Effect of different cultivation systems on the soil microbial carbon and nitrogen amount and the yield of cucumber in greenhouse

In this study, the soil used for the pot experiment was collected from 8\|year continuously planted cucumber field in greenhouse. Five rotation ways were designed: early spring cucumber-fallow in the summer-autumn cucumber (CK), early spring cucumber-fallow in the summer-garlic intercropped within autumn cucumber (CS1), early spring cucumber- summer crown daisy-autumn cucumber (CS2), early spring tomato-summer spanich- autumn cucumber (CS3) and early spring cucumber-summer garlic-autumn cucumber(CS4). The pot experiment was carried out for 5 years and the soil samples in the latter three years were collected to analyze the contents of soil microbial biomass C (MBC), and microbial biomass N (MBN), and the crop yield was recorded at the same time. The results show that compared with CK, the MBC, MBN contents and the ratio of MBC/MBN with treatment CS3 are significantly increased in the early spring of the third and fourth year, and MBC and MBC/MBN of CS2 and CS3 significantly increased in the summer from the third year to the fifth year. With treatment CS2, the yields in the early spring and the early spring plus autumn were increased significantly from the third year to fifth year. With treatment CS4, the yields increase was in the early spring and the early spring plus autumn and winter crops in the third and fourth years, and in the autumn winter season crops from the third year to fifth year significantly. Obvious positive correlations exist between the MBC and MBC/MBN ratio and the yields of the autumn winter season crops, and extremely significant with the yields of the early spring season crop and the autumn winter season crops. Rotation ways, seasons and their interaction have extremely significant effect on the MBC contents and the ratios of MBC/MBN. The yields are heavily affected by treatments, seasons, and treatmentseason. Rotation of CS2 shows the optimal effect in increasing MBC, MBC/MBN, and the crop yield.