Influencing Mechanism For Effcient Resource Utilization And Yield Of Rapeseed Under Key Cultivation Measures

In view of the problems of insufficient exploitation of the interaction potential between existing cultivation techniques and resource allocation,low resource utilization rate,high investment and low benefit in rapeseed production in China,the change rule and response mechanism of rapeseed resource utilization efficiency of temperature,light,water and fertilizer under different cultivation measures were studied.In this study,three single factor experiments were conducted in the experimental field of Huazhong Agricultural University from 2018 to 20213.Two varieties of rapeseed,Huaza 62（conventional high yield）and Huayouza 158（high quality and high oil）,were selected for the experiment,and three sowing dates were designed with gradient S1（early sowing on September 20）,S2（suitable sowing on October 1）and S3（late sowing on October 10）.Three nitrogen fertilizer gradients were N1(low N 120kg hm^-2),N2(suitable N 240kg hm^-2)and N3(high N 360kg hm^-2).Three density gradients D1(low density 30×10⁴ plant hm^-2),D2(suitable density 45×10⁴ plant hm^-2)and D3(high density 60×10⁴ plant hm^-2)were used to determine the yield and yield composition,quality formation,utilization efficiency of temperature,light,water and fertilizer resources,and root architecture of underground part.Growth hormone,nitrogen metabolism enzyme and canopy structure,photosynthetic characteristics and C,N metabolism related enzyme activities in shoot.The formation mechanism of resource utilization difference under different cultivation modes and its influence on rape yield and quality were analyzed to provide a theoretical basis for the efficient utilization of rape resources,optimize rape planting mode,and finally realize the efficient utilization of rape resources and high yield and quality.The results of this experiment are as follows:（1）In the three experiments,timely sowing（S2）,increasing nitrogen fertilizer（N3）and increasing planting density（D3）were beneficial to improve the absorption and utilization of light,temperature,water and fertilizer resources and realize the improvement of yield and oil yield.S2 increased by 3.6%-12.3%and 23.1%-38.3%compared with S1 and S3,N3 increased by 9.5%-37.8%and 27.1%-49.2%compared with N2 and N1,D3 increased by 10.8%-18.3%and 3.8%-8.7%compared with D1 and D2.Correlation analysis showed that the change of sowing date,nitrogen application rate and planting density could regulate the yield and quality of rapeseed mainly by affecting the production efficiency of accumulated temperature,light energy use efficiency and nitrogen use efficiency,respectively.（2）the delayed sowing date on grain yield and quality of rapeseed,sowing date delaying,rape growth period shorten,the utilization rate of effective accumulated temperature and effective accumulated temperature of declining fertility period,rape seedling root growth hormones,cut down the content of IAA,ABA and SA,CTK content at first and lowered later,due to large rainfall S1 sowing period,increase the synthesis of ABA,The root phenotype and nitrogen metabolism enzyme activity were S2>S1>S3 at the beginning of the moss stage.Compared with S1 and S3,leaf carbon and nitrogen metabolism enzymes,such as Ru BP carboxylase,FBP,SPS,GS and GOGAT,increased in S2,leaf carbon and nitrogen metabolism,and a large number of carbohydrates and proteins were synthesized to promote leaf growth.Under S2condition,canopy light-cutting rate,leaf area index and photosynthetic performance of leaves from moss stage to silique stage were higher than those of S1 and S3,and more photosynthates in leaves were transported to grains through a series of transformation,which promoted the increase of silique number per plant,grains per horn and yield per plant,and finally increased yield.The glucose content of S2 treatment middle tablet was significantly higher than that of morning and evening sowing.The accumulation of accumulated temperature in plant was beneficial to the synthesis of glucose in leaves,promoting lipid metabolism of grains and improving the oil content of grains.Therefore,timely sowing（S2）can make full use of temperature and light resources,improve the production efficiency of accumulated temperature during the whole growth period,and has a positive effect on the improvement of rape yield and quality.（3）Increased application of nitrogen fertilizer had a certain effect on both the upper and underground parts of the rapeseed field.With the increase of nitrogen fertilizer application,the contents of IAA and SA related to root growth increased,while the contents of ABA and CTK decreased,which promoted the occurrence of lateral roots and inhibited the growth of taproot.At the same time,the activities of NR and GOGAT related enzymes in root nitrogen metabolism increased,the root injury flow and the contents of amino acids and soluble sugars increased,which promoted the synthesis and transport of protein,and the nitrogen content in all parts of the plant increased.Root absorption ability of aboveground has a lot of positive feedback effect,the plant has more leaf number and larger light hinges area,improve the utilization efficiency of light energy,more light interception and enhances the blade carbon metabolism related enzymes Ru BP carboxylase place,FBPase enzyme and nitrogen metabolism related enzyme GS,incorporated into the activity of enzyme,increase the chlorophyll content and photosynthetic rate,Photosynthetic products increase.The increase of light energy utilization rate was conducive to the increase of’source’and the increase of’reservoir’.The thickness of pod layer,the number of pod per plant and the weight of one thousand seeds were significantly increased,and the grain yield was improved.However,excessive light energy absorption inhibited the SPS enzyme activity of pod and leaf,increased the protein content of seed and reduced the oil content of seed.However,the increase of yield more than made up for the oil loss caused by the decrease of oil content.Therefore,increasing nitrogen fertilizer application in the suitable range of rapeseed growth to improve the light energy efficiency of the plant is beneficial to the increase of rapeseed yield and efficiency.（4）Increasing density has certain influence on the upper and underground parts of rapeseed field.The spatial structure of population root phenotype was enlarged by increasing the density,SA content increased,NR and GS activities of nitrogen metabolism related enzymes increased,root injury flow and amino acid content increased,which promoted the absorption and transport of soil nutrients by roots,and nitrogen use efficiency increased.When the density was increased,the GS and GOGAT enzyme activities increased,which promoted the absorption and transformation of nitrogen nutrition,increased the nitrogen content in different parts of rape,and further improved the nitrogen use efficiency of rape.The improvement effect brought by population structure optimization was much higher than the negative effect brought by dense planting on individuals.The increase of population leaf number,LAI and canopy intercept rate not only promoted the improvement of’source’,but also increased the capacity of’reservoir’.When the population scones number increased,the yield increased.Nitrogen use efficiency increased the soluble protein content of grain,adverse to the formation of oil body to reduce the oil content of seed,but of the actual production to improve greatly increase the output per unit area,as a result,proper planting density increases to rape nitrogen use efficiency,achieve rape yield and quality of ascending simultaneously.