Rolling soybean fields before or after planting ensures your combine won’t be picking up stones and rocks at harvest.
But that’s just part of the return when growers invest the time and resources required to roll their soybeans, says Syngenta Agronomic Service Representative Doug Fotheringham. “It’s important to realize that when we roll we improve our seed-to-soil contact, which improves our emergence and also the timing and uniformity of emergence.”
Fotheringham says he can’t emphasize enough how even emergence and uniformity plays in a higher-yielding soybean crop. He adds that the need for rolling is further amplified for growers who run air seeders. “Planters are very good at maintaining uniformity of depth as well as seed-to-soil contact, but air seeders present some challenges. The technology is getting better but planting depth tends to vary quite a bit more than a planter.”
Improving seed-to-soil contact
A key benefit of rolling is how it tightens up and compresses the top two to three inches of topsoil and improves seed-to-soil contact. That compression also helps even out planting depth and promote more even emergence.
“You can take a really average seeding job and turn it into a good one by rolling after planting because that roller can cover up a lot of mistakes that happen during the planting process, especially with an air seeder,” says Fotheringham. “It also pushes a little bit of dirt around to cover up and fill in furrows.”
When should you roll?
Many growers ask Fotheringham when they should roll their soybeans – before or after planting?
“Typically, we’ve always rolled soybeans after planting as time permits,” explains Fotheringham. That’s still the most common practice and it works fine, but rolling before planting is also an option. “It really depends on the type of seeder or planter you’re using and whether you’ve worked the field fairly heavily in the fall or the spring,” he notes. “In these scenarios, the top four to six inches of soil is quite fluffy and loose.”
Running planters into rolled soil is generally effective because there is very little soil disturbance. The same conditions can be achieved using air seeders with disc-style openers – very little soil is disturbed and the top three inches remains tight. Fotheringham adds that growers need to be cautious when using air seeders with sweep-type openers in rolled ground. These tend to move more dirt during seeding and loosen the soil. In this case, the seed-to-soil contact benefits of pre-plant rolling are lost.
Managing soil erosion
Growers also have to be aware of the soil erosion that can be linked to rolling, says Fotheringham. “The positives certainly outweigh the negatives, but when you roll you are basically pulverizing the top part of the soil and we have to be mindful of erosion. We can get some strong winds and there’s nothing to stop that soil from blowing, especially in a drier spring.”
For growers concerned about erosion, Fotheringham feels rolling before planting could be a better choice. “It's definitely not a fix, but when we roll first and plant after we do ridge the ground a little bit so it does help minimize erosion.”
Use caution when rolling in-crop
Rolling immediately after planting is an option, but don’t wait too long. “If you go back in that field and the seed has already germinated and started to push a bit of a shoot, rolling it could crack or break it off and the seed is no longer viable,” says Fotheringham. In this case, you’re better off to leave the field because the damage you can do will certainly outweigh the benefits of rolling. You don’t want to roll anytime through emergence to first trifoliate.”
Another caution is when growers experience wet weather immediately after planning. In this situation, you risk creating a crust or hardpan over top of the soybeans and emergence could be severely compromised. The impact can be dramatic if heavier soil is rolled after a rain event.
Fotheringham says growers can roll from first to third trifoliate, but they must exercise great care. “It really is critical to have hot weather – 25 to 30°C – if you want to roll at this stage. Under those conditions, the plant is still rigid, but it’s pliable and it will bend and pop back up. In cooler conditions, the stems can actually crack and can cause big trouble later in the season as the plant moves through the vegetative stage.”