The sustainable agriculture

The case of no-till agriculture

GMO resistant to pesticide in no-till agricultre

(modified from: Nina V. Fedoroff and Nancy Marie Brown - Mendel in the kitchen - The National Academies Press, 2004)

Challenges of today farming

In May 2002 the United Nations Environment Programme released a report on environmental trends. The New York Times account stated: “Expansion of cities, destruction of forests, erosion of fields, and rising demand for water are likely to threaten human and ecological health for at least a generation.” The growth of agriculture “is damaging landscapes, depleting aquifers, raising the level of salt in the soil, and reducing habitat for wildlife.” The Times continued, “The report says an important cause is the accelerating growth of vast, poor, and largely unplanned cities in developing countries, most of them near coastlines.”

These sentences underscore the need for an agriculture that truly conserves both water and land—and still grows more food to feed the growing cities. The acreage of land under cultivation worldwide has remained the same for almost half a century. Most of the best agricultural land is already being farmed. On balance, additions—such as acres cut out of the Amazon rainforest for subsistence farms—are canceled by the loss of prime farmland to urbanization in some places and to desertification and salinization in others.

Europe and United States currently has a surplus of food, and farmers are paid to take land out of production. But Avery, a former USDA official, has written, “The world has no ‘surplus’ of farmland, in the U.S., in Western Europe, or anywhere else. The world must virtually triple its farm output in the next 40 years. Inevitably, surplus food stockpiled in America means plowing down more wildlife in some other country.” Efforts to protect wildlife and wilderness in other ways will eventually cause conflict.

The Green Revolution (the new crop varieties and expanding fertilizer use from the 1960s to the 1990s) has had its ecological downside. Pest and disease outbreaks have been an especially severe consequence due most often to a combination of factors—higher nutrient levels, narrow genetic stock, uniform continuous planting, and the misuse of pesticides. Erosion and salinization (from too much or improperly designed irrigation) have also been blamed, often legitimately, on the intensive farming practices of the Green Revolution.

When farming methods are not ecologically wise, Conway argues in The Doubly Green Revolution, “agriculture is both culprit and victim.” The human population of the earth was about a billion and a half at the turn of the twentieth century. It is more than six billion today. It is expected to be more than eight billion by 2050. The Great Plains of America and the steppes of Russia are already being farmed. New land could be put under the plow, but arable land is not evenly spread over the globe. More than 90 percent of potential new farmland is in Africa and Latin America. Two countries—Brazil, with 27 percent, and Zaire, with 9 percent—account for more than a third of it. In South Asia, a center of population growth, almost half of the potential farmland is already occupied by cities and towns.

More than half of the people alive today live in cities, with little prospect of growing their own food. By 2020 that proportion will reach 60 percent.

Today discussions of farming methods must take into account the environmental consequences of expanding the food supply further. New land put under cultivation is land taken away from the dwindling wildlands that are the planet’s ecological underpinnings—providers of what are called ecological services, such as the underground supply of clean water, climate regulation, and a home for wildlife. If we choose to preserve these, we must ask where the food will come from to feed the still growing human population. If we want everyone to eat as well as today’s average American, we must increase our production of food by more than 400 percent.

Thus our challenge for the twenty-first century is to substantially increase our food supply on roughly the same amount of land in production today while simultaneously ameliorating the impacts of intensive farming and putting it on a sustainable basis. Reaching this goal is likely to require improving every aspect of our current agricultural practices—and inventing new ones as well. Yet Ken Cassman, an agronomist at the University of Nebraska, warns that conventional plant breeding and farming methods are already approaching their maximal yields in some places in the world. Moreover, the extreme polarization of current discussions about organic and conventional farming methods stands in the way of using the best of both. We have few unbiased scientific appraisals of competing methods. The notion that valuable insights can be gleaned from both conventional and organic approaches and combined is almost unthinkable—right now—as is using molecular methods to increase yields and protect crops from diseases and pests (E1, E2).

Top

The sustainable agriculture

Klaus Ammann, curator of the Botanical Garden at the University of Bern in Switzerland, is among the many who believe a compromise could—and must—be reached between organic farming and the new methods in agriculture. In 2003 he produced a report on biodiversity and agricultural biotechnology for the Botanical Garden at Bern. His conclusion is: “We need organo-transgenic crops. We need to make peace with the people in organic agriculture. We need an ecotechnology revolution.”

At the annual meeting of the American Association for the Advancement of Science (AAAS) in 2003, Ammann was asked how scientists could encourage both biotechnology and organic agriculture. He answered, “There’s ideology on both sides. In Europe it’s just cheap marketing to be GM-free. But to build your marketing on a negative has no future. The next generation of transgenic crops may be more interesting to organic farmers.”

