| Potassium is a necessary nutrient for plant growth, and it has an important influence on plant growth and stress resistance. Red earth is primary soil resources in South China, which shows acid property with the pH value between5.0～6.5, and speedes up itself decomposition, mineraliazation and hydrolysis intensity during the hot and rainy season. Thus, the elements in the soil changed sharply and potassium lost most serious next only to calcium. As a result, red earth in South became the one which lacks potassium most seriously. For a long time, the irrational fertilization measures of more nitrogen, less phosphorus and potassium made potassium deficient, which has become the main factor to improve crops’yield and quality in South China. In China, the domestic production of potash is far from satisfied with the needs of agriculture, therefore, there is a great significance to the security of China’s agricultural production to seek a high efficient usage and alternative technologies of potash. Numerous studies showed that a lot of potassium-solubilizing bacteria presented in soil, which could change insoluble potassium into an easily utilized one. The bacteria could also secreted a variety of plant hormones to promote the plant growth and improve soil microenvironment. Therefore, the Potassium-solubilizing bacteria which screened from soil developed into microbial fertilizer has important practical meaning for solving the situation of potassium-deficient in Southern red earth and promoting agricultural production. In this research, a potassium-solubilizing bacteria named G4was isolated from red earth in Jiangxi province, identified and further studied on its fermentation and growth promotion to plant. Twelve strains of potassium-solubilizing bacteria were isolated on silicate medium using dilution-plate method and one of them named G4, whose potassium-releasing efficience was27.62%, was screened according to shake flask releasing potassium test. The colony of G4had round, neat edges, and displayed the property of transparent and protuberant, moist, sticky and difficult to stir up. Its cell was oval-shaped, Gram-positive, could produce spore and capsule. It was identified as Paenibacillus sp.strain G4according to the result of biochemical characteristics and16S rDNA sequence analysis.The fermentation conditions of Paenibacillus sp.strain G4were optimized by single factor and orthogonal experiment, and the optimal conditions were as follows:1%maltose,0.2%peptone,0.05%dipotassium phosphate,25℃,80ml/250ml(80ml in250ml flask),48h, Initial pH7.5,7%of Inoculation quantity.Paenibacillus sp.strain G4was inoculated into Brassica campestris ssp.chinensis in pot experiment. The results showed that the plants in both group A5(inoculated G4with5ml) and A50(inoculated G4with50ml) increased their height, fresh weight, Chlorophyll content, Vitamin C content, decrease Nitrate content. The height, fresh weight, Chlorophyll content, Vitamin C content of the plant in the group A50were increased by17.0%,36.4%,10.7%and33.3%respectively and the Nitrate content was decreased by19.0%compared to the control. Meanwhile, G4could impact soil microenvironment and increased the number of bacteria, actinomycetes, silicate bacteria111.6%,159.3%,128.0%respectively and decreased the number of fungi45.6%. The activity of Catalase, Urease, Sucrase were also significantly improved by5.17%,5.13%,6.59%respectively. Thirdly, the content of available K and slow-release K were increased by10.1%and26.4%. In a word, Paenibacillus sp.strain G4could significantly improved the soil microenvironment and the yield and quality of crops.The results of this study showed that Paenibacillus sp.strain G4has a strong activity of releasing potassium, and can improve soil microenvironment and promote plant growth, it is expected to be developed into microbial fertilizer for agricultural production. |
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