Closing Wheels…Why start at the back?

Here at Exapta, we field lots of questions about closing wheels and whether they affect yields. It’s easy to start with the closing wheel when trying to improve the planter because it’s the first thing you see when you walk behind it. However, closing wheels are part of the the final step in seed placement. We encourage you to begin by evaluating the pieces at the front of the planter row-unit and their part in creating a proper seed bed.
What happens in step 1, 2 and 3 of the seed placement process will affect how well your closing wheels perform.

Before we address the 4 step system, we must not overlook the importance of planter levelness and planter downforce.

Making sure the planter is running level to slightly nose-up is an often overlooked function that greatly affects how the closing wheels engage the soil. A planter that runs nose-down will tip the closing bracket up to where more pressure than necessary is needed to get the furrow closed. A couple of degrees difference in toolbar angle can make all the difference in closing satisfaction. Refer to page 4 in our catalog for more information on running your planter slightly nose up.

Paying attention to row unit downforce in the field will tremendously impact yields once harvest rolls around. In no-till conditions, more downforce is needed. Increasing the pressure doesn’t always translate into pushing the opener deeper if there is not enough frame weight to leverage against. On the flip-side, too much downforce can be applied (especially in the wet conditions experienced throughout North America the past two years). Excessive downforce causes sidewall compaction which will make it harder to close the furrow and can cause the closing wheels to break up the sidewall in clods rather than crumbling the sidewall. This is where hydraulic downforce can pay big dividends, as it reacts quickly and can keep the pressure where it needs to be for maintaining depth.

The importance of the first 3 steps:

Step 1: Check opener blades. Once the blades lose 3/8-inch off their diameter, they’ve lost their bevel and no longer cut residues (or soil) readily. If you continue to run the blades for a long time, eventually they get worn so thin that they are sharp again (razor sharp), but this thinness causes huge problems with blade flex and furrows that are pinched slits—so narrow that corn kernel cannot get to the bottom. For replacement blades, Exapta now offers the Forges de Niaux openers blades for planters.

Step 2: Check seed tube guards. New guards measure 15/16-inch – if they’ve worn much off the original dimension, replace them. At 5/8-inch, the guards are completely shot – you never want the guards to get to this point. Having a guard that is full-width or nearly full-width is crucial for creating a furrow bottom that is consistently wide enough to install a corn kernel; blade flex causes erratic depth, and worn guards are a major contributor to blade flex.

For replacement guards, seriously consider Exapta’s Valion seed tube guards for 2-4 times the wear life of OEM, as well as being liquid compatible. Stay away from any inserts or guard replacements that protrude below the blades—these smear the bottom of the furrow terribly.

Will closing wheels throw seeds out of the furrow? Here again, what happens ahead of closing the furrow will help answer this question.

Step 3: Seed Firming. By running a Keeton seed firmer with the Mojo Wire, all seeds will be firmly pushed into the bottom of the furrow. Once the seed is locked in place, it is much harder to dislodge with the closing wheel action. Setting the down pressure on the closing bracket will also help the cause (as the goal is to completely shatter the sidewall), but the depth of the wheel needs to be checked in the field to make sure the spoke is still above seed depth. The added pressure from the Mojo Wire ensures that every seed is at the correct depth. Achieving the correct depth of every seed is more important to emergence than perfect seed spacing. “Seed firming is critical. The most important step.” – Matt Hagny (Seed Firming and Setting the Record Straight – coming in next Newsletter!) Check out Exapta’s Mojo Wire Kits, compatible with Keeton Seed Firmers.

Step 4: A spoked closing wheel is necessary for closing the furrow. As the opener blade exits the soil it will smear and pry soil outwards. The gauge wheel compresses this soil into a defined furrow wall that is compacted. This compaction is needed to keep the furrow wall from collapsing before the seed reaches the bottom. By continuing to use an OEM smooth closing wheel, you’ll eventually see more crusting, reduced oxygen exchange, slower germination, and more physical resistance encountered by the seedling as it pushes to the surface.

Spoked closing wheels are needed to break up the compaction so that crown roots can spread out in all directions. If you are seeing rooting problems or still have trouble closing the furrow when the previous steps are being done properly, a spiked wheel like the Thompson wheel will increase yield potential.

When it comes to improving the planter, it’s really about maximizing the “potential” of the seeds that are planted. The attachments available for planters are there to solve an agronomic problem: to increase emergence, which in turn, increases the potential yield. If you are debating which attachments will give the best ROI, we encourage you to start at the front and evaluate how each step of the process affects the others.