Global-scale patterns of bioavailable soil phosphorus driven by agricultural fertilization.

Phosphorus is essential for plant metabolism and growth. Bioavailable phosphorus (resin-extractable phosphorus) is the soil phosphorus available for plant uptake. However, the global response of bioavailable phosphorus to fertilization remains unknown, hindering efficient nutrient management for crops. In this study, we developed a data-driven machine learning model to map global bioavailable phosphorus post-fertilization. The robust accuracy of the model was validated (coefficient of determination = 0.76), and phosphorus application and soil depth were identified as the primary drivers governing bioavailable phosphorus. Fertilization type was found to play a crucial role, with nitrogen fertilization decreasing global bioavailable phosphorus by -1.65 mg/kg (10%) and phosphorus fertilization increasing it to 6.20 mg/kg (37%). Nitrogen fertilization resulted in the greatest decline in bioavailable phosphorus in croplands (-2.52 mg/kg), and phosphorus fertilization led to the largest increase in wetlands (7.63 mg/kg). These findings provide critical insights into the global distribution and drivers of bioavailable phosphorus, offering a valuable tool for region-specific strategies and advancing sustainable agriculture.