Plant pathologist Jim Cook was asked, also at the AAAS meeting, how scientists could encourage biotechnology and organic agriculture at the same time. He replied, “We in the scientific community must never let the divide between the two drive our research.” Cook is an adherent of sustainable agriculture, although he admits that even this relatively new term has “taken up all sorts of baggage” and become politicized. To Cook it means an agriculture that is dependent on natural biological cycles, one that places a high value on such resources as soil, water, and energy, on the components of fertilizers, and on genetic diversity, and an agriculture that consciously tries to reduce the pollutants—“the dust, sediments, chemicals, gaseous emissions, and other wastes”—that farming releases into the environment. “These objectives must be met,” he stresses, “while continuing growth in the supply of safe, affordable, quality food.”

Top

The case of no-till agriculture

For more than 20 years, Cook has been studying no-till agriculture as a way for wheat farmers in the Pacific Northwest to cut erosion and to enrich the soil. Why do we plow? As T. F. Evans writes in Feeding the Ten Billion, in the past we believed that: weeds were controlled and soil moisture was thought to be conserved.” But research at the Rothamsted Research Institute in England in the 1930s showed that tilling the soil does not conserve soil moisture and that it is unnecessary if weeds can be kept down by “dust mulches” or some other means. “Indeed ploughing, that hallmark of good farming for more than a millennium, could cause substantial soil erosion,” Evans writes.

The best tillage systems, called conservation tillage, is defined by the Conservation Technology Information Center at Purdue University as “any tillage and planting system that covers more than 30 percent of the soil surface with crop residue, after planting, to reduce soil erosion by water.” Achieving this, however, meant putting up with weeds until herbicides were introduced that were effective enough to replace the plow. The first was atrazine, brought out in 1959. Glyphosate, or Roundup, was “the next major step,” Evans says, when it was released in 1974, being much less harsh than atrazine. “The reduction in soil erosion by minimum tillage can be striking,” Evans writes, “varying from twenty-to a thousand-fold across a range of environments.”

Plowing not only dries out the soil and exposes it to erosion, it releases carbon, as carbon dioxide. Carbon dioxide is a greenhouse gas, suspected to cause global warming. Plowing releases carbon into the atmosphere; no-till farming keeps it in the soil. Plowing also, said Cook, “doesn’t lead to that nice crumb structure we get when we let the process go slowly.”

When Cook first became interested in no-till in 1974, it was not a popular way to farm, even though it had been invented by what Cook calls progressive farmers. It is also known as direct seeding, because the seed and fertilizer are placed in the soil at the same time. Notably, the field is not plowed first. Planting involves one pass with a tractor towing a seeder with two tools. Said Cook, “One disk makes a slice, a zone an inch or two wide and three to four inches deep. The second disk is just a little shallower.” The first slice is for liquid fertilizer, with the proportions of nitrogen, phosphorus, and sulfur determined by a soil test. The second disc places the seed.

When a field has made the transition, as Cook put it, from a plowed field to a direct-seeded field, “the seed-drill goes through the soil easier, and the straw rots faster on the soil surface. The straw that’s left behind with one harvest disappears by the next spring.” It is what he calls “composting in place.” An acre that he has direct-seeded for more than 20 years “is organically as beautiful as it can be. The soil is mellowing out with better crumb structure. You can pull the plow through it in third gear.”

In spite of the beauty of the soil in his test plot—and the savings in labor, time, and gas from having to ride a tractor less—Cook finds it has not been easy to persuade the region’s wheat farmers that no-till is the future of farming. The Conservation Technology Information Center reports that in 1991, when Iowa farmers were asked why they didn’t switch to conservation tillage to control runoff and erosion, they answered: weeds. Other surveys of farmers have had the same result.

The biggest increase in no-till farming since 1996 has come in soybean farming. The center believes it is no coincidence that Monsanto’s Roundup Ready soybeans, genetically engineered to tolerate the herbicide glyphosate, were introduced in that year. In 2001 the American Soybean Association randomly surveyed soybean farmers in 19 states who planted 200 or more acres. They found that the number of acres being farmed with conservation tillage methods, including no-till, had jumped from 25 to 83 percent. Compared to 1996, more than half the farmers plowed less, while 73 percent left more crop residue in their fields. Why such a change? Sixty-three percent of the soybean growers said, without being prompted, that the reason was Roundup Ready soybeans. They could control weeds in their fields without plowing. In 2002, 75 percent of the soybeans planted in America were genetically engineered herbicide-tolerant varieties, the majority of which were Roundup Ready.

Top

GMO resistant to pesticide in no-till agricultre

Roundup, for which Monsanto’s patent expired in 2000, was discovered in 1971 and it is now the most popular weed-killer in the world. Every year since 1983 its worldwide sales have topped one billion dollars. It is a broad-spectrum herbicide, meaning that it kills every kind of plant Glyphosate latches on to an enzyme called 5-enolpyruvylshikimate-3-phosphate or EPSP synthase. This enzyme controls a key step in making the amino acids phenylalanine, tyrosine, and tryptophan. With glyphosate attached to it, EPSP synthase does not work: production of these three amino acids is stopped.

