United States

Department of

\“/ Agiiculture

Forest Service h1

Southern Forest

Experiment Station

The Nutrient Pool of Five Important

Bottomland Hardwood Soils

John K. Francis

SO-327

September 1988

SUMMARY

Heretofore, with the exception of N, the concentration

of total nutrients and the amount of variation in nutrient

concentrations among and within soil series and depths

within the rooting zone of forested alluvial soils of the

South was unknown. Information about total nutrient

concentrations is important in studying the danger of

nutrient depletion posed by total tree harvest and other

forms of intensive management. In this study, five important alluvial forest soils were sampled on each of five

sites, and the samples were analyzed for total N, P, K,

Mg, and Ca. Available nutrient levels were determined

as well. Soil series was a significant source of variation

for all nutrients (p = 0.95). Nutrient concentration varied

significantly among sites within soil series in most cases.

Total N, P, and Mg also varied by depth. The available

nutrient concentrations of all five nutrients were significantly correlated with their respective total nutrient concentrations. These alluvial soils are high in nutrients;

potassium content is particularly high (8-19 g/kg). Nutrient depletion resulting from withdrawals of nutrients in

whole-tree harvests will not occur for several rotations in

the soils tested. However, to reduce the risk of depletion

of sites with unexpectedly low nutrient reserves, the soil

should be tested, and when needed, maintenance fertilizer should be applied or less intensive harvests prescribed.

Keywords: total nutrients, available nutrients, alluvial

soils, nutrient depletion, soil series.

INTRODUCTION

Whole-tree chipping and other forms of intensive harvest remove considerable quantities of nutrients from

forest sites (Hornbeck and Kropelin 1982). Destruction

of the vegetative cover and disturbance of the soil surface may temporarily accelerate nutrient loss in runoff

and percolating waters (Vitousek and Reiners 1975).

The question “Will intensive harvests and disturbance of

bottomland hardwood sites deplete their soils of essential nutrients?” needs to be answered. To do so, we not

only need information on nutrient concentration in runoff

water and estimates of harvest withdrawals, we must

also document nutrient reserves in bottomland sites.

Nutrient reserves can be classified into two forms,

available (or exchangeable) and fixed. The trees accumulate their nutrient load from the available pool of nutrients. The available pool is in equilibrium with and can be

slowly recharged from the insoluble or fixed pool. The

nutrient depletion question cannot be fully answered unless the content of total nutrients is known. Analyses of

available nutrient concentrations in a number of forested

alluvial soils of the South have been published (Broadfoot 1978). Of the total nutrient reserve (available plus

fixed forms), only N was documented. Base-line data for

detection of changes in total nutrient reserves over time

and disturbance did not exist.

This study was undertaken to measure the total nutrient reserves of five important bottomland forest soils.

Each soil represented a distinct environment so that the

study would represent as much of the bottomland hardwood ecosystem of the South as possible. The variation

within and among sites and between depths was tested,

and total nutrient concentrations were related to available nutrient levels.

MATERIALS AND METHODS

All the soils sampled are alluvial and covered with

timber; old-field sites were not considered. Three of the

soils were deposited by the Mississippi River: the Alligator series (very fine, montmorillonitic, acid, thermic Vertic

Haplaquepts) is a clay; the Bruno series (sandy, mixed,

Southern Forest Experiment StationTT-10210 U.S. Postal Services Bldg., 701 Loyoia Avenue, New Orleans, La. 7Oll3

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin islands

1
thermic Typic Udifluvents) is a loamy sand; and the

Commerce series (fine-silty, mixed, nonacid, thermic

Aeric Fluvaquents) is medium textured. The Falaya

series (coarse-silty, mixed, acid, thermic Aeric Fluvaquents) is a silt or silt loam on flood plains of streams

in the Silty Uplands. The Mantachie series (fine-loamy,

siliceous, acid, thermic Aeric Fluvaquents) is a mediumtextured soil of the Coastal Plain. A soil was identified in

the field by establishing its soil taxinomic classification

and then matching it with the appropriate series description. Samples of these soils were collected in early summer in portions of Mississippi, Arkansas, and Louisiana.

Each series was represented by five forested sites

located at least 8 km apart. At each site, three locations

spaced 30 m apart were chosen for sampling. At each

location, two auger holes were bored 3 m apart and the

soil in each collected from depths of O-30.5 cm and

30.5-81 cm. This resulted in a total of 300 soil samples,

which were air-dried and sieved (2 mm).

