Research On Scerrning And Identification Of Nitric Nitrogen Transformation Bacterium And Ameliorative Effects

The facility cultivation agriculture has obtained the remarkable profit in both economic and social aspect in vegetables and other important industrial crop cultivation in our country, but a large number of nitrogenous fertilizer used massively causes soil secondary salinification seriously. The residual nitric nitrogen in the soil and the water body has seriously threatened to human health and natural environment. There are many traditional solutions to soil secondary salinification has many, while they are easy to cause the secondary pollution and reduce the productivity effect. So it cannot solve the problem fundamentally. In this paper, in order to verify the efficient way to repair the facility cultivation soil secondary salinification by soil microorganism, the microorganism of secondary salinization were screened and studied by using facility cultivation soil in Shanghai Congming and Nanhui modern agricultural region. Moreover, the bioremediation of the pollution of nitrate was also investigated. It provided the theory basis and practice instruction for the further research. The main results are showed as follows:1. Four nitrate-transforming bacteriums, named NCT-1, NCT-2,NCT-3,NCT-4, were screened by enrichment culture and gradient domestication repeatedly from serious secondary salinization soil collected from greenhouse in Congming island and Nanhui, Shanghai. They can grow depending on nitrate nitrogen as the sole nitrogen sources.2. The isolated NCT-1 was identified as klebsiella sp., NCT-2 was identified as Bacillus megaterum, NCT-3 was identified as Stenotrophomonas maltophilia sp., and NCT-4 was identified as Stomatococcus sp., according to its biological characteristics, physiological characteristics and 16s rDNA amplification and sequencing analysis.3. The growth rate of four nitrate-transforming bacteriums had relation to medium, incubation pH, incubation temperature and incubation time. The result showed that the best incubation condition for NCT-1and NCT-4 was potato culture medium (PDA), pH7~8, 30℃and 18~24h, and the best incubation condition for NCT-2 was potato culture medium (PDA), pH7~8, 35℃and 18~24h; in addition, the best incubation condition for NCT-3 was beef extract peptone medium, pH7~8, 30℃and 18~24h.4. It was necessary for nitrate-transforming bacteriums to grow up with carbon source. In order to make microorganism bacterial fertilizer in the industrial production in the later, so it is necessary to seek for more economic and efficient organic carbon source. In this chapter, the transformation efficiency of strain NCT-2 and NCT-2 to nitrate nitrogen was studied in different carbon sources. With glucose as control(CK), the other four different carbon sources, i.e. brown sugar (HT), wheat flour (MF), peat (CT) and wheat straw (MG), were inoculated strain NCT-2 under high-concentration of nitric nitrogen. Effect of strain NCT-2 on OD600, as well as pH value, EC value, nitrate nitrogen, nitrite nitrogen, ammonium nitrogen and total nitrogen was studied. The results showed that for strain NCT-1, it had little effect on pH/EC value in different carbon sources, while it could make better use of wheat flour to grow than brown sugar (HT), peat (CT) and wheat straw (MG). In addition, it could reduce nitrite nitrogen and total nitrogen content markedly and did not accumulate nitrite nitrogen and enhance ammonium nitrogen obviously. Moreover, the viable bacterial number of strain NCT-1 in wheat flour on the 11th sampling day was more than any other carbon sources. For Strain NCT-2, the OD600 value was higher in brown sugar, wheat flour and control medium, and pH value showed an increasing trend as a whole. It had little effect on EC value in different carbon sources. Nitrate nitrogen content was decreased significantly and ammonium nitrogen content was increased markedly when strain NCT-2 utilizated brown sugar and wheat flour as carbon sources. However, it could not utilizate peat and wheat straw to reduce nitrate nitrogen content. Except brown sugar and control group, nitrite nitrogen content had no obvious accumulation phenomenon in other treated groups, and total nitrogen content kept unchanged. The viable bacterial number of strain NCT-2 on the 11th sampling day was all high in different carbon sources. It showed as follows among treated groups: HT>CK>MG>MF>CT. From the overall, wheat flour was regarded as the most ideal carbon source for strain NCT-1 and NCT-2 transforming nitrate nitrogen.5. The straw can improve soil condition effectively and increase its loose. In order to verify the improvement effect of NCT-2 to the secondary salinification soil in the stuation of straw as carbon source. An indoor artificial adding experiment was conducted to investigate ameliorative effect of nitric nitrogen transformation bacterium NCT-2 (Bacillus megaterum) to soil secondary salinification. Three different nitric nitrogen levels were designed in the indoor artificial adding experiment, i.e. 0,100,200 mg kg -1, and three treatment methods, i.e., control(CK), straw powder (MF) and straw powder & NCT-2 (MF+JY). Effect of NCT-2 on soil pH value, EC value, concent changes of nitric nitrogen, nitrite nitrogen, ammonium nitrogen, total nitrogen, total phosphorus, organic matter were studied. Results showed that compared with CK and MF treatment, NCT-2 baterium in MF+JY treatment significantly reduced soil EC value and nitric nitrogen content, which had little effect on soil pH, with straw powder as carbon souce. When nitric nitrogen concentration level was 200mgkg-1, nitric nitrogen concent in MF+JY treatment decreased to 45.5%, equating 1.51 times of that in MF treatment, and its effect surpassed that in MF trearment. The changes of nitrite nitrogen and ammonium nitrogen concent in MF+JY treatment showed the same trend as them in CK treatment. And there was no obvious difference between the 2 treatments. Both soil total nitrogen content and soil total phosphorus content were basically uninfluenced, but organic matter content increased, which enhanced soil fertility, on the 15th day in MF+JY treatment , compared with them on the 0th day in experimental soil. Nitric nitrogen transformation bacterium NCT-2 played important roles in soil secondary salinification with straw powder as carbon source. It had certain application prospect on reducing nitric nitrogen content in the secondary salinification soil.