Screening Of Bacteria Decomposing Low-temperature Cellulose And The Application Of Composite Microbial Inoculants In Straw Returning To Field

China is one of the traditional agricultural countries around the world with a mass of crop straw resources. But the straws have not been utilized well and a large number of crop straws have been abandoned, even caused serious air pollution every year. Rice-wheat rotation system is one of the main cropping systems in China, which mainly distributes in the Chinese Yangtze River. After rice harvest, because of low temperature in autumn and winter, and the interval time of rotation is short, so straw returning into field needs to be degraded quickly. Otherwise, it will be hard for wheat seedlings to root, and led to smaller harvests. The research on the straw returning with high efficiency will not only solve these environmental problems, but also enhance the soil fertility, optimize the soil structure and increase the crop yield.There were two efficient degrading cellulose cold-adapted bacteria (LI and L2) have been isolated from sodium carboxymethyl cellulose Congo red medium via this research. These two strains have been preliminary identified as Streptomyces genus according to the physiological-biochemistry experiments and 16S rDNA sequencing. Coupled with the other two actinomycetes decomposing high-temperature cellulose saved in our laboratory. There were three microbial agents named as high-temperature microbial agents (F), low-temperature microbial agents (L) and composite microbial agents (FL) obtained from the orthogonal experiment of screened strains. The results of the filter paper degradation experiment showed that composite microbial agents (FL) has significant effect on filter paper strip degradation and the degradation rate were significant faster than high-temperature microbial agents and low-temperature microbial agents (L)(P<0.05). The cellulase enzyme experiments results showed the cellulase activity of FL reached a maximum value of 112.19(U/ml that significant higher than the maximum activity of F and L(P<0.05), which were 99.24 U/ml and 74.56 U/ml at 37? after incubation 3 days at the same temperature of 37? respectively. While after incubation 3 days at 14?, the maximum cellulase activity of FL was 75.94 U/ml that significant higher than the maximum cellulase activities of F and L, of which the value were 63.50 U/ml and 56.59 U/ml respectively(P<0.05). From the results mentioned above, we can infer the ability of cellulose degradation of FL is higher than F and L under the low temperature and ambient temperature. In the solid state fermentation experiments, after 10 days fermentation with incubation of these three microbial agents respectively at 14?, more than 20% rice straw have been degraded and the degree of rice straw degradation of FL reached the value of 34.17%, the composite microbial agents have been proved of the ability of rice straw degradation.Compared with blank control without inoculums, three kinds of microbial agents can decompose rice straw quickly in pot experiment and the microbial agents FL start decomposing process at first, but the results of the experiment process at the end were not significant among them and the rice straw were decomposed completely at the 25th day of all of the three microbial agents.Two treatments and one control were set in the field straw returning experiments, which were control (with no inoculation), F treatment group (inoculation of high-temperature agent F) and FL treatment group (inoculation of composite agent FL). Straw color, straw cutting stress and seed germination index (GI) were follow-determined during the composting process. The natural straw degradation rate was very slow in control with no inoculation and start decomposing at 20th day at the average outdoor temperature of 14?, and the effects of high-temperature degradation microbial agents (F) was inhibited at this temperature and start decomposing at 10th day while the composite agent (FL) has a significant degradation effect on straw at the 10th day. Therefore, add psychrophiles in high-temperature agent can improve the rate of straw degradation under low ambient temperature in the autumn and winter and psychrophiles bacteria promotes the thermophile bacteria start degrading rice straw under that low-temperature condition. According to the results of germination of wheat seeds in soil leachate treatment, in the process of degradation of straw by the composite microbial agents (FL), there would not be any harmful substance on wheat seeds, But instead of being beneficial substances on germinating wheat seeds. The results of this research provide the basis of developing high efficient rice straw degradation microbial agents applied in the autumn and winter, which has a broad application prospects.