Abstract: The effects of low temperature and rainy weather at seedling state on soybean yield were examined to provide basis for the prevention and reduction of soybean disaster. The localization and adaptability of WOFOST model were firstly tested based on the observation data of soybean growth in Heilongjiang Province and the results of previous research. Using daily meteorological data, regional crop parameters and soil parameters from 15 representative stations in the study area during 1971-2020, soybean yield under different low temperature and rainy scenarios was simulated, and the influence of low temperature and rainy weather at seedling stage on soybean yield was quantitatively evaluated. The results showed that the localization application of WOFOST model was effective in Heilongjiang Province and thus it could be used to simulate soybean yield in this region. Under the scenarios set here, low temperature, rainy weather and their combined effects would lead to significant reductions of soybean yield. The duration of combined effects was the main factor leading to soybean yield reduction. The t_-3.5 scenario lasting for 6 days had no significant effect on soybean yield, while some cases of t_-3.5 scenario lasting for 12 days and most cases of t_-3.5 scenario lasting for 18 days significantly reduced soybean yield. Under the context of the same duration and degree of agro-disaster, the combined occurrence of low temperature and heavy rain had stronger effect on soybean yield than that of the two alone.

Key words: soybean, low temperature and rainy superposition effect, WOFOST model, yield, seedling stage