| In facility culturing agriculture, chemical-intensive farming is the conventional method to promote the productivity in a short period and leads to the accumulation of salinity in soils, among which the secondary salinization of soil is the predominant problem. It could limit the growth of crops, constrain agricultural productivity, lead to the abandonment of agricultural soils and could be hazardous to environment in particular to the human health through food chain eventually. In order to explore an effective way to repair the secondary salinization soil in facility cultivation, this paper employs the traditional plate counts of cultivation method, the molecular method, and the BIOLOG method to study the effects of NCT-2 bacterial manure on the microbial ecology in secondary salinization soil. The main results are showed as follows:1. The 16S rDNA of Nitrate nitrogen transformation bacterium NCT-2 was amplified by using PCR method, and then a length of about 1500bp base sequence was get. Through the sequence and system evolvement analysis, the bacterium was identified as Bacillus megaterium sp., which is coincide with its biological characteristics and physiological characteristics2. The growth rate of nitrate-transforming bacterium NCT-2 is based on the kind of medium, the pH value, and the incubation temperature and incubation time. The results showed that when the pH value is 7.0 and the temperature is 35℃, NCT-2 get the optimal growing condition and the highest transformation rate (78%) in potato culture medium (PDA). The bacterium NCT-2 has no significant inhibiting effect on common pathogenic bacteria of soil-borne disease.3. Soil microbial community structure diversity was assessed with the traditional plate counts of cultivation method and the BIOLOG method. The traditional plate counts of cultivation method results showed that secondary salinization inhibited soil microorganism growth, that is the number of soil microorganisms declined along with the nitrate nitrogen concentration increasing. Also, the EC and the nitrate nitrogen concentration were negatively correlated with soil bacterium. The BIOLOG method showed that secondary salinization had prominently adverse effects on the soil microbial community functional diversity; nitrate accumulation inhibited the sole-carbon-source metabolic ability of soilmicrobial communities. The four carbon sources (Carbohydrates, Miscellaneous, Amino acids and Polymers) could reflect most of the information about carbon sources utilization. Microorganisms preferred these four carbon substrates were more vulnerable to nitrate. These four carbon substrates could be one of the prioritized microbe carbon sources in the microbial bioremediation of secondary salinization soil.4. The effects of the soil conditioner NCT-2 bacterial manure on secondary salinization soil were investigated by pot culture experiment. After the application of NCT-2 bacterial manure, the soil microorganisms quantity and the the total organic carbon content increased, the nitrate nitrogen concentration and the EC value declined. The BIOLOG results showed that sole-carbon-source-utilization and the diversity indices in JJG treatment were significantly higher than the other treatments. Application of NCT-2 manure improved the soil microbial metabolic diversity. Among all the treatments, the mixture of bacterium NCT-2 and carbon source 1 had the best remidation effect.5. Use the Degenerative Gradient Gel Electrophoresis (DGGE) to study the genetic diversity of soil microorganisms in secondary salinization. The results showed that the richness and diversity of soil microorganisms had obviously changed after the application of NCT-2 manure. Soil microbial communities were influenced by nitrate nitrogen concentration and differement soil treatment. Among all the treatments, the treatment JJG could significantly improve microbial community structure, the electrophoresis strip quantity of AJJG, BJJG, CJJG were 36, 30 and 32 respectively.6. The effects of application different fertilizer on nitrate content, soil microbial community structure diversity, the greengrocery emergence rate and the production were investigated in the field experiment. The results showed that the quantity of soil microorganisms significantly increased, and the field germination and the agricultural yield were 66% and 58% higher than the control inceptively, while the application amount of compound fertilizer was reduced to 60% through the use of NCT-2 bacterial manure. |
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