Water and nitrogen are primary inputs to irrigated agricultural production systems. Improved irrigation water management requires accurate estimates of crop evapotranspiration on at least a daily basis. Spatial and temporal variability of soil nitrogen supply together with temporal variability of plant nitrogen demand make conventional nitrogen management difficult. Since the plant is an integrator of its environment, measurements that express the plants' behavior to its environmental surroundings should improve management of these two inputs. Examples will be presented showing applications of ground-based remotely sensed plant data to improve techniques for both water and nitrogen management.