Effect Of Sowing Date And Planting Density On The Development, Yield And Quality Of Direct Seeding Rapeseed

Rapeseed is the most important and advantaged oil crop of China, improving the yield and quality of rapeseed is very important for guaranteeing the oil supply of China. Direct sowing method has lots of advantages, such as low-cost, labor savings, high efficiency, and it is more suitable for large-scale mechanized production. So direct sowing has great development potential. There had been plenty of researches of appropriate sowing date and planting density of rapeseed at home and abroad, but the research of Chongqing in this area has not been reported at present.In this study, Mian Za95-97A×Za2013Hui and ZhongShuang No.220 were chosen as experiment materials, and the effects of sowing date and planting density on development stage, plant height, total leaf and green leaf number of main stem, dry matter accumulation, chlorophyll, photosynthetic characteristics, economic characters as well as grain yield and quality in mature period were investigated. Aiming to reveal the effect of sowing date and planting density on the growth, yield and quality of rapeseed, to explore a suitable sowing date and density ranges of direct sowing rapeseed in Chongqing, and to provide theoretical basis and scientific guidance for the development of local rapeseed lightened and simplified cultivation. The main results are summarized below1.Postponed sowing date increased the emergence time of rapeseed, shorten seedling and budding stages, the whole growth period of rapeseed was also reduced. Compered with sowing on October 14, the whole growth period of those two varieties rapeseed sowing on September 30 shorted about 14 days. The whole growth period has a tendency to shorten with the increase of density under early sowing date,but there had almost no impact on the growth period of rapeseed under late sowing date.2.Both delaying sowing date and improving planting density could lessen individual development of rapeseed. With delaying sowing date, the plant height, total leaf number and green leaf number of main stem, dry matter accumulation and root-shoot ratio showed a trend of decline.individual growth vigor was different between hybrid and conventional rapeseed, individual development caused by planting density was also different. With density increasing, plant height of MianZa95-97A×Za2013Hui reduced only in seeding stage, but plant height reduced by density increasing not only in seeding stage but also in budding and mature period for ZhongShuang No.220. The effect of planting density on main stem total leaf number and green leaf number is greater than the effect of sowing date. total leaf number and green leaf number of main stem decreased with the increase of density, and the earlier the sowing date been, the greater the differences between three planting density. Dry matter accumulation per plant and root-shoot ratio decreased with sowing date delaying and planting density increase,but the root-shoot ratio of ZhongShuang No.220 showed a trend of increased with the sowing date postponed.3.The effect of different sowing date on rapeseed leaf chlorophyll content was different for different varieties. Chlorophyll content decreased with sowing date delaying for MianZa95-97A×Za2013Hui in seedling stage and bud stage, while there was no significant differences between three sowing date. Chlorophyll content of ZhongShuang No.220 reduced after rising first in seedling stage and bud stage but increased in mature period with sowing date postponed. Increasing planting density, the leaf chlorophyll content of two varieties decreased, and the difference between three density treatments was greater in seedling and bud stage than which in flowering stage.4.Different sowing date and planting density had little influence on photosynthetic characteristics of rapeseed. Pn, Gs and Tr were not significantly different between different treatments. Ci of MianZa95-97A×Za2013Hui increased but Ci of ZhongShuang No.220 decreased with sowing date delaying.5.Different sowing date and planting density had no significant influence on rape stem diameter, numbers of effective branches, length of main inflorescence of rapeseed. Branch height increased along with the delaying of sowing date and the increasing of planting density. The effective pod numbers per plant, main sequence pod numbers, pod numbers per spike, seed numbers per pod, 1000-seed weight were no significant difference between different treatments for MianZa95-97A×Za2013Hui while significantly reduced for ZhongShuang No.220 with sowing date delaying.6.Sowing date and planting density had no significant effect on single plant yield but had significant influence on plot yield. Plot yield decreased with increment of density for MianZa95-97A×Za2013Hui, while decreased with the sowing date delaying for ZhongShuang No.220. Thus, the choosing cultural practices lie on what type of variety is. Early sowing date and low density is suitable for MianZa95-97A×Za2013hui, ZhongShuang No.220 also optimum an early sowing date,but a higher planting density. IF the sowing date was delaying, increasing planting density has a certain role to increase the final yield.7.The influence of sowing date and planting density on rapeseed quality was not significant. Rapeseed qualities was mainly affected by variety characteristics,while cultivation measures had little impact on it. But oil content of main sequence rapeseed were 1%~2% higher than branches. Increasing planting density could significantly improve main sequence’s share of total branch number of rapeseed groups and then could also improve the groups oil content.