Growing a Revolution, page 24
What will it take to build up carbon levels in degraded agricultural soils? Top-down soil building. The old bottom-up view of soil formation as a simple product of rock weathering held that it takes hundreds of years, or longer, to form an inch of soil. The new view that incorporates biology—cover crops, exudates, microbes and soil life—holds that we can grow soil much faster, in decades instead of centuries.
The majority of the carbon that builds up in the soil comes from root exudates. Tie up carbon in life forms and it can’t ascend skyward. This is why mob grazing works so well for building up soil carbon—it stimulates exudate production like nothing else.
All this points to a big problem with conventional grain monocultures. As a crop begins to grow, it takes time before the plants build up enough photosynthetic carbon to produce exudates. And when the crop becomes reproductive, root exudates shut off as the plant shunts resources into seed production. So there is only a four- to five-week period when grains push exudates into the soil. That just isn’t enough time to pump out much carbon. So grain crops don’t contribute a lot to building up soil carbon. To dramatically increase soil carbon, cover crops are needed to push exudates into the soil over more of the year.
However, the carbon storage potential of soils is not unlimited. The pace of carbon buildup ramps to a maximum in the decades after adoption of new practices and eventually hits a plateau, above which it gets harder to further increase carbon storage. In this sense, soils are like batteries that can only get so charged up before it becomes pointless to keep charging them. Still, agricultural soils can potentially store a substantial amount of carbon over the coming decades. Researchers have estimated that it would take at least fifty years for European soils to max out soil-carbon levels after adoption of conservation agriculture. This means that soil-building agriculture can help buy time to transition to other energy sources or means of sequestering carbon before soil carbon storage becomes saturated.
Unlike many technologies to mitigate fossil fuel emissions, soil-building practices can be implemented immediately at low cost. And because these practices already make economic sense for many, if not most, farms, they might be readily adopted—if known about and promoted. If this sounds like an all-too-rare win-win situation, that’s because it is, or could be if we pursued it.
FINDING A BETTER WAY
Just how feasible is large-scale, soil-based carbon sequestration? Can it work on typical North American commodity crop farms without livestock? These were questions I’d come to Ohio to ask. Gabe Brown had told me that I had to go see David Brandt’s farm in Carroll, Ohio. Actually, he told me I had to see his soil.
For the past forty years, Brandt has run a farm-scale experiment in long-term soil building. He didn’t do it to explore the potential to sequester carbon on farms. He did it because he believes it’s the right way to build fertile soil on his farm. Yet in retrospect he’s shown how profitable changes in farming practices can deliver a hefty side benefit of carbon emission offsets.
After sitting in horrendous traffic on the drive from Columbus, Lal and I pulled into Brandt’s farm down a long driveway between fields and headed to the outbuildings behind the house. Brandt welcomed us jovially. An ex-marine who has been no-tilling since he came back from Vietnam, he has huge hands and a round face, which was shaded by a baseball cap. In his white shirt and blue-jean overalls, he looked the part of genial grandpa farmer.
But Brandt is far from a typical farmer. An unconventional corn and soy producer who owns 160 acres and leases another 800 acres, he’s become a well-known leader in the cover-crop revolution. Mostly, he’s followed a corn/soybean/wheat/cover-crop rotation. He plants cover crops into the wheat stubble two to three weeks after harvest. And when the roots of cover crops like buckwheat die, they release acids that help solubilize phosphorus and other mineral nutrients. If you don’t kill the cover crop, you don’t get this additional input, so if the winter doesn’t kill the cover crop first, then Brandt finishes it off with an herbicide or a crop roller like Jeff Moyer uses at Rodale. The idea is to not let the cover crop pull nitrogen and phosphorus from the soil to make seeds, but to time the growth of cover crops in such a way as to release the nutrients conserved in their biomass back to the soil for his next crop to take up.
It was late in the day, and Brandt was eager to show us his fields. So he ushered us over to his four-wheeler. His dog, a Weimaraner named Yankee, jumped in, happy to ride along to the fields.
