Objective  In order to provide scientific basis for improving soil quality, the variation characteristics of soil microbial biomass carbon (MBC) and nitrogen (MBN), water-soluble organic carbon (WSOC) and nitrogen (WSON) in greenhouse soil were studied under different proportions of earthworm casts instead of chemical fertilizers.

  Method  Based on the long-term located experiment of organic material replacing partial chemical fertilizer in greenhouse, the experiment consists of 6 treatments with cucumber as the tested material. They were 100% chemical fertilizer (CF100), 75% chemical fertilizer (CF75), 25% vermicompost substitute chemical fertilizer (VM25), 50% vermicompost substitute chemical fertilizer (VM50), 100% vermicompost substitute chemical fertilizer (VM100) and no fertilizer (CK).

  Result  The results showed that the variation trend of soil active carbon and nitrogen in 10-20 cm soil layer was similar to that in 0-10 cm soil layer, but slightly lower than that in 0-10cm soil layer. Among the three ratios of vermicompost to chemical fertilizer, VM50 was the most effective. The contents of MBC in soil of VM50 treatment increased by 66.46% (0-10 cm soil layer) and 76.02% (10-20 cm soil layer) than those of CF100 treatment, and the content of MBC in soil of each treatment was relatively high in full fruit stage of cucumber compared with CF100 treatment. Soil WSOC contents in VM50 treatment increased by 22.88% (0-10 cm soil layer) and 18.84% (10-20 cm soil layer) , respectively. VM50 treatment had a better effect on increasing MBN content in soil at the later growth stage. In 10-20 cm soil layer, the soil WSON content in each treatment was relatively high at the initial fruit stage of cucumber, and the soil WSON contents in VM50 treatment were 50.90% (0-10 cm soil layer) and 12.55% (10-20 cm soil layer) higher than those in CF100 treatment, respectively. Three ratios of vermicompost instead of chemical fertilizer could increase soil C/N, VM25 and VM50 treatments had a better effect on MBC/MBN reduction, which reflected the structure information of soil microbial community, and VM50 treatments had a better effect on WSOC/WSON.

  Conclusion  The earthworm casts were used as partial fertilizers in greenhouse soil, which would establish a theoretical foundation for scientific and rational fertilization in protected cultivation.