Effect of climate change-induced water-deficit stress on long-term rice yield

June (maturity stage), and the warm cropping season starts in late July or early August (initial stage) and ends in late November (maturity stage). The patterns of temperature variation are opposite in the two cropping seasons. The average temperature increases throughout the cool cropping season while the average temperature decreases throughout the warm cropping sea- son. The patterns of variation in reference evapotranspiration under the four growth stages of rice were the opposite between the cool and warm cropping seasons (Fig 2). Thus, to reveal the climatic effect, the rice yield response to climate variables needs to be analyzed separately in the cool and warm cropping seasons. The value for Qiu et al. [37] differentiates the changes in the seasonal crop evapotranspiration of rice in terms of growth duration under varying types of warming patterns using an evapotranspiration estimation model. The reference evapotrans- piration increased throughout the cool cropping season, whereas it decreased throughout the warm cropping season (Fig 2). The different patterns of temporal and spatial variation in the reference evapotranspiration and sensitivity coefficient responses to precipitation and temper- ature were investigated [38, 39]. Long-term decreasing trends and negative values in crop water status were observed at all four growth stages in the two cropping seasons (Fig 3). This result showed that increasing crop water deficiency led to greater water-deficit stress on rice growth. The decreased crop water

status was due to the increased air temperature and decreased rainfall [1]. The water deficit is limiting the growth and productivity of crops and has been a major problem for crop produc- tion worldwide, especially in rain-fed agricultural areas [40–42]. In the cool cropping season, the decreasing trend of crop water status was severe during the initial and maturity stages and mild during the reproductive stage (Fig 3). Compared with the cool cropping season, the decreasing trend in crop water status in the warm cropping season was relatively small under the four growth stages (Fig 3). This result may be due to the greater temperature increase and rainfall decrease in the cool season as opposed to the warm season [43]. The rice yield changes related to the crop water status were negative during the rice devel- opment stage (except for the warm cropping season from 1945–1983). This result suggests that crop water may be a determining factor for rice growth during the development stage [22, 44]. The rice yield changes related to the crop water status were positive during the rice reproduc- tive stage (except for the warm cropping season over the period 1996–2019). This result sug- gests that crop water may not be a determining factor for rice growth during the reproductive stage [22, 45]. In recent years, from 1996 to 2019, negative yield changes were observed under all four growth stages in the cool cropping season and under crop development, reproductive, and maturity stages in the warm cropping season. This result may suggest that water-deficit

stress has had a greater effect on rice growth in recent years [46, 47]. The values of crop water status under the four growth stages had little correlation with each other in both the cool (| r | � 0.24) and warm (| r | � 0.16) cropping seasons (Table 2). The annual variations in the yields of the cultivars with overlapping cultivation periods were Table 2. Correlation coefficients of crop water status among growth stages in the cool and warm cropping seasons. Cool cropping season Warm cropping season Growth stage INI DEV REP Growth stage INI DEV REP Cool cropping season DEV 0.222* - - Warm cropping season DEV -0.151 - - REP 0.154 0.045 - REP -0.102 0.087 - MAT 0.235* 0.059 0.094 MAT -0.074 -0.117 0.002 INI, DEV, REP, and MAT represent initial, crop development, reproductive, and maturity stages, respectively. * represents p-value < 0.05. https://doi.org/10.1371/journal.pone.0284290.t002 PLOS ONE Effect of climate change-induced water-deficit stress on long-term rice yield PLOS ONE | https://doi.org/10.1371/journal.pone.0284290 April 17, 2023 9 / 14