Effects Of Tillage Modes On Soil Microbes And Enzyme Activity In Rhizosphere Of Broad Bean

The broad bean is one of the important upland crops in purple hilly regions of southwest China. The field trial was conducted in the experimental field in Southwest University in Beibei, Chongqing.There were six treatments including T (traditional tillage), R (Ridge tillage), TS1 (Traditional tillage+half amount of straw mulching), RS1 (Ridge tillage+half amount of straw mulching), TS2 (Traditional tillage+whole amount of straw mulching), and RS2 (Ridge tillage+ whole amount of straw mulching).The effects of tillage modes on soil microbes(bacteria, fungi, actinomycetes),enzyme (catalase, urease, polyphenol oxidase, invertase and acid phosphatase)activitiesin rhizosphere, the yield of broad bean, and the correlation between them were studied, so as to provide the reasonable farming methods for production practice of broad bean.The main results were as follows:1. The ridge tillage and the straw mulching could obviously increase the soil moisture; and the straw mulching at the low temperature with the "warming effect", at the high temperature with the "lowing effect". The more the straw mulching quantities, the more obvious the effect.2. The ridge tillage and the straw mulching could improve the broad bean soil microorganism quantities. But the rhizosphere microorganisms were greater than the non-rhizosphere microorganisms in general. Bacteria was the largest number of microorganisms, followed by the actinomycetes, again for the fungus.The number of the soil microorganism at the beginning of the broad bean growth gradually rose, following in the branching period rapidly rising, reached the maximum at the podding stage, and then declined in the mature period. The trend of microbial quantities between the various processing basic was characterized by RS2>TS2>RS1>TS1>R>T.3. The ridge tillage and straw mulching could improve the broad bean soil enzyme activity. But the rhizosphere soil enzyme activity was greater than the non-rhizosphere soil enzyme activity in general. The trends of all kinds of enzyme activities with the growth of broad bean at different developmental periods under different tillages were same as the microorganisms’.The catalase, urease, polyphenol oxidase were characterized by RS2>TS2>RS1>TS1>R>T, and the invertase and acid phosphatase were characterized by RS2>TS2, RS1>TS1, R>T; RS2>RS1>R, TS2>TS1>T.4. The ridge tillage and straw mulching could improve the broad bean yield and soil organic carbon content. The broad bean plant height, yield, hundred grain weight and the soil organic carbon content under different tillage methods were characterized by RS2>TS2>RS1>TS1>R>T. And the broad bean yield under the RS2 tillage was biggest, reached 3769 kg/hm-2. And the soil organic carbon content was increasing slowly with the growth of broad bean. The rhizosphere soil organic carbon content was also bigger than the non rhizosphere soil organic carbon content.5. Soil microorganism, soil enzyme activity, and broad bean yield were wholly positively correlated each other. While the correlation between actinomyces and urease, and that between urease, acid phosphatase, polyphenol oxidase and yield of broad beanl were significant, the correlation between other soil microorganisms, other soil enzyme activities and yield of broad bean were wholly very significant.