The amount of carbon that can be restored in the world's degraded agricultural soils will directly influence global food security and climate change within our lifetime, said Rattan Lal, author of the article and director of the carbon management and sequestration center at Ohio State University.
Scientists estimate that, since the mechanization of agriculture began a few hundred years ago, some 78 billion metric tons more than 171 trillion pounds of carbon once trapped in the soil have been lost to the atmosphere in the form of carbon dioxide (CO2).
"Converting natural ecosystems to fields for crop production and pastures depletes a soil's carbon content by as much as 75 percent," Lal said. "And the amount of carbon we emit into the atmosphere each year from industrial activity is on the rise."
With too little carbon in the soil, crop production is inefficient. Right now, the world's agricultural soils are alarmingly depleted of carbon, particularly in sub-Saharan Africa, south and central Asia and the Caribbean and Andean regions, Lal said.
He calls for adopting "recommended management practices" for increasing and keeping carbon in farmed soils. These practices include no-till farming leaving residue from the previous year's crops on the field; agroforestry planting trees or shrubs on or around cropland to enhance the quality of the soil; planting cover crops, which protect the soil from erosion during normal growing seasons; and using nutrients such as manure, compost or biosolids to fertilize crops.
Evidence shows that following such practices greatly increases and sustains crop yields.
Lal cited an 18-year experiment in Kenya: Farm fields managed by regular farming practices tilling the land, using no fertilizer, leaving fields
Contact: Rattan Lal
Ohio State University