When a plant grows where it’s not wanted, producers call it a weed. When crop residue impedes planting and seedling emergence, producers call it trash. But unlike weeds that only serve to rob water and nutrients from the crop, residue can offer many benefits to growers—if they treat it like treasure. “All that residue has value,” says Jodi DeJong-Hughes, University of Minnesota Extension crop and soils educator. “Not only the nutrients in the residue,” but also its ability to protect and enhance the soil. “It lessens erosion, while improving water infiltration and soil biology. This helps increase the mineralization of nutrients to your crop. Residue will improve the soil’s resiliency.”
Managing that residue, however, requires producers to use a systematic approach that takes into consideration influencing factors from soil type and field slope to crop rotation and available equipment. Regardless of these variables, however, residue management always begins at harvest.
“Residue needs to be thought of at harvest time,” says Francisco Arriaga, assistant professor of applied soil physics at the University of Wisconsin-Madison and UW-Extension state specialist. “When you’re running the combine, you need to really start thinking about how to distribute the residue, so it doesn’t interfere and become a hindrance come springtime.”
Poorly distributed corn stover can both disrupt the efficacy of tillage tools in the fall and planters in the spring. It also can immobilize nitrogen trapped in concentrated residue, making it unavailable to the next year’s crop. Chopping corn heads offer options for breaking up stalks into smaller pieces, Arriaga says. It’s important, however, to make sure that as residue leaves the back of the combine, the straw and chaff are spread evenly across the entire pass and not piled in windrows.
“That’s especially important in a reduced tillage situation,” DeJong-Hughes adds. “If you’re trying to plant into high-residue and low-residue levels on the same pass, that can be difficult for the planter.”
A Time to Till
While there isn’t one type of tillage that will work for every field, the practice of turning over soil can be an integral part of a residue-management plan. When deciding which implement and tillage method are best, a producer must consider factors such as soil moisture and physical characteristics, slope and crop rotation.
In the South, for example, where coarse, sandy soils with lower organic matter are present, reduced tillage or even no-till systems are preferred to protect soil productivity. But in the Upper Midwest, where loam soils are rich in organic matter and often poorly drained, tillage can help dry out and accelerate spring warm-up of the soil for timely planting.
“So, look at your crop rotation and your soils, and then consider what challenges that residue might create,” Arriaga advises. “If you’re growing a lot of corn-on-corn, you probably will benefit from some kind of tillage. If you’re rotating crops, say corn and soybeans, consider rotational tillage, some type of reduced tillage or even no-till.”
On heavy soils in high-residue situations, such as continuous corn, more aggressive tillage, such as moldboard-plowing or disk-ripping, may still be an option today.
However, the costs of such methods and the potential for erosion should be considered. “I would say deeper is not necessarily better, and producers may not need as much tillage as we’ve traditionally been doing,” DeJong-Hughes says. “Instead of moldboard-plowing deep, which leaves less than 15% residue cover and costs more to operate, chisel-plowing may meet your management needs, while leaving 30% cover.”
A popular alternative is strip-tilling, which combines the benefits of chisel-plowing with no-till. Strip-till implements will prepare 7-to-10-inch-wide bands of soil for planting, while leaving the residue and soil between the rows untouched.
“A lot of farmers here in Minnesota, if they’re in a corn-soybean rotation, won’t run anything but the strip tiller,” DeJong-Hughes says. “Those in a corn-on-corn rotation might run vertical tillage to cut up the residue into smaller pieces ahead of the strip tiller.”
Arriaga adds that in cases of soil compaction below 6 inches, using a ripper is the only way to address the issue. “You need to bring the steel. It’s the only way to fix it,” he says. “But then, you need to figure out what caused the subsoil compaction in the first place and keep it from happening again.”
The final piece completing the residue-management puzzle occurs at planting. Arriaga says that growers need to examine the setup of their planters and account for not only the crop being planted, but also the conditions into which it’s being planted.
“Check your row cleaners, your ‘trash whippers.’ Are they working correctly? What about your closing wheels?” he asks. “You left that residue to benefit the new crop, so make sure your planter setup allows that to happen.”
Properly operating row cleaners can help ensure hair-pinned residue doesn’t cause the seed to miss the optimum moisture level and emerge late, says Bryce Baker, integrated marketing manager for Precision Planting.® In addition, row cleaners keep the seed furrow clear of residue that could cause seedling blight by giving off toxins while the crop material breaks down.
Arriaga says producers shouldn’t forget to account for the nutrient value of crop residue when applying fertilizer prior to or during planting. “There’s an economic value associated with your residue that can be captured,” he adds, noting that by contrast, growers who remove residue, such as corn stover for biomass, may need to replace those nutrients.
DeJong-Hughes says corn requires greater seedbed preparation than soybeans, so tillage needs for each crop vary. Whereas corn may benefit from post-harvest tillage, soybeans may only require light tilling in the spring. “It’s a whole different farming system now, and there are so many more variables than just tillage,” she says. “But if you’re doing the same thing that you’ve always done—tilling like our dads and grandpas did—maybe it’s time for a change.”