All samples were analyzed for total N, P, K, Mg, and

Ca. Total N was determined by the standard Kjeldahl

procedure (Bremner and Mulvaney 1982). Total P was

determined by a NaOH fusion technique described by

Smith and Bain (1982). Potassium, Mg, and Ca were

measured by atomic absorption spectroscopy (AAS)

from the NaOH-fused sample from the total P procedure

after dilution and acidification. Commercially available

reference soils were employed as standards.

Because of limitations of time and expense, available

nutrient concentrations were determined for only the

samples from the upper 30.5cm depth. Available N

(principally inorganic) was extracted from soil samples

with acidified NaCI, the N03- being converted to NH4+

through the use of Davarda’s alloy according to a procedure described by Jackson (1958). Available P was determined with a procedure involving two-stage dilute HCI

and acidic acid extraction (Soil Test Work Group 1974).

Exchangeable K, Mg, and Ca were extracted with 1 N

NH40Ac and measured by AAS.

To help direct future sampling and potentially nutrientdepleting harvest activities, sources of variation of total

nutrients in these alluvial soils were evaluated by the

analysis of variance technique (p = 0.95). Split-plot and

nested arrangements were used. When tests proved significant, soil depths and means of nutrient concentrations for soil series were compared by Duncan’s New

Multiple Range test. In addition, the relationships between available and total nutrient concentrations in the

upper 30.5 cm were related by linear regression.

RESULTS

The average total nutrient concentration in the five soil

series for O-30.5 cm and 30.5-61 cm are listed in table

1. The concentrations varied from more that 1 percent K

to less than 0.1 percent P. An approximate total nutrient

content per hectare for the upper 61 cm of soil can be

obtained by multiplying total nutrient concentration by

8.966 million kilograms, an average figure of soil weight

per hectare (Buckman and Brady 1960). Averages for

each soil and nutrient are presented in table 2.

Soil series was a significant source of variation for all

five nutrients. In table 2, multiple comparisons of means

indicate significant ranking according to concentration in

the soil. The series were generally ranked in order of

decreasing concentration: Alligator, Commerce, Bruno,

Falaya, and Mantachie. The three Mississippi River alluvial soils, Alligator, Commerce, and Bruno, usually had

greater concentrations than upland and coastal plain

Table 1 .-Average total nutrient concantrations in five soil series at two depths

Nutrient Depth Alligator Bruno Commerce Falaya Mantachie

C m ____________________________ Gpefkg ____________________________

N O-30.5 2.18~0.50* 0.s3-co.34 0.94-cO.16 0.6720.26 0.65kO.22

30.5-61 1.6O-co.47 0.2420.15 0.65kO.25 0.5620.16 0.44+0.11

P O-30.5 0.83*0.09 0.61kO.10 0.72kO.07 0.41kO.12 0.31*0.05

30.5-61 0.7420.09 0.54-co.06 0.6920.07 038~0.11 0.28-cO.08

K O-30.5 19.05kO.68 16.66r1.02 16.35kO.62 11.6923.26 6.03k2.25

30.5-61 16.97kO.66 16.68+0.79 16.54kO.79 11.26+3.03 6.22k2.42

Ca O-30.5 6.37~060 a.74+1.48 7.6721.15 1.48k0.76 0.732030

30.5-61 6.23kO.50 10.08+1.16 6.17k1.65 1.21+0.63 0.75kO.62

Mg O-30.5 10.51kO.85 4.89k1.47 66620.23 2.03kO.77 1.81kO.62

30.5-61 10.96kO.81 5.6121.10 7.1620.85 1.91k0.68 2.1920.85

'Meanzstandard deviation.

John K. Francis is Principal Soil Scientist, Institute of Tropical Forestry, Forest Service-USDA, Rio Ptedras, P.R. 00928.

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Table 2.-Approximate weights of total nutrients in the upper 61 cm in five soil

series *

Nutrient

N 16.la 4.6b 7.lb 6.4b 5.6b 0.0297

P 7.la 5.2b 6.3a 3.6c 2.7~ 0.0065

K 170.5a 150&l 165.3a 102.9b 72.9b 6.0299

C a 57.4c 84.4a 72.0b 12.ld 6.6d 1.0645

Mg 96.3a 47.lb 62.0a 17.7c 17.9c 1.0801

*Means within a row followed by the same letter are not significantly different at the

0.05 level.

EMS = Error mean square.

Table 3.-Comparison of means of total nutrient concentrations by

depth l

Nutrient

Depth

O-30.5 cm 30.5-61 cm

__________ Gperkg _________

EMS

N O.llla 0.070b 0.00087

P 0.058a 0.053b o.OfIOO3

K 1.48Oa 1.473a 0.00143

C a 0.508a 0.529a 0.00469

Mg 0.518b 0.557a 0.00139

*Means within a row followed by the same letter are not significantly

different at the 0.05 level.

