Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 11, 1999
Publication Date: N/A
Interpretive Summary: Phosphorus solubility from dairy manure and cheese whey applied to a calcareous topsoil and to a freshly exposed calcareous subsoil was compared to phosphorus solubility in untreated topsoil and subsoil fertilized with recommended rates of commercial (triple-superphosphate). The phosphorus solubility in the high phosphorus application rate was more closely related to the phosphorus source than to the amount of phosphorus applied. The phosphorus applied with the dairy manure was more soluble than that added with the whey. These differences must be considered when predicting phosphorus leaching or movement with soil eroded from fields and into streams and rivers.
Technical Abstract: Irrigation induced erosion and land leveling decreases yields on about 800,000 ha of south central Idaho silt loam soils. Phosphorus availability is a production problem after topsoil removal. This study evaluated the effect of three P sources on soil P availability and solubility. A long term study was initiated on a Portneuf silt loam (coarse-silty, mixed, mesic, Durixerollic Calciorthids) by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips. Phosphorus treatments applied across the strips were conventional fertilizer (applied according to soil test), dairy manure and cottage cheese acid whey. All treatments increased the freshly exposed subsoil bicarbonate extractable ortho-P concentrations up to or greater than the topsoil which was adequate for crop production. The initial topsoil ortho-P solubility was along the beta Tricalcium Phosphate isotherm and the initial subsoil was below the beta Tricalcium Phosphate isotherm. The ortho-P solubility of the subsoil monocalcium phosphate (MCP) treatment remained below the beta Tricalcium Phosphate isotherm. The cottage cheese whey treatment increased subsoil P solubility up to the beta Tricalcium Phosphate isotherm and the manure treated subsoil ortho- P solubilities were between the beta Tricalcium Phosphate and OCP isotherms. Most ortho-P concentrations decreased from spring to fall and then increased over winter in the subsequent spring samples. Soil solution ortho-P concentrations decreased with time in the subsoil treatments except immediately following treatment applications. The topsoil solution concentrations varied from year to year but remained at about the same over the study period.