Here’s a simple way to begin testing whether vertical tillage is working: After your primary tillage pass, hop in the truck with an open soda can and see whether it spills as you drive over the land.
If the soda stays in the can, chances are your tillage tool is doing a good job of moving the soil vertically to permit good root growth, says Bill Bauer, B&M Crop Consulting, from the 2014 Corn College in Coldwater, Mich. If the soda spills because of periodic bumps, there are likely columns of soil in the field that will prohibit proper root formation.
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Those dense layers of soil are a problem that can result from horizontal tillage action from tools such as field cultivators and disks, explains Missy Bauer, Farm Journal associate field agronomist. In addition to true horizontal tillage tools, there are also true vertical tillage tools and hybrid tillage tools that create a mix of both actions. Each of these categories can be effective, assuming farmers take the time to understand how each works and determine which makes the most sense for their operation.
"What we really want to do is create an optimum environment for roots," Missy says.
Two important practices can help you determine whether soil density—defined as the amount of air space between soil particles—is working to support ear growth or limit it:
Examine root balls. Dig up the root ball on the outside of the gauge wheel pass, being careful to see where the soil naturally breaks to reveal varying densities. Then give it a haircut by trimming off brace roots to review crown roots more closely.
"Roots should normally go down at a 35-degree to 40-degree angle," Missy notes. If the first three sets of crown roots appear to bend or change direction, it’s an indication soil density changes too much as the roots grow deeper. The fourth set of crown roots emerge with the V4 stage, where yield potential begins to emerge. That’s why farmers should look for problems with root growth and water movement early on to troubleshoot.
Dig a soil pit. Among the benefits of a soil pit is the ability to view a cross-section of the root zone beneath your corn plants. Once the pit has been dug, feel for changes in density with a soil knife. Start at the top of the pit and work your way deeper into the ground.
Next, observe the depth of roots. Roots should extend vertically through the soil profile and pull water from the subsurface toward the plant through capillary action.
On the other hand, if the soil has been layered by horizontal tillage, water saturation will occur more quickly close to the surface, and water in the subsurface will be trapped by hardpan.
That’s true even on no-till fields that were last cultivated decades ago. For example, Missy says, one farmer dug a soil pit in land that hadn’t been tilled with a field cultivator for 25 years. Just 4" beneath the soil surface, roots were turning sideways because of a change in density.
The story illustrates the importance of establishing good soil density down into the profile before a tillage machine is brought on top of it.
"Vertical tillage is really a whole system, and it starts with what kind of soil density you have underneath," Missy concludes.
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