Roundup does not harm insects, fish, birds, or mammals (including humans) because none of these creatures have the enzyme EPSP synthase. Unlike plants, animals do not make these three amino acids (phenylalanine, tyrosine, or tryptophan) but instead take them from their food. Fungi and bacteria, including the ones in the soil to which Cook attributes good crumb structure, do contain EPSP synthase. Yet soil organisms can—and rapidly do—metabolize glyphosate, breaking it down into carbon dioxide and ammonia.

Roundup encouraged conservation tillage. But Glyphosate has no way to distinguish one plant from another, a crop from a weed. So while it could clean a farmer’s fields of weeds before planting, it couldn’t be used while the crop was in the ground.

Could Roundup be made more specific, made to target only some plants and not all of them? By 1984 Monsanto researcher Ganesh Kishore had identified a change in the enzyme EPSP synthase that would make a plant tolerate Roundup. Said Steve Padgette, a Monsanto enzymologist: “In 1986 or ’87 we had a big collection of bacteria that would degrade glyphosate. So we got the idea to screen the bacteria for EPSP synthase. We found one particular bacterial culture in which the extracts showed really good results. It had super high efficiency.”

By the end of 1988 the team had isolated the gene and created a vector with which to introduce it into soybeans. This gene, from the familiar Agrobacterium, is now found in all Roundup Ready crops: alfalfa, canola, cotton, corn, lettuce, potato, soybean, strawberry, sugar beet, sugarcane, and wheat.

Besides Monsanto’s glyphosate-tolerant varieties, other crops, known by the name Liberty, have been developed that can tolerate being sprayed with a different herbicide, a compound called glufosinate, sold as Basta, Rely, Challenge, and Finale, with a different method of action.

A third kind of herbicide-tolerant crop can withstand spraying by imidazolinone herbicides, sold as Patriot, Lightning, On Duty, and other brands.

Having three kinds of herbicide-tolerant varieties of wheat available to farmers, Cook believes, could give the same boost to conservation tillage in the Pacific Northwest that Roundup Ready soybeans did in the Midwest. Yet so far two of these varieties have stayed on the shelf, the companies choosing not to commercialize them because of political opposition to genetically modified foods. “In Washington, we’re a big wheat-producing state,” Cook explained, “and 90 percent of our wheat is exported. It’s a different kind of wheat than is grown in the Midwest. It’s low protein, only 8 to 9 percent protein. It works well in chapatis and noodles.” Wheat growers have resisted switching to no-till farming using genetically modified crops because, said Cook, “That would make our wheat a GMO, a genetically modified organism, and so far unacceptable to our international customers.”

Wheat that is tolerant of imidazolinone, however, is not genetically modified. “BASF used mutagenesis, old-fashioned mutagenesis,” Cook said. To mutate the gene responsible for the ALS enzyme, BASF exposed seeds to the chemical sodium azide. “It beats up the DNA,” Cook explained. “Some seeds will be dead, others will produce plants with all kinds of morphological changes, and if you don’t like them, you throw them away.” The next step is to spray the healthy-looking seedlings with the herbicide, throw away the ones that die, and continue growing the rest. “You compare them back to your unmodified source,” said Cook. “You look and screen and throw away, and then scale up. You don’t know how many genes have been changed besides the one targeted to make the plant tolerate the herbicide. You don’t have a clue. You might have changed a hundred, or many hundreds of genes. And unless a change can be recognized by looking at the plant, or by watching its performance in the field, it will go undetected.” An imidazolinone-tolerant wheat variety called Above, in the line known as Clearfield, was released to seed producers by the Colorado and Texas experiment stations in 2001 and by the Oregon experiment station in 2002. Having been conventionally bred and not modified by molecular techniques, these varieties are not subject to federal regulations or international conventions concerning genetically modified foods.

Cook concluded, “The principle we need to never forget is that diversity is just as important in agriculture as in the environment. This three-year combination would be so efficient you could just skip the herbicide altogether one year—the ground would be so clean.”

Ecologists have taught us that the natural environment provides many essential services: purification of the water and of air, mitigation of droughts and floods, and protection of biodiversity. Asked Cook, “Can’t we do these same things while farming the land? The answer is yes, with no-till. You improve soil structures, stop erosion, sequester carbon, improve water filtration, rather than letting it run off the land, and store more water in years of drought.” The stubble left behind provides habitat for birds and small mammals, which could lead to an upsurge in the number of their predators, including hawks, owls, and coyotes. Compared to conventionally tilled farmland, Cook considers no-till “a whole new ecology” and “a huge step toward being environmentally benign and toward contributing services with social value.” Farmers can achieve these goals, he believes, with a three-year rotation of herbicide-tolerant cereals using three different herbicides—Clearfield, Roundup, and Liberty. But they can’t do it with just one.

For further details on Ethics and economics relationships in GMO, see also: AgBioForum

Top