The R. solani populations in the 20-day soil samples from the CK2 and OF experiments were much higher than in the 0-day samples. This could have been caused by invasion of the cucumber seedlings by R. solani Q1 and subsequent assimilation of nutrients from the host. In contrast, the populations of R. solani in the 20-day soil samples from the N and BIO treatments were less than in the 0-day samples. These results indicated that the populations of pathogens in the soil could be reduced by biocontrol agents, according with the previous reports ( Ling et al., 2010 and Zhao et al., 2011) ( Fig. 6).