Relating High Soil Test Phosphorus Concentrations to Plant Phosphorus Uptake
1990
Yerokun, Olusegun A. | Christenson, D. R.
The median P soil-test concentration in Michigan has increased above the point at which a yield response is expected from fertilizer P application. This study was conducted to determine whether several soil-P extractants reflect plant P uptake under high residual soil P conditions and to estimate the reduction in soil-test P concentration as a result of crop removal. Initial P concentrations of the surface 0- to 15-cm layer of ten Michigan soils were determined with Bray-Kurtz P1, Bray-Kurtz P2, Olsen, and anion-exchange resin (AER) as extracting solutions. Ten consecutive crops were grown for 5 wk each on each soil. Phosphorus uptake by each crop was calculated from yield and composition. Linear correlation coefficients among the Bray-Kurtz P1 and P2, Olsen P and AER P methods ranged from 0.79 to 0.99. Linear correlation coefficients between initial test P concentrations and cumulative P uptake were from 0.40 to 0.74. The highest correlation was with the Olsen extractant and the lowest was with Bray-Kurtz P1 (1:20). A comparison of change in extracted soil-P content with P uptake showed that the Bray-Kurtz P1 extractant at a soil/solution ratio of 1:20 and the Bray-Kurtz P2 extractant most closely estimated the magnitude of P removed by plants. On the cultivated soils, there was a change of 0.13 to 0.31 mg P kg⁻¹ soil in the Bray-Kurtz P1 soil test for each mg P kg⁻¹ soil removed by plants. Contribution from Michigan State Agric. Exp. Stn. Journal Article no. 13055.
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