Agriculture

In the parking lot behind a grocery store in Portland, Ore., last September, several hundred tomato aficionados gathered on a sunny, breezy day for Tomato Fest. While many attendees devoured slices of tomato quiche and admired garlands of tomatoes with curiously pointed ends, I beelined to a yellow-tented booth hosted by Oregon State University. Agricultural researcher Matt Davis was handing out samples of experimental tomatoes.

I took four small plastic bags, each labeled with a cryptic set of letters and numbers and containing a thick slice of a yellow tomato. Scanning a QR code with my phone led me to an online survey with questions about each tomato’s balance of acidity and sweetness, texture and overall flavor. As I chewed on the slice from the bag marked “d86,” I noted the firm, almost meaty texture. Lacking the wateriness of a typical supermarket tomato, it would hold up beautifully in a salad or on a burger, I thought. And most importantly, it was tasty.

These tomatoes for sale at a farmers market in Portland, Ore., were dry-farmed. The practice saves on water and produces more flavorful fruits and vegetables, advocates say.K. Kornei

I learned later that this tomato had been dry-farmed, a form of agriculture that doesn’t require irrigation. Dry farming has roots stretching back millennia. But in the western United States, the practice largely fell out of widespread use in the 20th century.

Today, however, farmers in the West are once again experimenting with dry farming as they grapple with water shortages, which are being exacerbated by rising temperatures and more frequent and intense droughts linked to climate change.

Finding a more sustainable way to grow food in a thirsty state like California, for example, where agriculture accounts for roughly 80 percent of water usage and where a third of U.S. vegetables are grown, is a top priority. Dry farming won’t solve all of agriculture’s woes, but it offers a way forward, particularly for smaller-scale producers, while drawing less on a scarce natural resource. And even though the practice isn’t without limitations — dry-farmed produce tends to be physically smaller, and harvests are less bountiful overall — its benefits extend beyond water savings: Dry farming can also yield longer-lasting and better-tasting produce.

How does dry farming work?

It’s a common misconception that dry farming means growing plants without water. “Nothing grows without water,” says Amy Garrett, president of the nonprofit Dry Farming Institute in Corvallis, Ore. Instead, dry-farmed plants take up moisture stored in the ground rather than sprinkled from above.

Dry farming is possible in states throughout the West. What’s needed is a wet rainy season, when rainwater infiltrates the soil, followed by a dry growing season, when plant roots pull in that moisture as needed. A wide variety of fruits and vegetables — including tomatoes, potatoes, squash, corn and even watermelons — can be dry-farmed. Dry farming is distinct from rain-fed agriculture, when crops grow during a wet season without the aid of irrigation.

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For dry farming to work, a couple elements are essential. “You need to be in a place where there’s sufficient rainfall to create moisture in the soil,” says David Runsten, water policy director at the Community Alliance with Family Farmers in Davis, Calif. Sites must generally receive more than 50 centimeters of annual precipitation — in 2022, that was true in 26 of California’s 58 counties, for example — and the soil must be composed of fine grains that help retain that water over time.

Beyond that, farmers employ a range of techniques to help crops get all the moisture they need. Those methods include planting earlier in the season than usual to take advantage of soil moisture stored up from winter rains and spacing plants more widely to give roots more room to search for water. Farmers can also plant young seedlings in furrows to minimize the drying effects of the wind and lay down an insulating layer of mulch — often leaves, wood chips or straw — on top of the soil.

Dry farming is standard practice in many places around the world, from olive groves in the Mediterranean to melon fields in Botswana to vineyards in Chile. In the American West, dry farming has a long history stretching back thousands of years among Indigenous peoples.

“Dry farming is just farming — it’s our way of life,” says Michael Kotutwa Johnson, an Indigenous resiliency specialist at the University of Arizona in Tucson. He’s also a member of the Hopi Tribe and dry-farms corn, lima beans and other crops. He learned the practice from his grandfather.

