AGRICULTURE HANDBOOK NO. 136

'^k estimating tfie amount of

/

CROP

RESIDUE

ON

A

FIELD

UNITED^fATES DEPARTMENT OF AGRICULTURE

AGRICULTURAL RESEARCH SERVICE

in cooperafion with

NEBRASKA AGRICULTURAL EXPERIMENT STATION

Wl'
Contents

Pase

Purpose and scope 3

Maintenance oí residue 3

Factors involved in soil protection 4

Estimatins the amount of residue 5

Oats residue ^

Wheat residue ^

Rye and legume residue /^^

Corn residue 20

Sorghum residue 25

Sweetclover residue ^^

Washington D. C. Issued June 1958

For sale by the Superintendent of Documents, U. S. Government Printing Office

Washington 25, D. C—Price 15 cents
estimating the amount of. . .

CROP RESIDUE ON A FIELD

By F. L. DULEY/ soil conservationist and project supervisor, Soil and

Water Conservation Research Division, Agriculttiral Research Service

Purpose and Scope

This handbook has been prepared primarily for the use of Soil Conservation Service and Agricultural Conservation Program personnel.

It is hoped that many others may also find use for it. Numerous occasions arise when it is important to know how much residue is on a

field, in order to determine how well the land is protected against soil

and water losses. This information may also serve as an aid in checking the efficiency of tillage methods used in a stubble-mulch system of

farming.

Illustrations and accompanying explanations are given in subsequent pages, to show amounts of residue of different types on fields

under different conditions of tillage.

To use this handbook, the reader should find a picture shoAving the

kind of residue to be estimated. He should select one that resembles

the appearance of the field, as nearly as possible. By comparing the

picture with the field he can obtain a reasonably close estimate of the

amount of residue on the land.

Maintenance of Residue

It has been determined by experiments, as well as by the experience

of farmers, that crop residue left on the surface is a means of protecting the land. One way to provide protective residue is by a system

of stubble-mulch farming. Such a system involves the use of implements which do not necessarily invert the soil and do not bury the

residue. In most instances, use is made of sweep-type implements

which loosen the soil by running beneath the surface. These are sometimes called subsurface tillers. Disk-type tools can be used to a

limited extent, but they usually cover too much residue.

Residue cover causes the soil to absorb water more rapidly and thus

reduces the total runoff. It also reduces the amount of soil lost by

either water or wind erosion.

^ Stationed at the Agricultural Experiment Station of the University of Nebraska, Lincoln.
Factors Involved ¡n Soil Protection

The protection afforded a soil by residue depends on a number of

conditions, including the—

Amount of residue on the surface.

Extent to which residue is anchored in the soil.

Length of pieces of residue.

Type of plant from which the residue came.

Extent of decay the residue has undergone.

The amount of residue needed to protect soil varies considerably

with the way it is held in the soil. When approximately 1 ton of

straw per acre is spread over the surface, a fair degree of protection

against erosion by wind or water can be expected. Half that much

straw may be equally effective if it consists of standing stubble. Under the most severe conditions, however, even a ton may not be sufficient. It should be emphasized that the amount of residue by

weight is not as important as the kind of residue and the way it is

anchored in the soil. When the amount is known, however, it is possible to arrive at a quick estimate of the overall protection afforded.

The residue should he anchored in the soil, as this prevents it from

being washed off or blown away. This attachment to the soil may

be through roots or clumps of roots on the stubble. Or residue may

be held in the ground by being partly covered with soil. When the

residue is held in the soil, it cannot be easily detached by either water

or wind. Thus it is much more effective in protecting the soil than is

residue w^hich lies loose on the surface.

The length of the pieces of residue affects the efficiency of the cover.

Straw residue, if broken into short pieces 1 to 3 inches long, may be

light enough to be washed away or blown away. Straw may get into

this condition when (1) shredding machines are used to shorten

straw for the purpose of reducing the clogging of equipment; or (2)

tractors and other machines, passing over the residue, tend to break

it. Working when the straw is very dry also increases the breaking

and shortening of the straw, as compared with working when it is

damp.

The Und of residue—that is, the type of plant from lühich it tvas

obtained—h2iS an important bearing on its durability. Legume residue tends to decay rapidly. It contains high amounts of protein

which supply nitrogen for the organisms that promote decay. However, some parts of legume plants, such as the coarse stems of secondyear sweetclover, may be quite resistant to decay. The coarse parts

of corn or sorghum stalks are quite durable, especially if they are on

top of the soil. When partly buried so that they remain damp for a

considerable time, they may decay rapidly. Wheat and rye straw

are more resistant to decay than is oats straw.
The extent to lohich decay has progressed nnay determine the effectiveness of the cover. As residue decays, it gradually loses its capacity

to cover or protect the soil. In instances where there is more residue

than desired, a certain amount of decay is necessary to reduce the

amount to a point where it is possible to operate machinery through it.

