Submitted to: Agricultural Research Service Publication
Publication Type: Experiment Station
Publication Acceptance Date: June 30, 2004
Publication Date: June 30, 2004
Citation: Schwartz, R.C. 2004. Phosphorus extractability of soils amended with stockpiled and composted cattle manure. Agricultural Research Service Publication. p. 1-44. Technical Abstract: An assessment of the influence of manure applications on the soluble and extractable forms of P in soils is required in the development of practical nutrient management plans. The objective of this study was to determine the influence of soil characteristics, manure characteristics, and application rates on the extractability of phosphorus in amended soils incubated over time. Five selected soils of the southern high plains region were amended with fed cattle manures, composted manure, and inorganic fertilizers [Ca(H2PO4)2 and KH2PO4] at five rates and incubated under controlled laboratory conditions. Mehlich 3, Olsen (NaHCO3), TAM (Texas A&M extractant), and water extractable P were determined for the soils after a one week or eight week incubation period. Except for the TAM extractions and some water extractions, P extractability as a function of total P applied was linear over a wide range of application rates. After an eight-week incubation period, P extraction efficiency of the Mehlich 3 extractant for all soils averaged 70% for scraped manure, 84% for composted manure, and 93% for KH2PO4. Mehlich 3 and NaHCO3 P extraction efficiencies of the KH2PO4 amended Pullman soil averaged 20 and 27% greater, respectively, than the efficiencies of Ca(H2PO4)2 amended Pullman soil. Increased soil calcium and calcium contained in manures and fertilizers tended to depress P solubility and extractability. Soluble organic acids and organic anions generated by or added with manures also appeared to play a role in governing P status in these soils. The calcareous soil was capable of immobilizing larger quantities of phosphorus than other soils investigated in this study. With increasing application rates, the increase in water extractable P relative to increases in agronomic soil test P were greatest for synthetic fertilizers compared with composted or stockpiled manures. Consequently, common agronomic soil extractants in the region cannot always be used to make reliable inferences about water extractable P.