The increased use of rotation, grafting, and soil sterilization has been documented to increase crop yield in intensive vegetable production systems in China. It is believed that these practices can promote changes in the rhizosphere that enhance early growth of plants. A 2-year greenhouse experiment on tomato double-cropping systems was conducted to investigate the effects of different agricultural treatments on microbial properties of rhizosphere soils and tomato fruit yield. The treatments included planting of welsh onion as a cover crop in the summer fallow (SF) period (CW), rotating vegetable chrysanthemum and tomato (CT), planting graft-tomato instead of auto-root tomato (GT), sterilizing soil with calcium cyanamide in the SF period (TC), and fallowing in the SF period (Control). Microbial population was analyzed by dilution plating. In general, microbial populations were higher in CT, CT and TC than in control. Fungal population was higher in TC whereas a high number of bacteria were found in CT. Soil microbial biomass C and N, total microbial population, organic C and total N showed significant positive correlations (P
