Effects Of Seeding Date And Seeding Rate On Agronomic Traits,Yield And Quality Of Shaanyou 28

Oilseed rape is one of important oil-bearing crops in China.Improving its yield and quality is very significant to safeguarding China’s grain and oil food safety.Nowadays,a lot of rural labors immigrate to urban areas.Thus,rural areas are now faced with severe labor drain.As a result,China’s oilseed rape production is now developing towards low-cost & high-efficiency,economies of scale and mechanization.However,oilseed rape mechanized production is faced with two bottlenecks: one is a lack of varieties that are suitable for mechanized production,and the other one is a mismatch between agronomic traits of oilseed rapes and agricultural machinery.In particular,researches related to cultivation techniques for varieties that are suitable for mechanized production are very few.Therefore,this paper was focused on a comparative analysis of Shaanyou 28,which was the first oilseed rape variety dedicated to mechanized production approved by Shaanxi Province,and the other six oilseed rape varieties that are approved and promoted in the recent years.Through the comparative analysis,growth and development characteristics of Shaanyou 28 were summarized,and effects of different seeding dates and seeding rates on agronomic traits,yield and quality of Shaanyou 28 were studied.Then,the optimal seeding dates and seeding rates for Shaanyou 28 in production were initially proposed to provide some technical support for large-area demonstration and promotion of Shaanyou 28.The research results suggested that:1.In terms of Shaanyou 28,its flowering phase is concentrated;growth period is short;shoot-root ratio is high;plant height is low;main inflorescence has the greatest podding density;and economic coefficient is high.Compared to the other six varieties,the flowering phase of Shaanyou 28 is 21 days,while the flowering phase of the other six varieties ranges from 21 to 24 days.The growth period of all seven varieties ranges from 249 to 252 days,and Shaanyou 28 has the shortest growth period of 249 days.During the maturation stage,the plant height of all varieties ranges from 123.0 to 165.8 cm,and “Shaanxi Oilseed Rape 28” has the lowest plant height of 123.0 cm.The podding density of main inflorescence of all varieties ranges from 0.91 to 1.47 per centimeter,and “Shaanxi Oilseed Rape 28” has the greatest podding density of main inflorescence.The economic coefficient of all varieties ranges from 0.30 to 0.37,and Shaanyou 28 has the highest economic coefficient of 0.37.2.With increase of seeding rate,the plant height,rhizome diameter and dry weight of Shaanyou 28 during the maturation stage increase first,and then decrease,showing a inversed V trend.In favorable seeding conditions(September 21 st,2015),differences among different seeding rates are significant;and in late-seeding conditions(September 28 th,2015 and October 4th,2015),differences in agronomic traits among different seeding rates are not significant.Agronomic traits for early-seeding date and moderate seeding rate are better than agronomic traits for late-seeding date and higher seeding rate.The increase of seeding rate and delay of seeding date can increase the height of branches of Shaanyou 28,but decrease the length of main inflorescence and reduce the number of first effective branches,the number of siliques of main inflorescence,the number of siliques of first branches and the number of effective siliques of single plant.Therefore,in favorable seeding conditions,seeding rate has significant effects on agronomic traits of Shaanyou 28.3.In the condition of same seeding date,with increase of seeding rate,the oil content of Shaanyou 28 increases,but its protein content decreases.In favorable seeding conditions(September 21 st,2015),the oil content of Shaanyou 28 with a seeding rate of 7.78 kg/hm2 is 2.22% higher than the oil content of Shaanyou 28 with a seeding rate of 3.33 kg/hm2;while the protein content of Shaanyou 28 with a seeding rate of 7.78 kg/hm2 is 2.21% lower than the protein content of Shaanyou 28 with a seeding rate of 3.33 kg/hm2.In the condition of same seeding rate,with delay of seeding date,the oil content of Shaanyou 28 decreases,but its protein content increases.When the seeding rate is 5.56 kg/hm2,the oil content of Shaanyou 28 with the first seeding date(September 21 st,2015)is 1.06% higher than the oil content of Shaanyou 28 with the second seeding date(September 28 th,2015)and 2.00% higher than the oil content of Shaanyou 28 with the third seeding date(October 4th,2015).When the seeding rate is 7.78kg/hm2,the oil content of Shaanyou 28 with the first seeding date(September 21 st,2015)is 1.79% higher than the oil content of Shaanyou 28 with the second seeding date(September 28 th,2015)and 2.96% higher than the oil content of Shaanyou 28 with the third seeding date(October 4th,2015)4.In Guanzhong Plain,the seeding dates suitable for Shaanyou 28 range from September 21 st to September 28 th.When seeding rate ranges from 5.56 to 6.67 kg/hm2,yield above 4,000 kg/ hm2 can be harvested.Therefore,on suitable seeding dates,a reasonably decreased seeding rate is recommended for an early-seeding date,while a reasonably increased seeding rate is recommended for a late-seeding date.