Abstract: The rapeseed undersowing rice cultivation model is effective for double cropping rice in winter fallow field in southern area of China. The symbiosis time of rice and rapeseed as well as seeding amount are key factors to affect the yield of rapeseed undersowing rice. To explore the growth and yield affected by different symbiosis times and various seeding amounts, we designed a split-plot experiment with two factors. The results showed that: (1) the rapeseed density decreased with the delay of growth period, and the rapeseed undersowing rice was favorable for improving the density at the seedling stage, but the density at the other growth stages decreased with extension of symbiosis; (2) symbiosis time and seeding amount had a significant effect on rapeseed density at each growth period, moreover, there was significant positive interaction effect at emergence stage, the density at maturity period in two experiment at locations reached the maximum when symbiosis time was 10 days and the seeding at 9.0 kg ha^–1; (3) the symbiosis time and seeding amount influenced the growth and development at each period, leaf area index increased when symbiosis time delayed, which led to weak and thin seedlings, therefore, resulting in the changes of yield component, yield per plant as well as plot yield. In conclusion, the rapeseed undersowing rice cultivation model can significantly increase the rapeseed yield, and suggest a favorable condition of 10 days symbiosis and seeding at 9.0 kg ha^–1 for getting higher yield.

Key words: Rapeseed, Undersowing rice, Symbiosis period, Seeding quantity