Charcterizing the Effects of Excessive Phosphorus Rates on Soil Test Phosphorus. (S11-lory511577-poster)
Authors:
J.A. Lory* - University of Missouri P.C. Scharf - University of Missouri
Abstract:
The objective of this research was to assess the impact of excessive phosphorus (P) rates on soil test P (STP). Nitrogen-based application rates of manure and sludge materials from animal feeding operations can result in P applications rates that substantially exceed crop need. Six P rates (0, 67, 111, 177, 892 and 2,231 kg P/ha) as ammonium polyphosphate (AP) and 2 P rates (67 and 111 kg P/ha) as poultry litter were surface applied to tall fescue on 3 soil types. Treatments were replicated 3 times in a completely randomized design and soil samples (0-5, 5-10 and 10-15 cm) were taken 31, 198 and 408 days after application. Agronomic rates (0 to 177 kg P/ha) of AP resulted in a linear increase in STP. The Lagonda soil was more responsive to added AP than the Creldon and Mexico soils.
Response of STP to excessive rates of P was linear and greater than predicted by agronomic P rates 31 and 198 days after application. Response of STP to excessive P rates decreased with each sampling date for all soils and was not significantly different than the response to agronomic rates 408 days after application for only the Lagonda soil. These results indicate P application rates in excess of agronomic need can pose a greater water quality risk because they maintain significantly higher STP levels than predicted by agronomic P rates for at least 198 days after surface application in forages.
Speaker Information: John Lory, University of Missouri, Department of Agronomy 210 Waters Hall Universit, Columbia, MO 65211; Phone: 573-884-7815; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 4:00 PM-6:00 PM Presentation Start: 4:00 PM (Poster Board Number: 1431)
