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    More than 57 billion tons of soil have eroded in the U.S. Midwest

    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

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    Potty-trained cattle could help reduce pollution

    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

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    A tweaked yeast can make ethanol from cornstalks and a harvest’s other leftovers

    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