Cultivation of perennial mixtures has emerged as an efficient way to produce a large amount of forage, supporting a sustainable livestock industry. The stability and sustainability of forage production is largely controlled by soil health. However, variation in soil health in perennial mixtures still needs further investigation under diverse conditions. Clarifying the relationships between soil physicochemical properties and microbial community is of great importance in better understanding soil health in perennial cultivated grasslands. The effects of mixing combination of alfalfa with timothy or smooth bromegrass on soil health were evaluated through comparing soil nutrients, enzyme activities, microbial community, and forage yield in alfalfa–grass mixtures and corresponding monocultures after seven years of establishment. Mixtures significantly increased forage dry matter yield by 61.39% and 1188.29% in the alfalfa–timothy mixture compared with alfalfa and timothy monocultures, respectively, and by 54.36% and 736.38% in the alfalfa–smooth bromegrass mixture compared with alfalfa and smooth bromegrass monocultures, respectively. Mixtures enhanced soil organic carbon, total nitrogen, nitrate nitrogen and ammonium nitrogen contents, and urease activity, but reduced microbial alpha diversity. Beneficial taxa, such as Bacillus, Paenibacillus, and Mortierella, were enriched. Soil nitrate nitrogen was identified as a key driver influencing bacterial functional composition, while soil organic carbon, ammonium nitrogen, water, alkaline phosphatase, and sucrase exhibited significant effects on fungal functional composition. This study demonstrated that alfalfa–grass mixtures enhance system productivity by improving soil physicochemical properties and reconstructing soil microbial community. It provides a theoretical basis from the viewpoint of soil health for establishing and managing sustainable cultivated grasslands.
Zhang et al. (Thu,) studied this question.