No-till corn growers know that their crops benefit from the practice. Long-term no-till practices have been shown to improve biological and microbial activity in fields, breaking down crop residue and releasing nutrients back into the soil for future crops.
Research has also shown no-till residue reduces evaporation, saving 3 to 5 inches of water over the whole growing season. This is especially helpful later in the growing season when precipitation is reduced.
However, the same residue that can benefit a crop can also cause emergence stress in cold, wet springs if not properly managed. The issue can be further compounded in no-till continuous corn fields, where there can be a potential for diseases to harbor on last year’s crop residue.
Also, depending on how much crop debris is left on the field and its level of uniformity, it may be more difficult for the soil temperature to warm enough to provide that perfect environment for a corn seedling.
Therefore, the key to making continuous corn-on-corn rotations work in continuous no-till fields is forward-thinking and management, says Paul Jasa, Extension engineer with the University of Nebraska.
It Starts At Harvest
Ideally, residue management happens at harvest time, Jasa says.
“It’s best to harvest the crop taller, and leave some of the cornstalk standing at harvest,” Jasa says.
A 10- to 12-inch-tall cornstalk that’s upright in the field after harvest keeps other residue from blowing in the field, as well as catches snowfall and reduces wind erosion.
“If you cut or shred the stalk too short, you risk having wind blow that around in the field, and you’ll get bare patches with no residue as well as drifts of residue buildup that can be difficult to plant into,” Jasa says.
Managing residue is about creating uniformity. Using the cornhead on the combine to process the cornstalks and leaves that do get harvested can make the next spring’s planting go a lot easier. Knife-to-knife or tapered snapping rolls are more aggressive to lacerate and crush the stalks, Jasa says.
Breaking down the stalks exposes them to microbes and weather to speed up decomposition, he adds. With Bt corn hybrids, processing the stalks with the cornhead is even more important, Jasa says.
Other ways to manage no-till would be to use cover crops to add biodiversity to the corn residue. Cover crops, Jasa says, offer humidity with their canopy, which decomposes the residue from corn harvest, and the cover crops also feed the soil microbes that feed on the corn residue. To use them to their best advantage, though, Jasa says they must be controlled so they don’t dry out the soil or create additional residue.
However, if a producer is planting continuous no-till corn and hasn’t planned ahead for the spring planting at the time of fall harvest, there are still ways to improve the success of the next crop, Jasa says.
Offset planting has been suggested as one way to utilize today’s precision ag technology in a no-till situation.
“Offset planting only works if you had GPS when you planted last year’s crop,” Jasa says.
Producers can instead use a low-tech technique of lining the edge of the planting tractor’s tire against last year’s row and planting off of the old row. This means producers aren’t planting between rows, risking driving on residue and tire damage from tough stalks, he adds.
Planting 4 or 5 inches off to the side of the old row avoids old root stumps from the last crop, Jasa adds. This increases the uniformity of planting depth, too.
“Corn needs 2 inches of depth at planting,” Jasa says. “I prefer up to 3 inches deep if planting into dryland.”
A uniform depth at planting allows for a better root system to develop, improved water and nutrient uptake. Also, planting a little deeper gives the seed a uniform temperature during the day and night during the fluctuating spring months, Jasa says.
Jasa also advises farmers to be sure to have enough weight on their planters so that they can properly penetrate the soil to the right planting depth, especially if there is heavy residue in the field.
“Remember to set the planting depth slightly deeper as the depth gauge wheels will be riding on some residue,” he says.
Uniformity Is Key
If a farmer finds himself with a field of patchy residue at planting and would like to improve the uniformity of the residue for the benefit of his new crop, Jasa says there are a few mechanical solutions available.
“They could run a residue mover up front, followed by a spoked closing wheel behind the planter,” Jasa says.
No-tillers should avoid coulters, he advises. While they can cut residue, loosen the soil and reduce wear on seed-furrow openers in abrasive soils, they may also cause air pockets in the seed zone if they’re set too deep.
Spoked residue movers, though, can warm poorly drained soils as they part the residue, and can even out thicker layers of residue with more patchy spots in the field.
“Floating residue movers with depth bands help keep the surface more uniform, reducing soil movement,” Jasa says.
Only use spoked residue movers, however, in new no-till fields. If used in long-term no-till fields, residue movers can do more harm than good. Residue that’s moved at planting can later blow back over the row and create less uniform emergence.
With the price of corn, it’s difficult to advise farmers to consider rotating out of continuous corn in their continuous no-till fields, but that’s just what they should do, Jasa says.
“Push the pencil,” Jasa says. “This year, with high corn prices, it was different. But, generally corn on corn is not as profitable as a corn-soybean rotation. We’ve shown that you can improve profit by $100 per acre with a corn-soybean rotation over corn-on-corn.”
Switching to a rotation also improves yields. With a corn-soybean rotation, Jasa said there’s been shown a 5% to 20% yield increase in irrigated corn, and a 10% to 50% yield increase in dryland corn.
“Continuous no-till works best when you use crop rotation and diversity to break down the disease cycle,” Jasa says. “If you change crops, you’ll change the pests. If you choose to do continuous corn, it’s important to properly select your varieties, and look for traits of resistance different from the previous year’s crop.
“It’s best if you have a variety susceptible to one disease, that you plant the next year a variety not susceptible to the disease.”
For example, grey leaf spot likes to stay on old residue, he says. Jasa emphasizes the importance of scouting for disease and weed issues, especially in monocultures.
The benefits of continuous no-till are worth the extra effort in planning, Jasa says, even in continuous corn.
“The longer you are in continuous no-till, the improved biologic activity that’s present to break down crop residue,” Jasa says.
All it takes is a little forward-thinking.