Effect of timing of simulated rain on ammonia volatilization from surface‐applied broiler litter

Abstract

Surface application of animal manures may lead to significant nitrogen (N) losses through ammonia (NH₃) volatilization. Understanding the factors that control these NH₃ losses is important for predicting the amount of manure N that will be available to crops. Field studies have shown that rain following cattle manure application can reduce NH₃ volatilization. Similar results may be expected with broiler litter due to its high concentration of water‐soluble N. The objective of this work was to evaluate the effect of timing of simulated rainfall on NH₃ volatilization and N mineralization from surface‐applied broiler litter. In one study, broiler litter from six broiler houses was applied (224 kg N ha^‐1) on the surface of packed soil columns that received 40 mm of simulated rain either immediately before or immediately after litter application. Following treatments, the columns were placed in a flow‐through system (25°C) that trapped NH₃ volatilized for 21 days. In another study, packed soil columns received no rain or 20 mm of rain at 0 to 4 days after broiler litter application. On average, the addition of 40 mm of rain immediately after litter application reduced NH₃ losses by 49% when compared to the addition of rain immediately before litter application. Soil inorganic N data supported the hypothesis that percolating rain solubilized litter N and transported it into the soil, thereby reducing NH₃ losses. For most broiler litter samples, net N mineralization was not affected by the rain treatments. The addition of 20 mm of rain at 0 to 4 days after broiler litter application temporarily increased the rate of NH₃ loss when compared to the treatment that did not receive rain. In the long‐term, however, the addition of 20 mm of rain tended to decrease total NH₃ losses. Our results suggested that total NH₃ losses from surface‐applied broiler litter may be reduced by rain or irrigation received immediately after manure application. These results warrant further studies on the effect of rain on NH₃ volatilization from surface‐applied broiler litter under field conditions.