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Corn+Soybean Digest

Healthier soil can reduce nitrogen costs, offer drought tolerance

Think different 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.

Organic matter helps “drought-proof” crops

Since he’s started using cover crops, DeSutter has seen a more drought-proof crop. Water-holding capacity is improved with each percentage of organic matter increase, DeSutter says. “Text books will tell you that each percent of organic matter equates to roughly 16,000 gallons of water storage in the top 12 inches per year,” he says.

The extra water can be valuable in times of drought, especially in late summer.

“A 2% increase in organic matter is equivalent to a 1¼-inch rain in August,” DeSutter says.

Depending on the season, this extra moisture can be worth 20 bushels of corn or more. In wet springs, rapidly growing cover crops can be used to wick moisture from the soil allowing for timelier planting.

“Cover crops give us the ability to weather both dry and wet extremes,” DeSutter says. “We’re building a robust system that isn’t as fickle as Mother Nature.”

The system that works for DeSutter won’t necessarily work for someone in a different region, he notes. “It’s all about the system you can build to work within your environment, rainfall, soil types, growing season and crops you raise.”

Understanding the costs and benefits of different crops and timings is important; most of DeSutter’s cover crop failures resulted from winter kill and/or late planting. That’s why cereal rye is his staple cover crop, as it can be planted late in the fall, reliably survives winter, is easy to kill and can control weeds.

DeSutter also mixes buckwheat, crimson clover, ryegrass, oats and radish when appropriate.

He drills about 90% of his cover crops; that’s been the most efficient method for him. Planting needs to happen as soon as possible after the cash crop is harvested: July (after wheat) through Nov. 1 (after corn harvest); a challenging season during a peak labor time of year.

Roundup is the primary cover crop terminator.

His preferred fertilizer is neighbors’ hog and chicken manure. After applying manure, DeSutter relies on cover crops to keep N in the system.

Nitrogen isn’t all that cover crops retain in the system – they also keep carbon in the soil by harvesting sunlight. DeSutter says that corn and soybeans are only effectively using sunlight for 90 days.

“The sun is our free resource, and every day that we don’t have a solar collector crop collecting energy and using that to inject carbon into soils is a lost opportunity,” DeSutter says. “Follow that simple idea and good things happen.”

“Obviously, this makes sense on farms that we own. As our landowners have come to understand that we are improving their soil resource rather than depleting it, they have become enthusiastic supporters of no-till and cover crops as well.”

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