Government incentives, spurred by climate change fears, will likely nudge you toward reduced tillage programs and cover crops in the near future. On-farm tests conducted by Farm Journal field agronomist Ken Ferrie, and his experience in hundreds of clients’ fields, show reduced tillage and covers require a vertical system, from which compacted soil layers and sudden density changes have been removed. Most soil layers and density changes are created by horizontal tillage, such as moldboard plows, disks, field cultivators and soil finishers.
For example, one of Ferrie’s plots shows how a subsurface layer can reduce yield. A compacted layer was created by running a field cultivator in wet conditions in the spring after chisel plowing the previous fall. (The last pass before vertical tillage must be vertical, Ferrie emphasizes, to avoid putting in a density layer.)
The graphs above show the yields from one horizontal and three vertical tillage treatments in two soil types. Fall chiseling followed by a vertical harrow in the spring produced the highest yield, followed by no-till; in-line ripping/vertical harrowing; and, finally, a soil finisher. Except for no-till, the vertical systems improved or removed the density layer, while the soil finisher left it in place.
“All the treatments were profitable,” Ferrie says. “But the greatest difference between vertical and horizontal tillage was 17 bu. per acre on silty clay loam and 37 bu. per acre in silt loam.
“This test confirmed results we have seen in other studies and on many clients’ farms. Removing compaction and density layers before transitioning to a vertical system can add 15 bu. to 20 bu. per acre and might lower cost of production,” he adds.
Before moving toward a vertical system (usually a three-year process), you first must determine whether layers are present. Ferrie’s preferred method is to dig up corn roots during the growing season.
“Paying attention to resistance as you dig, seeing how roots penetrate and examining soil moisture levels will show you whether layers exist,” he explains. “Knowing the depth and seriousness of layers will help you decide what tool or tools you need to transition to a vertical system.”
The Subsurface Layer Steals Bushels
Think 230 bu. per acre is a good corn yield? Wouldn’t you rather have 267 bu.? This side-by-side plot, in a field with a subsurface layer, compared three vertical systems (no-till, in-line ripping in the fall followed by vertical harrowing in the spring and fall chiseling followed by spring vertical harrowing) to horizontal tillage consisting of one pass with a soil finisher in the spring. The field contained two soil types, silty clay loam and light silt loam. Each vertical system outyielded the horizontal tillage.
“All these systems would have been profitable for the operator,” says Ken Ferrie, Farm Journal field agronomist. “But the vertical tillage programs yielded up to 37 more bushels per acre (in the silt loam soil) because they removed the layer put in by previous horizontal tillage. These results are similar to what we’ve seen on many clients’ farms.”
How to Find Density Layers
Do you have soil compaction and density changes that impede roots and water? Here’s how to find out:
- One sure clue. If your last tillage pass was horizontal (moldboard plow, disk, field cultivator or soil finisher), you have soil layers. “Even if a farm has been no-tilled for 10 years, if the last pass before vertical tillage was a soil finisher, we will find that layer,” says Farm Journal field agronomist Ken Ferrie. “Freezing and thawing does much to change density, but it doesn’t take out layers.”
- Tools you can use. The list includes GPS-equipped penetrometers, which store your results on the cloud, hand-held penetrometers, tile probes and, Ferrie’s favorite, a tile spade to dig up plants in the middle of the growing season.
- Dig deep enough to find old plow soles. You’ll probably feel density changes as you push the spade into the soil.
- Dig up one plant. If two or three come up at once, you’re under a layer and the plants are sitting on top.
- Read the roots. A corn plant’s roots should grow at a 30˚ angle from the crown, in a circular pattern. “If bulk density changes suddenly, roots don’t have time to taper, so they run sideways on top of the layer,” Ferrie says.
- The first three sets of crown roots are a key indicator. The first two sets, being the smallest, will turn on any layer. “If the third set runs horizontal, that’s a compaction layer,” Ferrie says. “If it just wiggles a little and then grows through it, it’s a density change.” Those three sets of roots are the most important for yield; sets four and five are for standability.
- Study the soil. If it separates on horizontal horizons, rather than crumbling, as you dig, those are soil layers. See if roots are turning and growing sideways.
- Sudden changes in soil moisture indicate horizontal layers. “As roots turn on layers, so does water movement,” Ferrie says. “If the top 4" is moist from a recent rain, and it’s dry below that, the rain came faster than it could penetrate a layer.” When subsurface layers prevent water from wicking to the surface, the surface soil can collapse into a massive, concrete-like state.
Want to learn more about how to convert to a vertical tillage system? Start here.
