Microorganism Diversity Of Mollisols In Different Rotation Systems

Soil is the main(?)living environment of microorganism. Physicochemical character of soil affects the varieties and numbers of soil microorganism directly. Soil managements, expecially rotation system, can affect soil microbial diversity and activity through affecting the physicochemical character of soil indirectly. Continuous cropping can reduce the activity of phosphatase and urease in soil, and decrease effective nutrient of soil, and then affect the growth of crop, resulting in continuous cropping obstacle. Rotation can promote soil bio-chemical processes and improve soil enzyme activity. Besides, rotation can also alter soil microbial distraction with changing of microbial structure. There was little study of more than twenty years continuous cropping affecting soil microbial diversity. In order to discuss the variations of the microbial diversity under different rotation systems in black soil, based on the long term experimental field at Hailun Agro-ecosystem Experimental Station of Chinese Academy of Sciences, four kinds of test methods including DGGE, PLFAs, BIOLOG and Real-time PCR were applied to study the microbial diversity under21years soybean continuous cropping, rotational cropping(wheat-corn-soybean), normal rotation(corn-soybean) and bare land treatments. This is mainly to evaluate the effect of rotation system on soil microecology.The DGGE result of soil microbial community under different rotation systems showed that, rotational cropping enhanced the abundance and diversity of soil microorganism. And soil microorganism diversity was the highest at the flowering stage, it was3.565; decreased at seed-filling stage, it was3.437; and rose again at maturing stage, it was3.570.The research of soil microorganism population structure diversity indicated that, with the growth of soybean, the charaeteristic fat acid of fungi and bacteria changed regularly, and the fat acid was the lowest at seed-filling stage. The lowest PLFAs of bacterium was3787.3ug/g dry soil, fungi was134.5ug/g dry soil. Under rotational cropping, bacteria/fungi was always the highest, and the highest was33.1, so we declared that bacterium was at dominant position under rotational treatment compared to other treatments, and rotation improved soil quality. The result of soil microorganism functional diversity indicated that the ability of utilizing carbon source of soil microorganism in rotation system was different. Compared to other treatments, Shannon and Simpson index under rotational cropping were higher.The quantification of soil bacteria and fungi indicated that there was no significant difference between rotational cropping and continuous cropping(P>0.05). Rotation can better soil ecological environment, increase microbical diversity, and improve the yield and quality of crop. So this study explained the variation of soil microbial population and quantity, and the indirect influence of rotation system, for playing a part in effective utilization of soil and sustainable development of agriculture.