Monday, November 5, 2007

Broiler Litter Application Method and Antecedent Time to Runoff Initiation Effect on Nutrient and E. coli Losses from Tall Fescue Pasture.

Karamat Sistani1, H. Allen Torbert1, T. Way2, Carl Bolster3, and Jason Warren1. (1) USDA-ARS, 230 Bennett Lane, Bowling Green, KY 42104, (2) USDA-ARS National Soil Dynamics Lab., USDA-ARS, Auburn, AL 36832, (3) USDA-ARS, Animal Waste Management Research Unit, 230 Bennett Lane, Bowling Green, KY 42104

Many studies have indicated the advantages of manure incorporation into soil in contrast to broadcast application to reduce nutrient losses. However, subsurface application of poultry litter through injection banding into a perennial forage system has not been evaluated. We used rainfall simulations to examine; 1) the effect of broiler litter application method on nutrient and E. coli losses in runoff from tall fescue pasture in the Appalachian Plateau; 2) to determine the impact of antecedent time to runoff initiation on nutrient and E. coli losses in runoff. Runoff plots were constructed on Hartsells fine sandy loam (Typic Hapludults) soil with permanent ‘Kentucky 31' tall fescue (Festuca arundinacea)  pasture in Crossville, AL. Broiler litter was applied at a rate of 8.97 Mg ha-1 by either broadcast application or by subsurface banding. Additional plots were included which received a broadcast application of commercial fertilizer (19-19-19) applied at a rate of 269 kg N ha-1 corresponding to the N applied with the broiler litter treatment. To examine the impact of antecedent time to runoff initiation on nutrient and E. coli losses, the runoff events were initiated on a  weekly basis from week 1 to week 4 on separate sets of plots after litter application. Inorganic N and E. coli concentrations in runoff were significantly greater from broadcast litter application than subsurface litter application, while fertilizer treatment had runoff with greater NH4-N but smaller NO3-N than litter application treatments. The loss of total phosphorus (TP), NO3-N, and total suspended solids (TSS) from broadcast litter method was 83.5%, 64%, and 68% greater than subsurface litter application method, respectively. About 81% of the runoff TP concentration was in the form of dissolved reactive phosphorus (DRP) for both litter-application methods. Results also indicated that longer antecedent time to runoff initiation resulted in lower nutrient and E. coli losses by runoff water. This clearly demonstrates that the length of time that litter application can be applied before a runoff event will greatly reduce nutrient losses, and that the guidelines aimed at increasing the time between litter application and large rainfall events should be an effective best management practice.