Brandt started planting cover crops back in 1978, when he seeded cereal rye onto bare fields to control erosion. Now he grows cover crop communities, with up to ten different types at a time in a field. He likes to feed his soil a diverse diet—a mix of cover crops, mostly legumes and radishes, which he knocks down to rot where they grew so they can nourish the subsequent cash crop.
Our first stop was a field with a ten-way seed blend, planted to prepare the ground for a crop of corn. Yankee hopped down to scout for something to chase. To me the field looked like a diverse stand of wildflowers. When Lal asked him how much of his farm is under cover crops, Brandt replied, “By fall harvest, 100 percent is under cover crops.” When I mused out loud something to the effect of how much the field looked like a salad bar for cows, Brandt replied that he does not have any cows. On this farm the livestock is all underground.
He drove us across a field he’d planted with cover crops after harvesting 96 bushels of wheat per acre, and Lal asked about the greener strips running lengthwise down the field. “That’s where a malfunctioning urea spreader dropped some extra nitrogen onto certain rows,” Brandt replied. Fortunately, the cover crops were capturing the excess, keeping it in the field for his next crop to use instead of letting it run off to pollute elsewhere, like it would from a plowed field.
Our next stop revealed an elegant experiment, a side-by-side comparison of Brandt’s field with the neighboring 81-acre farm he’d just bought. His side of the old property line had been no-till for forty-four years, while the neighbor’s side had a long history of conventional tillage. When Brandt first started farming the neighbor’s field as a tenant, it had 0.25 percent organic matter. Now, after two years of no-till and cover crops, it’s up to 1.1 percent, an increase of almost half a percent per year. His goal is to bring his newly acquired fields up to 5 percent within seven years.
Experience tells him that the investment will pay off. In Brandt’s recently acquired fields, the cover crops were half as high as in his no-till field. Before moving on, he reached down and yanked up a three-inch-long radish, a clod of soil dangling from its thick taproot. The soil was light brown with solid, platy chunks.
He then herded us back onto the four-wheeler and drove us over to his forty-four-year no-till field, which had been planted with the same cover-crop mix at the same time. Here, he pulled up a fat ten-inch-long radish. The soil was dark brown, crumbly to the touch, and gave off a rich earthy smell.
Back in the 1970s, Brandt’s field had started at less than half a percent carbon, just like his neighbor’s. In the decades since he started growing cover crops, it’s increased to 8.5 percent; the carbon content of the native soil in his woodlot is not quite 6 percent. He’s managed to raise the organic-matter level in his fields above that of the native soil, just as Rodale’s Kristine Nichols predicted was possible. “How high do you think your fields will go?” I asked him. “I’d be happy if it stopped, but I don’t think it’s going to,” he replied.
He gives his radishes credit for much of this transformation. Radishes are rapidly becoming a favorite cover crop among farmers, as both experience and research show their beneficial effects on soil quality and crop health. Radishes provide effective suppression of winter annual weeds from fall through early spring, and they grow taproots that can extend down three feet in just two months. When radishes rot after being killed by winter frosts, the large vertical holes they leave improve soil infiltration and help break up compacted ground. They have also been shown to increase plant-available soil phosphorus around their root holes, and to be excellent scavengers of soil nitrogen after summer crops. When they decompose, they rapidly release nitrogen and other nutrients back to the soil. All of this really adds up. An analysis of Brandt’s land that had been planted with tubers, like radishes, found that each acre recycled 250 pounds of nitrogen, almost as much potassium, and 23 pounds of phosphorus.
Other plants in his crop mixes serve other purposes. Sunflowers, for example, excel at scavenging zinc from depth and bringing it into the topsoil. Where Brandt plants sunflowers, he sees the plant-available zinc levels rise in his soil tests. Hairy vetch and Austrian winter peas have added between 100 and 200 pounds of nitrogen per acre. Since he’s been planting diverse cover crops, he’s found that his plant-available soil phosphorus and potassium levels have climbed, even though he’s greatly reduced his fertilizer application. He says his agronomist tells him that’s not possible.
