Rice yield variability in Preah Vihear, Cambodia, was studied through on-farm trials testing nine varieties under different ecosystems and management systems. Climate factors like frequency of high temperature (>33°C), and humidity were major drivers of yield variability. Local varieties showed broad adaptability, while improved ones performed best in irrigated systems. Five varieties performed better under green manure management. However, the limited fit of improved varieties to agroecological systems highlights the need to breed resilient, high-yielding varieties using local genetic diversity.