关键词: 盐碱地, 紫花苜蓿, 轮作模式, 土壤理化性质, 细菌多样性, 细菌群落结构

Abstract: To explore the improvement mechanism of soil environment and microbial community in saline‐alkali land by rotation systems of alfalfa（Medicago sativa L.） and salt‐tolerant gramineous crops，four planting patterns were established in the saline‐alkali land of the Ningxia Yellow River irrigation area，including continuous alfalfa cropping（M），alfalfa‐Hunan Jizi rotation（H），alfalfa‐maize rotation（Y），and alfalfa‐sorghum rotation（G）.The effects of different planting patterns on soil physicochemical properties and bacterial community diversity were systematically analyzed. The results showed that compared with continuous alfalfa cropping，all rotation patterns significantly reduced soil total salt content，as well as the contents of Na⁺，Ca²⁺，and Mg²⁺. Among them，the alfalfa‐sorghum rotation exhibited the optimal salt reduction effect，with the soil total salt content decreased by 79.2% compared with continuous alfalfa cropping. Rotation practices markedly increased the contents of soil availabl phosphorus，total phosphorus，and organic matter，and the alfalfa‐maize rotation showed the best improvement effect，with increases of 67.1%，38.3%，and 147.7% respectively relative to continuous alfalfa cropping. In terms of bacterial diversity，rotation patterns significantly improved soil bacterial richness，with a notably higher Chao1 index than that of continuous alfalfa cropping. Other alpha diversity indices were also superior to those of continuous cropping，though the differences were not significant.In terms of species composition，the relative abundances of Proteobacteria，Acidobacteriota and Actinobacteriota in soils with continuous alfalfa monoculture were all higher than those under rotation systems. Principal coordinate analysis（PCoA） further indicated that rotation enhanced the plasticity of soil bacterial community structure with a greater intra‐group dispersion. In conclusion，the rotation of alfalfa with gramineous crops could effectively improve the physicochemical properties of saline‐alkali soil and optimize the structure of soil bacterial community.Specifically，alfalfa‐sorghum rotation and alfalfa‐maize rotation present outstanding comprehensive improvement effects.

Key words: Saline‐alkali soil, Alfalfa（Medicago sativa L.）, Rotation pattern, Soil physicochemical property, Bacterial diversity, Bacterial community structure