Healthy food, healthy climate? The dirt on soil and carbon
Healthy food, healthy climate? The dirt on soil and carbon
This excerpt is adapted from Courtney White's "Grass, Soil, Hope" (May 2014) and is printed with permission from Chelsea Green Publishing.
It must have looked silly. Twelve of us were hunched over in a corn field under a blazing July sun, a few miles north of Emporia, Kansas, swishing butterfly nets among the corn stalks like deranged collectors chasing a rare breed of insect — deranged because it was a record-breaking 105 degrees.
The federal government announced two days before I arrived that the Midwest was in the grip of the worst drought since 1956. Legions of farmers had begun plowing under or chopping up their stunted corn and soybean crops, already writing off the year as a complete failure.
There we were, however, swishing our nets back and forth 50 times in a good-looking corn field owned and farmed by Gail Fuller, with nothing between us and the blazing sun except our determination to follow instructions and find spiders. We found lots of spiders.
Back under the shade of a large oak tree, we handed our nets to our instructor, an affable entomologist with the U.S. Department of Agriculture, who searched through them enthusiastically, pulling out spider after spider with his bare fingers (most spiders are poisonous, he told us, but very few can pierce human skin).Peering over his shoulder, I was amazed not only by the quantity of spiders in my net but by their diversity. I never knew so many odd-looking spiders existed! And who would have expected it from a corn field, in a record drought, during midday heat . . . which was exactly the point of the exercise, of course.
In a conventionally managed, monocropped Midwestern corn field, planted with genetically modified (GM) seeds, fertilized with industrially produced nitrogen and sprayed with synthetic chemicals, there would be no spiders, the entomologist told us — drought or no drought. There wouldn’t be much of anything living, in fact, except the destructive pests that could withstand the chemicals.
The corn field we had just swept, however, was different, and I knew why. Fuller’s field was no-tilled, it had a cover crop (and moisture in the soil as a result), it didn’t use GM seeds, its corn coexisted with a diversity of other plants, and livestock were used to clean up after the harvest — all the things I had learned in my travels so far. All in one field, all under a broiling sun.
Seeing them together, however, wasn’t the reason I had driven across humid Kansas in mid-July. I came to hear Jill Clapperton, an independent soil scientist and cover crop specialist, and to ask her a question: What happened to the nutrition in our food? And a second one: How can we get it back?
These questions first formed in my mind two years earlier, when I heard pioneering Australian soil scientist Christine Jones say at a conference that it was possible to buy an orange today that contained zero vitamin C. As in zilch. It got worse.
In Australia, she continued, the vitamin A content of carrots had dropped 99 percent between 1948 and 1991, according to a government analysis, and apples had lost 80 percent of their vitamin C. She went on to say that according to research in England, the mineral content of nearly all vegetables in the United Kingdom had dropped significantly between 1940 and 1990. Copper had been reduced by 76 percent, calcium by 46 percent, iron by 27 percent, magnesium by 24 percent and potassium by 16 percent. Furthermore, the mineral content of U.K. meat had dropped significantly over the same period as well — iron by 54 percent, copper by 24 percent, calcium by 41 percent and so on.
This is important because all living creatures, humans included, need these vitamins and minerals to stay strong and healthy. Iron, for example, is required for a host of processes vital to human health, including the production of red blood cells (hemoglobin), the transportation of oxygen through our bodies, the conversion of blood sugar to energy and the efficient functioning of our muscles.
Copper is essential for the maintenance of our organs, for a healthy immune system and to neutralize damaging "free radicals" in our blood. Calcium, of course, is essential for bone health. And every single cell in our body requires magnesium to function properly. Vitamins are organic compounds, by the way, composed of various chemicals and minerals, including carbon.
A deficiency or imbalance of these minerals (necessary to us only in small amounts) can cause serious damage to our health, as most people understand. That’s why taking vitamin pills has become such a big deal — and big business — today, especially where young children are concerned. But few people stop to think about why we need vitamin pills in the first place.
It’s not simply because we don’t eat our veggies or because we drink too much soda, but because the veggies themselves don’t have the amount of essential nutrients that they once did. As Jones quipped, for Aussies today to gain a comparable amount of vitamin A from carrots that their grandparents could, they’d have to eat themselves sick.
How did this happen? Well, the quick answer is that industrial agriculture happened. The hybridization of crops over the decades for production values — yield, appearance, taste and ease of transport — has drained fruits and vegetables of nutrients. But the main culprit is what we’ve done to the soil.
As a consequence of repeated plowing, fertilizing and spraying, the top few feet of farmland soil has been leached of its original minerals and stripped of the biological life that facilitates nutrient uptake in plants. Some farms, especially organic ones, resupply their soils with mineral additives, but many farms do not, preferring to rely on the Big Three — nitrogen, potassium and phosphorus (NPK) — to keep the plants growing.
According to the industrial mind-set, as long as crops are harvestable, presentable, digestible and profitable, it doesn’t matter if their nutrition is up to par. If there’s a deficiency, well, that’s what the vitamin pills are for.
