The high yield predicted by the model f_irrigated is due to water supply embeded in the function.
The water supply effect
f_irrigated(LST_irrigated, ...) - f_rainfed(LST_irrigated, ...).
yield = year + lst6^2 + lst7^2 + lst8^2 + precip6^2 + precip7^2 + precip8^2
Results