Recently, the intensification of the contrast between Taiwan’s wet and dry seasons due to climate change has led to stringent water use restrictions in agriculture, significantly impacting Taiwan’s primary staple crop, rice. This necessitates the development of effective agricultural management strategies to ensure the resilience of Taiwan’s agriculture. Therefore, we simulated potential challenges in rice cultivation due to climate change under specific conditions: flooded cultivation and soil water tension levels of −20 and −40 kPa. At −40 kPa, the soil becomes excessively dry, causing severe soil surface cracking. This results in a 20% reduction in plant height and a 30% decrease in yield compared to flooded cultivation. At −20 kPa, plant height and yield are comparable to those under flooded conditions. In resource efficiency, flooded cultivation demonstrates low irrigation water use efficiency (0.22 and 0.42 kg/m³) due to sustained high water levels. Conversely, the condition with −20 kPa shows the highest irrigation water use efficiency (2.15 and 2.16 kg/m³) with no significant difference in nitrogen use efficiency compared to flooded management. Although the irrigation water use efficiency under −40 kPa is better than flooded management (0.87 and 1.02 kg/m³), the nitrogen utilization efficiency is significantly low. Irrigation under the condition of −20 kPa climate change does not reduce yields and offers additional benefits. This strategy ensures stable crop production and conserves water resources for crop cultivation during the dry season, providing an effective means to stabilize production and mitigate the impacts of climate change on Taiwan’s agriculture.

Water-saving irrigation can substantially reduce water inputs in rice production, but excessive soil drying may impair physiological activity during grain filling and reduce yield. This study evaluated continuous flooding (CF), moderate water-saving irrigation (SW; −20 kPa), and intensified water-saving irrigation (IW; −40 kPa) in rice. Flag-leaf relative chlorophyll content and net photosynthetic rate, superior-grain development, yield components, grain yield, irrigation water input, and water productivity (WP) were evaluated. SW reduced irrigation water input by 57.4% relative to CF while maintaining a comparable grain yield (4545.0 vs. 4550.7 kg ha⁻¹), resulting in the highest WP (0.54 kg m⁻³). In contrast, IW reduced grain yield to 3694.4 kg ha⁻¹. During late grain filling, SW maintained flag-leaf chlorophyll status and photosynthetic activity comparable to CF, whereas IW showed greater reductions at 28 and 35 days after flowering. IW also exhibited lower relative grain volume during the middle-to-late grain-filling period. Plot-level regression analyses showed positive associations among flag-leaf chlorophyll status, photosynthetic rate, relative grain volume, and final grain yield. These results indicate that moderate soil water tension can substantially reduce irrigation requirements while maintaining late-stage physiological activity, grain development, and yield, whereas intensified soil drying provides limited additional water savings at the expense of crop productivity.