Climate & Sustainability
Research on dry-farmed tomatoes will better equip organic growers to adapt to climate change
New research led by UC Santa Cruz will strengthen understanding of which traits set tomato plants up to be grown successfully without irrigation.
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UC Santa Cruz researchers are evaluating the physiological traits and environmental conditions associated with successful dry-farmed tomato production to better equip West Coast farmers to adapt to a changing climate.
With a $414,800 grant from the California Department of Food and Agriculture (CDFA), Center for Agroecology Executive Director Darryl Wong, Ecology & Evolutionary Biology Professor Jarmila Pittermann, and a team of researchers are collaborating with Oregon State University on a new study entitled, “Climate-Ready Crops: Coupling Dry-Farm Tomato Eco-Physiology with Farmer Adoption in California and Oregon.”
Dry-farming is the production of crops without irrigation, usually in climates with at least 20 inches of annual rainfall, but where most of this rainfall occurs outside of the summer growing season. Agricultural production along the West Coast of the United States has struggled with insufficient irrigation water for decades, and as result, some farmers in this region have adopted and developed innovative crop-production methods, including dry farming. The Center for Agroecology has been practicing and teaching dry farming methods for decades, and in 2017 published a guide on organic dry-farmed tomato production on the Central Coast.
Small-scale organic tomato growers in coastal California and the Willamette Valley of Oregon have employed dry farming for at least two decades. Cool, foggy climates in these locations make for ideal conditions to dry farm tomatoes, and the technique creates an especially flavorful crop. However, drought stress can exacerbate physiological disorders like blossom-end rot, which can result in crop failure. Climate change is making these problems worse by bringing hotter and drier summers to the western United States.
One current challenge farmers face is with the cultivation of dry-farmed ‘Early Girl’ tomatoes, which are a highly valued and sought-after crop, prized by consumers for their sweet, condensed flavor. An increasing number of small-scale organic farmers in coastal California dry-farm this variety, and organic farms in Oregon have undertaken parallel efforts, but the hot summer climate of the Willamette Valley has presented challenges to tomato crops.
In order to successfully continue and expand dry farming practices, breeders and farmers need to develop new tomato varieties that can better tolerate drought and produce high-quality fruit. This will require an improved understanding of the physiological traits that best set tomato plants up for dry farming success, including the degree to which the plants may prioritize drought resistance over fruit yield. Wong and Pittermann’s research will be the first to try to address some of these issues.
“It’s so exciting to see university research coming in to support and understand the practices that growers have been innovating and developing for so long,” said Wong. “Often we think about universities doing the innovation, but in agriculture, it often happens the other way around, with growers following their intuition and expertise, followed by researchers working to understand the processes that underpin those observations.”
The researchers will incorporate variety trials to explore connections between yield and traits such as water-use efficiency, intrinsic drought resistance, growth rates, and time-to-flower, and they’ll also compare irrigated and dry-farmed varieties. The results will help to identify traits that coincide with successful phenotypes, in order to support breeding and seed selection in subsequent years. More than 15 varieties will be planted at Oregon State University and UC Santa Cruz this year and regional growers will have the opportunity to pick the best performing varieties for their own field trials in 2026.
“I am inspired by the possibility of supporting farmers and helping bridge their livelihood with a valuable and disease-resistant crop that requires minimal resource input,” said Pittermann. “It is an amazing feeling to be involved in work that has the potential to impact both the environment and people’s lives.”
The new CDFA grant expands on Agricultural Experiment Station grant-funded work piloted by Pittermann, Environmental Studies Professor Hannah Waterhouse, and Ecology and Evolutionary Biology Ph.D. student Viridiana Castro. The project will also employ students in the SUPERDAR (Supporting Undergraduates by Promoting Education, Research, Diversity, and Agricultural Resilience) Program, with funding from the United States Department of Agriculture’s NextGen Program.
“This research is important not only for its implications for food security as climate predictions become increasingly warmer and drier, but also for the impact it has on undergraduate students who have been involved in the work,” said Castro. “They are passionate about sustainable agriculture and I believe that this work will help enable them to contribute to the field both here at UC Santa Cruz and wherever their careers may take them.”