California Agriculture

Processing tomato yields have increased by 53% over the past 35 years, but the current seasonal crop-evapotranspiration requirements that growers use to schedule irrigation are based on 1970s-era data. We updated this data and developed new crop coefficients for processing tomatoes using the Bowen ratio energy balance method in eight commercial fields from 2001 to 2004. Today’s evapotranspiration rates are similar to those of the early 1970s, indicating a substantial increase in water-use efficiency by processing tomatoes during the past 35 years. In addition, we collected data in both furrow- and drip-irrigated fields, but no statistical differences were found between them.