Effects Of Nitrogen Application Rate On Yield And Nitrogen Uptake And Utilization Of New Semi-dwarf Rapeseed Variety "jiayou JS-1"

Sichuan Province is located in the upper reaches of the Yangtze River.As an important dominant crop,rapeseed production has ranked first in the country in recent years.With the changes in the quantity and structure of rural labor force,direct seeding and mechanized harvesting of winter rapeseed have become an inevitable trend of light and simplified production development.However,most of the rapeseed cultivars grown in our province are tall,and the plant height is generally above 200 cm,which is easy to fall,which not only affects the yield and quality of rapeseed,but also is not conducive to mechanized harvesting of rapeseed."Jiayou JS-1" is the first new semi-dwarf rapeseed variety approved by Sichuan Province.Based on the improved varieties and methods,the nitrogen fertilizer effect and suitable yield of high yield and efficiency under the condition of mechanized direct seeding were discussed.The cultivation and utilization of new dwarf varieties provide scientific reference.To this end,under the rice-oil rotation system of Guanghan City,Sichuan Province,from 2018 to 2019,different nitrogen levels(0-360 kg N/hm~2)were applied to the yield and nitrogen of a new semi-dwarf rapeseed "Jiayou JS-1" Field Experiment Study on the Influence of Biomass Absorption and Utilization.The main results are as follows:(1)Compared with the non-nitrogen treatment,the biological yield and grain yield of the nitrogen treatment increased significantly.With the increase of nitrogen application rate,the biomass yield and grain yield showed a trend of rising first and then decreasing.The maximum value was obtained when the nitrogen application rate was 270kg/hm~2;while the harvest index increased with the increase of nitrogen application rate.When the nitrogen application rate was 270kg/hm~2-360kg/hm~2,there was no significant difference in grain yield and harvest index of semi-dwarf rape.(2)As the growth period progressed,the nitrogen content in the leaves gradually decreased,while the soluble sugar content and carbon-to-nitrogen ratio showed a trend of first increasing and then decreasing,reaching the maximum in the bud period.As the amount of nitrogen applied increased,the nitrogen content of the leaves gradually increased,while the soluble sugar content and carbon to nitrogen ratio gradually decreased.(3)With the increase of the number of days after flowering,the total nitrogen content of the main sequence carambola and branch carob changed little,while the soluble sugar content and carbon-nitrogen ratio showed a downward trend.With the increase of nitrogen application,the total nitrogen content of the main sequence carambola and branched carambola showed an increasing trend,while the carbon to nitrogen ratio of the main sequence carob and branched carob showed a downward trend.Within the nitrogen application range of 180kg/hm~2-270kg/hm~2,there was no significant difference in the total nitrogen content,soluble sugar content and carbon-nitrogen ratio of main sequence carob and branch carob.(4)During the growth period of rapeseed,dry matter and nitrogen accumulation in plants,stems and leaves showed an increasing trend and then decreased,while dry matter and nitrogen accumulation in reproductive organs showed an upward trend.In the range of 0-270kg/hm~2 nitrogen application,dry matter accumulation and nitrogen accumulation of plants and various organs(stems,leaves,reproductive organs)gradually increased,but when the amount of nitrogen applied exceeded 270kg/hm~2,plants and different organs(stem,Leaves,reproductive organs)dry matter accumulation and nitrogen accumulation are similar or reduced.When the amount of nitrogen applied exceeds 270kg/hm~2,the distribution ratio of dry matter and nitrogen in vegetative organs(stems and leaves)in the late growth period is increased,while the distribution ratio of dry matter and nitrogen in reproductive organs is reduced.(5)The start time and end time of rapid accumulation of dry matter in semi-dwarf rape is later than the start time and end time of rapid accumulation of nitrogen,which provides a sufficient nutrient basis for plant morphogenesis and dry matter accumulation.In the range of 180kg/hm~2-270kg/hm~2 nitrogen application,the duration of rapid accumulation of dry matter and nitrogen is prolonged,the termination time of rapid accumulation of dry matter and nitrogen is postponed,and the maximum rate of dry matter accumulation is delayed.(6)Compared with the treatment without nitrogen application,the nitrogen accumulation of the plants at the mature stage of nitrogen application treatment increased significantly.The nitrogen accumulation,agronomic utilization rate of nitrogen fertilizer,apparent utilization rate of nitrogen fertilizer and physiological nitrogen efficiency of N270 treatment at the mature stage were higher than that of N90,N180 and N360 treatment,while the nitrogen harvest index was lower than that of N90,N180 and N360 treatment.There was no significant difference in nitrogen absorption efficiency,nitrogen utilization efficiency,physiological nitrogen efficiency and nitrogen harvest index between N180 treatment and N270 treatment.Considering the comprehensive grain yield and nitrogen fertilizer utilization rate,under the condition of direct seeding of rice stubble in the Chengdu Plain,the reasonable nitrogen application rate of semi-dwarf rape "Jiayou JS-1" is 180kg/hm~2-270kg/hm~2,which can better achieve rapeseed High yield and efficient use of nitrogen fertilizer.