Tamping Down on the Dust

Farm fallowing to save water can result in a host of unintended consequences, but the right kind of crop management can build in climate resilience.

DUST STORMS. Pest scourges. Diseased fungus.

As a historic drought drives water scarcity throughout the Western United States, these are some of the threats looming over hundreds of thousands of acres, experts say, if California farmland is left to dry up in coming years.

Once a standard practice in the Central Valley, dryland farming kept large swaths of the region covered in wheat, cereals, and forage grass with just precipitation. Photo of a Washington wheat field by Diana Robinson.

While the recent deluge has temporarily alleviated arid conditions, most of the state continues to be in drought, and many reservoirs — including its largest, Shasta Lake — still measure far below historical averages.

The drought has particularly dire implications for the San Joaquin Valley, the state’s agricultural heartland. The region is home to a $35-billion farming industry, which has had relatively unhindered access to water. But these days, with a relentless drought and a warming climate plaguing the West, the flow is looking less certain. Furthermore, decades of overdrawing groundwater to supplement surface supplies are finally catching up, leaving Central Valley aquifers depleted.

Enacted in 2014, California’s Sustainable Groundwater Management Act (SGMA) aims to reverse the trend by tightening restrictions on pumping, drilling, and deepening wells in order to restore underground basins. Yet those limits, coupled with deep slashes in surface water allocation, have already dried up some 752,000 acres of farmland statewide in the past year. And the situation is only expected to get worse: The Public Policy Institute of California (PPIC), a non-profit research institution, projects that by 2040, more than 500,000 acres may need to be retired to help replenish the region’s overdrawn reserves.

Left fallow, dry fields can kick up a host of dusty consequences. One season of mismanaging weeds and pests can have long-lived and wide-scale repercussions, far beyond a singular farm. Environmental hazards degrade soil and air quality, impacting public health and wildlife habitats. In addition, idle acres could seismically shift the regional landscape, leading to the potential loss of up to 85,000 jobs and $7 billion in yearly agricultural revenue.

Despite the sobering prospects, a recent PPIC study reveals strategies to temper the impacts of fallowing, including one solution that taps California’s agronomic roots to help it adapt to a drier future. Once a standard practice in the Central Valley, dryland farming kept large swaths of the region covered in wheat, cereals, and forage grass with just precipitation, until the advent of wide-spread irrigation in the early 1900s.

Economically, those crops are no match for the thirstier high-value nuts, fruits, and vegetables now common throughout the Valley. Given the daunting scale of land slated to be retired, however, researchers see low-water use agriculture as a promising alternative to keeping fields productive — one that holds tumbleweeds at bay while ultimately helping to replenish the water table.

A PRACTICE AS ANCIENT as agriculture itself, dryland farming is still prevalent in large, arid regions of Australia, Chile, and the Mediterranean, where advances in crop breeding and soil and water management have made grains and legumes more productive. And here in the United States, it’s practiced across more than half of Washington State to grow millions of acres of wheat, barley, and other cereals, as well as canola and legumes.

In the state’s southeast corner, in the long rain shadow of the Cascade Mountains, the Horse Heaven Hills average 9 inches of rainfall a year. The amount, while scant, is enough for Garrett Moon, a fifth-generation grain farmer, to grow 4,000 acres of wheat without irrigation. “Small grains are a good match for our dry climate,” he says.

Planting begins soon after the intense summer heat dissipates, with seedlings fed by late fall and winter rains. “There’s no heat stress,” Moon says, “so [the wheat] can be efficient with the water that it does get.” Abnormally dry conditions similar to California’s have cut yields by roughly 45 percent this year. “But even when things are bad, wheat always gives you something,” he adds. “That’s why it’s a staple.”

The grain’s reliability and hardiness boost its prospects as a viable crop for the San Joaquin Valley, says Caitlin Peterson, PPIC Water Policy Center’s associate director and research fellow, who lead the recent study. Although rainfall varies within the roughly 27,000-square mile region, in most areas, it’s enough to keep winter fields covered in wheat, other cereals, and forage grass.

Farming, however, requires balancing agronomics and economics, and replacing the region’s lucrative specialty crops with low-yield, low-value replacements complicates the equation. Unlike Washington, farmland ownership in California is much more fragmented and smaller in scale; given operating costs and commodity prices, Peterson estimates that for Central Valley growers to break even, they would need a minimum yield of 5 tons of winter wheat forage per acre. Without irrigation, she adds, many areas would come up short.

