Survey of Water-Extractable Phosphorus in Livestock Manures
- Peter J. A. Kleinman *a,
- Ann M. Wolfb,
- Andrew N. Sharpleya,
- Douglas B. Beeglec and
- Lou S. Saporitoa
- a USDA-ARS, Pasture Systems and Watershed Management Research Unit, Curtin Road, University Park, PA 16802
b Agricultural Analytical Services Laboratory, The Pennsylvania State University, University Park, PA 16802
c Dep. of Crop and Soil Sciences, The Pennsylvania State University, University Park, PA 16802
Water-extractable P (WEP) in manure is increasingly used as an environmental indicator as it is correlated with P in runoff from soils recently amended with manure. Little information exists on WEP variability across livestock manures. A survey of 140 livestock manures was conducted to assess trends in WEP (dry weight equivalent) related to livestock types and manure storage. Manure WEP ranged widely (0.2–16.8 g kg−1), with swine (Sus scrofa domestica L.) having the highest average concentrations (9.2 g kg−1), followed by turkey (Melleagris gallopavo) (6.3 g kg−1), layer chickens (Gallus gallus domesticus L.) (4.9 g kg−1), dairy cattle (Bos taurus) (4.0 g kg−1), broiler chickens (Gallus gallus domesticus L.) (3.2 g kg−1), and beef cattle (Bos taurus) (2.3 g kg−1). Manure WEP also differed by general storage system; dry manures contained significantly lower WEP concentrations (3.9 g kg−1) than manure from liquid storage systems (5.4 g kg−1). Within liquid storages, no significant differences in WEP were observed between covered and uncovered storages or between bottom-loaded and top-loaded storages. Dry-matter (DM) content of manure was weakly correlated to WEP across all manures (r = −0.44), but strongly correlated with WEP in liquid swine manure (r = −0.87) and dairy manure (r = −0.72), suggesting dissolution of phosphate compounds as manure solids are diluted in storage. Varying positive correlations were observed between WEP in manure and water-extractable Ca, Mg, and Fe, or total P, depending on livestock category. Results of this study show that livestock manure can be categorized by WEP, a key step toward differential weighting of agricultural P sources in P site assessment indices.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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