kans.

SHERIDAN, WYO.

Continuous Alternate

Rotation

Crops and year

Without manure With manure

Relative

sou nitrogen

Relative

yield

Relative

soil nitrogen

Relative

yield

Relative

sou nitrogen

Relative

yield

Relative

sou nitrogen

Relative

yield

Com, grain:

1917

Percent

100

Percent

100

78

56

33

100

77

56

32

100

87

73

60

Percent

100

86

77

66

100

86

77

66

100

91

80

73

Percent

100

83

66

60

100

83

66

60

100

98

97

96

Percent

100

Percent

100

76

61

27

100

79

68

37

100

96

91

87

Percent

100

96

96

98

100

96

96

98

100

96

96

98

Percent

100

1927 77

1937 64

1947 - - - 70

100

70

100

31

Com, stover:

1917 100

1927 83

1937 - - 67

1947 70

100

70

100

---

60

Wheat, grain:

1917 100

1927 103

1937 107

1947 - 79 110

HAYS, KANS.

Kafir, grain:

1916 100 100

87

73

64

100

82

63

60

100

92

83

76

100

81

68

60

100

81

68

60

100

98

90

93

100

90

80

73

100

86

70

69

100

93

87

82

100 100

94

87

83

100

92

84

78

100

97

94

91

100 100

1927 102

1938 74

71

100

68

65

100

68"

65

100

81

79

100

105

1946 107

Kafir, stover:

1916

1927

100

98

1938 74

71

100

96

88

90

81

79

100

96

1946 94

Wheat, grain:

1916 100

1927 90

1938 68

66

81

79

81

1946 74

At Hays, the relative values for yield of kafir grain and stover were

higher than for soil nitrogen in every instance except for stover under

continuous cropping. Relative values for kafir-grain yields under continuous cropping and stover yields under alternate fallow were approximately equal to those for soil nitrogen. For wheat, the relative yield

values were less than those of soil nitrogen under continuous and alternate cropping, greater in a rotation without manure, and about equal in

a rotation with manure. These results were almost the reverse of those

obtained at Sheridan.

From these results, it woidd be difficult to make an overall statement

as to the effects on crop yields of losses or gains in soil nitrogen. Apparently, the effect was considerable at some locations and only sUght at

others, but row crops in general were influenced more than wheat.

Further evidence that nitrogen may not be limiting wheat yields at

many of the locations is shown by the residts of fertilizer tests conducted
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 51

^

I

1

ë

1

"O

e

o

tu

•

>.

e

100

80

•N

Soil nitrogen ^^

\

^^ •i

o

&

1 .

i.

60

1-

Yield

•Continuous

-^

^

5

i

2--Alternate fallow ^X^ 2

40 3-

4-

-Rotation without manure

-Rotation with manure

1 1 %3

1917 1927 1937 1947

Y«ar

FIGURE 7.—Comparison of relative com-çrain yields and relative soil-nitrogen values

on different dates from 4 croppmg treatments at Sheridan, Wyo.

at 13 locations in the Great Plains, 1950-52. The average yields obtained from these tests are presented (table 28). It will be noted that

Mandan and Hays were the only locations that showed much response

to nitrogen. In individual years, however, response was observed at

some of the other locations. It is interesting to note that at Garden City,

Kans., and Woodward, Okla., no response was obtained, even though the

nitrogen content of the soil is low at those locations. The discussion on

nitrification (p. 33) brought out the fact that the Garden City soils had

a relatively high rate of nitrification in relation to the total sou-nitrogen

level; this may have provided the necessary soluble nitrate-nitrogen for

crop production.

Moisture is no doubt limiting the response to nitrogen fertilizer in

many instances. More moisture is generally available on fallowed than

on cropped land, but at the same time there is usually more available

nitrogen present under fallow. Thus, nitrogen fertilizers should not be

expected greatly to influence yields under this treatment.

More emphasis should be placed on conserving moisture so that crops
52 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

r 100 -

•2 80 -

60

^ 40

Soil nitrogen

Yield

1-Continuous

2-Alternate fallow

3-Rotation without manure

4-Rotation with manure

1?17 1927 1937 1947

Year

FIGURE 8.—Coinparison of relative wheat-grain yields and relative soil-nitrogen values

on different dates from 4 cropping treatments at Sheridan, Wjo.

TABLE 28.—Total nitrogen content of soily and average yield of wheat with and

without fertilizery at IS locations in the Great Plains^ 1960-52

Years Previous crop

Soil nitrogen Grain yield

Location

Oto 6

inches

6 to 12

Inches

Check Nitrogen

applied 1

Mandan, N. Dak.. ___

Number

2

2

2

3

3

3

2

2

2

1

1

3

1

3

Wheat

Percent

0.118

.168

.218

.092

.120

.136

.087

.089

Percent

0.112

.124

.191

.072

.098

.123

.087

.085

Bushels

9.5

13.8

16.8

17.3

11.6

16.4

21.5

26.0

22.9

6.9

16.3

22.6

18.3

22.3

Bushels

13.1

13.2

17.2

15.7

11.5

17.8

21.4

26.7

21 8

DIoldTifwin, ISr. DftV Crested wheat and

wheat.

Moccasin, Mont Wheat

Huntley, Mont _ Fallow

NeweU, S. Dak.., Wheat

Sheridan, Wyo _ Wheat

Archer, Wyo Tallow

Nort;h Platte, Nebr__ __

Akron, Colo _._ --""dollir""

DJ Wheat 6.3

16.1

29.6

18 2

Colby, Kans Pallow , .090

.116

.064

.049

.096

.095

.068

.053

Hays, Kans, .. Wheat

Garden City, Kans Fallow

Woodward, Okla _ Wheat 21.3

* From 20 to 40 pounds of nitrogen applied per acre^
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 53

can be grown every year. With increased moisture storage, greater

responses to nitrogen fertilizers could be expected; and it might be

possible to eliminate sununer fallow, which is a source of much wind and

water erosion difficulty and is responsible for great depletion of soil

nitrogen and carbon*

Summary

A study was made of the effect of cropping on the carbon and nitrogen

content of the soil at 14 locations in the Great Plains. The period of

cropping ranged from 30 to 43 years, and the loss of nitrogen varied from

24 to 60 percent. The average of all locations was 39 percent loss of

nitrogen over a 36-year period. Organic carbon losses were similar to

nitrogen losses except that they were sUghtly greater.

Samples were coUected periodically at 4 locations. The results at 3

of these locations in Kansas showed a sharp decline in nitrogen the first

10 to 20 years, with a tendency to level off in the later years. At Sheridan,

Wyo., the decline was almost Unear, with Uttle leveliQg off.

An attempt was made to determine whether one type of small grain

influenced nitrogen or carbon losses more than another. As nearly as

could be determined, there was httle difference in their effect on these

losses.

Land which had been continuously cropped to small grains, or which

had been alternately cropped to small grains and fallow, lost much less

nitrogen than that which had been planted to row crops. Alternate

small-grain and fallow land lost more nitrogen than that continuously

cropped, at every location except one; with row crops, however, the loss

was greater under alternate row crop and fallow than under continuous

row crop, at only 7 out of 13 locations. The average loss from the

surface soil under these cropping treatments at 11 locations was 24

percent for continuous smaU grains, 29 percent for alternate small

grains and fallow, and 43 percent for both continuous row crop and

alternate row crop and fallow. Losses from the subsurface soils were

considerably less than from surface soils.

AppHcations of barnyard manure reduced the loss of nitrogen at all

locations, compared with similar rotations without manure. At 1 location an increase in nitrogen was noted. The average loss at 12 locations

was 37 percent from a rotation without manure and 25 percent from a

rotation receiving manure.

Neither rye nor legumes used as green manure were effective in reducing

the loss of nitrogen.

The effect of grass in a rotation on the loss of soil nitrogen was studied

at 3 locations, and the effect of alfalfa at 4 locations. Both grass and

alfalfa reduced the losses in each instance except alfalfa at 1 location.

Neither grass nor alfaKa maintained the nitrogen at its original level.

The relationship between total nitrogen in the soil and nitrate production during a 6-week incubation period was determined on a total of 214

samples from 13 locations. There was a relationship between total

nitrogen and nitrate production at all but 2 locations. The correlation

coefficient for all samples was 0.562, which was highly sigmficant. In

addition to the 6-week incubation period, 1 high- and 1 low-nitrogen soil

from each location was incubated for 12, 18, and 24 weeks. The high-
54 TECHNICAL BULLETIN 1164, U. S. DEFT. OF AGRICULTURE

nitrogen soils not only produced more nitrate during the first 6-week

period but were able to maintain a higher rate of nitrification during

longer periods of incubation.

The effect of cropping on the total nitrogen content of the soil was

compared with the effect of cropping on nitrate-nitrogen production.

The results varied considerably between locations; but the average loss

of nitrogen was 39 percent, and the average loss in nitrate-nitrogen

producing abihty of the soil was 35 percent.

The type of crop growing on the land immediately prior to time of

sampling had httle effect upon nitrate production. However, there was

evidence in the majority of the samples that those samples from summer

fallow were able to produce less nitrate during incubation than those

from cropped land.

The effect of barnyard manure on the early growth and nitrogen content of wheat plants was determined at 11 locations. Expressed as a

percentage of the checks, the effect of manure on plant weight ranged

from a decrease of 18 percent at Archer, Wyo., to an inciease of 146 percent at Sheridan, Wyo. The effect of manure on the weight of nitrogen in

the plants ranged from 0 at Archer, Wyo., to an increase of 211 percent in

winter wheat at North Platte, Nebr. The effect of manure on the percentage nitrogen in the plants ranged from a 10-percent decrease at Mandan, N. Dak., to an increase of 40 percent at North Platte, Nebr. Increased early growth from the use of manure resulted in increased grain

yields in some instances but not in aU.

An attempt was made to determine the effect of years of cropping or of

the decline in soil nitrogen on crop yields. As nearly as could be determined from data at 6 locations, row-crop yields declined significantly in

some instances while wheat yields did not. Although none of the changes

in wheat yields tested significant, there was evidence that continuous cropping reduced yields more than alternate cropping and fallow, even though

soil nitrogen losses were greater under alternate cropping and fallow. In

some instances, yields from a rotationreceiving manure decUned more than

from a nonmanured rotation, but in general, the decline was not as great,

and in a few instances yields increased. When the percentage changes in

soil nitrogen were compared with the percentage changes in yield, there

was apparently Httle relationship between the two. In some instances

yield changes were greater than the nitrogen changes, while in others, the

reverse was true.

Fertilizer trials conducted during a 3-year period at 13 locations showed

that wheat responded to nitrogen at only 2 of these locations. There were

individual years, however, in which responses were obtained at a few of

the other locations. This indicated the probabihty that in many instances

moistiu-e is still the main limiting fa\;tor.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 55

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1954. THESE SOILS HAVp GROWN WHEAT FOR FIFTY YEARS. What's NeW in

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1942. NITROGEN LOSSES FROM ALABAMA SOILS IN LYSIMETERS AS INFLUENCED

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1937. FERTIOTY LOSSES FROM HIGH PLAINS SOILS DUE TO WIND EROSION.

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1944. STUBBLE MULCH FARMING IN SOUTHERN IDAHO. Idaho AgT. Expt. Sta.

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1937. SOIL AND WATER CONSERVATION INVESTIGATIONS AT THE SOIL CONSERVATION EXPERIMENT STATION, MISSOURI VALLEY LOESS REGION,

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1950. SOIL CONDITIONS & PLANT GROWTH. Ed. 8, 635 pp., illus. London,

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NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 57

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1933. FACTORS AFFECTING THE ACCUMULATION ANB LOSS OF NITROGEN AND

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APPENDIX

TABLE 29.—Nitrogen and carbon content and carbon/nitrogen ratio of

CONTINUOUS SPRING

Plots Crops and tillage treatments Year

started

Number

of plots

Nitrogen at—

Rotation > Oto 6

inches

6 to 12

inches

1914 1943 1914 1943

M. C—--

M. C

A-B__

A-B__

A-B__

Spring wheat—plowed

Oats—^plowed

1914

1914

1914

2

2

2

Pet.

0.178

.142

.212

Pd.

0.142

.114

.179

Pet.

0.138

.108

.158

Pet.

0.142

.108

M. C Barley—plowed... . .162

Average .177 .146 .135 .137

ALTERNATE SPRING

M. 0 C-D..

C-D..

C-D._

Spring wheat, fallow 1914

1914

1914

2

2

2

0.190

.Ißö

.211

0.140

.112

.152

0.147

.118

.154

0.140

.106

.141

M. C Oats, fallow

M. C Barley, fallow

Average .185 .135 .140 .129

CONTINUOUS

M. C A-B__ Com—plowed 1914 2 0.170 0.110 0.130 0.112

ALTERNATE ROW

M. C C-D.. Com, fallow 1914 2

i

0.166 0.100 0.120 0.098

ALTERNATE ROW CROP

40 A-B__

A-B__

Com, oats 1914

1914

2

2

0.142

.144

0.100

.102

0.108

.108

0.092

49 Com, spring wheat _ . _ .098

Average _ .143 .101 .108 .095

ROW CROP, SMALL GRAIN,

2 A-C-_

A-C__

A-C-.

Com, spring wheat, oats

-"-^do'^"------^I-----I-----I--

1914

1914

1914

9

3

3

0.159

.141

.161

0.105

.102

.115

0.118

.102

.119

0.102

.087

.110

3

13

Average .154 .107 .113 .100

ROW CROP (MANURED),

68 A-C Com (manured), spring wheat,

oats.

1914 3 0.144 0.143 0.106 0.116

See footnotes at end of table.
TABLES

the soily under various rotations at Mandan, N. Dak., 1914 ^ and 194S

SMALL GRAIN

Nitrogen at— Carbon at— Ratio of carbon to nitrogen at—

12 to 24

inches

0to6

inches

6 to 12

inches

12 to 24

Inches

0to6

inches

6 to 12

Inches

12 to 24

Inches

1914 1943 1914 1943 1914 1943 1914 1943 1914 1943 1914 1943 1914 1943

Pet.

0.096

.076

.104

Pet.

0.096

.078

.098

Pet.

2.34

1.88

2.76

Pet.

1.82

1.42

2.26

Pet.

1.72

1.36

1.98

Pet.

1.76

1.33

2.07

Pet.

1.18

.91

1.28

Pet.

1.17

.92

1.18

1.09

13.1

13.2

13.0

12.8

12.6

12.6

12.6

12.6

12.6

12.4

12.3

12.8

12.3

12.0

12.3

12.2

11.8

12.0

.092 .091 2.33 1.83 1.69 1.72 L12 13.1 12.6 12.6 12.6 12.2 12.0

SMALL GRAIN AND FALLOW

0.100

.078

.098

0.089

.072

.084

2.48

2.04

2.76

1.77

1.39

1.94

L84

1.48

1.93

1.74

1.32

1.78

1.61

L22

.96

1.20

1.12

1.02

.82

.97

.94

13.1

13.2

13.0

13.1

12.6

12.4

12.8

12.6

12.6

12.6

12.6

12.4

12.5

12.6

12.2

12.2

12.2

11.5

11.4

11.5

.092 .082 2.42 1.70 1.76 12.6 12.6 12.2 11.6

ROW CROP

0.083 0.074 2.24 1 1.64 1.34 1.00 0.87 13.2 12.6 12.6 12.0 12.0 11.8

CROP AND FALLOW

0.076 0.066 2.19 1.23 1.49 1.20 0.91 0.76 13.2 12.3 12.4 12.2 12.0 11.5

AND SMALL GRAIN

0.072

.074

0.066

.074

1.87

1.90

1.88

1.19

1.26

1.22

1.35

1.36

1.36

1.12

1.24

0.86

.89

0.78

.87

13.2

13.2

11.9

12.4

12.5

12.6

12.2

12.7

11.9

12.0

11.8

11.8

.073 .070 1.18 .88 .82 13.2 12.2 12.6 12.4 12.0 11.8

SMALL GRAIN

0.082

.069

.090

0.076

.066

.091

2.09

1.85

2.12

L31

1.23

1.45

1.47

1.28

1.50

1.26

1.08

1.39

0.99

.82

1.09

0.89

.76

1.07

13.1

13.1

13.2

12.5

12.1

12.6

12.5

12.5

12.6

12.4

12.4

12.6

12.1

11.9

12.1

11.9

11.7

11.8

.080 .077 2.02 1.33 L42 1.24 .97 .91 13.1 12.4 12.5 12.5 12.0 11.8

SMALL GRAIN, SMALL GRAIN

0.076 0.081 1.89 1.76 L33 1.45 0.92 0.97 13.1 12.3 12.5 12.5 12.1 12.0

See footnotes at end of table.

