Response of Manitoba soils to banding phosphorus with sulfate or carbonate salts

Abstract

Applications of sulfate and carbonate salts have been shown to improve the solubility of phosphorus (P) in model calcareous soils. It is unclear how these treatments will influence P solubility in real soils. The objective of this study was to determine the effect of sulfate or carbonate salts on P solubility in selected Manitoba soils. We hypothesized that the application of carbonate or sulfate salts in a fertilizer band could enhance the solubility of P in Manitoba soils. Different salt mixtures were prepared by mixing either monopotassium phosphate (MPP) or monoammonium phosphate (MAP) with K2SO4, (NH4)2SO4, MgSO4, or (NH4)2CO3. After the 2 wk of incubation of salt-treated soils, both P sources decreased soil pH significantly. The addition of salts did not significantly affect pH in most of the soils. There was a significant treatment effect (P < 0.0001), a significant soil effect (P < 0.0001), and a significant soil by treatment interaction (P < 0.0001) on water-extractable P. Coapplication of either sulfates or (NH4)2CO3 salt increased soluble P in some soils by 6%-44% or 11%-14%, respectively. Application of carbonate or sulfate salts increased P solubility only in soils with a smaller ratio of HCl-extractable Ca to ammonium acetate-extractable Ca.