EFFECT OF TIMING OF SIMULATED RAIN ON AMMONIA VOLATILIZATION FROM SURFACE-APPLIED BROILER LITTER

Surface application of animal manures may lead to significant nitrogen (N) losses through ammonia (NH3) volatilization. Understanding the fa ctors that control these NH3 losses is important for predicting the am ount of manure N that will be available to crops. Field studies have s hown that rain following cattle manure application can reduce NH3 vola tilization. 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 vol atilization 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 litt er application. Following treatments, the columns were placed in a flo w-through system (25 degrees C) that trapped NH3 volatilized for 21 da ys. 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 reduce d NH3 losses by 49% when compared to the addition of rain immediately before litter application. Soil inorganic N data supported the hypothe sis that percolating rain solubilized litter N and transported it into the soil, thereby reducing NH3 losses. For most broiler litter sample s, net N mineralization was not affected by the rain treatments. The a ddition of 20 mm of rain at 0 to 4 days after broiler litter applicati on temporarily increased the rate of NH3 loss when compared to the tre atment that did not receive rain. In the long-term, however, the addit ion of 20 mm of rain tended to decrease total NH3 losses. Our results suggested that total NH, losses from surface-applied broiler litter ma y be reduced by rain or irrigation received immediately after manure a pplication. These results warrant further studies on the effect of rai n on NH3 volatilization from surface-applied broiler litter under fiel d conditions.