What is in this article?:
- Healthier soil can reduce nitrogen costs, offer drought tolerance
- Organic matter helps “drought-proof” crops
No-till veteran Dan DeSutter, Attica, Ind., has used cover crops for 15 years; mostly cereal rye, with some mixes. Besides anchoring soil and building carbon and nitrogen, he values cover crops for the sunlight they capture to keep carbon in the soil.
“Over the last 100 years, we’ve lost half of the organic matter that our soils had before the introduction of widespread tillage,” he says. “It’s easy to figure out what that level could be – sample a fencerow that’s never been touched.”
Landlords have come to appreciate him building their soil.
It all started by fixing tile about 15 years ago.
Dan DeSutter was working in a Purdue ryegrass demonstration plot on his Attica, Ind., farm. While digging a trench and repairing the tile, he noticed what the ryegrass roots had done for the soil.
“No piece of steel could ever do what that annual ryegrass had just accomplished between cash crops, which was to pierce a series of macropores through compacted layers 4 feet deep,” DeSutter says.
After that, he quickly incorporated cover crops into the rest of his operation and has used them since 1999. Currently, he plants cover crops on all 4,400 acres, except where he’s working on drainage.
One primary goal has been to increase the soil’s organic matter to its native level – where it was before anyone worked the land. “Over the last 100 years, we’ve lost half of the organic matter that our soils had before the introduction of widespread tillage,” he says.
“Soil organic matter is composed primarily of carbon from roots rather than surface residue,” he says. “In order to rebuild organic matter, we must refrain from tillage, which oxidizes existing organic matter into the atmosphere, and grow as many tons of roots as possible. It’s easy to figure out what that level could be – sample a fencerow that’s never been touched,” he says.
The economics of cover crops are tied directly to the amount of organic matter, DeSutter says. With his background as a financial analyst and commodity broker, he easily did the math, connecting percentage of organic matter with water-holding capacity, the amount of soil N and yield.
No-till can increase organic matter by 0.1 % each year – 1% in 10 years, he says. “With the addition of cover crops, that number could improve to 0.2 % per year,” DeSutter says. “Potentially, cover crops could add 1% of organic matter in as little as five years, he believes. Weather conditions, crop rotation and initial organic matter levels all play a role in the rate of increase.
That 1% organic matter can make a huge difference in the nutrients and water available to a cash crop, DeSutter says. For example, 1% of organic matter in the top 12 inches contains 1,000 pounds N per acre. On average, 3% of that N is mineralized, which results in 30 pounds N per acre becoming available to a crop year.
Long-term no-till and cover crops have helped add 2% organic matter on some of his farms resulting in an additional 60 pounds of “free” N per acre, he says. If N is $0.50 per pound, that equates to a savings of $30 per acre, he adds.