设施甜瓜种植年限对土壤生物学特性和细菌多样性的影响

以广西北海市种植不同年限的设施甜瓜土壤为研究对象，研究甜瓜不同种植年限对其设施土壤的理化、生物学性状的影响和细菌多样性的演变规律。结果表明：随着种植年限的增加，设施土壤 EC 值随着设施种植年限的增加逐年增大，而 pH 值却随着设施种植年限的增加而下降，两者均以种植 3 a 后变化幅度增大；另一方面，设施土壤中可培养微生物的数量，以及涉及碳、氮、磷循环相关酶活性和微生物生物量（C、N、P）亦随着种植年限的增加而逐年下降，特别是种植 3 a 后的下降幅度表现出甚为剧烈的趋势；同时，设施土壤细菌多样性指数（H）、丰富度（S）和均匀度（Eh）指数亦随着设施栽培年限的增加而降低，同样表现出种植 3 a 后下降幅度加剧的趋势。此外，测序结果显示种植 3 a 后，设施土壤优势细菌种属主要以不可培养细菌为主；而且导致了诸如芽孢杆菌属、根瘤菌属等部分有益细菌种属的缺失。基于上述结果可知：施用化肥为主的甜瓜设施栽培连续 3 a 后易出现土壤肥力下降、质量劣化、发生盐渍化等危害。

Effect of Different Planting Years on Soil Biological Properties and Bacterial Diversity in Protected Cultivation of Cucumis melo L.

 melon were systematically investigated in Beihai, Guangxi in south China. The results showed that soil  electrical conductivity (EC) increased and soil pH decreased with more protected cultivation years. In particularly, soil EC and pH were significantly changed three years later under protected cultivation. In addition, the number of soil cultivable microbes, enzyme activities which related to the carbon, nitrogen and phosphorus cycles in soil and microbial biomass carbon, nitrogen and phosphorus were all decreased with more protected cultivation years, particularly three years later under protected cultivation condition. Meanwhile, soil bacterial diversity index (H), richness (S) and evenness index (Eh) in protected cultivation also showedthe same trend. Moreover, some bacteria groups, such as Bacillus(sp.) and rhizobia, which belonged to the beneficial microorganism, disappeared in soil after three years protected cultivation. Based on the above results, it indicated that the degradation of soil, such as soil fertility decline and salinization in southern China would easily happen with the application of chemical fertilizers only after three years under continuously protected cultivation.