Farther down the old property line, Brandt showed us the contrast in this year’s corn on opposite sides of his old fence line. To our right was the field he bought two years ago. We passed six-foot-tall corn that had been planted along with soybeans and received no herbicide. He thinks he’ll make 140 bushels an acre out of the field, just under the county-average corn yield of 145 bushels an acre.
Then the corn steps down to just three or four feet tall. He said, “You see what’s happened here? This is where I ran out of soybeans.” From there on, the field had instead received 160 pounds of nitrogen fertilizer per acre as well as herbicide treatments. He thinks he’ll be lucky to get 100 bushels an acre from this field. We dug into the hard soil with a shovel. It was light brown, dry, and platy.
“Now look at this,” he said as he waded into a thicket of corn rising several feet above his head on the other side of the road—the side that he’s no-tilled for over four decades. This field has not had any fertilizer or herbicide for two years and no fungicide or pesticides for nine years. I bent down and dug into the soil with my bare hand. It was dark brown, moist, and crumbly, with a lush smell.
Brandt expected to get 200 bushels an acre from this field. Only he was planning to do it with no chemical inputs, thanks to his soil-building practices. And this wasn’t an unusual year. According to him, his corn and soybean yields are generally at least 20 percent above county average. He does even better in dry years.
I was particularly impressed with the way Brandt runs his own experiments. Like most farmers in the county, he had been pairing genetically modified (GM) corn and a lot of herbicide. But he’s experimenting with whether he really needs either.
This year he was comparing varieties of organic corn with varieties of GM corn, planted in narrow quarter-mile-long strips. These were not small-scale research test plots. So far, the organic seeds that cost $105 a bag were “all doing pretty good.” He’d expected to have cutworms in the organic plots but didn’t. He was comparing that with non-GM, insecticide-treated seed that cost $160 a bag, and similarly treated GM corn that cost $336 a bag. At these prices, he said, he’d need to harvest 45, 60, and 90 bushels of corn, respectively, to simply break even for the three types. This meant that the GM seeds would have to be twice as productive as the organic ones to pay off.
He also had a soil-life study done two weeks after planting. It revealed that there was half as much soil life where he’d planted insecticide-treated seed. “Did seed corn treatment eliminate my underground critters?” he asked. “Are we hurting ourselves using this in our fields?” I suspect that such curiosity underlies how he’s worked out soil building practices that promote beneficial soil life.
He was also maintaining a control plot for his county’s typical practice of full tillage and the addition of 200 pounds of nitrogen, even more phosphorus-rich row starter, and 2.5 quarts of Roundup an acre. With all these inputs, he’d invested $502 an acre. He predicts it won’t make 100-bushel corn. That pencils out to a net loss at anything under $5 a bushel. Lately corn has sold for less than $4. With that system, the more acres he plants, the more money he loses.
In contrast, on each acre of his forty-four-year no-till cover-cropped fields, Brandt spent $137 on seed corn and used just 24 pounds of nitrogen at $0.60 per pound and an $8 quart of Roundup. Along with $160 cash rent, this comes to a total expense of just under $320 an acre. At the current $3.80 a bushel, his estimated corn harvest of 182 bushels an acre would return just over $690 an acre, a net profit of about $370 an acre, not counting his time, cover crop seed, and equipment costs.
Plus, Brandt saved more on diesel too. He says he used a bit more than 2 gallons an acre while, on average, his conventional tillage neighbors use more than 10 gallons an acre.
So while Brandt was using less than half the herbicide, about a fifth of the diesel, and a tenth of the fertilizer, he consistently outyielded his neighbors who practice conventional tillage with no cover crops. Unlike too many of their farms, Brandt’s operation is actually profitable—quite profitable.
Consider, for example, the contrast with the farmer right across the road who recently bought 720 acres for almost $5 million. The farm had been run for thirty years with a corn-soybean rotation and no cover crops, wearing the soil down to just a few percent organic matter. The first year, the new owner used more than 220 pounds of nitrogen an acre and sprayed herbicides three times. Brandt estimated that “he’s probably got $560 an acre in expenses and $320 for debt on the land. If he does really well and grows two hundred bushels an acre, he’ll make $760 an acre. So he’s already lost $120 an acre before he’s even paid his diesel bill. How will he be able to keep going?”