59
60 TECHNICAL BULLETIN 1164, tJ. S. DEPT. OF AGRICULTURE

TABLE 29.—Nitrogen and carbon content and carbon/nitrogen ratio of the soil,

FALLOW, SMALL GRAIN,

Plots Crops and tillage treatments Year

started

Number

of plots

Nitrogen at—

Rotation » 0to6

inches

6 to 12

inches

1914 1943 1914 1943

6 A-C

A-0

Fallow, spring wheat, oats

Fallow, oats, spring wheat

1914

1914

-

3

3

Pd.

0.136

.176

Pet.

0.096

.126

Pet.

0.103

.134

Pet.

0.094

8 .121

Average .156 .111 .118 .108

ROW CROP, SMALL GRAIN

19 . -__ A-D Com, spring wheat, fallow,

oats.

1914 4 0.157 0.109 0.120 0.104

ROW CROP, SMALL GRAIN, RYE (GREEN

A-D Com, spring wheat, winter

rye (green-manured), oats.

1914 0.161 0.110 0.119 0.103

ROW CROP, SMALL GRAIN,

31 A-D Com, spring wheat, sweetclover (green-manured), oats.

1914 4 0.145 0.102 0.107 0.098

ROW CROP, SMALL GRAIN, FALLOW

71 A-D Com, spring wheat, fallow

(manured), oats.

1914 4 0.134 0.124 0.099 0.103

ROW CROP, SMALL GRAIN, SMALL

A-F Com, spring wheat, oats, 3

plots grass.

1914 0.149 0.112 0.106 0.100

R(DW CROP, SMALL GRAIN, SMALL GRAIN,

42». - A-F Com, spring wheat,, oats, 3

plots alfalfa.

1914 6 0.164 0.134 0.119 0.122

VIRGIN

(None) Native grasses 15 0.156 0.111

1 Nitrogen and carbon values in 1914 were calculated as described in text.

2The symbol "M. C." means "Methods of ctoppiug."
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 61

under various rotations ai Mandan, N. Dak., 1914 ^ oná 1943—Continued

SMALL GRAIN

Nitrogen at— Carbon at— Ratio of carbon to nitrogen at—

12 to 24

Inches

0to6

Inches

6tol2

inches

12 to 24

Inches

0to6

inches

6tol2

inches

12 to 24

inches

1914 1943 1914 1943 1914 1943 1914 1943 1914 1943 1914 1943 1914 1943

Pet.

0.076

.088

Pet.

0.075

.083

Pet.

1.80

2.31

Pet.

L19

L54

Pet.

1.29

L68

Pet.

1.19

1.48

Pet.

0.90

1.07

Pet.

0.92

.05

13.2

13.1

12.4

12.2

12.6

12.5

12.7

12.2

12.0

12.2

12.3

11.4

.082 .079 2.06 L36 1.48 1.34 .98 .94 13.2 12.3 12.6 12.4 12.1 11.8

FALLOW, SMALL GRAIN

0.086 0.082 2.06 1.37 1.50 L34 1.04 1.01 13.1 12.6 12.6 12.9 12.1 12.3

MANURE), SMALL GRAIN

0.090 0.082 2.12 L36 L50. 1.29 1.10 0.97 13.2 12.4 12.6 12.6 12.2 11.8

LEGUME (GREEN MANURE), Ê MALI GRAIN

0.080 0.078 1.90 1.28 L35 1.21 0.98 0.94 13.1 12.6 12.6 12.3 12.3 12.1

(MANURED), SMALL GRAIN

0.074 0.079 1.77 1.67 1.24 1.30 0.89 0.94 13.2 12.7 12.5 12.6 12.0 11.9

GRAIN. GRASS, GRASS, GRASS

0.077 0.077 1.96 1.40 L33 1.23 0.93 0.96 13.2 12.6 12.5 12.3 12.1 12.5

ALFALFA, ALFALFA, ALFALFA

0.089 0.093 2.16 1.66 1.49 1.64 L08 1.11 13.2 12.3 12.6 12.6 12.1 11.9

SOD

0.081 2.06 1.39 0.98 18,1 12.6 12.1

* Changed to deferred type rotation In 1937.
TABLE 30.—Nitrogen and carbon content and carbonInitrogen ratio of the soil under various rotations at Dickinson, N. Dak., 1947

CONTINUOUS SMALL QRAIN

Plots Crops and tillage treatments

Year

started

Number

of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

Rotation i

Oto 6

Inches

6 to 12

Inches

Oto 6

inches

6 to 12

inches

Oto 6

Inches

6 to 12

inches

M. C A-B___ Spring wheat—plowed 1907

1907

1907

2

2

2

Percent

0.162

.154

.173

Percent

0.116

.114

.132

Percent

1.80

Percent

11.0

M. C A-B Oats—plowed ._ _ _ M. C A-B Barley—plowed

Average .163 .121

ALTERNATE SMALL GRAIN AND FALLOW

M. C C-D Spring wheat, fallow.. .. .. 1907

1907

1907

2

2

2

0.148

.139

.162

0.102

.095

.100

1.62 10.9

M. C C-D Oats, fallow. ' _ M. 0 C-D Barley, fallow., . .. . . .

Average .147 .099

CONTINUOUS ROW CROP

to

H

H

M. C. A-B_ Com—plowed 1907 2 0.120 0.083 1.33 0.92

ALTERNATE ROW CROP AND FALLOW

M. C. C-D_ Com, faUow 1907 2 0.118 0.090 1.28 L04 10.8 11.6

ROW CROP, SMALL GRAIN, SMALL GRAIN

7 _ A-C Com, oats, barley 1907

1907

3

3

0.148

.150

0.115

9_..- A-C Com, oats, spring wheat. _- .111

Average. .149 .113
ROW CROP (MANURED), SMALL GRAIN, SMALL GRAIN

62 A-O Com (manured), spring wheat, oats 1907 a n lAH 0.146 2.08 L66 n.6 11 3

»^ 1 Hrf

S FALLOW, SMALL GRAIN, SMALL GRAIN ä

1 Ö A-C-_ Fallow, spring wheat, oats. . 1907

1907

3

3

0.142

.147

0.100

.103

O

L 8 A-C._ - Fallow^ oats, spring wheat- __ o

«^

Average

ö

.145 .102 î^

hw

en

PEAS (GREEN MANURE), SMALL GRAIN, SMALL GRAIN

61.. A-C Peas (green manure), spring wheat, oats . - 1907 3 0.147 0.105 o

5>

WINTER RYE (GREEN MANURE), SMALL GRAIN, SMALL GRAIN 3o

63 A-0_ __- Winter rye (green manure), spring wheat oats 1907 3 0.163 0.111 ' ^

O

ROW CROP, SMALL GRAIN, WINTER RYE (GREEN MANURE), SMALL GRAIN ^

15 A-D Com, oats, winter rye (green manure), spring wheat 1907 4 0.149 0.111 §

" H

ROW CROP, SMALL GRAIN, LEGUME (GREEN MANURE), SMALL GRAIN ö

16 - A-D _ Com, spring wheat, peas (green manure), oats _ _ 1907

1907

1907

1907

4

4

4

4

0.151

.132

.168

.146

0.118

.092

.111

.106

^

17 A-D Comj oats, peas (green manure), spring wheat

31 - - A-D Com, spring wheat, sweetclover (green manure), oats

Po

32 A-D Com, oats, sweetclover (green manure), spring wheat

g

Average.

g

.149 .106 •d

a

ROW CROP, SMALL GRAIN, SMALL GRAIN, ALFALFA, ALFALFA, ALFALFA >

42 - - A-F Com, oats, spring wheat, alfalfa, alfalfa, alfalfa 1907 6 0.163 0.112 'à

m

VIRGIN SOD O

a

rKonft^ Native grass 9 0.293 0.162 3.64 L87 12.4 11 5

1 The symbol "M. C." means "Methods of cropping." S
TABLE 31.—Nitrogen and carbon content and carhoninitrogen ratio of the soilj under various rotations at HavrCj Mont., 1947

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments Year

started

Number

of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

Oto 6

inches

6 to 12

inches

Oto 6

inches

6 to 12

Inches

Oto 6

inches

6 to 12

Inches

M. 0 A-B Winter wheat—plowed _ 1916

1916

1916

1927

2

2

2

2

0.110

.088

.102

.092

0.108

.087

.096

.088

1.05

.87

.94

.89

0.99

.84

.90

.83

9.6

10.0

9.2

9.7

9.2

M. 0 A-B Spring wheat—plowed 9.6

M. O A-B 0ats—plowed- 9.3

M. 0.« A-B Spring rye—plowed 9.3

Average .098 .096 .94 .89 9.6 9.4

ALTERNATE SMALL GRAIN AND FALLOW

M. 0 C-D Winter wheat, fallow 1916

1916

1916

1927

2

2

2

2

0.098

.088

.092

.087

0.104

.095

.090

.075

0.88

.82

.82

.78

0.94

.90

.79

.68

8.9

9.4

8.9

9.0

9.0

M. 0 O-D Spring wheat, fallow . 9.4

M. 0 C-D_ Oats, fallow- _ _ 8.8

M. 0.« 0-D Spring rye, fallow 9.0

Average .091 .091 .83 .82 9.0 9.0

CONTINUOUS ROW CROP

H3

Î

fei

O)

O

O

M. o., A-B. Com—plowed _ __. 1916 0.076 0.082 0.67 0.72 8.8 8.9

ALTERNATE ROW CROP AND FALLOW

M. C, C-D. Com, fallow 1916 0.071 0.074 0.62 0.65 8.8 8.8

ROW CROP, SMALL GRAIN, SMALL GRAIN

2 A-O Com, spring wheat, oats 1916

1916

1916

3

3

3

0.078

.084

.097

0.081

.086

.090

0.74

.82

.92

0.72

.80

.82

9.5

9.7

9.5

8.9

9 A-O Com, oats, spring wheat _ . _ 9.3

7 A-C Com, oats, barley 9.1

Average .086 .086 .82 .78 9.6 9.1
ROW CROP, SMALL GRAIN, SMALL GRAIN (MANURED)

68 A-0 Com (manured), oats, spring wheat 1916

1916

1916

3

3

3

0.112

.102

.093

0.096

.095

.076

L08

.97

.94

0.89

.86

.72

9.7

9.6

10.1

9.2

9.1

9.4

69 A-0 Com, oats, spring wheat (manured)

70 A-0 Com, oats (manured), spring wheat '

Z

3

Average .102 .089 1.00 .82 9.8 9.2 S

b

FALLOW, SMALL GRAIN, SMALL GRAIN

6 A-0 FaUow, spring wheat, oats 1916

1916

3

3

0.097

.092

0.097

.086

0.90

.85

0.87

.79

9.3

9.3

9.0

9.2 8 A-0 Faiiowi oats, spring wheat

Average .095 .092 .88 .83 9.3 9.1

Ö

P

FALLOW, SMALL GRAIN, WINTER RYE

99» A-0 Fallow, spring wheat, winter rye 1937 3 0.098 0.102 0.89 0.88 9.0 8.7

FALLOW, SMALL GRAIN, WINTER RYE (GREEN MANURE) g

98» A-O Fallow, spring wheat, winter rye (green manure) 1937 3 0.097 0.102 0.86 0.87 8.9 8.5 ^

o

ROW CROP, SMALL GRAIN, FALLOW (MANURED), SMALL GRAIN

71 A-D Com, spring wheat, fallow (manured), oats 1916

1916

4

4

0.106

.121

0.093

.110

1.00

1.16

0.86

.97

9.4

9.6

9.2

8.9

g

72 _. A-D Com, oats, fallow (manured), sorlnir wheat O

Average .114 .101 1.08 .92 9.5 9.1 t^

>

SMALL GRAIN, FALLOW, FALLOW, FALLOW ^

670 A-D Spring wheat, fallow, fallow, fallow 1916 4 0.087 0.091 0.74 0.78 8.6 8.6 ^

[^

VIRGIN SOD QQ

None Native grasses 9 0.151 0.108 1.75 0.99 11.6 9.2 O

1

1 The symbol *'M.

« From 1916 to 192e

» From 1916 to 193(

rotation 16, plots A an<

0." means "Methods of cropping."

1, Inclusive, the area occupied by the M. 0. rye plots was In M. 0. flax plots.

), üicliMlve, the area occupied by rotation 98 was hi rotation 54, plots A. B. and 0. That occupied by rotation 99 was formerly In rotation 54, plot D, and

IB. Both rotations 54 and 16 were 4-plot rotations containing peas plowed under for green manure. • ¿^
TABLE 32.—Nitrogen and carbon content and carbon/nitrogen ratio of the soil under various rotations at Moccasinj Mont., 1947

CONTINUOUS SMALL GRAIN

O

G5

^

H

1^

M. C...

M. C...

M. C—

M. C...

M. C.2_

Average.

Plots

A-B_

A-B_

A-B.

A-BA-B_

Crops and tillage treatments

Winter wheat—plowed.

Spring wheat—plowed--

Oats—plowed

Barley—plowed

Spring rye—plowed

Year

started

1908

1908

1908

1908

1933

Number

of

plots

Nitrogen

at—

0 to 6 inches 0 to 6 inches

Percent

0.200

.212

.223

.229

.232

.219

Carbon

at—

Percent

2.21

Ratio of

carbon to

nitrogen

at—

0 to 6 inches

11.0

ALTERNATE SMALL GRAIN AND FALLOW

M. O...

M. C —

M. C —

M. C —

M. C.i_

Average.

C-D.

C-D.

C-D.

C-D.

C-D_

Winter wheat, fallow..

Spring, wheat, fallow-.

Oats, fallow

Barley, fallow

Spring rye, fallow

1908

1908

1908

1908

0.208

.196

.190

.192

.190

.195

2.17 10.4

O

O

d

ROW CROP, SMALL GRAIN, SMALL GRAIN

Average.

A-C_

A-C.

A-C_

A-C_

Com, spring wheat, oats..

do

Com, oats, spring wheat..

Com, oats, barley

1908

1908

1908

1908

0.193

.205

.209

.206

.203
ROW CROP (MANURED), SMALL GRAIN, SMALL GRAIN

Average.

A-C.

A-C_

Com imanured), oats, spring wheat..

Com (manured), spring wheat, oats_.

1Ô12

1912

0.240

.234

ROW CROP, SMALL GRAIN, SWEETCLOVER (GREEN MANURE), SMALL GRAIN

31» A-D Com, spring wheat, sweetclover (green manure), oats

Com, oats, sweetclover (green manure), spring wheat.

