Resilience to climate change starts with water, say these UC ag researchers

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

Mitchell is a cropping systems specialist at the University of California Cooperative Extension. Its fast-absorbing soils prevent rainfall from pooling and overflowing, as is the case in many surrounding fields. “There is a risk that this water will evaporate if it stays there long enough,” he said, “and even more serious, perhaps, is that the water would not even seep at all in the field and it would just run off and eventually go into the ocean.

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

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

Along with other soil health practices, including no-till agriculture, which involves minimal soil disturbance, Mitchell’s research has shown that cover crops confer a multitude of benefits, including “increased infiltration , the cooling of the soil, the reduction of evaporation directly from the soil and the presence of water passing through the plant in what is called transpiration rather than simply being an evaporative loss of water from the soil”, did he declare.

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

Mitchell spends much of his time at UC’s West Side Research and Extension Center at Five Points, where he is one of many scientists whose work on improving farming practices goes hand in hand with conserving nature. water and resilience to climate change.

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The research facility is in a rural area of ​​western Fresno County dotted with unincorporated farm worker communities and within rumbling distance of the Super Hornets taking flight from Naval Air Station Lemoore. The facility is quite modest, consisting of a dozen low buildings surrounded by a large open sky. “We’re still kind of an outpost here, it’s not exactly a very populated area,” laughs agronomist and center director Robert Hutmacher.

Built in 1959, it is one of nine such centers in various ecosystems across the state designed to bridge the gap between academic research and industry. Research specialists study new crop varieties and farming techniques, then crop advisors help growers put them into practice. What they’re studying here is a sample of what’s grown nearby, Hutmacher said, including “cotton, sorghum, industrial hemp, barley, wheat, processing tomatoes, garlic, onions, alfalfa, pistachios, table and wine grapes, almonds, chickpeas” and a variety of cereals.

In some ways, this modest research station is on the front lines of climate change. It’s on the west side of the valley, where surface water is already scarce and the soil is full of salts that prevent plants from absorbing nutrients. Like its neighbours, this state-funded institution is likely to face looming reductions in its groundwater use under the Sustainable Groundwater Management Act.

But when it comes to water conservation, the facility also has a reputation for being a bit ahead of its time. For example, it’s one of the places where drip irrigation, now dominant in California agriculture, was pioneered in the 1970s. Back then, “it wasn’t always seen as something important or profitable,” Hutmacher said, “but with all these changes, the availability of water, the predictability of water supply, the issues of groundwater management and water management salinity…all of those things together, they kind of pushed everything towards better water conservation.

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A recent regional climate assessment led by UC Merced researchers estimates that average annual temperatures in the San Joaquin Valley have increased by one degree Fahrenheit over the past 70 years, and warming could continue another 5-8 degrees by the end of the century.

Interestingly, however, when considering the future of agriculture, it is not rising temperatures that Hutmacher is most concerned about, but water availability. From a regional perspective, Hutmacher believes agriculture will survive in the valley, but for individual growers, he understands the future is daunting. “If you’re not mobile you’re tied to 1,000 acres of land that can rarely be fed by a water district and then a few wells that somebody’s going to start restricting your use of, that’s hardware of existential crisis,” he said.

It’s one of the reasons other Five Points researchers take a close look at some of the Valley’s most important crops. “There are six acres of pistachios planted in May 2019,” nut farming adviser Mae Culumber said, pointing to a field of trees that are now bare but in a few years will be teeming with a commodity that earned California nearly $3 billion in 2020.

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

So one of Culumber’s plans is to restrict post-harvest irrigation to essentially induce early dormancy, in the hopes that this can help trees get through erratic winters while reducing their water needs. “Towards the end of the growing season, we have different times to turn off irrigation for the season,” she said. “We want to try to find practices that are viable and maintain agricultural productivity, but are as sustainable and environmentally friendly as possible.”

A few hundred yards away, George Zhuang and Karl Lund, viticultural advisors for Fresno and Madera counties, respectively, tend to two acres of vines a few inches tall. “We just planted these vines this year, so they are baby vines,” Zhuang said.

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UC Cooperative Extension viticulture advisor George Zhuang evaluates newly developed grape rootstocks for their tolerance to drought, heat and salinity.

Most of the grapes were grafted onto a few universal varieties of rootstocks widely used around the world, says Lund. So here at Five Points, in tandem with other UC research stations doing similar work, they are testing new rootstock varieties for their tolerance to heat, salinity and especially drought. .

“In Madera County, we plan to reduce our pumping by 20 percent” over the next 20 years, Lund said. “So if we don’t do something, that’s sort of the direction the industry is going…we’re just going to lose 20% of our acreage.”

He and Zhuang are convinced that by finding new varieties of hardier rootstocks, the grapes we love — and which brought California more than $4 billion in 2020 — can continue to thrive with fewer resources. “We just adapt to whatever is thrown at us,” Lund said. “You can’t outsmart mother nature, mother nature is always going to throw something new at you and you just have to readjust.”

“Human beings, we have the talent and we have the research skills to adapt to climate change or whatever challenges we face, and we can still make progress,” Zhuang agreed.

Whatever benefits these researchers find, it’s up to the producers of the Valley’s more than 8 million acres of productive farmland to embrace them.

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

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