| Although chemical fertilizer can promote the growth of crops and increase crop yield rapidly in a short time, nowadays, abusing of chemical fertilizer has caused some serious problems, including environmental pollution, soil hardness and desertification and soil erosion. Thus, developing a new type of fertilizer, which is environmentally friendly and suitable for a new era, has become a hot spot of current research, and also meets the requirements of changing the extensive agriculture to sustainable agriculture.In this experiment, we used dilution coating methods and specific selective medium to screen for functional microorganisms, including 14 strains of nitrogen-fixing bacteria,13 strains of soluble phosphorus bacteria, and 15 strains of decomposing potassium bacteria. For all these strains, we carried on Gram staining methods and spore identification. And then, we found 1) N11 nitrogen-fixing strain, K12 and K13 decomposing potassium strains are Gram-negative bacterium, all the others are gram-positive; 2) N3 nitrogen-fixing strain, P, WP1, WP6 soluble phosphorus strains, and K, K0, K6 decomposing potassium strains can produce spores. To further investigate the growth-promoting effects of all these strains to plants, we took corn seeds sprouting experiments and corresponding single factor pot experiments. In the corn seeds sprouting experiments, some strains had significant inhibition to corn seeds sprouting, including WP2, WP5, YP3, YP6; while nitrogen-fixing strains and decomposing potassium strains did not show similar phenomena, only soluble phosphorus strain K2’s germination potential and germination rate was slightly lower than those in control water. Moreover, in single factor pot experiments, nitrogen-fixing strain N10, soluble phosphorus strains YP1, YP4, and decomposing potassium strains K10, K11 had relatively better performance; however, all these strains did not have significant differences. In the identification test of dissolved phosphorus ability, the D/d ratios of YP3 and YP6 could reach 4 over. By the preliminary screening test and some basic evaluation tests, we had established functional fertilization bacteria strain library.After comprehensive consideration of Gram positive bacteria screening test, spore producing bacteria screening test, corn seeds sprouting experiment and single factor spot experiment, we picked out nitrogen-fixing bacteria N5, N10, N12, soluble phosphorus bacteria WP1, WP5, P, and decomposing potassium bacteria K, K0, K6. In the same time, we took out flask shaking experiments to all these bacteria. There were no significant changes in pH of nitrogen-fixing and decomposing potassium bacteria, while there was obvious decline of soluble phosphorus bacteria. During the flask shaking experiments, the content of rapidly available phosphorus and rapidly available potassium had improved significantly:on the sixth, day, soluble phosphorus bacteria P reached the maximum amount of dissolved phosphorus to 267.915μg/mL; while soluble potassium content of decomposing potassium bacteria K6 reached 19.277μg/mL on the seventh day. By using simulation orthogonal experiment method, we designed nine combinations, and did granulation experiments to these nine combinations. We detected microbial quantity dynamic changes, and finally determined combination N5,P, K. By using this combination to do pot inoculation experiments, we found that M+S grew well in sterilized soil. And its plant height, leaf length and width were consistent with combination F, as well as the part on the ground, while its root-shoot ratio was slightly lower than combination F. However, all these data did not achieve the expected results.To sum up, resolving the oneness of microbial fertilizer and non-standardization during the actual manufacture are the key points of this study. In addition, we studied organic compounds process of microbial fertilizer, and focused on the methods of microbial compound agents needed in the granulation. |
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