Effects Of Chemical Topping On Growth And Physiological Characteristics Of Cotton In Mulchless Planting Mode

Cotton topping is a technique in which the apex of cotton is artificially removed to promote the transfer of nutrients to the reproductive organs.In order to liberate labor and reduce production costs,in recent years,chemical topping technology,which delays and inhibits the top growth advantage of cotton plant through plant growth regulators,has gradually replaced manual topping.In this study,cotton was sprayed with different chemical topping reagents at different times under the mulchless planting mode of Xinluzhong 82.To investigate the effects of chemical topping on agronomic traits,dry matter,total nitrogen content in each organ of cotton plant,enzyme activity in leaf,yield composition and quality.The main conclusions are as follows:1.Chemical topping inhibited the increase of plant height and fruit branch number,and promoted the increase of stem diameter.When spraying the same chemical topping agent,the plant height,fruit branch number,bud number and boll number of cotton with different chemical topping time were R(artificial topping)<T1(July 9)< T2(July 16)< T3(July 23)< B(no topping),and stem diameter decreased with the extension of topping time.Spraying different topping agents at the same time,the chemical topping agent with fluorideamine as the main component had the best control effect on cotton plant type.The initial node and the height of the initial node of fruit branch were less affected by chemical topping agent.2,chemical multi-topping have significant effects on the accumulation of dry matter,the artificial multi-topping and multi-topping all have significant difference,not in multi-topping back with time,the cotton dry matter accumulation and distribution of different organs from vegetative growth to reproductive growth earlier,T3 time starts from multi-topping after 10 d dry matter distribution coefficient of significant change,It is about 10 days earlier than T1 time(20th day).Spraying different topping agents at the same time,chemical topping agent with fluorideamine as the main component was more beneficial to dry matter accumulation and distribution of cotton plants.3.After chemical topping,the total nitrogen content in all organs of cotton plants showed a downward trend,and the change rate of total nitrogen content in leaves and reproductive organs decreased with the extension of topping time.4.Spraying chemical apex agent increased the content of Peroxidase(POD)and Superoxide Dismutase(SOD)in cotton leaves,decreased the content of Malondialdehyde(MDA),and maintained normal physiological metabolism.Enhanced cotton resistance to adversity.The effect of chemical topping time on enzymatic activity of cotton leaves decreased.Spraying different topping agents at the same time,the chemical topping agent with fluorideamine as the main component had better effect.5.With the delay of chemical topping time,the cotton yield increased,and the average cotton yield of T3 treatment was 5419.5 kg/hm~2,which was 6.97% lower than the artificial topping yield of 5625.85kg/hm~2.However,with the postponement of topping time,the quality of cotton decreased,and with the postponement of topping time,the number of cotton green boll increased obviously.Influence cotton final yield.