Effects Of Nitrogen Fertilizer On Nitrogen Metabolism, Yield And Quality Of Cold-Region Rice Under Different Irrigation Methods

The increasingly scarcity of water resource and unreasonable nitrogen fertilizer have caused serious pollution to the environment. It is urgent to explore the effects of different irrigation methods combined with the application of nitrogen fertilizer on nitrogen metabolism and yield quality of cold-region rice, ultimately determine the most appropriate irrigation methods and nitrogen fertilizer combinations to achieve high and stable yield of rice. In this experiment, Dongnong425and Songjing6were used as materials to explore the effects that the five nitrogen application pure nitrogen0kg/hm2(F0),75kg/hm2(F1),150kg/hm2(F2),225kg/hm2(F3),300kg/hm2(F4)under the four levels of irrigation methods(conventional irrigation(W1), light dry-wet alternated irrigation(W2), dry-wet alternated irrigation (W3), and weight dry-wet alternated irrigation(W4)) on nitrogen metabolism enzyme activity, protein content, nitrogen use efficiency, yield and quality of cold-region rice. It revealed the regulatory role of nitrogen application had on nitrogen metabolism, yield and quality under different irrigation methods,and then cleared that the appropriate irrigation methods and reasonable application level of nitrogen fertilizer could provide a theoretical basis and technical support for water-saving irrigation and rational application of nitrogen fertilizer of Japonica rice from cold zone.The results were as follows:1. The nitrate reductase(NR) and glutamine synthetase(GS) activities of Dongnong425and Songjing6function leaves showed a single peak curve, and reached the peak at heading stage. NR and GS activities of leaves in Dongnong425and Songjing6under W2treatment were significantly higher than the other irrigation treatments.NR and GS activities of Dongnong425and Songjing6of leaves under F3treatment were significantly higher than the other nitrogen application treatments. The combination of W2and F3could improve NR and GS activities of leaves. NR and GS activities of leaves in Dongnong425were higher than that of Songjing6.2. Variation trend of protein content of grain in Dongnong425and Songjing6increased from the7th days after heading, and reached the peak at the14th day, then decreased; from the21th days after heading, Grain protein content under W3and W4treatment were significantly higher than W1and W2treatment, and W2treatment was significantly higher than that of W1. On the14th day of heading, grain protein content of F3treatment was higher than the other nitrogen application treatment. Grain protein content growth degree of rice were generally the same under the same treatment, Dongnong425were higher than that of Songjing6.3. The change of nitrogen content of leaves in Dongnong425and Songjing6were generally the same during the whole growth period, which decreased with the growth period. The nitrogen content under Tillering to heading stage decreased slowly, and from heading stage to full maturity decreased rapidly. Nitrogen content of Dongnong425and Songjing6under W2treatment were significantly higher than that of the other irrigation treatments, and were significantly higher under F3treatment than that of the other nitrogen application treatments. Plant nitrogen content of Dongnong425was higher than that of Songjing6.4. The change of nitrogen uptake in Dongnong425and Songjing6were generally the same during the whole growth period, plant nitrogen uptake in early growth stage was little, increased slightly at the jointing stage and rapidly after heading, and reached the highest at the mature period. Plant nitrogen uptake of Dongnong425was higher than that of Songjing6.5. Spikelets per panicle and seed setting rate of Dongnong425and Songjing6under W2treatment were significantly higher than that under W3and W4treatments, and had no significant difference with W1treatment. Yield of Dongnong425and Songjing6under W2treatment was significantly higher than the other irrigation treatments; yield of Dongnong425and Songjing6under W2and F3treatment was significantly higher than the other treatments. Yield of Dongnong425were higher than that of Songjing6.6. Brown rice rate, head rice rate, amylose content of Dongnong425and Songjing6under W2treatment were significantly higher than the other irrigation treatments, chalky grain rate was significantly lower than the other treatments. Protein content of W4treatment was significantly higher than that of W1and W2, and had no significant difference with W3.