1937

1937

4

4

0.206

.200 328 A-D - 0.215 10 8

Average .203

VIRGIN SOD

None Native grass . 9 0.300 3.24 10 8

1 The sjmibol "M. O." means "Methods of cropping."

2 From 1908 to 1932, Inclusive, these plots were In M. C. flax.

s From 1908 to 1936, tucluslve, the area occupied by rotations 31 and 32 was In rotations 16 and 17 respectively, which contained peas Instead of sweetclover.

O

M
TABLE 33.—Nitrogen and carbon content and carhoninitrogen ratio of the soil under various rotations at Huntley, Mont., 1947

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments Year

started

Number

of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

Oto 6

Inches

6 to 12

Inches

Oto 6

taches

6 to 12

inches

Oto 6

Inches

6 to 12

inches

M. O A-B Winter wheat—plowed _. 1912

1912

1912

1914

1912

2

2

2

2

2

Percent

0.096

.086

.081

.081

.092

Percent

0.091

.084

.084

.062

.095

Percent

0.92

Percent

9.7

M. 0 A-B Spring wheat—plowed ._. _ M. O A-B Oats—plowed.-1_._ ___ _ _

M. 0- A-B Barley—plowed- _.. _._ _ __.

M. 0_- A-B Flax—plowed __

Average .087 .084

ALTERNATE SMALL GRAIN AND FALLOW

M. 0 _ _ C-D Winter wheat, fallow _._ 1912

1912

1912

1914

1912

2

2

2

2

2

0.105

.074

.072

.071

.068

0.092

.076

.066

.048

.072

0.89 9.7 M. 0 O-D SprtDg wheat, fallow _._

M. 0 O-D Oats, fallow. _ _

M. C _ C-D..._ Barley, fallow _ __. __ _.

M. O O-D Flax, fallow ___ _

Average .078 .070

ALTERNATE SMALL GRAIN AND FALLOW (MANURED)

38 - A-B Winter wheat, fallow 1914

1914

2

2

0.122

.110

0.080

.066

1.20 0.76 9.8 9.5 39 A-B Spring wheat, fallow.

Average .116 .072

CONTINUOUS ROW CROP

O

>

O

wH-l

a

d

M. O, A-B- Corn—plowed- 1912 0.070 0.068 0.64 0.63 9.2 to 9.2
ALTERNATE ROW CROP AND FALLOW

M. O ...—„ C5-D Corn.faUow 1912 0.066 0.060

ROW CROP, SMALL GRAIN, RYE (GREEN MANURE), SMALL GRAIN

61 A-D _ Corn, barley, rye (green manure), winter wheat 1912

1912

4

4

0.090

.092

0.096

63 A-D Cor^n', wiTiti^r w'^eat, rye (gr^ftn rnannre), barley .086

Average .91 .091

ROW CROP, SMALL GRAIN, PEAS (GREEN MANURE), SMALL GRAIN

92...^ A-D Com, barley, peas (green manure), winter wheat .- _ 1912

1912

4

4

0.093

.099

0.090

64 A-D Oornj winter wheat7peas (green manure), barley.— .091

Average .096 .090

SMALL GRAIN, FALLOW, FALLOW, FALLOW

to

O

o

fei

§

o

fei

o

fei

m

o

670. A-D Spring wheat, fallow, fallow, fallow.. 1914 4 0.061 0.042

I The symbol "M. O." means "Methods of cropping."
TABLE 34.—Nitrogen and carbon content and carhonjnitrogen ratio of soil from various rotations at Sheridan^ Wyo.y 1917 and 1947

CONTINUOUS PEAS—PLOWED UNDER

Plots Crops and tillage treatments

Number of

plots

Nitrogen at— Carbon at— Ratio of carbon to nitrogen at—

Rotation i 0 to 6% Inches 6^ to 20 inches 0 to QH Inches m to 20 Inches 0 to 69é Inches 6^ to 20 Inches

1917 1947 1917 1947 1917 1947 1917 1947 1917 1947 1917 1947

Continuous. _ _ Peas—plowed under ^. 1

Percent

0.185

Percent

0.134

Percent

0.169

Percent

0.129

Percent

1.99

Percent

1.30

Percent

1.62

Percent

1.32 10.8 9.7 10.2 10.2

CONTINUOUS FALLOW

O

>

1^

Continuous. Fallow.. 0.166 0.095 0.103 0.079 0.94 1.18 0.84 11.2 10.6 H*

CONTINUOUS SMALL GRAIN-PLOWED OR LISTED

M. C.2 A-B

E-F

A-B

E-F

A-B

E-F

A-B

E-F

Spring wheat—plowed . 2

2

2

2

2

2

2

2

0.140

.132

.140

.145

.148

.162

.153

.142

0.111

.109

.112

.113

.116

.124

.112

.112

0.103

.103

.096

.109

.101

.116

.108

.102

0.102

.096

.100

.101

.104

.106

.098

.097

1.50

L34

1.47

1.45

L62

1.74

1.48

L37

L09

LOI

1.10

1.03

L08

L18

1.05

L07

""Ö."98'

"Loi"

"i.'iö"

1.02

.99

0.97

.90

.97

LOI

.98

LIO

.92

.94

10.7

10.2

10.5

10.0

10.9

10.7

9.7

9.6

9.8

9.3

9.8

9.1

9.3

9.5

9.4

9.6

"""9.T

'" "9."5'

""iÖ."3"

9.4

9.7

9.6

M. C

M. C.3

Spring wheat—E subsoiled, F

listed.

Oats—plowed

9.4

9.7

M. C Oats—E subsoüed, F listed

Barley—plowed

10.0

M. C.2 9.4

M. C

M. C

Barley—E subsoUed, F listed.

Winter wheat—plowed _

10.4

9.4

M. C.8 Whiter wheat—E subsoiled, F

listed.

9.7

Average .145 .114 .105 .101 1.50 1.08 .97 10.3 9.6 9.6

CONTINUOUS SMALL GRAINS—ALTERNATE PLOWED AND DISKED

258. A-B

A-B

A-B

Oats and winter whpAt .. 2

2

2

0.167

.164

.172

0.146

.128

.156

0.140

.114

.147

0.135

.106

.145

L86

L63

L79

L60

L31

L58

L46

LIO

L48

L42

L04

L44

n.i

10.6

10.4

ILO

10.2

10.1

10.4

9.6

10.1

10.5

672. _._ Winter wheat 9.8

577 Oats-_. 9.9

Average .164 .143 .134 .128 L76 L60 L35 L30 10.7 10.6 10.1 10.2

d

CD

Ö

O

>

O

to

3

w

Ö
CONTINUOUS SMALL GRAIN PLOWED 1 YEAR, DISKED 2 YEARS

573 A-C

A-C

Winter wheat 3

3

0.150

.169

0.127

.133

0.117

.120

0.109

.116

1.51

1.69

1.28

1.29

L17

1.22

1.11

1.11

10.1

10.6

10.1

9.7

10.0

10.2

10.2

9.7 578 Oats -

Average .156 .130 .118 .112 1.60 L28 1.20 1.11 10.3 9.8 10.2 9.9

OONTINUOUS SMALL GRAIN—DISKED

571 A Winter wheat __ 1

1

0.170

.186

0.156

.160

0.127

.142

0.128

.132

1.87

2.04

1.77

1.71

1.28

1.44

1.25

1.30

11.0

11.0

11.3

10.7

10.1

10.1

9.8

9.8 576 A Oats

Average .178 .158 .134 .130 1.96 1.74 1.36 1.28 n.o 11.0 10.1 9.8

ALTERNATE SPRING SMALL GRAIN AND FALLOW

M.F.*

M. F.*

H-I

J-K-.-_.._

L-M

N-O

C-D

C-D

C-D

Spring wheat—fall-plowed, replowed in spring.

Spring wheat—fall-plowed _

2

2

2

2

2

2

2

0.162

.148

.161

.158

.140

.142

.166

0.096

.098

.097

.106

.102

.106

.113

0.106

.092

,115

.122

.097

.103

.116

0.090

.088

.086

.093

.088

.089

.097

1.62

1.39

1.54

;.45

1.46

1.48

1.67

1.00

.98

1,02

1.12

.93

.98

1.06

0.98

.83

1.08

1.16

0.92

1.02

.91

1.00

.85

.82

.98

10.0

9.4

9.6

9.2

10.4

10.4

10.7

10.4

10.0

10.5

10.6

9.1

9.2

9.4

9.2

9.0

9.4

9.6

10.2

11.6

10.6

10.8

9.7

9.2

10.1

M. F.*

M. F.<

M. 0.»

M. C.8.__

Spring wheat—plowed in May

Spring wheat—plowed in June

Spring wheat—spring-plowed

Oftts—îçpring-plowfid

M. C.2 Barley—spring-plowed. _ _

Average .152 .102 .107 .090 1.52 1.01 .93 10.0 9.9 10.3

ALTERNATE WINTER WHEAT AND FALLOW

W

O

o

o

>

W

O

Q

O

M. C_ C-D. Winter wheat and fallow.. 2 0.140 0.119 0.104 0.100 1.49 1.43 0.93 13.8 9.3

CONTINUOUS ROW CROP

M. C.« A-B______

E-F

Com—plowed _ _ . 2

2

0.144

.145

0.098

.091

0.100

.092

0.092

.081

1.49

1.47

0.91

.84 ""Ö.'87"

0.85

.76

10.3

10.1

9.3

9.2 """9.'5'

9.2 M. C Com—E 9.4 subsoiled, F listed ._

Average .144 .094 .096 .086 1.48 .87 .80 10.3 9.3 9.3

See footnotes at end of table.
TABLE 34.—Nitrogen and carbon content and carbon/nitrogen ratio of soil from various rotations at Sheridan, Wyo., 1917 and 1947—Con,

ALTERNATE ROW CROP AND FALLOW

Plots Crops and tillage treatments

Number of

plots

Nitrogen at— Carbon at— Ratio of carbon to nitrogen at—

Rotation i 0 to 6^ inches 6% to 20 inches 0 to 6% inches 6H to 20 Inches 0 to 6^ inches 6?é to 20 inches

1917 1947 1917 1947 1917 1947 1917 1947 1917 1947 1917 1947

M. C.« 0-D Corn, fallow 2

Percent

0.140

PercerU

0.091

Percent

0.097

Percent

0.084

Percent

1.46

Percent

0.82

Percent Percent

0.77 10.4 9.0 9.2

246-, A-B_

ALTERNATE ROW CROP AND FLAX

243.._ A-B_

A-B

A-B.

Com, flax 2

2

2

0.156

.141

.145

0.112

.100

.111

0.118

.107

.114

0.106

.096

.104

1.64

1.41

1.46

L14

.98

L06

1.28

1.06

1.13

L14

.98

1.02

10.6

10.0

10.1

10.2

9.8

9.6

10.8

9.9

9.9

244 do

- do

10.8

245. 10.2

9.8

Average .148 .108 .113 .102 1..50 1.06 1.15 L05 10.1 9.8 10.2 10.3

ALTERNATE ROW CROP (MANURED) AND FLAX

Com, flax.. 0.143 0.202 0.106 0.105 2.15 1.08 1.10 10.2 10.6

ROW CROP, SMALL GRAIN, SMALL GRAIN

Checks 1-3...

4-6

7-9 <

10-12

13-16.

Com, spring wheat, oats. 3

Do.

Do

Do

Do

do

do

do

do

3

3

3

3

0.134

.153

.161

.147

.174

0.102

.107

.115

.109

.124

0.101

.116

.122

.112

.121

0.094

.097

.107

.102

.107

1.35

1.56

1.70

1.45

1.80

0.95

1.09

1.13

1.05

1.21

1.00

1.20

1.27

1.12

1.21

10.2 10.6

ALTERNATE SMALL GRAIN AND FLAX

247_._ A-B_

A-B

flprlTiff wheat, flax 2

2

0.167

.164

0.134

.127

0.114

.120

0.109

.108

1.83

L72

1.36

1.33

1.19

1.26

1.18

1.18

11.0

10.5

10.1

10.6

10.4

10.5 248 Oats, flax 10.8

10.9

Average .165 .130 .117 .109 1.78 1.34 1.22 1.18 10.8 10.3 10.4 10.8

0.88 10.1 9.3 9.9 9.4

1.01 10.2 10.2 10.3 10.4

1.17 10.6 9.8 10.4 10.9

1.01 9.9 9.6 10.0 9.9

1.06 10.3 0.8 10.0 9.9

fcO

^

Ö

o

w

(=1

ÇQ

Ö

O

d
Do

Do

Do

Do

1

16-18 <

19-21

22-24

25-27*

A-O

A-O

A-O

A-O

A-O

A-O

A-O

A-0_

A-0_

do

do

""IdoIII"!":"!!""!"""""

do

:::::do::i:i"i"iii"iiiiiiii"iii

:""do"ii"iiiiii"iiii-ii"iii"

Oom, barley, oats

3

3

3

3

3

3

3

3

3

3

3

3

3

.168

.163

.183

.166

.172

.186

.175

.158

.171

.183

.189

.165

.159

.118

^126

.136

.122

.133

.131

.127

,113

.129

.123

.144

.123

.116

.122

.129

.147

.105

.109

.125

.127

.113

.124

.122

.146

.116

.101

.107

.124

.130

.102

.111

.112

.115

.100

.101

.108

.123

.103

.097

1.68

1.69

1.90

1.77

1.97

1.93

1.91

1.65

1.86

1.93

2.05

1.72

1.67

1.18

1.32

1.39

1.19

1.31

1.36

1.29

1.10

1.28

1.26

1.37

1.23

1.15

1.25

1.30

1.46

1.03

1.23

1.30

1.44

1.17

""i."3Ö'

1.51

1.24

1.18

1.10

1.23

1.33

.99

1.18

1.20

1.34

1.00

1.02

1.17

1.27

1.09

1.03

10.0

10.4

10.4

10.7

11.5

10.4

10.9

10.4

10.9

10.5

10.8

10.4

10.5

10.0

10.6

10.2

9.8

9.8

10.4

10.2

9.7

9.9

10.2

9.5

10.0

9.9

10.2

10.1

9.9

9.8

11.3

10.4

11.3

10.4

""iÖ."7"

10.3

10.7

11.7

10.3

9.9

10.2

9.7

10.6

2

10.7

3

11.7

4

10.0

13» 10.1

6 10.8

7 Oom, oats, barley 10.3

9 Oom, oats, spring wheat.. 10.6

48- Sorgo, spring'wheat, oats 10.6

Average .167 .122 .120 .108 1.76 1.22 1.12 10.5 10.0 10.4

EOW OROP, SMALL GRAIN, SMALL GRAIN (MANURED)

67 A-O

A-O

A-O

A-O

Oom (manured), oats, spring

wheat.

Oom (manured), spring wheat,

oats.

Oom, spring, wheat (manured),

oats.

Oorn, spring wheat, oats

(manured).