EMS = error mean square.

alluvial soils. Concentrations of total nutrient by depth

averaged across the five soil series are given in table 3.

Depth was significant for N, P, and Mg but insignificant

for K and Ca. Although N, P, and Mg differed significantly

by depth, the difference in concentration by depth was

large (63 percent) for N only. There were no significant

series x depth interactions.

nutrient concentrations on available nutrient concentrations and their square yielded coefficients of multiple

determination (R2) values ranging from 0.28 for N to 0.88

for Mg (table 5). Thus total nutrient levels for these soils

may be predicted from available nutrient concentrations

if no other means is available.

Sampling site was a significant source of variation in

most of the series-nutrient combinations. This indicates

significant variation in total nutrient concentrations within

most soil series. As would be expected, there was less

variation within sites than between them-more than

half the F tests for location within site were not significant.

DISCUSSION AND CONCLUSIONS

In table 4, mean available nutrient concentrations of

the five elements are presented and compared. Available nutrients varied significantly among soil series. In

general, the series were ranked as they were for total

nutrient levels. Available nutrient supply varied from

about 1 percent of the total N in the soil to about 80

percent of the total Ca. Approximate available nutrient

weight as kilograms per hectare (30.5 cm layer) may be

obtained by multiplying the numeric value of available

nutrient concentration by 4.48. It varied from 38 to 66

kilograms of N per hectare to 2 to 24 thousands of kilograms of Ca per hectare.

Massive amounts of K, Ca, and Mg were present in all

the soil samples analyzed. Substantial amounts of N and

P were also present. Soils deposited by the Mississippi

River were higher in K, Ca, and Mg than the Coastal

Plain or Silty Upland alluvial soils. This did not always

hold true for N and P. Despite its loamy sand texture,

Bruno soil contained surprising amounts of total nutrients. This may be a result of periodic flooding by the

mildly alkaline waters of the Mississippi River. There

were not only differences in total nutrients among soil

series, but also considerable differences among sites

within the same series. This, no doubt, reflects the extreme variability of the alluvial deposits layed down by

the river over the years. Liberal sampling of these alluvial

soils is indicated to assure accurate conclusions about

nutrient properties.

The five total nutrient concentrations were significantly Depth was not as important as expected. Concentracorrelated with their respective avaiiable nutrient con- tions of K and Ca were not different between depths.

centrations in the upper 30.5 cm of soil. Regressing total Although total P and Mg concentrations at both depths

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Table 4.-Comparison of means of available nutrient concentrations by soil series’

Nutrient Alligator Bruno Commerce Falaya Mantachie EMS

___________________________Gpermg ___________________________

N 14.84a 8.44b 10.62ab 13.08ab 9.60b 10.6

P 49.3a 49.9a 60.9a 16.3b 11.7b 210.0

K 402.5a 143.2c 223.2b 58.44 46.44 2953

C a 5246a 1669c 3254b 506d 404d 246765

Mg 1302a 306c 656b 163c 153c 26662

‘Means within a row followed by the same letter are not significantly different at the

0.05 level.

EMS = error mean square.

Table 5.--Regression of total nutrient levels (lJ on available nutrient levels (A) for

the five nutrients tested in the upper 30.5 cm of soil

Nutrient Equation* R2 C V

N T = 0.2892 + 0.07062A + 0.0003029A2 0.2622

P T = 0.19660 + 0.014491A + 0.0008728A2 0.7668

K T = 7.4570 + 0.07263A + 0.0001036A2 0.7075

Mg T = 1.3097 + 0.0086OOA + 0.000001A2 0.6760

C a T = 0.7023 + 0.003966A + 0.0000005A2 0.5974

*Values for T and A are g/kg of nutrient in the upper 30.5 cm of soil.

44.71

17.46

17.26

23.58

42.86

were significantly different, the actual magnitude of the

difference was small and probably unimportant. Total N

was considerably more concentrated in the upper 30.5

cm than in the lower 30.5 cm. This was a result, no

doubt, of a higher concentration of organic matter and of

fixation and cycling in the more biologically active surface 30.5 cm. Leaching seems to have done little to

stratify these recent alluvial soils. The loss of surface

layers of soil by erosion or scalping may not carry such

long-term nutrient effects as in more weathered soils.

Also, due to the small vertical nutrient stratification, sampling depth for total nutrients may not be as critical as in

other soils.

Although the available nutrients P, K, and Mg are

available in only a fraction of the amount of the total

nutrients, enough of each is present in southern bottomland soils for good growth, as evidenced by the lack of

deficiency symptoms and response in fertilizer trials

(Francis 1985). Response to N fertilization most often ’

occurs in old-field stands where much of the organic

matter with its nitrogen has been lost.

