Abstract:

To prevent the blind extension of sowing date, the research was conducted through field sowing test at different stages and the analysis of heat distribution, combined with the study on the developmental period and the biological factors. The results showed that: although the early sowing early rice once reached the highest tillering rate, suitable sowing early rice still achieved the highest effective stem multiple at the harvest time; the total maximum biomass was obtained by early sowing, and the ideal yield was obtained by suitable sowing; early sowing early rice had more non-effective tillers; the suitable sowing hold an advantage in yield structure; late sowing early rice did not perform well on the number of panicles and single-earned panicles; early sowing early rice had high management cost and showed a high probability of suffering low temperature at seedling stage and heavy rain during the flowering period; late sowing early rice was easy to suffer from extreme heat at heading and filling stage, which had adverse effects on chlorophyll, photosynthesis and rice quality. To extend the sowing date, the risk caused by climate change and its repetitiveness, and the different effects of heat distribution on the biomass and yield should be considered comprehensively.

Key words: sowing date, thermal efficiency, multiple of stem, chlorophyll content, photosynthetic rate