Since 1969, select farm plots at the University of Illinois have been in continuous no-till. In that time, the measure of organic matter has been boosted more than three-fold — from about 1% to 3.2%, without use of cover crops. In the same period with rotations of corn and soybeans, the stored carbon in that soil has risen from 25,200 pounds per acre to 99,300 pounds.
It’s said that agriculture is a significant contributor to the carbon load in the atmosphere (estimated at about 8%) and that conventional tillage is largely to blame.
Mike Plumer, a University of Illinois Extension educator, who has done extensive no-till research, believes farms are a potential ally in lowering the release of carbon dioxide into the atmosphere. Plumer has also been an avid promoter of cover crops as a companion to no-till.
“Conventional tillage burns carbon and decreases organic matter,” he says. “Cover crops essentially speed the recapture of organic matter and carbon in the soil.”
Plumer points to annual ryegrass as an example.
“Its network of deep roots sequester carbon over the winter, while increasing organic matter and rebuilding soil structure more quickly than by no-till alone,” Plumer says.
Cover crops also reduce erosion, store nitrogen, mine deeper minerals and, particularly in the case of annual ryegrass, produce channels for subsequent corn and soybean crops to follow, allowing them access to deeper moisture in dry years.
In a 2-year replicated study on a southern Illinois farm where corn yields were compared with conventional, no-till and no-till with annual ryegrass, Plumer found that crop productivity increased substantially with annual ryegrass. Moreover, the yield increased as the years in no-till and cover crops increased.
Here’s a brief look at the data, collected during 2006 and 2007 seasons.
- Conventional tillage, 52.5 bushels per acre.
- Conventional 1st year, No-till (2nd) 61.5 bushels per acre.
- No-till, 79 bushels per acre
- No-till with annual ryegrass cover crop, 121 bushels per acre
In 2006 and 2007, the weather was exceptionally dry. In 2008, a more normal rainfall year, average yield on the no-till with cover crop acreage was 169 bushels per acre.
Plumer says the soil at this farm has a layer of fragipan. Annual ryegrass excels at eliminating compaction, he says. Yield differences between conventional and no-till with a cover crop would be less dramatic in a normal year.
Plumer adds that positive results like these have encouraged farmers throughout the Midwest to adopt no-till and cover crops. Government agencies including the USDA/NRCS (Natural Resources Conservation Service) are incentivizing and advising farmers, helping with conservation plans and practices to sequester carbon.