The impact of cover crop shoot decomposition on soil microorganisms in an apple orchard in northeast China

Mowing can facilitate the incorporation of cover crop shoots into soil and improve the properties of soils in apple orchards. This article evaluated how apple orchard soil responds to the decomposition of the shoot residues of three cover crops[native mixed herbs (NMS), red clover (RCS), and ryegrass (RES)] in terms of microbial metabolism and biomass, and discussed the relationships between microbial responses and shoot chemistry. The chemical composition of shoots was analysed and a buried bag experiment was carried out to simulate shoot decomposition in an apple orchard. The results revealed significant differences in the chemical compositions and shoot C:N ratios (NMS: 10.9, RCS: 19.1, and RES: 12.9) of the three cover crops. The decomposition of the cover crop shoots promoted microbial metabolism and boosted soil bacterial reproduction (increase in the biomass indicator muramic acid: 19.44, 124.15, and 14.83 mg kg(−1), respectively. But there are different types of effects on soil fungal reproduction (change in the biomass indicator glucosamine: 712.51, 887.45, and 103.97 mg kg(−1)), and they are obviously negative, significantly positive, and non-significant respectively. Thus, the native mixed herbs and red clover are preferable swards for better shoot enhancement in apple orchard.