There are three kinds of farmers. Those who have their corn planted and growing vigorously. Those whose corn is planted, but is in a sorry state because of being drowned out. And those who have not been able to plant. If you are in the latter two groups, this blog’s for you!

Farmers some where in the Cornbelt are lucky every year and their corn is planted on time and takes off. But farmers who have been unable to plant or need to replant are in a special group that is unusually large this year. Facing a June 5th crop insurance deadline to get corn planted, many farmers need some sunshine and warm winds to dry fields enough to make headway. And farmers who are challenged with the possible need to replant have some serious decisions to make.

We’ll provide a number of resources for you, but begin with the thoughts of Ohio State agronomist Peter Thomison in the latest C.O.R.N. newsletter. He says first and foremost, “Replant decisions in corn should be based on strong evidence that the returns to replanting will not only cover replant costs but also net enough to make it worth the effort.”

Assess the current damage much like you begin estimating yield in late July. Mark off 1/1000 of an acre, which is 17 feet, 5 inches in 30 inch rows, count the number of viable corn plants and multiply by 1000. If you are planting 20 inch rows, the distance is 26 feet, 2 inches. That gives the estimated population which can be compared with your intended population. The more times you gather that number randomly around the field the more accurate it will be.

Next comes your decision whether to replant, and University of Illinois Crop Production Specialist Emerson Nafziger has developed a decision aid which calculates your gain or loss from replanting, based on input costs, dates for replanting, and market value of the corn.

Another significant issue is row gaps, which Thomison says can reduce yield beyond an even distribution of kernels. He says gaps 4-6 feet can reduce yield by 5%, and gaps that are 11-3 feet will reduce the yield by 2%. Additionally, corn stressed with cool temperatures and excess water may only be in the 1-2 leaf stage despite being planted 4-5 weeks ago. Nafziger, in his recent newsletter at the University of Illinois, says, “This slow growth is not a good thing, but compared to a more favorable spring, such as the one we had a year ago, it means that replanted corn will not start out as far behind early-planted corn as it often would. So in relative terms, replanting is “favored” this year.”

The decision to replant requires a decision on pest control as well. Thomison says post-emergent herbicides are recommended in replant situations along with cultivation. For insect controls, the maximum labeled rate for a chemical at the initial planting will prevent your use of that same chemical for the replanting. And he reminds farmers that late planting dates are usually linked to corn borer damage, and that can be prevented with the use of Bt hybrids. And he adds, “In OSU studies conducted in 2004 and 2005, short season (104 day or less) Bt hybrids planted after the first week of June consistently out-yielded their non-Bt counterparts and usually produced yields comparable to commonly grown hybrid maturities (108 day or greater).”

As the cost of replanting rises, the potential profitability drops. And Thomison says, “If after considering all the factors there is still doubt as to whether or not a field should be replanted, you will perhaps be correct more often if the field is left as is.”

If you need some more hand holding as you make replant decisions, look to Purdue agronomist Bob Nielsen. Right hand. Left hand.

Summary:

Replanting decisions are tough decisions, but many farmers are having to make them because of poor emergence in cold wet soil conditions. Decisions need to be made by evaluating the viability of the crop that is trying to grow in the field, and in some cases it will produce a minimal crop. Some agronomists are also suggesting the slow start may warrant replanting in an effort to plant a crop that will get off to a good start. Herbicide decisions have to be made and that may force a post emerge herbicide, and insecticide decisions may require some corn borer protection. Plenty of research has been conducted on replanting, and help is available for the asking.

Stu Ellis

Leave a Comment

Name (required)

Email (will not be published) (required)

Website