Spatial patterns and key drivers of available phosphorus in Yunnan tea plantation soils

Soil fertility, particularly phosphorus (P) availability, is vital for tea yield and quality. However, as tea is a leaf-harvest crop with high nitrogen (N) demand, P nutrition is often overlooked in tea plantations, with more attention typically given to N fertilization. This study assessed the spatial distribution of available phosphorus (AP) and its influencing factors across Yunnan's tea plantations. Large-scale soil sampling was conducted across eight cities covering central, western, and southern Yunnan, encompassing modern and ancient tea plantations under conventional and organic farming. The approach showed that soil AP content (15.82 mg kg^-1) in these regions was lower than in other tea regions of China, and 56.4% of those samples were severely P-deficient (≤3 mg kg^-1). The regions exhibited significant variations in soil AP levels, and central Yunnan and modern tea plantations had relatively higher AP levels. Mixed-effects modeling revealed that soil chemical properties accounted for 95.74% of the variation in AP among plantations in these regions, while elevation indirectly influenced AP through its effects on pH and soil organic carbon, Ca, Mg, Mn, and Zn contents. Our subsample analysis also found that in these soils, P primarily occurred in organic forms, and that low-AP soils (95.23%) had greater organic P accumulation than high-AP soils (73.53%). These findings provide insights into the AP status of Yunnan's tea soils and offer a foundation for sustainable fertility management. The study also recommends targeted P management strategies, including the combined use of organic and inorganic fertilizers and intercropping with green manure crops, to mitigate soil AP deficiency.