Renewable Farming

This four-year project explores cover crop combinations that build soil health

As farmers gathered at a cover-crop field day Sept. 15, organizer Bob Recker explained: “Probably, your first reaction on seeing this cornfield was, ‘It’s a disaster!’ But over the next four years, experiments here could show you how cover crops can effectively build soil health, productivity — and profit.”

September 20, 2021 By Jerry Carlson   The 16-acre field just west of Janesville, IA contains replicated plots to test blends of cover crop species. It will also show how cover blends interact with corn planted in no-till 30-inch, 60-inch and 90-inch rows. The sloping field will reveal runoff behavior and water quality with varied covers.

The county NRCS conservationist staff is participating to monitor changes in the soil profile. Major goals: Measure effective ways to accelerate formation of active humus and a vibrant soil food web. And evaluate impacts on weed control, yields and eventual profitability.

Farmers kept cover crop specialist Keith Berns
answering questions for an hour. He’s co-founder and sales lead for
GreenCover, a cover crop seed firm in Nebraska.

The venture, organized by Bob Recker as Cedar Valley Innovation LLC, teams up two retired John Deere executive/engineers eager to keep their hands and minds in agriculture. Recker led advanced engineering research at the end of a 41-year career at Deere’s engineering center in Waterloo, Iowa. He retired in 2008. Bob and another Deere retiree, Graham Thompson, encouraged each other to make yet another lasting contribution to agriculture. Thompson, a strategic planning and marketing executive, offered 16 acres of sandy ground near his home west of Janesville, IA. It has a corn suitability rating of 43 on a 100-point scale. It’s surrounded by woods, pasture and hungry deer roaming bottomlands of the Shell Rock and Cedar Rivers.

As a further challenge, Recker and Thompson resolved to abstain from applied fertilizer or herbicides. There’s nothing to mask the benefits of cover crops and various corn row widths. Thus, what field-day farmers saw on Sept. 15 was corn that would qualify for disaster payments. However, cover-crop specialist Keith Berns of GreenCover, a major supplier of cover crop seed, pointed out signals to watch for among the test strips:

1. Researchers will measure buildup of biomass over four years with cover crops in varied row widths of corn. Four replicated strips of continuous corn in 30-inch rows without cover crops will provide a benchmark for organic matter buildup. These will adjoin four identical strips of corn with interseeded cover crops.

2. In corn with cover crops, Berns noted, “There’s not many weeds among the mixed cover species. They compete with weeds. And with no-till, weed seeds remain on the surface, where crickets and other insects eat them. Also, weeds really like artificial nitrate fertilizer. Natural nitrogen from legumes and other nitrogen fixers, not so much.”

3. Multiple species of cover crops support a wide array of beneficial fungi and bacteria, which accelerate digestion of stalk residue. “In our Nebraska fields with a history of covers, you won’t find many intact cornstalks after mid-May of the season following corn. An accumulation of intact crop residue signals a lack of soil biological activity.”

4. At the latitude of Iowa and Nebraska, drilling cover crops usually happens after corn or soybean harvest. “That typically means cereal rye,” said Berns. “There’s no shame in cereal rye alone. It can be planted late and has an aggressive root system.” However, the 60-inch and 90-inch corn rows in the Cedar Valley Innovation experiment could reveal productive ways to interseed covers between corn rows. Another farmer and supporter of this experiment, Loran Steinlage, told me he has grown 300-bu. corn in 60-inch rows at his farm near West Union, Iowa. He commonly interseeds cover crops with both corn and soybeans.

5. Recker and Thompson plan to graze the plots with sheep after corn harvest. That’s a management tool Keith Berns encourages, as opposed to applying raw manure from feedlots. “Rumen bacteria are compatible with similar digestive organisms in the soil,” he said. Another soil-building tactic on low-fertility soils is to allow a “soil building season” — planting mixed cover crops in the spring, then grazing off the forage in summer and fall with intensive-grazing paddocks.

6. Berns alerted visitors to a promising new winter pea variety that Greencover is raising for a seed buildup. In tests, it controlled weeds, accumulated four tons of dry matter on the surface, and contributed 240 lbs. of nitrogen as shown by soil tests. 

Research organizer Bob Recker

Bob Recker also gained a small research grant for this project, plus technical support from the Natural Resources Conservation Service. But the unique aspect of this venture is that two senior Deere specialists had the experience, talent and capital to create and manage it for a long-term objective. For example, 16 sandy acres wouldn’t normally justify a couple new John Deere tractors, plus a new, specialized plot planter. But that first-class equipment was on hand. (I’ll be interested to see where the test-plot combine and/or weigh wagon comes from.)

Recker told field-day visitors that during his career, John Deere invested 5% of sales dollars into research and improvements. He encouraged farmers to do the same, saying, “Deere had to invest heavily in tractor exhaust emissions to meet EPA’s Tier 4 standards. Farmers may soon face much tighter regulations on nitrate runoff and other pollutants. If you invest now, you’ll be better prepared.”

The researchers planted BT corn this season. If they go non-GMO in future years, I’ll offer a caution: Our 20 to 40 acres of Renewable Farming test plots always used non-GMO corn for more than 10 years. Our farm’s reputation spread among herds of whitetails, which turned our cornfields into feedlots and confounded plot yield results. Imagine the deer-candy appeal of 16 acres of non-GMO corn mingled with tasty legumes, millet, winter peas, tillage radish and other goodies. Bob Recker noted: “We may have to fence out the deer. Good thing that Recker and Thompson are creative engineers!

NRCS specialist Neil Sass describes soil profile
in this research plot. Note that the top
foot or more is extremely sandy.
Keith Berns explaining cover-crop trials, with a tractor and cover crop plot planter on display.