The reason of low yield in late direct-sowing rapeseed in the middle region of Jiangsu province.

The difference of yield components and the weight of dry matter at maturing stage among different sowing dates in direct-sowing rapeseed were studied.The main results were as follows:The yield of direct-sowing rapeseed decreased as the sowing date postponed.In the middle region of Jiangsu province,the optimum sowing date of direct-sowing rapeseed was in the range of September 21 to October 3 and the lastest sowing date was about October 24.The main reason of low yield in late direct-sowing rapeseed was the less pod number per plant.The main reason of less pod number per plant was the lower dry matter accumulation before flowering.