Mulching and legume rotation changed soil microbial community and structure, which was beneficial to the improvement of soil quality in semi-arid potato continuous cropping system

Continuous cropping of potato (Solanum tuberosum L.) leads to reduced yield, quality deterioration and soil degradation, and these negative effects can be alleviated by mulching and crop rotation. Mulching improves soil hydrothermal conditions, while legumes improve soil nutrient status through nitrogen fixation, which affects crop growth. However, the mechanisms of soil nutrient and microbial improvement by mulching and legume rotation have been rarely reported. Field experiments were conducted to investigate the changes in soil properties and microbial community composition in response to the mulching method and rotation under six cropping patterns: potato continuous cropping without film mulching (PC), potato continuous cropping with film mulching (PCF), potato broad bean rotation without film mulching (R1), potato broad bean rotation with film mulching (R1F), potato pea rotation without film mulching (R2) and potato pea rotation with film mulching (R2F). The results showed that the soil of R2F had significantly higher alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), organic matter (OM), total carbon (C) and total nitrogen (N) contents and carbon-nitrogen ratio (C/N) than PC, while reducing soil pH and electrical conductivity (EC). The ACE, Shannon index of R2F soil fungi was significantly higher than other treatment, and the beta diversity of bacteria and fungi differed significantly among treatments. The dominant bacterial phylum included Proteobacteria, Bacteroidetes, Acidobacteria and Actinobacteria, and the dominant genera were RB41, Sphingomonas and UTCFX1. The most abundant fungal phylum was Ascomycota, with the dominant genera being Botryotrichum, Mortierella and Plectosphaerella. R2F significantly increased the relative abundance of the dominant bacterial Proteobacteria and fungal Basidiomycota, while PC significantly increased the relative abundances of the bacteria Acidobacteriota, and R2F had significantly less fungal and bacterial biomarkers than PC. Amino Acid Metabolism and Carbohydrate Metabolism were the main secondary metabolic pathways for soil bacteria, Pathotroph-Saprotroph-Symbiotroph and Saprotroph were the major metabolic pathways for fungi under each treatment. Redundancy analysis (RDA) indicated that the soil microbial community was mainly influenced by EC, AN and AK. Person correlation analysis showed that soil EC was positively correlated with Sphingomonas and Terrimonas, while significantly negatively correlated with Clonostachys, Stachybotrys, and Chaetomium.Overall, the properties of potato rhizosphere soil changed after continuous cultivation, and crop rotation significantly improved soil nutrient status, influenced soil fungal community diversity index, and improved microbial community structure. Thus, the legume-potato rotation improved the soil environment by maintaining higher soil fertility and a healthy microbial ecosystem.