ARS | Publication request: PHOSPHORUS FORMS AND PLANT AVAILABILITY

Submitted to: ASA-CSSA-SSSA Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 14, 2001
Publication Date: N/A

Technical Abstract: Land-applied organic wastes can lead to accumulation of phosphorus (P) in soil and can contribute to nonpoint source pollution of surface waters. The objective of this study was to investigate soil test P changes due to various P sources in an INCUBATION STUDY and to determine plant available P from the same P sources in a GREENHOUSE STUDY. The P sources were whole (Whole), fiber (Fiber), low (Low P), medium (Medium P), high (High P), P manures, biosolids (Biosolids), and calcium phosphate (CaHPO4) applied at rates of 0, 101, 202, and 404 kg P/ha to a silt loam soil and incubated at 21 °C. Five soil samplings were taken at 16-wk intervals and analyzed for deionized water, Mehlich 3, Bray-Kurtz P1, ammonium oxalate extractable P, P saturation, bioavailable P, and anion exchange membrane extractable P. In the greenhouse study, similar P treatments were applied to sand or sand+soil cultures, and a wheat test crop was harvested and analyzed for total P. In general, Low P and Fiber supplied the least available P, CaHPO4 the most, and Medium P, High P, Whole, and Biosolids contributed intermediate amounts of P according to the soil P test used in the incubation study. Agronomic and environmental P tests were strongly correlated. In sand, P sources increased P uptake in the order Low P<Whole<Fiber< CaHPO4<High P<Medium P<Biosolids, but increased in sand+soil in the order CaHPO4<Fiber<Whole<Low P<Medium P<High P. Results of the greenhouse study indicate that organic P mineralization and reaction of soluble P with soil constituents mask initial differences in plant availability among P sources.