Yet supplementing dryland farming with minimal irrigation — a method Peterson refers to as water-limited cropping — can dramatically up the odds. Computer modeling shows that just one 4-inch application can bump yields towards the 5-ton mark, she says. “And with eight inches, you have [even] better luck,” with averages pushing as high as 7 tons.

Even in the water-strapped valley, “these are minuscule amounts compared to what you would typically put on a fully irrigated [specialty] crop,” Peterson says. Tomatoes, for example, require 24 inches of water per season; nut trees and alfalfa can guzzle as much 42 inches. And faced with decreasing supplies, farmers may have little choice but to maximize their remaining allocations.

For land that would otherwise sit fallow, the relative sprinkle can reap a range of public and private benefits. In addition to minimizing environmental hazards and providing surrogate habitats for birds and other wildlife, keeping fields productive helps maintain soil health and improve water infiltration — leaving them less vulnerable to erosion, and better able to store moisture and accommodate other crops in wetter years.

Winter cereals also give growers options for adapting to swings in annual precipitation. In drier conditions, they can be harvested early as forage or used to graze livestock, while in flood years, they can be sacrificed as a cover crop and tilled to recharge the soil with nutrients. And given the increasing volatility of climate conditions, “building flexibility into farm operations,” says Peterson, “is really the key to resilience.”

GLOBALLY, WHEAT PRODUCTION is second only to corn. Each variety, however, tends to be highly local, and bred for maximum yield given the soil, rainfall, and economics of a specific region. In Washington alone, agronomists at the state’s University Extension program trial more than 90 low-rainfall strains every year across 40 different locations, and also promote advances in deep seeding technology and low-impact tillage. Otherwise, notes Moon, “with the climate stress we have here,” dryland grains not suited to a specific region “can fall flat on their faces.”

Currently, the San Joaquin Valley produces about 117,000 acres of wheat — mostly on irrigated fields. “The varieties in California weren’t really developed with [water-limited] cropping in mind,” says Mark Lundy, assistant professor of cooperative extension at UC Davis’ Department of Plant Sciences and co-author of the PPIC report.. More research — both genetic and agronomic — is needed, he adds, to tailor varieties to the region’s range of water needs and its changing environment.

Planting vast expanses of grain in the Valley, says Peterson, “is a big mindset shift — as well as a system transformation — from the high-input, high-output crops we’re used to.” For growers, the list of bottom-line considerations runs long, from the practicality of irrigating fields with minimal amounts of water to California’s current insurance regulations, which limit coverage of strictly dryland crops, or prohibit livestock from grazing grain and forage.

Moon also notes that a large-scale switch to low- or no-irrigation agriculture comes with unavoidable economic impacts. Taxation on dryland farms can be as little as a third of irrigated ones, he says, and those crops will be producing far less revenue with a fraction of the labor. He recalls that in the 1990s, the federal Conservation Reserve Program (CRP) paid Washington growers to convert marginal fields into native pastureland. “The owners didn’t need labor or services, new equipment, or inputs,” he adds. “It gutted the communities those farms supported.”

Yet with the added squeeze of SGMA on California’s water supply, the inevitable risks posed by large-scale fallowing leave few options, says Peterson. “We’re not talking about planting dryland wheat instead of almonds. We’re talking about planting dryland wheat instead of nothing, where there’s really no other option.”

Peterson acknowledges that in some areas, greater water availability may support slightly thirstier crops such as oilseeds or legumes, while more marginal land might better accommodate pastures or a restored wildlife habitat. And drought-resistant specialty crops such as agave and jujubes have the potential to create a niche and value-added market.

Nevertheless, she adds, farmers need financial incentives and policy support — water credits through grants and tax benefits, risk reduction through robust crop insurance and cooperative land management initiatives and streamlined regulation and permitting — to enable profits and the public benefits of keeping farmland productive.

Either way, the changes in the landscape are inevitable, Peterson says. “With the amount of water we have and our need to keep our basins balanced, we’re going to end up with a smaller [agricultural] footprint.” But the stark realities of the potential impacts of large-scale fallowing present an opportunity, she adds, to reimagine the Valley’s water use and crop portfolio.

“We can produce amazing things in our region with little irrigation,” she says. “So I don’t think this is a decline. I think it’s an inflection point.”

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