An Economic and Biophysical Model of Deficit Irrigation

Abstract

Competition for scarce water resources may lead to high water prices. Agricultural producers can adapt to increasing water price by adjusting irrigation management strategies. When water prices are high, deficit irrigation, the purposeful reduction of irrigation to reduce water use while accepting reduced yield, may increase net income. Deficit irrigation decisions depend on economic, biological, and physical conditions. A model based on relationships among the amount and cost of irrigation water applied, water productivity, and the value of water saved and crop yield was developed to assist farmers making deficit irrigation decisions. A model application for irrigated maize (Zia mays L.) production in northeast Colorado illustrates conditions under which deficit irrigation increases net income. High water costs and low crop prices favor deficit irrigation. When water has value for leasing, the combination of deficit irrigation production to reduce water use and water leasing may increase net income. Sufficiently high lease prices and low commodity prices favor rainfed production or fallowing.Core Ideas Deficit irrigation may increase net farm income. Expensive water, low crop prices, and high elasticity of water productivity favor deficit irrigation. Combining economic with biophysical models improves applicability.