4.2. Effects of warming on soybean yield
The optimum temperatures for soybean are 15–22 °C at the emergence stage, 20–25 °C at the flowering stage, and 15–22 °C at the maturity stage [36]. Seed yield and yield formation of soybean are frequently reduced by temperatures above approximately 30 °C [22] and [39]. In the present study, mean air temperatures ranged from 20 to 37 °C under warming from anthesis to maturity stages (Fig. 1a), above the optimum temperature ranges of soybean growth. Thus, warming was not beneficial for soybean yield.