Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 7/23/2004
Publication Date: 11/5/2004
Citation: Sharpley, A.N., Allen, A., Kleinman, P.J.A., Saporito, L.S., Stout, W.L. 2004. Changing from N- to P-based manure management can decrease soil and runoff P[abstract]. American Society of Agronomy Abstracts. Paper No. 3708. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Application of manure to soils at rates exceeding crop removal can result in an accumulation of P in soil and exacerbate losses in runoff. In such cases, recently mandated comprehensive nutrient management plans require manure applications to be based on either an environmental soil P threshold (here 100 mg/kg as Mehlich-3 P) related to runoff P potential or crop removal rates of P (here 30 kg P/ha), rather than previous recommendations based on crop N requirements (here 75 kg P/ha). Even so, there is little data to show that P-based manure management decreases P loss in runoff water. In 2000, we started to study the effect of P- and N-based manure management on soil and runoff P at the University of Maryland Eastern Shore's research farm, using 18, 0.1 ha plots in corn or soybean on an Othello silt loam, with 'excessive' soil test P (480 mg/kg as Mehlich-3 P). In the fall of 2003, soil test P had decreased to 410 mg/kg on the environmental soil P threshold treatment (no manure P), while soils decreased to 430 mg/kg for the crop-P removal treatment. Over the same period, N-based manure applications had increased soil test P to 515 mg/kg. Dissolved P in runoff was initially 0.65 mg/L and averaged 0.57, 0.61, and 0.67 mg/L for the environmental soil P threshold, crop-P, and N-based treatments in 2002. Although soil and runoff P was still above environmental thresholds, P-based manure management can reduce the potential for P in runoff water.