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A lot of produce can be dry-farmed, such as these Native Sun and Marmande tomatoes grown near Portland, Ore.

In the parking lot behind a grocery store in Portland, Ore., last September, several hundred tomato aficionados gathered on a sunny, breezy day for Tomato Fest. While many attendees devoured slices of tomato quiche and admired garlands of tomatoes with curiously pointed ends, I beelined to a yellow-tented booth hosted by Oregon State University. Agricultural researcher Matt Davis was handing out samples of experimental tomatoes.

I took four small plastic bags, each labeled with a cryptic set of letters and numbers and containing a thick slice of a yellow tomato. Scanning a QR code with my phone led me to an online survey with questions about each tomato’s balance of acidity and sweetness, texture and overall flavor. As I chewed on the slice from the bag marked “d86,” I noted the firm, almost meaty texture. Lacking the wateriness of a typical supermarket tomato, it would hold up beautifully in a salad or on a burger, I thought. And most importantly, it was tasty.

I learned later that this tomato had been dry-farmed, a form of agriculture that doesn’t require irrigation. Dry farming has roots stretching back millennia. But in the western United States, the practice largely fell out of widespread use in the 20th century.

Today, however, farmers in the West are once again experimenting with dry farming as they grapple with water shortages, which are being exacerbated by rising temperatures and more frequent and intense droughts linked to climate change.

Finding a more sustainable way to grow food in a thirsty state like California, for example, where agriculture accounts for roughly 80 percent of water usage and where a third of U.S. vegetables are grown, is a top priority. Dry farming won’t solve all of agriculture’s woes, but it offers a way forward, particularly for smaller-scale producers, while drawing less on a scarce natural resource. And even though the practice isn’t without limitations — dry-farmed produce tends to be physically smaller, and harvests are less bountiful overall — its benefits extend beyond water savings: Dry farming can also yield longer-lasting and better-tasting produce.

It’s a common misconception that dry farming means growing plants without water. “Nothing grows without water,” says Amy Garrett, president of the nonprofit Dry Farming Institute in Corvallis, Ore. Instead, dry-farmed plants take up moisture stored in the ground rather than sprinkled from above.

Dry farming is possible in states throughout the West. What’s needed is a wet rainy season, when rainwater infiltrates the soil, followed by a dry growing season, when plant roots pull in that moisture as needed. A wide variety of fruits and vegetables — including tomatoes, potatoes, squash, corn and even watermelons — can be dry-farmed. Dry farming is distinct from rain-fed agriculture, when crops grow during a wet season without the aid of irrigation.

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For dry farming to work, a couple elements are essential. “You need to be in a place where there’s sufficient rainfall to create moisture in the soil,” says David Runsten, water policy director at the Community Alliance with Family Farmers in Davis, Calif. Sites must generally receive more than 50 centimeters of annual precipitation — in 2022, that was true in 26 of California’s 58 counties, for example — and the soil must be composed of fine grains that help retain that water over time.

Beyond that, farmers employ a range of techniques to help crops get all the moisture they need. Those methods include planting earlier in the season than usual to take advantage of soil moisture stored up from winter rains and spacing plants more widely to give roots more room to search for water. Farmers can also plant young seedlings in furrows to minimize the drying effects of the wind and lay down an insulating layer of mulch — often leaves, wood chips or straw — on top of the soil.

Dry farming is standard practice in many places around the world, from olive groves in the Mediterranean to melon fields in Botswana to vineyards in Chile. In the American West, dry farming has a long history stretching back thousands of years among Indigenous peoples.

“Dry farming is just farming — it’s our way of life,” says Michael Kotutwa Johnson, an Indigenous resiliency specialist at the University of Arizona in Tucson. He’s also a member of the Hopi Tribe and dry-farms corn, lima beans and other crops. He learned the practice from his grandfather.

The intimate knowledge of the natural world that dry farming requires aligns with the Hopi community’s values and spiritual beliefs, he says. “You get to really learn what the environment gives you, and you learn to reciprocate.” A relationship develops between the cropping system and the farmer, he says. “It’s a beautiful thing, and it’s something that needs to be cherished.”

As non-Indigenous people started arriving in the West, they too began to dry-farm. But by the 20th century, many commercial farmers started relying on irrigation to capture growing markets. Having water on demand gave farmers more control and allowed them to boost production, says Jay Lund, vice director of the Center for Watershed Sciences at the University of California, Davis. “They could have a lot more reliable crop yields, and much higher crop yields.”

But today, irrigation water in many parts of the West is in short supply. In places like California’s San Joaquin Valley — the state’s largest agricultural region — water is pumped up from deep aquifers and often transported through canals and pipes before being deposited on crops. Researchers estimate that more than a quarter of irrigation water can be lost during transport due to evaporation and leaks. An even bigger problem in this region is that water is being extracted from the ground at a faster rate than it’s being replenished. “There just isn’t sufficient water for the amount of farmland that’s been planted,” Runsten says.

