Abstract:Pot experiments were carried out to investigate effect of sterilization and application of amino acid fertilizer on growth of cucumber plants and soil microflora in a continuous mono-cropping soil. The soil which had been planted with continuous mono-cropping cucumber for 4 seasonal crops and had a severe continuous obstacle, was used in the experiment. The experiments had 6 treatments with 8 replicates for each treatment, including CK (Non-sterilized soil with no application of amino acid fertilizer), 0.5% AAF (Non-sterilized soil with the addition of 0.5% amino acid fertilizer based on soil dry weight), 1.0% AAF (Non-sterilized soil with the addition of 1.0% amino acid fertilizer based on soil dry weight)，S-CK (Sterilized soil with no application of amino acid fertilizer), S-0.5% AAF (Sterilized soil with the addition of 0.5% amino acid fertilizer based on soil dry weight) and S-1.0% AAF (Sterilized soil with the addition of 1.0% amino acid fertilizer based on soil dry weight). Uniform cucumber seedlings with two cotyledons were transplanted to pots (0.5 L, 400 g soil) at March 7, 2006, and harvested at May 10, 2006. The results obtained are listed as follows. Soil sterilization could improve growth of cucumber plants to greater extent, and, for example, SPAD value, plant height, leaf area and fresh weight of cucumber plants grown in sterilized soil were significantly higher than those in non-sterilized soil. The differences of cucumber growth between the sterilized soil and non-sterilized soil decreased with increase of AAF application, showing that the application of AAF could solve some problems coming from continuous mono-cropping system. SOD and POD activities in the leaves of cucumber plants grown in sterilized soil were higher than CK, but their activities became lower with increase of AAF application. CAT activities and soluble protein contents of all treatments in sterilized soil were significantly higher than those in non-sterilized soil while MDAs were significantly lower. The number of bacteria and fungi in sterilized soil was increased by 1.89-3.03 folds and 6.96-2.43 folds, respectively, compared with those in non-sterilized soil and the ratio of fungi to bacteria was significantly increased. In addition, Actinomycetes were slightly enhanced. The analyses of PCR-DGGE profiles showed that the number of bands on the lanes of DGGE profiles in sterilized soil was more than those in non-sterilized soil, with low similarities of DGGE profiles, and the diversities of soil microorganism in sterilized soil were increased compared to those in non-sterilized soil. The incidence of Fusarium wilt of cucumber plants grown in non-sterilized soil was up to 31.2%-68.8%, but no incidence in sterilized soil.