Runoff Nitrogen Loss with Simulated Rainfall Immediately Following Poultry Manure Application for Corn Production

Nitrogen loss from a soybean [Glycine max (L.) Merr.]-corn (Zea mays L.) rotation by runoff to surface water can be significant. This study was conducted to determine short-term N loss in runoff immediately, after poultry Manure application and assess the effects of manure rate and incorporation on losses. The study was conducted for 3 yr at nine Iowa fields previously cropped to soybean. Poultry manure sources were applied in the fall or spring to untilled soybean stubble at in tended rates of 0, 84, and 168 kg total N ha(-1) with three replications. Within 2 d of application, simulated rainfall was applied to 3-m(2) areas to provide a single 30-min runoff event. The total Kjeldahl N (TKN) and NH(4)(+)-N concentration and load in runoff increased with higher manure rates, with the associated manure TKN and NH(4)(+)-N correlated with runoff losses. With the high manure race, runoff TKN and NH(4)(+)-N concentration averaged 33 and 15 mg L(-1) and the TKN and NH(4)(+)-N load 2.6 and 1.1 kg ha(-1), respectively. Runoff concentration and load of TKN and NH(4)(+)-N was significantly decreased with incorporation, approximately 5096 and 90%, respectively Tillage increased TKN in runoff when no manure was applied, but loses were lower than the treatment with manure and incorporation. The NO(3)(-)-N load in runoff was low and not affected by manure application. The results show that rainfall shortly after surface application of Poultry manure can result in increased runoff TKN and NH(4)(+)-N, with loss related to manure rate, specific N fraction, and incorporation, which significantly reduced manure N in surface runoff.