And access to irrigation is already being curtailed. Farmers in California and other states in the West are experiencing water shortages and have at times been entirely cut off from irrigation (SN: 9/25/21, p. 16).

That’s not likely to change in the future, Runsten says. To meet the goals of California’s 2014 Sustainable Groundwater Management Act, for instance, more than 200,000 hectares of irrigated farmland in the San Joaquin Valley — roughly 10 percent — will need to be taken out of irrigated production by 2040. Dry-farming speciality crops like agave or jujube, an Asian fruit similar to a date, could be an economically attractive alternative for the land, according to a 2022 report by the nonprofit Public Policy Institute of California.

Catherine Nguyen, who farms on a little less than half a hectare of leased land outside of Portland, Ore., in the Willamette Valley, has been dry-farming for two years. Nguyen — whose customers include farmers market shoppers, members of her community supported agriculture, or CSA, program and small restaurants — was drawn to the practice in part out of curiosity. “I love experimentation and with the changing climate and cost of water, it seemed like something to learn more about,” she says. A portion of her property also lacks access to irrigation, so dry farming made it possible to use land that would otherwise remain fallow.

Potatoes were the first crop Nguyen dry-farmed. Beyond saving roughly 7,500 liters of water, Nguyen and her small crew discovered other benefits. There was no need for sprinklers, drip tape, hosing or any other irrigation equipment. That meant Nguyen’s farm could cut down on a lot of plastic equipment intended to last for just one or two growing seasons. “Not only is our water usage down, but so is our plastic usage,” Nguyen says. That lighter environmental touch is important to Nguyen, who uses farming methods that promote healthy soil ecosystems, including minimal tillage and cover cropping, which involves growing plants specifically to improve the soil rather than for a harvest (SN Online: 4/12/22).

Last year, Nguyen dry-farmed delicata squash, corn, tomatoes, potatoes and beans. Nguyen noticed that her dry-farmed plots contained only about a fifth of the weeds that grow in her irrigated plots. That’s another known advantage of dry farming, Garrett says. Irrigation creates conditions for weed growth: Dispensing water through above­ground sprinklers causes moisture to pool near the surface, precisely where weeds wait for water, she says. “There is a weed seed bank in the top few inches of soil.”

Not having to pull up as many weeds or apply herbicides can translate into labor savings. Coupled with not having to manage irrigation infrastructure, dry farming can streamline a growing operation, Garrett says. “There’s a lot less to do.” Labor accounts for more than a quarter of total production costs for U.S. fruit and vegetable farmers.

Another benefit is that the produce contains less water and therefore tends to store better. In 2016 and 2017, Alex Stone, a horticulturist at Oregon State University, and her student Jennifer Wetzel grew different varieties of winter squash at the university’s research farm in Corvallis. The pair irrigated some vegetable plots and dry-farmed others. After harvesting the squash and leaving them in storage for four months, Stone and Wetzel found that about 1,000 of the roughly 1,250 dry-farmed winter squash, or about 80 percent, were still marketable. But only about 600 of the roughly 1,150 irrigated winter squash, or about 50 percent, were marketable.

Dry-farmed tomatoes grow longer roots (plant on the left in the photograph) than irrigated tomatoes (plant on the right). Dry-farmed tomatoes are planted early in spring so they can access water in the topsoil (darker brown in the diagram). A lack of irrigation in summer encourages the roots to go searching for water as the soil dries out. By fall, the roots can be more than a meter deep.

Longer-lasting produce is a boon for small-scale fruit and vegetable growers, Garrett says. Winter is often a slow time sales-wise because there’s not much ripening. Selling stored crops in winter is one way that these farmers can earn an income during that lull. “If winter squash is storing months longer, that makes a huge impact for our local growers,” she says. Produce that lasts longer also means less food waste, both in farmers’ storage bins and in shoppers’ refrigerators and pantries.

Dry farming does have its downsides, however. The practice tends to produce smaller fruits and vegetables. That’s a natural outcome of withholding irrigation, Lund says. “The plant has less water to feed the growth of the fruit.” And growers, to say nothing of shoppers, can be wary of diminutively sized produce. That’s true among farmers in Oregon, Stone says. “They want a big, red tomato.”

Overall yields also tend to be lower. Not only does a dry-farmed plant produce fewer fruits or vegetables, but it also needs more space than its irrigated brethren so that its root system can spread out in search of water. Dry-farmed tomatoes, for instance, are typically planted almost two meters apart in rows separated by about two meters. Irrigated tomatoes can grow much closer together, about 60 centimeters apart, with rows separated by a meter or so.

Stone and Wetzel found that yields of irrigated winter squash at Oregon State’s research farm averaged 35.7 metric tons per hectare in 2016 and 32.2 metric tons in 2017. Dry-farmed squash yields were only 37 to 76 percent as much.

