The Study On The Microbial Community Succession Of Straw Decomposition

Long-term water scarcity,the abuse of chemical fertilizers and insufficient investment of organic fertilizers have caused insufficient soil fertility of northwestern arid area.Therefore,in the face of declining status of agricultural production land,vigorously developing soybean straw and returning corn stalks will play a pivotal role in soil fertility and sustainable development of agriculture.As a common crop in the northwest,corn can increase soil fertility after returning to the field.The soil respiration was determined by gas chromatography.The enzyme activity of soil was determined by the technique of microplate reader.The effects of various environmental factors on the decomposition process of straw and the succession of microbial community were studied.The main objectives are as follows:(1)Study on the decomposition process of corn/soybean straw mixed into the field;(2)To analyze the effects of different soil structure,water,temperature and other environmental factors on straw decomposing;(3)To discuss possible driving mechanism for straw degradation from the perspective of soil microbial community.The results are as follows:1.The degradation rate of straw was various due to the types of straw.The degradation rate of three different types of straw,soybean straw,corn straw and soybean straw + corn straw,were compared in this experiment.The results showed that the degradation rate of soybean straw was the fastest,followed with corn straw and soybean straw + corn straw.Soil microbes played a significant role,and abundance of Proteobacteria and Bacteroidetes significantly increased during the process of degradation of straw.The soybean straw has the greatest impact on soil microbial community structure.2.Soybean straw degradation was affected by soil aggregates of different particle size.The small aggregates were small in volume,but large in specific surface.So,their contact surface with organic matter in the soil was large.Therefore,the small aggregates were beneficial for soil carbon retention.The large aggregates were larger in volume and had the fastest metabolism to straw.It suggested that the large aggregates could accelerate the degradation of straw.3.The synergistic effect of moisture and temperature had a significant effect on straw degradation.Too high or too low moisture and temperature could decrease degradation rate of straw.Only at the optimum moisture and temperature(moisture was 30% of the maximum water holding capacity and the temperature was 28℃),the degradation rate of straw was the faster.The dominate taxa of microorganism in the process of straw degradation were various in different condition of temperature and moisture.When the moisture was 15% or 30% of the maximum water holding capacity,the dominant microflora were Proteobacteria,Acidobacteria and Actinobacteria.When the moisture was 50% of the maximum water holding capacity,the dominant microflora were Proteobacteria,Acidobacteria and Bacteroidetes.When the temperature was 16℃ or 28℃,the relative abundance of Firmicutes was significantly increased compared with 4℃.The above research results showed that straw degradation was affected by many factors,such as types of straw,soil aggregates,water and temperature.These factors might have a significant impact on straw degradation through regulation of soil microbial community structure.The results of this study provided a theoretical basis for optimizing soil microbial community through artificial farmland management and promoting straw decomposing in agricultural production.