Fertilizer, seed selection and residue removal are methods to handle heavy corn residue without tillage.
Corn residue accumulated after high-yielding crops should someday make a great source of cellulosic ethanol. “University research suggests that at a high yield level (200 bu./acre or more), growers can remove 40% of stover without negatively impacting soil organic matter,” reports Andy Heggenstaller, Pioneer Hi-Bred agronomy research manager. “As we move forward, cellulosic ethanol production may become a common form of residue management.”
But until those ethanol plants are built, the residue will continue to challenge farmers who need to plant a crop through it the next spring. Tillage is one method of handling residue, but there are other options. Universities and companies are studying some of the best ways to handle heavy residue, including removal.
Harvesting corn residue has improved yields in some circumstances, according to studies by the University of Minnesota. The studies were conducted on southern Minnesota’s heavy-textured, poorly drained soils. Normally, residue retains moisture, but in these soils, residue kept soil temperatures too cool. When the residue was removed, the soil warmed up and stimulated seed growth.
The university studies also found that nitrogen levels were lower in corn planted in the residue. Applying more nitrogen did alleviate this problem.
One concern was the long-term effect of removing the carbon-bearing residue. Aaron Sindelar, UMN research fellow, suggests that growers who remove residue for harvest should then apply manure, which will help offset carbon losses.
Select seed for high-residue situations. Pioneer Hi-Bred provides a suitability rating for hybrids in high-residue fields. Every year the company conducts trials of plant emergence in stressful situations, including early planting and reduced tillage. Hybrids are then assigned an emergence score that indicates how well the plant emerges under stress.
In addition, Pioneer hybrids receive a high-residue suitability rating that indicates how well the hybrid will perform in reduced-tillage systems. The company says it bases the rating on traits for stress emergence, northern corn leaf blight, anthracnose stalk rot, gray leaf spot and Diplodia ear rot.
Apply fertilizer in forms that account for soil environments created by a layer of residue. Preplant injection of anhydrous ammonia is one form. The anhydrous should be applied at 7 in. or deeper and angled so seed damage is prevented, according to Monsanto. The company’s literature suggests another preplant option is to apply liquid and dry forms of nitrogen on the surface.
Once planting starts, starter fertilizers will help jump-start seed growth in cool soils. Monsanto says starter fertilizer should be placed 2 in. to the side of the seed and 2 in. below the seed to prevent seed damage.
If soils are warmer, pop-up fertilizers are an option. These fertilizers should not be overapplied or salt injury may occur on the seed. Urea and diammonium phosphate (DAP) should not be applied with the seed.
Sidedressing nitrogen by knife or injector puts the fertilizer where the plant needs it and without potential loss of nitrogen. As a result, it will help hybrids reach full potential in high-residue fields.
If farmers tilled their soil last fall and have good seedbed conditions, they might try planting without further tillage, says Emerson Nafziger, University of Illinois Extension agronomist. He adds that this practice hasn’t been widely studied.
If farmers do want to try this planting method, Nafziger suggests that they use a burndown plus residual herbicide to control winter annual weeds.