Wednesday, 9 November 2005
5

Soil P Levels in No-Till Amended with Broiler Litter.

Dinku Endale1, Harry Schomberg1, Miguel Cabrera2, and Michael Jenkins1. (1) USDA-ARS, 1420 Experiment Station Road, Watkinsville, GA 30677-2373, (2) Crop and Soil Sciences, University of Georgia, Plnt Sci Bldg-1201 Mason Mill Rd, Athens, GA 30602

Eutrophication problems in surface waters arising from P management in crop and livestock production systems are of national concern, especially from broiler litter use. Researchers from USDA-ARS J. Phil Campbell Sr. Natural Resource Conservation Center in Watkinsville, GA, and University of Georgia, Athens, GA, monitored soil P levels in a Cecil soil over eight years in production of cotton followed by corn under conventional- or no-tillage (CT or NT) fertilized with either ammonium nitrate or broiler litter (AN or BL). Initially, fertilizers were managed primarily to meet crop nitrogen needs with additional P and K needs determined based on soil tests and regional recommendations. Levels were subsequently increased, however, to investigate water quality issues. During the initial four years of cotton production under 2 tons per acre of broiler litter application (60 lbs N per acre requirement) mean soil P levels in pounds per acre in the surface 6 inches were 29 for CTAN, 48 for CTBL, 43 for NTAN and 67 for NTBL. Two years of corn followed under 5 tons per acre of broiler litter application. Mean soil P levels (lbs per acre) increased to 37 for CTAN, 95 for CTBL, 52 for NTAN and 115 for NTBL. Broiler litter application increased to 10 then back to 5 tons per acre for the remaining period of corn production. Soil P level increments were higher than the previous period. Means in pounds per acre were 44 for CTAN, 194 for CTBL, 63 for NTAN and 225 for NTBL. The research demonstrates the need for a holistic approach to managing broiler litter as fertilizer in tillage systems.

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