Climate outweighs fertiliser effects on soil phoD-harbouring communities in agroecosystems

Alkaline phosphatase (phoD) gene-encoding bacterial (phoD-harbouring) communities are crucial for organic phosphorus (P) mineralisation in agroecosystems. However, the relative contributions of natural factors (e.g., climate) and anthropogenic influences (e.g., fertilisation) to these communities remain unclear, particularly at large spatial scales. To address this, we analysed phoD amplicon sequence data from 290 samples across 15 independent cropland studies, spanning diverse climatic zones and soil types from central to eastern Asia. Our results reveal that climatic factors exert stronger effects than fertiliser regimes on soil phoD-harbouring communities. Specifically, the richness of soil phoD-harbouring communities decreased by approximately three times as mean annual precipitation increased from 160 mm to 1800 mm, and mean annual temperature rose from 9°C to 18°C. Compared to the control, chemical nitrogen (N) + P + organic fertiliser doubled richness, while the control’s richness was 10 times higher than that of chemical N + P + potassium fertiliser. Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the most dominant phoD-harbouring taxa, collectively accounting for 65.3% of the relative abundance. Precipitation explained up to 96.3% of the variance in community composition, while fertiliser regimes explained approximately 40%. Notably, excessive potassium fertilisation was linked to reduced richness and abundance of dominant phoD-harbouring taxa, potentially limiting the availability of plant-accessible P. This suggests that the amount of potassium fertiliser should be carefully considered in future agricultural practices, as it may reduce plant-available P by inhibiting soil phoD-harbouring communities.