CO2 AND TEMPERATURE EFFECTS ON EVAPOTRANSPIRATION AND IRRIGATED AGRICULTURE

A sensitivity analysis of potential evapotranspiration (PET) rates und er both CO2 and air temperature changes was conducted. PET was modeled with the Penman-Monteith equation so that the effects of atmospheric CO2 concentrations on plant stomatal resistance, and the effects of te mperature on land-surface-atmosphere water vapor exchanges were explic itly taken into account. A root-zone soil-water balance was performed using a physically based soil-crop-climate model to analyze the sensit ivity of soil moisture to changes in atmospheric temperature and CO2 c oncentrations, and the effects of CO2 fertilization on plant photosynt hesis and crop yield. A wide spectrum of directional climate change sc enarios were analyzed, including both a 3 degrees C increase and a 3 d egrees C decrease in air temperature, and both a 50 and a 100% increas e in atmospheric CO2 concentrations. An additive crop yield model and an optimal irrigation scheduling model were used to maximize agricultu ral benefits by maximizing crop yield and minimizing irrigation costs. The model was applied to an irrigated potato crop in the San Luis Val ley of Colorado.