COLUMBUS -- The quantity and quality of the world's soil will not meet future food demands if the population continues to grow at its current rate and efforts are not taken to improve soil conditions, cautions a soil scientist at The Ohio State University.

"I tell my students that 'In soil, we trust,'" said Rattan Lal, a professor of soil science in Ohio State University's School of Natural Resources. "It's time that we as a community give proper respect to what we call dirt."

A specialist in soil degradation and carbon sequestration (keeping carbon in place in the soil), Lal argues that two key 21st century concerns -- global food security caused by a rapid increase in world population and increases in atmospheric greenhouse gases -- are linked to soil quality, especially in relation to soil carbon. The quality and quantity of carbon in soil affects soil's support of terrestrial life through such processes as ecosystem restoration, water purification and pollutant detoxification, among others.

Lal has worked with colleagues around the world to assess the potential for agricultural practices that would improve soil quality and, at the same time, reduce emissions of carbon dioxide into the air.

He recommends a variety of agricultural practices, including conservation tillage, precision farming and growing cover crops, to keep carbon in the soil, thus improving soil productivity and reducing the release of carbon into the air. He estimates judicious land use and soil management techniques could resequester 60 percent to 70 percent of the historic carbon loss of 80 billion to 100 billion metric tons of carbon.

The increase of atmospheric carbon dioxide is occurring at the rate of 3.3 billion metric tons per year. In addition to fossil fuel combustion, the increase is caused by soil cultivation, biomass burning and deforestation. Further declines in soil quality from erosion and nutrient imbalance cause even more gaseous emissions -- including methane and nitrous oxide, Lal said.

Before the 1970s, more carbon was emitted into the atmosphere from soil and agricultural activity than from fossil fuel combustion. Now, agricultural activities are responsible for about 25 percent of global emissions.

In the United States alone, carbon sequestration could affect 212 million metric tons of carbon per year, or about 12 percent of the total carbon emissions. 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 said.

Increasing soil carbon also has other societal benefits: resisting erosion, reducing the transport of pollution-laden sediment into water, decreasing downstream flooding and lowering the release of particulate matter into the atmosphere -- which decreases the risks of global warming.

"It's truly a win-win strategy," Lal said.

However, the use of cropland to reduce atmospheric carbon levels is not a permanent solution to the problem. Soil can hold only so much carbon, and with appropriate agricultural practices it will be filled within 25 to 50 years, Lal said.

"This isn't a substitute to finding alternatives to fossil fuel usage," he said. "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. This is not 'the' answer, but it is an important temporary solution."

Though the water and air quality concerns are high priorities, Lal emphasized that world hunger -- already a problem for 790 million people globally -- will intensify if agricultural productivity is not improved.

Concerns about food availability are particularly high in developing countries, where almost 97.5 percent of the estimated annual population increase of 73 million people is expected to occur, Lal said. Malnourishment in these areas is intensified in cases where crops and animals are raised on degraded soils missing many nutrients -- among them, zinc, copper and iron.

"There are not many troubles in the world more alarming than those caused by an empty stomach," he said.

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(ST/LO)