关键词: 冬油菜, 直播, 育苗移栽, 播种期, 植株密度, 养分管理

Abstract: Both direct-sowing and transplanting are the dominated methods to establish winter oilseed rape in the current Yangtze River Basin, China, which play important roles in the development of national oilseed rape industry and edible oil supply security. With the altered cultivars, production targets, local labor conditions, and productivity levels, cultivation patterns and corresponding technical practices had transformed and developed at different historical stages. The present paper reviewed the development processes of cultivation pattern and corresponding technique in winter oilseed rape production since the foundation of China. Direct-sowing, the main cultivation pattern at the beginning and transplantation, was started from 1960s, and then transplantation was fully adopted in large scale during 1980s to 1990s. Nowadays, direct-sowing and transplantation cultivations have co-existed in winter oilseed rape production of China. Correspondingly, nutrient management practices have progressed from farmyard manure application to N and P chemical fertilizers application, and then converted to advocate the balanced application of N, P, K, and B fertilizers, and now a high-yielding and high efficiency technique system is found for transplanted oilseed rape. There are significant differences in the cultivation characters and growth progresses between direct-sowing oilseed rape (DOR) and transplanting oilseed rape (TOR), their growth stages, plant density, population structure and individual morphology were emphatically compared in this paper. The DOR showed generally shorter growth stages, weaker plants and lower individual yield, compared with TOR. However, DOR played group effects under the higher plant density and had stronger abilities to absorb nutrient and water due to the greater root system, and therefore showed a potential of high yield and high efficiency. At present, the abundance-deficiency nutrient indices and recommended fertilization system of TOR have been established in Yangtze River Basin, and nutrient management strategy has also been completed. The main points included determining fertilizer application rates based on soil fertility and target yield level, ensuring balanced nutrient supply and combined application of organic and inorganic fertilizers, adopting split application of N and K fertilizers (basal fertilizer﹕overwintering fertilizer﹕bolting fertilizer = 60%﹕20%﹕20%) to match the growth and nutrient uptake, aiming to strengthen individual plant and obtain high yield. In view of the rapid development but lagging nutrient management practice of DOR, the differences in nutrient responses, absorption and distribution, requirement and utilization between DOR and TOR were emphatically compared and discussed. The results indicated that DOR were more sensitive to nutrient deficiency and insufficient nutrient supply leaded to weak individual growth and population decline, its transport efficiencies for biomass and nutrient were lower, and it showed higher requirement for P and K than TOR. The nutrient management strategy of “promotion in early and stabilization in late” for DOR was presented according to the existing researches, and it included: ensuring P and K supply based on the rational and balanced nutrients application, applying organic fertilizer and returning straw to the field, and paying more attention to the role of N fertilizer in the development of individual and population. The N fertilizer as basal should be reduced and seedling topdressing need to be increased to improve plant growth at early stage, and appropriate topdressing before flowering are also required to ensure population density and yield formation. The recommended N fertilizer application practice of DOR is basal fertilizer﹕seedling fertilizer﹕overwintering fertilizer﹕bolting fertilizer = 40%﹕30%﹕15%﹕15%. Moreover, nutrient management should be adopted with other cultivation practices, e.g. selecting early-maturing and density-resisting varieties, adopting mechanization precision sowing technique, adopting specific long-acting formula fertilizer or controlled release fertilizer, increasing appropriately plant density to reduce fertilizer rate, compensate late-sowing, and improve sink and source, and enhancing plant protection to control diseases, pests and weeds. Furthermore, the main problems in current researches and the key points in future studies for DOR were also proposed in this paper, in hope of providing references for further improvement of cultivation practices and scientific fertilization technique.

Key words: winter oilseed rape (Brassica napus L.), direct-sowing, transplanting, sowing date, plant density, nutrient management