Effects Of EthDAH Application Period And Density On Lodging Resistance And Yield Of Maize Stalks

Appropriate chemical control and reasonable density planting are important technical measures to achieve abundant yield of maize with resistance to fall and stable yield and resistance to fall suitable for machine cultivation.The main problem in current production application is that the application period is not uniform,which leads to inconsistent application effects and in some cases even leads to maize yield reduction.In order to investigate the effects of Eth DAH application period and density on the formation of internodes at the base of the stalk and the characteristics of resistance to falling and yield formation of maize,a two-factor randomized group trial design was used in 2021-2022,with factor A being planting density,with two densities of 67,500 plants/hm2(high density treatment)and 45,000 plants/hm2(low density treatment).Factor B was the application period,and four chemical control levels,B1(no application as control),B2(6 leaf spread spray),B3(9 leaf spread spray)and B4(12 leaf spread spray),were set.Carbohydrate content,anatomical structure,mechanical strength and other traits related to yield resistance,as well as leaf area index,dry matter accumulation and yield components,in order to find the optimal application period for high yield resistance under dense maize planting conditions,with the following main results:1.The period and density of chemical control significantly affected plant morphology.Increasing planting density increased plant height,ear height and center of gravity height by 2.21%,2.83% and 1.92%,respectively.In contrast,Eth DAH treatments reduced plant height,ear height and center of gravity height of maize to different degrees,with 2.3%,7.1% and 4.6% reduction in plant height,ear height and center of gravity height in B2 treatment,10.1%,11.8% and 10.7% in B3 treatment and 11.6%,9.6% and 6.8% in B4 treatment,respectively.Overall,it showed that Eth DAH treatment at 6 leaf spread had weaker effect on maize plant dwarfing than 9and 12 leaf spread chemical control,9 leaf spread Eth DAH treatment had better effect on reduction of cob height and center of gravity height,while 12 leaf spread Eth DAH treatment had better effect on reduction of plant height.2.Increasing planting density reduced the slender and weak basal internodes of maize stalks,reduced fresh dry weight per unit length,material content per unit length,number and area of vascular bundles,and thinner skin thickness,which in turn led to reduced mechanical strength of the basal internodes and increased the risk of collapse occurrence.On average for both years,the average internode length(IL),internode diameter(ID),average fresh weight per unit length(FWUL)and dry weight per unit length(DWUL),soluble sugar(Su C),starch(St C),cellulose(CC)and lignin content(LC),number of vascular bundles per unit length size(N1,N2)and area(S1,S2)of internodes 3,5 and 7 at high density(A1),puncture strength(RPS)and bending strength(SBS)were reduced by 0.86%,5.03%,3.38%,6.08%,17.35%,8.01%,5.44%,8.82%,3.31%,4.67%,6.96%,5.71%,7.54%,and 10.99%,respectively,compared with low density(A2);the thickness of the 3rd,5th,and 7th internodes at high density(A1),7 intersegmental cortical thickness(CT)increased by 8.39% compared to low density(A2).3.Eth DAH treatment at different periods affected the stalk resistance characteristics of maize stalks to different degrees,which was mainly reflected in the basal internodes of stalks,6 spreading leaves application of Eth DAH(B2)to affect internodes 2-4,IL at internodes 3,5 and 7 was reduced by 9.96% compared to control(B1),ID,FWUL,DWUL,Su C,St C,CC,LC,N1,N2,S1,S2,CT,RPS and SBS were increased by 5.45%,26.05%,20.75%,11.46%,4.68%,10.33%,24.31%,15.15%,13.84%,9.41%,13.03%,19.86%,12.73%,and SBS,respectively,compared to the control(B1),36.09%,but there was also some compensatory elongation in internode length at internode 7 and above;9th spreading leaf application of Eth DAH(B3)mainly regulated internodes 3-6,and IL at internodes 3,5 and 7 was reduced by17.43% compared to control(B1),and ID,FWUL,DWUL,Su C,St C,CC,LC,N1,N2 S1,S2,CT,RPS and SBS were increased by 3.51%,22.28%,12.32%,12.49%,5.12%,10.36%,21.66%,15.22%,12.41%,10.08%,12.35%,20.31%,14.37% and30.65%,respectively,compared to the control(B1);12 spreading leaf application of Eth DAH(B4)mainly acted on internodes at 7 nodes and above,predominantly near the spike nodes,IL at 3rd,5th and 7th nodes was reduced by 6.62% compared to control(B1),ID,FWUL,DWUL,Su C,St C,CC,LC,N1,N2,S1,S2,CT,RPS and SBS at 3rd,5th and 7th nodes were increased compared to control(B1)by 6.07%,17.85%,18.88%,7.79%,3.54%,6.31%,15.42%,5.76%,3.55%,3.55%,3.86%,7.06%,7.53%,and 14.76%,respectively.4.Correlation analysis showed that SLR was negatively correlated with RPS and SBS,while RPS and SBS were negatively correlated with IL and IL/ID,and positively correlated with ID,FWUL,DWUL,CC,N1,N2,S1,S2,and CT,with CT contributing the most to the variation in internode mechanical strength.This indicates that foliar application of Eth DAH and increased planting density affects mechanical strength and thus its resistance to collapse mainly by regulating basal internode growth and influencing its morphological characteristics,material enrichment and anatomical structure,with length-to-thickness ratio and cortical thickness being the main traits,followed by anatomical structures such as number of small vascular bundles and material accumulation such as starch content.5.Although increasing density inhibited individual development and led to a decrease in the number of ears and 100 grain weight,it increased maize grain yield due to an increase in the effective number of ears per unit area,higher leaf area index and more dry matter accumulation.Although the foliar spray Eth DAH had a certain inhibitory effect on plant growth and tended to reduce the dry matter accumulation of individual plants,it improved the stalk resistance to fall,reduced field collapse,and promoted grouting and fruit set,thus increasing maize yield to some extent,among which the best yield increase was achieved by the 9th spreading leaf application.In summary,increasing planting density reduced the mechanical strength of maize basal internodes by elongating the internodes,increasing plant height,ear height and center of gravity height,and decreasing fresh dry weight per unit length,lignin and cellulose content,number and area of small and large vascular bundles,and cortex thickness.Eth DAH treatment enhanced the mechanical strength of maize basal internodes,increased structural and nonstructural carbohydrate content,improved microstructure,and enhanced the resistance of maize stalks to collapse,with 6 leaf extensions for chemical control mainly affecting internodes 2-4,9 leaf extensions for chemical control mainly regulating internodes 3-6,and 12 leaf extensions for chemical control mainly affecting internodes 3-6.The 6 leaf spread chemical control mainly affected the 2nd-4th internodes,the 9th leaf spread chemical control mainly regulated the 3rd-6th internodes,and the 12 leaf spread chemical control mainly acted on the 7th and higher internodes.In terms of yield increasing effect,the best effect was achieved at the 9th leaf.