Characterization of Water Soluble Phosphorus From Selected Animal Manures In Arkansas.

Water-soluble P (WSP) in animal manure is included in the Arkansas P Index used to assess the risk of P movement in developing nutrient management plans. There is limited information regarding the range of WSP in liquid swine manure (LSM) and various forms of poultry litter. Our objective was to characterize WSP and other chemical properties in these different manures from samples submitted to the University of Arkansas Agricultural Diagnostic Laboratory. Manure WSP was extracted using the 100:1 method and quantified using an inductively coupled plasma atomic emission spectrophotometer and manure total nutrient content was determined by digestion or combustion. Analytical data from 713 LSM samples from 2007 to 2011 and 504 poultry litter samples from 2010 to 2011 were summarized using descriptive statistics. Broiler litter comprised 68% of the total poultry samples and had mean (standard deviation) values of 260 (73) g H₂O/kg, 11.8 (2.5) g total P/kg, 2802 (776) mg WSP/kg, 32.3 (5.6) g total N/kg, 20.1 (8.1) g total Ca/kg, 278 (41) g total C/kg, 24.7 (4.7) g total K/kg, 10821 (3095) µS/cm, and 8.3 (0.5) pH. On average, WSP accounted for 24% of the total P in broiler litter. The relationship between WSP and total P (TP) in broiler litter was linear and had a significant, positive slope, but was weak (r²=0.22). The LSM had mean values of 12.5 (34.6) g solids/kg, 479 (1330) mg total P/L, 132 (173) mg WSP/L, 1167 (1176) mg total N/L, 511 (1712) mg total Ca/L, 765 (665) mg total K/L, 6908 (4495) µS/cm, and 7.8 (0.4) pH. For the samples having both WSP and TP, WSP accounted for 22% of the TP. Relationships between WSP and P or moisture/percent solids were weak and suggest that the use of standard values should not replace actual analysis in nutrient management plans.