It seemed to Rufus that Alyssum might be more than an interesting curiosity of botany. It might be a valuable tool in remediating pollution. “I realized,” he said, “we might be able to convert this hyperaccumulating weed—because it’s a weed until you say it’s a useful plant—into something that could decontaminate soils or mine nickel from soils that otherwise aren’t any good for agriculture. That was very exciting.
“It became a case for classic agronomy. We found out the fertility needs of our weed, worked out its genetics, and bred to improve it. Since most of the nickel is in the leaves, we selected for those individuals that hang on to their leaves late in the season. We also worked on increasing its yield of foliage and making it taller so standard farm equipment could harvest it. Then we field-tested our cultivars. Not only was it a success; we had an immediate use for the results. In Georgia, pecan trees die because of nickel deficiency. So, we made an extract of the leaves and used it in a foliar spray, and pecan farmers have found it’s a wonderful cure. You can also just spread ground-up Alyssum on the soil. You only need to apply a couple of grams of nickel per hectare as a spray, and if you do, you solve the deficiency problem for years. What’s more, we can grow this nickel more cheaply than a farmer can buy nickel sulfate.”
Rufus leaned forward in his government-issue desk chair. “Then there’s the mining opportunity. You grow the crop on nickel-rich soil, then harvest the plants just after they flower, but before they set seed. You cut your crop like hay, bale it like hay, and take it to the biomass energy facility. Then you put the ash into a smelter, and eighteen minutes later”—he leaned back in his chair, and smiled—“you pour out liquid nickel. It’s the richest, best nickel ore anyone has ever found.”
Every year the United States imports about 125,000 tons of nickel at a cost of about $2.5 billion for use in stainless steel and other alloys, in batteries and electronics, and in construction. Alyssum can produce about 350 pounds of nickel per acre of serpentine soil, which means, Rufus says, that U.S. farmers could grow about half the country’s annual needs. Since it costs about one hundred dollars an acre to grow Alyssum, farming nickel on otherwise useless land could be an excellent business proposition.
So why haven’t I heard of nickel farming?
That, Rufus said, is the big mystery. In 1998, USDA, the University of Maryland, and several scientists, including Rufus, were awarded a patent for nickel phytoextraction using these Alyssum cultivars. The patent holders promptly licensed the technology to Viridian Resources LLC, a small Houston-based company, with the understanding that it would commercialize the process. Viridian ran some trials at a smelting facility owned by Vale (formerly the International Nickel Company, or Inco) in Ontario that had nickel-polluted acreage. Vale was pleased with the results, but didn’t want to move forward until it settled some outstanding lawsuits related to the pollution, which had occurred many years earlier.
“Viridian got five million dollars from Inco to further develop the application at their locations overseas—Indonesia, Canada, and Britain—and they were asked in Brazil to go full speed ahead. But nothing happened.”
“Why not?” I asked.
“God only knows,” Rufus said. “I’m infuriated. Just think about what this could mean in poor countries like Zimbabwe where they have lots of serpentine soils. They could take otherwise useless acreage that can’t grow food and phyto-mine nickel out of it for a profit. Plus, they could then actually farm that land.”
Rufus explained that serpentine soils not only have too much nickel, they also have too much magnesium and not enough calcium and phosphorous. Although many plants can tolerate soils with low calcium and low phosphorous, very few can do it if there is also high magnesium. It’s another revolving-door problem: Magnesium elbows its way into the calcium membrane transporter and prevents the passage of calcium. Without sufficient calcium, cells can’t be created or divide. The few plants that are able to grow on serpentine barrens have evolved transporters that are either particularly efficient at passing through calcium or are less likely to admit magnesium. They are also more efficient at taking up phosphorous.
“So,” Rufus continued, “if Zimbabwean farmers mined nickel with Alyssum, it would make economic sense for them to add phosphorous and calcium to the soil because doing so would maximize the Alyssum and, therefore, the nickel yield. Then, after they’ve extracted the nickel, the serpentine soil has been fully enhanced and you can grow whatever you want afterward.
