Abstract:

To identify the impact of climate warming on double-cropping late rice, this study evaluated the climatic advantages and disadvantages at different growth stages of late rice with three sowing dates (late June, early July, and mid-July) based on meteorological data from 1981 to 2024 in Keqiao District, Shaoxing City. The results indicated that compared with the period 1981-2000, during 2001-2024, the temperature during the vegetative growth stage of late rice increased, the duration of suitable temperature during the grain filling and ripening stage extended, and the risk of chilling damage during the heading and flowering stage in autumn decreased significantly. However, the risk of high temperature stress during the jointing and booting stage increased. Early July was identified as the optimal sowing window, as it could effectively avoid high temperature at the booting stage and chilling damage at the heading stage, while providing suitable or relatively suitable temperature conditions for grain filling. This sowing date also was best aligned with the local large-scale harvest period of early rice (mid-July). Late June was the suboptimal sowing date, requiring precautions against high temperature at the booting stage, but it coordinated well with the early rice harvest period in early July. Mid-July was not recommended due to the high risk of autumn chilling damage during the heading stage, insufficient temperature during the late grain filling period, and low benefits in farming schedule coordination. This study provides a quantitative basis for optimizing the sowing date arrangement in Keqiao District and analogous double-cropping rice regions.

Key words: double-cropping late rice, sowing date, climatic suitability, high temperature stress, autumn low temperature, climate warming