Agricultural Phosphorus Management for Environmental Protection: A Review

Abstract

This review addresses research done over the past 40 years on different aspects of agricultural phosphorus (P) management for environmental protection. Inputs of P are essential for profitable crop production. Long-term application of P to agricultural soils has resulted in elevated levels of soil P. This accumulation may be desirable from an agronomic point of view but it represents a threat to freshwater quality. Indeed, P in runoff from agricultural land is an important component of non-point source pollution and can accelerate eutrophication of lakes and streams. Even very small amounts of P can raise the concentration above the critical value for eutrophication. Excessive eutrophication restricts water use for recreation, industry, and drinking due to the increased growth of undesirable algae and aquatic weeds. Current concerns facing the environmentally sound management of P in agriculture are similar worldwide and revolve around agricultural, economic, and environmental compromises associated with balancing productivity with environmental values. Agricultural P management strategies should be geared towards ensuring that P, a finite earth resource, is not wasted and those soils do not become so enriched with P that there is an unnecessary risk of too much P being mobilized to water from agricultural fields. Approaches, such as soil P testing and either P models or indices have been studied and implemented to mitigate agricultural P losses. Apparently, P indices are preferred instead of P models for this purpose because they are more flexible. A holistic management strategy is therefore suggested by using soil P testing in conjunction with either a P index or a P model.