“In Indonesia,” he added, “people are thinking that you could use it on mining sites. When they mine nickel there, they strip off three to ten meters of topsoil and subsoil, cart it away, do their mining, and then bring the soil back to ‘re-green’ the site. A lot of that soil has enough nickel in it to be valuable. You could spread fertilizer on it, grow Alyssum, and then finish off by farming it. Everyone benefits. But Viridian has been doing absolutely nothing with the patent, so none of that is happening.”
Later, I tried to reach Viridian, but the CEO never returned my calls or emails. An Internet search revealed a story, though.
In the fall of 1998, Viridian leased some fifty acres from the airport authority in Josephine County, Oregon, and under an agreement with the County Board of Commissioners, planted the fields with Alyssum cultivars. In 2002, the company reported that the leaves were accumulating large amounts of nickel, as expected.
Then, in 2005, for reasons unknown, Viridian failed to harvest on time, and mowed the fields after the flowers had not only bloomed but gone to seed. The company also left bales of harvested plants, which were full of seeds, piled in the fields. By 2008, Alyssum was found at sites far beyond the airport, including on protected properties of the U.S. Forest Service and the Nature Conservancy. The County Board ended the lease with Viridian and demanded the company spray herbicide on the Alyssum. The spraying was only partially successful, and the next year the Oregon Department of Agriculture (ODA) dispatched workers to attack the plants again, pulling them out by hand when necessary. The ODA classified Alyssum murale and Alyssum corsicum as Class A noxious weeds, noting that these European natives are so well suited to serpentine conditions that they threaten to outcompete and overrun unique indigenous flora, including endangered native species that evolved to live only on the serpentine barrens. The cultivars’ special vigor, unusual size, and their strong, perennial root systems make them exceedingly difficult to eradicate, although the Forest Service, the ODA, and a corps of local volunteers are still working hard to do so.
Rufus later acknowledged that the Alyssum has become a problem in Oregon, but he blames Viridian for failing to cultivate it according to the agreed protocol. If harvested before or even while in flower, he pointed out, the plant has no ability to spread. This is true, but I find it easy to imagine that on a large-scale nickel farm an occasional plant might go to seed prematurely. It could be that the question of phyto-mining nickel will be like other difficult choices we make between economic value on one hand and sensitive ecosystems or rare species on the other. Sometimes the choices are not very palatable. Is it better to employ roots to gently search the soil for nickel even if it also means risking a special habitat? Or is strip-mining the earth elsewhere better? Maybe a choice won’t be necessary. The patents that Viridian now licenses will expire in 2015. Then Rufus and others will try to breed a sterile cultivar, one that doesn’t produce viable seed. Although Rufus will probably never see any royalties from his years of research, he does hope to see Alyssum put to work in remediating nickel-polluted soils.
Although Rufus has not been directly involved with the arsenic-gathering brake ferns, he was instrumental in their story. In the late 1990s, Dr. Lena Q. Ma, an expert in geobiochemistry at the University of Florida, was investigating arsenic contamination of Florida soils and groundwater. At Rufus’s suggestion, she searched for species that flourished on the inhospitable grounds of chemical companies, wood treatment facilities, cattle dip stations, incinerators, dumps, and other arsenic
-polluted sites. At a facility in central Florida that treated lumber with chromated copper arsenate, a substance once used (but now banned) to make wood resistant to termites, she found the brake fern growing in lacy profusion. Investigating, she found that the plants were sequestering arsenic in the vacuoles of its fronds. The arsenic gained entry to the roots through the revolving door of the phosphorous transporter. Like nickel in Alyssum, the arsenic benefits the fern by acting as a potent insecticide. It was Ma’s discoveries, inspired by Rufus, that enabled Edenspace to, beautifully, clean up Spring Valley.
twelve
The Once and Future Wheat
The average midwestern farmer tills his fields at least once a season. In the spring, his plow slices through the topsoil, turning the top a few inches to the side to create furrows. Plowing uproots the remains of last year’s crop, breaks up fungus-carrying leaves, destroys emerging weeds, and exposes the soil to air, which releases a flush of nutrients. A few days later, after the soil has dried, the farmer may return with a harrow, a piece of equipment with multiple discs or tines that breaks up dirt clods and further aerates the surface of the field. After harrowing, he often disturbs the soil once more, running a cultivator across the land to incise a pattern appropriate for the seeds to be sown.
