Chemical defoliation can have most of the leaves abscised quickly before harvesting time, thereby improving operation efficiency of mechanical harvest and decreasing percentage of trash content in raw cotton. Because of the direct and indirect effect of defoliation benefiting the plant population, it facilitates the cotton boll crack, chemical ripener can solve the problems of the maturation of cotton during the changeable harvest phase. With the technology of maturation and defoliation in cotton, people make it possible to pick up cotton through machine. It is important for the farmers of Xinjiang to save cost, increase benefit and improve competition on international market. In this study, the defoliants using in cotton at both home and abroad were investigated, then the best product was screened out by experiment, based on the shed leaves percentage, boll opening rate, yield in cotton and so on.Finally, summarizing all above theses, the authors come to the conclusion. We study about the promoter of defoliation including species, compound proportion, compound method by experiment. The study was carried out according to the climate characters and agronomic production level of the Xinjiang reclamation area at present. The experiment was arranged about the distance between rows and plants, variety screening and defoliant screening in Xinjiang. According to the plot experiment, the big area demonstration, outside investigation and inside seed research, applying statistic methods, the results were as follows:The most economical, practical and good synthetic performance defoliant dosage was 600g/hm~2 50% thidiazuron WP marked defoliant +1050g/hm~2 ethrel. The optimum temperature of spraying the mixture defoliants was the 18-25℃at the daily average temperature, the best spraying time is on September 10-15th in Cotton Fields in South Xinjiang. The most economical, practical and good synthetic performance defoliant dosage was 675g/hm~2 Zhengongfu marked defoliant +organic Silicon promoter225ml/hm~2 +2250g/hm~2 ethrel, 675g/hm~2 "Falling Leaves Settling on the Roots" marked defoliant +888A promoter225ml/hm~2 +2250g/hm~2 ethrel, 600g/hm~2 Zhengongfu marked defoliant +888A promoter225ml/hm~2 +2250g/hm~2 ethrel. The optimum temperature of spraying the mixture defoliants was the 18-25℃at the daily average temperature, the best spraying time is on September 10-15th in Cotton Fields in north Xinjiang.There is no correlation between the impact of defoliant and temperature those 5 days after spraying and 10 days before spraying, but the impact of defoliant are related with temperature during 6-10 days after spraying. Meanwhile, it is closely related with temperature change tendency. After spraying chemical for some time, the temperature was steadily increasing. The result is that the shed leaves percentage became relatively high. The shed leaves percentage became very low with the decrease of temperature. We consider that, it is important that Leaves how to uptake agent at different air temperature on same day. Lower temperature is beneficial for cotton to uptake into agent adequately because of slow evaporation of agent. It can work effectively 6-7 days latter. If the air temperature is high, control effect is good.With the help of research result in recently years, the most economical, practical and good synthetic performance defoliant dosage was determined by the time of chemicals application to decide application rate. If you need spray agent in the plant in advance, you must spray a little. The later is multiple than before. We determine the time and rate of chemicals application by weather forecast. When the temperature is increasing, we spray agent for the plants. Otherwise, we need more agents in the plant. If yield in cotton is lower, we only spray once. If yield in cotton is higher, it can be advanced for 7 days. After most of the leaves have exfoliated, we will spray another.The rate of shed leaves and boll open were influenced by temperature and sunlight hours. Meanwhile, it is closely related with cotton variety. The rate of shed leaves coloredcotton lines are lower than cotton Xinluzao No. 13 in the same dosage. So, machine instruction statement picked cotton variety was screened out. Moreover, there are the other factors including quality of spraying, Relative humidity, nitrogen nutrition, the diseases and insect pests, cotton growth and development and so on."The main points of Integration and Practical Technology of machine-harvested cotton Cultivation, defoliation and ripening ect." was written in order to guarantee the smooth implementation of picking cotton with machine; perfect cultivation management, defoliation and ripening points gradually; construct matching equipment of processing; ensure that the technology of picking cotton with machine will be extended with high quality, high efficiency, security and high speed. |