Impacts of long-term drip irrigation on K-bearing mineral weathering and microbial potassium mobilization in arid cotton systems

Potassium (K) availability in arid agroecosystems is strongly regulated by mineral weathering and microbial K mobilization. However, the effects of long-term mulched drip irrigation (MDI) on these processes remain unclear. This study investigated a chronosequence of cotton fields (0, 11, 15, and 25 years of MDI) on aridic gray desert soils to assess changes in K-bearing minerals, K fractions, rhizosphere bacterial communities, and K-solubilizing potentials. Total soil K remained stable, whereas non-specifically adsorbed and non-exchangeable K increased markedly along the irrigation gradient. K-feldspar consistently declined (∼13 % to ∼3 %), accompanied by a steady rise in illite (∼40 % to ∼56 %) and a reduction in illite–smectite mixed layers. Rhizosphere bacterial diversity decreased initially but later recovered, with community composition shifting from Actinobacteriota dominance toward increased Proteobacteria. Functional predictions indicated a transition from transport-dominated K-related genes at 0 years to stronger regulatory and ion homeostasis pathways at 11 years, followed by stabilization under prolonged irrigation. Although the abundance of cultivable K-solubilizing bacteria decreased, Pseudomonas aeruginosa persisted across all stages, and its K-solubilizing activity shifted from preference for K-feldspar to illite. Partial least squares path modeling revealed that K-feldspar dissolution was mainly constrained by functional genes, whereas illite weathering was strongly driven by mineral succession, microbial composition, and functional traits. These results demonstrate a coordinated “mineral–community–function” succession under long-term MDI, highlighting its role in redirecting microbial K mobilization from primary feldspars toward secondary clay minerals in arid cotton systems.