There are hazards to all this soil disturbance. Mycorrhizal networks are destroyed. Rich topsoil, loosened and sitting exposed on the ground, dries out and is liable to blow away in the wind. On sloping land, rain washes the loose particles downhill. Such soil disturbances and the inevitable erosion, it has been convincingly argued, led to the downfall of the ancient Mesopotamian, Greek, Roman, Mayan, and Incan empires. In nineteenth-century America, farmers plowed under prairie grass in a hundred-million-acre area in the Oklahoma and Texas panhandles and nearby Kansas, New Mexico, and Colorado counties, planting wheat and other crops in its place. From 1934 to 1937, the region was hit by sustained drought, few crops grew, and high winds scooped up 75 percent of the region’s topsoil and airmailed it to the Atlantic Ocean. Around the world today, according to experts at the University of California, roughly seventy-five billion tons of topsoil blows away or washes into oceans, lakes, and rivers every year. About seven billion tons comes from the United States. It takes about 250 years for weathering from rocks and organic decay to create a single inch of soil. According to a recent Cornell University study, farming is eroding topsoil in the United States ten times faster (and in China and India, thirty to forty times faster) than nature creates it. In a world that will probably need to feed an additional three billion people by the end of the century, erosion is a global crisis.
The fundamental problem is that modern farming is based on species whose life cycle is complete in one growing season. Most of our edible species—grains like wheat, rice, and corn; legumes like soybeans and alfalfa; and oilseed crops like canola (a rapeseed cultivar) and sunflowers—are annuals. Annual crops cover about 80 percent of the world’s farmland and provide 80 percent of the world’s calories. This means a global cycle of tilling, seeding, harvesting, and then tilling again the following spring.
This is a most unnatural situation. Without human intervention, most of the world’s farmable landscape would be covered by perennials, plants that live for years, and produce new growth primarily from the same, deep root systems. More than 85 percent of North America’s native species are perennials. The vaunted fertility of the Great Plains’ tall-grass prairie, where topsoil could be as deep as nine feet, was created by perennials. The wild prairie was tremendously productive, supporting a rich diversity of insects, birds, and mammals (including millions of bison) while never requiring herbicides, pesticides, added water, or fertilizers, and all the while banking carbon and mineral nutrients year after year. Now, less than 4 percent of our native prairie remains.
Today, some scientists and plant breeders are making the case that we should re-create a landscape where perennials prevail. If, they argue, we develop deep-rooted perennial versions of our familiar annual crops, we will protect dwindling topsoil, use far less irrigation and fertilizers, save on the fuel required to make nitrogen fertilizer and run farm equipment, and open up marginal lands to agriculture. It is a compelling vision, which is why, in early March, I am driving west from the Kansas City airport to the Land Institute in Salina, Kansas. The Institute, a nonprofit organization founded in 1976 to promote sustainable agriculture, focuses on research and breeding to develop perennial versions of our annual grain and oilseed crops.
I meet my host, Dr. David Van Tassel, in his office in the Institute’s research building. David is a rugged man in his early forties wearing a flannel shirt and sporting a stubble of reddish whiskers that reminds me of the stubble in the desolate fields outside. When I rue the fact that I am here in late winter when there is little to see outdoors, he assures me this is the best time for him to entertain a visitor. Right now, he is limited to running experiments in the Institute’s modest greenhouse. In a few months, he will be busy outside cultivating, monitoring, and measuring thousands of field-grown sunflowers and bundleflowers, which are the focus of his research.