3

3

3

3

0.177

.191

.154

.200

0.196

.188

.176

.196

0.132

.131

.118

.135

0.114

.121

.112

.124

L85

1.93

1.57

2.12

2.05

1.99

1.90

2.09

1.34

1.21

1.45

1.14

1.27

1.17

1.36

10.5

10.1

10.2

10.6

10.5

10.6

10.8

10.7

10.2

10.3

10.7

10.0

68« 10.5

69—

70

10.4

11.0

Average— .181 .189 .129 .118 L87 2.01 1.24 10.3 10.6 ' 10.5

FALLOW, SMALL GRAIN, SMALL GRAIN

5.. A-O

A-O

Fallow, spring wheat, oats

Fallow, oats, spring wheat

3

3

0.178

.162

0.129

.121

0.135

.108

0.116

.097

1.96

1.72

1.32

1.14

L46 1.33

.95

11.0

10.6

10.2

9.4

10.8 11.6

8«-— 9.8

Average .170 .125 .121 .107 L84 1.23 1.14 10.8 9.8 10.7

ROW CROP, SMALL GRAIN, FALLOW, SMALL GRAIN

18—

19«

A-D -

A-D

A-D

A-D..-..-

Com, oats, fallow, spring wheat—

Oom, spring wheat, fallow, oats—

Com, oats, fallow, winter wheatCorn, winter wheat, fallow, oats...

4

4

4

4

0.156

.165

.155

.152

0.124

.118

.120

.121

0.108

.115

.116

.120

0.098

.103

.105

.110

1.58

L80

1.61

L57

L17

Lll

1.22

1.25

1.10

""'ne'

L18

1.02

1.02

L03

1.09

10.1

10.9

10.4

10.3

9.4

9.4

10.2

10.3

10.2

9.8

10.4

9.9

118 9.8

119 9.9

Average .157 .121 .116 .104 1.64 1.19 L04 10.4 9.8 10.0

See footnotes at end of table.

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O

td

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o

CO
TABLE 34.—Nitrogen and carbon content and carbon/nitrogen ratio of soil from various rotations at Sheridan^ Wyo.y 1917 and 1947—Con.

BOW CROP, SMALL GRAIN, RYE (QREEN MANURE), SMALL GRAIN

Plots Crops and tillage treatments

Number of

plots

Nitrogen at— Carbon at— Ratio of carbon to nitrogen at—

Rotation i 0 to 6^ hiches 6^ to 20 inches 0 to 6^é üiches 6% to 20 inches 0 to 6% inches 6^ to 20 hiches

1917 1947 1917 1947 1917 1947 1917 1947 1917 1947 1917 1947

142 A-D

A-D

A-D

A-D

Com, spring wheat, rye (green

manure), oats.

Com. oats, rye (green maTiure),

spring wheat.

Com, winter wheat, rye (green

manm-e), oats.

Com, oats, rye (green manure),

spring wheat.

4

4

4

4

Percent

0.145

.139

.159

.165

Percent

0.110

.111

.130

.136

Percent

0.110

.099

.130

.136

Percent

0.100

.091

.127

.126

Percent

1.47

1.40

1.72

1.76

Percent

1.01

1.06

1.34

1.42

Percent

0.99

1.32

1.36

Percent

0.94

.90

1.28

1.25

10.1

10.1

10.8

1.07

9.2

9.5

10.3

10.4

10.0

10.2

10.0

9.4

9.9

10.1

9.9

16

114

115

Average .152 .122 .119 .111 1.59 1.21 1.09 10.6 9.9 9.8

ROW CROW, SMALL GRAIN, LEGUME (GREEN MANURE), SMALL GRAIN

16 A-D

A-D

A-D

A-D

A-D

A-D

Com, spring wheat, peas (green

manure), oats.

Com, oats, peas (green manure),

spring wheat.

Com, winter wheat, peas (green

manure), oats.

Com, oats, peas (green manure),

winter wheat.

Com, winter wheat, sweetclover

(green manure), oats.

Com, oats, sweetclover (green manure), winter wheat.

4

0.136

.153

.164

.147

.166

.160

0.112

.118

.130

.120

.128

.122

0.107

.112

.126

.115

.114

.110

0.100

.103

.116

.105

.108

.104

1.37

1.56

1.75

1.50

1.72

1.56

0.98

LIO

L29

1.16

L26

L19

L08

L17

LIO

L15

0.94

L07

1.10

LOI

L12

L07

10.1

10.2

10.7

10.2

10.4

10.4

8.8

9.3

9.9

9.7

9.8

9.8

10.1

10.4

9.6

10.5

17

116»

10.4

117

9.5

1313

9.6

10.4

132 _

10.3

Average .153 .122 .114 .106 1.68 L16 L06 10.3 9.6 9.9

H

w

5

d

d

ÇQ

O

>

oh-1 O

d
ROW CROP, SMALL GRAIN, FALLOW (MANURED), SMALL GRAIN

71» A-D

A-D

Com, spring wheat, fallow (manured), oats.

Com, oats, fallow (manured),

spring wheat.

4

4

0.186

.166

0.178

.166

0.127

.110

0.113

.099

1.92

1.73

1.91

1.78 L09

1.14

1.00

10.4

10.4

10.7

10.8 9.9

10.1

72 10.1

Average .176 .172 .119 .106 1.83 1.85 L07 10.6 10.8 10.1

SMALL GRAIN, FALLOW, FALLOW, FALLOW

to

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670* A-D _ Spring wheat, fallow, fallow, fallow- 4 0.148 0.096 0.114 0.084 1.52 1.02 1.20 0.90 10.3 10.6 10.5

ROW CROP, FLAX, SMALL GRALNT, FALLOW, SMALL GRAIN

86- A-E. Com, flax, barley, fallow, whiter

wheat.

0.190 0.136 0.135 0.117 1.39 1.23 10.8 10.3 10.4 10.5

ROW CROP, SMALL GRAIN, SMALL GRAIN, GRASS, GRASS, GRASS

41» A-F

A-F

Com, sprhig wheat, oats, 3 plots

grass.

do

6

6

0.159

.165

0.139

.122

0.118

.119

0.108

.103

1.72

1.76

1.37

1.26 L20

L08

1.12

10.8

10.7

9.9

10.3 10.1

10.0

41-def.» 10.9

Average .162 .131 .119 .106 1.74 1.32 L20 1.10 10.8 10.1 10.1 10.5

ROW CROP, SMALL GRAIN, SMALL GRAIN, ALFALFA, ALFALFA, ALFALFA

42-def.».. A-F_. Com, spring wheat, oats, 3 plots

alfalfa.

0.161 0.132 0.108 0.103 1.71 1.03 10.6 9.6 10.0

1 The symbol "MC." means "Methods of cropphig." The symbol "MF." means "Methods of fallow." The abbreviation "def." signifies "deferred."

3 The 1917 sous of these rotations were analyzed in. BeltsviUe, Md., and the dry-combustion method was used for the determination of carbon. All the other soils were analyzed at Mandan, N. Dak., and the wet-combustion method was used for the determinations of carbons.

8 In 1937 these plots were changed to rotation 11-268, which is a rotation of spring-plowed oats and winter wheat on disked oat stubble.

* Sampled in 1949.

« From 1917 to 1936 hidusive, these plots were in M. C. flax plots A to F. Rotation 41 (deferred) is shnilar to 42 (deferred) except that grass was used instead of alfalfa.

« In 1937 this rotation was changed from the standard rotation in which a given plot is hi alfalfa for 3 years to the deferred type hi which a plot is in alfalfa for 12 years.
TABLE 35.—Nitrogen and carbon content and carbonjnitrogen ratio of the soil under various rotations at Archer, Wyo., 194?

CONTINUOUS SMALL GRAIN

Plots Crops and tillage treatments

Year

started

Num.

ber

of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

Rotation i Oto 6

Inches

6 to 12

inches

Oto 6

Inches

6 to 12

inches

Oto 6

inches

6 to 12

inches

MO A-B Winter wheat—plowea - 1913

1913

1913

1913

1913

2

2

2

2

2

0.088

.097

.086

.094

.086

0.079

.089

.092

.094

.088

0.84

.90

.90

.86

.84

0.72

.78

.87

.84

.82

9.6

9.3

10.5

9.1

9.8

9.1

M 0 E-F Winter wheat—E subsoiled, F listed :

8.8

M G - A-B Spring wheat—plowed _

9.6

M. C'-"I.I

M. C

A-B Oats—plowed 8.9

A-B__ Barley—plowed- 9.3

.090 .089 .87 .81 9.7 9.1

ALTERNATE SMALL GRAIN AND FALLOW

M C 0-D Winter wheat, fallow__ - 1913

1913

1913

1913

2

2

2

2

0.082

.082

.082

.079

0.088

.081

.087

.081

0.80

.78

.76

.72

0.74

.73

.74

.74

9.8

9.5

9.3

9.1

8.4

M C C-D . - Spring wheat, fallow 9.0

M C G-D Oats, fallow 8.5

M. C C-D Barley, fallow 9.1

.081 .084 .76 .74 9.4 8.8

^^"^^

CONTINUOUS ROW CROP

M. 0. (dup.) » M C

A-B Com—plowed..

do

1923

1913

1913

2

2

2

0.075

.068

.073

0.082

.073

.079

0.66

.60

.65

0.68

.63

.71

8.8

8.8

8.9

8.3

A-B 8.6

M. C E-F Com—E subsoiled, F listed 9.0

.072 .078 .64 .67 8.0 8.6

^^^^®

ALTERNATE ROW CROP AND FALLOW

M. C. (dup.) «_ -

M. C

C-D Com, fallow 1923

1913

2

2

0.076

.070

0.080

.078

0.61

.68

0.64

.70

8.1

9.7

8.0

C-D do._ 9.0

.072 .079 .64 .67 8.9 8.5

d

C

>

o

d

tr»

d

to
14.

16.,

7-26..

A-0.

A-C.

A-D.

A-D_

A-D.

ROW CROP, SMALL GRAIN, SMALL GRAIN

2 A-C Com, spring wheat, oats - - - 1913

1913

1913

1913

3

3

3

3

0.077

.086

.074

.084

0.083

.089

.080

.086

0.76

.80

.73

.81

0.78

.75

.76

.80

9.9

9.3

9.9

9.6

9.4

3 A-C do -

8.4

7 A-C Com, oats, barley . -

9.6

9 A-0 Com, oats, spring wheat -

9.3

Av6r&c6 .080 .084 .78 .78 9.7 9.2

ROW CROP—MANURED, SMALL GRAIN, SMALL GRAIN

Com (manured), spring wheat, oats.. 1913 0.099 0.091 0.97 0.81

FALLOW, SMALL GRAIN, SMALL GRAIN

Fallow, oats, sprhig wheat. 1913 0.083 0.085 0.80 0.73

ROW CROP, SMALL GRAIN, RYE (GREEN MANURE), SMALL GRAIN

Com, spring wheat, rye (green manure), oats.. 1913 0.086 0.085 0.80 0.76

ROW CROP, SMALL GRAIN, PEAS (GREEN MANURE), SMALL GRAIN

Com, spring wheat, peas (green manure), oats. 1913 0.082 0.084 0.80 0.77

ROW CROP, POTATOES, BEANS, SMALL GRAIN

Com, potatoes, beans, spring wheat.. 8 1926 0.072 0.079 0.68 0.66

See footnotes at end of table.

9.8

9.6

9.4

9.8

9.4

8.9

8.6

8.9

9.2

ROW CROP, SMALL GRAIN, FALLOW (MANURED), SMALL GRAIN

71 A-D Com, spring wheat, fallow, oats _-- - --- 1913

1913

4

4

0.089

.092

0.088

.088

0.92

.89

0.81

.78

10.3

9.7

9.2

72 A-D Com, oats, fallow, spring wheat..— -- -

8.9

.091 .088 .90 .80 10.0 9.0

8.4

W

O

O

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o

o

fei

CD

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o
TABLE 35.—Nitrogen and carbon content and carbon/nitrogen ratio of the soil under uarious rotations at Archer, Wyo., 19^7 Continued

KOW CROP (MANURED), POTATOES (MANURED), BEANS (MANURED), SMALL GRAIN (MANURED)

42 4_.

None..

Rotation i Plots Crops and tillage treatments

Year

started

Number

of

plots

Nitrogen at— Carbon at- Ratio of carbon

to nitrogen atOto 6

inches

6 to 12

inches

0to6

inches

6 to 12

inches

0to6

inches

6 to 12

inches

18-26 A-D_ - Com (manured), potatoes (manm-ed), beans (manured), spring

wheat (manured),

do

8 1926

8 1926

4

4

0.104

.100

0.080

.089

1.07

1.02

0.69

.80

10.3

10.2 19-26 A-D

8.6

9.0

Average .102 .084 1.04 .76 10.2 8.9

A-F.

A-F.

ROW CROP, SMALL GRAIN, SMALL GRAIN, GRASS, GRASS, GRASS

Com, spring wheat, oats, 3 plots grass. 1913 0.086 0.82 0.80

ROW CROP, SMALL GRAIN, SMALL GRAIN, ALFALFA ALFALFA, ALFALFA

Com, spring wheat, oats, 3 plots alfalfa.. 1913 0.079 0.081 0.76

VIRGIN SOD

Native grasses.. 0.122 1.33 0.83

1 The S3rmbol "M. C." means "Methods of cropping."

« From 1913 to 1922, inclusive, the area occupied by the M. C. com (duplicated plots) was in M C flax

! SiP ^?i? to 1926, inclusive, the area upon which these rotations are located was used for variety tests altemating with faUow

* Changed to deferred type rotation in 1937.

9.6

10.9

9.3

9.4

00

d

— S

05

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TABLE 36.—Nitrogen and carbon content and carhoninitrogen ratio of the soil under various rotations at Akron^ Colo., 1947

CONTINUOUS SPRING SMALL GRAIN

^

§

Plots Crops and tillage treatments Year

started

Number

of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

»p Rotation i

Oto 6

Inches

6 to 12

inches

Oto 6

inches

6 to 12

inches

0to6

inches

6 to 12

inches

<o M. 0_... A-B__ Spring wheat—^plowed _ 1908

1908

1908

2

2

2

Percent

0.092

.099

.100

Percent

0.085

.088

.090

Percent Percent

M. C._ A-B__. ..._ Oats—plowed

M. C_ _. A-B__ Barley—plowed 1.06 10.6

Average _ .097 .088

M. C.

M. O.

M. O.

Average.

C-D.

O-D.

O-D.

ALTERNATE SPRING SMALL GRAIN AND FALLOW

Spring wheat, fallowOats, fallow

Barley, fallow

1908

1908

1908

0.080

.090

.094

0.076

.076

.077

0.90

to

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ALTERNATE WINTER WHEAT AND FALLOW

267 >.. A-B_ Winter wheat, fallow 1924 0.079 0.081

ALTERNATE WINTER WHEAT AND FALLOW (MANURED)

268»..

269«-.

Average.

A-B_

A-B_

Winter wheat on manured fallow

Winter wheat (topdressed with manure), fallow..

1924

1924

0.102

.099

.100

0.096

.092

.094

See footnotes at end of table.

CD
TABLE 36.—Nitrogen and carbon content and carbon/nitrogen ratio of the soil under various rotations at Akronj Colo.j 1947—Continued

CONTINUOUS ROW CROP

Plots Crops and tillage treatments

Year

started

Number

of

plots

Nitrogen at- Carbon at— Ratio of carbon

to nitrogen at—

Rotation i

0to6

inches

6 to 12

inches

0to6

Inches

6 to 12

Inches

0to6

inches

6 to 12

inches

M. O _ A-B Com—plowed- 1908

1908

1908

1922

1922

2

2

1

2

1

Percent

0.066

.067

.070

.068

.079

Percent

0.070

.072

.078

.074

.078

Percent

0.64

.64

.77

Percent

0.62

.66

.68

9.6

9.6

11.0

8.9

M. 0 A-B-_ Kaflr—plowed : 9.2

M. 0 _ F. Kafir—listed . 8.7

M. 0.«__ „_. A-B Sorgo—plowed

M. 0.«__ A'* -. .do.. _

Average .069 .073

AI^TERNATE ROW CROP AND FALLOW

00

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d

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d

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o

d

M. C I C-D.

t

Com, fallow. 1908 0.059 0.070 0.66 0.58 9.3 8.3

ALTERNATE ROW CROP AND SMALL GRAIN

262«.. A-B. Com, winter wheat _ _ 1924 0.086 0.079

ALTERNATE ROW CROP (MANURED), AND SMALL GRAIN

261«.. A-B. Com (manured), winter wheat 1924 0.107 0.086

ROW CROP, SMALL GRAIN, SMALL GRAIN

3 A-C Corrí, spring wbftat, oat«'.. 1908

1908

1908

3

3

3

0.090

.090

.096

0.085

.084

.087

4 _ A-C Corn,'ofttS sp''JTig wbfyit .

