Phosphatase Activities and Available Nutrients in Soil Receiving Pelletized Poultry Litter

Abstract

Pelletization of poultry litter can impact availability of inorganic and organic nutrients. We compared the effects of incorporating pelletized poultry litter (PPL) and inorganic fertilizer Osmocote (OSM) applied at rates of 56 (low), 112 (medium), or 168 (high) kg phosphorus (P) · ha −1 on nutrient availability and enzyme activities in a high-P silt loam growing edamame throughout one growing season. Responses in the low rate treatments of both PPL and OSM generally did not differ from the untreated control. Medium and high application rates of both fertilizers increased water-soluble P and Mehlich-3 P and K compared with the control, whereas PPL increased extractable P concentrations compared with OSM, especially at the high rate. Inorganic nitrogen concentration was higher in OSM-than PPL-treated soil, especially as rates increased and during reproductive stages. The high rate of PPL increased dissolved organic C concentrations, but without a clear linear relationship between dissolved organic C and enzyme activities. Acid and alkaline phosphatase activities were higher initially in PPL treatments than the control and OSM-treated soil. Phosphatases in the high-rate PPL treatments were similar to or lower than the control at V5 to R6 stages and higher than OSM-treated soil at V5 and R6. We conclude that even under high soil test P, soil organisms will increase available P from PPL to an even greater extent than inorganic fertilizer, likely contributing to negative environmental consequences. Nutrient management incorporating PPL in soils should consider both nutrient concentrations and potential for mineralization to release organic nutrients.Least significant difference (LSD) and a critical value of P < 0.05 were used for means separation (n = 4 at T0 to R1, n = 3 at R6). *Low, 56 kg P · ha −1 ; medium, 112 kg P · ha −1 ; high, 156 kg P · ha −1 . CTL: untreated control; OSM: inorganic fertilizer Osmocote; PPL: pelletized poultry litter.