Phosphorus Dynamics in Soils Amended with Dairy Manures from Modified Diets. (S11-toor996274-poster)
Authors:
G.S. Toor* - Univ. of Delaware J.T. Sims - Univ. of Delaware Z. Dou - Univ. of Pennsylvania
Abstract:
Phosphorus (P) losses from agricultural production systems have contributed to the widespread eutrophication of natural waters. This is especially true in areas with intensive animal farming, where repeated manure applications have led to excessive accumulation of P in soils. Recent research has begun to focus on ways to reduce P excretion in manures through dietary modification by feeding P closer to the animal requirement. On dairy farms, it has been a common practice to add inorganic P to diets due to concerns that the amount of available P in the organic ingredients may be inadequate for satisfactory cow performance. National Research Council recommends 0.32 to 0.38 % P for lactating dairy cows. However, on many US dairy farms, P is often supplemented at the rates much higher than the recommended range, sometimes reaching up to 0.80 % P. The excessive addition of inorganic P results in higher P excretion in manure, increasing the potential of P losses to waters. The objective of this study was to investigate the effect of dairy diet modification on P forms in manures and
manure-amended soils. Through laboratory incubation trials, two soils were amended with dairy manures at a uniform rate of 150 kg P/ha. The manure samples were collected from commercial dairy farms in the Northeast and Mid-Atlantic regions and contained total P ranging from 5.5 to 14.0 g/kg manure dry matter. Water extractable P, Mehlich 3 P, and sequential P fractionation data will be reported.
Speaker Information: Gurpal Toor, Univ. of Delaware, Department of Plant & Soil Sciences, Newark, DE 19716; Phone: 302-831-4190; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 4:00 PM-6:00 PM Presentation Start: 4:00 PM (Poster Board Number: 1231)
