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Publication Date

1997

Location

Manitoba and Saskatchewan

Description

The effect of agropastoral systems replacing native savanna on microbially bound phosphorus (Pmic) in low P acid soils was investigated. Chloroform released P (PChl) was measured to estimate Pmic. In a long-term improved pasture experiment, PChl was higher in grass-legume (GL) than grass-only pasture (GO). Although the P balance was slightly higher in GO than in GL, available P contents followed the same trend as PChl suggesting that the presence of legumes enhances the maintenance of P fertility. In a rice-pasture system, PChl was higher than under rice monocrop indicating an effect of the cropping system on PChl that goes beyond P inputs, and includes factors such as soil cultivation, herbicide application and organic matter input. Pmic may not be seen as a factor competing for plant available P in these strongly P-sorbing soils, but as a rapidly cycling pool that protects P from sorption. The results suggest that Pmic is an important indicator of P fertility on low P acid soils.

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Effects of Agropastoral Systems on Microbially Bound Phosphorus in Low P Acid Soils

Manitoba and Saskatchewan

The effect of agropastoral systems replacing native savanna on microbially bound phosphorus (Pmic) in low P acid soils was investigated. Chloroform released P (PChl) was measured to estimate Pmic. In a long-term improved pasture experiment, PChl was higher in grass-legume (GL) than grass-only pasture (GO). Although the P balance was slightly higher in GO than in GL, available P contents followed the same trend as PChl suggesting that the presence of legumes enhances the maintenance of P fertility. In a rice-pasture system, PChl was higher than under rice monocrop indicating an effect of the cropping system on PChl that goes beyond P inputs, and includes factors such as soil cultivation, herbicide application and organic matter input. Pmic may not be seen as a factor competing for plant available P in these strongly P-sorbing soils, but as a rapidly cycling pool that protects P from sorption. The results suggest that Pmic is an important indicator of P fertility on low P acid soils.