Our recent study showed that plastic mulching improved soil water and heat conditions, and is good for the proliferation of microorganisms (Li et al., 2016), which may confirm that both PM + SL and PM treatments increased the MBC content in the 0– 20 cm soil layer compared to CK and SL (Fig. 3A,B). Many studies have confirmed a direct relationship between straw application and MBC (Hu et al., 2006; Rasul et al., 2006). We also found that both PM + SL and SL increased the MBC in the 20–60 cm layer significantly, since the straw incorporation increased the soil carbon source and provided nutrients for microbial propagation. This suggests that the effect of straw burial on MBC at greater soil