Here is the trap that input-intensive farmers fall into, where they pay high costs at the front end and focus on yields and gross returns rather than on the spread between expense and income. High input costs and low commodity prices are a recipe for farm failure. This has been the story of the American family farm since the Second World War.
On his farm, Brandt has found that he doesn’t need to add any nitrogen to a field once it reaches 8 percent organic matter. At that level, his cover-crop-fueled nutrient recycling is equivalent to applying 240 pounds of nitrogen fertilizer an acre annually. His input costs are low, yields are good even in dry years, and pests are not a routine problem or threat to crops. This sounded like resilient and sustainable farming to me.
The next day, Brandt picked me up at my hotel in his red Dodge Ram, a practical, no-frills pickup truck. The drive to the Ohio No-Till Council’s field day workshop gave him a chance to express his concerns about how conventional agriculture treats the soil as a giant growing medium, with the expectation that if you just stick chemical nutrients in it, crops will come out. He wants everybody to learn to take care of the soil, because he fears that our society won’t exist in a hundred years if we don’t.
Experience is a good teacher and Brandt is a tinkerer—always testing out new ways of doing things, curious about what might work better. He likes to challenge guys who supposedly know it all. He laughed hard when I confided to him that universities are filled with such folk. When he first heard academics talk about an eight-way cover-crop mix, he was a single-species guy and simply believed an eight-species mix was a recipe for weeds. Still, he tried it out. After a year he was surprised to see positive changes in the soil and began experimenting with cover-crop mixes.
Brandt now sees cover crops as the key to supporting his microbial livestock. Cover crops don’t just feed the microbes, they help moderate soil temperature so the microbes can work for him. In the hottest summer months, his neighbors’ bare soils can heat to well over 110°F. But his soils don’t get over 97°F. This matters, remember, because microbial activity pretty much stops above 100°F.
A decade ago he didn’t know that there was a herd of livestock in the soil. He was taught that if he just applied the right nutrients he’d see higher yields. “I didn’t know that earthworms eat our weed seeds, drag them down in winter, and manage weeds for us.” Since then he’s learned to feed his belowground livestock.
Brandt has spent his whole life on farms, the first of which was just a few miles from where he now farms. He turned seventy a couple months after I visited, and had started no-tilling in 1971—not by choice but out of necessity.
The day after he got married in 1966, he got a notice from his draft board to get a physical, and the next thing he knew, he was a sergeant in the Marine Corps. To this day he peppers his speech with “yes sir” and “no sir,” a habit, I suspect, left over from those days. After serving in Vietnam for a few years, he returned home to find that his father had died without a will and his family had been forced to sell the farm.
His luck began to change when a niece of J. C. Penney (yes, that J. C. Penney) called, looking for a tenant to farm 400 acres under the guidance of an elderly farm manager who had worked for the Eisenhower administration. The manager told Brandt that the only way he’d be able to work the farm by himself was to go no-till.
When Brandt sold his tillage equipment and bought a no-till planter, his eighty-six-year-old grandfather, who’d plowed behind a pair of mules in his youth, was more than a little concerned. At the sight of his grandson planting his first no-till field, he took off his big straw hat and exclaimed, “My god, boy, what are you doing?” That year the corn made 127 bushels an acre. Grandpa was impressed. So was Brandt.
He did well at first but found that under his single-crop, low-residue routine, the ground became harder and yields starting falling. Even so, he refused to go back to tillage. So, in 1978, he planted hairy vetch and varieties of clover as cover crops. The hairy vetch worked so well that he stuck with it, experimenting with single-species stands of cover crops for twenty years. Then, in 1997, he decided to give peas and radishes a try, planting them in alternating rows. He immediately saw further improvement in his soil. After attending a field day demonstration at a conference in 2001, in which five-, six-, and seven-way cover-crop mixes were featured, he decided to try multiple species cover cropping. He was soon sold on the soil-improving power of combining no-till with a diverse mix of cover crops.
