Using Landscape Position and Soil
Information to Optimize Manure Application
Thomas J. Sauer
USDA-ARS
J. Van Brahana
USDI-USGS
Timothy M. Kresse
Arkansas Department of Pollution Control and Ecology
Philip A. Moore, Jr., Sally D. Logsdon
USDA-ARS
Kenneth P. Coffey, Tommy C. Daniel, Charles V. Maxwell, Charles P. West
University of Arkansas
Sebastian M. Braum
University of Minnesota
Introduction
In spite of marked changes in the form, collection, and storage of
animal waste, little has changed in terms of attitudes and perception concerning land
application of the waste material. Land application of animal waste is often reluctantly
approached as a necessary yet unproductive activity. Consequently, growers fail to fully
appreciate the waste material as a valuable nutrient and organic matter resource that can
sustain and/or revitalize their soil. Failure to utilize animal wastes effectively can
lead to over application and offsite impacts that encourage increased government
regulation and costs of production (Govindasamy et al., 1994; Copeland, 1995; Morse, 1995;
Martin, 1997).
Here we present some concepts for improving manure utilization by
considering the role of landscape position and soil properties in designing land
application strategies. A team of researchers, agency personnel, and growers has been
organized to develop practical solutions and recommendations for effective animal waste
management. The focus of this work concerns application of poultry and swine waste to
grazing lands in the Ozark Highlands but the principles behind this effort are applicable
to any region with concentrated livestock production.
Optimizing Nutrient Use
Optimizing plant uptake of nutrients contained in animal waste
should be one of the primary objectives of any animal waste management program. Profitable
crop production can be sustained only by maintaining optimum levels of essential plant
nutrients in the soil root zone. Excessive amounts of nutrients, when applied as
commercial fertilizer or animal waste, create the potential for offsite movement to
surface or subsurface water resources. In particular, transport of phosphorus (P) in
runoff water or attached to eroded sediment and nitrate (NO3) into groundwater
are often observed after excessive levels of P and nitrogen (N) have been allowed to build
up in the soil. Too much P in lakes and streams causes accelerated eutrophication (algal
blooms, aquatic weed growth, and low dissolved oxygen). High levels of NO3 in
groundwater cause methemoglobinemia (Wetzel, 1975; U. S. Environmental Protection Agency,
1976). Therefore, effective manure management that promotes uptake of nutrients by plants
is good for both crop production as well as the environment.
Most Best Management Practices (BMPs) offered for animal waste
management relate to manure generation and handling or cropping considerations (Council
for Agricultural Science and Technology, 1996). Clearly, there is no single solution to
animal waste management problems. It is important to note that in most instances
appreciable amounts of land-applied nutrients will not leave the site of application
except when dissolved in water or attached to eroded sediment. Knowledge of how rainfall
and snowmelt are partitioned between runoff and infiltration is key to improving the
nutrient utilization efficiency of land-applied animal waste. This aspect of animal waste
management has received little attention but is one of the central objectives of this
research/education program.
The Savoy Experimental Watershed (SEW)
The Ozark Highlands are a center of poultry and swine production and
the majority of the poultry litter (solid bedding material plus manure) and liquid swine
waste is applied to pastures. The soil types and topography of the Ozarks in combination
with increased poultry and swine production have led to concern over possible animal waste
impacts on regional water resources.
The SEW is being developed as a cooperative research/education site
between scientists, agency personnel, and producers to address issues of animal waste
management in the Ozarks. The goal is to take a holistic approach to the management of
nutrients derived from applied animal wastes and the excreta of the animals grazing the
pastures. An interdisciplinary team of researchers with backgrounds in soil science,
hydrology, animal nutrition, forage production, grazing management, and hydrogeology has
assembled to initiate comprehensive studies of nutrient fate and movement within the
watershed. An advisory committee composed of commodity group, producer, and extension
representatives will provide input on the studies undertaken.
Figure 1 shows a soil map of the SEW which is located in northwestern
Arkansas adjacent to the Illinois River. In general, the upland and less-steep side slopes
of the SEW are in tall fescue and bermudagrass pasture while the steep side slopes and
valley bottom are in hardwood forest. Compared to pastures outside the SEW, animal waste
and commercial fertilizer applications in the watershed have been limited in recent years.
The watershed is 363 acres in size and contains 6 soil types (Table 1).
