|Mcdowell, R - AG RESEARCH LMTD|
Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2003
Publication Date: November 1, 2003
Citation: Sharpley, A.N., McDowell, R.W., Kleinman, P.J. 2003. Applying manure changes the form and solubility of phosphorus in soil [Abstract]. American Society of Agronomy Meetings. Paper No. S11-sharpley903014-poster. 2003 CD-ROM. Technical Abstract: The continual application of manure increases soil and overland flow P concentrations. Less information is available on the fate of P applied to soil and its effect on soil P chemistry. Therefore, the effect of long-term (>10 years) manure applications on P form and solubility of P was determined in soils. Eight soils from Oklahoma, 115 from New York, and six from Pennsylvania that had received dairy, poultry or swine manure (40-150 kg P/ha/yr for 10-15 years), were used along with untreated soils. Although Mehlich-3 soil P concentration increased with the amount of manure applied, the proportion that was water extractable declined (R of 0.91). For example, at a Mehlich-3 P of 50 mg/kg, 10% was water extractable, while at 2800mg/kg only 3% was extracted by water. This relative decline in water extractable soil P was related to an increase in exchangeable Ca in soil (R of 0.76), added in manure. Overall, there was a general shift from Fe- and Al-P to Ca-P forms. Solubility diagrams showed hydroxyapatite to be the dominant Ca-P in untreated soils and tricalcium-P in manured soils. These results suggest that heavily manured soils can exhibit P chemistry associated with calcareous soils, even when their pH is less than 6.5. Also, the relative decline in water solubility of P in manured soils may lead to an overestimation of potential runoff losses as predicted by the Mehlich-3 extraction.