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

resources [6, 7]. It is suggested that water availability and crop productivity will decrease sig- nificantly, and climate change will have an impact on irrigation water requirements and crop yield [8, 9]. Crop yield change is expected due to the shifting growth phase and photosyn- thetic capacity, and increasing respiration and water requirements, which result from climate change [10, 11]. To investigate the general effects of crop yield change on climate change, it is necessary to analyze long-term temporal variations between crop yields and climate variables [12–14]. To improve water-use efficiency in irrigated agriculture, it is important to study and understand crop water requirements. Evapotranspiration is a vital component when describing the hydrological cycle in ecological systems, estimating water balance, and deter- mining water availability along with precipitation [15, 16]. Reference evapotranspiration (ET0) is a parameter of climatic conditions that has been widely investigated as an indicator of climate change [17, 18]. Crop evapotranspiration (ETC) is a variable for the optimization of irrigation water productivity and designing the schedule of irrigation in the implementa- tion of agricultural water management [19] (Gong et al., 2020) and is highly influenced by irrigation water supply under different irrigation levels [20, 21]. The Penman-Monteith (PM) model based on the Food and Agriculture Organization (FAO)-56 guidelines has served as a reference method because it produces the most accurate results compared to lysi-

metric measurements [22, 23]. The PM model has been widely used for the estimation of daily or monthly ET0 in different agro-climatic zones by many researchers for decades [22, 24, 25]. Rice is a semi-aquatic plant that depends on the rainfall and temperature of the cultivation area and hence, is heavily affected by climate change [5, 26]. Severe effects of drought and high temperature on the growth and yield of rice due to insufficient water supply and improper scheduling of irrigation have been reported [27, 28]. Some reports have revealed that rice yield may be affected by temperature and precipitation because of some physiological mechanisms [29, 30]. Although many studies have revealed the impacts of climate change on crop produc- tion utilizing climate model projections of temperatures and rainfall [31, 32], the number of studies that analyze the effect of water-deficit stress on rice yield using long-term field experi- mental data is limited. Water deficit stress occurs when the amount of water required is greater than the amount of water available during a certain time. Our goal was to assess the effects of water deficit stress on rice yields throughout the major cropping seasons. In this study, we analyzed the yield data of 12 rice cultivars in cool and warm cropping seasons, separately, from field experiments con- ducted under irrigated conditions with optimal management at a research station in Taichung, Taiwan over the period 1925–2019. First, weather data, including average, maximum, and

minimum temperatures, humidity, wind speed, and sunshine duration, collected at the research farm were used to compute the long-term temporal trends of reference evapotranspi- ration during the initial, crop development, reproductive, and maturity stages of rice growth during the 95 years. Second, the crop evapotranspiration of rice under the growth stages was calculated using the estimated reference evapotranspiration and crop coefficient of rice. Third, the crop water status during the growth stages was calculated using the estimated crop evapo- transpiration and collected rainfall data. Fourth, long-term temporal trends in crop water sta- tus during the growth stages were deduced to reveal the temporal trend in water-deficit stress. Fifth, a multiple linear regression model was applied to evaluate the relationships between rice grain yield and water-deficit stress during the four growth stages. Finally, total yield changes computed from the regression coefficients for each growth stage over the periods 1925–1944, 1945–1983, and 1996–2019 were used separately to reveal the effects of water-deficit stress on rice yield and the temporal variations during the experimental period. 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 2 / 14