Abstract:

This study aims to investigate the impact of heat resource variations on winter Brassica napus under the background of climate warming. Daily meteorological data from 2000 to 2020, including the growth period and yield of Zhejiang winter B. napus, were collected from the national first-class agricultural meteorological experimental station of Zhejiang Longyou Station. Statistical analyses, such as simple linear regression equations, Pearson correlation coefficients, 5-day moving averages, and 3-year moving averages were employed to assess the effects of multi-temporal and multi-element heat resources on the growth period and yield of winter B. napus in Zhejiang. The results revealed a clear upward trend in average temperatures in Longyou County, Zhejiang Province during autumn, winter, and spring over the past two decades, with the most significant inter-annual distribution difference observed in winter, reaching its peak in 2020. Additionally, the study found that the initial and final dates of stable through the 10℃ threshold temperature were advanced, along with a significant increase in duration, and a reduction in the longest and shortest days. The budding period of rapeseed had been advanced over the past 20 years, while other growth periods had experienced delays, particularly the green ripening period. The study also highlighted the influence of temperatures in January and February on the early budding period in winter. Furthermore, the entire growth period had increased in recent years, with a significant advance in the maturation period and an increase in the accumulated temperature above 10℃. Both the actual and trend yields of rapeseed had exhibited an increasing trend, with climatic yield also showing an upward trajectory, but there were significant inter-annual fluctuations. The study identified a positive correlation between the average temperature in late October and the climatic yield, indicating favorable conditions for the robust growth of rapeseed seedlings before winter, as well as the promotion of cotyledon growth and the development of strong seedlings. The main climatic factors affecting rapeseed yield were found to be low temperatures during the overwintering period and high temperatures after spring. The study suggests that the advance of initial and final dates, along with appropriate late sowing of rapeseed, can enhance the utilization of heat resources during the seedling stage, promoting robust seedlings, early budding, and early bolting, ultimately leading to high rapeseed yields and abundant harvests.

Key words: thermal resources, Brassica napus, winter rapeseed, growth period, yield, Zhejiang