application led to marked changes in the abundance of key nitrogen cycle-related genes (Fig. 1). For instance, genes involved in assimilatory and dissimilatory nitrate reduction pathways displayed elevated abun- dances under high-K treatments (K180 and K360) relative to the control (K0). Additionally, shifts in microbial functional traits associated with soil N transformations, as annotated by KEGG, showed treatment- specific clustering in the PCoA (Fig. 2A). PERMANOVA further indi- cated that K fertilisation significantly altered the KEGG Ortholog groups, capturing 66.0 % of the total variability (P < 0.05), whereas green manure amendment yielded no significant change, accounting for only 25 % (Fig. 2B). The combined application of K and green manure significantly increased the Shannon index of microbial α-diversity in the rhizosphere soil of potatoes (Fig S2). Among all treatments, the Shannon
diversity index was lowest in K0 and increased with increasing potas- sium fertiliser application, reaching its peak in K90M90. To investigate the compositional variations among different potassium fertiliser treatments, Principal Coordinate Analysis (PCoA) based on Bray-Curtis distance was used to visualise the differences in rhizosphere bacteria and fungi between treatments. The first coordinate axis explained
application led to marked changes in the abundance of key nitrogen cycle-related genes (Fig. 1). For instance, genes involved in assimilatory and dissimilatory nitrate reduction pathways displayed elevated abun- dances under high-K treatments (K180 and K360) relative to the control (K0). Additionally, shifts in microbial functional traits associated with soil N transformations, as annotated by KEGG, showed treatment- specific clustering in the PCoA (Fig. 2A). PERMANOVA further indi- cated that K fertilisation significantly altered the KEGG Ortholog groups, capturing 66.0 % of the total variability (P < 0.05), whereas green manure amendment yielded no significant change, accounting for only 25 % (Fig. 2B). The combined application of K and green manure significantly increased the Shannon index of microbial α-diversity in the rhizosphere soil of potatoes (Fig S2). Among all treatments, the Shannon
diversity index was lowest in K0 and increased with increasing potas- sium fertiliser application, reaching its peak in K90M90. To investigate the compositional variations among different potassium fertiliser treatments, Principal Coordinate Analysis (PCoA) based on Bray-Curtis distance was used to visualise the differences in rhizosphere bacteria and fungi between treatments. The first coordinate axis explained
