Screening Of Wheat Straw Degradation Strains And Application Effects

In this study high effective degradation strains were screened and identified from the virgin foresthumus soils. And a series of experiments were conducted, including the optimum nutrition of bacterialstrains fermentation growth, the degradation effects and influencing factors on straw degradation.Themain objective was obtaining the excellent degradation strains for accelerating straw decay, in order toprovid scientific basis to improve wheat straw degradation in the northern. The research results were asfollows:Five high effective straw-degradation strains were obtained by diluting and spreading plate method,enrichment culture, Congo red stain method and filter paper disintegration method. With theidentification of bacterial morphological characteristic, physiological and biochemical appraisal and16SrDNA sequence analysis, the five strains were well-established. They were Bacillus cereus LYZ22,Bacillus circulans DG15, Bacillus subtilis A4B3, Alcaligaenes faecalis DG75B, Paenibacillusaglinolyticus JC117.The best fermentation conditions for five strains were studied through single factor and orthogonaltest by600nm turbidimetry method. The best fermentation conditions of DG75B strains were sucrose1%, sodium nitrate0.2%, pH value6.5, temperature30℃; the optimal fermentation conditions of LYZ22strains were sucrose2%, sodium nitrate0.25%, pH value7, temperature30℃; the fermentationconditions of DG15were sucrose2%, sodium nitrate0.25%, pH value7, temperature30℃; the optimalfermentation conditions of A4B3strain were sucrose2%, sodium nitrate0.25%, pH value7.5,temperature32℃; the optimal fermentation conditions of JC117were glucose0.5%, sodium nitrate0.3%, pH value6.5, temperature28℃.The best inorganic elements group and dosage of strain DG15were Ca0.001%, Mo0.0001%, B0.0001%. During five days, straw weightlessness rate was37.90%. The optimal inorganic elementsgroup and dosage of strain DG75B were Ca0.005%, Mg0.015%, Mn0.0005%, Fe0.0005%, Mo0.0005%. Its straw weightlessness rate reached40.59%. And the optimal inorganic elements and dosageof strain LYZ22were Ca0.01%, Mg0.03%. The straw weightlessness was41.79%.Effects of straw degradation strains adding inorganic elements were studied. During forty days,variation trend of wheat-straw weightlessness rates and different component contents were from slow tofast in flask, straw weightlessness rate was43.19%, increased by16.07%compared to treatment Tstrainwithout inorganic elements. The contents of straw cellulose, hemicellulose, lignin were decreased by43.18%,54.77%,22.96%, in comparison with Tstrainthe rates were increased by17.29%,15.36%,11.28%respectively.The additive amounts of there strains were determined in pot experiment. The optimal additiveamounts of bacteria liquid from DG75B, LYZ22, DG15were1mL,2.5mL,1mL respectively. On thiscondition, straw degradation with strains was more obvious than the control without strains. Duringsixty days, the straw weightlessness rate of DG75B was53.43%. The contents of straw cellulose, hemicellulose, lignin were decreased by44.55%,53.18%,24.78%. Strain LYZ22was the best ofstraw-cellulose degradation, with the rate of degradation47.84%.The changes of soil labile carbon in pot experiment were determined. Soil labile carbon of strawreturning adding strains were promoted fastly, in comparision with the treatment straw returning withoutstrains. During sixty days, soil labile carbon with strains DG75B, LYZ22, DG15were increased by53.41%,42.93%,33.08%in comparison with the treatment (straw returning) without strains. Comparedwith the control, soil labile carbon with straw returning into field was increased34.92%in sixty days.Wheat seedling biomass and morphological characteristics were researched in pot experiment.Results indicated the treatment with strains straw returning could increase seedling biomass to someextent. Rate of emergence were increased, the growth of plant height and roots were enhanced.