The intimate knowledge of the natural world that dry farming requires aligns with the Hopi community’s values and spiritual beliefs, he says. “You get to really learn what the environment gives you, and you learn to reciprocate.” A relationship develops between the cropping system and the farmer, he says. “It’s a beautiful thing, and it’s something that needs to be cherished.”

Children explore a field of dry-farmed corn on Hopi land in Arizona. Dry farming requires that crops be spaced farther apart than on an irrigated farm so that the plants have enough room to access all of the soil moisture they need.M.K. Johnson

As non-Indigenous people started arriving in the West, they too began to dry-farm. But by the 20th century, many commercial farmers started relying on irrigation to capture growing markets. Having water on demand gave farmers more control and allowed them to boost production, says Jay Lund, vice director of the Center for Watershed Sciences at the University of California, Davis. “They could have a lot more reliable crop yields, and much higher crop yields.”

But today, irrigation water in many parts of the West is in short supply. In places like California’s San Joaquin Valley — the state’s largest agricultural region — water is pumped up from deep aquifers and often transported through canals and pipes before being deposited on crops. Researchers estimate that more than a quarter of irrigation water can be lost during transport due to evaporation and leaks. An even bigger problem in this region is that water is being extracted from the ground at a faster rate than it’s being replenished. “There just isn’t sufficient water for the amount of farmland that’s been planted,” Runsten says.

And access to irrigation is already being curtailed. Farmers in California and other states in the West are experiencing water shortages and have at times been entirely cut off from irrigation (SN: 9/25/21, p. 16).

That’s not likely to change in the future, Runsten says. To meet the goals of California’s 2014 Sustainable Groundwater Management Act, for instance, more than 200,000 hectares of irrigated farmland in the San Joaquin Valley — roughly 10 percent — will need to be taken out of irrigated production by 2040. Dry-farming speciality crops like agave or jujube, an Asian fruit similar to a date, could be an economically attractive alternative for the land, according to a 2022 report by the nonprofit Public Policy Institute of California.

Dry farming has pros and cons

Catherine Nguyen, who farms on a little less than half a hectare of leased land outside of Portland, Ore., in the Willamette Valley, has been dry-farming for two years. Nguyen — whose customers include farmers market shoppers, members of her community supported agriculture, or CSA, program and small restaurants — was drawn to the practice in part out of curiosity. “I love experimentation and with the changing climate and cost of water, it seemed like something to learn more about,” she says. A portion of her property also lacks access to irrigation, so dry farming made it possible to use land that would otherwise remain fallow.

Potatoes were the first crop Nguyen dry-farmed. Beyond saving roughly 7,500 liters of water, Nguyen and her small crew discovered other benefits. There was no need for sprinklers, drip tape, hosing or any other irrigation equipment. That meant Nguyen’s farm could cut down on a lot of plastic equipment intended to last for just one or two growing seasons. “Not only is our water usage down, but so is our plastic usage,” Nguyen says. That lighter environmental touch is important to Nguyen, who uses farming methods that promote healthy soil ecosystems, including minimal tillage and cover cropping, which involves growing plants specifically to improve the soil rather than for a harvest (SN Online: 4/12/22).

Last year, Nguyen dry-farmed delicata squash, corn, tomatoes, potatoes and beans. Nguyen noticed that her dry-farmed plots contained only about a fifth of the weeds that grow in her irrigated plots. That’s another known advantage of dry farming, Garrett says. Irrigation creates conditions for weed growth: Dispensing water through above­ground sprinklers causes moisture to pool near the surface, precisely where weeds wait for water, she says. “There is a weed seed bank in the top few inches of soil.”

Not having to pull up as many weeds or apply herbicides can translate into labor savings. Coupled with not having to manage irrigation infrastructure, dry farming can streamline a growing operation, Garrett says. “There’s a lot less to do.” Labor accounts for more than a quarter of total production costs for U.S. fruit and vegetable farmers.