David proposes we go downstairs to start our tour of the greenhouse. But as we approach the stairs, I am stopped short by a color photograph that spans the height of the stairwell we are about to descend. Pictured life-sized and side by side are the root systems of two plants. The roots of the one on the left are six inches wide at soil level and taper down to a point at about three feet. The roots of the plant on the right form a nearly solid column eighteen inches across and nearly nine feet long. The plant on the left, David tells me, is winter wheat (Thinopyrum hibernum), the annual crop that farmers in the region typically sow each September and harvest in May. The plant on the right is intermediate wheatgrass (Thinopyrum intermedium), a wild perennial native to the Great Plains. (This is not the wheatgrass sold in health food stores, which is simply sprouts of an annual wheat.) The wheatgrass’s roots look like the impenetrable waterfall of beard on R. Crumb’s cartoon character Mr. Natural. In comparison, the annual wheat’s roots look like the ends of an old man’s Fu Manchu.
Once I cease exclaiming about the astonishing difference between the plants in the photos, David tells me there’s more to the matter than appearance.
“You have to remember that annuals’ roots only reach that three-foot length shortly before they begin to die. Even more important is that annuals’ roots are not in the ground for much of the year. The way we grow wheat around here, for about nine months of the year the ground is either bare or just seeded, and there aren’t any roots in there at all.”
The wild wheatgrass root system, on the other hand, stays in place all year. Its roots reach far more pervasively through the soil to access more water and nutrients than annuals’, enabling them to grow on more marginal land. The perennials also corral more phosphate and nitrate fertilizers, which otherwise easily leach out of the soil and pollute groundwater or cause excessive algal growth in lakes and ponds. In fact, perennials capture twice as much of applied fertilizers as annuals do.
Because perennial roots and their mycorrhizal partners merely slow down or go dormant in winter, the plant is ready at the first hint of spring to send up new stalks. Wheatgrass is up and busy photosynthesizing in full force many weeks before the stalks of a newly sown annual variety appear. It stays green even after its seeds fall, continuing to manufacture carbohydrates. Some of those carbohydrates are stored in the roots, which, like soup kitchens, dole out a certain percentage to feed the multitudes of organisms in the rhizosphere. Those burrowing, digesting, and decomposing creatures create the granular texture of good soil and, at their deaths, build its fertility. That fertility in turn supports plants and a diverse aboveground ecology. And, of course, perennials’ roots are active year-round in holding soil in place.
So why, I ask, aren’t all our grain crops perennials, especially given that in the wild they are so much more prevalent than annuals? The quick answer, David says, is that annuals
tend to channel more of their energy into producing more and bigger seeds—the part of the plant we use for food—than perennials do. A fuller answer awaits us downstairs.
At the door to the greenhouse, I look into a sea of six-foot-high grasses with their green stalks and narrow, bladelike leaves. All the plants are growing in ten-gallon black pots and all the pots are arranged, rim to rim, in shallow metal trays. Right now, the trays have only a little water in them, but in a few hours they will be flooded so the plants can absorb water from their roots. Grow lights hang over the plants, but at noon on this sunny day, they are outshone by natural daylight.
Narrow aisles separate the trays, and we sidle into the wheat section. “In this section,” David says as we proceed crabwise, “we’re crossing annual winter wheat and wild perennial wheatgrass. Because each seed has its own particular genetic inheritance, any cross between two parents are going to produce a wide range of hybrid individuals. It’s a roll of the genetic dice: Some individuals are going to be almost like wheat, others almost like wheatgrass, while most will fall in a bell curve of intermediate traits.”
He stops and bends a sturdy stalk toward me that has, at about my eye level, a curving seedhead packed with plump, pale golden brown seeds nearly the size of rice grains. The tip of each seed has a long, stiff hair, called an awn. (The awn probably makes it harder for birds to land and snatch the grain.) “This plant,” he says, “is very close to the annual species. If this plant were growing outside, this is how it would look in May, right before harvest. You can see how large the seeds are, and that they’re all still on the head.”
A Garden of Marvels Page 11
