Diversified crop rotation with no‐till changes microbial distribution with depth and enhances activity in a subtropical Oxisol

Abstract Soil microbial community and enzyme activity regulate carbon and nutrient cycling in soils. No‐till has elevated levels of carbon at the soil surface compared to intensively tilled soils. The introduction of crop diversification in agricultural systems increases soil carbon protection and aggregate stability. Thus, the association of no‐till with crop diversification may change the soil microbial distribution and enhance activity in comparison with tilled soils with no crop diversification. We tested this hypothesis assessing the soil microbial community and enzyme activity in a long‐term (32 yr) experiment with contrasting soil management (no‐tillage, (NT) and conventional tillage (CT)) and cropping systems in southern Brazil. Long‐term NT increased microbial biomass at 0–5 cm. In contrast, soil microbial biomass was higher in deeper soil layers (10–30 cm) of CT. No‐tillage and crop diversification increased the activity of β‐glucosidase, acid phosphatase and N ‐acetyl‐glucosaminidase. The benefits of an intensified/diversified crop rotation were offset by soil tillage. The higher abundance of PLFA groups at 0–5 cm and 10–30 cm of respective NT and CT soils were correlated with increased C and nutrient levels (N, Ca 2+ , Mg 2+ ) and decreased Al 3 + . Highlights Crop diversification increased the soil microbial biomass and individual PLFA groups. No‐till without crop diversification did not change microbial biomass. No‐till with crop diversification increased enzyme activity. Subsoil fertility restricted microbial responses in a no‐till Oxisol.