The four P sources were applied as raw manure, compost and vermicompost from Dyecrest Dairy manure and rock phosphate (<0.02 mm 2). In 2002, each treatment was applied at 90 and 180 kg ha -1 P2O5 .

Results

• The high rate of raw manure treatment had significantly higher Olsen P in 2002 and 2003 as compared to all other treatments including the control.

• The high rate raw manure treatment resulted in significantly higher total dissolved P values in 2002 and higher total P, total dissolved P and dissolved inorganic P values in 2003 than all other treatments including the control.

• The vermicompost treatment produced less overall P runoff than the raw manure treatments.

• Although the plant P values illustrate a significant nutrient uptake difference among treatments, other unmeasured variables affected yield along with P availability.
• This study concluded that compost and vermicompost that have been applied at the same P2O5 rate as raw manure have significantly less runoff P available than raw manure.

• Rock P was not soluble in this alkaline soil.

Graduate Student: Addy Elliott, currently Research Associate with Colorado State University Soil and Crop Sciences Department.
Co-Principal Investigators: Reagan Waskom , Dana Christensen

Funding from the USDA-Natural Resources Conservation Service , the U.S. Environmental Protection Agency Pollution Prevention Program, and the Regional SDA-CSREES Water Quality Program.

Article: Phosphorus Fertilizers for Organic Farming Systems

Factsheet: http://www.ext.colostate.edu/pubs/crops/00569.html

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