Effects Of Nitrogen Management On Rhizosphere Soil Microorganism And Enzyme Activities In Winter Wheat

The study was conducted in the Experimental Station and State Key Laboratory of Crop Biology of Shandong Agricultural University from 2013 to 2014. Jimai 22 were used as the experimental materials. The farming denisities of Jimai 22 were 180 seeds hm-2. Split plot design was applied to examine the effects of nitrogen fertilizer management on rhizosphere soil microorganism and enzyme activities in winter wheat. The purpose of this study is to provide theoretical basis for the reasonable fertilization, the improvement of soil environment and high yield and efficiency. This research adopted the combination of field experiment and indoor analysis. During revival stage, jointing stage, anthesis stage and maturity stage of the winter wheat, the rhizosphere soil microorganisms, enzymatic activity, NO3--N concentrations in soil, nitrogen distribution proportion in maturity as well as the wheat production of different nitrogen fertilizer treatments were determined. The main results are as follows:1 The relationship between application of nitrogen fertilizer and soil microorganism of wheat rhizosphereThe amounts of wheat rhizosphere microorganism were significantly affected by nitrogen fertilizer. With the increase of nitrogen application, soil ammonifying bacteria,nitrifying bacteria, denitrifying bacteria and nitrous acid bacteria raised. Except N0, where nitrogen fertilizer was not applied, there was no significant difference between other treatments because of the same rate of basal fertilizer at jointing stage. At the anthesis period,microbial activity of N4 treatment was the highest, positively correlated with the amount of fertilizer, and each treatment had significant difference at anthesis stage. With the development of growth period, microbial activity decreased gradually in the anthesis stage,there was a direct relationship with large nitrogen fertilizer consumption.2 The relationship between application of nitrogen fertilizer and soil enzyme activities of wheat rhizophereThe amount of nitrogen had an effect on soil urease and protease activity of wheat rhizophere, which increased firstly and then decreased. Except N0, where nitrogen fertilizer was not applied, there was no significant difference between other treatments because of the same rate of basal fertilizer at jointing stage. At the anthesis period, the activities of ureaseand protease of N4 reached the peak. After jointing stage, nitrogen fertilizer could significantly increase the soil enzyme activities. This showed that application of nitrogen fertilizer had a positive effect on soil urease and poteinase activities. The anthesis period is the key stage for nitrogen supply, the supply of nitrogen fertilizer must be guaranteed if sufficient water supply is available.3 The relationship between application of nitrogen fertilizer and soil NO3--N content in wheatThere was no significant difference between each treatment in soil NO3--N at jointing stage in the winter. With the increment of nitrogen rate, significant difference was found between surface soil layers from 0 cm to 40 cm at anthesis period, and surface content of nitrate nitrogen is higher than winter and jointing stage, it showed that nitrogen and soil NO3--N content are positively correlated. As the soil layer deepen, nitrate content decreases gradually and no significant difference was found. Nitrate nitrogen content of N4 of maturity reached the highest 45.029 mg kg-1in the whole growth period, it showed that nitrogen absorption of wheat at the maturity stage decreased significantly, which was affected by watering. Nitrogen leaching was less in surface drought soil, compared with soil NO3--N content on the high side.4 The relationship between application of nitrogen fertilizer and the wheat grain filling rate and processThe grain filling rate showed a trend of rapidly raise after anthesis in 4-20 days, it reached maximum about 20 days later after anthesis and the filling rate of N3 is the fastest,which reached above 1.8 mg grain-1d-1, and then gradually reduced after anthesis. There was no significant difference between the filling rates of the groups in 4-24 days after anthesis.Significant difference was found between the groups with the increase of nitrogen application from 28 to 36 days after anthesis, which showed N3 > N4 > N2 > N1 > N0. Application of nitrogen was benefit to increasing wheat filling process.5 The relationship between application of nitrogen fertilizer and dry matter accumulation of wheatWith the increase of nitrogen fertilizer application, dry matter accumulation showed a trend of rising firstly and then decreased, both varieties showed the highest dry matter accumulation of N3. Nitrogen application of N3 was 240 kg hm-2; Nitrogen application of N4 was 300 kg hm-2to the extent, dry matter was slightly lower compared whit the treatment of N3. The results showed dry matter accumulation quantity will gradually reduce if plant population is oversize after nitrogen fertilizer exceeds a certain amount.6 The relationship between application of nitrogen fertilizer and wheat yield componentsThe wheat yield components are mainly consisted of ear numbers, grain numbers per ear and grain weight. To a certain extent, fertilization can significantly increase the yield of wheat.With the increase of fertilizer, ear numbers of wheat, grain numbers of per ear and thousand kernel weight increased from N0 to N4 in the trend of rising, nitrogen use efficiency and production efficiency of nitrogen fertilizer were obviously rising trend. Except the use efficiency of nitrogen and production efficiency of nitrogen have significant difference between the treatment of N3 and N4, there was no significant difference in the other treatments.