Effects of Seedling Ages on Growth,Development and Yield of Transplanted Short-season Cotton in Wheat-cotton Continuous Cropping Pattern

Under the new wheat-cotton continuous cropping pattern,cotton substrate seedling and naked-root transplant is a main light and simple technique.Its primary target is to figure out the appropriate seedling age to transplant.This study was conducted to investigate the differences in growth,development and yield among six transplanting seedling ages for a short season cotton(Gossypium hirsutum L.),cv.CCRI 50,in Anyang,Yellow River Valley Planting Region.The main results were as follows: the accumulated air temperature from transplant to bud declined by 4.33℃·d with each day increase in seedling age,but accumulated temperature use efficiency reduced by increasing seedling age.Suitable transplanting seedling age resulted in a higher percentage of pre-frost cotton,about 75%.Seedling age of 50 d resulted in the greatest seed cotton yield which was 3238.6 kg·hm-2.Moreover,high seedling quality had a positive effect on transplant survival rate.With the characteristics of concentrated growth,for cotton seedlings transplanted after wheat,the fastest growing rate,the greatest dry matter and reproductive organs accumulation rates occurred around 34 days after being transplanted,14 days after topping and 70 days after squaring,respectively.Enzymatic activity of functional leaves changed a lot during the recovering stage,moreover,enzymatic activity of 50-day seedlings kept relatively stable.By comprehensive comparison,50-day seedlings had more appropriate yield components and higher potential for yield increase.