Economically, producers will provide more input costs for planting continuous corn. These inputs include increased nitrogen, insecticide and/or seed cost for a Bt rootworm hybrid, irrigation where available, and potentially a fungicide treatment.
Another important consideration is equipment needs and labor. A corn/soybean rotation spreads out the planting and harvest season so one may be able to use smaller equipment and/or less labor. There are a lot more bushels to handle in a continuous corn rotation versus a corn/soybean rotation.
A long-term tillage study conducted at the South Central Agricultural Laboratory near Clay Center compared yields from corn/corn and corn/soybean rotations in disk, ridge and slot-planted systems. The data shows increased corn yields from 3.4 to 9.1 bushels per acre when followed by soybeans in all systems.
When it comes to pest considerations, rotation disrupts most pest cycles. Insects such as corn rootworms often do not survive corn/soybean rotations in Nebraska. Newer technologies such as Bt corn rootworm traits are one way that producers can manage corn rootworms in a continuous corn system. Soil insecticides also can be used. Pathogens causing diseases such as gray leaf spot, anthracnose and numerous stalk rots survive in corn debris.
Rotation to another crop can reduce the severity of these diseases the next time corn is planted. However, rotation will not completely destroy these pathogens. Tillage will bury the residue, destroying the pathogens. However, the benefits of conservation tillage, such as increased soil moisture and improved soil structure, may outweigh the benefits of tillage. Management strategies such as planting more resistant hybrids and the use of fungicides can replace or be used in addition to crop rotation and tillage.
Prices and production costs at the South Central Agricultural Laboratory from 1985 to 2004 showed a $60 per acre advantage to the corn/soybean rotation versus continuous corn. However, the current high price of corn coupled with high yields may offset additional input costs for continuous corn. Crop prices, yields, production costs, insects and diseases will all affect which crop rotation will be the most profitable in the future.
Jennifer Rees, Extension Educator; Bob Klein, Cropping Systems Specialist; and Tamra Jackson, Ph.D., UNL Plant Pathologist provided the information used in this week's column.
For more information or assistance, please contact Allan Vyhnalek, Extension Educator, University of Nebraska-Lincoln, Extension in Platte County. Phone: 402-563-4901 or e-mail AVYHNALEK2@unl.edu .
