The growth-promoting effects of soil treatment with Trichoderma harzianum TH-1 on capsicum and their mechanisms were investigated in this paper.The results show that capsicum grows much better in the soil with Trichoderma harzianum TH-1 than in the soil without treatment.Compared with those without Trichoderma harzianum TH-1,the fresh weight of capsicum and the content of chlorophyll increase significantly with the average increase over 22.26%,and the nitrate-reductase activity in the capsicum leaves in soi...