Can We Improve the Efficiency of Phosphorus Use in Crop Production?.

Phosphorus (P) is essential for all living organisms but the global resource of P is limited. About 85% of currently-mined phosphate rock (PR) is processed for use in agriculture and it is here that the greatest scope for improving P use efficiency exists. Current thinking on the behaviour of inorganic P in soil indicates that phosphate ions are retained by soil components with a continuum of bonding energies. This has led to soil P being considered to occur in four operationally-defined pools based on its accessibility, availability for plant uptake, and its extractability by reagents used for routine soil analysis. Results obtained from field experiments, which allow an adequate evaluation of the residual effect of added P, indicate that the efficiency of P fertilizer use is often high (up to 90%), contrary to common thinking. Optimal P-use efficiency is achieved when soil P is increased to a critical level assessed by crop response and related to soil analysis. When the critical level is maintained by replacing the P removed in harvested crops, P-use efficiency approaches 100%.