Estimating Potential Ground and Surface Water Pollution from Land Application of Poultry Litter

ESTIMATING POTENTIAL GROUND AND SURFACE WATER POLLUTION FROM LAND APPLICATION OF POULTRY LITTER In 1985, more than 750 million broiler chickens were produced in Arkansas. During the same year over 15 million laying chickens produced 3.6 million eggs. The waste products of these agricul­ tural production systems, poultry litter and manure, were about 1 million metric tons. As a result of land application of these wastes, about 5,000 metric tons of ammonium N and 12,000 metric tons of mineralized nitrogen were applied to Arkansas pastures in 1985. Manures contributed about 2-3 percent of the total. The objective of this research was to quantify major components of the nitrogen cycle which influence the ground and surface water pollution potential and the proper use of poultry or hen manure in a land application program. Both decomposition and N mineral­ ization of representative samples of surface applied hen manure were evaluated. During the decomposition, N mineralization fol­ lowed two patterns. Initially, N mineralization was rapid and the mineralized N plus initial inorganic N was converted to volatile ammonia and lost to the atmosphere. Later, one of two scenarios appeared to be operative. If nitrification and denitrification were small, then N im obilization likely occurred at a rate near that of N mineralization resulting in only small increases in inorganic N. Undigested feed was suggested as the immobilizing agent. If nitrification and denitrification were large, then N mineralization could have proceeded at expected rates and would not be measured by the methods employed herein. In a practical vein, the initial inorganic N and mineralized N in surface applied hen manure has a low N fertilizer value and water pollu­ tion potential due to volatilization of N. If the manure is incorporated or a rainfall event occurs soon after surface addi­ tion, more than 50 percent of the manure N could be available for plant uptake and contamination of ground and surface waters. J.T. Gilmour, D.C. Wolf, and P.M. Gale Completion Report to the U.S. Department of the Interior, Geological Survey, Reston, VA, June, 1987.