Farming with this amendment isn’t a climate silver bullet, but it could make more soil a carbon sponge.
May 3, 2021
As the adoption of no-till practices has spread widely across parts of the U.S. over the past few decades, the approach has been touted as an important means of storing carbon in soil—and a key solution to solving the climate crisis.
But despite its recent growth in popularity, “no-till” has no single, agreed-upon meaning. In fact, the phrase is often a misnomer. Most no-till farmers have not cut out tillage altogether and do not engage in other beneficial practices such as planting cover crops. As a result, these “seldom-till” farmers aren’t able to permanently store carbon in their soil.
That trend, coupled with the scientific uncertainty on how to measure and verify carbon sequestration, could throw a wrench into the Biden administration’s plan to fund an agricultural carbon trading program (or “carbon market”) as a central response to climate change.
“The reality is that 100-percent-never-till is [practiced on] a very small percentage of the acres across the United States,” said Steve Swaffar, executive director of No-Till on the Plains, a nonprofit that hosts an annual conference for no-till farmers in the Great Plains region. “There’s certainly a need to change this.”
Tillage has been an intrinsic part of global agriculture for thousands of years. Breaking up soil helps clear land for production and quickly uproots and kills weeds. Tilling also aerates and warms the soil, buries plant residue, incorporates fertilizer or compost, and creates a clean, level bed to make seed planting easier.
Some farmers adopted limited soil conservation practices in the aftermath of the Dust Bowl—caused, in part, by intensive tillage practices—but most continued to plow up their fields multiple times every year. It wasn’t until the 1970s that farmers in the Midwest, the Plains, and the Southeast began switching in earnest to no-till and reduced tillage practices, spurred by the widespread availability of broad-spectrum herbicides, including glyphosate (the main ingredient in Roundup), and later by the genetically modified crops resistant to those herbicides.
In some cases, chemical companies such as Imperial Chemical Industries, which developed the controversial herbicide paraquat (also known by its brand name Gramoxone), conducted no-till experiments and helped spread the concept of reduced soil disturbance.
Liberated from the need to plow for weed control, farmers who grew commodities such as corn and soy began to spray them with herbicides and parked their tillage equipment to cut down on fuel and labor costs—a much-needed relief during the energy crisis of the 1970s and the farm crisis of the 1980s.
Today, the no-till movement continues to be concentrated in regions that grow commodity crops with the use of chemicals: states with the highest no-till adoption rates include Montana (73 percent of all acres), Kentucky (68 percent), Tennessee (79 percent), and Virginia (74 percent).
The practice has also gained favor with farmers looking to switch to so-called regenerative practices—either as a way to build healthy soil and reduce input costs, or because the company they sell their crops to is in some way incentivizing the change. General Mills, for instance, has committed to converting 1 million acres to regenerative practices and Danone, Walmart, and a number of other large consumer packaged goods (CPG) companies have taken on similar initiatives—meaning that many farmers are making the change to meet the demands of the marketplace.
According to the 2017 U.S. Census of Agriculture, the number of the farms practicing intensive tillage declined by 35 percent between 2012 and 2017. The number of farms practicing reduced tillage increased by 11 percent. And while no-till farms increased by less than 1 percent during the same time period, the number of no-till acres has continued to increase.
On the ground, there’s ample evidence suggesting that the vast majority of no-till farmers occasionally or regularly return to tillage, calling into question the environmental benefits and carbon-absorbing potential of their soils.
A study by the U.S. Department of Agriculture’s (USDA) Economic Research Service found that while nearly half of all corn, soybean, wheat, and cotton acreage was identified as no-till or strip-till (tilling small areas of fields to prepare seed beds for planting) at some time over a four-year period, only about 20 percent of these acres were identified that way for the whole duration.
The terms “reduced till” and “minimal till” can also mislead. They’re both undefined versions of the generic “conservation tillage,” which denotes a wide range of systems that leave at least 30 percent of the soil surface covered by crop residue after planting. In practice, this often means a farmer has slightly reduced the number of tillage passes or simply switched from a moldboard plow—the most aggressive tillage practice—to a chisel plow, a slightly less destructive one.
One former USDA researcher even called “conservation tillage” an oxymoron that “gives a misguided sense of entitlement and conservation,” despite the fact that many of the practices under its umbrella lead to “significant soil loss” and hence are not sustainable.
Factors such as climate, soil type, crop type, cultural convention, family dynamics, and a limited understanding of how soil works may influence a farmer’s decision to take up the plow again, soil health experts say.
Many no-tillers in the Midwest return to tillage on a regular basis, or alternate between years. Others strip till or till in a way that only disturbs the top two inches of soil, while still others will upturn their entire fields, said Swaffar with No-Till on the Plains.
Some farmers say a changing climate is making it difficult to stick with no-till. Justin Topp, who grows a number of grains and legumes on 14,000 conventional and 1,500 organic acres near Grace City in North Dakota, told Civil Eats that the short growing season in his area means untilled soil isn’t usually warm enough to plant seeds into. And then there’s the erratic weather: It was so wet in 2019, he said, that he had to till his fields in order to aerate and dry out the soil—otherwise, his crops would have failed.
On the other hand, this winter was so dry that he’s planning to convert some of the previous year’s minimum-till fields to complete no-till to retain moisture. (Topp has also tried inter-seeding a rye cover crop with the corn, but it failed to grow both during the wet and dry years.)
“I would love to switch to 100 percent no-till all the time,” said Topp. “We’re trying. But it just doesn’t work. . . . We have to make the best decision for our farm year after year.”
Still other farmers break out the plows because their fields are overgrown with weeds that have become resistant to herbicides (i.e., “superweeds”). There are now several hundred herbicide-resistant weeds in the world, affecting farmers across the entire U.S. One 2018 study found that the spread of glyphosate-resistant weeds is responsible for a 9 percent reduction in the use of no-till practices in soybean production.
