Objective The effects of rotation tillage on soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN) and enzyme activities were studied in wheat–maize rotation system in fluvo-aquic soil in Huang-Huai Plain, aiming for selection of suitable tillage system.
Methods Field experiments with split plot design were conducted in 2017 and 2018. The two main treatments were rotary tillage (RT) and deep tillage (DT) in wheat season, three sub-treatments were no-tillage (NT), inter-row subsoiling (SBR) and in-row subsoiling (STR) in maize season, making totally six treatments. The contents of soil organic matter, total nitrogen, available nutrients, SMBC and SMBN, and the activities of urease, invertase and neutral phosphatase in different soil layers were measured.
Results All the indexes decreased with soil depth in the two years but the indexes were not affected by the tillage modes in 40–50 cm layer. The deep tillage in wheat season and subsoiling in maize season did not significantly increased organic matter and total nitrogen contents in surface layer, but did in deeper layers. Rotary tillage in wheat seson increased available nutrient contents in 0–10 cm layer, while DT-SBR and DT-SIR treatment increased those in 20–40 cm soil layer. In 0–20 cm layer, the SMBC in RT treatments were significantly higher than those in DT ones, but in 20–40 cm layer, both SMBC and SMBN were significant higher in DT treatments than in RT ones, and with the highest SMBC (67.99 mg/kg) and highest SMBN (45.96 mg/kg) in DT-SIR. DT increased the ratio of SMBN/total N in 30–40 cm layer, but decreased the microbial entropy in surface layer (0–20 cm). Subsoiling in maize season brought higher soil enzyme activities than no-tillage did. The soil urease, invertase and neutral phosphatase activities were higher under RT-SBR and RT-SIR in 0–20 cm layer, while they were significantly increased under DT-SBR and DT-SIR in 20–40 cm layer.
Conclusions In the fluvo-aquic soil area of Huang-Huai Plain, during the experimental period, rotary tillage in wheat season and subsoiling in maize season could increase available nutrient contents in 0–10 cm layer and microbial biomass carbon in 0–20 cm layer, while deep tillage in wheat season and subsoiling in maize season could increase content of organic matter, total N, available nutrient, microbial biomass carbon in 20–40 cm layer. Deep tillage in wheat season also could improve the ratio of MBSN/total N and decrease the microbial entropy in 0–20 cm layer.
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