Phosphorus use efficiency and management in agriculture

Phosphorus (P) is an essential element for all life, is essential for global food security, and is a limited, nonrenewable global resource, making its efficient use vitally important. There is a commonly held belief that P fertilizer is very inefficient because P recovery by crops in the year it is applied is often only 10-15%. The residual fertilizer P not recovered by the crop is believed to be permanently tied-up or “fixed” in the soil in forms not available to plants. However, field experiments do not support that view. The behavior of inorganic P in fertilizer when applied to the soil can be explained as contained in four pools of varying availability to plants based on its accessibility to plant roots and its extractability by soil test reagents. Phosphorus use efficiency can be assessed in several ways, but the “balance” method (i.e. partial nutrient balance) calculated as a P removal-to-input ratio and expressed as a percent best reflects the behavior of fertilizer P in soils and supports the concept of P transfer and availability within the four pools discussed. When determined by the balance method, P recovery is often in the range of 50-70% or even higher. Improving fertilizer P use and effectiveness is achievable through the implementation of fertilizer best management practices within the context of 4Rs—application of the right nutrient source, applied at the right rate, right time, and in the right place.