Another benefit is that the produce contains less water and therefore tends to store better. In 2016 and 2017, Alex Stone, a horticulturist at Oregon State University, and her student Jennifer Wetzel grew different varieties of winter squash at the university’s research farm in Corvallis. The pair irrigated some vegetable plots and dry-farmed others. After harvesting the squash and leaving them in storage for four months, Stone and Wetzel found that about 1,000 of the roughly 1,250 dry-farmed winter squash, or about 80 percent, were still marketable. But only about 600 of the roughly 1,150 irrigated winter squash, or about 50 percent, were marketable.

Longer-lasting produce is a boon for small-scale fruit and vegetable growers, Garrett says. Winter is often a slow time sales-wise because there’s not much ripening. Selling stored crops in winter is one way that these farmers can earn an income during that lull. “If winter squash is storing months longer, that makes a huge impact for our local growers,” she says. Produce that lasts longer also means less food waste, both in farmers’ storage bins and in shoppers’ refrigerators and pantries.

Dry farming does have its downsides, however. The practice tends to produce smaller fruits and vegetables. That’s a natural outcome of withholding irrigation, Lund says. “The plant has less water to feed the growth of the fruit.” And growers, to say nothing of shoppers, can be wary of diminutively sized produce. That’s true among farmers in Oregon, Stone says. “They want a big, red tomato.”

Overall yields also tend to be lower. Not only does a dry-farmed plant produce fewer fruits or vegetables, but it also needs more space than its irrigated brethren so that its root system can spread out in search of water. Dry-farmed tomatoes, for instance, are typically planted almost two meters apart in rows separated by about two meters. Irrigated tomatoes can grow much closer together, about 60 centimeters apart, with rows separated by a meter or so.

Stone and Wetzel found that yields of irrigated winter squash at Oregon State’s research farm averaged 35.7 metric tons per hectare in 2016 and 32.2 metric tons in 2017. Dry-farmed squash yields were only 37 to 76 percent as much.

Diminished harvests can be a challenge. “With land access already being one of the biggest obstacles to farming, sometimes it’s hard for me to justify dry farming,” Nguyen says. Last year, she dry-farmed on only about a tenth of her property. “I do have to consider yield per square foot when deciding how much land to dry-farm,” she says.

Smaller harvests can translate to more expensive produce. “You don’t have the economies of scale,” Lund says. “Your costs are much higher per unit of production.” Dry-farmed tomatoes, for instance, typically sell for $4–$6 per pound and are primarily found at farmers markets and specialty grocery stores. That’s compared with $2–$3 per pound for traditional supermarket tomatoes grown with irrigation.

Dry-farmed produce may never become truly mainstream, Johnson says. “I don’t see us moving in that direction as long as we still have a market system that’s based on efficiency and quantity.” But many dry farming experts argue that paying more for dry-farmed produce is an investment in the future. And, they point out, dry-farmed produce tastes better.

All of these melons were grown in dry farming experiments at Oregon State University’s Vegetable Research Farm. Melons are well-suited to dry farming because they originated in arid locations.A. Garrett

How does dry farming affect flavor?

In California’s Napa Valley, there’s nary an irrigation hose snaking through Dominus Estate’s roughly 55-hectare Napanook Vineyard. Every last one of the more than 100,000 cabernet sauvignon, cabernet franc and petit verdot grapevines planted there is dry-farmed.

The water savings are tremendous, says Tod Mostero, Dominus Estate’s director of viticulture and winemaking. A single irrigated grapevine is typically irrigated with nearly 40 liters of water several times or more over the growing season, he says. For a vineyard the size of Napanook, that translates to nearly 4 million liters, or about a million gallons, for just one watering, Mostero says. In drought-prone California, that’s not sustainable, he says. “Pumping millions of gallons of water out of the soil is not something that we can continue to do.”

Beyond the water savings, there’s another reason Napanook Vineyard is dry-farmed, Mostero says. The practice produces the best wines, he contends. When grapevines are dry-farmed, the unique flavors of a wine associated with a place, and even a vintage, often shine through. Grapevines can send roots up to six meters deep in search of moisture. As those roots pass through layers of soil and rock, they absorb a complex set of minerals unique to that location, Mostero says. “You really find the terroir, the subtle differences between different areas.” For that very reason, some wine-growing regions, in parts of Europe for example, forbid vineyards from irrigating wine grapes.

