Effects Of Fertilization And Straw-returning On Microbial Diversity Of Cotton Field Soil In Arid Region

Soil microbial diversity is closely related to soil function, which making contribution to keeping dynamic balance of soil. Vegetaton in arid region of Xin Jiang is sparse, the system of oasis farmland is weak, it would make soil ecosystem worse, organic matter absent and deteriorate soil environment result from ill management, therefore, to study the effects of methods of fertilization and straw-returning on agricultural soil environment is significantly meaningful. This research designed location-split plot experiment, choosing to take soil samples before sowing, full bloom and harvest to determine soil pH, microbial biomass carbon(MBC), enzymes activities and bacterial community structure and microbial functional diversity under straw-returning and fertilization, analyze the effects of different treatments on the composition of bacterial community and microbial functional diversity. The results showed :For soil pH, MBC and enzyme activities there were significant responses to different fertilizers and straw-returning:(1) Management of straw returning increased soil pH, and compared with NF, the optimal fertilization method was combined application of chemical fertilizer and organic fertilizer(2) With straw-returning, MBC increased remarkable;The best deal of fertilization was chemical and organic fertilizer dispensed, making MBC the highest,and soil MBC in 0-20 cm is significantly higher than in 20-40 cm during every period(3)With straw returning method, the enzyme activity of Urease and Invertase increased notably and enzyme activities turned out to be the highest under chemical fertilizer with manure,followed by fertilizer or manure separately(P<0.05), but there was no manifest difference between chemical fertilizer and organic fertilizer(P>0.05),the results of soil enzyme activities in different periods is 0-20 cm enzyme activity was significantly higher than 20-40 cm,especially in flowering(P<0.01)(4) It was said that the method of straw-returning with chemical and organic fertilization mixed strongly enhanced the ability of microbial taking advantage of carbon resource after synthetically compared different managements, microbial diversity as well. They had variant responses to different carbon sources, the result of PCA suggested that the carbohydrates, polymers and amino acids were main carbon sources microbes took advantage, which under treatment of chemical and organic fertilization mixed along with straw-returned, the type of carbon source microbial utilized under chemical fertilization was similar to which under mixed fertilization with straw-returning(5) DGGE showed bacteria diversity in 0-20 cm significantly higher than which in 20-40 cm,straw-returning or fertilization was benefit for promoting bacteria community diversity, but the best practice for bacterial diversity was by both.Fertilization can promote enzyme activities, increase MBC, decrease soil pH on the contrary. However, the effect of actualizing chemical fertilizer all alone was limited, hybrid fertilizer ameliorated the situation of soil environment getting badly resulted from solely putting chemical fertilizer into effect. Stubble-incorporation significantly augmented soil MBC, advanced enzyme activities, though the disadvantage was enhance soil pH.Stubble-incorporation meanwhile applying hybrid fertilizer was the amendment to weaken the intensive effect to pH by cotton stalk. Stubble-incorporation is propitious to environment and cumulation of soil organic matter on the whole, excite germ’s merisis and increase MBC; in the other hand, chemical fertilizer blended manure bring in both nutrients crops need and exogenetic microbial species, which increased soil microbial diversity and made soil circumstance more stable, go a step further, formed a benign ecosystem of“soil-microbial-crop”. Therefore taking measurements of NPK fertilizer mix manure along with straw is in favor of soil sustainable utilization.