Effects Of Planting Density And Spraying Time On Defoliation Ripening And Physiological Characteristics Of Cotton

Cotton is an important strategic material in China and the main economic crops in Xinjiang.Promoting rational close planting,chemical dedetopping,chemical defoliation and ripening technology is the only way to solve the problem of full mechanization for cotton production.Therefore,it is significance to carry out the research on chemical detopping cotton defoliation and ripening technology to promote the development of mechanical cotton picking technology in Xinjiang,reduce the cost of cotton planting and improve the benefit of cotton planting.A two-factor orthogonal experimental design was adopted In this study.The set density was:90000 plants·hm-2(M1),180000 plants·hm-2(M2),270000 plants·hm-2(M3);the flocculation rate was 10%(T1),30%(T2),50%(T3)during the spraying period of the set defoliation accelerator.The effects of planting density and defoliant spraying period on cotton defoliation and ripening effect,yield components,fiber quality,osmotic regulating substances and protective enzymes were studied.Study on the effects of planting density and application time on the physiological characteristics of cotton.The two aspects provide theoretical basis and practical experience for enriching cotton high-yield cultivation techniques and chemical control.The main findings are as follows:1.Effect of different densities and application periods on cotton defoliation and ripening effect,yield and qualityThrough the study of cotton defoliation ripening effect and yield quality,it was found that:from the perspective of the same density and different defoliation ripening agent spraying periods,the final defoliation rate of each density showed the rule of T2>T1=T3,and the hanging rate and flocculation rate showed T2>T3>T1.From the perspective of the same defoliation ripening agent spraying period and different densities,the final defoliation rate of each density showed M2>M3>M1,of which T2 is the highest defoliation rate was 99.2%in M2 treatment,while the rate of shoot-hanging showed T2>T3>T1 in T2 and T3 periods,and flocculation was more concentrated in M2 and M3 densities,among which the best flocculation rate was 96.9%in T2M3 treatment.Planting density and defoliant spraying time had no significant effect on cotton finger and lint percentage and planting density had significant effect on,boll weight and the number of bolls per plant.Under the same spraying time,the higher the planting density,the higher the cotton yield,among which T3M3 treatment had the highest yield,and the seed cotton yield reached 7225.5 kg·hm-2.The planting density of cotton and the spraying period of defoliation accelerator had no significant effect on the fiber quality of cotton.2.Effect of different densities and application periods on the content of osmotic regulators in cottonThrough the study of the content change process of osmotic regulators in cotton:it was found that the content of malondialdehyde(MDA)in cotton leaves of all densities increased continuously during the same defoliation accelerator spraying period,and the response was strong 2-6 d after application.The degree of lipid peroxidation in M1 density membrane was significantly higher than that in M2 and M3 densities,and the change of malondialdehyde(MDA)content was relatively flat after spraying defoliation accelerator at M3 density.As the maturity of cotton plants increased,the content of soluble protein(SP)in cotton leaves increased accordingly,and the change trend showed that it first increased and then decreased,and was most significant at M2 density.The content of free proline(Pro)showed an upward trend in each period,among which the increase was obvious in T1 and T2 periods,and the change process was more complex in T3 periods.As a whole,with the increase of natural flocculation rate,the higher density responded strongly to the stress after the application of defoliation accelerator,while the lower density responded relatively slowly.3.Effect of different densities and application periods on cotton protective enzyme activityIt was found that spraying defoliation accelerator could stimulate the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)and ascorbate peroxidase(APX)in cotton leaves with different planting densities.During the same application period of defoliation accelerator,the change trend of protective enzyme activity was basically the same in all treatments,and showed that in M2 and M3 densities,the response of protective enzyme activity to defoliation accelerator was significantly stronger than that of M1 densities.In terms of final defoliation and ripening effect,spraying defoliation accelerator at any planting density and application period can achieve the effect of destroying the physiological and biochemical balance of protective enzyme system of cotton,thus promoting the shedding of cotton leaves and boll flocculation,and accelerating the process of physiological aging of cotton.To sum up,T3M3 has the highest treatment output and reaches the mechanical production standard,which can be used as a reference index for field production.