6 A-C _._ Corn, barley, oats _ _ _ __ _ _ _

Average .092 .086
FALLOW, SMALL GRAIN, SMALL GRAIN

5 A-0 FftllOW, spring whfiat, nats _____ 1908

1908

3

3

0.089

.083

0.082

R^ A-0 Fallow, oats, spring wheat .076 0.86 0.74 10.2 9.9

Average .086 .078

ROW CROP, SMALL GRAIN, FALLOW, SMALL GRAIN

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A-D Corn, oats, fallow, winter wheat - 1908 0.086 0.080

ROW CROP, SMALL GRAIN, RYE (GREEN MANURE), SMALL GRAIN

61. A-D. Corn, barley, rye (green manure), winter wheat.. 1908 0.084 0.080

ROW CROP, SMALL GRAIN, PEAS (GREEN MANURE), SMALL GRAIN

92-, A-D Corn, barley, peas (green manure), winter wheat 1908 4 0.090 0.084

VIRGIN SOD

None.. Native 9 0.134 0.087 1.42 0.79 10.6 9.1

1 The symbol " M. O." means "Methods of cropping."

» The land on which these rotations were located was continuously or alternately cropped and fallowed from 1908 to 1923, inclusive.

* Sorgo plots were in milo from 1908 to 1921, Inclusive.

* 1 mark (') on a capital letter means 1 replication of the M. C. plot designated by that letter.

00
TABLE 37.—Nitrogen and carbon content and carhonjnitrogen ratio of the 0- to 7'inch depth of soil binder various rotations at Colby, Kans.j

1916 and 1946

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

to nitrogen

1916 1946 1916 1946 1916 1946

M. C A-B -.. Winter wheat 1914

1914

1914

1914

2

2

2

2

Percent

0.159

.110

.122

.140

Percent

0.12

.10

.12

.12

Percent

2.08

1.28

1.18

1.47

Percent

1.28

1.11

1.14

1.18

13.1

11.6

9.7

10.6

10.7

M. 0 _. A-B Spring wheat 11.1

M. C A-B - Oats._ 9.5

M. C .._ A-B _ Barley __ ._ 9.8

Average .132 .12 1.50 1.18 11.4 9.8

ALTERNATE SMALL GRAIN AND FALLOW

M. 0 _ C-D_. Wiîit^r wheat—spritig-plowed _ . . 1914

1914

1914

1914

1914

1914

2

2

2

2

2

2

1

2

2

2

0.148

.167

.165

.168

.165

.161

"""iis"

.116

.118

0.11

.11

.12

.12

.12

.12

.11

.10

.10

.10

1.78

1.63

1.76

1.70

1.81

1.88

'"'i."35"

1.14

1.12

1.07

1.16

1.20

1.28

1.32

1.28

1.00

1.04

.98

.98

12.0

9.8

10.7

10.1

11.0

11.7

"'n.l~

9.8

9.6

9.7

M. F H-I __ Whiter wheat—fall-plowed 10.4

M. F. J-K. _ .do - -_ - 10.0

M. F L-M Winter wheat—^plowed ta May 10.7

M. F N-0.- Winter whi^ftt—plowed in Jiinñ „ 11.0

M. F P-Q Whiter wheat—fall-listed 10.7

267 A Wintfir wheai^—sp^ÍTig-pl^W^íl 9.1

M. C C-D Sprhig wheat—spring-plowed 1914

1914

1914

10.4

M. C ._ C-D Oats—spring-plowed-. _ 9.8

M. C 0-D Barley—spring-plowed ^r. 9.8

Average.. .147 .11 1.57 1.13 10.7 10 3

CONTINUOUS ROW CROP

M. C A-B Com—plowed _ 1914

1914

1914

2

2

2

"o'lu 0.08.08

.09

""i.éí" 0.68

.78

.79

"'"ii.T 8.5

M. C„. A-B .. Kafir—plowed. 9.8

M. C A-B Milo—plowed . 8.8

Average .08 .75 9.4

00to
ALTERNATE ROW CROP AND FALLOW

M, C O-D Oom, fallow 1914

1914

1914

2

2

2

"à'm 0.08

.08

.08

"'i."Î8' 0.69.66

.68

""ii.'ö" M. 0 0-D Kafir, fallow ' "'"

8.6

M.O O-D Mllo, fallow ' "' """

8.2

8.6

Average _..

.08 .68

ROW CROP, SMALL GRAIN, SMALL GRAIN

6 A-0 Com, barley, oats 1914

1914

1914

3

3

3

0.166

.166

.163

0.12

.12

.11

1.90

1.84

2.07

1.16

1.23

1.16

12.2

11.9

13.6

7 A-C Com, oats, barley 9.6

9 A-C Com, oats, spring wheat 10.2

10.4

Average .165 .12 1.94 1.18 12.6 9.8

FALLOW, SMALL GRAIN, SMALL GRAIN—STUBBLE NOT BURNED

8 A-C Fallow, oats, spring wheat 1914 3

3

0.126 0.11

.11

1.33 1.06

.99 668 A-C. 10.6 Fallow, winter wheat, winter wheat 9.6

9.0

Average .11 1.02 9.3 1

FALLOW, SMALL GRAIN, SMALL GRAIN—STUBBLE BURNED

121-1 A-C Fallow, winter wheat, winter wheat 3

3

0.10

.09

0.92

.91 122-2 A-C do 9.2

10.1

Average .10 .92 9.2

FALLOW, SMALL GRAIN, ROW CROP

661 A-C... Fallow, wiQter wheat, mllo 1914

1914

1914

3

3

3

0.130

.118

.137

0.10

.09

.11

1.34

1.18

1.21

0.92

.87

.96

10.3

10.0

8.8

662.... A-C do .. "

9.2

663 A-C do ... .

9.7

8.7

Average .128 .10 1.24 .92 9.7 9.2

See footnote at end of table.

O

O

M

w

o

Î2Î

Ir«

m

o

00

00
TABLE 37.—Nitrogen and carbon content and carbon/nitrogen ratio of the Ö- to 7-inch depth of soil under various rotations at Colby, Kans.,

1916 and 1946—Continued

FALLOW, SMALL GRAIN (TOPDRESSED WITH 3 TONS PER ACRE OP STRAW), ROW CROP

Rotation! Plots Crops and tillage treatments Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

to nitrogen

1916 1946 1916 1946 1916 1946

554 A-0 Fallow, winter wheat plus straw, mllo 1914 3

Percent

0.120

Percent

0.11

Percent

1.25

Percent

1.01 10.4 9.2

FALLOW, SMALL GRAIN, ROW CROP (3 TONS PER ACRE OF MANURE)

566 A-C Fallow, winter wheat (topdressed with manure), mllo 1914

1914

3

3

0.119

.130

0.10

.10

1.28

1.33

0.94

.95

10.8

10.2

9.4

557 A-C Fallow, winter wheat, mUo (manured) 9.5

.125 .10 1.30 .94 10.4 9.4

560-

FALLOW, SMALL GRAIN, ROW CROP (TOPDRESSED WITH 6 TONS PER ACRE OF MANURE)

556- A-O Fallow, winter wheat (manured), mllo 1914

1914

3

3

0.126

.124

0.10

.11

1.28

1.31

0.93

1.01

10.2

10.6

9.3

668 A-C Fallow, winter wheat, milo (manured) 9.2

.124 .10 1.30 .97 10.5 9.7

FALLOW, SMALL GRAIN, ROW CROP (TOP DRESSED WITH 9 TONS PER ACRE OF MANURE)

A-C. Fallow, winter wheat, mllo (manured)- 1914 0.139 0.11 1.37 1.08

FALLOW, SMALL GRAIN, ROW CROP (TOP DRESSED WITH 12 TONS PER ACRE OF MANURE)

A-C. Fallow, winter wheat, mllo (manured). 1914 0.139 0.12 1.37 1.11

9.9 9.8

9.2

00

d

CD

O

H3
ROW CROP, ROW CROP, SMALL GRAIN, RYE (GREEN MANURE)

162 A-D 1914

1914

4

4

0.130

.116

0.09

.10

1.60

1.43

0.86

.94

12.3

12.3

153 A-D 9.6

Average

9.4

.123 .10 L52 .90 12.4 9.0

161.

164.

166.,

166-,

ROW CROP, FALLOW, SMALL GRAIN, RYE (GREEN MANURE)

A-D. Milo, fallow, winter wheat, rye (green manure). 1914 0.124 0.09 0.88

ROW CROP, FALLOW, SMALL GRAIN, PEAS (GREEN MANURE)

A-D. Milo, fallow, winter wheat, peas (green manure). 1914 0.143 0.10 1.64 0.93

ROW CROP, FALLOW, SMALL GRAIN, FALLOW

A-D. Milo, fallow, winter wheat, fallow.. 1914 0.138 0.10 L66 0.98

ROW CROP, FALLOW, SMALL GRAIN, FALLOW (10 TONS PER ACRE OF MANURE)

A-D. Milo, fallow, winter wheat, fallow (manured). 0.147 0.12 1.86 1.16

VIRGIN SOD

Í The symbol "M. O." means "Methods of cropping." The symbol "M. F." means "Methods of fallow.'

10.7

11.6

11.3

12.6

9.8

9.3

9.8

9.7

Weather station Native grass 1

9

10

0.182 0.18

.163

2.00 2.06

1.80 Grid _ do '

11.0 11.4

11.1

Weighted average .166 1.83 11.1

o

o

w

o

QQ

03O

(X)

en
TABLE 38—Nitrogen and carbon content and carbon/nitrogen ratio of the 0- to 7-inch depth of soil under various rotations at Hays, Kans.,

1916 and 1946

M. O..

M. F..

M. F..

M. F..

M. F_.

M. F..

M. C-.

M. C.

Average.

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

to nitrogen

1916 1946 1916 1946 1916 1946

M C A-B Winter wheat—^plowed --- 1906

1906

1913

1916

1916

1916

1916

1916

1916

1906

1906

1906

1906

2

2

2

2

2

2

Percent

0.162

.166

.168

.167

.167

.172

.169

.169

.166

.146

.128

.160

.149

Percent

0.14

.14

.16

.13

.13

.14

.14

.16

.16

.13

.12

.14

.12

Percent

1.88

1.76

1.86

1.96

1.94

1.91

1.91

1.96

1.89

1.78

1.48

1.96

1.82

Percent

1.62

1.42

1.72

1.26

1.36

1.37

1.38

1.62

1.44

1.33

1.16

1.31

1.24

11.6

11.2

11.0

11.7

11.6

11.1

11.3

11.6

n.4

12.3

11.6

13.1

12.2

10.8

M C E-F Winter wheat^-E subsolled, F listed 10.1

691 A Winter wheat—stubbled-in 10.8

606 A Winter wheat—plowed 9.7

606 B Winter wheat—alternately plowed and disked 10.4

606 0 Winter wheat—plowed 1 year, disked 2 years 9.8

606 D - Winter wheat—plowed 1 year, disked 3 years 9.9

606 E Winter wheat—plowed 1 year, disked 4 years — 10.1

606 F Winter wheat—plowed when neœssary 9.6

M O A-B Oats—plowed. 10.2

M O E-F _ Oats—E subsoiled, F listed 9.7

M O A-B Barley—plowed. __

9.4

M. 0 E-F —- Barley—E subsoiled, F listed 10.3

.166 .14 1.83 1.37 11.7 9.8

O-D.

I

K.—

M.__.

o..__

Q...-

C-D.

C-DALTERNATE SMALL GRAIN AND FALLOW

Winter wheat—plowed May 16

Winter wheat—fell-plowed, replowed in spring..

Winter wheat—fall-plowed

Winter wheat—plowed in May

Winter wheat—plowed in June

Winter wheat—fall-listed

Oats—plowed May 16

Barley—plowed May 16

1906

1914

1914

1914

1914

1914

1906

1906

0.146

.149

.161

.166

.164

.168

.120

.120

.142

0.14

.11

.12

.14

.14

.13

.11

.11

.12

1.66

1.72

1.81

1.87

1.90

1.97

1.28

1.64

1.66

1.37

1.04

1.06

1.34

1.40

1.28

1.06

1.12

1.20

11.4

11.6

12.0

12.1

11.6

11.7

10.7

12.8

11.7 10.0

00

ir"

CO

Ö

O

>

O

3
CONTINUOUS ROW CROP

M. CM. O.

M. OM. C.

M. CM. C_

Average.

150-

350-

149..

349-

AverageH-B.

E-F-.

G--_

H-B.

E-F..

Q- —

A-BA-B.

A-BA-BSee footnotes at end of table.

Kafir—plowed _

Kafir—E subsoiled, F listed..

Kafir—lister-planted

Milo—plowed

Milo—E subsoiled, F listed..

Milo—lister-planted .

1910

1910

1910

1910

1910

1910

0.140

.152

.144

.144

.160

.161

.149

0.10

.10

.10

.10

.10

.10

.10

1.64

1.94

1.87

1.78

1.66

1.66

1.76

0.94

1.06

1.00

1.00

1.06

1.08

1.02

ROW CROP, SMALL GRAIN

Com—80-inch rows, winter wheat..

Kafir—80-tnch rows, winter wheat..

Corn—40-inch rows, winter wheatKafir—40-lnch rows, winter wheat..