As part of an initial site assessment, several soil properties were
measured on surface soil cores (0 to 4 in.) taken from 4 soils (Rg, Ca, Gu, and Na). A
complete discussion of these data is available in Sauer et al. (1998). A brief summary is
presented here. Each of the soils sampled had comparable amounts of sand, silt, and clay
(approximately 20, 70, and 10%, respectively) but the Rg soil had significantly more
gravel (43% as compared to 26, 22, and 12% for Gu, Na, and Ca, respectively). As a result,
the Rg soil had a much higher hydraulic conductivity than the other soils indicating a
greater ability to transmit water. When ponded infiltration measurements were made the
differences were much smaller. This is likely due to the presence of rodent burrows in the
Ra soil and layering within the Rg soil. Water draining from the SEW must cross the Razort
silt loam soil (Ra, Figure 1) in the alluvial plain before entering the Illinois River.
Measurements on this soil showed that it had the highest infiltration rate of any of the
soils measured (2.1 in h-1). In addition, it also had the highest clay content
(20%) and cation exchange capacity (an index of a soil's ability to retain some forms of
nutrients).
This study indicates that soil types in the valley bottom and along the
Illinois River have higher infiltration rates and potential to absorb P and N forms (i.e.
higher clay content). Thus, nutrients transported in runoff water from animal wastes
applied to upland pastures could be adsorbed when the runoff water reaches these soils.
Even though the Ca, Gu, and Na soils have lower infiltration rates and clay content and
are located on steeper slopes, application of animal wastes to these soils may not
represent an unreasonable risk of nutrient runoff to the river due to the presence of
soils with greater infiltration and nutrient adsorptive capacity downhill.
Summary
Recognizing that water is the primary carrier of nutrients from
animal waste across and into soils, the varying ability of soils to infiltrate water and
absorb nutrients present in the water are important considerations in devising a land
application strategy. Preliminary data from a site in Arkansas suggest that changes in
infiltration rate, nutrient content, and absorptive capacity with landscape position could
be used to identify preferred locations for animal waste applications. Such an approach
could supplement existing methods for assessing nutrient runoff potential (e.g. Lemunyon
and Gilbert, 1993) and/or be incorporated into site-specific farm management programs
(Vanden Heuvel, 1996) to both optimize plant uptake of nutrients contained in the animal
waste and to reduce offsite impacts.
References
Copeland, J. D. 1995. The criminalization of environmental law:
implications for agriculture. Oklahoma Law Review 48:237-288.
Council for Agricultural Science and Technology. 1996. Integrated animal
waste management. Task Force Report No. 128. 87 pp. Ames, Iowa.
Govindasamy, R., M. J. Cochran, and E.
Buchberger. 1994. Economic
implications of phosphorus loading policies for pasture land applications of poultry
litter. Water Resources Bulletin 30:901-910.
Harper, M. D., W. W. Phillips, and G. J. Haley. 1969. Soil survey of
Washington County, Arkansas. U. S. Department of Agriculture, Soil Conservation Service,
U.S. Government Printing Office, Washington, D.C.
Lemunyon, J. L., and R. G. Gilbert. 1993. The concept and need for a
phosphorus assessment tool. Journal of Production Agriculture 6:483-496.
Martin, J. H. Jr. 1997. The Clean Water Act and animal agriculture.
Journal of Environmental Quality 26:1198-1203.
Morse, D. 1995. Environmental considerations of livestock producers.
Journal of Animal Science 73:2733-2740.
Sauer, T. J., P. A. Moore, Jr., and K. P. Coffey. 1998. Characterizing the
surface soil properties along an Ozark toposequence. Soil Science (in preparation)
U. S. Environmental Protection Agency. 1976. Quality criteria for water.
U. S. Government Printing Office, Washington, D.C. 256 pp.
Vanden Heuvel, R. M. 1996. The promise of precision agriculture. Journal
of Soil and Water Conservation 51:38-40.
Wetzel, R. G. 1975. Limnology. W. B. Saunders Co., Philadelphia. 743 pp.
Figure 1. Soil survey map with the Savoy Experimental Watershed
delineated (from Harper et al., 1969).
N
![](20524/manuremgmt/Image53.gif)
Table 1. Soil types of Savoy Experimental Watershed.
Symbol |
Name |
Slope (%) |
Position |
Rg |
Razort gravelly silt loam |
0-2 |
valley bottom |
Cl |
Clarksville cherty silt loam |
12-60 |
ridge side slope |
Na |
Nixa cherty silt loam |
3-8 |
ridge top |
Ps |
Pickwick silt loam |
3-8 |
upland |
Ca |
Captina silt loam |
3-6 |
stream terrace |
Gu |
Guin cherty silt loam |
3-8 |
ridge side slope |
To
Top |