Effects Of Sowing Date On Seed Yield And Quality Of Rapeseed(Brassica Napus L.)in Guanzhong Area

China is a big country that consumes edible oil.With the widespread planting and its own characteristics,Canola（Brassica napus L）has become the most competitive oil crop in China.Therefore,ensuring and improving its yield and quality is of strategic significance for the development of our society.With the improvement of technology,the impact of cultivation measures on the yield and quality of canola is increasing.The sowing date is one of the important measures to regulate the production of canola,and sowing on time is a necessary condition to ensure the normal growth and development of canola.In order to study the effects of different sowing dates on canola,this experiment was carried out at Doukou experimental station of Northwest A&F University in Shaanxi Province.Two varieties of Ganza1 hao and Qinyou 33 were selected as experimental materials,and three sowing dates were set to study the difference of sowing date on canola plant height,stem diameter,dry matter accumulation,chlorophyll content,photosynthetic characteristics,economic characteristics,and yield and quality at maturity.The main test results are as follows:（1）Different sowing dates will affect the growth and development of canola.In the two-year experiment,the plant height and stem diameter of the two varieties of canola increased first and then decreased with the delay of the sowing date.The change trend of the dry matter accumulation of winter canola stem,silique husk,grain and aboveground part during different sowing periods was consistent with that the change trends of plant height and stem diameter are basically similar,and different sowing dates have the most significant impact on the dry matter accumulation of winter canola stem.Among the root morphological indexes of canola,the total root length,root surface area,volume and dry weight decreased significantly with the delay of sowing date.（2）The treatments of different sowing dates had no significant effect on the SPAD value of winter canola at the flowering stage,but the photosynthetic characteristics of some functional leaves at the flowering stage were significantly different between different treatments.Among them,as for the transpiration rate and net photosynthetic rate of winter canola functional leaves,the general trend is normal sowing time>late sowing>early sowing.For winter canola functional leaves,the stomatal conductance and intercellular CO₂ concentration gradually follow the sowing date has decrease trend,but the difference is not significant.（3）The sowing date has no significant effect on the main inflorescence length and branch position of canola;the number of effective branches gradually decreases with the postponement of the sowing date,and the effective branch height increases first and then decreases.Different sowing dates have obvious effects on the number of siliques per selected area,branched siliques and the yield of canola.Based on the two-year data,it is found that the sowing date is between 10-15 in September when the yield reaches its maximum value.Sowing too early or too late will cause a decline in yield.There was no significant difference in yield between Ganza 1 hao and Qinyou 33.（4）The sowing date has a significant effect on the glucosinolate content of the variety Ganza 1 hao.With the delay of the sowing date,the glucosinolate content gradually decreases.At the same time,the glucosinolate content of Ganza 1 hao is significantly greater than that of Qinyou 33.The oil content of each variety was negatively correlated with the protein content.In addition,the sowing date had little effect on the fatty acid of canola.In conclusion,the suitable sowing date can improve the growth and development of rapeseed,increase the plant height and stem diameter,improve the root morphology,improve the transpiration rate and net photosynthetic rate of functional leaves of winter rapeseed,and also increase the yield and its components of winter rapeseed.In terms of quality,the content of glucosinolate of Ganza 1 hao cultivar was greatly affected by sowing date,and the delay of sowing date could reduce the content of glucosinolate.Therefor,in Guanzhong area of Shaanxi Province,in order to ensure stable yield of varieties,the sowing date can be adjusted to September 25 BBB 0 between September30.Meanwhile,the quality of Ganza 1 hao is greatly affected by temperature and its quality performance is not stable,while the yield and quality of Qinyou 33 are stable under various circumstances,so it can be vigorously popularized for planting.