Effects of Drying Intervals and Repeated Rain Events on Runoff Nutrient Dynamics from Soil Treated with Broiler Litter

Even though the effect of poultry litter application on runoff nutrient concentrations has been thoroughly evaluated, the timing of broiler litter application and estimated runoff nutrient dynamics are not well documented. The objectives of this study were to evaluate how time to rainfall and repeated rain events affect nutrient concentrations and dynamics in runoff from a Ruston sandy loam (fine, mixed active, thermic Aquic Hapludults) soil established with Bermuda grass (Cynodon dactylon L.). Air-dried soil was packed into runoff boxes (144 cm long, 20 cm wide, and 10 cm deep) to a bulk density of 1.30 g cm−3. Hybrid Bermuda grass was established by plugging (26 plugs per box). Broiler litter was broadcast at the rate of 9 Mg ha−1. Simulated rainfall (27 mm h−1) was applied until 15 min of runoff was collected at 0, 3, 6, and 9 d after broiler litter application. Also, 8 successive rainfall events were applied at 3-d intervals to the soil incubated for 9-d with broiler litter and commercial fertilizer and runoff was collected for 15 min for each rain event. Increasing time between litter application and rainfall event from 0 to 9 d reduced runoff of total N, NH4-N and NO3-N by 50, 64, and 31%, respectively. Total P and dissolved P concentrations in runoff decreased to 35 and 43% of initial time of application values (0 d), respectively. Runoff N, P, K, Ca, Mg, Cu, and Zn concentrations decreased with successive rain events and approached the ones in unfertilized soil. Avoiding litter applications during periods of possible high intensity rainfall reduces the potential environmental hazard.