Effect Of Nitrogen Application Rate On Yield And Nutrition Quality Of Japonica Rice In Cold Region

Nitrogen is the main nutrient in rice production, which plays an important role in the rice growth and development, yield and quality formation. However, it is common that the application rates of nitrogen fertilizer were excessive in rice production, leading to decreased quality, increased production costs, and severe environmental pollution. To realize the goal of high yield and quality, improve nitrogen use efficiency and ensure agricultural ecological security, we should first consider the characteristics of the nitrogen requirement in different rice varieties, and determine the optimum amount of nitrogen. In this paper, three japonica rice cultivar, Longdao 5(LD 5), Mudanjiang 30(MDJ 30) and Songjing 6(SJ 6) were used as the test materials, and six application rates of nitrogen fertilizer(0, 50, 100, 150, 200 and 250kg/hm2) were set to study the effect of nitrogen application rates on the dynamic of plant height and tiller, shoot biomass, nitrogen accumulation and allocation, yield and its components, and nutritional quality. So as to figure out the effect of nitrogen application rates on the growth of rice, determine the dry mass accumulation character, and explore the optimum amount of nitrogen for high yield and quality of rice. The main results were as follows:(1) Application of nitrogen fertilizer could increase the plant height, effective tiller number, fresh weight and dry weight of shoot. Sensitive degree of plant height and shoots fresh weight response to nitrogen fertilizer varied depending on the genotype. Appropriate amount of nitrogen fertilizer could promote tillering early and quick growth, reduced extinction rate of tillering, thereby improving the effective tiller number. Nitrogen could make the rice plants to advance into the rapid accumulation of dry matter, and increase the maximum dry matter accumulation rate, so as to promote the shoot dry matter accumulation of rice in cold region.(2) Exactly, with the increase of nitrogen, nitrogen uptake content in the shoot at regreening and jointing stage, and nitrogen content in the shoot at heading and filling stage increased, which meets the nitrogen requirement of the plant during the middle and late growth stage. With increasing of nitrogen, the translocation amount of nitrogen(TNA) in grains from the vegetative organ increased, and the proportion of that to total nitrogen increased gradually. The yield increased with the increase of TNA in grains from the vegetative organ, but beyond a certain range, the yield showed a downward trend.(3) With the increase of the amount of nitrogen, N contribution rate(NCR),recovery efficiency(REN) and agronomic N use efficiency(AEN) of LD 5, MDJ 30 and SJ 6 was first increased and then decreased, while nitrogen physiological efficiency(PEN) and partial factor productivity showed a tendency of decrease. LD 5 has a higher AEN, and its REN was greater under low nitrogen than other cultivars. While, SJ 6 has a higher PEN.(4) The application of nitrogen fertilizer could significantly increase the effective panicle number per square meter, grain number per spike and the yield of rice. The response to nitrogen of yield components of different varieties was different. Combined with the price of rice and fertilizer that year, according to the fitting equation of rice yield(y) and nitrogen(x), the highest yield of LD 5, MDJ 30 and SJ 6 were 6210.1, 6046.8 and 7306.8kg/hm2, which were achieved with application nitrogen rates of 241.7, 200 and 241.7kg/hm2, respectively. The optimum yield of LD 5, MDJ 30 and SJ 6 were 6207.7, 6046.3 and 7306.8kg/hm2, which were achieved with application nitrogen rates of 233.3, 191.7 and 241.7 kg/hm2, respectively.(5) The application of nitrogen fertilizer could significantly improve the grain protein content, protein yield, total amino acids, essential amino acids(EAA), nutritional index(NI), essential amino acid index(EAAI) and biological value(BV). The highest content of EAA in LD 5 and MDJ 30 were under N250 treatment, while that in SJ 6 was under N150 treatment. NI of rice grain protein improved with the increase of nitrogen. And the greatest EAAI and BV of LD 5, MDJ 30 and SJ 6 were under the treatments of N100, N50 and N150, respectively. The magnitude order of EAAI and BV were MDJ 30> SJ 6> LD 5.