大豆与烤烟不同套作年限对根际土壤微生物数量的影响

为克服烟田连作障碍、提高烤烟产量和质量,以大豆套作烤烟为种植模式,调查大豆与烤烟不同套作年限下根际土壤三大类群微生物和与氮代谢相关的功能性微生物群落的数量变化及其与烤烟主要土传病害的发生情况之间的相互关系。结果表明,烤烟-大豆带状套作显著增加作物根际土壤的细菌(B)、放线菌(A)数量、B/F和A/F值,减少真菌(F)数量;也提高与土壤氮素代谢相关的氨化细菌、硝酸细菌、亚硝酸细菌、自生固氮菌等功能性微生物数量;烟豆套作能降低烤烟主要土传病害的发生,其发生程度与烤烟根际土壤细菌及放线菌数量显著负相关,而与真菌数量极显著正相关。随着套作年限的延长,根际土壤的细菌(B)、放线菌(A)、B/F和A/F值以及氨化细菌、硝酸细菌、亚硝酸细菌、自生固氮菌等有益菌群数量大幅度增加,真菌(F)及反硝化细菌的数量显著减少,对烟草土传病害的相对防治效果明显提高,以上效应表现为烤烟-大豆带状套作3年(A3)烤烟-大豆带状套作2年(A2)烤烟-大豆带状套作1年(A1)。

Effects of Relay Strip Intercropping Years between Flue-cured Tobacco and Soybean on Rhizospheric Microbes Quantities

To overcome obstacles from continuous tobacco cropping and improve the yield and quality of flue-cured tobacco, we studied the effects of flue-cured tobacco and soybean relay intercropping years on the population changes of three classifiable microorganism and functional microorganisms related to nitrogen metabolism in rhizospheric soil, and their relationship with the occurrence of major soil-borne disease of flue-cured tobacco in this research. Results showed that the flue-cured tobacco-soybean relay strip intercropping markedly increased the population of bacteria (B), actinomycetes (A), B/F, and A/F, while reduced the fungi (F) quantity in rhizospheric soil. Meanwhile, the flue-cured tobacco-soybean relay intercropping enhanced the quantity of functional microorganisms related to nitrogen metabolism, such as ammonifier, nitrobacteria, nitrite bacteria and free-living nitrogen fixing bacteria. In addition, it alleviated the occurrence level of soil-borne disease of flue-cured tobacco, and the severity indexes of soil-borne disease had significantly negative correlation with the quantities of bacteria and actinomycetes respectively, but were positively correlated with the increasing of fungi. With increasing the number of years for relay intercropping, the quantities of bacteria (B), actinomycetes (A), and value of B/F and A/F, ammonifier, nitrobacteria, nitrite bacteria and free-living nitrogen fixing bacteria were raised largely, while the quantities of the fungi (F) and the denitrifying bacteria were significantly declined, and there was a marked improvement in the relative control efficiency to soil-borne disease of flue-cured tobacco. These effects showed a trend of flue-cured tobacco relay strip intercropping with soybean for three years (A3) > that intercropping for two years (A2) > that intercropping for one year (A1).