The Influence Of Microbial Fertilizer On Bacterial Community Diversity Of Rhizosphere Soil And Root Growth Of Yunnan Tobacco 87

Tobacco is one of major commercial crops in China, and tobacco planting is the main financial source of tobacco farmers in Longyan district. In order to pursue higher output, people have applied a large quantity of fertilizers and pesticides, thus bringing serious soil environment problems such as soil acidification and hardening, drop of biological activity, low rate of nutrient utilization, heavy metal accumulation, etc., all of which result in constant degeneration of soil fertility of tobacco fields.As microbial fertilizer has various functions like improving biological activity of soil, increasing utilization rate of fertilizers, enhancing resistance of plants, improving soil physical and chemical properties, etc., application of microbial fertilizer in tobacco fields has become an effective method for many tobacco farmers to improve soil fertility. Studies show that microbial fertilizer can improve agronomic characters of tobacco plants, increase ratio of first-class tobacco and lighten plant diseases and insect pests. However, during application of microbial fertilizers, functional bacteria in them are influenced by original microbial populations in soil which results in instable effects of microbial fertilizers.In order to further confirm fertilizer efficiency and provide sufficient theoretical foundation for large-area promotion and application, study on the influence of microbial fertilizers on soil microorganisms:has vital theoretical and practical significance.This paper takes Yunnan tobacco 87 as tested material. The test adopts randomized blocks design with 5 dispositions and 3 repetitions. The test adopts drainage method to measure root volume of tobacco plants, uses chlorination triphenyl tetrazole (TTC) to measure root activity of each disposition in 4 growth periods. This paper uses terminal restrictive fragment length polymorphism (T-RFLP) technology to study the influence of microbial fertilizer on bacterial community diversity of rhizosphere soil and root growth of Yunnan tobacco 87 which is the main tobacco variety in Longyan district, and evaluate variation of bacterial community of rhizosphere soil, hoping to provide technical reference for sustainable development of sound tobacco production in Longyan tobacco district.Study results show that:dispositions that apply microbial fertilizers can increase agronomic characters such as plant height, effective number of blades, maximum leaf area, etc. within a certain scope. Their performances in spherical plant stage, vigorous growing stage, squaring stage and maturation stage are quite different, maturation stage is obviously higher than the contrast percentage, reaching 6.19～8.52%. There is little difference in number of blades of tobacco planting dispositions before and after spherical plant stage. Vigorous growing stage, squaring stage and maturation stage are obviously higher than contrast percentage. Vigorous growing stage is 5.2～7.3%, squaring stage is 6.3～8.9% and maturation stage is 5.2～6.1%. In addition, application of microbial fertilizers can increase the maximum leaf area. The difference percentage of all tobacco planting dispositions in maturation stage reaches 5.2～6.8%.In terms of root system, application of microbial fertilizers can promote root development of tobacco plants and increase root volume. With increasing application of microbial fertilizers, root volumes of all dispositions are on the rise in the whole growth period. From transplantation to spherical plant stage, the volume is small, and then it increases rapidly, tending to be stable in squaring stage and slightly increasing subsequently. During the whole growth period of flue-cured tobacco, root volumes of disposition B and disposition C both of which apply microbial fertilizers are higher than the contrast. In spherical stage, disposition B and disposition C are higher than the contrast respectively by 6.7% and 10.1%. Disposition C and the contrast present extremely significant level, disposition C is higher than disposition B by 3.1%, presenting a significant level. Root activities of all dispositions of flue-cured tobacco present unimodal curve variation. With progress of growing process, they present the tendency of increasing before and decreasing later, but peak values are quite different. Root activity of tobacco plants is on the increase in vigorous growing stage during which it reaches the peak value. With further maturation of tobacco plants, root activity gradually decreases. Root activity of disposition that applies microbial fertilizers is higher than the contrast during the whole growing period, it is higher than disposition A respectively by 13.6.%,26.2%,82% and 56.6% in spherical plant stage, vigorous growing stage, squaring stage and maturation stage, which indicates that application of microbial fertilizers can enhance root activity of tobacco plants.T-RFLP analysis results show that microbial fertilizes can increase the number of bacteria especially mycetozoan, actinomyces, firmicutes, etc. Analysis of bacterial community diversity and uniformity shows that during tobacco transplantation stage and vigorous growing stage, diversity and uniformity of soil bacteria applied with chemical fertilizers are slightly higher than soil applied with microbial fertilizers, but the difference is not that obvious; during squaring stage and maturation stage, bacterial diversity and uniformity of soil applied with microbial fertilizers are obviously increased. This study also finds through database comparison that application of compound microbial fertilizers can promote growth of mycetozoan and firmicutes, e.g., aerobic bacteria such as beijerinckia derxi, azospirillum brasilense, bacillus under mycetozoan; aerobic bacteria Burkholderia under firmicutes and facultative anaerobic bacillus coagulans, bacillus brevis, paenibacillus,etc. Therefore, application of compound microbial fertilizers can improve mass propagation of bacillus and nitrogen-fixing bacteria as well as other bacterial communities, thus increasing diversity index of bacterial communities.