Mining of soil legacy phosphorus without jeopardizing crop yield

Abstract Off‐site transport of excess soil P from repeated P fertilizer applications constitutes waste of a vital resource and poses an environmental risk. Excess P can be mined by growing crops without P addition until it is exhausted to the point of P deficiency. This study evaluated the utility of the “soil phosphorus storage capacity” (SPSC) as an indicator of safe P mining for acid soils. The SPSC predicts crop‐available legacy P in absolute terms, (i.e., kg ha−1; can be calculated from mg kg−1 if the bulk density and soil depth are known), which is not provided by current soil tests. Results show that mining provides sufficient P for crops when there is adequately negative SPSC. This study provides a “proof‐of‐concept” for SPSC, serving as an indicator of legacy P mining prior to the need for P fertilizer application. However, further study is needed to determine the negative P thresholds more precisely at which P mining would no longer provide adequate P for optimum crop yields.