Monday, November 5, 2007

Evaluation of Continuous-Furrow Knife Aeration to Reduce P Export from Applied Poultry Litter Using a Paired-Watershed Approach.

David Butler1, Miguel L. Cabrera1, Dorcas H. Franklin2, Larry West1, Armando S. Tasistro1, Kang Xia3, Vaughn H. Calvert1, and J. Frank Newsome1. (1) University of Georgia, University of Georgia Crop and Soil Sciences, 3111 Miller Plant Sciences, Athens, GA 30602, (2) USDA-ARS, 1420 Experiment Station Road, Watkinsville, GA 30677, (3) Mississippi State University, 3316 Hand Lab, Morrill Rd., Mississippi State, MS 39759

Surface-applied manures are of particular concern in the Southern Piedmont (USA) because of a high concentration of broiler production.  As these manures can contribute to P in runoff, a study was conducted to examine the water conservation potential of mechanical aeration of grasslands.  Mechanical aeration has potential to reduce P transport by increasing infiltration of rainfall and binding of P with soil minerals.  The effect of continuous-furrow knife aeration perpendicular to the slope on the export of total Kjeldahl P (TKP), total dissolved P (TDP), and dissolved reactive P (DRP) in surface runoff from pastures with applied broiler litter was examined using a paired watershed approach.  Six paired, bermed field watersheds (0.79-ha each) were monitored by automatic sampling during rainfall events for 4 yr to develop calibration relationships between the paired watersheds.  From spring 2005 to fall 2007, 1 watershed from each pair was aerated (each fall and spring, immediately following broiler litter application) using ammonia injection knives attached to a chisel plow frame.  Aeration was to an average depth of 10-cm, with 27-cm spacing between rows.  Results indicate that aeration decreased TKP, TDP, and DRP export (p < 0.05) from applied broiler litter.