| Corn stover resource is very abundant but is not utilized adequately in China. Straw returning is an effective measure to improve soil nutrients and achieve sustainable development of agricultural production. However, in spring maize region of north China, the cool climate limits straw decomposition. Because returned straw decaying needs a long time, it not only could not serve as fertilizer for current crop, but also affect post-season planting and seedling emergence. In order to promoting efficient decomposing of corn stover in low temperature region, the present study collected corn stover returned soils, cow dungs and rotting leaves from the frigid region (average annual temperature of-7℃～8℃) of northern China and screened the microbial consortium with efficient corn stover degradation ability at low temperature (4℃ ～ 10℃) by carbon source restrictive cultivation and cold acclimation. Then the corn stover decomposing activity, composition structure, stability and applicability were evaluated, so as to provide microbial strain resources and technical supports for accelerating the efficient degradation of corn stover at low temperature(4℃～10℃) in frigid region of northern China. The main results of this study are as follows.1. A microbial consortium with efficient corn stover degradation ability at low temperature was screened out. Microbial consortia was screened by enrichment cultivation, restrictive cultivation and cold acclimation, after that,7 groups of psychrophile (10℃) and mesophilic (15℃) double-efficient consortiums and 20 groups of psychrophile (10℃) efficient consortiums were gained from 128 copies of inoculums sources such as straw returned soils, cow dungs and rotting leaves collected from frigid regions of northern China. Finally, a microbial consortium with steady degradation ability of corn stover and efficient production of cellulase at low temperature (4℃～10℃) was obtained by analyzing the corn stover degradation ratio of different generations and dynamics of cellulase activities, which was named as GF-20. The microbial consortium GF-20 went into logarithmic growth phase within 12h after inoculation, secreted cellulase and degeaded corn stover to esters or hydrocarbons. The consortia GF-20 degraded corn stover by 32.10% after 15 day fermentation at 10℃ and 10.27% higher than the control consortia No.8 (screened by our team, the corn stalk degradation ratio was 22.02% under 15℃ condition).2. Composition of the microbial consortium with efficient corn stover degradation ability at low temperature was identified. Microbial consortium GF-20 was consisted of 22 kinds of bacteria and 4 kinds of fungi.The bacteria mainly included Azonexus hydrophilus, Azospira oryzae, Variovorax boronicumulans, Hydrogenophaga caeni, Herbaspirillum frisingense, Arcobacter cloacae, Pseudomonas fuscovaginae, Cellvibrio mixtus subsp.mixtus, Seleniivibrio woodruffii, Rhodococcus qingshengii, Terribacillus saccarophilus, Planococcus antarcticus, Bacillus licheniformis, Bacillus tequilensis, Clostridium populeti, Clostridium xylanolyticum, Paludibacter propionicigenes, Pedobacter agri, Sphingobacterium cladoniae and Uncultured bacterium. The fungi related to Lotharella globosa, Trichosporon sp., Trichosporon loubieri and Chlamydomonas leiostraca.3. Stability and applicability of the microbial consortium with efficient corn stover degradation ability at low temperature were expounded. The consortium GF-20 remained relatively stable in the corn stover decomposition process. Microbial consortium GF-20 sub-cultured under different temperature (4℃～30℃) and pH(6.0-9.0) conditions or continuous cultivation under changed temperature (0℃～40℃) conditions also kept stable growth property, decomposing function and composition structure. It indicated that GF-20 had excellent resistance and adaptability to volatile environment. Furthermore, consortia GF-20 had more stable composition structure, and that induced GF-20 to secrete cellulase and promote the decomposition of substrate as the corn stover and ammonium are used as the carbon and nitrogen source respectively. The critical dilution gradient of consortia GF-20 was 1014 times.4. Application effects of the microbial consortium with efficient corn stover degradation ability at low temperature were implemented. Microbial inoculants GF-20 which was developed under 10% of inoculation amount, initial pH at 6.5,2.0% of osmotic pressure, corn stover and ammonium sulfate ratio at 40:1, at 10℃ temperature could significantly accelerate straw decomposition. Corn stover degradation rate of inoculants GF-20 was 29.00%,36.75% and 59.47% under 4℃,10℃ and 30℃ conditions after 60 days,7.21%, 9.78% and 10.26% higher than that of inoculant Lu Kang respectively. The soil available N, available P, available K and organic matter contents increased by 0%-5.32%,5.26%-14.17%,2.07%～3.57% and 0.44%～2.94% respectively. Applications of GF-20 could not only significantly improve the soil catalase, urease, alkaline phosphatase, sucrase, β-glucosidase and cellulase activity, but also obviously increased soil microbial richness and diversity index. Using GF-20 inoculum could make the Candidatus saccharibacteria and Planctomycetia groups emerged in soil, promoted the functional microorganisms such as Herbaspirillum lusitanum, Bacillus sp., Cellvibrio fibrivorans, Melanocarpus albomyces breed. Furthermore, applying microbial consortium GF-20 did not influnce maize germination rate.In summary, the microbial consortium GF-20 had stable corn stover decomposing activity and community composition structure, it could significantly promote corn stover decomposition, improve the soil nutrients and soil enzyme activities at low temperature (4℃～10℃), a good application prospect should be anticipated. |
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