Tuesday, November 14, 2006

Organic Phosphorus Forms in Poultry Litter Amended Soil.

Thilini Ranatunga, Robert Taylor, and Byron Belvitt. Alabama A&M University, "Dept of Plt & Soil Sci, PO Box 1208", "Dept of Plt & Soil Sci, PO Box 1208", Normal, AL 35762, United States of America

Land application of manure has long-term effects on the phosphorus (P) levels in soils and is of high environmental concern. Application of organic waste in agricultural lands as nutritional sources can create changes in soil organic phosphorus (P) concentrations as well as the composition of soil organic P. Mineralization rates of organic P compounds in litter amended soil may depend on the composition of such compounds. This study was initiated to understand the distribution of various organic P forms in a Decatur silt loam soil amended with poultry litter at rates of 0, 100, and 200 lbs/hectare. Sequential organic P fractionation method was employed to isolate water soluble organic P, Fe-associated organic P, Ca/Al-associated organic P, acid soluble organic P, nucleic acid P and polyphosphates as well as sugar bound and humic acid bound organic P forms from poultry litter amended soil. Organic P fractions from soil samples (collected after one year of litter application) indicate that the highest amount of P present in soils (0-15 cm) comprise of Fe-associated organic P (185.9-266.2 mg/Kg) followed by Ca/Al-associated organic P (127.8-169.0 mg/Kg). The amount of Fe and Ca/Al-bound organic P present in soil is affected by the rate of poultry litter application. Acid soluble organic P in these soils ranged from 70-87 mg/Kg for 0-15 cm depth and 59-71 mg/Kg for 15-30 cm depth. Humic acid bound P ranged from 82-94 mg/Kg and 40-50 mg/Kg for 0-15 and 15-30 cm depths, respectively. Both acid soluble and humic acid bound organic P levels in these soils were not significantly affected by the rate of litter application during this period. Low amounts of water soluble organic P was also found in poultry litter amended soils as well as untreated soils.