Predicting soil phosphorus uptake: Evaluating low‐cost chemical alternatives to DGT technology

Abstract

Soil phosphorus tests quantify specific fractions but fail to capture P kinetics that govern plant availability. Diffusive gradients in thin films (DGT) technology offers a dynamic measure of P mobilization, outperforming conventional extractions in predicting soil P supply. In this study, agricultural soils with varying P saturation were assessed using DGT at multiple deployment times and compared with standard extractions (ammonium‐acetate‐lactate [P‐AL], Olsen‐P, and CaCl ₂ ‐P). We evaluated adsorption isotherms and chemical parameters controlling P sorption to link kinetic insights with predictive models. Results showed that DGT‐derived labile P concentration (P _DGT ) was the single best predictor of plant P uptake ( R ²  = 0.88). While DGT's effectiveness is documents, our specific novel contribution is identifying that a combination of P‐AL, Al‐AL, and soil organic carbon matches DGTs precision ( R ²  = 0.90–0.92) for these agricultural soils. This finding demonstrates that low‐cost analyses can substitute for advanced DGT measurements without compromising precision. By integrating sorption characteristics and soil chemistry, our approach provides a practical framework for improving fertilizer recommendations while reducing environmental risk. These insights advance understanding of soil P dynamics and offer stakeholders an efficient alternative for predicting crop P uptake and yield response