Oenophiles aren’t the only ones swearing by the superior flavors of dry-farmed fruits and vegetables. Laurence Jossel, the chef-owner of Nopa, a restaurant in San Francisco that specializes in wood-fired cuisine, sources dry-farmed tomatoes from local farms. Tomatoes that are bloated with water taste “boring,” Jossel maintains. “The acid is gone, and the sweetness is gone.” He uses dry-farmed tomatoes in everything from soups to flatbreads. Sometimes they’re the star ingredient: A salad of chopped tomatoes topped with a bit of feta or mozzarella is one of Nopa’s summer offerings. “The tomato itself is just amazing,” he says.

What’s the future of dry farming?

Despite the environmental benefits of dry farming, some farmers remain wary. Stone has found that growers in Oregon are often cautious about the practice, even when it comes to cultivating varieties that sell well elsewhere. A case in point is Early Girl tomatoes, which are extensively dry-farmed in California and available at both California supermarkets and farmers markets.

“They just see them as elite, expensive, small tomatoes,” Stone says.

To explore the economic viability of dry farming, Stone is leading farming trials of dry-farmed crops to determine which varieties are most suited to commercial production. In recent years, she and colleagues have focused on tomatoes, which, after potatoes, are the most commonly consumed vegetable in the United States. (Technically a fruit, tomatoes are considered a vegetable for nutritional and culinary purposes by the U.S. Department of Agriculture.)

Stone’s team at Oregon State has grown hundreds of types of tomatoes. By recording yields, susceptibility to common diseases like blossom-end rot, and the size, firmness and flavor of the tomatoes, the researchers have started to home in on varieties that thrive — and taste good — when the irrigation is turned off. The first yellow tomato I sampled at Tomato Fest is one of the researchers’ leading contenders.

Planting tomato seedlings in furrows, as shown on this dry-farmed plot in California, helps prevent the wind from wicking away precious moisture.Carolyn Lagattuta/UC Santa Cruz

Dry farming offers one way forward as water resources become more unpredictable in the future. But it’s not a one-size-fits-all panacea for climate change, researchers admit. In some cases, crops that once thrived without irrigation may no longer do well at some point in the future.

“As summers become hotter and drier, crops will require even more water as they will lose more water [through evapotranspiration], making dry farming riskier,” Stone says.

Some farmers may have to swap one type of crop for another that’s more suited to even drier conditions. Fruit trees with particularly long, deep roots are good bets, Garrett says, as are species like melons that originally evolved in arid locales.

Whatever the future holds, being adaptable will be key. Farmers must be prepared to respond to changing conditions, Johnson says, but must also allow nature to lead. After all, that’s worked for his community for thousands of years.

“We raise corn to fit the environment,” he says. “We do not manipulate the environment to fit the corn.” More

No matter how you slice it, climate change will alter what we eat in the future. Today, just 13 crops provide 80 percent of people’s energy intake worldwide, and about half of our calories come from wheat, maize and rice. Yet some of these crops may not grow well in the higher temperatures, unpredictable rainfall and extreme weather events caused by climate change. Already, drought, heat waves and flash floods are damaging crops around the world.

“We must diversify our food basket,” says Festo Massawe. He’s executive director of Future Food Beacon Malaysia, a group at the University of Nottingham Malaysia campus in Semenyih that studies the impact of climate change on food security.

That goes beyond what we eat to how we grow it. The trick will be investing in every possible solution: breeding crops so they’re more climate resilient, genetically engineering foods in the lab and studying crops that we just don’t know enough about, says ecologist Samuel Pironon of the Royal Botanic Gardens, Kew in London. To feed a growing population in a rapidly changing world, food scientists are exploring many possible avenues, while thinking about how to be environmentally friendly.

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Consumer preferences are part of the equation as well. “It does have to be that right combination of: It looks good, it tastes good and it’s the right price point,” says Halley Froehlich, an aquaculture and fisheries scientist at the University of California, Santa Barbara.

