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As the tea plants were physiological characteristic of NH4+-N adsorption and tolerance, the ammonium nitrogen fertilizer was usually chosen as nutrition nitrogen for tea growing. But nitrification in the soil of tea garden caused ammonium convert to the nitrate forms, and thus reduced effectiveness of nitrogen, acidulated the tea garden soil and polluted the ground water. Nitrobacteria was separated and purified from the same soil which collected in Taishan tea garden of Tai’an, Shandong Province. And then the superior strains were screened, their characteristics were investigated and the species were identified. At the same time, the effects of different treatments on nitrification inhibition were compared. Main results as follows:1. By the experimental procedure of enrichment culture and microbial purification, three nitrosobacteria (A1～A3) and three nitrobacteria (N1～N3) were screened from the soil of tea garden in Shandong province. According to the removal rate of ammonia nitrogen and nitrite nitrogen, the nitrifying activity of strains arranged as fallows: A3>A1>A2, N3>N1>N2. On the basis of the characteristics of strain’s physiological&biochemistry as well as referring to <Bergey’s Manual of Systematic Bacteriology> and <Common Bacteria System Identification Manual>, the strain A3 was preliminary identified as Nitrosomonas and N2 as Nitrospina. In addition, the effect of temperature and pH on the nitrifying activity of A3 and N2 were measured. The result showed that the optimum temperature of two strains were 30℃; but their optimal pH were different, A3 for 8.0, N2 for 7.5.2. By applying single urea as contrast, the effect of different methods of applying urea with such as: DCD ( Dicyanodiamide,short for UD), microbial agent (UJ), mixed fertilizer(UY), microbial agent plus with mixed fertilizer(UYJ) ,or covering the tea dust on soil surface (UF), on urea transformation and nitrification were studied by the experiment of aerobic incubation. By determining the content of ammonium nitrogen, nitrate nitrogen, soil urease activity and the amount of ammonia-oxidizing bacteria (short for AOB) in the soil , calculating the rate of apparent nitrification , the results showed that the contents of ammonium nitrogen in the all treatment soils were improved by the contrast, but the content of nitrate nitrogen were reduced, the peak period of urease activity were delayed, the rate of apparent nitrification were decreased, and the amount of AOB were inhibited. Among the five treatments, UF is the best. It had the highest content of ammonium nitrogen, the lowest content of nitrate nitrogen and the rate of apparent nitrification in the soil. The second is UD treatment because the DCD could delay the peak period of urease activity, reduce urease activity in the early days and it also could inhibit the amount of AOB significantly. In addition, by compared the effect of UYJ to that of UJ, it could be suggested that the effect of microbial agent on inhibiting nitrification would not be significant in tea garden with rich organic matter.
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