Most commodity farmers overwhelmed by weeds don’t grow a diverse enough range of crops to disrupt the weed cycles, Swaffar said. And local cultural mores, family relationships, and pressure from herbicide sales reps all tend to sway farmers toward tillage when challenges in their no-till systems arise.
“Tillage is still culturally accepted and financially supported,” Swaffar added. “It’s promoted by equipment manufacturers, producers of genetically engineered seeds, and other industries that benefit from disturbing the land. The amount of dollars invested into those industries and economies is enormous.”
But perhaps the biggest challenge, said farmer and soil scientist Ray Archuleta, is farmers’ limited understanding of soil biology. They often take up the practice on its own—and continue to spray an excessive amount of chemicals, leave their soil bare, and fail to incorporate other regenerative practices, such as cover crops, grazing livestock, and diverse crop rotations beyond corn and soy.
“No-till by itself is not enough,” Archuleta said. “But if you combine no-till, cover crops, and livestock [grazing], the system changes completely and starts to work a lot better.”
Cover crops are grown on less than 4 percent of the nation’s cropland, meaning they’re absent from the vast majority of no-till farms. The good news, said Archuleta, is that their acreage increased by 50 percent between 2012 and 2017. “We’re working in the right direction,” he said.
Researchers today widely agree that tillage is destructive to soil. But, because soil science is an emerging field, just how destructive is still an open question. Tilling disrupts soil’s natural structure, and damages the beneficial mycorrhizal fungi networks. It also results in an immediate loss of substantial amounts of soil carbon as it enters the air in the form of carbon dioxide.
According to studies by the University of Nebraska Extension service, occasional tillage may be beneficial every 5–10 years to manage weeds, prevent soil compaction, or incorporate a soil amendment. The university concluded that any loss in soil organic matter is recovered within one year of the tilling event.
Similarly, research at the Kansas State University Southwest Research Extension Center showed that in a long‐term no‐till dryland rotation system of wheat grain−sorghum−fallow, a single tillage pass in a no-till system that was continuous for at least five years prior did not lead to significant effect on crop yield, biomass, available soil water, and water use compared with continuous no‐till.
And a recent study by the Pennsylvania-based Pasa Sustainable Agriculture, a farming education and research nonprofit, found that farms using some tillage can still achieve soil health benefits as long as they plant cover crops, incorporate crop rotations, and utilize other beneficial practices.
But other studies suggest that occasional tillage within long-term no-till systems can adversely affect soil quality and lead to an immediate release of carbon into the atmosphere—and only continuous no-till systems can lead to long-term increased yields and other benefits.
John Dobberstein, senior editor of the publication No-Till Farmer, believes that studies promoting a return to occasional tillage are misleading. He said they don’t tell farmers about the negative side effects of occasional tillage, including that it can cause more weeds to germinate, not less. It can also cause a decrease in soil moisture, an especially dire problem in semi-arid areas. The studies also fail to mention the fuel, labor, and equipment costs that cut into a farmer’s profitability, said Dobberstein.
No-Till Farmer aims to encourage farmers to try other solutions first, from planting cover crops and growing a greater diversity of crops, to changing the timing of herbicide applications.
“It takes a lot of dedication to be in continuous no-till,” Dobberstein said. “We try not to be judgmental. We know people have to do what’s best for their farm.”
Archuleta advises no-till farmers in dire-straights who are wanting to till their fields to consider tillage intensity, frequency, and depth.
“Do I say ‘never till’? If you have a situation and you’re desperate to till, do it when it’s cold and focus on just the affected area, not the whole field. Think about the ramifications,” he said.
Soil experts Archuleta and Swaffar say more education and support is needed for farmers to keep their no-till practices going long-term. They also say the emphasis on carbon markets is misguided.
Instead of paying farmers to store and calculate carbon, the government should pay them for the acreage of diverse cover crops they grow, Archuleta said. One reason a carbon market will be challenging, he said, is that building soil carbon is dependent upon climate, temperature, moisture, vegetation type, and soil characteristics. Soils in colder climates, silty clay, or clay soils, and certain types of crops can store more carbon, he said, putting some farmers at a distinct disadvantage.
“Paying farmers for carbon is not a smart goal because carbon [levels] change daily. It’s like paying for blood sugar levels,” Archuleta said. “And it would put a lot of producers on an unequal footing. Even if they were doing the same exact practices, they would never be able to build carbon the same way.”
Furthermore, measuring soil carbon is expensive, time-consuming, and not very accurate. Most soil sampling doesn’t measure deep carbon or account for seasonal fluctuations. It’s also impossible to guarantee that stored carbon will remain in the soil long-term, since a farmer who stopped tilling for years may decide to plow up their field at any point. There is only so much organic carbon that can be stored in soil, leading some scientists to question the long-term viability of no-till systems as carbon sinks.
In April, a coalition of environmental, agricultural, and justice groups sent a letter to Congress members asking them not to pass the newly introduced Growing Climate Solutions Act, a bill that would facilitate farmers’ participation in carbon market programs, because methods on measuring carbon are still being developed, soil carbon storage is limited, and participation in carbon offset programs may lead to further farm consolidation.
Diverse mixes of cover crop species, which have the potential to capture large amounts of carbon from the atmosphere and store it in soil, are less controversial and easier to measure, Archuleta said. And this potential means that even if a farmer needs to occasionally return to tillage, he or she can continue to store carbon and improve the soil, Swaffar added.
“Even if you return to tillage, but you grow cover crops instead of leaving your field bare, you would still have a positive impact on your soil biology,” said Swaffar. “If you look at the natural landscape, the soil is always trying to grow something.”
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