Estimatins the Amount of Residue

The pictures presented in the following pages of this handbook are

intended as a guide in estimating the amount of residue. They illustrate the effectiveness of different amounts and types of residue in

protecting soil against erosion under a variety of conditions. It has

been mentioned before, and should be emphasized again, that the kind

and length of residue and the degree to which it is anchored in the

soil also should be considered, in order to estimate the effectiveness of

the residue in protecting the soil.

For a more exact method of estimating residue, based on simple

calculations which have proved practical, the following procedure

may be used : Make a sampler frame 2.95 feet square ; this has an

area of 1/5000 acre. Take five such samples of residue at random and

combine them to give a sample of 1/1000 acre. Air-dry the material

and weigh it to the nearest one-tenth pound. Divide this weight in

pounds by two, and the result will be the number of tons of residue

per acre.

A little practice in estimating the amounts from the pictures, however, should give estimates that are accurate enough for practical

purposes.
OATS RESIDUE

OATS RESIDUE AND OLD CORNSTALKS

Approximately 1.1 tons per acre of oats straw and 2-year-old cornstalks

in spring will give good cover on sandy land planted to corn, provided this residue is carefully maintained on the surface. (Sandy

Land Experiment Farm, Pierce, Nebr.)
OATS AND SWEETCLOVEE RESIDUE

Oats stubble and first-year sweetclover residue in spring ; total residue,

0.9 ton per acre. This residue is well distributed and gives excellent protection so long as most of it is kept on the surface. If

proper subtillage methods are used, sufficient residue can be retained

to protect the soil against runoff and erosion until the next crop is

well started.
o

DIFFERENT AMOUNTS OF WHEAT EESIDUE PEE ACRE LEFT

ON SURFACE AFTER DIFFERENT DEGREES OF TILLAGE

A, 2.2 tons; B, 1.5 tons; 0,0.37 ton.
WHEAT EESIDUE IN WIND-EKOSION AREA, FALLOWING

Approximately 2.2 tons of combine wheat stubble per acre. This was

worked lightly soon after harvest with a one-way disk to start volunteer wheat and downy bromegrass. The stubble is still standing

well enough to hold snow and prevent erosion by wind or water.

(High plains of western Nebraska.)

453207 O—58-
WHEAT RESIDUE IN WIND-EEOSION AREA, FALLOWING

Approximately 2 tons of residue per acre at beginning of fallow season.

This picture shows the condition on June 26,1956, after 2 subtillage

operations. (High plains of western Nebraska.)

TO
WHEAT KESIDUE IN WIND-EROSION AREA

Only about 1.2 tons of wheat residue per acre, but since some is still

standing, it will catch a certain amount of snow and reduce wind

erosion. This field has had a light disking.

11
WHEAT KESIDUE IN WIND-EEOSION AKEA

Wheat stubble 8 to 10 inches high, approximately 0.5 ton per acre.

While in the condition shown here, the field is fairly well protected

against wind erosion. However, if this field should be tilled by

even the most careful methods, the residue might be too little to

protect the land, especially if the soil is an erosive type. (Hale

County, Tex.)

12
BN-5190

WHEAT SEEDING ON SUMMER FALLOW LAND

Drilling wheat through approximately 1.25 tons per acre of heavy

wheat residue on demonstration field in western Nebraska.

13
WHEAT SEEDING ON SUMMEE FALLOW LAND

Wheat-straw residue on land fallowed with a subsurface tiller. Approximately 0.85 ton per acre of residue still on surface after drilling. This should give a fair degree of protection against wind

erosion, but slightly more residue would be desirable, especially if

the soil is sandy.

14
COKN PLANTING THROUGH WHEAT RESIDUE

Wheat residue, 2.3 tons per acre. The land has been prepared for

corn with subsurface tillers and planted with a disk furrow-opener

planter. This amount of residue should protect the land against

severe runoff and erosion. This field, which is on a 6-percent slope,

has been protected by such treatment over a 12-year period, and

erosion has been negligible. (Near Lincoln, Nebr.)

15
APPEAEANCE OF DIFFEEENT AMOUNTS OF WHEAT STEAW

SPEEAD OV THE SOIL

These pictures give an idea of the visibility of soil through straw when the

amounts per acre are (A) 0.25 ton, (5) 0.5 ton, (6*) 1 ton, and (Z>) 2 tons.

