Effects Of Different Chemical Regulation Methods On Growth Characteristics And Yield Formation Of Film-free Cotton

In order to shape plant type more perfectly,tap high-yield potential of non film cotton and realize high-quality and efficient production of non film cotton,field experiments were conducted with zhong619treated as test material with five control methods:TM（Early steady,middle and late control）,IM（Early promotion,mid-term control and late protection）,BM（Seedling control,bud stability,flowering and boll stage control）,PM（all the way to the end）,OM（Seedling promotion,bud stability,flower regulation and late preservation）and CK（no chemical regulation）.The effects of chemical regulation on the growth and development indexes,dry matter accumulation and photosynthetic physiological indexes,protective enzymes,boll setting characteristics and yield components of non film cotton under drip irrigation were observed,and the effects of chemical regulation on the growth characteristics and yield formation of non film cotton were discussed.The results are as follows:（1）Different chemical regulation methods had great effects on agronomic traits.PM had the most obvious effect on plant height and total fruit node length,while IM had the best agronomic shape,with the largest number of green leaves,stem diameter,main stem nodes,fruit sets and total fruit nodes.Om had better individual development,which was conducive to the formation of yield,although its agronomic traits were not outstanding;LAI of non film cotton population reached the maximum at flowering and boll stage,and the highest LAI of each treatment was 5.28（PM）,the lowest was 3.17（TM）,The LAI of IM and OM were 3.43 and 3.94,and the highest LAI of them were 3.55 and 3.75 at boll opening stage,which indicated that OM and IM could better regulate population growth and optimize population functional leaf area dynamics;Om had the highest dry matter accumulation in full boll stage,and the reproductive organ weight of OM was 57.41 g in full boll stage,followed by IM.（2）The root superficial area,root length density and root dry weight density of PM were the largest,while the root volume of CK was the largest in 0-20 cm soil layer,up to 2.74 cm³,TM was the largest in20-40 cm soil layer,up to 2.99 cm³,and IM was the largest in 40-60 cm soil layer,up to 2.86 cm³.（3）P_n,T_rand G_sof IM were higher,reaching 23.16μmol CO₂/（m²·s）,14.64 mmol H₂O/（m²·s）and0.88 mmol/（m²·s）,while C_iof CK was the highest,294.19μmol CO₂/（m²·s）.The photosynthetic"midday break"of P_ndiurnal variation was obvious,while the peak values of T_r,G_sand C_iwere 14;00,which ranged from 14.00 to 22.82μmol CO₂/（m²·s）,11.93 to 14.64 mmol H₂O/（m²·s）,0.65 to 0.91 mmol/（m²·s）,and 212.67 to 275.66μmol CO₂/（m²·s）,respectively;At the flowering and boll stage,the difference of population photosynthesis of all treatments reached a significant level,with OM reaching the highest of52.18 g/（m²·h）and CK only 15.04 g/（m²·h）.（4）In the middle stage（bud stage）,chemical regulation can significantly improve the SPAD value of functional leaves,and in the late stage（full boll stage）,chemical regulation can effectively reduce the SPAD value and slow down the speed.The individual growth and development of IM and OM are better,the plant type construction is reasonable,and the leaves in the late stage can maintain a good nutritional level,with the average SPAD value of 61.89 and 62.60 respectively.It is beneficial for the development of cotton bolls to maintain enough nutrition supply in the late stage.（5）The activities of superoxide dismutase（SOD）,peroxidase（POD）and catalase（CAT）were the highest in boll stage.OM treatment had the highest average SOD content（459.02 U/g FW）,followed by PM（440.61 U/g FW）,CAT（65.55 U/g FW/min）,OM（63.06 U/g FW/min）;POD increased sharply at first and then decreased gradually,and reached the peak at flowering and boll stage.At this time,the POD of PM was the highest,which was 366.63ΔOD₄₇₀/（min·g）.The average POD of each treatment was Im>BM>OM>TM>PM>CK;The average MDA of BM was 25.56 mg/g FW,IM was 25.71 mg/g FW,CK was35.01 mg/g FW.The activities of protective enzymes in leaves of non film cotton remained at a high level at boll opening stage,and IM was the best.At this time,CAT and PODin leaves were the highest,while MDA was the lowest,which were 19.36 U/g FW/min,250.99ΔOD₄₇₀/（min·g）,32.48 mg/g FW,respectively,while SOD in OM was the highest,which was 296.35 U/g FW.（6）The proportion of"Fu Tao"in IM and PM was the highest.The average abscission rate of each treatment shows that CK>BM>IM>OM>TM>PM,the highest abscission rate was 76.65%,the lowest68.31%;The spatial distribution of bolls in non film cotton was less affected by the regulation methods,but the regulation had significant interaction effects on the yield components and yield levels of cotton,Among them,IM was the most effective boll per plant,followed by PM and OM;BM was the highest boll weight,5.62 g,OM was the second,5.23 g.In terms of yield,the seed cotton yield of IM was the largest,which was5 419.09 kg/hm²,and the lint yield was 2 292.28 kg/hm²;OM was the second,which was 5 369.27 kg/hm²,and the lint yield was 2 319.52 kg/hm²;BM was 5 266.63 kg/hm²,and the lint yield was 2 290.98 kg/hm²;CK was the lowest,which was 3 485.21 kg/hm²,and the lint yield was 1 481.21 kg/hm².It can be seen that the control strategy of"pre promotion,middle control and post maintenance"is the best,followed by"seedling promotion,bud stability,flower regulation and post maintenance"and"seedling control,bud stability and flower bell control",which can be used as a technical reference for production practice.