Here are six foods that could check all those boxes and feature more prominently on menus and grocery shelves in the future.

1. Millet

SZJPHOTO/MOMENT/GETTY IMAGES

Source of: Carbohydrates, protein, minerals (potassium, phosphorus and magnesium)Uses: Whole grain; gluten-free flour, pasta, chips, beer

The United Nations has declared 2023 the International Year of Millets (a handful of varieties exist). Quinoa earned the same honor in 2013, and its sales skyrocketed. First cultivated in Asia some 10,000 years ago, millet is a staple grain in parts of Asia and Africa. Compared with wheat, maize and rice, millet is much more climate resilient; the crop needs little water and thrives in warmer, drier environments. Some more good news: Millet is one of many ancient grains — including teff, amaranth and sorghum — that are similarly sustainable and resilient (not to mention capable of being turned into beer).

2. Bambara groundnut

PONSULAK/ISTOCK/GETTY IMAGES PLUS

Source of: Protein, fiber, minerals (potassium, magnesium and iron)Uses: Roasted or boiled; gluten-free flour; dairy-free milk

You’ve heard of almond milk and soy milk. The next alternative at your coffee shop could be made from Bambara groundnuts, a drought-tolerant legume native to sub-Saharan Africa. Like other legumes, the Bambara groundnut is packed with protein. And bacteria on the plant convert atmospheric nitrogen into ammonia so the groundnut grows well in nutrient-poor soil without chemical fertilizers. A better understanding of the plant, says Festo Massawe of Future Food Beacon Malaysia, could pave the way for breeding programs to help the Bambara groundnut become as popular as the soybean, a legume that produces high yields but is less drought tolerant.

3. Mussels

MATT MACRO/EYEEM/GETTY IMAGES

Source of: Protein, omega-3, vitamin B12, minerals (iron, manganese and zinc)Uses: Steamed; added to pasta dishes, stews, soups

A delicious mussel linguine might someday become a weeknight regular on the family menu. Mussels and other bivalves, including oysters, clams and scallops, could make up about 40 percent of seafood by 2050, according to a 2020 report in Nature. With no need to be watered or fertilized, bivalve farms are prime for scaling up, which would lower prices for consumers. All bivalves have merit, but Halley Froehlich of UC Santa Barbara singles out mussels as “super hardy,” “super nutritious” and underhyped. One downside: Shell-forming creatures are threatened as rising carbon levels boost ocean acidification. Kelp might be able to help.

4. Kelp

MOAIMAGE/MOMENT/GETTY IMAGES

Source of: Vitamins, minerals (iodine, calcium and iron), antioxidantsUses: Salads, smoothies, salsa, pickles, noodles and chips; also found in toothpaste, shampoo and biofuels

Kelp has a few cool climate-friendly tricks. For one, by taking in carbon dioxide during photosynthesis, it can lower the acidity of its watery surroundings. Farmers in Maine and Alaska grow kelp and bivalves together so that the shelled critters can benefit from the less acidic water. Kelp also sequesters carbon, like underwater trees. That means growing and eating more kelp could be good for the environment. While kelp and other seaweeds have been widely consumed in Asia for thousands of years, they’re still an acquired taste in many Western countries.

5. Enset

MIKE GOLDWATER/ALAMY STOCK PHOTO

Source of: Carbohydrates, calcium, potassium and zincUses: Porridge or bread; also used to make rope, plates and building materials

The drought-tolerant enset, cultivated in Ethiopia, is nicknamed the “false banana” because the plant resembles a banana tree, though its fruit is inedible. It’s also called “the tree against hunger” because its starchy stems can be harvested at any time of year, making it a reliable buffer food crop during dry periods. A 2021 report in Environmental Research Letters suggests that the enset’s range could be expanded to other parts of Africa, and possibly beyond. The processing required to make enset edible is complex, says study author James Borrell of the Royal Botanic Gardens, Kew. So any expansion would have to be led by the communities who hold that Indigenous knowledge.

