连作怀牛膝根际土壤微生物区系及酶活性的变化研究

Variation of microbial flora and enzyme activity in rhizospheric soil under continuous cropping of Achyranthes bidentata

本文从适宜连作的作物研究角度,以连作两年和多年的怀牛膝根际土壤为研究对象,对其微生物区系及酶活性的变化作了对比研究。结果表明,连作两年和多年的怀牛膝根际土壤中细菌总数占绝对优势,其平均占有率分别为62.27%和89.46%;放线菌次之,平均占有率分别为37.59%和10.45%;真菌最少,分别占总菌数的0.15%和0.09%。随着连作年限的增加,细菌数量和比例明显增加;其中亚硝化细菌、反硝化细菌、好气性纤维素分解菌、硫化细菌的数量均明显增加。同时,种植牛膝能够显著增加脲酶、蛋白酶、蔗糖酶的活性,但长期种植会使这3种酶活性呈不同程度减弱,多酚氧化酶活性却明显增强。最后对牛膝耐连作的可能机理作了进一步探讨。

Achyranthes bidentata, a Chinese traditional herb grows best under continuous cropping, Thus an experiment was con- ducted to evaluate microbial flora and enzyme activity in rhizospheric soils that have been under continuous cropping of A. bidenta- ta for two and more than twenty years. The results show that bacteria is the most dominant species of microbial flora, accounting for 62.27% and 89.46% of total microbial flora numbers in the soil under continuous cropping ofA. bidentata for two and more than twenty years. Actinomycetes is the next dominant species, accounting for 37.59% and 10.45% , while fungi is the least dominant species, accounting for only 0.15% and 0.09% of total microbial flora numbers in the soil. As the number of years of continuous cropping increases, the number and percentage of bacteria linearly increase. Further analysis on the physiological groups of microbial flora shows that A. bidentata favors growth of nitrite bacteria, denitrifiers, aerobic cellulose-decomposers and sulphate-reducers. Moreover, A. bidentata increases urease, protease and invertase activities in the soil. However, continuous cropping of A. bidentata inhibites enzyme activity, though it increases polyphen-oxidase activity in rhizospheric soils. Finally, the mechanism of adptiness of A. bidentata to continuous cropping is disscussed.