16 17
RYE AND LEGUME RESIDUE

RYE AND PARTRIDGE-PEA RESIDUE ON SAND

Approximately 1.3 tons of residue per acre on sandy land gives good

protection while standing. If care is taken to leave it on the surface, it will protect the soil for the next crop. (Sandy Land

Experiment Farm, Pierce, Nebr. )

18
RYE AND VETCH RESIDUE FOR CORN PLANTING ON

SAND

Approximately 2.5 tons per acre of residue on sandy land. Land was

subtilled and planted to corn with short moldboard lister. This

left plenty of residue on surface between rows to protect soil from

blowing. ( Pierce, Nebr. )

19
CORN RESIDUE

\^ -

f^s^^

-^^J^-

'/-5»ir--

V'^,

>.^^

CORNSTALKS CUT INTO 12-INCH LENGTHS

A^ Plots shown in sprinji with 2 tons per acre of residue; B^ same

plots after 6 months of weathering and cultivation with a subtiller

equipped with wide sweeps. (Near Lincoln, Nebr.)

20
CORN RESIDUE IN FALL, ON ROLLING LAND

Corn residue after husking, approximately 1.8 tons per acre. Much

of this will decay or blow away before planting time in the spring.

If care is taken and the land is subtilled, enough residue should remain on the surface to give fair protection to the land the following

year. (Loess hill region of eastern Nebraska.)

21
CORNSTALK RESIDUE IN SPRING

Approximately 1.5 tons per acre of cornstalks on the surface at time of

planting the land back to corn. Many of the leaves and finer parts

of the plants have been lost during the winter, but there is still

sufficient residue to give effective protection against runoff' and

erosion. (Eastern Nebraska.)

22
HI^H

^ ' '' -v.- '-^ .i'*-^ -'> ~

0- - 4-- ^ "

' - à-. i, - >^ ^-.r / :-^i^ ..

LIGHT COKNSTALK RESIDUE IN SPRING

Land with about 0.75 ton per acre of light cornstalk residue. This

amount should give some protection, but it would not be sufficient if

the land is again planted to corn.

23
CORNSTALKS ON OATS LAND

Approximately 0.5 ton per acre of cornstalk residue. Oats have been

seeded and are coming up. This small amount of residue following

a dry year is too thin and scattered to give effective protection

against erosion.

24
SORGHUM RESIDUE

HEAVY SOKGHUM STALKS IN SPKING

Approximately 2.5 tons per acre of this residue were present in the

fall. The stalks were knocked down by the combine. Leaves have

become largely disintegrated over winter, but the stalks still offer

good protection to the soil. After such stalks are cut in the spring,

they will continue to protect the soil while the next crop is getting

started, provided they are left on the surface by subsurface tillage.

(Near Lincoln, Nebr.)

25
SOKGHUM EESIDUE ON IRRIGATED LAND

Approximately 1.5 tons of residue per acre on irrigated land which

has been one-way disked once. Surface fairly well protected against

wind erosion. If it had not been one-way disked, the field would

have been almost completely protected. Later tillage should be

done with swee{)-type implements, or so much residue will be buried

that much of its protective value will be lost. (Terry County, Tex.)

26
BN-5184

HEGAEI STUBBLE ON lEEIGATED LAND

Irrigated hegari planted in 12-inch rows. Stubble 6 to 7 inches high,

weighing approximately 0.5 ton per acre. This cover will provide

good protection against wind erosion so long as it is not disturbed.

Tillage for the next crop should be done with subsurface tillers, or

so much residue will be lost that the soil will be exposed to severe

wind erosion. Wind tunnel shown is used to measure effectiveness

of stubble. (Lubbock County, Tex. )

27
MILO STUBBLE ON IRRIGATED LAND

Approximately 2.1 tons per acre of milo stubble; some regrowth of

milo and weeds. Soil is heavily crusted and affords excellent protection against wind erosion. At 1 inch above ground, wind velocity

was reduced by 90 percent. ( Lubbock County, Tex. )

28
MILO STUBBLE ON DEY FAEMING AEEA

Approximately 0.43 ton per acre of milo stubble, 10 to 12 inches high.

Surface is somewhat ridged and crusted. The soil is fairly well

protected against wind erosion while this stubble is undisturbed.

Not enough residue is present to protect the soil after it is tilled for

the next crop. However, it will give some protection if care is

taken to maintain as much as possible on the surface by subsurface

tillage. (Lubbock County, Tex.)

29
SWEETCLOVER RESIDUE

SWEETCLOVEE RESIDUE, CROP HARVESTED FOR SEED

Approximately 2.5 tons of residue per acre. This combination of high

stubble and straw gives very effective protection against runoff' and

erosion. It is highly efficient in holding snow. Next year's crop

is likely to have plenty of moisture and available nitrogen. (Eastern Nebraska.)

' See also OATS AND SWEETCLOVER RESIDUE, p. 7.

30
BN-6185

MOWED SWî:ETCLOVER, FLAT ON GROUND

Approximately 3 tons of second-year sweetclover residue which has

been mowed and flattened by weather. This type of residue gives

almost perfect protection against runoff and erosion, but it will not

stop blowing snow.

U. S. GOVERNMENT PRINTING OFFICE: 1958 O—453207

31