Net mineralizable soil phosphorus cannot be measured by non‐isotopic approaches

Abstract While radioisotopic pool dilution is widely regarded as the most reliable method for estimating soil phosphorus mineralization (P min ), high costs, low throughput, and safety requirements limit its use. We evaluated the potential of non‐radioisotopic approaches to estimating net P min by difference before and after aerobic incubation, analogous to potentially mineralizable nitrogen (N), using five common extractions (water, resin, Olsen, Bray‐1, and Mehlich‐3). Non‐radioisotopic methods generally failed to produce positive net P min rates (extractable P pre‐incubation > post‐incubation), ranging from 18% (resin) to 0% (Mehlich‐3) in the detection of positive net P min . When detected, positive net P min values measured as post‐incubation difference in extractable P were underestimated by a factor of 3 to 274 relative to net P min measured by the radioisotopic approach. These findings demonstrate that net P min cannot be estimated by difference in extractable P after incubation, and point to the necessity of radioisotopic approaches for accurate measurements of soil P min .