1916

1915

1916

1916

0.180

.174

.172

.168

.174

0.13

.12

.12

.12

.12

1.96

1.81

2.03

1.98

1.94

1.34

1.14

1.27

1.10

1.21

ROW CROP, SMALL GRAIN, SMALL GRAIN

11.7

12.8

13.0

12.4

10.4

10.3

11.8

10.9

10.4

11.8

n.8

11.2

9.4

10.6

10.0

10.0

10.6

10.8

10.2

ALTERNATE ROW CROP AND FALLOW

M. C C-D _._ Kafir, faUow- 1910

1910

2

2

0.142

.160

0.08

.09

1.72

1.92

0.86

.90

12.1

12.8

10.8

10.0 M. C C-D Mllo.'fallow "

Average .146 .09 L82 .88 12.5 9.8

10.3

9.5

10.6

9.2

10.1

1 A-C ^ Com. sDrine wheat oats 1906

1906

1906

3

3

a

0.143

.149

.164

0.11

.13

.13

1.68

L69

1.70

1.12

1.34

L27

11.0

n.3

n.o

10.2

10.3

9.8

9. A-c : : Com, oats, spring wheat

58 A-C Sorgo, oats, spring wheat

Average .149 .12 1.66 1.24 11,1 10.3

w

o

o

1^

>

öd

o

o

ce

o

¡Xi

o

00
TABLE 38.—Nitrogen and carbon content and carhoninitrogen ratio of the 0- to 7-inch depth of soil under various rotations at Hays, Kans.^

1916 and 1946—Continued

ROW CROP, FALLOW, SMALL GRAIN

Rotation i Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

to nitrogen

1916 1946 1916 1946 1916 1946

601 A-0 Kafir, fallow, winter wheat - 1913

1913

1913

1913

1913

1913

3

3

3

3

3

3

Percent

0.134

.163

.162

.170

.171

.168

Percent

0.10

.12

.11

.11

.11

.11

Percent

1.31

1.72

L78

1.87

L78

L77

Percent

0.97

L16

L13

1.08

1.07

1.08

9.8

10.6

11.0

11.0

10.4

10.6

9.7

502 A-0 do --

9.7

603 A-0 do- -— -

10.3

661 A-C - do -

9.8

662 A-0 - do. 9.7

663 - A-0 - do — - -

9.8

AvBTöCö .161 .11 L71 1.08 10.6 9.8

ROW CROP, FALLOW, SMALL GRAIN (3 TONS PER ACRE OF STRAW)

8g

664- A-0 Kafir, fallow, winter wheat (3 tons per acre of straw) 1913 0.170 0.11 1.76 1.13 10.3 10.3

ROW CROP, FALLOW, SMALL GRAIN (3 TONS PER ACRE OF ]MAI^iURE)

666 A-0 - Kafir, fallow, winter wheat (3 tons per acre manure) -- 1913

1913

3

3

0.174

.174

0.12

.12

L78

1.84

1.14

L14

10.2

10.6

9.6

667 - A-0 Kafir (3 tons per acre of manure) fallow, winter wheat -— 9.6

.174 .12 1.81 1.14 10.4 9.6

ROW CROP, FALLOW, SMALL GRAIN (6 TONS PER ACRE OF MANURE)

656 A-0 - Kafir, fallow, winter wheat (6 tons per acre of manure)-

Kafir (6 tons per acre of manure), fallow, winter wheat. -

1913

1913

3

3

0.179

.177

0.11

.13

L96

1.92

L18

L31

n.o

10.8

10.7

668 -— A-C 10.1

Avera e

.178 .12 1.94 1.24 10.9 10.3 ^^^^^
ROW CROP (9 TONS PER ACRE OF MANURE), FALLOW, SMALL GRAIN

6ß9. A-0- Kafir (9 tons per acre of manure), fellow, winter wheat.. 1913 3 0.177 0.13 1.91 L35 10.8 10.4

Î2I

O

o

td

td

o

Î25

o

tel

00

O

to

IT"

O

00

CD

ROW CROP (12 TONS PER ACRE OF^MANURE), FALLOW, SMALL GRAIN

MO-, A-O. Kafir (12 tons per acre of manure), fallow, winter wheat. 1913 3 0.180 0.14 1.92 1.47 10.7 10.5

ROW CROP, SMALL GRAIN, SMALL GRAIN, SMALL GRAIN

403 -_- A-D Com. barlev. Winter wheat, winter wheat 1916

1916

4

4

0.166

.177

0.12

.13

L84

2.04

L22

L38

11.1

11.5

10.2

10.6 404-._. A-D... Elafir, barley, winter wheat, winter wheat

Average .172 .13 1.94 1.30 11.3 10.0

SMALL GRAIN, FALLOW, FALLOW, FALLOW

570. A-D. Winter wheat, fallow, fallow, fallow 1916 4 0.168 0.11 1.84 1.08 11.0 9.8

ROWÍCROP, SMALL GRAIN, FALLOW, SMALL GRAIN

57. A-D- Com, barley, fallow, winter wheat. 1906 0.147 0.12 1.68 Lll 10.8 9.2

ROW CROP, SMALL GRAIN, RYE (GREEN MANURE), SMALL GRAIN

61 A-D... Com, barley, rye (green manure), winter wheat 1906

1906

1906

4

4

4

0.167

.162

.167

0.14

.14

.13

1.96

2.02

1.82

1.38

1.40

1.33

11.7

12.6

11.6

9.9

10.0

10.2

63 A-D... Com, winter wheat, rye (green nianure), barley

66 - A-D Kafir, barlev. rve (¿een manure), wlntéó* wheat

Average.- .162 .14 1.93 L37 11.9 9.8

ROW CROP, SMALL GRAIN, PEAS (GREEN MANURE), SMALL GRAIN

64 A-D Cnm. wlntfir whiiat. riMu (trrPuPrt TnaTinrftV harlAv 1906

1906

1906

4

4

4

0.162

.162

.155

0.13

.13

.13

1.68

1.79

1.83

1.26

1.22

L27

n.o

11.0

11.8

9.7

9.4

9.8

92 A-D Com, barley, peas (igreen manure), winter wheat

66 - A-D Kafir, barlev. neas (ereen manure), winter wheat

Average .157 .13 1.77 1.26 11.3 9.6

See footnotes at end of table.
TABLE 38.—Nitrogen and carbon content and carbon/nitrogen ratio of the 0- to 7-inch depth oj soil under various rotations at Hays, Kans.,

1916 and iP^Ö—Continued

CO

O

ALTERNATE SMALL GRAIN AND FALLOW

Rotation i Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbo

to nitrogen

1916 1946 1916 1946 1916 1946

M. F H Winter wheat—fall-plowed, replowed In spring 1914

1914

1914

1914

1914

Percent Percent

0.11

.12

.12

. .13

.13

Percent Percent

1.12

1.20

1.25

1.32

1.26

10.2

10.0

10.4

10.2

9.7

M. F J Winter wheat—fall-plowed

M. F L_ .- . Winter wheat—plowed in May

M. F N WlQtiir wheat—plowed in Time

M. F P Winter wheat—fall-listed

Average .12 1.23 10.2

A-D.

SMALL GRAIN—STUBBLE BURNED 2

SMALL GRAIN—STUBBLE NOT BURNED 2

ROW CROP, FALLOW, SMALL GRAIN, SMALL GRAIN 2

Kafir, fallow, winter wheat, winter wheat. 1913 0.11

C15 7 Continuous winter wheat—stubble burned 1919

1919

1919

1

2

2

0.14

.13

.12

1.46

1.42

1.24

10.4

10.9

10.3

C14, C16..- 7 Continuous winter wheat—stubble burned in alternate years..

C9, C13 7 Fallow, winter wheat, wheat on burned stubble, wheat, wheat.

Average .13 1.35 10.3

C15 8 Continuous winter wheat—stubbled-tn 1919

1919

1919

1

2

2

0.14

.13

.12

1.57

1.39

1.23

11.2

10.7

10.2

C14, C16 8 Continuous winter wheat—stubbled-in in alternate years

C9, C13 8 FaUow, wmter wheat, wheat stubbled-hi, wheat, wheat

Average .13 1.36 10.5

9.8

O

>

so

d

d

to
ROW CROP, ROW CROP, FALLOW, SMALL GRAIN i

A-D. Kafir, kafir, fallow, winter wheat.. 1913 0.10 0.96

ROW CROP, FALLOW, SMALL GRAIN a

504 A-0 _ Kafir, fallow, winter wheat 1913

1913

1913

1913

1913

1913

1913

3

3

3

3

3

3

3

0.11 1.08

1.06

1.06

1.05

1.06

1.08

1.14

9 8

506 A-C do 9.5

506 -_- -_-.- A-C do - - . _ _ 9 6

507 A-C do 9.6

508 A-C do 9 6

509 A-C do 9.8

510 A-C do 10 4

Average .11 1.08 9.8

VIRGIN SOD 3

SOD REESTABLISHED IN 1911 »

Fort Hays pasture /Native grass . ._ 1

1

9

0.22

.22

.22

2.64

2.44

2.47

11.6

1 do

Virgin grid do 11.2

Weighted aver- .22 2.47 11.2

age.

o

o

w

o

o

o

>

None _ Native 0.20 1.92 9.6

1 The symbol "M. C." means "Methods of cropping."

3 Plots and rotations not sampled prior to 1946.

The symbol *'M. F." means " Methods of fallow." The symbol ** C" means " Continuous.'

O

O
TABLE 39.—Nitrogen and carbon content and carbon/nitrogen ratio oj the 0- to 7'inch depth of soil under various rotations in the main field

at Garden City, Kans,, 1916 and 1946

CONTINUOUS SMALL GRAINS

Rotation » Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

to nitrogen

1916 ^ 1946 1916 1946 1916 1946

M. C A-B Winter wheat—plowed . 1908

1908

1922

1922

2

2

1

1

Percent

0.110

.100

.094

.093

Percent.

0.10

.09

.08

.09

Percent

1.46

1.14

.96

1.07

Percent

0.90

.78

.72

.78

13.3

11.4

10.2

11.6

9.0

M. O E-F Winter wheat—E subsolled, F listed - 8.7

M. 0.» -, B - Oats—plowed- _ _ 9.0

M. 0.* B _. Barley—plowed __ 8.7

Average. .101 .09 1.20 .81 11.9 9.0

ALTERNATE SMALL GRAIN AND FALLOW

M. 0 C-D Winter wheat—spring-plowed 1908

1913

1913

1913

1913

1913

2

2

2

2

2

2

0.090

.083

.088

.096

.100

.092

0.08

.08

.08

.08

.09

.08

1.16

.84

.90

.99

1.14

1.00

0.74

.68

.72

.82

.84

.73

12.9

10.1

10.2

10.3

11.4

10.9

9.2

M. F H-I Winter wheat—fall-plowed, replowed in spring.^_ 8.Ö

M. F . _ J-K Winter wheat—fall-plowed... ! S...S1 _ 9.0

M. F L-M _.. Winter wheat—plowed in May _._ 10.2

M. F N-0 Winter wheat—plnwfifl In June 9.3

M. F ^ P-Q Winter wheat—fall-listed 9.1

Average .092 .08 1.00 .75 10.9 9.4

CONTINUOUS ROW CROPS

M. O A-B Corn—plowed 1908

1908

1908

1908

1908

1908

1908

1913

1913

1913

2

2

1

2

1

2

1

2

2

2

0.079

.084

.083

.084

.091

.088

.085

.113

.124

.123

0.06

.06

.07

.06

.06

.07

.07

.06

.06

.07

0.88

.74

.73

.77

.88

1.08

.97

1.46

1.54

1.38

0.54

.57

.55

.62

.60

.64

.64

.51

.60

.59

11.1

8.8

8.8

9.2

9.7

12.3

11.4

12.9

12.4

11.2

9.0

M. O E-F Com—E subsolled, F listed 9.5

M. O G Com—lister-planted 7 9

M. 0 A-B _ Kafir—plowed 10.3

M. C F. -

l?^^fl,^_tlgt^(^ _ 10 0

M. O A-B Mllo—plowed - 9.1

M. 0 F. Milo—fisted . _ . . 9 1

S. B_ 1,3 Kafir 8.6

S. B 2,4 do 10.0

S. B 17,18 - Sorgo - 8.4

Average .097 .07 1.08 .58 11.1 8.3

to

^

»

i

O
ALTEENATE ROW CROP AND FALLOW

M. 0 0-D Com—spring-plowed.. 1908 2 O.C 0.06 0.90 0.64 11.0 9.0

ROW CROP, ROW CROP, SUDAN

O

213. A-0. Kafir, mllo Sudangrass.. 1916 3 0.110 0.08 1.12 0.75 10.2 9.4 o

ROW CROP, C0WPEA8, SUDANGRASS

A-C- Kafir, cowpeas, Sudangrass. 3 0.091 0.07 0.99 0.62 10.9 8.9 Ö

a

>

w

o

QQ

02

I

ROW CROP, FALLOW, SMALL GRAIN

405. A-C. Kafir, fallow, "Winter wheat 1913 0.096 0.08 1.11 0.74 11.6 9.2

ROW CROP, FALLOW, SMALL GRAIN, SMALL GRAIN

324. A-D. Kafir, fallow, winter wheat, winter wheat 1913 4 0.098 0.08 1.14 0.78 11.6 9.8

ROW CROP, FALLOW, SMALL GRAIN, SMALL GRAIN, RYE (GREEN MANURE)

331 .. . A-E Kafir, fallow, winter wheat, winter wheat, rye (green manure).

Kafir, fallow, winter wheat, rye (green manure), winter wheat.

1913

1913

5

5

0.099

.108

0.09

.08

1.05

1.22

0.71

.76

10.6

11.3

7.9

332 A-E 9.5

Average .103 .08 1.14 .74 11.1 9.2

CONTINUOUS SMALL GRAIN »

S. B — - 1-2 Winter wheat—plowed _- - 2

2

1

0.09

.08

.09

0.70

.67

.76

7.8

S. B 6-6 do - 8.4

M. C B - Spring wheat—^plowed — 1022 8.4

Average. .09 .70 7.8

See footnotes at end of table.

CO

00
TABLE 39.—Nitrogen and carbon content and carbon/nitrogen ratio of the 0- to 7-inch depth of soil under various rotations in the main field

at Garden City, Kans., 1916 and 1946—Continued

ALTERNATE SMALL GRAIN AND FALLOW »

Rotation i Plots Orops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

tonitrogen

1916 1946 1916 1946 1916 1946

S. ß 3-4- Winter wheat . 2

Percent Percent

0.08

Percent Percent

0.62 7 8

CONTINUOUS ROW CROP

S. B 5-6 Kafir ___ -_ 1913 2 0.07 0.57 8 1

ALTERNATE ROW CROP AND FALLOW (5 TONS PER ACRE OF MANURE) «

CO

p

t*

a

H

Average.

A-B.

A-B.

Milo, fallow (5 tons per acre of manm-e) -

Milo (5 tons per acre of manure), faUow.

1921

1921

0.07

.08

0.54

.60

7.7

7.5

8.1

ROW CROP, COWPEAS «

295 A-B Milo, cowi)eas 1921 2 0.07 0.54 7 7

ROW CROP (MANURED), COWPEAS s

301 A-B Milo (topdressed with mftTinre), cowpeas ... 1921 2 0.07 0.62 8 9

FALLOW, WINTER WHEAT, WINTER WHEAT ON BURNED STUBBLE»

121 . A-C ... Fallow, winter wheat, winter wheat on burned stubble 1921 3 0.07 0.65 9 3

o

o

3
FALLOW, WINTER WHEAT, WINTER WHEAT ON STUBBLE NOT BURNED »..

567 A-C Fallow, winter wheat, winter wheat on stubble not bumed. 1921 0.08 0.70 8.8

o

s

VIRGIN SOD

1, None East fence line Native grass 0.12 1.13 9.4

r

Í The symbol "M. C." means "Methods of cropping." The symbol "M. F." means "Methods of fallow." The symbol "S. B." means "Seedbed.'

