"There's a lot of gray areas where we have incomplete knowledge here, and it's not because of lack of research," she said. "We need to develop a more complete understanding of how the soil microbial community is functioning and the processes that control and drive whether or not carbon is stored."
On Wednesday, Agriculture Secretary Tom Vilsack spoke of the importance of cover crops to maintain fertile soil, control erosion, hold moisture and store carbon. Although farmers recognize the importance of cover crops, many are reluctant to use them because of concerns that growing them might conflict with crop insurance rules. Vilsack announced the rollout of new cover crop guidelines to encourage farmers to use them.
Storing carbon in soils could also help farmers cash in on carbon credits, providing an extra income for growers who take care to maintain carbon in the ground. Last year the Verified Carbon Standard approved the first soil offset program for a World Bank-run effort in Africa. In Oklahoma, the state's conservation commission runs a carbon program that pays farmers up to $3.50 per ton of carbon sequestered.
But without the lure of additional income, keeping soil rich with carbon is not a priority for most growers.
"The incentive is for the farmers to strip mine the soil; that's the cheapest, fastest way to get a buck," said Daniella Malin, project manager of the Cool Farm Institute, a program on agriculture and climate under the Sustainable Food Laboratory. Malin works to finds ways to monetize low-carbon agriculture through the use of carbon markets.
Organic agriculture doesn't lower N2O emissions
Malin says she does not favor organic agriculture over conventional when it comes to choosing the best method for curbing climate change. But the practices that enrich soils with carbon tend to be adapted more heartily by organic farmers. Compost, or the decayed remains of plants that are used to amend the soil, tends to add a more stable source of carbon, for example.
Nevertheless, there are reasons why organic agriculture can be a worse option than conventional growing for keeping carbon dioxide out of the atmosphere. Yields tend to be lower for organics, meaning one needs more land to grow the same amount of food.
Overall, the information on how to quantify carbon has been lacking. "The carbon footprint has been guessed at the farming level," Malin explained.
But although organic practices may be winning in the race for low-carbon agriculture, they seem to fare no better than conventional crops for another, more nefarious greenhouse gas: nitrous oxide.
Nitrous oxide (N2O), or laughing gas, has a global warming potential 200 times that of carbon dioxide. About 80 percent of nitrous oxide emissions come from agriculture, as nitrogen-based fertilizer bonds with oxygen and is released as a gas.
As it turns out, organic fields, enriched with cover crops, emit just as much nitrous oxide as conventional crops that rely on pungent ammonia-based industrial fertilizer.
"The microbes producing it don't care where the nitrogen comes from, a fertilizer factory in the Gulf Coast versus a legume that has fixed the nitrogen last spring," Robertson said. "All they care about is what's there, and they'll go to town regardless."
This story was made possible in part by a fellowship from the Institutes for Journalism & Natural Resources.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500