RUNOFF FROM COTTON FIELDS FERTILIZED WITH POULTRY LITTER

Abstract

Broiler litter is a valuable soil amendment for crop production, with litter typically applied to land areas used forgrazing and/or hay production. Historically, farmers have based litter application rates on the nitrogen (N) needs of thereceiving crop; however, this results in overapplication of phosphorus (P). To alleviate the tendency to accumulate P innearby watersheds, export of litter to other regions has been proposed. A field study was conducted at the University ofArkansas Northeast Research and Extension Center at Keiser, Arkansas, to quantify the impact of poultry litter on runoff waterquality from cotton (Gossypium hirsutum L.) cropland in the Mississippi River Delta. Six 0.6ha fields were fertilized witheither commercial fertilizer (annually 140 kg N ha 1 yr 1 in a split application) or poultry litter (7,200 to 9,200 kg litter ha 1yr 1 ). Runoff from each field was diverted through an Hflume, where water samples were collected. Stage was recorded andused to compute runoff flow. Concentration and mass loss of eight waterquality analytes were measured from 21 individualrunoff events over a threeyear monitoring period. Seedcotton yield was lower from the litterfertilized plots, suggesting aneed for refinements in the production system. Threeyear total mass losses of total suspended solids (TSS) and nitratenitrogen (NO3N), as well as total runoff volume, were reduced from fields receiving poultry litter compared to fields receivingcommercial fertilizer. Differences associated with the two fertilizer treatments did not clearly exhibit a systematic change overthree years, as would be expected if soil structure were changing as a result of the organic amendments. Although total TSSmass loss was reduced, concentrations of nutrients associated with the solid fraction of chicken litter increased periodicallyin runoff events that immediately followed litter application. Moreover, total loss of orthophosphate P from littertreatedfields was four times greater than from fields fertilized conventionally. Additional research is needed to ensure that poultrylitter exported to the Mississippi River Delta region can be applied as part of an integrated crop fertility program that resultsin the desired agronomic performance while protecting and enhancing water quality.