Effects Of Planting Density And Nitrogen Fertilizer On Growth,Yield And Nitrogen Utilization Of Dwarf Rape

For the winter brassica napus direct sowing machine,it is not only an important development trend of rapeseed production mechanization in the Yangtze River Basin,but also it has become a hot research topic on rapeseed cultivation.However,rapeseed varieties that are suitable for mechanized production are relatively scarce,especially in the main producing areas of rapeseed of the Sichuan Basin.The existing varieties of rapeseed cultivars are high in height and late in maturity and their resistance to density and lodging is poor.Therefore,it is necessary to explore and clarify the growth,yield and utilization of nitrogen characteristics of Brassica napus dwarf,which can provide a scientific basis for the application of Brassica napus dwarf in mechanized production and its high yield and high efficiency.In this paper,Brassica napus dwarf MJ01 was used as experimental material to study the effects of different planting densities(M2:2 ×104/667m2,M4:4)and nitrogen fertilizer rate(N0:0kg N/667m2;N9:9kg N/667m2;N12:12kg N/667m2;N15:15kg N/667m2)on the growth,yield and nitrogen utilization of the dwarf rapeseed in a modern agricultural research and development base of Sichuan Agricultural University from 2014 to 2015.The base is located in Qiyuan Town of Chongzhou City.At the same time,we compared the high stalk rapeseed variety Chuanyou 36 to the dwarf rapeseed MJ01 in the same field,and set up two kinds of densities(M2,M4)and nitrogen levels(N9,N15),and then contrasted and analyzed the agronomic traits,yield components,dry matter and nitrogen distribution and the nitrogen utilization characteristics of dwarf rapeseed.The results showed that:The dwarf rapeseed MJ01 has the growth characteristics of budding,early flowering and early maturity.Planting density(M2,M4)and nitrogen application rate(N9,N12,N15)have significant effects on the growth of the dwarf rapeseed in seedling stage and flowering stage.The planting density has a significant effect on the plant height in the mature period and the number of branches of the dwarf rapeseed.And the nitrogen application rate has significant effectson the plant height in the mature period,the length of main shoots,the number of primary branches,number of protocarp and the proportion of main products.Compared with the high-stalked rapeseed,the plant height,branching part,main length and main pod number of the dwarf rapeseed are significantly lower,but the proportion of the primary branch and the main fruit was not obvious different.The resistance to density of the Dwarf rapeseed is significantly stronger than that of high-stalked rapeseed.Planting density and nitrogen application rate has significant effects on the organs in mature period and the accumulation of dry matter for the dwarf rapeseed.The amount of nitrogen applied and the density of planting had no significant effect on the dry matter distribution in mature period of the dwarf rapeseed.In the case of dry matter distribution,the kernel proportion(%)of the dwarf rapeseed is lower than that of high-stalked rapeseed.However,increasing the density favors the increase in the kernel proportion of the dwarf rapeseed(%)At the mature stage of dwarf rapeseed,the planting density had no significant effect on nitrogen uptake and distribution,but on the nitrogen application rate.With the increase of the planting density,nitrogen ratio of the kernel(%)and nitrogen ratio(%)of stem are increasing.Increasing nitrogen fertilizer significantly can reduce the nitrogen ratio of the kernel(%).Compared with high-stalked rapeseed,the nitrogen ratio of the kernel(%)of the dwarf rapeseed is lower,and the increase of nitrogen fertilizer significantly can decrease the nitrogen ratio the kernel(%)of the dwarf rapeseed.The planting density has a significant effect on the contribution rate of nitrogen fertilizer to dwarf rapeseed,and the nitrogen application rate has a significant effect on the partial productivity of nitrogen fertilizer.With the increase of nitrogen application rate,the partial productivity of nitrogen fertilizer in dwarf rape shows a decreasing trend,and the contribution rate of nitrogen fertilizer and apparent utilization rate of nitrogen fertilizer increased.Nitrogen absorptivity efficiency and nitrogen use efficiency were the highest in N12.Compared with high-stalked rapeseed,the partial productivity and nitrogen use efficiency of Dwarf rapeseed were higher.The planting density has no significant effect on the yield of dwarf rapeseed,but has a significant effect on nitrogen application rate.The difference of grain yield between N12 and N15 was not remarkable,but they were much higher than those of N9.At the same level of density and nitrogen application rate,there was no significant differences in grain yield between dwarf rapeseed and high-stem rapeseed.The tolerance and fertilizer resistance of Dwarf rapeseed were significant stronger than that of high-stem rapeseed.Under the two sowing density(M2,M4),and nitrogen application rate in the range of 12-15kg N/667m2,dwarf rapeseed can obtain higher grain yield(184-196kg/667m2)Based on the above results,the suitable for nitrogen application rate was 12 kg N/667 m2,and the planting density was 2-4 million/667 m2.