Nutrients potentially withdrawn by whole-tree harvest

of bottomland hardwoods on very short rotations can

exceed nutrients added by rainfall and other sources by

a few kilograms per hectare per rotation (Blackman

1979; Francis and Baker 1982; Francis 1984). This withdrawal could, over many rotations, reduce both the available and fixed pools of nutrients and lead to deficiencies

and reduced growth. The average weights of nutrients

that were removed by a simulated summer-whole tree

harvest from five bottomland hardwood stands with

sawlog-size trees were: N, 369 kg/ha; P, 37 kg/ha; K,

202 kg/ha; Ca, 783 kg/ha; and Mg, 70 kg/ha’. Of these

nutrients, only the withdrawal of Ca exceeded the accumulated nutrient additions in local rainfall (Lockaby

1981) over a 75-year rotation, and this by 319 kg/ha.

Nothing is known about losses or gains from periodic

floodwaters. The species mix and character of the vegetation harvested would certainly influence the rate of

removal of nutrients. However, several rotations would

certainly be required before deficiencies would be felt on

even the poorest sites sampled. This is a small sample

of the numerous alluvial soils in the South, and it is likely

that soils exist, especially in the Coastal Plain, that are

lower in nutrient reserves than these reported. Before

intensive harvests are commenced, a soil test of at least

exchangeable Ca should be done. When nutrient reserves are encountered that do not far exceed the quantities expected to be removed, either a less intensive

harvest regime should be employed or a fertilizer

maintenance program prescribed.

1 Francis, John K. 1985. Nutrient distribution in bottomland hardwood

stands and projections for nutrient removal by harvesting alternatives.

Unpublished final report SO-1 11 O-65 on file at the USDA Forest Sewice, Southern Hardwoods Laboratory, Stoneville, Mississippi.

4
LITERATURE CITED

Blackman, B.G. Estimates of nutrient drain by dormantseason harvests of coppice American sycamore. Res.

Note SO-245. New Orleans, LA: U.S. Department of

Agriculture, Forest Service, Southern Forest Experiment Station; 1979. 5 p.

Bremner, J.M.; Mulvaney, C.S. Nitrogen-total. In: Methods of soil analysis, Part II, Chemical and microbiological properties. No. 9 (Part 2). American Society of

Agronomy; Madison, WI. p. 595-624; 1962.

Broadfoot, W.M. Hardwood suitability for and properties

of important Midsouth soils. Res. Pap. SO-127. New

Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station; 1976.

84 p.

Buckman, H.O.; Brady, N.C. The nature and properties

of soils. The MacMillan Co., New York; 1960. 567 p.

Francis, J.K. Yield and nutrient removal by whole-tree

harvest of a young bottomland hardwood stand. Res.

Note SO-305, New Orleans, LA: U.S. Department of

Agriculture, Forest Service, Southern Forest Experiment Station; 1984. 4 p.

Francis, J.K. Bottomland hardwoods fertilization-the

Stoneville experience. In: Proceedings of the Third

Biennial Southern Silvicultural Conference (Atlanta,

GA, Nov. 7-8, 1984). Gen. Tech. Rep. SO-54. New

Orleans, LA: US. Department of Agriculture, Forest

Service, Southern Forest Experiment Station; p. 346-

350; 1985.

Francis, J.K.; Baker, J.B. Potential for nutrient depletion

by short rotation harvest of sweetgum. Soil Science

Society of America Proceedings 46:1116-l 118; 1982.

Hornbeck, J.W.; Kropelin, W. Nutrient removal and

leaching from a whole-tree harvest of northern hardwoods. Journal of Environmental Quality 11:309-316;

1982.

Jackson, ML. Soil chemical analysis. Prentice-Hall,

New York. p. 193-195; 1958.

Lockaby, B.G. Nutrient cycling in eastern cottonwood

plantations on alluvial soils of the southern Mississippi

floodplain. Ph.D. Thesis, Mississippi State University,

Univ. Microfilms 81-19207. Ann. Arbor, Ml; 1981.

Smith, B.F.L.; Bain, D.C. A sodium hydroxide fusion

method for the determination of total phosphate in

soils. Communications in Soil Science and Plant Analysis. 13:185-l 90; 1982.

Soil Test Work Group. Procedures used by state soil

testing laboratories in the Southern Region of the

United States. South Coop. Serv. Bull. 190. Mississippi State, Ml. 1974. 23 p.

Vitousek, P.M.; Reiners, W.A. Ecosystem succession

and nutrient retention: a hypothesis. Bioscience

25(6):376-381; 1975.

aU.S.GOVERNMENTPRINTlNGO~CE:1986-761-086' 60002

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