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Reaping long-term benefits of zero disturbance, cover crops

For Scott Gonnerman, these practices protect the soil, reduce the need for inputs and pave the way for added value.

Tyler Harris, Editor

May 1, 2020

6 Slides

For Scott Gonnerman, the term "no-till" doesn't quite cut it for describing his farming operation. For Gonnerman, the term "zero disturbance" is more fitting.

"I don't disturb any soil or residue," he says. "The only thing I have on my planter is my opener. I just cut a slot in the soil. I don't remove residue. There are many interpretations of no-till. That's why I like to say, 'zero disturbance.'"

Since 2008, Gonnerman, who farms near Waco, Neb., has abided by his zero disturbance ideology, only disturbing the soil with his planter's openers.

He started planting single-species cover crops that winter-killed in 2009, followed by multiple species mixes that included more winter-hardy cover crops in 2010.

"When I went to multispecies cover crops, I made sure I had at least two cool-season grasses, two cool-season broadleaves, two warm-season grasses and two warm-season broadleaves," Gonnerman says. "That way, I had something planned for the entire growing season. Some of the cool-seasons planted in summer didn't take off until fall when I grazed it, and they lasted until December to January. Some warm-seasons were dead after the first frost in October."

But it hasn't stopped there. Gonnerman continues to expand his rotation, and is currently in the process of adding more perennials such as alfalfa.

For Gonnerman, it's about net profit spread across the whole rotation — and sometimes, that means adjusting his expectations for yield, while also rethinking his nitrogen applications and irrigation.

"I think success is not determined by how much we make, but by how much we spend making it," he says. "In 2017, my cost to raise a bushel of corn was $2.26. That's still profitable today."

"One of the easiest ways I've cut costs is I'm not trying to outproduce my environment anymore," Gonnerman adds. "I used to shoot for 250- to 270-bushel corn, so I was farming for that. Now I farm for 200-bushel corn, and that alone probably reduced my inputs by 20%. A lot of those years, I was only raising 225 to 230 bushels anyway."

Adding covers, cutting costs

With a corn-soybean-small grain-field pea rotation, Gonnerman is able to grow two long-season cover crop mixes every four years. This includes a cereal rye or triticale cover crop after corn and before soybeans, a small grain such as winter wheat planted after soybean harvest, followed by a long-season, diverse cover crop mix planted after wheat harvest, followed by yellow field peas, and finally, a long-season, diverse legume mix after field peas.

Since he's incorporated more legumes, including hairy vetch, sunn hemp, Austrian winter peas and crimson clover into his cover crop mixes, he's been able to cut back on the nitrogen he's applying through commercial fertilizer — in some cases, cutting his rate by 50% of what was recommended by the Haney soil test — and still maintain yields.

Gonnerman also has started split-applying his nitrogen, applying some with the planter, sidedressing and applying the balance through the center pivot.

"At V5 and again at tassel, I take a tissue sample and send it to Ward Labs, and test it to see how much nitrogen I need," he says. "I must have been overfertilizing, because the last three times I planted corn, at tassel I planned on applying another 20 or 30 pounds, and tissue tests said I was adequate, so I didn't put any on through the pivot."

This is due in part to more active soil biology mineralizing nitrogen and making it readily available to plants. Over the past five years, Gonnerman has been able to raise between 2 and 2.5 bushels per acre of corn per pound of nitrogen applied.

"My goal is to get to 3 bushels per pound," he says. "I'm planning to start incorporating alfalfa for three years into the rotation. I think I can raise two years of corn after three years of alfalfa, with zero nitrogen, zero herbicides and still not use insecticide. I haven't used insecticide since 2013. I'm trying to break that weed cycle. I think I can control weeds with plants, but we're going to have to start putting in more perennial plants, like have alfalfa for three or four years."

Zero disturbance and cover crops also have improved infiltration, allowing Gonnerman to store more soil moisture from rainfall, and reduce the number of passes with his center pivots.

He notes that when he started zero disturbance in 2008, on average in an area of tilled soil, he could infiltrate a half-inch in one hour. When Gonnerman recently tested the infiltration in 2017 on a field that had been cover cropped since 2010, he notes 2 inches infiltrated in less than two minutes — and the first inch infiltrated in 23 seconds.

"We installed one pivot in the fall of 2012," he says. "In spring 2019, we only had 563 hours on the motor. It takes about 10 hours a year just to move this pivot to the farm. I think we've only run it four days a year since about 2013 to 2018. If I had spent 10 hours moving the pivot, that's about 100 hours a year, or about four days. In 2019, I put a half-inch on just to wash the fertilizer in."

With cover crop mixes, including brassicas such as turnips and radishes, which he says help control pests like wire worms and corn rootworm, he's also been able to eliminate insecticide applications.

Adding value to soil health

And Gonnerman hasn't planted treated seed since 2013. This has opened him up to non-GMO markets, and helped him save money on seed — which he usually buys from Nebraska-based Hybrid85. "The last couple years, my corn seed has cost $85 per bag," he says. "If it's over $100 a bag, I won't buy it."

Gonnerman typically plants shorter-season corn, either 97-day or 102-day corn, around the end of May. This gives him a chance to harvest earlier and seed cover crops earlier, and let the cover crop produce more biomass after the corn crop.

"I can plant 97- or 102-day corn the end of May, and it'll come out at 15.5% moisture at the end of September," Gonnerman says. "The nice thing about harvesting corn in September is that's when ethanol plants are looking for corn. Last year, our yellow corn went directly from the field to the ethanol plant. When we started out, they were 20 cents over Chicago futures. When we were done harvesting, they were down to 5 cents over."

Since 2013, all of the soybeans he's raised have been food-grade. In the past few years, all of his soybeans have been exported to Japan for the human consumption market. In years past, he's sold them to markets such as World Food Processors of Oskaloosa, Iowa, and Gavilon in Hastings, Neb., and he currently raises seed soybeans for eMerge Genetics, fetching a $2 premium.

Although Gonnerman has considered transitioning to organic with the addition of perennials and annual cover crops in the rotation, he's seeking a more regenerative-focused avenue for adding value to his crops.

"I think there will be more value added if I can sell something as a regenerative ag," he says. "Once we learn how to test our grain and feed, I think nutrient density on anything you harvest is going to outweigh organic certification down the road."

"Most people try it one to two years and don't see the return on investment right away," Gonnerman says. "I think in time to come, our land values and cash rental rates are going to be determined by soil health, especially if margins are tight. That will come along as our ability to test soil health comes along."

About the Author(s)

Tyler Harris

Editor, Wallaces Farmer

Tyler Harris is the editor for Wallaces Farmer. He started at Farm Progress as a field editor, covering Missouri, Kansas and Iowa. Before joining Farm Progress, Tyler got his feet wet covering agriculture and rural issues while attending the University of Iowa, taking any chance he could to get outside the city limits and get on to the farm. This included working for Kalona News, south of Iowa City in the town of Kalona, followed by an internship at Wallaces Farmer in Des Moines after graduation.

Coming from a farm family in southwest Iowa, Tyler is largely interested in how issues impact people at the producer level. True to the reason he started reporting, he loves getting out of town and meeting with producers on the farm, which also gives him a firsthand look at how agriculture and urban interact.

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