Combining Physical and Behavioral Response to Salinity

Soil salinity accumulation in California’s Central Valley and other irrigated areas around the world affects agricultural productivity, regional economies, urban areas, and the environment. The direct costs of salinity to agriculture in the California’s Central Valley have been estimated to be equal to US$ 500 million per year. Reduced crop yields from salinity in the root zone account for the largest direct cost of salinity but these losses can be partially offset by regional and field-level management including blending with higher quality water, improving field drainage, or leaching. Effective salinity management must consider the behavioral adjustments by irrigation districts and growers, and importantly, must be based on data available at the regional scale required for policy analysis. In this paper, we estimate crop-specific yield-salinity functions using geo-referenced crop data and shallow groundwater salinity. We model farmers as risk-averse crop portfolio managers and estimate farmer-behavior based yield-salinity functions for six crop groups in Kern County, California. The resulting farmer-behavior based yield-salinity functions account for field-level management of salinity and use the regionally available shallow groundwater salinity to proxy for the true salinity at root zone. We calibrate a regional economic model of Kern County agriculture to evaluate the cost of salinity using the estimated functions, and compare these estimates to the standard field-experiment based yield-salinity functions.