Chemical Regulation Of High Yield And Nitrogen Utilization Efficiency Of Varied Genotypes Of Sorghum (Sorghum Bicolor,(L.) Moench.)

Field experiments were set up in Xinxiang experimental site of the Institute of Crop Science,Chinese Academy of Agricultural Sciences（ICS-CAAS）in 2020 and 2021,to investigated the effect of Ethylene-Chlormequat-Potassium（ECK）,which invented by the Institute of Crop Science,Chinese Academy of Agricultural Sciences on sorghum（Sorghum bicolor,（L.）Moench.）yield and nitrogen utilization efficiency.In detail,the field experiment included two types of sorghum varieties（dwarf Liaozhai 37 and medium-high straw Liaozhai19）,two spraying periods（nodulation and tasseling）and fours doses(0,0.75,1.5,and 2.25L·hm^-2)of ECK.Sorghum yield and yield components,dry matter accumulation and distribution,stalk physicochemical properties and mechanics,root development and N use efficiency were investigated.The results showed that.（1）ECK increased sorghum spike and kernel weight,which in turn increased sorghum yields.In terms of the ECK spraying period,sorghum yield was better when ECK spraying at sorghum 5-leaf stage than at the boot stage;while sorghum yield showed a trend of increasing and then decreasing with the increasing spraying dose of ECK,and the results of the two-year study showed that 0.75 L·hm^-2ECK at the 5-leaf stage was the most effective in increasing sorghum yield compared to the control treatment.Sorghum yield increased by 4.3%and 11.6%in 2020 and 2021,respectively,compared to the control treatment.（2）ECK decreased sorghum plant height and increased dry matter accumulation significantly.At physiological maturity stage,plant height of Liaozha37 and Liaozha19 under ECK treatment were decreased by 16.5%and 11.9%,respectively,compared to the control treatment,while leaf chlorophyll content of the above two sorghum varieties were increased by40.5%and 14.9%,respectively,and net assimilation rate and growth rate increased by 45.1%and 32.3%of Liao19,respectively.（3）ECK shortened sorghum length and the increased nodal thickness,nodal folding strength and puncture strength significantly,which improved the lodging resistance of sorghum stalks.Compared to the control,internode length,thickness,flexural strength and puncture strength under ECK treatment were occurred mainly at the 3rd and 4th nodes from the base of the aboveground stems,with 25.9%and 28.4%reduction in internode length,6.4%and 4.6%increase in internode thickness,22.0%and 29.9%increase in flexural strength,respectively.（4）ECK promoted sorghum root development and increased root dry weight accordingly.In terms of root conformation,root length,root surface area,root volume,and root diameter of Liaozha37 and Liaozha19 under ECK treatment were increased by 22.6%and 23.1%,26.7%and 40.6%,30.2%and 61.7%,5.8%and 20.9%,respectively,compared to the control,while root dry weight increased by an average of 16.2%and 19.6%for Liaozha37 and Liaozha19,respectively.（5）ECK improved nitrogen fertilizer utilization in sorghum,but there were significantly differences among two sorghum varieties.ECK treatment increased the nitrate reductase activity of Liaozha37 and promoted nitrogen metabolism,which in turn improved the nitrogen partial productivity（PFPN）and nitrogen agronomic efficiency（NAE）of sorghum.Compared to the control,PFPN and NAE of Liaozha37 under ECK were increased in average by 1.1%,8.2%and71.9%,respectively.