An improved global database and model of plant available soil phosphorus

Plant-available phosphorus (P) is critical for plant production but can also be used an an indicator of P loss from soils and potential freshwater degradation. Global maps of plant-available P provide an overview of spatial patterns in plant-available P and are a critical input for various model applications, from agro-climate models to crop models. A previous map of Olsen P, the most widely applied soil test for plant-available P, was developed from ~575,000 observations, but informed by data biased toward Europe and North America. We present an updated and improved Olsen P dataset of 892,332 observations measured between 2000 and 2020. After filtering for consistent methods and depths we retained 42,034, greatly increasing geographic representation, particularly from Africa and Asia, and improving the balance of land uses sampled. Using these data, we applied a quantile random forest model with enhanced soil and land-use predictors to generate global grids (and maps) of the 20^th, 50^th and 80^th percentile of Olsen P for the 0-20 cm depth at 1 km² resolution. These data provide a more accurate, representative resource for assessing global patterns in fertiliser needs, modelling nutrient cycles, and evaluating potential freshwater P risks.