Effects Of Chemical Regulation On The Plant Morphology And Yield Formation Of Cotton After Drought

In chemical control,the spraying of mepiquat chloride on cotton not only helps to shape an ideal plant type,but also replace artificial topping.The application of DPC depends on climate and cotton growth.In irrigated agricultural production,long irrigation cycle often leads to early drought in cotton.Therefore,it is necessary to adjust chemical control strategy of cotton to ensure the stability of cotton production in arid areas.This experiment simulates the cotton drought background during the bud stage,adopts a two-factor random block design.The spraying time of DPC is 3rd,6th and 9th days after drought,with no DPC as the control treatment and the topping method is chemical capping(T1)and manual topping(T2),to study their impact on cotton plant morphology and yield formation after drought.The main results are as follows:(1)Effect of chemical regulation on agronomic traits after drought in cottonAfter drought stress at the bud stage,the height of the cotton plant is controlled at 75～80cm.By delaying the spraying of low-dose mepiquat chloride,the overall cotton plant type tends to be compact.The growth of cotton plant height,main stem internode length,plant width cross-sectional area,fruit branch length,fruit branch angle,and the area of top fourth leaf are affected significantly inhibited,and the decreasing range was 8.4%～16.5%,12.1%～16.7%,13.2%～32.9%,6.7%～38.7%,4.3%～16.1% and 7.9%～26.0%,respectively,which are more effective with the DPC applied earlier.Compared with manual topping,the area of top fourth leaf of chemical capping cotton increased by 19.5%,the cross-sectional area of plant width decreased by 6.1%,and the increase in plant height,main stem leaf number,main stem internode length,and fruit branch length was not significant.Under chemical capping,spraying DPC delayed six days under moderate processing cotton plant height,plant type structure is more reasonable.(2)Effects of chemical regulation on cotton canopy structure after droughtBefore topping(0～74 days after emergence),Various LAI decreased with DPC sprayed time in advance in cotton,and the upper LAI decreased most obviously.The D3 and D9 treatments were at the peak of LAI decrease by 20.6% and 19.4%,respectively,the mean foliage inclination angle(MIFA)of each part showed an upward trend,with the highest value in D3,the MIFA at the lower,middle and upper parts increased by 6.0%,18.3% and 19.2% respectively compared with CK,the scattered radiation transmission coefficient(TC)of each part of cotton was significantly higher than CK,the decrease in specific leaf weight(SLW)of middle and upper parts was reduced.After topping,the upper LAI of DPC treated cotton continued to decrease,while LAI and SLW at the middle and lower,TC at each part remained at a relatively high level.Throughout the reproductive period,the relative chlorophyll content(SPAD)after DPC spraying increased,especially D3 has 6.8% higher than CK.Compared with manual topping,cotton’s upper LAI,middle SLW and TC increased significantly under chemical capping,and MFIA of each part increased,overall canopy index showed an increasing trend.Chemical capping and low-level DPC spraying for 6 days delayed,SPAD and SLW are higher,LAI is evenly distributed,leaves are kept upright,and the overall canopy is well ventilated in cotton.(3)Effect of chemical regulation on yield formation in cotton after drought.Before topping(0～74 days after emergence),after spraying DPC,the dry matter accumulation of cotton bolls increased,and the dry matter accumulation of stems and leaves decreased.The maximum increase and decrease were 47.8%,23.8% and 14.2%,respectively.After spraying DPC,the cotton fruit node number,bud number,prehot seasonal boll and autumn bolls ratio increased by 9.0%～15.5%,21.4%～37.9%,22.6%～53.7%,135.3%～188.2%,and the proportion of summer bolls and the weight of fallen buds decreased by 23.6%～56.8% and 7.6%～66.4%,respectively.After topping,the dry matter accumulation of DPC treatment increased by 6.0%～22.9%,and the dry matter accumulation of stem and leaf decreased slowly.Among them,the dry matter accumulation of boll,stem,leaf of D6 treatment was higher than CK.The increase was19.7%～69.8%,5.4%～15.4% and 13.3%～19.9%.The number of bolls of cotton increased rapidly within 80～90d after emergence,while the number of bolls dropped significantly increased.Finally,the number of bolls per plant increased by 9.3%～16.3%,and the weight of single boll increased by3.7%～4.6% after spraying DPC,thereby increasing the yield of cotton seed cotton by11.0%～22.9%;The overall output of lint cotton is D6>D9>D3>CK.Compared with manual topping,the number of fruit nodes,bolls,shedding buds,and shedding bolls increased by an average of 13.7%,4.5%,17.1% and 20.7% after chemical capping in cotton,and the proportion of prehot seasonal boll by an average of 9.6%.The proportion of summer bolls and autumn bolls increased by 15.4% and 37.5% on average,while the dry matter accumulation and the number of bolls did not change significantly in cotton,and finally the yield of seed cotton and lint cotton increased by 4%.