Comparison of Phosphorus Uptake from Poultry Litter Compost with Triple Superphosphate in Codorus Soil

Received for publication January 8, 2004. Nutrient management plans require that fertilizer equivalents of manures and composts be used in determining the total nutrient application to soils. The P nutrient content of manure composts has not been studied as extensively as N. In a growth chamber study using 15-cm pots, a Codorus silt loam soil (Fluvaquentic dystrochrepts) with less than 10 mg kg^–1 Mehlich-3 extractable P was amended with poultry litter compost (PLC) or triple superphosphate (TSP) at rates of 0, 25, 50, 100, and 150 kg P ha^–1. Nitrogen was supplied to be uniform across all treatments, taking into account the N mineralization rate of PLC. Fescue (Festuca arundinacea Schreb) was grown and harvested three times over 103 d. Yield of fescue was curvilinear related to rate of amendment, but yield was not affected by PLC or TSP. Models describing yield changes with rate were different for TSP and PLC. Phosphorus uptake was statistically the same for both treatments, and a single quadratic equation described P uptake with rate. These data indicate that PLC added to soils on a total P basis provided the same amount of fertilizer equivalents as TSP. The use of composted manure as a N source narrows further the plant available N/P ratio from that recorded in manures because N is immobilized and P is not. To use manure compost as source of P, more fertilizer N would be required to satisfy crops needs than if manure was used as a P source.