What Helps Organic Soils Store More Carbon?

Boosters of organic food often say the practice, which rejects synthetic fertilizers and pesticides, is a good method for curbing climate change because it stores more carbon in the soil. But aside from anecdotal observations, no one could really explain the dynamics behind why organic fields keep more carbon underground than conventional ones.

Robertson, a researcher at Michigan State University's Kellogg Biological Station, thinks he might have an answer: a chemical group called phenolics, a class of complex compounds that also protect plants from disease and pests.

“It's only by elimination that we're left with the chemical explanation,” Robertson said. He believes phenolic compounds enter the soil when farmers plant cover crops like beans and legumes that enrich the soil with nitrogen before planting. These compounds create a barrier around the carbon in the soil, protecting the carbon from microbes that process it into carbon dioxide gas. While organic farmers are not the only growers who use cover crops, they rely on them much more than conventional growers.