Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 7/10/2004
Publication Date: 8/13/2004
Citation: Sharpley, A.N., Allen, A., Kleinman, P.J.A;, Saporito, L.S., Stout, W.L. 2004. The effect of phosphorus- and nitrogen-based manure management on soil and runoff phosphorus. Meeting Abstract. In: Proceedings of the 12th National Nonpoint Source Monitoring Workshop: Managing Nutrient Inputs and Exports in the Rural Landscape, September 26-30, 2004, Ocean City, Maryland. p. 26. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: The continual and long-term application of manure to soils at rates exceeding crop removal can result in an accumulation of phosphorus (P) in soil and exacerbate losses in runoff water. In such cases, recently mandated comprehensive nutrient management plans require manure applications to be based on either an environmental soil P threshold (i.e., 100 mg kg-1 as Mehlich-3 P) related to runoff P potential or crop removal rates of P (i.e., 30 kg P ha-1), rather than previous recommendations based on crop N requirements (about 75 kg P ha-1). Even though P-based manure management is being put in place for high P soils over most of the U.S., there is little data to show that this change in nutrient planning strategy decreases P loss in runoff water. Thus, we quantified the effect of implementing P- and nitrogen (N)-based manure management on soil and runoff P. The study was initiated at the University of Maryland Eastern Shore's research farm in 2000 by establishing 18, 0.1 ha plots in corn or soybean on an Othello silt loam, which already had 'excessive' soil test P (400 mg kg-1 as Mehlich-3 P). In the fall of 2003, soil test P had decreased to ~325 mg kg-1 on the environmental soil P threshold treatment, which received no manure P, while soils increased to ~490 mg kg-1 for the crop-P removal treatment. Over the same period, N-based manure applications had increased soil test P to ~560 mg kg-1. Dissolved P in runoff water from the 18 plots was 0.45 mg L-1 before the P- and N-based manure treatments were implemented. Averaged for 2002, dissolved P was 0.55, 0.61, and 0.68 mg L-1 for the environmental soil P threshold, crop-P, and N-based treatments, respectively, and reflected changes in soil P. Clearly, alternative manure management required by revised nutrient planning strategies can reduce the potential for P in runoff water. However, as soil test P levels for all treatments remain above environmental thresholds (100 mg kg-1) and runoff dissolved P above eutrophication thresholds for flowing waters (0.05 mg L-1), continued evaluation of these strategies is needed to determine long-term implications to the management of farm nutrients.