Study On Screening And Effect Of Chemical Topping Compound In Cotton

[Objective]It is an important measure to realize"the last kilometer"of mechanization cultivation of cotton by spraying cotton leaves with stable and effective chemical topping agent to inhibit the growth of cotton top,so as to replace artificial or mechanical topping.Through this study to explore the drip irrigation cotton plant morphology and distribution of dry matter accumulation of northern Xinjiang,endogenous hormones and yield and its components under different complex matches chemical fertilization response effect,combined with the economic benefit is selected to optimize chemical formula and its usage,for the application of cotton chemical multi-topping technology promotion and provide basis for cotton light simplified cultivation.[Methods]Dosage form optimization trials will be carried out in 2019-2020.Using abscisic acid（ABA）,unbuzol（S3307）,anthocyanin（MH）,ethephon（ETH）and other regulators as the main base materials,the experimental dosage forms were formed according to different components to regulate the growth of cotton tip,and were sprayed at bud and boll stages.The"chemical topping agent"and"Cu Huawang promotion"series of dosage forms（Cu Huawang molding agent and topping agent）with a large application area at that time were used as the first control（CK1）,and equal amount of water was sprayed at bud stage and artificial topping was used as the second control（CK2）.The tested variety was Lu Mianyan no.24.The differences in plant type structure,yield and economic benefit of cotton treated with different compound chemical agents were compared.Clear SPAD,LAI,accumulation of dry matter distribution and change rule of endogenous hormones such as index,select the optimal dosage forms,on this basis,carried out in 2021 under the optimum dosage forms with different spraying times,dose of two-factor randomized block experiment,and to determine optimum formulations and optimized fertilization scheme,for chemical multi-topping in cotton production technology provides the basis for scientific applications.[Results]（1）Screening of optimal dosage forms.Compared with artificial multi-topping（CK2）,"Cu Huawang"series of dosage form（CK1）processing of cotton stalk width,average main stem internode length,angle index,the upper branch were lower trend,length and Angle of effective branch number,boll number per increased,yield improvement,show that"Cu Huawang"series of dosage form application,can achieve the anticipated effect of agricultural production,It is suitable to be used as dosage form screening control.Compared with CK1,A2B3（S3307+ABA at bud and boll stages）and A3B5（S3307+ETH at bud and boll stages）showed no significant differences in plant height,internode length of main stem,number of fruit branches,plant width and Angle index.Under A3B5 treatment,the boll setting rate of upper fruit and boll opening rate of middle and lower fruit nodes increased by 3.7%and 2.8%,respectively.Under A2B3and A3B5 treatment,the boll number per plant increased by 0.8 and 0.7,and the yield increased by 9.4%and 8.0%,respectively.The economic benefit of A3B5 treatment was the highest,and there was no significant difference with A2B3 treatment.Under A3B5 treatment,SPAD and LAI reached the highest at the bolling stage,the maximum growth rate（V_m）of vegetative organs and reproductive organs increased by6.3%and 18.4%,respectively,and the proportion of reproductive organs reached 57%at the bolling stage.The IAA and ABA content were effectively reduced and increased 10 days after spraying.The ABA/IAA and CTK/IAA levels in boll phase remained high 10 days after spraying.（2）Study on the effect of optimum chemical formulations on cotton growth and development.Cotton plant height,internode length of main stem,number of fruit branches,plant width and Angle index all showed a decreasing trend with the increase of spraying times and concentration.Under T2C3 treatment,SPAD and LAI reached the maximum at the early bolling stage,and dry matter weight of reproductive organs maintained a high level from the early bolling stage.Boll number per plant under T1 and T2treatments was proportional to the spraying concentration,and T2C3 was 2.17%-9.19%higher than other treatments.The single boll weight was proportional to the spraying concentration under different spraying times,and reached the maximum at T3C3.The seed cotton yield was the highest in T2C3 and increased3.08%-16.69%compared with other treatments.[Conclusion]Compared with artificial topping,different chemical topping agent treatments can shape compact plant type individuals in different degrees and weaken the growth of cotton plant top.A3B5treatment can significantly increase boll setting in the upper part and increase the probability of boll opening in the middle and lower part,and promote boll centralized boll opening.The SPAD value of cotton was increased and photosynthesis was enhanced.Adjust the balance between reproductive growth and vegetative growth of cotton,improve the proportion of dry matter distribution of reproductive organs;Decreased IAA and GA₃contents in functional leaves of main stem,weakened vegetative growth,and facilitated the transport of photosynthates to reproductive organs,thus promoting cotton yield.Both A2B3and A3B5 treatments have a certain potential to increase production,but considering economic benefits,A3B5 is more dominant.A3B5 chemical topping agent could control the plant height,increase the number of fruit branches,shorten the internode length of main stem,and weaken the longitudinal growth advantage of cotton under the treatment of T2（twice in bud and boll stages）and C3(45g·hm^-2in A3 reagent in bud stage and180g·hm^-2in B5 reagent in boll stage).Therefore,the nutrients produced at the top of cotton were more heavily transported to the side branches.At the same time,the SPAD value of cotton leaves was increased to ensure the sustainable and efficient photosynthesis of cotton plants,expand the transfer of photosynthetic products to reproductive organs,promote the boll formation in the upper part of cotton plants,and increase the boll number per plant,which was conducive to the increase of cotton yield and income.