Monday, November 5, 2007
119-15

Total Phosphorous, Calcium, Aluminum and Iron Levels in Cecil Soil after Ten Years of Poultry Litter Application.

Dinku Endale1, Zhongqi He1, Harry Schomberg1, Wayne Honeycutt2, Michael Jenkins1, and Ron Sharpe1. (1) USDA-ARS, USDA-ARS, 1420 Experiment Station Rd., Watkinsville, GA 30677, (2) USDA, USDA-ARS University of Maine, New England Plant Soil Water Lab, Orono, ME 04469

Poultry litter (PL) is an inexpensive and effective organic fertilizer. However, there is concern with over application due to concerns of excess releases of nutrients, especially phosphorus, and metals into water bodies resulting in impairments such as eutrophication. We characterized and compared total P, Ca, Al, and Fe levels in a Cecil soil near Watkinsville, GA, from five years each of cotton and corn production under combinations of two tillage (conventional tillage and no-till) and two fertilizer sources (PL and inorganic fertilizer). During the cotton, PL application rate of 4.5 Mg ha-1 was based on crop nitrogen requirement. During the corn PL application rates rose 2 to 4 times that of cotton partly because of corn's greater nitrogen requirement and also due to inclusion of a water quality study component related to hormones. Soil P levels rose markedly in PL plots during the corn. In the surface 15 cm of soil, the average soil total P level nearly doubled from below 300 mg/kg to about 560 mg/kg in both conventional tillage and no-till. We also observed soil P stratification under PL within this 15 cm soil layer. The soil P level averaged 1000 mg/kg in the 0-2.5 cm depth, 700 mg/kg in the 2.5 to 5.0 cm depth, and 450 mg/kg in the 5.0-15.0 cm depth. Application of PL also increased Ca level but only in the 0-15 cm depth. No significant change of Al and Fe was observed but the no-till plots exhibited more variability in the metal data. Application of PL at or above agronomic needs of corn appears to raise soil P levels in Cecil soil. A more elaborate study with different PL rates at the same time might establish the critical level of PL application for corn with respect to increases in soil P levels.