Factors affecting the uptake of phosphorus by plants

A study has been made in a series of 16 field experiments of the recovery by the turnip crop of the phosphorus applied in various phosphatic fertilizers, superphosphate at two rates (0.33 and 0.66 cwt. P₂O₆ per acre) being used as a standard. The recovery of phosphorus varied from less than 5 to almost 40%; it was nearly always greater from superphosphate than from other fertilizers and it was nearly always greater from the low than from the high rate of phosphate application. The soil properties which were most closely related to the percentage recovery were exchangeable calcium and citric‐soluble phosphate, the correlation coefficients being slightly above and slightly below the 2% level of significance respectively. These soil properties were quite unrelated to each other. Summer rainfall was also found to exert a considerable influence on the recovery of the phosphorus added; the partial correlation of recovery and exchangeable calcium, eliminating summer rainfall, reached the 1% level of significance.