Effect Of Conservation Tillage On Soil Micribial Diversity And Cellulose Degrading Bacteria In Taihu Region In Paddy Field

Conservation tillage is a modern farming technology system. Straw returning, minimum tillage sowing, deep plowing and insect pest integrated control are as the main content of it. Advocating for and implementing conservation tillage to improve soil quality and ecological environment is significant. At the same time we also recognize that the cellulose-degrading bacteria play a very important role in the degradation process of straw.The experiment was carried out in2010and2011at the Agriculture Science Institute of Taihu, Jiangsu with three cropping patterns (wheat-rice, ryegrass-rice, rape-rice), two modes of tillage and two modes of crop straw returning to field, hence forming12experimental treatments. We studied the following contents:the dynamic effect of the number of cellulose-degrading bacteria under conservation tillage, the dynamic effect of the microbial community structure. At the same time we screened three cellulose degrading bacteria, and made a preliminary study of the one about the cellulase gene. The main findings are as follows:1. Six DGGE profiles of bacterial and fungal were analyzed in three periods. Compared with minimum tillage and zero tillage mode, conservation tillage showed the advantages in the soil bacterial and fungal diversity in the vast majority of cases. Under a individual model at a individual period it can not show the advantage. One of the reasons may be is that a band is to be understood as the dominant bacteria to a certain extent. Some of the bands did not exist, which may be at a disadvantage on the number and could not be reflected in the map.2. The number of cellulose degrading bacteria under12processing mode of the three periods was counted and analysted. Compared with minimum tillage and zero tillage patterns, it showed that there is increase of the count of cellulose degradation bacteria by implementing conservation tillage in most cases, which can not show to advantage under a individual model at a specific period. In each mode, the straw mulch could significantly improve the number of cellulose degrading bacteria.3. Three cellulose degrading bacteria were screened and identified.They are:Bacillus, Streptomyces, Brevibacillus. Then we designed primers, amplified the endoglucanase gene, used the BLAST to make a homology identification. It turns out that the homology reach99%with the strains of Bacillus cellulase gene which had been reported.