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Climate change resilience begins with water, say these UC ag researchers

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Kerry Klein
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The six acres of pistachio trees behind University of California Cooperative Extension nut crop advisor Mae Culumber are part of a study evaluatinng new techniques for tree training and deficit irrigation.

They’re optimistic that increasing agriculture's resilience to a changing climate can also improve its relationship with the environment.

On the rare days it rains in western Fresno County, the soils in Jeffrey Mitchell’s experimental fields soak up the water like a sponge. “The water disappears within less than a minute, even for four inches of water,” he said, laughing.

Mitchell is a cropping systems specialist with the University of California Cooperative Extension. His quick-absorbing soils keep the rainfall from pooling and overflowing, like it does in many surrounding fields. “There’s the risk of that water evaporating if it stays there long enough,” he said, “and even more serious, perhaps, is that the water wouldn’t even infiltrate into the field at all and it would just simply run off and go out eventually into the ocean.”

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Kerry Klein
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UC cropping system specialist Jeffrey Mitchell’s research showing the benefits of cover crops and reduced-disturbance farming practices have earned him two awards from a national organization that promotes no-till farming.

Mitchell’s water-efficient soils are the product of more than two decades of research into regenerative agricultural practices. Since the late 1990s, he’s rotated eight acres of farmland through tomatoes, cotton, chickpeas and melons, all while planting cover crops such as grains and grasses between the rows of cash crops.

Along with other soil health practices—including no-till farming, which involves minimal soil disturbance—Mitchell’s research has shown that cover crops impart a wealth of benefits, including “increased infiltration, cooling the soil, reducing evaporation directly from soil, and having water actually go through the plant in what’s called transpiration rather than just being a loss through soil-water evaporation,” he said.

At some soil depths, cover crops can even boost carbon storage, all without a significant increase in water demand. Mitchell’s research has earned him two awards from a national no-till farming association, the most recent of which as 2020 Innovative Educator of the Year.

Mitchell spends much of his time at the UC’s West Side Research and Extension Center in Five Points, where he’s one of many scientists whose work on improving ag practices runs parallel with water conservation and resilience in the face of a changing climate.

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Kerry Klein
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The research center lies in a rural area of western Fresno County scattered with unincorporated farmworker communities and within rumbling distance of the Super Hornets taking flight from Naval Air Station Lemoore. The facility is pretty unassuming, comprised of a dozen or so low-lying buildings surrounded by big open sky. “We are still sort of an outpost out here, it's not exactly a highly populated area,” laughed agronomist and center director Robert Hutmacher.

Built in 1959, it’s one of nine such centers in various ecosystems throughout the state designed to bridge the gap between academic research and the industry. Research specialists study new crop varieties and farming techniques, then crop advisors help growers bring them into practice. What they study here is a cross-section of what’s grown nearby, said Hutmacher, including “cotton, sorghum, industrial hemp, barley, wheat, processing tomatoes, garlic, onions, alfalfa, pistachio trees, table grapes and wine grapes, almonds, garbanzo beans,” and a variety of grains.

In some respects, this modest research station is on the front lines of climate change. It’s on the Valley’s west side, where surface water is already scarce and the soil is full of salts that prevent plants from taking in nutrients. Like its neighbors, this publicly funded institution is likely to face cuts to its groundwater usage looming under the Sustainable Groundwater Management Act.

But when it comes to water conservation, the facility also has a history of being a little ahead of its time. For instance, it’s one of the places where drip irrigation, now dominant in California agriculture, was pioneered in the 1970s. At the time, “It was not always perceived as something that was important or cost effective,” said Hutmacher, “but with all these changes, water availability, predictability of water supplies, problems with groundwater management and salinity management…all of those things together just sort of pushed everything toward improved water conservation.”

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Kerry Klein
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A recent regional climate assessment helmed by researchers at UC Merced estimates that average annual temperatures in the San Joaquin Valley have risen one degree Fahrenheit in the last 70 years, and warming could continue by another 5 to 8 degrees by the end of the century.

Interestingly, however, when contemplating the future of ag, it’s not rising temperatures that concern Hutmacher the most, but water availability. From a regional perspective, Hutmacher believes ag will survive in the Valley—but for individual growers, he understands the future is scary. “If you're not mobile, you're tied to 1,000 acres of land that infrequently can be supplied by a water district and then by a couple of wells that someone is going to start restricting your use of, it is existential crisis material,” he said.

That’s one reason other researchers in Five Points are taking a close look at some of the Valley’s most important crops. “There's six acres of pistachios planted in May of 2019,” said nut crop advisor Mae Culumber, gesturing to a field of trees that are bare now but in just a few years will be overflowing with a commodity that earned California nearly $3 billion in 2020.

Although winters on average are getting warmer, temperatures still swing erratically, explains Culumber, and trees that have become accustomed to milder winters can be caught unawares by sudden cold snaps. “They're going to be more susceptible to potentially getting damaged and maybe even sometimes killed from that extreme change,” she said.

So one of Culumber’s projects involves restricting irrigation after harvest in order to essentially induce early dormancy, in the hopes that it can help the trees weather erratic winters while reducing their water requirements. “Toward the end of the growing season, we have different timing of when we're cutting off the irrigation for the season,” she said. “We want to try to find practices that are viable and maintain the productivity for agriculture but that are also sustainable and environmentally conscious as possible.”

Just a few hundred feet away, George Zhuang and Karl Lund, viticulture advisors to Fresno and Madera Counties, respectively, tend to two acres of grapevines just a few inches tall. “We just planted those vines this year, so they are baby vines,” said Zhuang.

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Kerry Klein
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UC Cooperative Extension viticulture advisor George Zhuang is evaluating newly developed grape rootstocks for tolerance to drought, heat and salinity.

Most grapes have been grafted onto a few universal varieties of rootstocks that are in widespread use around the world, says Lund. So here in Five Points—in tandem with other UC research stations doing similar work—they’re testing new varieties of rootstocks for tolerance to heat, salinity, and especially drought.

“In Madera County, we're looking at cutting 20 percent of our pumping” over the next 20 years, Lund said. “So if we don't do anything, that's sort of the way the industry is headed...we're just going to drop 20 percent of our acreage.”

He and Zhuang are confident that by finding new varieties of hardier rootstocks, the grapes we love—and that raked in more than $4 billion for California in 2020—can continue to flourish with fewer resources. “We're just adapting to whatever is being thrown at us,” said Lund. “You can't outsmart mother nature, mother nature's going to always throw something new at you and you just have to re-adapt.”

“Human beings, we have the talent and we have the research skills to adapt to the climate change or whatever challenges we have, and we'll still be able to make some progress,” agreed Zhuang.

Whatever benefits these researchers uncover, it’s up to growers in more than 8 million acres of productive farmland in the Valley to adopt them.

Jeff Mitchell knows that’s no small task, but he’s optimistic big change can happen. He’s seen it. In a conference room in Five Points, he points to a wall of portraits of local growers. “These are all farmers who have done amazing things by changing the paradigm of their production system here,” he said. He hopes more will do the same in the future.

Kerry Klein is an award-winning reporter whose coverage of public health, air pollution, drinking water access and wildfires in the San Joaquin Valley has been featured on NPR, KQED, Science Friday and Kaiser Health News. Her work has earned numerous regional Edward R. Murrow and Golden Mike Awards and has been recognized by the Association of Health Care Journalists and Society of Environmental Journalists. Her podcast Escape From Mammoth Pool was named a podcast “listeners couldn’t get enough of in 2021” by the radio aggregator NPR One.