Effect Of Nitrogen Application On Nitrogen Metabolism Of Silage Maize

Different silage maize varieties were studied on regulatory effects of nitrogen application (fertilizing 0kg, 50kg, 100kg, 150kg, 200kg, 250kg, 300kg in each hectare field) on the nitrogen metabolism and key enzyme activity, and effects of nitrogen application on the photosynthetic characteristics, yield and protein content of silage maize were determinated. Regulatory effects of nitrogen application on the protein and yield of silage maize were researched systematically. The aim of this thesis was to provide theoretical foundation and technical support in proper use of nitrogen fertilizer, increasing the yield of silage maize and improving the silage maize qualities. The main conclusions of this experiment were as follows:1. The plant height and stem diameter of silage maize were significantly or very significantly positively correlated with biomass fresh weight, biomass dry weight and grain weight(except seeding stage and elongation stage). Excepted the seeding stage, the green leaf number per plant of silage maize was significantly or very significantly positively correlated with biomass fresh weight, biomass dry weight and grain weight.2. The leaf area indexes (LAI) of these varieties increased with the increasing of nitrogen application. The chlorophyll contents showed peak value at the level of N250 in the whole growth period. The LAI and chlorophyll contents were significantly or very significantly positively correlated with biomass fresh weight (except ripening stage), biomass dry weight and grain weight (except ripening stage).3. The NR, GS, GDH activity and SP contents in functional leaves of silage maize appeared with single peak curve; the peak value occurred in booting stage and tasseling stage. The GS, GDH activity and SP contents in grains of silage maize appeared with single peak curve, but the peak value was varied with different varieties and nitrogen application. The effect of nitrogen application on NR, GS, GDH activity and SP contents in functional leaves and grains of silage maize were different on different varieties and stages. The NR, GS, GDH activity and SP contents (except ripening stage) in functional leaves of silage maize were significantly or very significantly positively correlated among each nitrogen application treatment. The GS, GDH activity(except the 49^th day after spinning) and SP contents in grains of silage maize were significantly or very significantly positively correlated among each nitrogen application treatment.4. Excepted the seeding stage, the NR, GS, GDH activity and SP contents in functional leaves of silage maize were significantly or very significantly positively correlated with biomass fresh weight, biomass dry weight, protein yield and grain yield. The GDH activity and SP contents in grains of silage maize were significantly or very significantly positively correlated with biomass fresh weight, biomass dry weight, protein yield and grain yield.5. The protein contents in leaves of silage maize changed as a single peak curve during the whole growth period. The protein contents in stalks of silage maize decreased with the growth period promoting. The protein contents in grains of silage maize had different trends in accordance to different varieties and nitrogen application. The effect of nitrogen application on crude protein contents in organs of silage maize were varied with different varieties and stages. The protein content in leaves and stalks of these varieties during ripening stage showed the peak value at the level of N250, being remarkable different with other treatments. The protein contents in grains of Zhongyuandan32 showed the peak value at the level of N200, Longfu208 at N250 and Gaoyou115 at N300. These treatments were remarkable different with other treatments.6. The relationship of nitrogen application and biomass fresh weight, biomass dry weight, protein yield, TDN and NE of silage maize showed a quadratic curve. The biomass fresh weight of Zhongyuandan32 showed the highest value at level of N200, but Longfu208 and Gaoyou115 at N250. There was remarkable difference with other treatments. According to the biomass dry weight, the highest was N250, and N250 treatment had a marked difference from other treatments. The protein yield of these varieties showed the peak value at the level of N250, the difference between N250 and N200 of Zhongyuandan32 wasn't significant, however, there had a marked difference from other treatments. Protein yield of Longfu208 and Gaoyou115 was remarkable difference among all nitrogen application treatments. Under the condition of the same nitrogen dosage, the biomass biomass fresh weight in Gaoyou115 was higher than other varieties, and the biomass biomass dry weight, protein yield of Longfu208 were highest.7. The optimal nitrogen application was selected by comprehensive consideration with the biomass fresh weight and protein yield of silage maize. Zhongyuandan32 was N200, and N250 was optimal to Longfu208 and Gaoyou115. From biomass dry weight, N250 was the optimal nitrogen application. Gaoyou115 was the optimal variety on biomass fresh weight, and Longfu208 on biomass dry weigh and protein contents.