6. Cassava

ILTONROGERIO/ISTOCK/GETTY IMAGES PLUS

Source of: Carbohydrates, potassium, vitamin CUses: Whole cooked root; gluten-free flour; tapioca pearls in bubble tea

Cassava, a starchy root vegetable from South America, checks the boxes for climate resilience, sustainability and nutrition. Now grown in over 100 countries, cassava can withstand temperatures of up to 40° Celsius and is salt and drought tolerant. An added plus: Higher atmospheric CO2 levels enhance the plant’s tolerance to stress and can lead to higher yields. Raw cassava can contain toxic levels of cyanide, but the chemical can be removed by peeling, soaking and cooking the root. More

With soils rich for cultivation, most land in the Midwestern United States has been converted from tallgrass prairie to agricultural fields. Less than 0.1 percent of the original prairie remains.

This shift over the last 160 years has resulted in staggering — and unsustainable — soil erosion rates for the region, researchers report in the March Earth’s Future. The erosion is estimated to be double the rate that the U.S. Department of Agriculture says is sustainable. If it continues unabated, it could significantly limit future crop production, the scientists say.

In the new study, the team focused on erosional escarpments — tiny cliffs formed through erosion — lying at boundaries between prairie and agricultural fields (SN: 1/20/96). “These rare prairie remnants that are scattered across the Midwest are sort of a preservation of the pre-European-American settlement land surface,” says Isaac Larsen, a geologist at the University of Massachusetts Amherst.

At 20 sites in nine Midwestern states, with most sites located in Iowa, Larsen and colleagues used a specialized GPS system to survey the altitude of the prairie and farm fields. That GPS system “tells you where you are within about a centimeter on Earth’s surface,” Larsen says. This enables the researchers to detect even small differences between the height of the prairie and the farmland.

At each site, the researchers took these measurements at 10 or more spots. The team then measured erosion by comparing the elevation differences of the farmed and prairie land. The researchers found that the agricultural fields were 0.37 meters below the prairie areas, on average.

Geologist Isaac Larsen stands at an erosional escarpment, a meeting point of farmland and prairie, in Stinson Prairie, Iowa. Studying these escarpments shows there’s been a startling amount of erosion in the U.S. Midwest since farming started there more than 150 years ago.University of Massachusetts Amherst

This corresponds to the loss of roughly 1.9 millimeters of soil per year from agricultural fields since the estimated start of traditional farming at these sites more than a century and a half ago, the researchers calculate. That rate is nearly double the maximum of one millimeter per year that the USDA considers sustainable for these locations.  

There are two main ways that the USDA currently estimates the erosion rate in the region. One way estimates the rate to be about one-third of that reported by the researchers. The other estimates the rate to be just one-eighth of the researchers’ rate. Those USDA estimates do not include tillage, a conventional farming process in which machinery is used to turn the soil and prepare it for planting. By disrupting the soil structure, tilling increases surface runoff and erosion due to soil moving downslope.

Larsen and colleagues say that they would like to see tillage incorporated into the USDA’s erosion estimates. Then, the USDA numbers might better align with the whopping 57.6 billion metric tons of soil that the researchers estimate has been lost across the entire region in the last 160 years.

This massive “soil loss is already causing food production to decline,” Larsen says. As soil thickness decreases, the amount of corn successfully grown in Iowa is reduced, research shows. And disruption to the food supply could continue or worsen if the estimated rate of erosion persists.

Not everyone is convinced that the average amount of soil lost each year has remained steady since farming in the region started. Much of the erosion that the researchers measured could have been caused in the earlier histories of these sites, dating back to when farmers “began to break prairies and/or forests and clear things,” says agronomist Michael Kucera.

Perhaps current erosion rates have slowed, says Kucera, who is the steward of the National Erosion Database at the USDA’s National Soil Survey Center in Lincoln, Neb.

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To help reduce future erosion, farmers can use no-till farming and plant cover crops, the researchers note. By planting cover crops during off-seasons, farmers reduce the amount of time the soil is bare, making it less vulnerable to wind and water erosion.

