16 steps to better corn-on-corn and continuous corn
1. Know your foe
The 5% to 15% yield drag in corn-on-corn and continuous corn sometimes can be lessened. To do that, though, you have to overcome excessive in-row residue that keys five issues.
Poor seed placement. Residue stashed in the seed furrow at planting nixes seed-to-soil contact and results in uneven emergence.
Autotoxic compounds. “As residue decomposes, autotoxic compounds slow growth and reduce vigor of young corn plants,” says Jeff Coulter, University of Minnesota (U of M) Extension agronomist. “They can inhibit growth and vigor of young corn seedlings.”
Low soil temperatures. Excessive residue can lower soil temperatures below the optimal 50°F. recommended for planting. That delays emergence, early growth, and nutrient uptake.
That’s especially true in no-till corn-on-corn. “Soil temperatures can average 2°F. to 3°F. lower in the first three to four weeks after planting in no-till corn-on-corn when compared to disk-ripped corn-on-corn,” says Coulter.
- Nitrogen (N) availability inhibition. Ever notice the crunch of cornstalks on just-harvested corn ground? That’s the sound of carbon. Long term, the carbon that ends up as soil organic matter from residue decay boosts soil’s water-holding capacity and other benefits.
Short term, though, it can create a fertility issue.
“That residue is a sponge in which the soil microbes are using N to feed on as they break down carbon,” says Jason Webster, Central Illinois Practical Farm research director for Beck’s Hybrids. “They use N, and if you don’t apply enough N next season, the corn plant will say, ‘Hey, what about me?’ ”
- Increased disease. “This is especially true for diseases that survive on surface corn residue, especially anthracnose seedling blight,” says Coulter.
2. Don't show up late
Residue that causes late corn plant emergence will cause problems all season.
“Seeds need to imbibe 30% of their weight in water to germinate,” says the U of M’s Coulter. “Seeds surrounded by residue instead of soil will not imbibe water as quickly.”
The result is delayed and uneven emergence that creates plants unable to fully compete for water, nutrients, and light. Later on, these plants are late to silk. This boosts the risk of less pollen to make kernels, more stressful weather, and low soil-moisture levels during pollination.
In the chart below, you’ll see early-emerging plants yield more than late-emergers in uneven emerging fields. “However, it is not enough to fully overcome the yield penalty from late-emerging plants,” says Coulter.
3. Reduce in-row residue 4 ways
Distribute residue evenly behind the swath of the combine.
Shred stalks and till early in the fall if a full-width tillage system is used.
Have good planter row cleaners that work well. “Removing residue from the row is critical,” says the U of M’s Coulter.