Study On The Screening & Application Of Microbial Agents

In this paper, we studied the culture media and fermentation conditions of the four strains-Bacillus subtilis S3, Bacillus subtilis BS, Bacillus megaterium, Bacillus mucilaginosus, the preparation of the microbial agents and the practical effects in rice were studied. The results are as follows:1、One bacteria strain S3 with a certain ability to produce cellulase was isolated from the soil.By morphological characteristics of the strain, a conventional combination of physiological and biochemical characteristics and 16S rDNA gene sequence analysis, this strain was confirmed to be Bacillus subtilis.2、By using single factor test, the influence of the culture media and fermentation conditions on the number of spores in the broth was studied, and the fermentation conditions were optimized using orthogonal experiment. The result shows that, （1） The suitable media and conditions for B. subtitles S3 were wheat bran 2%, ammonium sulfate 0.10%,yeast extract powder 0.78%, KH₂PO₄ 0.30%, MgSO₄·7H₂O 0.20%, inoculation amount 2.0%, initial pH 8, fermentation time 36h.Under these conditions, the viable count reached 2.88x10⁹CFU/mL; （2） For B. Subtitles BS those were wheat bran 3%, ammonium sulfate 0.15%, yeast extract powder 0.55%,KH₂PO₄ 0.30%, MgSO₄·7H₂O 0.30%, initial pH 7.5, inoculation amount 2.0%, fermentation time 60h. Under these condition, the number of spores was up to 2.96×10⁹CFU/mL; （3） For B. Mucilaginosus those were wheat bran 3%, ammonium sulfate 0.10%,yeast extract powder 0.78%, KH₂PO₄ 0.30%, MgSO₄·7H₂O 0.20%, initial pH8.0, inoculation amount 3.5%, fermentation time 72h. Under these conditions, the average number of spores was up to 2.39×10⁹ CFU/mL; （4）For B. Megaterium those were corn meal 3%, Ammonium sulfate 10g, yeast extract powder 0.78g, KH₂PO₄ 0.30%, MgSO₄·7H₂O 0.30%; initial pH 8.0,0.5% inoculation, fermentation time 60h. Under these condition, the average number of spores was up to 2.50×10⁹ CFU/mL.3、The ratio of the bacteria in the starter culture, as derived from pot experim ent, was B. subtilis S3:B. Subtilis BS:B. megaterium:B. mucilaginosus=0.5:1:1.5:1. Compared to the controls, the fresh weight of Brassica rapa L.Chinensis had an average increase of 0.65g per head, an increase of 38.92%; dry weight increased by an average 0.55g per head, an increase of 61.80%.4、With respect to conventional compound fertilizer and biochar compound fertilizer, the adding of both biochar fertilizer with microbial agents had increased 19.52%、14.53%、 14.78% and 6.12%、1.70%.3.25%（P<0.05） of the chlorophyll level,46.38%、39.24%、 42.57% and 22.37%、14.09%、19.19%（P<0.05） of SOD activity, and 42.07%、32.55%、 35.60% and 21.65%、11.89%、15.25%（P<0.05） of CAT activity during booting period,18.41%、12.01%、12.95% and 8.27%、2.53%、3.28%（P<0.05）,30.26%、14.29%、 25.52% and 13.74%、0.21%（decreased）、9.60%（P<0.05）,37.15%、22.07%、24.73% and 23.17%、8.79%、12.02%（P<0.05） respectively during grain filling period.The pH value、organic content and available potassium of the soil had increased,this could lower the Amount of some of the nutrient in the soil such as alkaline nitrogen, available phosphorus, total phosphorus and total nitrogen. While the effects on the cat ion exchange capacity、slowrelease potassium and total potassium were not obvious.In the aspect of processing impose the agents cadmium content in soil and grain,comparing to the use of compound fertilizer,as a result of the bacterial inoculation the average reduction of Cadmium in soil and grain sample were 27.25%、22.96%、26.61%（P<0.05） and 23.89%、 21.90%、26.77%（P<0.05）,also decreasd 13.00%、19.67%、14.00%（P<0.05） in soil and increased 6.52%、4.08%、10.05%（P<0.05） in grain sample compared to the use of biochar compound fertilizer;the average yield had increased 14.34%、18.64%、 23.59%（P<0.05） and 19.67%、24.18%、29.36%（P<0.05）.The amount of fertilizer showed that microbial agents, to a certain extent can improve soil enzyme activity, increase soil nutrient content and reduce the cadmium content insoil and grain to acertain extent, improve the yield of rice.