Effects of Increasing Boll Fertilizer on Photosynthetic Characteristics,Autumn Boll Development and Yield of Chemically Capped Cotton
Chemical topping accelerates the aging process of cotton,leading to insufficient nutrient supply,affecting the proper development of top cotton bolls,resulting in reduced boll formation,fewer bolls,and lower boll weight,ultimately impacting yield.To address this issue,using J206-5 as the experimental material,a split-plot design was employed with the main plot containing two additional urea treatments during the boll stage[0 kg/ha(N0)and 150 kg/ha(N1)],and the sub-plot containing four foliar fertilization treatments during the boll stage[no foliar spray(F0)and spraying 1%potassium sulfate(F1),0.1%borate(F2),0.3%monopotassium phosphate(F3)],totaling eight treatments.The study aimed to investigate the impact of additional boll fertilizer under chemical topping conditions on cotton photosynthetic capacity,boll development,and yield formation.Results indicated that the functional leaf SPAD value peaked at 21 days after boll fertilizer application,with N1F3 treatment showing the highest SPAD value among all treatments,increasing by 15.02%compared to N0F0.After 21 days of applying boll fertilizer,at N0 level,Pn values of F3,F1,and F2 treatments increased significantly by 20.72%,17.71%,and 14.42%,respectively,compared to F0 treatment;at N1 level,F3 and F1 treatments showed significant increases of 20.00%and 11.81%,respectively,over F0 treatment.Boll length and volume after applying boll fertilizer were higher than N0F0 treatment,and the differences were significant in boll length except for N0F2 treatment.Under the same nitrogen level,seed and fiber dry mass of F1—F3 treatments were higher than F0 treatment;at N0 level,seed and fiber dry mass of F1 and F3 treatments increased significantly by 31.43%,25.53%,and 38.57%,35.46%,respectively;at N1 level,seed dry mass increased significantly by 32.92%,17.39%,37.89%for F1—F3 treatments,while fiber dry mass increased by 23.81%and 32.65%for F1 and F3 treatments,respectively,compared to F0 treatment.Individual boll weight and seed cotton yield of all boll fertilizer treatments were higher than N0F0 treatment,with N1F3 treatment showing the highest individual boll weight(6.18 g),a significant increase of 14.44%over N0F0 treatment;except N0F2,N1F0,and N1F2 treatments,seed cotton yield of all other treatments was significantly higher than N0F0 treatment,with N1F3 treatment showing the highest seed cotton yield of 7 273.35 kg/ha,and a significant increase of 30.20%over N0F0 treatment.In conclusion,based on cotton chemical topping and nitrogen application at the conventional levels of 300-375 kg/ha in southern Xinjiang,it is recommended to apply 150 kg/ha of urea along with foliar spraying of 0.3%monopotassium phosphate during the boll stage to enhance cotton's photosynthetic capacity,facilitate the accumulation of boll biomass,increase the number and quality of cotton bolls,thereby enhancing cotton yield.
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