2017 ASHS Annual Conference

Cool season vegetables require adequate soil moisture to assure that maximum yield and quality are achieved. On the central coast of California, where a majority of cool season vegetables are produced in the US, over-pumping of irrigation water has reduced groundwater levels and has led to environmental degradation. Evapotranspiration (ET) based irrigation scheduling can increase water use efficiency of many crops and minimize environmental impacts such as nitrate leaching and surface water run-off. Irrigation trials were performed to evaluate if ET-based irrigation scheduling could conserve water and optimize yield and quality of romaine lettuce (Lactuca sativa L. cv. Sun Valley) near Salinas, CA during 2015 and 2016. Crops were seeded in 2 rows on 1-m wide raised beds on a Chualar sandy loam soil. Sprinklers were used for germinating seed and crop establishment. Plants were thinned to 20-25 cm spacing 1 month after planting. After converting to surface drip, 4 irrigation treatments were imposed in a complete randomized block design with 6 replications. Treatments represented 50%, 75%, 100%, and 150% evapotranspiration (ET) replacement for a typical romaine crop. Guidance for ET estimation was provided by CropManage decision-support tool (U.C. Cooperative Extension, cropmanage.ucanr.edu), operating in conjunction with daily reference ET from the California Irrigation Management Information System (Calif. DWR). Applied water for both sprinkler and drip was monitored with flow meters. Marketable yield was evaluated at crop maturity for carton and cored products. Yields from the 100% and 150% ET treatments were not significantly different and were similar to industry averages, while yields were significantly lower for the 50% and 75% ET treatments. The 100% ET treatment resulted in the greatest water and N-use efficiency.