【摘要】 通过盆栽和田间试验表明，重迎茬大豆根际微生物数量变化的主要特征表现在细菌和放线菌数量减少，真菌数量增多，故Ｂ／Ｆ和Ａ／Ｆ比值明显下降，并随重茬年次的增加，其变化幅度增大。在重茬条件下连年施用氮磷化肥处理较不施肥处理，耕层（１５－２０ｃｍ）土壤细菌数量减少６０％，Ｂ／Ｆ比值下降４０％；但连年施用有机肥或秸杆还田的处理，使细菌和放线菌数量显著增加，同时也使真菌数量明显减少，故Ｂ／Ｆ和Ａ／Ｆ比值将相应提高。更多还原

【Abstract】 The show on pot experiments and field trials was :the number of Bacteria and Actinomyces decreased ,the number of Fungi increased ,so the ratio of B/F and A/F decreased significantly,with the increasing of continous cropping ,the extentof changing increased On the condition of continous and intermittent cropping ,comparing continous applying Nitrogen and Phosphorus with no fertilizer, the result was :the number of topsoil(15--20cm)Bacteria decreased by 60%,the ratio of B/F decreased by 40%;but continous applying organic fertilizer or return straw to soil , the number of Bacteria and Actinomyces increased significantly, on themeanwhile,the number of Fungi decreased ,so the ratio of B/F and A/F increased更多还原