According to Iowa farmer and precision ag specialist Jeremy Swanson, the purpose of tillage is to ensure the best seedbed conditions possible for planting. In this series, we’ve covered tillage implements, strategies for residue management, and the biological products on the market today formulated to aid in the digestion of tough residue. Now, we’re going to take a look at your spring tillage pass and how to best optimize your seedbed to promote emergence. 

Your #1 Goal: Promote Seed to Soil Contact

How do you give your seed the best chance to start? Spring tillage is all about seedbed; getting the top of the soil opened up to get that good seed to soil contact. In my opinion, that’s 100 percent of it. This maybe isn’t as vital with soybeans, but with corn, we’ve learned that seed-to-soil contact is very, very important. 

Set Tillage Depth Based on Planting Depth

The depth at which you need to plant will determine your depth settings for tillage. For soybeans, we’re probably going to plant in that one- to two-inch-deep range. You're going to want your tillage pass to be maybe two, two and a quarter or two and a half inches deep. 

From the FCLG: Soybeans, as with any crop, need access to moisture in order to germinate. This means that if you’re planting earlier in wet conditions, you might want to plant at a shallower depth. You may want to consider planting deeper when your crop is going in later or in dry soil conditions. Soil type will also influence your planting depth. Light, well-drained soils often require a deeper planting depth; you may have better success planting shallower in heavier soils. And you need to watch your speed while planting, of course. Uniformity is critical to overall stand, so you don’t want to exceed the speed at which you can maintain accurate depth control. 

For corn, I like to aim for two, two and a quarter, or two and a half inches deep. I even like to go down to two and three quarters. With these depths, or whatever depth you’re planting at, your field cultivator needs to be under that. You need to be three, probably four inches deep. 

It's Important to Level the Planting Field

The other piece to spring tillage is to get the soil as level as you can so you don’t get a bunch of bounce with your planter, which in the end messes up your planting depth. So leveling is a huge issue with spring tillage because, again, you’re working to ensure both good seed-to-soil contact and the correct planting depth.

Obviously, the field cultivator is the main tillage implement used in spring. Some guys run vertical till machines in the spring as well, as they do a nice job of leveling the ground. And, I have seen guys mount coulters, similar to the style you’d see on a vertical till machine, ahead of the row units on their planters to do a bit of light tillage during the planting pass and save wear and tear on their row openers. 

Even if you’ve had a really wet fall, and you have some larger clods of soil in your fields, you should stick with your tillage plans. Usually, freeze-thaw cycles over the winter will break those clumps up to the point where, once the field cultivator hits them, they just go poof, and the leveling system will finish the job. The vertical tillage machine is a good option for taking care of them too, as it will slice through them. In fact, it might be a better option because the machine is going underneath a bit more and will lift and throw the soil to some extent. 

Wait for Fields to Dry

Moisture issues can develop as a result of your spring tillage pass, and this would apply with either a field cultivator or vertical till machine. As you run your implement deeper you’re going to start to pull up moisture from further down in the soil profile. And then you can start bringing up mud balls that don’t break up, which leads to a cloddy surface. This is why a lot of guys tend to shallow up for the spring pass—they want to stay out of the moisture and the mud. 

My thoughts are this: give fields an extra day or two to dry out. Remember to set your depth based on your seeding or planting depth. We often see issues with a rough or cloddy surface because we’re out there sooner than we should be. Like I said, let the field sit and dry out another day or two to help ensure that you’re preparing the best seedbed to get your crop off to a solid start. 

Stay 24 Hours Ahead of Your Planter

As far as timing goes, I think one to three days ahead of the planter is good. And never less than 24 hours. Unless conditions are really dry, you’re going to bring up a little bit of moisture with your spring pass either way. And you want a little bit of time for that to dry off before you plant. Nate Firle at AgRevival is running a three-year study on this very issue, and I’m really excited to see what the data is going to show. For the first year, I think his research showed that you have to be at least at the 24-hour mark. Anything less and you’re losing yield. 

From FCLG: AgRevival’s Planting Time After Spring Tillage study wrapped up its second year in 2023. Across two years of the study, researchers found an average 3.8-bushel-per-acre advantage when waiting one day after tillage to plant. According to Nate Firle, “ensuring adequate seed to soil contact and preventing sidewall compaction (due to fluffy or wet soil conditions) is critical during early growth of corn.” You can read more about this study and many others here: 2023 AgRevival Research Book

Nate’s data makes a lot of sense to me. You’ve got to let the field dry off a bit. For one, the soil will be a little warmer. And if you wait, you may not have to deal with mud sticking to your planter’s gauge wheels. We all know that the gauge wheels control your planting depth. If the mud raises up your gauge wheels and they’re hovering and bouncing, your planting depth is going to be off. So let that ground dry off a bit for 24 hours and your planter will be more likely to run across your ground nice and smooth. 

Where it gets really tricky is if you go out, work a field, and then you get a pounding rain on it. Now, a lot of this depends on the particular farm, where it’s at, the soil types, and so on, but rain can pack down a field and almost seal it off to the point where it doesn’t dry out underneath. There may be a scenario where you will need to go out and work that ground again to try and fluff it back up. 

Scouting for Tillage Success in Summer

From FCLG: We posed this question to wrap up our tillage interview with Jeremy: Can you find evidence of good (or bad) tillage practices during a summer field scout? 

One of the first things you can notice is your planting depth. Let’s say you were aiming to plant at two and a half inches for corn. You go out and start digging and find that you only planted at an inch and three quarters. What happened? Well, we fluffed up the soil during tillage and planting and then the field got hit with a rain after planting and settled everything down. During planting, you probably need to be shooting for two and three quarters or maybe even three inches, so that your end result is two and a half.

When you start digging out plants, sometimes you bring up an entire root ball and you start to look at the plant structure. And sometimes you can see where the field cultivator shank ran. Maybe the root started down but then took a sharp bend only to one side. Well, you know that the plant hit a tillage pan and the roots found the easy path through where the cultivator or ripper shank ran. Was it too wet when you were running? More times than not, with tillage pan issues, that’s what it was. 

Plowing Through Tillage Advice

Tillage is responsible for residue sizing and breakdown, soil compaction mitigation, and seedbed preparation. Your tillage passes are vital to your farm’s productivity, as your seed needs a fast start if you’re going to achieve top yields. And one key to a uniform and fast-emerging stand is optimum seed-to-soil contact—avoiding soil clods and air pockets as much as possible. With properly sized residue and well aggregated soil, your planter stands a better chance of delivering your seeds to the proper depth and uniformly closing the seed trench.