2 These plots were In rotation from 1908 to 1921, hiclusive.

3 Plots and rotations not sampled prior to 1946.

O

O

w

o

?d

o

pCO

CO
TABLE 40.—Nitrogen and carbon content and carhotijnitrogen ratio of the 0- to 7-inch depth of soil under various rotations in the annex at

Garden Cityy Kans., 1931 and 1946

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen Carbon Ratio of carbon

tonitrogen

1931 1946 1931 1946 1931 1946

S. S - 1 Winter wheat—stubble burned, plowed.__ ___ _ __- --_ 1931

1931

1931

1931

1931

1

1

2

3

2

Percent

0.150

.149

.137

.134

.133

Percent

0.11

.12

.11

.12

.11

Percent

1.56

1.44

1.44

1.41

1.37

Percent

1.08

1.06

1.07

1.09

1.07

10.4

9.7

10.5

10.5

10.3

9.8

571 A Winter wheat—St ibbled-ln 8.8

S. B 1, 2 Winter wheat—listed 9.7

S B 3, 4, 6 Winter wheat—plowed 9.1

S. B 5, 7 Winter wheat—one-wayed 9.7

Average . .138 .11 1.43 1.08 10.4 9.8

, ALTERNATE SMALL GRAIN AND FALLOW

267 A-B Winter wheat. 1931 2 0.146 0.11 L44 1.00 9.9 9.1

CONTINUOUS ROW CROP

CO

O

>

d

Ö

o

>

s

o

d

d

s.S. 2 Müo—listed - 1931 1 0.141 0.10 1.44 0.90 10.2 9.0

SMALL GRAIN, RYE (GREEN MANURE)

S. S 4 __ Winter wheat, rye (green manure) . 1931 1 0.146 0.11 1.48 1.03 10.1 9.4

SMALL GRAIN, COWPEAS (GREEN MANURE)

S.S. 6 Winter wheat, cowpeas (green manure) 1931 1 0.145 0.11 1.50 0.98 10.3 8.9
FALLOW, SMALL^GRAIN, ROW CROP

s. s 3 Fallow, winter wheat, nillo - - 1931 1 0.136 0.10 1.34 0.87 9.9 8.7

Í2!

FALLOW, SMALL GRAIN, SMALL GRAIN

667 A-0 Fallow, winter wheat, winter wheat 1931 3 0.142 0.11 1.45 LOI 10.2 9.2

o

o

FALLOW, SMALL GRAIN, SMALL GRAIN, SMALL GRAIN

566,..._ ___.._.._ A-D.._ FaUow, winter wheat, winter wheat, winter wheat 1931 4 0.135 0.10 L37 0.97 10.1 9.7

O

VIRGIN SOD •

>

O

N. P Native grass _ _ _ 0.12 - 1.20 10.0

I The symbol "S. S." means "Soil studies." The symbol "S. B." means "Seedbed." The symbol "N. P." means "North pasture."

03

s

CO
TABLE 41.—Nitrogen and carbon content and carbon/nitrogen ratio of soil under various rotations at Woodwardy Okla.y 1947

CONTINUOUS ROW CROP

Rotation i Plots Crops and tillage treatments Year

started

Number of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen at—

Oto 6

Inches

6 to 12

inches

Oto 6

inches

6 to 12

inches

Oto 6

inches

6 to 12

inches

M. 0 A-B Com—plowed 1914

1914

1918

1914

1914

1914

2

2

1

2

2

Percent

0.036

.032

.026

.032

.028

.028

Percent

0.042

.042

.034

.044

.038

.038

Percent

0.38

.34

.25

.34

.30

.30

Percent

0.40

.40

.32

.44

.40

.37

10.6

10.6

9.6

10.6

10.7

10.7

9.6

M. C A-B Mllo—plowed-- --_ 9.5

M. C B'2__ . do - _ . - 9.4

M. C _- A-B Kafir—plowed _. _ 10.0

M. C ._- . A-B Broomeom—plowed-.. . ___ 10.5

M. 0 _- A-B Sorgo—plowed.. _ . 9.7

Average .031 .040 .32 .39 10.3 9.8

CONTINUOUS ROW CROP (MANURED)

M. C T.. Milo (manured).. 1918

1918

1

1

0.035

.042

0.038

.046

0.40

.43

0.37

.49

11.4

10.2

9.7

M. 0 T . Kafir (manured^ 10.6

Average .038 .042 .42 .43 11.0 10.2

ALTERNATE ROW CROP AND FALLOW

M. O C-D Corn, fallow .. .._ _-. 1914

1914

1918

1914

1914

1914

2

2

2

2

2

2

0.028

.024

.025

.026

.028

.022

0.034

.asi

.031

.034

.034

.030

0.26

.24

.26

.27

.32

.23

0.32

.29

.30

.31

.35

.29

9.3

10.0

10.4

10.4

n.4

10.4

9.4

M. C C-D. Mllo, fallow 9.4

297 A-B . do - 9.7

M. C-.._ C-D. Kafir, fallow- 9.1

M. C C-D Broomeom, fallow ._ . 10.3

M. C... C-D-. Sorgo, fallow. _ . 9.7

Average .026 .032 .26 .31 10.0 9.7

ce

OC

>

bd

d

05

d

tel

H

O

>

O

t-H

O

d

%
ROW CROP AND COWPEAS

4^ 28Ö- A-B_ TTftfir, fínwi^iag, . 1918 2 0.022 0.038 0.22 0.36 10.0 9 5

00

a>

1

ROW CROP AND COWPEAS (GREEN MANURE)

cu

286 A-B TTftflr, cowpftiv (grftPTi mannre)...^ . 1918 2 0.028 0.034 0.29 0.34 10.4 10 0 1

1 The symbol "M. C." means "Methods of cropping."

> 1 mark (0 on a capital letter means 1 replication of the M. 0. plot designated by that letter.

W

O

O

>

Ö3

o

îz5

o

GO

O

>

CD

OH-1

CD

CD

CO
Kotation i

261_-.

S.L..

S. L..

S. L..

Average.,

S. L...

S.L..

267.,

268, 269-.

TABLE 42.—Nitrogen content of soil under various rotations at Lawion^ Okla., 1947

CONTINUOUS SMALL GRAIN—PLOWED OR LISTED

Plots

A_..

1,2-.

3, 4_.

9_.-.

7,8_.

10-.

Crops and tillage treatments

Winter wheat, oats

Winter wheat—plowed

Winter wheat—3 deep-plowed, 4 subsolled..

Winter wheat—basin-listed

Year

started

1919

1923

1923

1923

Number

of

plots

CONTINUOUS SMALL GRAIN—DISKED

Winter wheat-. 1923

CONTINUOUS SMALL GRAIN—BASIN-LISTED (MANURED)

Winter wheat (manured)-. 1923

ALTERNATE SMALL GRAIN AND FALLOW

Winter wheat, fallow.. 1919

ALTERNATE SMALL GRAIN AND FALLOW (MANURED)

A Winter wheat, fallow (manured). 1919

Nitrogen at0to6

Inches

Percent

0.080

.082

0.088

0.081

0.078

0.085

6 to 12

inches

Percent

0.086

.090

.082

.079

.085

CONTINUOUS SMALL GRAIN-ALTERNATELY PLOWED AND DISKED

S. L 5, 6 —. Winter wheat- 1923

1923

2

2

0.080

.084

0.080

262 264 ' A Winter wheat; oats or barley .086

.082 .083

0.088

0.084

0.078

0.080

O

o

o

>

IT"

z s

o

>

o

M

o

d
CONTINUOUS ROW CROP

ALTERNATE ROW CROP AND FALLOW

ALTERNATE ROW CROP AND FALLOW (MANURED)

M. 0 A-B Kafir—plowed-_ 1916

1916

2

2

0.059

.058

0.078

M. 0 A-B Feterita—plowed .080

.058 .079

M C C-D - Kafir, fallow. _ __ 1916

1916

1919

2

2

1

0.062

.058

.064

0.080

M. C C-D Feterita, fallow .084

397 A Cotton, fallow .079

.061 .081

o

o

w

o

o

fei

CO

QQ

1

398, 399.. A _ Cotton, fallow (manured). 1919 0.064 0.076

ALTERNATE SMALL GRAIN AND ROW CROP

260* A Winter wheat, cotton. 1923 0.081 0.084

ALTERNATE SMALL GRAIN AND COWPEAS

265-. A - Winter wheat, cowpeas. 1919 0.080 0.091

ALTERNATE SMALL GRAIN AND COWPEAS (GREEN MANURE)

266.. Winter wheat, cowpeas (green manure). 1919 0.082 0.086

ALTERNATE SMALL GRAIN (TOPDRESSED WITH MANURE), COWPEAS

364_. Winter wheat (topdressed with manure), cowpeas. 1919 0.090 0.094

VIRGIN SOD

None - I Native grasses. 0.154 0.103

1 The symbol "M. C." means "Methods of cropping." The symbol "S. L." means "Seedbed plots with winter wheat at Lawton."

« From 1919 to 1922, inclusive, rotation 262 was in alternate com and wheat, and rotation 264 in alternate kafir and wheat.

» From 1919 to 1922, inclusive, rotation 260 was a rotation of wheat, and com and cowpeas In alternate rows.
TABLE 43.—Nitrogen and carbon content and carhoninitrogen ratio of the soil under various rotations at Dalhart, Tex.f 1947

CONTINUOUS EOW CROP

Rotation i Plot Crops and tillage treatments Year

started

Number of

plots

Nitrogen at— Carbon at— Ratio of carbon

to nitrogen

Oto 6^

inches

6% to 12

inches

Oto 6%

inches

6Mtol2

inches

Oto 6%

inches

6^ to 12

inches

M. 0.._. _ - A-B Com fsouth field)—plowed 1908

1914

1908

1908

2

2

2

2

Percent

0.050

.037

.042

.042

Percent

0.052

.051

.048

.052

Percent

0.53

.38

.48

.48

Percent

0.52

.48

.48

.52

10.7

10.3

11.3

11.2

10.0

M. 0 A-B_ ___ Com (north field)—plowed 9.6

M. 0- A-B TTf^fir (south fielfl)—plowed 10.2

M. 0 - A-B Milo (south field)—plowed . 10.2

Average .043 .051 .46 .60 10.9 10.0

ALTERNATE ROW CROP AND FALLOW

M. 0 C-D Com, fallow—-south field __ 1908

1914

1908

1908

2

2

2

2

0.046

.037

.038

.041

0.051

.052

.042

.060

0.48

.34

.42

.44

0.48

.44

.45

.46

10.5

9.4

10.8

10.9

9.4

M. C C-D Com, fallow—^north field 8.4

M. C- C-D Kafir, fellow—south field _._ 10.6

M. C. C-D Milo, fallow—south field . 9.3

Average.. .040 .049 .42 .46 10.4 9.4

ROW CROP, OOWPEÀS, SMALL GRAIN

O

A-C. Com, cowpeas, winter rye—west field 1914 3 0.046 0.047 0.46 0.46 9.9 9.6

ROW CROP (TOPDRESSED WITH MANURE), COWPEAS, SMALL GRAIN

89.. A-0- Com (topdressed with manure), cowpeas, winter rye—west

field.

1914 3 0.062 0.049 0.64 0.49 10.4 10.0

VIRGIN SOD

None I Native grasses. 9 0.067 0.069 0.72 0.60 10.9 10.2

1 The sjonbol "M. C." means "Methods of cropping.*
M. o.

301-

166-

TABLE 44.—Nitrogen percentage oj the soil under various rotations at Big Spring, Tex., 1947

CONTINUOUS SMALL GRAIN

Rotation i Plots Crops and tillage treatments

Year

started

Number of

plots

Nitrogen at—

Oto6

inches

6 to 12

inches

M. 0 - A-B Winter wheat—plowed 1916 2

Percent

0.061

Percent

C-D.

A-B_

A-CSee footnote at end of table.

ALTERNATE SMALL GRAIN AND FALLOW

Winter wheat, iallow..

CONTINUOUS SMALL CROP

ALTERNATE ROW CROP AND FALLOW

1916

ROW CROP (TOPDRESSED WITH MANURE), COWPEAS

Milo topdressed with manure, cowpeas.. 1920

ROW CROP, COWPEAS, SMALL GRAIN

Milo, cowpeas, winter wheat.. 1919

0.060

0.064

0.042

0.054

M. C _ __ A-B Cotton—plowed .. 1916

1916

2

2

0.031

.033

0.044 M. .046 C __ _ A-B Milo—plowed

Average .032 .045

M. C - C-D Cotton, fallow 1916

1916

2

2

0.030

.037

0.043 M. .052 C C-D Milo, iallow - " " "

Average .034 .047

o

O

i2|

0.050 B

m

o

0.044

O

00
TABLE 44.—Nitrogen percentage of the noil under various rotations at Big Spring^ Tex,, 1947—Continued

ROW CROP, FALLOW, FALLOW, FALLOW

Rotation i Plots Crops and tillage treatments

Year

started

Number

of

plots

Nitrogen at—

Oto 6

Inches

6 to 12

Inches

670 A-D -- Milo, fallow, fallow, follow 1916 4

Percera

0.041

Percent

0.046

VIRGIN SOD

O

d

Ö

O

None Native 0.060 0.050

I The symbol "M. C." means "Methods of cropping.'

Ö
TABLE 45.—Percentage of total nitrogen in the 0- to 6-inch depth of soil from different cropping treatments at 9 locations in the Great Plains,

1960; and parts per million of nitrate-nitrogen produced by these soils during a 6-week incubation period

PREVIOUS CROP-ROW CROP

Soil nitrogen and unit

Total nitrogen and nitrate-nitrogen In soil at— Aver,

age at

71ocatlons

Cropping and tillage treatment

Havre HuntleySheridan

Archer NeweU North

Platte

Colby Garden

City

Dalhart

Continuously cropped.- _

/Total nitrogen (percent)

\Nitrate-nltrogen (p. p. m.)

/Total nitrogen (percent)

\Nitrate-nltrogen (p. p. m.)

/Total nitrogen (percent) _

INitrate-nitrogen (p. p. m.)

/Total nitrogen (percent)

\Nitrate-nitrogen (p. p. m.)

/Total nitrogen (percent)

\Nitrate-nitrogen (p. p. m.)

0.076

21.3

.074

23.8

.070

28.3

.073

24.2

.082

33.7

0.076

10.7

.067

10.2

.066

16.6

.064

7.8

.099

23.2

0.100

41.3

.097

33.3

.100

40.6

.086

36.1

.126

40.4

.074

31.8

0.101

14.1

.100

•16.3

.082

11.3

.091

14.7

.102

18.4

0.074

22.6

.072

21.7

.074

20.6

.082

31.7

0.071

16.1

.067

19.0

.063

11.4

.068

9.9

.084

37.9

0.064

69.3

.066

28.2

.069

30.1

.070

62.0

.068

62.9

0.044

11.3

.042

12.6

.043

14.0

.038

10.3

.042

18.4

0.076

Do _ ._

24.9

.073

Alternately cropped and fallowed, cropped plot

20.3

.069

Alternately cropped and followed, fallowed plot

21.7

.070

Rotation of crops __

23.4

.086

32.1

PREVIOUS CROP—SMALL GRAIN

Continuously cropped...

Do

Alternately cropi)ed and fallowed, cropped plot..

Alternately cropi)ed and fallowed, fallowed plot..

Rotation of crops

Native grasses

1 Average of 2 samples.

/Total nitrogen (percent)

INitrate-nitrogen (p. p. m.)

/Total nitrogen (percent)

\Nitrate-nltrogen (p. p. m.)

/Total nitrogen (percent)

\Nitrate-nitrogen (p. p. m.).

/Total nitrogen (percent)

\Nitrate-nitrogen (p. p. m.)

/Total nitrogen (percent).

\Nitrate-nitrogen (p. p. m.)

0.088

33.1

0.088

19.2

0.112

42.2

0.078

46.2

0.117

27.0

0.096

36.4

0.119

44.4

0.098

86.6

0.036

20.9

.092

28.3

.080

21.3

.110

62.6

.081

62.1

.112

19.3

.090

31.0

.108

46.0

.087

44.1

.042

23.0

.083

21.2

.078

17.1

.106

48.3

.083

46.1

.106

19.9

.096

31.8

.099

33.9

.083

61.7

.045

22.8

.091

20.6

.078

16.7

.091

41.1

.091

47.8

.098

19.3

.100

38.9

.082

66.6

.046

28.3

.084

32.3

.100

19.9

.118

39.7

.070

37.2

.104

19.8

.078

26.1

.090

34.7

.066

96.8

.042

20.8

0.094

38.9

.090

33.4

«.7

.084

33.0

37.6

VIRGIN SOD

/Total nitrogen (percent)

\Nltrate-nltrogen (p. p. m.).._.

