Some Aspects of Achieving Sustainable Phosphorus Use in Agriculture

The management of P in agriculture must maximize the benefit to producers and minimize any adverse environmental effects. The latter arise from the loss of P from soil to standing freshwater. Even very small amounts of P can raise the concentration above the critical value for eutrophication. Such small quantities can be lost in eroded soil, in surface runoff and in drainage water. The relative importance of these pathways depends on many factors, including topography, rainfall, farming system, soil characteristics, and the bioavailability of the P that is lost. The success of agriculture in increasing food production to meet the increasing needs of humankind, especially since the 1950s, owes much to the use of P in fertilizers and animal feeds. What is now required is to ensure that P, a finite earth resource, is not wasted and that soils do not become so enriched with P that there is an unnecessary risk of too much P being carried to water from agricultural soils. The concept of taking account of critical soil P values to optimize the use of P in both fertilizer and manures is discussed here.