Effects Of Chemical Regulation On Yield Formation And Suitable Mechanical Harvesting Characters Of Xiangnongyu No.27

The cotton field in the Dongting Lake area of Hunan has been restructured,and the area of summer maize has expanded year by year.In order to clarify the appropriate chemical regulation measures for summer maize in this area and improve the high-yield cultivation technique system for machine-harvesting summer maize,the field experiments were conducted out under three densities(60,000 plants/hm~2,75,000 plants/hm~2,90,000plants/hm~2)and three kinds of chemical control treatment methods(one time control at early jointing stage,two times control at jointing and big trumpet stage,clear water control)with summer maize variety Xiangnongyu No.27 selected by Hunan Agricultural University and chemical regulator amines·ethephon were used as the experimental materials in 2017-2018.The main results are as follows:(1)The leaf area index(LAI)of Xiangnongyu No.27 significantly increased with the increase of density,and decreased with the increase of chemical control times,but the decrease was not significant.(2)The accumulation of dry matter in leaves,stems,loquat leaves and spike axis increased with increase of density,chemical regulation inhibited the accumulation of dry matter in leaves and stems,but one time chemical regulation treatment promoted dry matter accumulation in loquat leaves.The effect of chemical control on the dry matter accumulation of spike axis was not significant under medium(75,000 plants/hm~2)and low density(60,000plants/hm~2),but the dry matter of spike axis was significantly inhibited under high density(90000 plants/hm~2).Under the condition that the summer maize group was large and grew well,one time chemical regulator at early jointing stage contributed to the accumulation of dry matter of population.(3)The yield of Xiangnongyu No.27 increased significantly with the increase of density.The climate was bad in 2017,and in the case of weak plant population,chemical regulation treatment inhibited plant growth,caused a significant reduction of yield.Under normal climate conditions in 2018,chemical regulation had significant effect on yield,andthe maximum yield(11340.0 kg/hm~2)was obtained under high density and one time chemical regulation treatment.(4)The plant height and ear height of summer maize increased with the increase of density,and decreased with the increase of chemical control times.The plant height uniformity increased with the increase of density,and the ear height uniformity was higher under medium density(75,000plants/hm~2),which is 30.31.Chemical regulation effectively improved plant height uniformity and ear height uniformity,which was conducive to machine harvesting,and one time chemical control had the better effect.(5)The plucking force and puncture strength of stalk decreased with the increase of density,and the treatment was the largest with one time chemical control.The lodging rate of Xiangnongyu 27 was generally increased with the increase of density,and decreased with the increase of times of chemical regulation.Chemical control could reduce lodging rate caused by bad weather and high density planting,and avoid maize yield reduction.(6)Chemical regulation reduced the grain moisture content in the late filling stage.Due to the interannual difference and climate difference,the effect of chemical regulation and density interaction on grain moisture content was the lowest in the late filling stage in2017,the lowest was 27.00%,and the grain moisture content performed lower on two times chemical control in 2018,the lowest was 20.2 %.And the grain moisture content significantly decreased under the conditions of medium and low density.On the whole,under normal climate and good growth of summer maize population,the yield of Xiangnongyu No.27 was highest under high-density(90,000 plants/hm~2)and one time control at early jointing stage,and which improved the machine-harvesting characters by reducing plant height and ear position,improving the uniformity of plant height and ear height,increasing the plucking force and puncture strength of the stem,and improving the grain dehydration rate at the late filling stage.