CO2and Temperature Effects on Evapotranspiration and Irrigated Agriculture

Abstract
A sensitivity analysis of potential evapotranspiration (PET) rates under both CO 2 and air temperature changes was conducted. PET was modeled with the Penman-Monteith equation so that the effects of atmospheric CO 2 concentrations on plant stomatal resistance, and the effects of temperature on land-surface–atmosphere water vapor exchanges were explicitly taken into account. A root-zone soil-water balance was performed using a physically based soil-crop-climate model to analyze the sensitivity of soil moisture to changes in atmospheric temperature and CO 2 concentrations, and the effects of CO 2 fertilization on plant photosynthesis and crop yield. A wide spectrum of directional climate change scenarios were analyzed, including both a 3°C increase and a 3°C decrease in air temperature, and both a 50 and a 100% increase in atmospheric CO 2 concentrations. An additive crop yield model and an optimal irrigation scheduling model were used to maximize agricultural benefits by maximizing crop yield and minimizing irrigation costs. The model was applied to an irrigated potato crop in the San Luis Valley of Colorado.