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United States Department of Agriculture

Agricultural Research Service

Title: Phosphorus Availability Coefficients from Various Organic Sources

item Smith, Matthew
item White, Kathryn - Kate
item Coale, Frank

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2007
Publication Date: 6/18/2007
Citation: Smith, M.C., White, J.W., Coale, F.J. 2007. Phosphorus Availability Coefficients from Various Organic Sources. ASABE Annual International Meeting.

Interpretive Summary: .

Technical Abstract: The objectives of this study were to determine Phosphorus Availability Coefficients (PACs) for a variety of organic phosphorus (P) sources, and to examine the relationship between PACs measured in simulated rainfall runoff and alternative soil incubations. PAC is an important parameter in the P-Index which is used in some states as part of comprehensive nutrient management planning. Two parallel studies were conducted. An incubation study was utilized to calculate PACs for various organic P sources through incubation of amended soils using three different methods to measure the P available for runoff. A runoff study, using the P protocols established by the National Phosphorus Research Project, directly measured PACs and was used to compare rainfall simulator results with those from the incubator studies. The organic P sources studied were liquid dairy manure (separated and unseparated), digested dairy manure, dairy manure solids, commercial broiler litter, and compost. Two additional treatments studied were triple super phosphate and an unamended control. The soil used in the study was a Mattapex silt loam. Results of the runoff experiments show PAC values ranging from nearly 80% for unseparated dairy manure to approximately eight percent for dairy solids. Comparisons between the runoff and incubation studies will be presented in detail.

Last Modified: 07/26/2017
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