| Rice is an important food crop in the world,and about half of the world's people eat rice as their staple food.China is a major producer of rice,and its planting area is second only to India,which is also the country's largest consumer of rice.The high-yield,high-quality and high-efficiency coordination of rice has important significance for China's grain production.However,since the founding of the People's Republic of China,due to the limitations of China's basic national conditions and people's material needs and productivity,many research scholars in China have used high yield as the main breeding goal and cultivation based on high yield.Technology is so limited that there are relatively few studies on the selection,improvement,and cultivation of rice quality.In recent years,with the development of economy,social progress and the improvement of people's living standards,people's demands for rice quality have also become higher and higher.Rice with excellent quality has attracted more and more attention.Therefore,the selection of high-quality rice varieties and the cultivation of high-quality rice are urgently needed.The quality of rice is mainly influenced by heredity,ecological area and cultivation measures.Only those varieties with excellent rice quality can be exhibited only with suitable cultivation measures within the suitable ecological area for growth.The formation stage of rice quality is the process of accumulation of carbon and nitrogen assimilate during the grain filling stage.Therefore,nitrogen nutrition is an important limiting factor affecting the yield and quality of rice,and plays an important role in rice production.The application of a large amount of nitrogenous fertilizer in rice production may increase rice yield and income and increase rice quality.However,excessive application of nitrogen fertilizer greatly increases the production cost of rice.At the same time,nitrogen fertilizer applied to rice fields is only absorbed and utilized by a small amount of rice.Most of the nitrogenous fertilizers are lost due to volatilization and leaching,which results in a series of environmental pollution problems such as eutrophication,soil compaction,and acid rain,which pose potential threats to people's health and sustainable agricultural development.Therefore,determining the suitable nitrogen application interval and increasing the nitrogen uptake and utilization efficiency of rice based on the application of nitrogen fertilizer at the present stage is of vital importance to the increase of nitrogen fertilizer efficiency and the sustainable development of rice production.The planting density of rice is also the main factor affecting its yield and quality.Planting density has a greater impact on the formation of rice population structure,mainly because the configuration of different rows of burrows has changed the state of competition among the individual individuals for environmental resources.Thus affecting individual and population growth conditions;under proper planting density conditions,rice can make fuller use of natural resources to achieve coordinated development of rice individuals-populations,so as to achieve higher yields,so to determine the rational cultivation of rice cultivation Density is very important for the efficient use of nitrogen fertilizer in rice,and has important practical significance for the establishment of high-quality and high-quality rice cultivation techniques.At the present stage,there are many domestic and foreign scholars on the impact of nitrogen application rate and planting density on rice yield,which has laid a solid theoretical and practical basis for high yield,high quality,and efficient cultivation of rice,and nitrogen fertilizer application and planting density.The effect on rice quality is rarely researched.Therefore,based on previous studies,the japonica rice varieties Jijing 88 and Tongyu 99 were used as experimental materials.Through field trials,three densification and nitrogen reduction cultivation models were set up.The effects of nitrogen application rate and transplanting density on rice quality of indica rice were studied.The appropriate nitrogen application level and planting density were explored in order to lay a theoretical foundation for the high quality and high efficient cultivation techniques of japonica rice in cold region.The results of this study are as follows:1.The level of nitrogen application and planting density had a significant effect on the brown rice rate and whole polished rice.The percentage of brown rice and whole polished rice increased first and then decreased with the increase of planting density and reduction of nitrogen fertilizer.Nitrogen application rate and planting density had no significant effect on rice polished rice rate.The processing quality of rice also differed significantly among different varieties.Jixi 88 performed well under the conditions of F1 treatment.Tongyu 99 performed better under the F2 treatment conditions.2.Nitrogen application rate and planting density had extremely significant effects on chalky white grain rate,chalkiness,crumb(total),small crushed rice,imperfect grain,and yellow rice,chalky grain rate,chalkiness,Both the crumb(total amount)and the yellow granules showed a tendency of decreasing first and then increasing with the increase of planting density and reduction of nitrogen fertilizer.With the increase of planting density and reduction of nitrogen fertilizer,imperfect grain has the tendency of increasing first and then decreasing.The effects of nitrogen application and planting density on the whiteness,transparency and whiteness of rice were not significant.The appearance quality of rice was also significantly different among different varieties.Jixi 88 had better appearance quality under F1 treatment conditions,Tongyu 99 performed better under F2 treatment conditions.3.The effects of nitrogen application and planting density on the moisture content,protein content,amylose content and taste of rice were extremely significant.The water content,amylose content and the overall taste were increased first with the increase of planting density and reduction of nitrogen fertilizer.After reducing the trend.With the increase of planting density and reduction of nitrogen fertilizer,the protein content decreased first and then increased.The taste quality of rice is also different between different varieties.Jixi 88 has better appearance quality under F1 treatment conditions,Tongyu 99 has better taste quality under F2 treatment conditions.4.The results of this study indicate that the rice quality of Jijing 88 and Tongyu 99 is not consistent with the density-reducing and nitrogen-reducing cultivation model.Jijing 88 has better rice comprehensive quality under F1 treatment conditions.Tongyu 99 is under F2 treatment conditions.The comprehensive quality of rice is relatively good.According to the characteristics of different varieties,increasing the planting density and reducing the amount of nitrogen fertilizer can improve rice quality. |
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