In the United States, no-till and similar practices to help limit erosion have been implemented at least sometimes by 51 percent of corn, cotton, soybean and wheat farmers, according to the USDA. But cover crops are only used in about 5 percent of cases where they could be, says Bruno Basso, a sustainable agriculture researcher at Michigan State University in East Lansing who wasn’t involved with the study. “It costs $40 to $50 per acre to plant a cover crop,” he says. Though some government grant funding is available, “the costs of cover crops are not supported,” and there is a need for additional incentives, he says.

To implement no-till strategies, “the farmer has to be a better manager,” says Keith Berns, a farmer who co-owns and operates Green Cover Seed, which is headquartered in Bladen, Neb. His company provides cover crop seeds and custom seed mixtures. He has also been using no-till practices for decades.

To succeed, farmers must decide what particular cover crops are most suitable for their land, when to grow them and when to kill them. Following these regimens, which can be more complicated than traditional farming, can be “difficult to do on large scales,” Berns says.

Cover crops can confer benefits such as helping farmers repair erosion and control weeds within the first year of planting. But it can take multiple years for the crops’ financial benefits to exceed their cost. Some farmers don’t even own the land they work, making it even less lucrative for them to invest in cover crops, Berns notes. 

Building soil health can take half a decade, Basso says. “Agriculture is really always facing this dilemma [of] short-sighted, economically driven decisions versus longer-term sustainability of the whole enterprise.” More

You can lead a cow to a water closet, but can you make it pee there? It turns out that yes, you can.

Researchers in Germany successfully trained cows to use a small, fenced-in area with artificial turf flooring as a bathroom stall. This could allow farms to easily capture and treat cow urine, which often pollutes air, soil and water, researchers report online September 13 in Current Biology. Components of that urine, such as nitrogen and phosphorus, could also be used to make fertilizer (SN: 4/6/21).

The average cow can pee tens of liters per day, and there are some 1 billion cattle worldwide. In barns, cow pee typically mixes with poop on the floor to create a slurry that emits the air pollutant ammonia (SN: 1/4/19). Out in pastures, cow pee can leach into nearby waterways and release the potent greenhouse gas nitrous oxide (SN: 6/9/14).

“I’m always of the mind, how can we get animals to help us in their management?” says Lindsay Matthews, a self-described cow psychologist who studies animal behavior at the University of Auckland in New Zealand. Matthews and colleagues set out to potty train 16 calves, which had the free time to learn a new skill. “They’re not so involved with milking and other systems,” he says. “They’re basically just hanging out, eating a bit of food, socializing and resting.”

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Matthews was optimistic about the cows’ potty-training prospects. “I was convinced that we could do it,” he says. Cows “are much, much smarter than people give them credit for.” Each calf got 45 minutes of what the team calls “MooLoo training” per day. At first, the researchers enclosed the calves inside the makeshift bathroom stall and fed the animals a treat every time they peed.

Once the calves made the connection between using the bathroom stall and receiving a treat, the team positioned the calves in a hallway leading to the stall. Whenever animals visited the little cows’ room, they got a treat; whenever calves peed in the hallway, the team spritzed them with water. “We had 11 of the 16 calves [potty trained] within about 10 days,” Matthews says. The remaining cows “are probably trainable too,” he adds. “It’s just that we didn’t have enough time.”

[embedded content]
Researchers successfully trained 11 calves, such as this one, to urinate in a bathroom stall. Once the cow relieved itself, a window in the stall opened, dispensing a molasses mixture as a treat. Toilet training cows on a large scale and collecting their urine to make fertilizer could cut down on agricultural pollution, the team says.

Lindsay Whistance, a livestock researcher at the Organic Research Centre in Cirencester, England, is “not surprised by the results.” With proper training and motivation, “I fully expected cattle to be able to learn this task,” says Whistance, who was not involved in the study. The practicality of potty training cows on a large scale, she says, is another matter.

