May 8, 2000 / AgAnswers
The quantity and quality of the world's soil will not meet future food demands if the population keeps growing at its current rate and soil conditions are not improved, says an Ohio State soil scientist.
A specialist in soil degradation and carbon sequestration (keeping carbon in place in the soil), Rattan Lal argues that two key 21st century concerns-a limited global food supply due to the increase in world population and the increases in atmospheric greenhouse gases-are linked to soil quality, especially its carbon.
Atmospheric carbon dioxide is rising at a rate of 3.3 billion metric tons per year. In addition to fuel combustion, the rise is caused by soil cultivation, biomass burning and deforestation. Even more gaseous emissions-including methane and nitrous oxide-are caused by declines in soil quality from erosion and nutrient imbalance, Lal says.
Before the 1970s, more carbon went into the atmosphere due to soil and agricultural activity than from fuel combustion. Now, agricultural activities are responsible for about 25 percent of global emissions.
Lal, who has been assessing agricultural practices that would improve soil quality while also reducing emissions of carbon dioxide into the air, recommends conservation tillage, precision farming and growing cover crops. These practices keep carbon in soil, which improves soil productivity and lowers the carbon going into the air. He estimates careful soil management could resequester 60 percent to 70 percent of the historic loss of 80 billion to 100 billion metric tons of carbon.
Through a global program of soil management, "the potential of soil restoration is enough to nullify the annual increase in atmospheric concentration of carbon dioxide," Lal says.
Increasing soil carbon also has other benefits: resisting erosion, reducing the amount of polluted sediment going into water, decreasing downstream flooding and lowering the release of particulate matter into the atmosphere-thus, decreasing the risks of global warming.
"It's truly a win-win strategy," Lal says.
However, the use of cropland to reduce atmospheric carbon levels is not a permanent solution. Soil can hold only so much carbon, and with appropriate agricultural practices it will be filled within 25 to 50 years, Lal says. Soil carbon also can easily be lost back into the atmosphere. One mistake-such as plowing once after years of no-till, can destroy 20 years of work.
"This isn't a substitute to finding alternatives to fossil fuel usage," Lal says. "What it does is provide us an opportunity to sequester carbon in agricultural soils for the next 25 to 50 years while we find viable alternatives to fossil fuels."
Though water and air quality concerns are high priorities, Lal emphasizes that hunger will intensify if productivity doesn't improve.
"There are not many troubles in the world more alarming than those caused by an empty stomach," Lal says. He adds that the best soils and the best management combined will produce optimum yields and spare marginal land for nature conservancy.
Food availability concerns are paramount in developing countries, where nearly all of the 73-million people added to the world's population yearly, are born, Lal says. Malnourishment is especially rampant where crops and animals are raised on degraded soils missing many nutrients-among them, zinc, copper and iron.
To learn more about carbon's impact on soil quality and the use of cropland to reduce the threat of global warming, check your local libraries for a book Lal wrote with several other authors titled, "The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect." The USDA commissioned the study.:
