Impacts of long-term drip irrigation on K-bearing mineral weathering and microbial potassium mobilization in arid cotton systems
Hongbang Liang, Feihu Yin, Jinzhu Zhang, Jihong Zhang, Yue Zhao, Tao Zhao, Na Zhao, Zhenhua Wang
Abstract
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. • Long-term drip irrigation alters K-bearing minerals and reshapes soil K speciation. • Drip irrigation drives staged shifts in rhizosphere bacteria and K functions. • K-solubilizing bacteria adopt mineral-specific strategies under long-term irrigation.