Growth and Yield Formation of Direct-Seeding Rapeseed Under No-Tillage Cultivation in Double Rice Cropping Area in Hubei Province

In the Yangtze River basin, winter fallow is popular for the double cropping rice (Oryza sativa L.). In this study, the possibility of adding a rapeseed cropping season after late rice harvest in this area was studied with the purpose of extending direct-seeding rapeseed under no-tillage cultivation pattern. In a 2-year field experiment from 2008 to 2010, the rapeseed cultivar Huashuang 5 (Brassica napus L. cv. Huashuang 5) were planted in 3 locations in Hubei Province of China after harvesting late rice. At both individual and population levels, the effects of plant density and nitrogen (N) application rate on rapeseed growth and yield formation were measured at seedling, budding, flowering, podding, and maturity stages. The cultivation pattern of no-tillage and direct-seeding after late rice harvest shortened the growth duration of rapeseed, especially at seedling stage, but prolonged the late budding stage in spring. The biomass accumulation from emergence to early budding was deficient severely, resulting in quick growth from budding to flowering of rapeseed. Application of N fertilizer had significant effects on enhancing the growth and yield formation of rapeseed through improving the individual and population qualities. Under the N rate of 270 kg ha⁻¹ condition, the highest yield of rapeseed was approximately 2250 kg ha⁻¹ at the density of 4.5 × 10⁵ plants or 6.0 × 10⁵ plants per hectare. The yield level was higher than that of average local rapeseed production. In the practice of no-tillage and direct seeding cultivation technique in the double rice cropping rice area, both nitrogen application rate and planting density should be considered simultaneously to obtain high quality of plant population and high yield of rapeseed.