长期连作及秸秆还田对棉田土壤微生物量及种群结构的影响

通过采用常规微生物培养技术分析长期不同连作年限及秸秆还田棉田土壤微生物量及种群结构变化,揭示棉花连作及秸秆还田与土壤微生物多样性关系。研究表明,随着连作年限增加,秸秆还田连作模式下真菌数量持续增加,细菌和微生物总量在连作5-20 a逐渐下降,25 a后又上升;非秸秆还田连作模式随着连作年限增加其微生物种群变化与秸秆还田连作模式变化一致,但非秸秆还田连作模式土壤细菌和微生物总量分别比秸秆还田连作模式在连作5、10和15 a降低42.9%、57.9%、70.6%和41.9%、54.7%和65.7%,而真菌数量增加28.4%、80.8%和116.7%。说明棉花秸秆还田能够增加微生物数量,改善棉田土壤微生物种群结构。连作棉田土壤Simpson指数和Shannon指数呈随连作年限增加呈增加的趋势,连作棉田土壤微生物细菌/真菌（B/F）和放线菌/真菌（A/F）比值在秸秆还田模式下先逐渐减小至连作25 a有升高,而非秸秆还田模式下持续下降。

Effects of cotton continuous cropping and returning stalks to soil on the quantities and community structure of soil microbes

The paper was analyzed variation between the quantities of soil microbes and community structure under long-term continuous cropping of cotton, by using traditional microbiological culture technology, and revealed the relationship among continuous cropping, cotton stalks retttmed and soil microbial diversity. The results showed that bacteria and actinomycetes decreased in 5-20 years and increased after 25 years, while fungal colony-forming units （CFUs） increased with time under the model of returning stalks into field; Variations of quantities of cotton soil microbes between stalks returned and no-stalks returned are the same, but bacteria and the total quantity of soil microbes in 5, 10 and 15 years continuous cropping under no-stalks returned model, decreased by 42.9%, 57.9%, 70.6% and 41.9%, 54.7% and 65.7%, respectively, while fungal colony-forming units （CFUs） increased by 28.4%, 80.8% and 116.7%, respectively. Soil Simpson index and Shannon index increased with increasing years of continuous cropping. The ratio of bacteria and fungi （B/F） and the ratio of actinomycetes and fungi （A/F） decreased gradually with time, and then increased after 25 years under stalks returned, but decreased under no-stalks returned.