Abstract: 【Objective】The microbial community structure was the important element of soil environmental quality in soil. The purpose of this study was to compare the influence of D123 and D125 wheat residues on the growth and rhizosphere microorganisms of watermelon in continuous cropping soil, the relation of Fusarium oxysporum f. sp. niveum and rhizosphere microorganism in soil, to provide a reference for ecological control about watermelon continuous obstacles and watermelon wilt disease. 【Method】The D123 and D125 wheat residues were smashed and mixed in the continuous cucurbites cropping soil. The growth index and yield of watermelon have been measured by conventional methods. Rhizosphere microorganism numbers were determined with a dilution plate method. Abundances of Bacillus and Fusarium oxysporum f. sp. niveum were assessed by real-time PCR. 【Result】The results showed that the vine length of watermelon was promoted after D123 and D125 wheat residues treatment, the fresh weight of over ground root and plant were increased significantly in the later growth stage (P＜0.05), and D125 was higher than D123. The yield per plant was increased after the stubble treatment but was non-significant. Stubble treatment increased the yield per plant of watermelon, but this difference was insignificant. With the statistics of the rhizosphere soil microorganism number, the bacterial population of D125 was remarkably higher than the D123 and control (CK) at 20 d after transplanting (P＜0.05), but the discrepancy was not significant between D123 and CK. D125 treatment bacterial population was remarkably higher than CK at 30 d after transplanting (P＜0.05), there was a non-significant difference between D123 and the CK, D125 and D123 (P＜0.05). The fungus amount researches show that D125＞D123＞CK each period, this rule shows a significant difference at 30 d after transplanting (P＜0.05). The research of Fusarium oxysporum f. sp. niveum number show that D125＞D123＞CK, D125 treatment is significantly higher than D123 and the CK at 30 d after transplanting (P＜0.05), but D123 treatment and CK had no remarkable difference. The B/F specific value had a declining curve along with the sampling period, the multiply speed of bacterial population was lower than fungus and Fusarium oxysporum. On 20 d after transplanting, the B/F specific value of D125 treatment was remarkably higher than D123 treatment and CK in rhizosphere soil (P＜0.05), D123 treatment had non-significant difference with CK. The amount of Fusarium oxysporum f. sp. niveum had a growth trend with the plant growth of watermelon, Fusarium oxysporum assume CK＞D123＞D125 in all periods, the data show that wheat residues significant reduce the amount of Fusarium oxysporum f. sp. niveum at 20 d and 40 d after transplanting (P＜0.05). The Bacillus data indicate that the amount of Bacillus reaching the maximum value at 30 d after transplanting, but it was lower in other periods. Wheat residues increase the number of Bacillus in rhizophere soil contemporaneity, D125 treatment outstanding higher than CK in each period (P＜0.05), and D123 treatment significantly greater than CK at 20 d and 30 d after transplanting (P＜0.05), D125 treatment was salience higher than D123 treatment on 20 d and 40 d after transplanting (P＜0.05), and it showed an adverse result at 30 d after transplanting. 【Conclusion】Wheat residues can promote watermelon growth, increase microbial numbers and the size of the beneficial microflora, and reduce the number of pathogens. Wheat residues can repair soils continuously cropping of watermelon.

Key words: watermelon, continuous monocrop, wheat residues, Fusarium oxysporum f. sp. niveum, Bacillus, microorganisms, community size