However, it was the next thing that Jones said that spun my wheels. There was another way to remineralize our bodies without having to rely on pills or their corporate manufacturers: restore essential elements the old-fashioned way — with plant roots. With carbon, specifically.
Building humus by increasing the amount of carbon in the soil via no-till agriculture, planned rotational grazing and other practices that stimulate mycorrhizal fungi/root activity and the production of glomalin, she said, would:
- increase the availability of potassium, calcium, phosphorus, sulfur, copper, zinc, iron, magnesium and boron to plant roots (which are good for plants)
- reduce availability of sodium and aluminum (which are bad for plants)
- increase the pH in the soil (from acidic to neutral — good for everything)
Access to these essential minerals in combination with carbon means vitamins and other types of nutrients, including acids, carbohydrates, fats and proteins, can be produced within a plant.
One key to building soil carbon on farms is cover crops — plants that keep the land covered with something green and growing at all times, even in winter. I went to Kansas to find out more.
Clapperton, who hails originally from Canada but lives today on a Montana ranch, told the workshop audience that the key to rebuilding soil health is to start a "conversation among plants." Cool-season grasses (such as barley, wheat and oats) and cool-season broadleaf plants (such as canola, pea, turnip, lentil, radish and mustard), she said, need to dialogue constructively with warm-season grasses (including millet, corn and sorghum) and warm broadleafs (such as buckwheat, sunflower and sugar beet).
Who gets along with whom? Who grows when? Who helps whom? If you can get these plants engaged in a robust conversation in one field, she said, you’ll be creating "a feast for the soil." That’s because increased plant diversity, as well as year-round biological activity, absorbs more CO2, which in turn increases the amount of carbon available to roots, which feeds the microbes, which builds soil, round and round.
This is exactly what happened on Fuller’s farm. When he took over the operation from his father they were growing just three cash crops: corn; wheat; and soybeans. Today, Fuller plants as many as 53 kinds of plants on the farm, mostly as cover crops, creating what Clapperton called a "cocktail" of legumes, grasses and broadleaf plants.
He doesn’t apply any herbicides, pesticides or fertilizers either, despite the recommendations of his no-till neighbors and chemical manufacturers who advise them. That’s because Fuller considers "weeds" to be a part of the dynamic conversation as well. Besides, chemicals kill life, Clapperton reminded us, including spiders, dung beetles and even grasshoppers.
As a result of this big, robust conversation, Clapperton said, the carbon content of the soil on the Fuller farm has doubled from 2 percent in 1993 (when they switched to no-till) to 4 percent today. That’s huge. But what about the mineral content of Fuller’s crops?
That’s risen dramatically too, she said, and it’s done so for two reasons: First, no-herbicide/no-pesticide no-till means the microbial universe in the soil remains intact and alive, and if the soil dwellers have enough carbon (as an energy source) they will facilitate the cycling of minerals in the soil, especially earthworms, who are nature’s great composters. Second, a vigorous and diverse cover of crops will put down deeper roots, enabling plants to access fresh minerals, which then become available to everything up the food chain, including us.
And by covering the soil surface with green plants, or litter from the dead parts, Clapperton said, a farmer such as Fuller traps moisture underground, where it becomes available for plants and animals (of the micro variety), enabling roots to tap resources and growing abundant life.
"Above-ground diversity is reflected in belowground diversity," she said. "However, soil organisms are competitive with plants for carbon, so there must be enough for everybody."
Predator-prey relationships are also important to nutrient cycling, she said. Without hungry predators, such as protozoa and nematodes, the bacteria and fungi would consume all the nutrients in the soil and plants would starve. Predators above-ground play a positive role too, including spiders, and especially the No. 1 predator: ants.
So exactly how do minerals get into plants? There are two principal paths: First, minerals can dissolve in water, and when the water is pulled into the plant through its roots, the minerals are absorbed into the cells of plant tissue. Whichever minerals the plant doesn’t need (or doesn’t want) will remain stored in the cells. Second, mineral nutrients can enter a plant directly by being absorbed through the cell walls of root hairs.
Some minerals, such as phosphorus, can also "hitch a ride" with mycorrhizal fungi, which then "barter" them for carbon molecules from the plant roots. Of course, if there aren’t any minerals in the vicinity, no uptake into plants is possible.
It all begins with a dynamic conversation at a cocktail party for plants — where everyone is gossiping about carbon.
Standing under the oak tree at the end of the workshop, after we had oohed and aahed over a giant wolf spider someone discovered under a shrub, Clapperton reminded us why using nature as a role model — for cover crops in this case — was so important: We need to recycle nutrients, encourage natural predators to manage pests and increase plant densities to block weeds, which in a natural system are all integrated and interconnected strategies.
This reminded me of something the great conservationist Aldo Leopold once wrote:
"The black prairie was built by the prairie plants, a hundred distinctive species of grasses, herbs, and shrubs; by the prairie fungi, insects, and bacteria; by the prairie mammals and birds, all interlocked in one humming community of cooperations and competitions, one biota. This biota, through ten thousand years of living and dying, burning and growing, preying and fleeing, freezing and thawing, built that dark and bloody ground we call prairie."
One biota. With carbon at its core.