CHURCHVILLE, Va. -- The world's farming has been unsustainable for 10,000 years because of soil erosion. Until now. In the past two decades, modern high-yield farming has discovered how to radically cut soil-erosion rates and shown the world how to produce food for billions of people while building topsoil faster than it erodes.
Throughout agricultural history, mankind used "bare-earth" farming systems to control weeds. We plowed and left newly turned soil open to wind and water for the whole winter. Or we fallowed (left the fields unplanted, so we could destroy any weeds that sprouted). But fallowing left the field open to the elements for a whole year. As recently as the 1930s, great clouds of dust floated high over U.S. cities from the abused soil of America's Great Plans.
In the tropics, soil erosion has been even worse. High soil temperatures literally burn up the organic matter in the soil, leaving it without structure to resist erosion when the rains come. No wonder the environmental movement has been terrified at the thought of 10 billion people, most of them living and eating in tropical climates.
High-yield farming has now given us new answers to soil erosion. With the help of hybrid seeds, chemical fertilizers and pesticides, the world has trebled the yields on its best farmland. That cuts the critical measure of soil erosion, the amount per ton of food produced, by two-thirds.
In the past two decades, chemistry has given us another big weapon. Weed killers that let farmers invent a new farming system called "conservation tillage" that cuts soil erosion 65 to 95 percent. With chemical weed killers, we don't need to plow most soils. We can just disc the crop residue into the top few inches of topsoil, creating billions of tiny dams against erosion.
In the most radical form of conservation tillage, called "no-till," the soil is never opened to wind or water. Instead, a sod cover is planted before the previous crop is harvested, and the blanket of sod protects the soil until the farmer is ready to plant the new crop. The farmer sprays a chemical to kill the blanket a couple of weeks before he plants the new crop seeds through the dead sod.
America is now using conservation tillage on more than 100 million acres, including virtually all the high-risk land being cropped. The new tillage systems are also spreading widely in Europe, Latin America, Australia -- and are even working in Africa.
An Iowa woman recently told me she knew we were destroying America's cropland because Iowa's rivers ran brown. But Iowa's rivers ran brown when bison roamed the state. Erosion can't be stopped, though it can be slowed to below the rate at which topsoil is created. That's what conservation tillage does.
Conservation tillage also saves soil moisture because it never exposes the moist subsoil. It is already helping to avoid dust-bowl conditions in dry years on much of North America's wheat land. What's more, it provides a more favorable subsoil climate for earthworms and soil bacteria. (Soil microbes hate being plowed.)
Organic farming, unfortunately, doesn't have such good answers to the soil-erosion problem. Organic yields are only about half the yields on chemically assisted farms because fertility levels are lower and pest losses are higher.
The Third World's traditional farming is even worse. Traditional farmers may get only 5 percent of the yield of a modern farming system, and they lose huge amounts of topsoil to erosion.
We should feed tomorrow's world by maximizing the yields on the world's safest soils, wherever they are. The poor soils (which harbor three-fourths of our wildlife species) should be left to nature, wherever they are.
No longer the 15th century
Food self-sufficiency is no longer a very important concept. This isn't the 15th century, when a food importer had to depend on uncertain winds to slowly deliver wooden sailing ships while weevils ate their cargoes. Nor is importing food much of a financial hardship when most of the Third World is growing at 6 to 10 percent a year.
The planet can now be saved from famine. Still higher yields can produce the food we'll need from the good acres we're already farming. Conservation tillage can protect the soils while we do it. And free trade in farm products can protect the erosion-prone tropical acres that harbor most of the world's wildlife from being farmed at all. Food production can be fully sustainable for the first time in human history -- even though Iowa's rivers still run brown.
Dennis T. Avery is editor of the Global Food Quarterly and was formerly the State Department's senior agricultural analyst.
Pub Date: 8/27/96