For MooLoo training to become a widespread practice, “it has to be automated,” Matthews says. “We want to develop automated training systems, automated reward systems.” Those systems are still far from reality, but Matthews and colleagues hope they could have big impacts. If 80 percent of cow pee were collected in latrines, for instance, that could cut associated ammonia emissions in half, previous research suggests.

“It’s those ammonia emissions that are key to the real environmental benefit, as well as potential for reducing water contamination,” says Jason Hill, a biosystems engineer at the University of Minnesota in St. Paul not involved in the work. “Ammonia from cattle is a major contributor to reduced human health,” he says (SN: 1/16/09). So potty training cattle could help create cleaner air — as well as a cleaner, more comfortable living space for cows themselves. More

When corn farmers harvest their crop, they often leave the stalks, leaves and spent cobs to rot in the fields. Now, engineers have fashioned a new strain of yeast that can convert this inedible debris into ethanol, a biofuel. If the process can be scaled up, this largely untapped renewable energy source could help reduce reliance on fossil fuels.

Previous efforts to convert this fibrous material, called corn stover, into fuel met with limited success. Before yeasts can do their job, corn stover must be broken down, but this process often generates by-products that kill yeasts. But by tweaking a gene in common baker’s yeast, researchers have engineered a strain that can defuse those deadly by-products and get on with the job of turning sugar into ethanol.

The new yeast was able to produce over 100 grams of ethanol for every liter of treated corn stover, an efficiency comparable to the standard process using corn kernels to make the biofuel, the researchers report June 25 in Science Advances.

“They’ve produced a more resilient yeast,” says Venkatesh Balan, a chemical engineer at the University of Houston not involved in the research. The new strain may benefit biofuel producers trying to harness materials like corn stover, he says.

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In the United States, most ethanol is made from corn, the country’s largest crop, and is mixed into most of the gasoline sold at gas stations. Corn ethanol is a renewable energy source, but it has limitations. Diverting corn to make ethanol can detract from the food supply, and expanding cropland just to plant corn for biofuel clears natural habitats (SN: 12/21/20). Converting inedible corn stover into ethanol could increase the biofuel supply without having to plant more crops.

“Corn can’t really displace petroleum as a raw material for fuels,” says metabolic engineer Felix Lam of MIT. “But we have an alternative.”

Lam and colleagues started with Saccharomyces cerevisiae, or common baker’s yeast. Like sourdough bakers and brewers, biofuel producers already use yeast: It can convert sugars in corn kernels into ethanol (SN: 9/19/17).

But unlike corn kernels with easy-access sugars, corn stover contains sugars bound in lignocellulose, a plant compound that yeast can’t break down. Applying harsh acids can free these sugars, but the process generates toxic by-products called aldehydes that can kill yeasts.

But Lam’s team had an idea — convert the aldehydes into something tolerable to yeast. The researchers already knew that by adjusting the chemistry of the yeast’s growing environment, they could improve its tolerance to alcohol, which is also harmful at high concentrations. With that in mind, Lam and colleagues homed in on a yeast gene called GRE2, which helps convert aldehydes into alcohol. The team randomly generated about 20,000 yeast variants, each with a different, genetically modified version of GRE2. Then, the researchers placed the horde of variants inside a flask that also contained toxic aldehydes to see which yeasts would survive.

Multiple variants survived the gauntlet, but one dominated. With this battle-tested version of GRE2, the researchers found that the modified baker’s yeast could produce ethanol from treated corn stover almost as efficiently as from corn kernels. What’s more, the yeast could generate ethanol from other woody materials, including wheat straw and switchgrass (SN: 1/14/14). “We have a single strain that can accomplish all this,” Lam says.

This strain resolves a key challenge in fermenting ethanol from fibrous materials like corn stover, Balan says. But “there are many more improvements that will have to happen to make this technology commercially viable,” he adds, such as logistical challenges in harvesting, transporting and storing large volumes of corn stover.

“There are so many moving parts to this problem,” Lam acknowledges. But he thinks his team’s findings could help kick-start a “renewable pipeline” that harnesses underused, sustainable fuel sources. The vision, he says, is to challenge the reign of fossil fuels. More