The uptake of phosphorus by wheat and clover from four inorganic soil phosphate fractions after the addition of contrasting types of phosphatic fertilizer

Summary

Basic slag, calcinated rock phosphate, monocalcium phosphate and rock phosphate were applied to acid, clay-loam soil at rates of 0, 50 and 100 ppm P. Yield response was assessed using subterranean clover and residual values using clover or wheat. Basic slag and monocalcium phosphate were equally efficient in producing increased yield in the first period and basic slag slightly better during the residual phase. Calcined rock phosphate was slightly inferior to rock phosphate at first, but was equal during the second stage: both were markedly inferior to the other two fertilizers when clover was the crop.

The soil phosphorus was fractionated by a modified Chang and Jackson procedure. There were shown to be significant differences in the forms of phosphate used by the different species and by the same species at different times. It was concluded that the better residual value of basic slag can, in part, be ascribed to the greater solubility of the residual fertilizer in the soil over the reaction products of fertilizer and soil.