EATON, Ind. — Cover crops aren’t a new concept, but the topic has been gaining traction in agricultural news. It was also a central topic at the Tri-County Field Day for building soil health, hosted by Purdue University extension at the Russell Sheep Co. farm north of Muncie in late June.

True to its name, this kind of crop serves many functions as cover for both cash crops and earth, including fixing nitrogen in the soil for corn, loosening dirt for roots and better water-holding, weed-killing and preventing erosion. It is possible some could do double duty as cash crops to feed livestock, explained Purdue agronomy professor Keith Johnson, who specializes in forages.

But there are rules. A farmer can’t just freely turn cows out to graze a field of radishes if they intend to plant it next to an insurable commodity like corn or soybeans, or if that cover is part of a government program conservation practice, he explained.

Johnson said the USDA Natural Resources Conservation Service (NRCS) has Conservation Service Practice Standards for cover crops – for itself as well as for forage – and the Risk Management Agency has rules for acceptable risk to and use of planting ground for forage in order to still federally insure the cash crop when it is planted.

One key component of monitored grazing, for example, is making sure the livestock don’t eat too much of the cover; another is timing it so their stepping around, or “pugging,” doesn’t do too much soil compaction or other damage.

For some agronomists, cover crops go with no-till like jelly with peanut butter. Cover helps build the vertical soil structure necessary for transitioning to and using no-till at its best, according to Barry Fisher, an Indiana NRCS state soil health specialist and agronomist.

But cover can also benefit tillage systems and boost their yield. In fact, he wonders if using cover crops well and on a broader scale could be as much a “game-changer” for boosting cash crop yield as the introduction of hybrids did so many decades ago.

Right now, he said “we don’t have a very resilient system out there” for improving yield by a great deal over a short period of time. In the last 30 years, he said the United States has gained an average of 1.87 bushels per acre of corn yield each year. At that rate, the brass ring of 300 bushels is still far, far away.

By growing cover over the winter to protect soil, Fisher said it can also scavenge 50-70 additional pounds per acre of nitrogen for use in cash-crop planting that spring. When a grower applies nitrogen, he explained about half is put to work in the crop because it gets its other half from stored nitrogen in the soil.

The other, unused half of applied nitrogen goes into the soil. Ideally, it would cycle for later crop use – if there’s organic material and storage capacity in the soil to hold it. Of course, the organic matter can come from killing cover early enough in its vegetative state to release its stored nitrogen into the soil for the coming crop … and the cycle perpetuates through cover crops.

If it’s too wet to burndown the cover before planting, Fisher said a starter fertilizer can be the boost young corn needs to set properly – Russell Sheep Co. farm owner Paul Russell planted in ryegrass in mid-May and about 41 days later the crop was roughly three feet tall.

A high-carbon cover crop such as cereal rye may not be the best option to plant ahead of corn, he said, because it won’t release nitrogen in time for the cash crop. But, soybeans do well in it. Corn can use a little rye, but he said it does better with more legumes and manure.

Growing cover also increases the water-holding capacity of soil – and during last year’s drought, Fisher pointed out how valuable it would have been to many growers to have an extra inch of stored water the few times it did rain. Water stored in soil is what he calls “superwater” – more nutrient-rich than fresh rain or irrigation.

“Everyone’s trying to expand their cropping system horizontally,” he pointed out, planting more acres and spending thousands on land to do so. “I would suggest we start expanding vertically” to gain individual plant yield.

Indiana NRCS soil scientist Scot Haley, a champion of no-till, said it is supported by fungi in the soil, whereas tillage systems have more bacteria. Fungi hold soil together but also allow water to permeate and hold more in than bacterial systems, he added.

No-till soil is also home to more earthworms, which aerate it by moving around and fertilize it by eating old organic matter and turning it into useful waste for new root systems – and distributing that waste through their movement network, including vertically.

Byron Seeds Territory Manager Dennis Brown said some growers he knows have gone to no-till and, after just a few years, been able to access potash and potassium that was “locked up” in deeper soil, for their crops. “You go down four feet and you’d be surprised at the potassium levels there,” he pointed out.

As part of his demonstration, Haley dug a soil pit several feet deep near Russell’s cornfield to point out the layers. An experiment he conducted on-site to demonstrate water-holding capability was to fill two canisters with water and bend chicken wire a couple of inches down into them. Into each wire “cup” he placed a clod of soil – one from a tillage system and one from Russell’s no-till pit.

The tilled dirt burst, scattering throughout the canister and muddying the water quickly; he explained this is similar to how erosion happens in a hard rain or flooding, as the soil can’t trap any of the water and stay put. The no-till clod stayed largely trapped in the chicken wire and intact, he said, because it can absorb more of the water that surrounds it and allow runoff with less dirt going along for the ride.

Fisher agreed, citing a central Indiana farmer he knows who is converting part of his fields from till to no-till and uses irrigation.

Last year, he said the grower could only apply about a half-inch of water before the excess streamed away as runoff to his tilled ground – but the no-till fields accepted more than that half-inch into the soil.

He attested the farmer’s corn yield difference between these fields ranged from under 100 bushels per acre to more than 200, respectively.

Asked his opinion of gypsum, Haley thinks it works best on loosening really abused soil. Otherwise, he said switching to no-till should begin improving almost any otherwise fertile ground within a few years without having to spend money on an amendment.

“It’s just getting by those first couple of years,” he said, advising growers to make the transfer slowly and not all at once on their farms. “I know (waiting on the conversion to have an effect is) painful.”