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Interest in corn following corn is increasing. A move toward two successive years of corn in the rotation, of course, requires some new thinking about management practices and the changes that are needed compared to the more traditional corn-soybean rotation. When corn following corn is considered, some changes in fertilizer management are needed. Some important changes are described in the paragraphs that follow.

Nitrogen Rates

Most producers recognize that additional fertilizer nitrogen will be needed if corn is not preceded by a soybean crop. Currently, there is a 40 lb. per acre N credit for a previous crop of soybeans. This credit applies regardless of soybean yield. Some have the perception that the soybean N credit should be 1.0 lb. N per acre for each bu. per of soybeans produced by the preceding crop. That perception is not correct and is not supported by research conducted in the northern and western Corn Belt.

Therefore, an additional 40 lb. N per acre will be needed if corn follows corn in the rotation.

A switch to a corn following corn rotation does not imply that change in method or time of application of fertilizer N is needed. There have been questions about the application of 28-0-0 to stalks in an effort to speed the decomposition of the crop residue. This practice has proven to be beneficial in the laboratory and greenhouse settings. However, the application of N in this way has not been demonstrated to be an economical management practice for corn production.

Banded Fertilizer

Residue from the previous corn crop on or near the soil surface will reduce soil temperature near the seed. These cooler temperatures can decrease phosphorus uptake by young corn plants thereby reducing early growth. Use of fertilizer near the seed at planting is the management practice that can be used to help overcome this problem.

Many producers who planted corn after corn in 2004 discovered the importance of banded fertilizer near the seed at planting. When the banded fertilizer was not used, there were many instances of short, stunted corn with a light green color. Uniform emergence, enhanced early growth and more consistent stands were the consequences of the use of the banded fertilizer.

Use of banded fertilizer near the seed at planting should be a management consideration unless soil test levels for P are very high (more than 30 ppm for the Bray test; 25 ppm for the Olsen test). A high rate of fertilizer is not needed with this placement. For soils with a medium to high soil test for phosphorus, a rate of 5 to 8 gallons open acre of a material like 10-34-0 is adequate. For fine textured soils, this rate can be applied in direct contact with the seed with a minimum amount of risk. If soil test values for phosphorus are considered to be low or very low, a combination of broadcast and banded fertilizer should be seriously considered.

Rates in excess of 8 to 10 gallons per acre can be used without risk by adding attachments to the planter that allow for some soil to be placed between seed and fertilizer. The attachments vary. Some place the fertilizer below the seed. With others, the fertilizer is placed above the seed. There is no current evidence to suggest that one placement is superior to another. The key is to place the fertilizer close to the seed in a band.

Application of fertilizer in contact with the seed is not suggested for sandy soils. The risk of damage to emergence and germination is high. This high risk leads to the recommendation of having ½ inch of soil (at least) between seed and fertilizer.

Insecticides With Fluid Fertilizers

Use of a liquid insecticide at planting is a management practice that will probably be used by many growers. It seems logical to apply both fertilizer and liquid insecticides at the same time. There are several factors that affect his management decision. The two products must be compatible. If not, the insecticide may not be effective if the mixture is used. The insecticide should not have any effect on the availability of the fertilizer. Placement is another serious consideration. The most effective placement for either the insecticide or the fertilizer may not be the most effective for the other. The insecticide label is the best source of information regarding placement of each component.

Residue Removal

When corn follows corn, it is important to maximize early growth. For fields where fall chisel has been used a the primary tillage, a good management practice would be to plan for a residue free zone 10 to 14 inches in. in width over the seed. Planters can be fitted with a variety of attachments to remove the residue from the previous corn crop. This residue free zone in combination with banded fertilizer near the seed should stimulate early growth leading to optimum yields.