Effects of Watermelon Replanting on Main Microflora of Rhizosphere and Activities of Soil Enzymes
西瓜连作对土壤主要微生物类群和土壤酶活性的影响

Soil samples collected from greenhouses with 6, 8, 10, 14 and 20 years watermelon replanting, respectively, in Changle, Shandong province were analyzed for number of bacteria, actinomycetes, and fungi, and soil enzyme activities, and pH, N, P, K, and organic matter contents in soil. Results showed that with year increasing of replanting, the number of bacteria and actinomycete showed a trend of increasing first and then decreasing afterward; the activities of proteinase and polyphenoloxidase had a similar trend as those of the number of bacteria and actinomycete; however, the trend of the number of fungi was totally opposite to that. As the replanting year increasing, the urease activity decreased, while the saccharase activity increased. Results also showed that the nitrogen content of replanting soil was not evidently changed, while the contents of P, K in the soil had a little accumulation after replant of watermelon. The relationship between microflora, soil enzyme activities, physical and chemical character in replanting soils was also discussed.