Effect Of Sowing Date On Seedling Growth And Boll Development Of Plant Top Of Cotton Under Mulched Drip Irrigation In Xinjiang

【Objectives】The climate of Xinjiang is typical continental arid climate with abundant resources of light and heat.The agricultural production in Xinjiang is irrigation agriculture.Therefore,Xinjiang has the advantages of resource to develop cotton industry.However,the temperature of Xinjiang changes greatly in spring,cotton seedlings are prone to frost,continuous low temperature and other extreme weather,resulting in rotten buds,rotten seeds,poor growth of seedlings;With the application of cotton planting technology under mulch drip irrigation,under mulch drip irrigationWater can the water demand seedling germination and emergence of cotton,reduce the contradiction between sowing date and soil moisture,and the temperature of sowing date becomes the main influencing factor.In order to meet the temperature demand of cotton seedling under drip irrigation under mulch and to cultivate strong seedling,this paper adopts the method of sowing by stages to form sowing under different temperature conditions.The effects of different temperature conditions on the growth of cotton seedlings and the development of boll at the top of drip irrigation under mulching were studied,and the temperature requirements of boll spitting at the top of cotton under drip irrigation under mulching were discussed.The results provide theoretical basis for cotton harvesting and sowing and field management in northern Xinjiang.【Methods】According to the temperature requirement of sowing and the termperature changes of 3 days before sowing,there were 3-4 sowing date conducted in this study.The emergence rate,seedling morphogenesis,dry matter accumulation of plant,root morphology,changes of bolling period,cotton fiber quality and yield components factors were determined to study the relationships between cotton seedling growth and boll development in the later growth stage of cotton under different sowing date treatments.【Results】The results of this study showed that（1）the emergence rate of the cotton sown under 18.7℃soil temperature condition on April 21,2017 was the highest among the treatments.In the cotton sown under 24.7℃soil temperature condition on April 29,2017,the plant height than other treatments10-12.22%,height of cotyledon node was 8.82-20.59%,total root length1.79-6.59%,and root dry matter accumulation 14.84-25.93%respectively;the root dry matter accumulation and root-shoot ratio of cotton sown under 9.5℃soil temperature condition on April 8,2017 were the highest among the treatments;（2）the root dry matter accumulation of cotton sown under 9.5℃soil temperature condition was the highest among the treatments;the root surface area,root diameter,root volume was 1.60-4.65%,3.28-11.47%,and 15.15-21.12%higher than other treatments,respectively;（3）in the cotton sown on April 8,2016 and 2017,the single boll weight,fiber length,fiber specific intensity,fiber uniformity,micronaire value of cotton fiber was 0.79-11.02%,1.05-3.86%,2.00-9.49%,0.59%-2.03%,0.41%-13.76%higher than other treatments,respectively;the seed cotton yiled of cotton sown under 9.5℃soil temperature condition on April 8,2017 was 6.81-32.78%higher than other treatments;in the cotton sown under 24.7℃soil temperature condition on April 29,2017,the boll number per plant,single boll weight,and the number of harvested plants decreased,and then the yield of it was the lowest among the treatments.【Conclusion】Overall,when the air temperature was at 13.8-15.7℃,the soil temperature was at 17.6-18.7 ^oC and the 1 week mean air temperature was at 16-18℃,the emergence rate of cotton would be higher than 90%.According to the recent decade,the days when the air temperature was at 13.80-15.70℃were from April 7^th to April 15^th.In the cotton sown under under 9.5℃soil temperature condition,the height of cotyledon node was more appropriate,the dry matter accumulation was greater,the root-shoot ratio was higher,resulting in a stronger seedling,though the emergence rate was not very high.The higher effective accumulative temperature contributed to greater total boll numbers and single boll weight,and therefore a higher yiled in cotton.