| “wheat-maize†rotation is one of the main forms of food production in northern China, where the technology of straw-returning plays an important role in improving soil. But, the soil structure, the quality of sowing and wheat seedling growth are seriously affected by the poor efficacy on crushing and burying straw and the slow decomposition rate. At the same time, the occurrences of drought and freeze damage are caused easily. In addition, the suitable environmental conditions provided for the soil borne pathogens infecting wheat and maize because of straw-returning and the frequent mechanized cross-operating has made the pathogens accumulate in the topsoil. In the end, the soil borne disease of wheat occurred seriously year by year.In order to solve the contradiction between the effective utilization of straw resources and the occurrence of soil borne diseases with farming problem, a strain, Bacillus subtilis B1514, was isolated in the Plant Disease Ecology Lab, College of Plant Protection, Agricultural University of Hebei, from the wheat-maize rotation soil, which can decompose straw and has a function on control soil borne disease of wheat. On the basis of the previous work in laboratory, the fermentation carriers, wetting agents and dispersing agents were screened in this study and the optimal formulation of wettable powder of Bacillus subtilis B1514. Then, the indoor experiments and plot experiments were conducted to determine the effects of dressing seed with the wettable powder on wheat seeding growth, occurrence of wheat sheath blight and yield.The results showed that the preparation method of wettable power of Bacillus subtilis B1514 mainly included three steps. Firstly, 18% diatomite was put in shake flask containing 70% fermentation broth. Secondly, it was mixed with 4.8% CMC-Na and 7.2% PEG8000 after being shacked and dried,. At last, the mixture was crushed and mixed sufficiently by the jet mill. Quality detection showed the spore content of B. subtilis B1514 wettable powder reached 1.70×109 cfu/g(p H6.8), with a suspension rate of 72%, a dispersing time of 135 s, a fineness through rate of 95% and a moisture content of 3.8%. The method had a simple and fast characteristic with a low cost.The results of pot experiment showed that germination potential, germination indexand germination rate of wheat seeds were significantly improved after being dressed by 500 g, 600 g and 700 g B. subtilis B1514 wettable powder per 100 kg wheat seed. The root length, rooting ability, plant dry weight and ratio of root to shoot of seeds dressed by 500 g B. subtilis B1514 wettable powder per 100 kg wheat seeds were all significantly higher than those of the seeds dressed with 30g/L difenoconazole FS and 2% tebuconazole dry powder, with the increase rates from 25.42% to 31.24% and from 24.88% to 31.25%, respectively. Its control effect on wheat sheath blight reached more than 71.61% at seedling stage. Preliminary determination of the best concentration of the B. subtilis B1514 wettable powder was 500g/100 kg wheat seed.Field experiments in four different experimental stations showed that the average yield in the treatment at the best concentration of wettable powder was increased by 12.5 % or more, with a higher seedling emergence, a uniform growth, more tillers and roots. There was a good control effects on the Wheat sheath blight, Take-all and Common rot, with 70%~85%, 50%~75%, 62%~85% at the jointing stage and 55%~71%, 52%~60%, 46%~73% at the filling stage, respectively. The decomposition rate of maize straw was increased significantly and was up to 58.18%~69.07% at the filling stage, which was increased by 31%~38% compared with that of the control. |
