California Has Farmers Growing Weeds. Why? To Capture Carbon

4 min
Jose Robles spreads mulch and compost under his almond trees with help from a California climate change grant. (Lauren Sommer/KQED)

California’s climate change efforts can be spotted all over the Bay Area in the growing number of electric cars and solar panels. But now, California is enlisting people from a more conservative part of the state -- even if they don’t think climate change is much of a concern.

California’s farmers are receiving millions of dollars to pull carbon out of the atmosphere, something the state says is crucial for meeting its ambitious climate goals.

The state is paying them to grow plants, which absorb carbon and help move it into the soil where it can be stored long-term. That makes California home to some of the first official “carbon farmers” in the country.

For some, like almond grower Jose Robles of Modesto, climate change was an afterthought, if that. That’s something they talk about in Sacramento, he says, not where he lives and works.

But in December, the ground under Robles' almond trees was a carpet of green, full of mustard plant and clover. It’s not a common sight in the Central Valley. After all, most farmers hate weeds.

“Everybody wants to have the orchards nice and clean,” Robles says, laughing.

His neighbors really don’t understand it.

“I’ve heard them say, ‘We’re in the business of growing almonds, not in the business of growing weeds,’” he says, laughing.

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Adapting to Drought

Robles got the idea a few years ago, during California’s severe drought, when he had to cut back on watering his trees.

“We had no water,” he says. “It made us look at things different.”

Robles knew that richer earth with more microorganisms holds moisture longer, but there wasn’t a lot of organic matter in his orchard to build the soil up. Like most farmers, he sprayed herbicides to kill weeds.

A field at Russell Ranch at UC Davis, where carbon storage techniques are studied. (Lauren Sommer/KQED)

So he decided to grow organic matter specifically to feed his soil. He planted species that most people commonly see as weeds, but when sown on purpose, are known as a "cover crop."

Once they get a few feet tall, he mows them and lets them decompose, along with some extra compost and mulch. A $21,000 grant from California helps cover his extra costs and labor.

It can be tricky, because almonds are harvested from the ground after they’re shaken off the trees. Having mulch or weed remnants on the ground would interfere with that, so Robles has to make sure the organic matter breaks down before harvest begins.

He’s already seen a difference.

“The trees, they don’t stress as much, because they hold the moisture a lot longer,” Robles says.

Absorbing Carbon Emissions

Though climate change didn’t really factor into Robles' decision, his grant comes from a program designed to be part of the state’s climate change strategy. California's Healthy Soils initiative is now in its third year.

Farms and forests could absorb as much as 20 percent of California's current level of emissions, says a state report.

“I think there’s great potential for agriculture to play a really important role,” says Kate Scow, professor of soil microbial ecology at UC Davis, of the state's climate goals. She’s standing in a large wheat field at Russell Ranch, seven miles west of the campus, where the university plants crops to study sustainable agriculture.

“Soil is alive,” she says. “There’s farmers that know that.”

To show me, Scow starts enthusiastically digging in the dirt.

“All right, see, we’re starting to hit the mineral soil.”

This is where the carbon is stored. Plants soak up the carbon dioxide in the air to build their leaves and stems. Their roots pump carbon down into the earth. Then, when the plant dies, its organic matter gets broken down by microbes and fungi. That’s how carbon from the air gets into the soil.

“The deeper you can get it in the soil, especially below the plow layer, the more stable and secure it’s going to be,” she says.

That’s key to prevent the carbon from being released back into the air, and is how agriculture could play a part in the state’s climate effort.

“We have very ambitious climate goals, and without natural and working lands, California simply won’t get there,” says Jeanne Merrill, with the California Climate & Agriculture Network, a coalition of ag groups working on climate policy.

Before leaving office, Gov. Jerry Brown set a goal for California to be carbon neutral by 2045. That will likely mean not just reducing carbon emissions from cars and buildings, but absorbing carbon already in the air.

Merrill says California’s farmers are already on the frontlines of facing climate impacts, like more extreme weather.

“Some are willing to say that it’s climate change,” she says. “Others are unsure. But I think many know that things are changing and they need different tools.”

Farmers are interested in the climate programs, Merrill says, if only because it can help them weather extended droughts.

Hundreds have signed up. But state climate officials say the Healthy Soils program needs to be five times larger. That means the state Legislature will have to boost its $15 million budget, and Gov. Gavin Newsom has requested more money for the program. (Update May 9, 2019:  In the May revise of the state budget, Newsom has proposed $28 million for Healthy Soils, an increase of $10 million over his original proposal.)

Merrill says that would send a signal that California’s climate efforts will take the entire state, not just coastal cities.

“It’s bridging that coastal-Valley divide,” she says. “It’s saying that we need that Valley base pretty significantly.”

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