Green manuring shifted the effects of crop rotation on soil EEAs activities in the Loess Plateau of China

Green manuring and crop rotation are important management practices with the potential to reduce the dependence on mineral fertilizers and to maintain soil health. Soil extracellular enzyme activities (EEAs) serve as a proxy for estimating the availability and cycling of soil nutrients and thus widely used as biological indicators of soil health. However, the effects of green manure application under different crop rotations on soil EEAs remain unclear. Here, a 5-year field experiment (2015-2020) was conducted and two crop rotations were established in the Loess Plateau of China. Specifically, forage rape (Brassica napus L.) (R) or common vetch (Vicia sativa L.) (V) was cultivated during the fallow period (F) of monoculture system, winter wheat (Triticum astivum L.) (W). Aboveground biomass of R and V were harvest in September 2020 and 50% of the biomass was chopped and returned to the soil surface. Soil EEAs activities [β-glucosidase (BG), cellobiohydrolase (CBH), β-xylosidase (Xylo) (XYL), and N-acetyl-glucosaminidase (NAG)] at 0-5 cm were determined in September and October. Observed EEAs activities were strongly affected by the pattern of crop rotation and sampling time, with greater EEAs activities in W-V-W-V than in W-R-W-R in September. Whereas, EEAs activities was higher in W-R-W-R than in W-V-W-V in October, expert for BG that had no difference between two crop rotations. Overall, our study demonstrated that green manuring shifted the effects of crop rotation on soil EEAs activities in the topsoil in the Loess Plateau of China.

Keywords: Annual forage, Residue retention, Soil health, The Loess Plateau