SAN JUAN BAUTISTA — Jim Leap fondly recalls the first Early Girl tomatoes he grew at UC Santa Cruz’s farm in 1990. Sweet and bursting with flavor, they were raised without a single drop of irrigated water.

Nearly three decades later, he remains deeply committed to “dry farming” — forsaking modern irrigation and relying on seasonal rainfall to grow tomatoes, winter squash, potatoes, dry beans and corn on the 4-acre San Juan Bautista farm that Leap and his wife, Polly Goldman, have owned for eight years.

“What motivated us to dry farm was the environmental ethic,” Goldman said. “We are not using city water or groundwater.”

As California gets hotter and drier because of climate change, Leap, Goldman and other members of this small but brave band of farmers predict that dry farming and other water-sparing techniques will become more popular in the Golden State.

While unfamiliar to many consumers, dry farming is an age-old practice that entails carefully managing soils to lock winter rainfall into the top layers until it’s time to begin growing crops during the spring and summer. As little as 20 inches of rain – roughly the same amount that the Central Coast receives each winter on average – can sustain crops in the months without rainfall, with no need to add any extra water.

The strategy has been used for generations by grape and olive growers in Mediterranean countries such as Italy and Spain. It was also common in coastal California through most of the 19th and early 20th centuries.

But practices changed as farmers got better at extracting water from under the ground. Yields boomed, and our food supply became more reliable. And so did our reliance on groundwater.

Today, many of the state’s water basins – particularly in the Central Valley, the state’s agricultural hub – are so overdrawn that they’re unable to replenish themselves.

California’s 2014 Sustainable Groundwater Management Act is aimed at ensuring that local and regional agencies better manage the amount of water pumped from wells. This means that groundwater supplies in the future are likely to be limited for farmers, who account for about 80 percent of California’s water consumption. And scientists predict that intense and frequent droughts caused by global warming will likely tighten water supplies further.

In some parts of California, growers such as Stan Devoto already see dry farming as a necessity.

“It is the way we have to farm in western Sonoma County if we’re going to grow apples,” said Devoto, a dry farmer who owns a 25-acre apple orchard in Sebastopol.

“I can literally count on one hand the growers that have adequate water to irrigate the orchards,” he said of the area, where farmers have long dealt with declining water levels and salt water creeping into freshwater basins.

Not for everyone

But not everyone can dry farm, and not all crops can be dry farmed. It works best in certain climates and soil types.

The best-suited regions are those with clayey subsoil that experience morning fog and mild summer afternoons, with temperatures that rarely exceed 90 degrees.

“In the Central Valley, it’s really challenging,” said Rachel Long, a farm adviser at the University of California Cooperative Extension. “It doesn’t rain enough, and the temperatures are in the 90s and 100s.”

Also, fewer plants can be grown per acre, making dry farming less lucrative than conventional farming.

“It’s tricky and takes a lot of experience,” said Leap, 63.

The growing season for Leap and his wife usually starts in October, when they plant a mix of legumes, vegetables and cereal crops. If the rains don’t arrive, the couple has to wait until later in the fall.

Over the winter, these “cover crops” will flourish and mature. As they grow, the crops’ roots acquire nutrients from the soil. And any weeds that try to establish themselves will get shaded out by the thick canopy formed by these crops.

In March, as the rains ease, Leap will mow the green leafy matter and let it enrich the soil. In early April, he will till the topsoil, creating mulch that will lock in the soil moisture.

“You can almost think of it as though you’ve laid out a plastic tarp on the soil,” Leap said. The water that gets trapped, he said, will support the vegetables grown in the summer.

As the summer progresses, however, plant roots must go deeper and wider to meet their water needs. That means dry-farmed tomato plants must be spaced much further apart, reducing the total number of plants from 5,400 an acre with irrigation to 1,210 per acre when dry farmed, Leap said.

The upside is that the water savings are substantial. At UC Santa Cruz’s farm, every acre of dry-farmed tomatoes saves an acre-foot of water – enough to flood three-quarters of a football field one foot deep.

And dry-farmed tomatoes, apples, grapes and almonds also have more character, according to supporters of the practice. They say that unlike irrigated fruits with diluted flavor profiles, dry-farmed fruits are smaller and have a dense, concentrated flavor.

A triple-win situation

Paul Cocking, owner of the Gabriella Cafe in Santa Cruz, uses dry-farmed tomatoes as much as he can at his restaurant. “The tomatoes have better flavor, and they are better for the soil and better for the environment,” he said. “It’s a triple-win situation.”

But because yields are lower, the prices are higher. A consumer must be willing to pay at least 30 percent more for a pound of dry-farmed tomatoes.

“That’s the only way to make it profitable,” Leap said.

Mark Bartle, who has been growing dry-farmed tomatoes on his 19-acre Two Dog Farm near Davenport since 2001, said he has no trouble selling them.

He sells 60 percent of his Early Girl tomatoes at farmers’ markets and three independent grocery stores in San Francisco, as well as at the Whole Foods and New Leaf stores in Santa Cruz.

“There is a big demand,” he said.

The New Leaf store on the west side of Santa Cruz sells an average of 1,000 pounds of dry-farmed tomatoes each week from August to November, when the tomatoes are in season, Bartle said.

“We sell dry-farmed tomatoes more than any other kind when they are available,” said Bartle, who also works part-time in the produce department at the store.

Less than 1 percent

Still, Leap and Bartle acknowledge that dry-farmed fruits and vegetables are niche crops. Indeed, agricultural experts estimate that dry farming is practiced at less than 1 percent of California’s 77,000 farms.

Jay Lund, director of UC Davis’ Center for Watershed Sciences, is more blunt.

“Dry farming for most of the state will be a recipe for royal poverty,” he said. “The reason people don’t do as much dry farming is you don’t make enough money.”

There’s also the unpredictability: Without irrigation, crops are at the mercy of variations in seasonal rainfall. In 2014, when San Juan Bautista barely got 10 inches of rain, Leap resorted to a hybrid form of dry farming. He irrigated his winter cover crops, but his spring and summer vegetables were still produced without water.

“Usually you get people dry farming when they don’t have access to irrigated water,” said David Runsten, policy director at the Davis-based California Agricultural Water Stewardship Initiative, which aims to raise awareness about approaches to water conservation techniques.

But as Devoto and his fellow growers in western Sonoma County and other parts of an increasingly thirsty state have found out, sometimes there’s just no choice.

“If you don’t have the water,” Runsten said, “then it becomes more appealing.”