Abstract:

This study quantified the integrated climate risk posed by multiple hazards to double−cropping early rice in Nanhai district of Foshan, under climate change and identified the sowing period that minimize this risk. Based on annual observations of early rice from the Guangdong agrometeorological experiment station and the daily meteorological data of the Nanhai national meteorological station from 1981 to 2025, the sliding−window correlation analysis identified the critical exposure periods and response variables for the five hazards. K−Means clustering was used to define the threshold of each disaster level, frequency−based probability estimates and cumulative deviation were used to derive hazard and vulnerability indices, and a weighted expectation model was used to calculate an integrated climate risk index for each sowing period group. Robustness was evaluated under four vulnerability weighting scenarios. The results showed that: (1) the critical periods for cold damage, chilling injury, low sunshine, rainstorm and high temperature were sowing to transplanting, transplanting to tillering, 5d before heading to 15d after heading, 15d before heading to 20d after heading and 10d before heading to 20d after heading, respectively. Their corresponding response variables were the duration from sowing to transplanting, the duration from transplanting to tillering, actual yield, seed−setting rate and 1000−grain weight, respectively. (2) Historical sowing dates clustered into early (late February), intermediate (early March) and late (mid−March) groups by K−Means. As the early rice sowing period was delayed, the risk indices for cold damage, chilling injury and low light conditions showed a declining trend, with cold damage decreasing from 1.268 to 0.152, a reduction of 88.0%. In contrast, the high−temperature risk index increases significantly, rising from 1.044 to 1.231, an increase of 17.9%, while the heavy rainfall risk index changed relatively little. (3) The integrated climate risk index for the late−sown early rice group in Nanhai was 1.086, which was 2.25% and 17.29% lower than those of the mid−sown and early−sown groups, respectively. Under four vulnerability weighting scenarios, the ranking of the integrated climate risk indices for early rice across different sowing periods remained consistent, indicating strong robustness of the conclusions. Adjusting the optimal sowing period for early rice in Nanhai district of Foshan, to mid−March can effectively reduce the risk of low spring temperatures and minimize overall climate risk. The findings provide valuable references for optimizing early rice sowing schedules and climate adaptation decisions in similar regions.

Key words: Early rice, Integrated climate?risk index, Sowing period optimization, Agrometeorological hazards, Nanhai district of Foshan