0.121

39.7

0.171

73.6

0.116

60.1

10.166

149.3

1 0.176

168.8

0.153

42.3

0.068

26.6

0.139
TABLE 46.—Percentage of total nitrogen in 0- to 6-inch depth oj soil from rotation plots at 4 locations in the Great Plains^ 1950; and parts

per million of nitrate-nitrogen produced by the soil during a 6-week incubation period

MOCCASIN, MONT.

Crops » and tillage treatments

When previous crop was—

Rotation i Row crop Small grain Native grasses

Total

nitrogen

Nitratenitrogen

Total

nitrogen

NitratenitrogenTotal

nitrogen

Nitratenitrogen

49- Gam, spring wlifiat

Percent

0.210

.196

.224

.241

.206

.204

.242

.270

P. p. TO.

33.3

36.6

38.4

53.2

42.5

47.1

»53.3

«64.3

Percent

0.204

.191

.219

.225

.208

.201

.228

.222

.180

.196

.192

.202

.226

.194

.197

.192

P. p. m.

35.3

35.4

39.1

49.0

36.7

43.5

*42.4

*44.2

38.1

40.3

29.6

34.9

53.0

39.5

31.1

»35.8

Percent P. p. m.

1 Com, spring wheat, oats__ __

18 Corn, oat«S, fallow, sprlnp wlieat ~

68 Com (manured), spring wheat, oats

15 Com, oats, rye (green rnannre), spring wheat..

32 Com, oats, sweet clover (green manure), spring wheat

41 Com, spring wheat, oats, 3 plots crested wheat

42 CoTTi, spring "wheat, oats, 3 plots alfalfa

Ô4 Winter wheat, oats, rye (green manure)

64 WiTiter whPiat, oats, rye (green manure) _ _

5 Spring wheat, oats, fallow

6 Spring wheat, oats, fallow

M. C CoTitlTi^ious com or spring wheat .179

.156

.136

.142

43.2

27,2

22.3

«23.4

M. C do

M. C._ Alternate com or spring wheat and fallow

M. C . . AlteTTiate c-om, or spring wheat and fallow.

None Virgin sod __ _ ._ . _._ 0.284 44.1
ARKON, OOLO.

252 __ Com, winter wheat 0.077

.087

.083

.104

.079

.086

.086

.086

32.0

26.8

32.9

46.7

32.8

29.6

<26.0

*27.2

0.086

.091

.082

.103

.081

.096

.082

.089

.086

.089

.092

.092

.092

.092

.076

.076

31.7

40.0

30.6

46.7

31.6

36.6

8 31.6

8 29.8

37.2

40.1

36.0

«36.7

39.9

43.7

36.1

«24.3

3 Com, spring wheat, oats

28 ___. Com, oats, fallow, winter wheat . .

261 Corn-manured, winter wheat -_. _

61_ _.._ Com, barley, rye (greeTi TnaTinre), wintfftf w^heat- -

92.. Com, barlfty, peafi (green Tnannre), winter wheat

41 Com, spring wheat, oats, 3 plots grass _

42 .... . Com, spring wheat, oats, 3 plots alfalfa .. _. .

5 Spring wheat, oats, fallow _.

6. Spring wheat, oats, fallow

268.. Winter wheat, fallow (manured)..

268 Winter wheat, fallow (manured) „ ._ __ ._

M. C . Continuous com or spring wheat _ .066

.063

.067

.067

27.1

24.3

24.2

«18.1

M. 0 do.

M. C Alternate com or spring wheat and fallow

M. 0 - Alternate com or spring wheat and fallow

None Virgin sod __ 0.126 38.1

See footnotes at end of table.

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TABLE 46.—Percentage of total nitrogen in 0- to 6~inch depth of soil from rotation plots at 4 locations in the Great Plains^ 1950; and parts

per million of nitrate-nitrogen produced by the soil during a 6-week incubation period—Continued

HAYS, KANS.

Orops > and tillage treatments

When previous crop was—

Kotation ^ Row crop Small grain Native grasses

Total

nitrogen

Nitratenitrogen

Total

nitrogen

Nitratenitrogen

Total

nitrogen

Nitratenitrogen

349« Kafir, winter wheat , . , , .

Percent P. p. 77». PercerU

0.107

.100

P. p. m.

47.7

50.0

Percent P. p. m.

349 0 do .

17 Com, spring wheat, oats _.- Ó.ÍÓ7

.100

.093

.104

.108

.118

.147

.122

.119

.110

.110

33.2

26.5

26.7

24.3

28.7

35.5

39.1

49.9

54.0

4»33.8

* 8^36.3

17 do

651 Kaflr, fallow, wint^erwheat ... .104

.117

.110

.108

.129

.115

.137

.141

.126

.100

.100

.149

.136

.125

.113

41.4

33.6

4a5

35.1

40.7

36.7

67.9

«66.0

»39.9

49.8

»48.9

64.1

59.1

58.6

»44.1

57- Com, barley, fallow, winter wheat _.- __-

403 Com, barley, winter wheat, winter wheat _ _.

558 Kftflr (ft tons TTiannre), fallow, winter wheat

660 Kafir (12 tons manure), fallow, winter wheat

928 MUo, barley, fallow, winter wheat ._ _ ___ _.

518 _. do -

141" Milo, fallow, winter wheat, 3 plot-s gra88

142" Milo, fallow, wint^er wheat, 3 plots alfalfa

570 Winter wheat, fallow, fallow, fallow

570 Winter wheat, fallow, fellow, fallow

M. C nontinnons I'^aflr or spring wheat . , .094

.084

.075

.089

27.0

31.5

28.1

«25.5

M. C do

M. C Alternate Kafir or spring wheat and fallow

M. C . _ A Iternatre kafir or spring wheat and fallow. . .,

None -- -- Virgin sod 0.181 44.4

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BIO SPRING, TEX.

236... Milo, cowpeas— - 0.028

.030

.026

.026

.032

.028

7.6

8.7

10.1

8.6

10.1

9.1

236 - Milo, cowpeas

202 Mllo, cotton, cowpeas . _

202 Milo, cotton, cowi)eas

223 Milo, cowpeas, cotton, fallow. .

223 Mllo, cowpeas, cotton, fallow

164 Winter wheat, winter wheat, cowpeas 0.047

.051

17.7

164 Winter wheat, winter wheat, cowpeas 15.7

205 Milo, cotton, cowpeas (green manure) .026

.027

.050

.041

.032

.030

.023

.022

.026

.025

.024

.026

.026

.028

9.6

8.9

16.7

16.4

8.7

«9.0

9.7

7.6

7.8

«7.6

9.0

8.5

8.1

«7.9

205 Milo, cotton, cowpeas (green mEinure)

273 MUo, cowpeas, cotton, fallow (manured)..

273 MÜO, cowpeas, cotton, fallow (manured)

670 Milo, fallow, fallow, fallow

570 Mllo, fallow, fallow, fallow.

M. C Continuous milo, or winter wheat.. .042

.045

.045

.045

14.7

14.8

15.6

«12.9

M. C do :._

M. C Alternate milo or whiter wheat and fallow

M. 0 Alternate milo or winter wheat and fallow. .

M. C Continuous cotton

M. C. . do _. _

M. C Alternate cotton and fallow. .

M. 0 Alt^rnat-e cotton and fallow

None Virgin sod 0.058 23.8

1 The symbol "M. C." means "Methods of cropping." Rotations which tend to

exert similar effects on soil nitrogen are grouped for comparison.

3 The underscored crop indicates the previous crop.

8 Plot most recently broken from sod.

* Plot farthest removed from sod.

« Plots were in summer fallow prior to sampling.

« This rotation was in effect 1915-45. In 1946 the area was uniformly cropped to

milo, in 1947 fallowed, and in 1948-50 uniformly cropped so winter wheat.

7 This rotation was in effect 1906-45. The area was uniformly cropped to milo la

1946, fallowed in 1947, In winter wheat in 1948, and in mllo 1949-60.

8 The rotation as shown has been in effect since 1946. From 1906-45, the rotation

was com, barley, cowpeas plowed-under for green manure, winter wheat.

» The rotation as shown has been in effect since 1946. From 1906-45, the rotation

was com, barley, winter rye plowed-under for green manure, winter wheat.

" Rotation of milo, fallow, winter wheat, and 12-year-old stands of buffalograss since

1941. From 1906-40, the rotation was com, winter wheat, oats, and 3-year-old stands

of bromegrass.

11 Similar to rotation 141, except that alfalfa was used instead of grass until 1949, at

which time a mixture of blue and side-oats grama replaced the alfalfa.

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lio TECHNICAL BULLETIN 1164, U. S. DEPT. OF AGRICULTURE

TABLE 47.—Average precipitation^ average actual yield per acrey and calculated

yield per acre for the first and last years of period under different cropping treatments at 6 stations

MANDAN, N. DAK. (1915-43)

Crops and tillage treatments

Average

precipitation 1Actual average yield 2

Calculate yield »

First year Last year

Com (grain):

Continuous ^_

Inches

15.31

30.71

16.61

16.61

15.31

30.71

16.61

16.61

15.26

30.65

13.96

13.96

Bushels

27.7

29.2

25.9

24.8

Pounds

2,030

1,990

1,780

2,780

Bushels

13.7

20.9

15.2

17.8

Bushels

34.7

37.9

29.7

30.6

Pounds

2,720

2,790

2,080

2,980

Bushels

12.3

18.6

17.6

16.4

Bushds

25.2

Alternate fallow _ __ _ 26.4

Tiotation without Tnauure . 25.5

Rotation with TTianure... , . , 21.4

Com (stover);

Continuous _

Pounds

1,570

1,470

1,620

2,770

Bushels

16 5

Alternate fallow -

Rotation without manure

Rotation with TTiftTinre -

Wheat (grain):

Continuous -- -

Alternate fallow 24.5

Rotation without manure 15.3

Rotation with manure - _ . __ 24.0

DICKINSON, N. DAK. (1908-47)

Com (grain):

Continuous

Alternate fallow

Rotation without manure.

• Rotation with manure

Com (stover):

Continuous —

Alternate'fallow

Rotation without manure.

Rotation with manure

Wheat (grain):

Continuous

Alternate fallow..

Rotation without manure.

Rotation with manure

Inches

15.98

31.76

17.67

17.67

15.98

31.76

17.67

17.67

15.96

31.79

14.27

14.27

Bushels

19.1

22.1

14.0

16.5

Pounds

3,230

3,530

3,000

4,150

Bushds

11.4

19.8

13.5

17.7

Bushels

30.6

34.7

22.3

23.6

Pounds

4,100

4,010

3,980

4,910

Bushels

15.3

23.3

18.4

21.3

Bushels

21.2

24.1

18.0

23.2

Pounds

3,110

3,620

2,920

4,740

Bushels

11.4

19.1

12.5

20.2

HAVRE, MONT. (1917-47)

Com (grain):

Continuous.

Alternate fallow __

Inches

11.68

23.60

12.82

12.82

11.68

23.60

12.82

12.82

11.63

23.58

10.48

10.48

Bushels

12.2

18.3

10.5

9.9

Pounds

2,080

2,590

1,910

2,180

Bushels

8.1

16.3

11.9

12.5

Bushels

16.2

23.2

13.6

14.6

Pounds

3,010

3,510

2,460

2,830

Bushels

8.3

11.8

12.5

14.9

Bushels

15.6

24.3

Rotat-iOTi withmit Tnamirft , 17.8

Rotation with manure... ....... ..„ . . 13.4

Com (stover):

Continuous

Pounds

1,250

Alternate fallow , _ , 2.910

Rotation without manure 1,450

Rotation with manure 1,670

Wheat (graüi):

Continuous _ - - _ _

Bushels

8.0

Alternate fallow 19.4

Rotation without manure. 10.9

Rotation with manure ^ 9.7

See footnotes at end of table.
NITROGEN AND CARBON CHANGES IN GREAT PLAINS SOILS 111

TABLE 47.—Average precipitcUion, average actual yield per acre, and calculated

yield per acre for the first and last years of period under different cropping treat*

ments ai 6 stations—Continued

SHERIDAN, WYO. (1918^7)

Crops and tillage treatments

Average

precipitation 1Actual average yield 2

Calculated yield «

First year Last year

Com (grain):

Continuous

Altflrn^te fellow

Inches

16.21

32.28

16.98

16.98

16.21

32.28

16.9«

16.98

16.21

32.26

16.44

15.44

Bushels

16.9

19 3

14.5

14.2

Pounds

1,160

1,150

1,220

1,560

Bushels

12.6

24.4

17.9

20.5

Bushels

30.3

29.2

25.8

24.2

Pounds

1,810

1,580

1,840

2,140

Bushels

16.6

25.3

20.4

20.4

Bushels

10.6

15.0

Rotation without manure ._. 7.5

Rotrfttion with TTiftTiure 7.9

Com (stover);

Continuous

Pounds

620

Alternate fallow

Rotation without manure

810

720

Rotrfttion with TTiannrft 1,110

Wheat (grain):

Continuous _ _ _ _

Bushels

10.2

Altemato fallow 24.2

Roti^tion wit.hoTit miinur« 17.8

Rot-at^on with maTiur« . 22.4

ARCHER, WYO. (1914-46)

Com (grahi):

Continuous

Inches

14.48

28.95

17.63

17.63

14.48

28.96

17.63

17.63

14.61

29.13

11.36

11.36

Bushels

13.6

15.7

13.0

11.3

Pounds

1,390

1,470

1,470

1,490

Bushels

7.7

13.1

10.3

10.2

Bushels

19.8

18.6

19.3

15.1

Pounds

2,110

1,940

2,280

2,100

Bushels

10.2

13.1

13.6

14.0

Bushels

11.4

Alternate fallow.. 16 8

RotrfttiOTi without TTiftTiure 11.6

Rotation with manure

Com (stover):

Continuous

11.7

Pounds

770

Altemate fallow

Rotation without TTiRTiure

1,080

780

Rotrfttion with TPflnnre. 990

Wheat (grain):

Continuous - _» _._

Bushels

6.9

Altemate fallow 13.7

Rotation without Tnanure 8.2

Rotation with manure . 7.6

HAYS, KANS (1916-46)

Kafir (grahi):

Continuous __-

Inches

22.02

44.48

29.93

29.93

22.02

44.48

29.93

29.93

22.21

44.71

36.76

36.76

Bushels

15.3

26.7

20.4

20.8

Pounds

3,940

6,780

4,530

4,800

Bushels

14.2

24.1

22.0

19.9

Bushels

21.6

37.3

27.9

24.6

Pounds

6,210

7,130

6,020

4,850

Bushels

19.0

27.0

24.6

23.8

Bushels

13.7

Altemate fallow . _ 27 1

Rotation without riauurfi 23.1

26.3

Kafir (stover):

Continuous -

Pounds

2,610

4,180

3,890

4,670

Bushels

14.6

Altemate fallow

RotftMnn wit.hont manure

Rotation with TTianure....

Wheat (grain):

Continuous „ - >

A Itrftrnatri» fallow .... > 22.2

Rotation without manurfi 22.6

Rotation with manure . „,.. 17.6

Í Precipitation from harvesttime of one crop to harvesttime of next crop.

> Years when hail damafi:e occurrea were omitted.

» Calculated from regression formulas.

K^r

T, PRINTH*«-OFFWfc 1957