The Effects Of Planting Density On Stems Lodging Resistance And Yield For Different Plant Height Maize Varieties

In the actual production of maize,the increase of planting density usually results in the mutual occlusion of leaves,the poor light transmittance of population,the decline of photosynthetic capacity of leaves,the intensification of competition between water and fertilizer,the low slender and fragile hardness of stems,and the aggravation of lodging.The phenomenon of lodging is one of the main reasons that hinder maize yield from achieving the goal of high and stable yield.In this experiment,the maize varieties with different plant height and density tolerance are selected as materials,the split plot design is adopted and the five planting densities are set up.The differences of plant external morphological index,dry matter accumulation,stem mechanical index,internode chemical composition,lodging rate,yield and related characters under different planting densities are systematically discussed during the main growing period of maize in order to provide a theoretical basis for the specific cultivation system of high-yield and lodging-resistant varieties of maize and the close planting of lodging resistant varieties.The main results are as follows:1.With the increase of planting density,the plant height,ear height,ear height coefficient,stem length and leaf area index of the three cultivars increase first and then decrease,while the stem diameter decreases with the increase of planting density.The variation range of high-stalk variety Jinongda 928 is the largest among varieties,and that of low-stalk variety Jinongda 935is the smallest.2.During the whole growth period,with the increase of density,the above-ground dry matter accumulation of the three varieties gradually increases,and the low-stalk variety Jinongda 935 accumulates the most under high density.However,the growth rate is different in different stages.Before the stage of silk,the increase rate of dry matter accumulation in shoot is small.After the stage of silk,the maize plants are beginning to enter reproductive growth,and the accumulation rate increases accordingly.With the increase of planting density,the dry matter weight per unit stem length of the base stem node of maize decreases gradually,and Jinongda 935 decreases most gently.3.With the increase of density and node position,the puncture strength and the crush strength between 2-4 internodes of stem base gradually decrease.With the advance of maize growth period,puncture strength and crushing strength gradually increase.There are significant differences among varieties.The two mechanical indexes of low-stalk variety Jinongda 935 are higher than those of normal plant height variety Jinongda 778 and high-stalk variety Jinongda4.With the increase of planting density and the growth of maize,the main chemical composition in the stem:the cellulose content,hemicellulose content and lignin content all reduced.The difference between the density treatments is significant.The chemical composition of high-stalk variety Jinongda 928 stem decreases most with the increase of density,and low-stalk variety Jinongda 935 is the smallest.5.The lodging rate of the three varieties increases with the increase of density.Comparison between varieties,the lodging rate of low-stalk variety Jinongda 935 is the least affected by the density,and the lodging rate of high-stalk variety Jinongda 928 is the most affected by the density.The correlation analysis shows that the lodging rate is significantly positively correlates with the plant height,ear height and the stem length,and significantly negatively correlates with the stem diameter,the puncture strength and the crush strength of stem base.It was also significantly negatively correlates with the hemicellulose content,lignin content and cellulose content.6.With the increase of planting density,the yield trends of the three varieties are the same,which gradually increase and then decrease with the increase of planting density.According to the regression analysis,the planting densities corresponding to the highest yields of the three varieties are 67,400 plants/hm~2,72,600 plants/hm~2,and 69,400 plants/hm~2,respectively.It can be seen that the low-stalk variety Jinongda 935 is more dense than the other two varieties and is suitable for high-density planting.