Diminished harvests can be a challenge. “With land access already being one of the biggest obstacles to farming, sometimes it’s hard for me to justify dry farming,” Nguyen says. Last year, she dry-farmed on only about a tenth of her property. “I do have to consider yield per square foot when deciding how much land to dry-farm,” she says.

Smaller harvests can translate to more expensive produce. “You don’t have the economies of scale,” Lund says. “Your costs are much higher per unit of production.” Dry-farmed tomatoes, for instance, typically sell for $4–$6 per pound and are primarily found at farmers markets and specialty grocery stores. That’s compared with $2–$3 per pound for traditional supermarket tomatoes grown with irrigation.

Dry-farmed produce may never become truly mainstream, Johnson says. “I don’t see us moving in that direction as long as we still have a market system that’s based on efficiency and quantity.” But many dry farming experts argue that paying more for dry-farmed produce is an investment in the future. And, they point out, dry-farmed produce tastes better.

In California’s Napa Valley, there’s nary an irrigation hose snaking through Dominus Estate’s roughly 55-hectare Napanook Vineyard. Every last one of the more than 100,000 cabernet sauvignon, cabernet franc and petit verdot grapevines planted there is dry-farmed.

The water savings are tremendous, says Tod Mostero, Dominus Estate’s director of viticulture and winemaking. A single irrigated grapevine is typically irrigated with nearly 40 liters of water several times or more over the growing season, he says. For a vineyard the size of Napanook, that translates to nearly 4 million liters, or about a million gallons, for just one watering, Mostero says. In drought-prone California, that’s not sustainable, he says. “Pumping millions of gallons of water out of the soil is not something that we can continue to do.”

Beyond the water savings, there’s another reason Napanook Vineyard is dry-farmed, Mostero says. The practice produces the best wines, he contends. When grapevines are dry-farmed, the unique flavors of a wine associated with a place, and even a vintage, often shine through. Grapevines can send roots up to six meters deep in search of moisture. As those roots pass through layers of soil and rock, they absorb a complex set of minerals unique to that location, Mostero says. “You really find the terroir, the subtle differences between different areas.” For that very reason, some wine-growing regions, in parts of Europe for example, forbid vineyards from irrigating wine grapes.

Oenophiles aren’t the only ones swearing by the superior flavors of dry-farmed fruits and vegetables. Laurence Jossel, the chef-owner of Nopa, a restaurant in San Francisco that specializes in wood-fired cuisine, sources dry-farmed tomatoes from local farms. Tomatoes that are bloated with water taste “boring,” Jossel maintains. “The acid is gone, and the sweetness is gone.” He uses dry-farmed tomatoes in everything from soups to flatbreads. Sometimes they’re the star ingredient: A salad of chopped tomatoes topped with a bit of feta or mozzarella is one of Nopa’s summer offerings. “The tomato itself is just amazing,” he says.

Despite the environmental benefits of dry farming, some farmers remain wary. Stone has found that growers in Oregon are often cautious about the practice, even when it comes to cultivating varieties that sell well elsewhere. A case in point is Early Girl tomatoes, which are extensively dry-farmed in California and available at both California supermarkets and farmers markets.

“They just see them as elite, expensive, small tomatoes,” Stone says.

To explore the economic viability of dry farming, Stone is leading farming trials of dry-farmed crops to determine which varieties are most suited to commercial production. In recent years, she and colleagues have focused on tomatoes, which, after potatoes, are the most commonly consumed vegetable in the United States. (Technically a fruit, tomatoes are considered a vegetable for nutritional and culinary purposes by the U.S. Department of Agriculture.)

Stone’s team at Oregon State has grown hundreds of types of tomatoes. By recording yields, susceptibility to common diseases like blossom-end rot, and the size, firmness and flavor of the tomatoes, the researchers have started to home in on varieties that thrive — and taste good — when the irrigation is turned off. The first yellow tomato I sampled at Tomato Fest is one of the researchers’ leading contenders.

Dry farming offers one way forward as water resources become more unpredictable in the future. But it’s not a one-size-fits-all panacea for climate change, researchers admit. In some cases, crops that once thrived without irrigation may no longer do well at some point in the future.

“As summers become hotter and drier, crops will require even more water as they will lose more water [through evapotranspiration], making dry farming riskier,” Stone says.

Some farmers may have to swap one type of crop for another that’s more suited to even drier conditions. Fruit trees with particularly long, deep roots are good bets, Garrett says, as are species like melons that originally evolved in arid locales.

Whatever the future holds, being adaptable will be key. Farmers must be prepared to respond to changing conditions, Johnson says, but must also allow nature to lead. After all, that’s worked for his community for thousands of years.

“We raise corn to fit the environment,” he says. “We do not manipulate the environment to fit the corn.”

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A version of this article appears in the March 11, 2023 issue of Science News.

J.D. Wetzel. Winter squash: Production and storage of a late witner local food. Graduate thesis at Oregon State University.

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