Corn-on-corn acres, which are driven by ethanol production, are on the rise. Continuous corn has more problems than corn after other crops because most of the diseases and insects of corn carry over on the residue. The previous year legume crops add not only pounds of nitrogen, but the nitrogen is released by the soil organism midway through the growing season. This release gives high-yielding corn hybrids a shot of late-season nitrogen, which increases yield and prevents them from having to cannibalize stalks and lower leaves to fill the ear.
Diseases and insects that match a specific hybrid’s susceptibility can develop in first-year corn. These diseases and insects carry over on the residue into the second year. Rotating to the same hybrid, or even one with similar genetic families, increases leaf diseases and stalk rots. Every insect or disease from the year before is out in that field, waiting to attack that hybrid from day one. When planting corn-on-corn, always rotate to a different hybrid, preferably a different genetic family type.
Hybrids containing Eastern and Early Health Genetic Families tend to have more plant health. In addition, select hybrids with as much rind strength as possible, which enables stalk integrity after the plant has died. Northern, Eastern and High Yield Genetic Families tend to have the best rind strength. Eastern and Northern genetic types work well where heavier soil types supporting high populations are encountered. On lighter soil types, using Northern and Eastern males on High Yield females allows for the use of lower plant populations that provide the required stalk quality. Another alternative on light soil types is to use a flex-eared Southern male on a High Yield female with a lower plant population to improve stalk quality.
Corn rootworm beetles prefer to feed on silks. The latest flowering hybrids tend to attract beetles from adjacent fields. These beetles lay their eggs in those late-flowering fields. If a field is going to be corn-on-corn in two years, plant early hybrids on that field now. Save full-season hybrids for corn-soybean rotations while planting early-maturing hybrids on continuous corn.
Because no late-season nitrogen is released from a previous legume crop, corn-on-corn acres are more likely to run out of nitrogen. Earlier flowering hybrids will absorb most of their nitrogen sooner than a late-flowering hybrid, leaving less time for leaching or denitrification losses of the fertilizer nitrogen. Plus, earlier-maturing hybrids can be harvested first, lowering the likelihood of stalk lodging. With less nitrogen leading to more cannibalization, and with more residues to introduce disease, an earlier harvest enables a reduction in harvest losses.
Since the corn plant absorbs 75 percent of its nitrogen by tasseling, the earlier the hybrid tassels, the higher the availability of fertilizer nitrogen. Earlier hybrids therefore make more efficient use of the fertilizer nitrogen in corn-on-corn before the nitrogen has the opportunity to leach away or be denitrified. This reduces stalk lodging and increases yields in corn-on-corn production systems. In addition, manure applications should be prioritized for corn-on-corn fields as the nitrogen from the manure is released later in the growing season.
If you are in an area with corn rootworm problems, consider corn rootworm hybrids. Because the active ingredient in CRW corn is at the point where the insect feeds, the efficacy is better than insecticides, and performance is not influenced by soil moisture levels.
Reducing plant populations on continuous corn takes stress off the corn plant because less nitrogen and water are required and lower density keeps plants shorter. On lighter soil types, where water-holding capacity cannot support the high densities required to get Northern and Eastern types to yield, use High Yield x Southern Genetic Family hybrids and reduce the plant populations to lower, safer densities.
In northern areas where Southerns tend to be too late, use Northerns with the large-eared High Yield Genetic Family females. When using CRW corn, this lower density can save considerable expense on your corn rootworm control. At $2.50 per thousand kernels, the savings can be significant. Be sure to use Cruiser®-treated seed for wireworms, seed corn maggot and other secondary insects.
Use herbicide-tolerant corn systems in the second year of corn-on-corn to control volunteer corn from the previous corn crop. LibertyLink® and Roundup Ready® can be used in successive years if herbicide-tolerant systems are preferred for all corn production. Using LibertyLink® hybrids in the second year allows Liberty® to kill the Roundup Ready® volunteer corn from the previous year and allows for the use of Roundup Ready® soybeans the next year to control volunteer LibertyLink® corn. The use of Roundup Ready® stacked with Herculex® or Bt11 hybrids will result in volunteer corn that is both Roundup Ready® and LibertyLink®. This would not be recommended for corn-on-corn acres.
Visit the Answer Plot® location in your area to see how CROPLAN GENETICS® corn hybrids perform in conditions similar to yours. You’ll see how the influence of various genetic families affects hybrid performance. Agronomic experts will be available to help you match the right hybrids to your fields for maximum performance. For more information on Answer Plot® locations, see your local retailer or answerplot.com.