Wednesday, 9 November 2005
4
Standardizing the Water-Soluble Phosphorus Test for Manures and Biosolids.
Dan Sullivan1, Peter Kleinman2, Ann Wolf3, Robin Brandt4, Zhengxia Dou5, Herschel Elliott6, John Kovar7, April Leytem8, Rory Maguire9, Philip Moore8, Andrew N. Sharpley10, Amy Shober11, J. Thomas Sims11, Gurpal Toor12, Hailin Zhang13, and Tiequan Zhang14. (1) Oregon State University, OSU-Dep. Crop & Soil Science, 3017 Ag. & Life Sciences, Corvallis, OR 97331-7306, (2) USDA Agricultural Research Service, USDA-ARS-PSWMRU, University Park, PA 16802-3702, (3) Penn State University, 111 Agric Analytical Serv Lab, University Park, PA 16802, (4) Dept Agricultural and Biological Engineering, Penn State University, University Park, PA 16802, (5) University of Pennsylvania, School of Veterinary Medicine, 382 W. Street Rd., Kennett Sq., PA 19348, (6) Penn St. University, 220 Agr. Engr. Bldg., University Park, PA 16802-1909, (7) USDA-ARS Natl. Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011-4420, (8) USDA-ARS, 3793 N 3600 E, Kimberly, ID 83341-5076, (9) North Carolina State University, Department of Soil Science, PO Box 7619, Raleigh, NC 27695-7619, (10) USDA - ARS, 3702 Building - Curtin Road, University Park, PA 16802, (11) University of Delaware, Dept of Plant & Soil Science, 152 Townsend Hall, Newark, DE 19716, (12) University of Arkansas, Biological & Agricultural Engineering, 207 Engineering Hall, Fayetteville, AR 72701, (13) Oklahoma State Univ., Dept. of Plant & Soil Sciences, Stillwater, OK 74078, (14) Agriculture & Agri-Food Canada, 2585 County Road 20, Harrow, ON N0R1G0, Canada
Water extractable P (WEP) in biosolids and manures has been shown to be an effective indicator of runoff P loss potential. To be an effective commercial test, a WEP method must meet reproducibility and other production laboratory analytical criteria, and it must reflect differences in runoff dissolved P. The objective of this project was to develop data for choosing a single WEP procedure for inclusion in a national (CSREES SERA-17) testing manual. Cooperating laboratories conducted extraction experiments to evaluate (i) solution:solids ratio (10, 100 or 200) and (ii) the sample size used to determine WEP. A runoff box study was also conducted to evaluate the effect of different WEP protocols on the correlation between dissolved P in runoff and WEP of surface applied biosolids and manures. As extraction ratio increased from 1:10 to 1:200, so did WEP, with a few exceptions. All WEP extraction protocols were highly correlated (r2 > 0.7) with dissolved P in runoff. WEP extractions were reproducible within labs and between labs. Increasing manure or biosolids sample size for WEP test did not improve precision. Obtaining a 1:10 extract suitable for ICP or colorimetric determination was difficult for some biosolids and dairy manure samples. The consensus extraction procedure will be included in a revision of "Methods of Phosphorus Analysis for Soils, Sediments, Residuals, and Waters" available at www.sera17.ext.vt.edu.
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