Effects Of Different Exogenous Substances On Chemical Capping,Yield Formation And Quality Of Cotton

In order to explore the feasibility of spraying uniconazole compound exogenous substances instead of artificial topping and improve the yield and quality of cotton,the regulation effect of spraying uniconazole compound exogenous substances on chemical capping and growth and development of cotton was studied.The optimal combination of uniconazole compound was found,which was beneficial to promote the whole mechanization process of cotton and provide new ideas and theoretical basis for the development of high yield and high efficiency cultivation techniques of cotton in Xinjiang.A field experiment was conducted in Yougankumuqi Village,Shaya County,Aksu Prefecture,Xinjiang,with ‘ Xinluzhong 84 ’ as the material.A randomized block design was adopted.Two foliar sprayings were conducted before chemical capping(July 5)and during chemical topping(July 15).By measuring cotton plant type traits,cotton boll space layout,dry matter accumulation and distribution,chlorophyll relative content,photosynthetic characteristics,canopy structure,yield composition and fiber quality under different treatments,the effects of spraying uniconazole combined with different exogenous substances on cotton growth and yield and quality were explored.The main research results are as follows :1.Compared with W-CK,uniconazole chemical capping treatment had a certain effect on cotton plant type traits.There was no significant difference in plant height among the treatments,and the plant height of W2 treatment was the highest,which was 10.31 % higher than that of W-CK.The plant width of each treatment was lower than that of W-CK,and the plant width of W3 treatment was the smallest,which was reduced by 20.20 %.The stem diameter of each treatment was higher than that of W-CK,and the stem diameter of W1 treatment was the largest,increasing by 9.83 %.The number of fruit branches of each treatment was higher than that of W-CK,and the number of fruit branches of W2 treatment was the largest,which increased by26.07 % compared with W-CK.The number of bolls in each part of each treatment was different but not significant.The total dry matter accumulation and the proportion of buds and bolls increased.2.Compared with artificial topping control(W-CK),uniconazole chemical capping treatment had significant effect on canopy structure of cotton population.The leaf area index of cotton after each treatment showed differences in the flowering and boll stage,and the W2 treatment increased the most obviously.The values were 4.505 and 4.294 in July 25 and August 5,respectively,which were increased by 24.41 %and 20.96 % compared with the artificial topping control,respectively.After the first application,chemical capping treatment compared with manual topping treatment can significantly improve the canopy opening of cotton plants in each period,and W2 treatment compared with manual topping treatment can maximize the canopy opening of cotton,increased by 45.86 %,128.98 %,79.52 %,113.77 %,90.03 %,respectively,to achieve significant differences.At flowering and boll stage,the average leaf angle of W3 treatment was 3.48 % lower than that of W-CK,and there was no significant difference in other treatments.3.Compared with manual topping control(W-CK),uniconazole chemical topping treatment had a certain degree of improvement on the photosynthetic characteristics of cotton.There was no significant difference in the relative chlorophyll content of cotton after each treatment.Except for the D-CK treatment,other treatments increased.At the boll stage,the leaf photosynthetic characteristics of all treatments were improved,and the improvement of W2 treatment was the most obvious.Compared with W-CK and D-CK,the net photosynthetic rate(Pn)was increased by 87.54 % and 48.32 %,respectively;the transpiration rate(Tr)was increased by 90.12 % and 47.81 %,respectively;the stomatal conductance(Gs)was increased by 170.03 % and 94.99 %,respectively;and the intercellular CO2concentration(Ci)was increased by 27.77 % and 18.33 %,respectively.4.Compared with artificial topping control(W-CK),uniconazole chemical capping treatment had a significant effect on cotton yield.The number of bolls per plant,boll weight and lint percentage of cotton increased after single application and combination of different exogenous substances,so as to improve the seed cotton yield and lint yield.Among them,W2 treatment increased the most obviously,and its fiber quality was basically consistent with the artificial topping control.In summary,uniconazole combined with different exogenous substances could inhibit plant height,shape good plant type,optimize canopy distribution,improve photosynthesis,promote the transformation of nutrients to reproductive organs,and increase the proportion of buds and bolls.W1 and W2 treatments increased the number of bolls per plant and boll weight by increasing the accumulation of dry matter in the population and increasing the proportion of buds and bolls,and ultimately increased yield.It is feasible to use spraying uniconazole combined with exogenous substances for chemical capping of cotton.Based on the results of this experiment,W2 treatment not only achieved the effect of chemical topping,but also increased the cotton yield to the greatest extent,and the fiber quality had the smallest effect.It was recommended for production and use in Xinjiang cotton region.