Wednesday, November 7, 2007 - 10:15 AM
318-4
Soil Phosphorus Buffer Capacity Is Dependent on Phosphorus Source and Soil Type.
In Wisconsin nutrient management regulations are phosphorus (P) based because of concerns with regard to surface water quality. This incubation study was conducted to gain a better understanding of P availability from different manures applied at varying rates of total P, as compared to fertilizer. The Plano and Withee silt loam soils used in this study were categorized as having a low soil test P (STP) level. Fertilizer (F) (0-46-0), two dairy slurries (DS1,DS2), two dairy semi-solids (DSS1, DSS2), swine slurry (S), and pelletized poultry litter (P) were applied in triplicate at 90, 180, and 270 kg total P2O5 ha-1. Samples were incubated at 25°C for 15 weeks and watered every week to maintain water content between 45 and 60% field capacity. Soils were subsampled at 1, 2, 4, 10, and 15 weeks and analyzed for Bray 1 extractable P. For both soils, as total P applied increased so did STP levels. Additionally, fertilizer increased STP significantly more than all other manure sources for all dates and rates. P buffering capacity (PBC) is the amount of P2O5, in kg ha-1, needed to increase STP 1 ppm. In general, PBC was greater for the Withee compared to the Plano soil for all P sources. After fifteen weeks of incubation, there was no difference in PBC between rates for a given source and soil. Comparisons of PBC between sources on each a soil at fifteen weeks showed PBC following the trend: DSS2>DSS1>DS2=DS1=S>>P=F and DS1=DS2=DSS1>DSS2=S>>P>F on the Plano
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