[Objective] The aim of this work was to analyze the N fertilization on the vegetative growth and N uptake of different winter rapeseed varieties at wintering stage. [Method] In two consecutive years (2009-2011), two winter rapeseed varieties (B. napus L.), an early maturity variety Zhongyou 116 (ZY116) and a middle-late application maturity variety Zhongyouza 12 (ZYZ12) were employed. Field experiments with different N levels (0, 90, 180, 270, 360 kg N/hm 2 ) were designed. At the wintering stage, the dry matter weight, the nitrogen content and concentration of plants, leaf nitrate reductase activity (NRA) and seed yields were investigated. [Result] The shoot dry matter of ZY116 increased rapidly when N rate ranged from 0 to 180 kg/hm 2 , and it raised slightly when N rate ranged from 180 to 360 kg/hm 2 . The shoot dry matter of ZYZ12 were changed in a single peak curve; the peak of shoot dry matter appeared at 270 kg N/hm 2 . The N concentration and N content in shoot and root increased rapidly when the N rate changed from 90 to 180 kg/hm 2 . Moreover, the N concentration and N content root of in ZYZ12 were much higher than that of ZY116. Present study revealed that the changed trend of leaf nitrate reductase activities (NRA) were significantly increased at the N rate of 180 kg/hm 2 in ZY116 and ZYZ12 compared with the N rate of 90 kg/hm 2 in two years. [Conclusion] Optimal nitrogen application significantly increased the dry weights and N uptake at wintering stage as well as increasing the yield of winter oilseed rape.
China is one of the most important rapeseed producing countries in the world. Effective mechanical harvesting time for decreasing harvesting loss of winter oilseed rape has been becoming a critical factor. An elite cultivar Zhongshuang 11 (Brassica napus L.) was employed in two rounds of field experiments from 2009 to 2011. Seeds were sown with machine, three combine harvesting times namely combine harvesting A, B, and C (CHA, CHB, and CHC) were designed and manual harvesting (MH) as control was performed at maturity. The harvesting treatments were determined according to color of pod and seed in the field. Seed yield loss and quality in different treatments were evaluated. Results showed that both seed yields and harvesting losses in 2009-2010 were higher than that in 2010-2011, whereas seed oil contents in 2010-2011 were higher than that in 2009-2010. The highest yield appeared in CHB, which was significantly higher than that in MH. Furthermore, harvesting loss in CHB were 50% that in MH. Seed oil content and chlorophyll exhibited no obvious difference between CHB and MH. Economic profit analysis demonstrated that mechanical sowing/combine harvesting (MS/CH) showed an input/output ratio of 1:1.6, and it was 1:1.2 in mechanical sowing/manual harvesting (MS/MH). Labor-cost accounted for more than 70% of the total cost in MS/MH, which led to low profitability to a great extent. Our results suggested that CHB was the optimum harvesting time for winter oilseed rape along the Yangtze River.
MA NiZHANG Chun-leiLI JunZHANG Ming-haiCHENG Yu-guiLI Guang-mingZHANG Shu-jie