Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/1999
Publication Date: N/A
Interpretive Summary: The state of Arkansas ranks second in poultry production in the U.S. Much of the broiler production in Arkansas is concentrated in the northwestern corner of the state. Poultry litter (manure and bedding material) is removed from the broiler houses once each year and spread on the land. In northwestern Arkansas, the poultry litter is most often spread on permanent pasture. The litter contains relatively high amounts of plant nutrients, especially nitrogen (N) and phosphorus (P), so it is valued as a fertilizer and is credited with improving pasture productivity. Increasing nutrient levels in surface water of this region, however, have raised concern that repeated poultry litter applications to pasture lands may lead to excessive concentrations of nutrients in surface runoff. The purpose of this study was to measure nutrient runoff from pasture plots treated with poultry litter. A rainfall simulator was used to apply a 3-inch storm one month after a typical poultry litter application. Runoff from litter-treated plots had consistently higher concentrations of all nutrients tested. Differences in the amount of runoff water, however, meant that the actual total amount of nutrients in runoff from the treated plots was not greater than from the untreated plots. This study highlights the need to measure both nutrient concentrations and the volume of runoff when evaluating animal waste effects on surface water quality.
Technical Abstract: In the Ozark Highlands, annual application of poultry litter to pasture land is a routine waste management practice. The objective of this study was to measure the effect of poultry litter application on selected water quality parameters in surface runoff from grazed pasture and forest sites. Sixteen pairs of 1 x 2 m runoff plots were established on Nixa (loamy-skeletal, siliceous, active, mesic Glossic Fragiudults) and Clarksville (loamy-skeletal, siliceous, semiactive, mesic Typic Paleudults) cherty silt loams. One plot of each pair received 4.5 Mg ha**-1 of poultry litter. A rainfall simulator was used to apply rainfall at an intensity equivalent to a 25-year return period storm (75 mm h**-1 for 1 h) one month after litter application. A composite runoff sample was analyzed for dissolved reactive phosphorus (DRP), total phosphorus (TP), ammonia-nitrogen (NH3-N), nitrate-nitrogen (NO3-N), total Kjeldahl nitrogen (TKN), and total suspended solids (TSS). Poultry litter-treated plots had consistently higher concentrations of all water quality parameters tested as compared to untreated plots. Concentration of DRP in runoff from untreated plots was linearly correlated with three soil P tests (0.35<r**2<0.85). Soil P on litter- treated plots had no effect on DRP which averaged 2.20 mg L**-1. High variation in runoff volume resulted in only NO3-N showing significantly greater losses due to poultry litter treatment at two pasture sites. These results indicate that variation in surface hydrology (infiltration rate) has a significant affect on nutrient transport from grazing lands receiving poultry litter.