Several years ago, Nick Rajkovich bought 1,200 acres in California's Fresno County, planning to grow almonds for his family's farming business.

The ranch had a steady supply of water at the time. But that changed with the state's latest, relentless drought: Federal water deliveries over the past three years dwindled to zero.

"Now the almonds are dead," Rajkovich says; and with the land bone dry and no relief in sight, "The only thing we can farm is the sun. That's why solar is the obvious choice for us."

Rajkovich is one of many farmers in the Central Valley and elsewhere who are turning land over to solar developers, planting photovoltaic panels instead of crops.

California's punishing drought is sparking fierce debates over water allotments for agriculture, and more than 500,000 acres will lie fallow this year. At the same time, the state is fighting climate change more aggressively than ever with a new law requiring half of all electricity to come from renewable sources like solar and wind by 2030.

All of that clean energy needs real estate, and farmers have land available.

Now, almost a third of California's big solar facilities—those capable of generating one megawatt or more—stand on croplands or pastures, according to new research.

"It presents a whole suite of new questions," says Rebecca Hernandez, a Stanford University researcher who led the study published this month in the Proceedings of the National Academy of Sciences. While some installations can put spent farmland to good use, she says, others could be more disruptive, especially if they require transmission lines to be built through sensitive areas nearby, or they convert land that could still be used to grow food.

In Fresno and Kings Counties, the Westlands Solar Park sits on 24,000 acres that once produced lettuce, beans, garlic, and other crops. That land is now unfarmable, and the park's developers say its salt-contaminated grounds could eventually provide 5 gigawatts of solar energy—a quarter of the whole country's current capacity.

Aside from abundant sunshine, sites like Westlands Solar Park's can be appealing to developers because the land has already been disturbed, eliminating the kinds of endangered species concerns that cropped up on the Mojave Desert's Ivanpah project, for example. (See how a rare type of tortoise created special considerations for that plant.)

Al Solis, a real estate developer in Fresno, says he saw solar development in the Central Valley pick up after California set a target in 2011 of one-third renewable electricity by 2020. Since then, he says, projects have gotten fewer, but bigger. He expects more land in the Westlands Water District—the subject of a contentious agreement with the federal government that requires 100,000 acres to be retired from cultivation—will be offered for solar companies to purchase.

But in most cases, Solis says, a solar deal isn't necessarily a permanent switch. Instead, it can be 25- or 30-year lease that allows the farmer to reclaim the land for crops at the end of the term. (Rajkovich's land lies within the Westlands district; he says he's exploring both purchase and lease options.)

"People think that a solar facility means somehow the ground underneath it disappears," Solis says, noting that some owners of large parcels will section off some land for solar and keep the rest for farming. In those cases, "solar's not forcing them out," he says. "It's actually a benefit to keep them in agriculture on the rest of their land."

Other states, such as Georgia and North Carolina, have seen similar deals. After all, the income from a solar lease isn't affected by weather or drought; it's "financial stability that actually keeps the farm operating and keeps the land in the family," Brian O'Hara, senior vice president for strategy and government affairs at Strata Solar, which has leased land from farmers in North Carolina.

For Rajkovich, a deal with a solar company on his land will be welcome, but as an income source, it can't hold a candle to almonds. They currently sell for $4 a pound, and the potential yield is 2,000 pounds per acre, he says.

"Solar doesn't pay anywhere near that," he says, but it's the best option he has now to pay off the loans on land that might never produce another crop. "We don't think we're ever getting water back there."

The story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.