连作西瓜的根际土壤酶活性和微生物多样性

以山东大鹏西瓜基地0，3，9，15 a的西瓜根和根际土壤为研究对象，采用野外调查和实验室分析方法分析连作对西瓜根际土壤酶活性和微生物多样性的影响。结果表明:随着连作年限的增加，土壤有机质和氮磷钾含量递减，连作第15年有机质及有效氮磷钾含量最低。在同一生长时期内，连作年限越长，西瓜根系活跃吸收面积和总吸收面积最低，根际土壤酶活性呈现先递增后下降的趋势，并且根际土壤酶活力幼苗期 < 抽蔓期 < 结果期。在连作前期土壤中可培养微生物代谢活力递增，连作后期微生物代谢活力递减，且连作越久土壤中微生物群落多样性降低，均匀度先增加后降低。相关性分析表明，土壤中过氧化氢酶（p < 0.05）、磷酸酶（p < 0.05）、蔗糖酶（p < 0.01）、速效磷（p < 0.05）、速效钾（p < 0.05）与真菌具有正相关性；脲酶与细菌正相关（p < 0.01），与碱解氮负相关（p < 0.01）；过氧化氢酶（p < 0.05）、碱解氮（p < 0.01）与放线菌具有显著正相关。综上所述，连作0～9 a，土壤微生物代谢活力和酶活性增强，养分流失较小；连作9 a后，土壤养分流失严重，土壤酶活性和微生物代谢活力显著降低，产生连作障碍，说明减少连作年限可使西瓜优质丰产并且可持续发展，反之影响西瓜正常生长生产，损害经济效益。

Soil Enzyme Activity and Microbial Diversity in Rhizosphere of Continuous Watermelon Cropping

In order to improve the cultivation quality and provide reference for the high yield and excellent quantity and sustainable development of watermelon, the roots and rhizosphere soils with watermelone growths of 0, 3, 9 and 15 years which were marked as CK, CP₃, CP₉ and CP₁₅ were collected in Dapeng watermelon base in Shandong Province. Root activity, soil nutrients, soil enzyme activity and rhizosphere microorganisms were measured, and correlation analysis between them was carried out. It turned out that soil organic matter and the contents of nitrogen, phosphorus and potassium were decreasing and nutrients were losing with the duration of continuous cropping, the lowest was found in fifteen year of continuous cropping. At the same growth period, active absorption area and total absorption area of watermelon roots reduced respectively in long term continuous cropping. Rhizosphere soil enzyme activity showed a trend with the increase at first and decline later, and the activity was high in thefruiting period. Soil culturable microbial metabolic activity increased at the early stage of the continuous cropping, microbial metabolic activity reduced at the late stage, and the longer continuous cropping was, the less soil microbial community diversity was, evenness increased at first and reduced later. Correlation analysis showed that the soil catalase (p < 0.05), phosphatase (p < 0.05), sucrase (p < 0.01) and available phosphorus (p < 0.05), and available potassium (p < 0.05) had the positive correlation with the fungus. Urease had a positive correlation with the bacteria (p < 0.01), was negatively related to the alkali solution nitrogen (p < 0.01); catalase (p < 0.05), alkali solution nitrogen (p < 0.01) and actinomycetes had significant positive correlation. To sum up, a few years before continuous cropping, microbal metabolisms and enzyme activity had increased, continuous cropping obstacles did not occur. After 9 years, soil nutrient loss was serious, microbal metabolisms and enzyme activity significantly reduced, continuous cropping obstacles occurred. Reducing the time of continuous cropping could improve high yield and excellent quantity and sustainable development of watermelon, conversely affected the growth of watermelon, and lowered the economic benefits.