Phosphorus Removal From Swine Effleunt Treated Forage Production Systems.

An experiment was conducted to evaluate the effects of repeated annual applications of swine effluent in forage production systems on soil phosphorus (P) levels.  Located in the Great Plains region of Oklahoma swine effluent was added at N levels of 56, 168, and 504 kg N ha-1 to bermudagrass, buffalograss, orchardgrass, and wheatgrass. Phosphorus additions were approximately 3, 10 and 30 kg P ha-1, annually.  Soil P levels were reduced as function of biomass removal.  Forage species had no significant affects on the annual soil P levels which were reduced 9.6 kg ha-1 yr-1 from biomass removal.  Nitrogen applied resulted in significant increases in biomass production, which was strongly correlated to soil P removal (P>.0001).