Corn Replant Decisions
R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen
rappy stands of corn (aka less than desirable) occur somewhere in Indiana every year. Unacceptable stand establishment in some of these fields may eventually require growers to make decisions about replanting. Deciding to replant a crappy stand of corn should be based on a number of criteria, but unfortunately the most common is often the grower's emotion associated with looking out the kitchen window at the damaged field every morning or driving by the field every afternoon taking the kids to baseball practice.
Making a wise decision about the merits of replanting a damaged field of corn requires more than emotions. In fact, I would rather that emotions be taken out of the equation entirely. Toward that end, I developed a replant decision-making worksheet that assists growers and farm managers in making that important replant decision. The worksheet allows you to determine the damaged field's current yield potential (if left untouched), its replant yield potential, and the dollar returns (if any) from replanting the field.
The worksheet is included in a larger overall publication on corn replanting titled "Estimating Yield and Dollar Returns From Corn Replanting". This Purdue Extension publication (AY-264-W) is available as a PDF-formatted download from the Web at http://www.agry.purdue.edu/ext/pubs/AY-264-W.pdf.
Some of the information that is required to complete the worksheet originates from cropping records and history, including the original seeding rate and planting date for the damaged field. Some of the required worksheet inputs are frankly estimates, including what the field would have yielded under "normal" conditions if it had not been damaged and what market price you expect to receive for the grain after harvest. The expected replanting date and replanting costs are also required for the worksheet calculations.
- Recognize that the expected replanting date may be uncertain if the field is too wet to replant today and the forecast is for a lot of rainy weather. An accurate estimate of the replanting date is important because it influences the estimate of yield relative to "normal" and, thus, the estimate of dollar returns from replanting.
- Recognize that there is no guarantee of success for later-planted replanting situations. Late-planted fields will pollinate during late summer when high temperatures and moisture deficits are more common. Late-planted fields are often more attractive to late flights of European corn borer, so make sure you consider hybrids with Bt corn borer trait technology. Late-planted fields can also be more susceptible to fall frost damage if the corn does not reach physiological maturity prior to the occurrence of damaging temperatures, so choose replant hybrid maturities wisely (Nielsen & Thomison, 2002).
- Recognize that the costs of replanting a damaged stand may include additional herbicide or tillage to eliminate the surviving plants in the crappy stand. Simply replanting through an existing, crappy stand of corn is not always a wise decision because the original plants of the crappy stand can significantly compete with the newly emerged replant seedlings and reduce their yield potential. My opinion, supported by empirical evidence, is that unless the surviving population of the original crappy stand is significantly less than 50% of the intended original population, you ought to take steps to eliminate those plants prior to replanting the field. Unfortunately, "taking out" the original plants is not as simple as it was years ago because of today's transgenic herbicide-tolerant traits. If the original hybrid planted in the field contains Roundup-ready™ or LibertyLink™ traits, you will not be able to use glyphosate or glufosinate herbicides to "burn down" the original, poor stand of corn. In addition to cold, hard steel (aka tillage), there are a limited number of herbicide options for killing crappy stands of these herbicide-tolerant hybrids (Johnson et al., 2010), but some require a significant waiting period before replanting the field. Corn older than about V3 (three leaf collars) will also generally be much more difficult to "take out" with these alternative herbicides.
Finally, some information is required for the worksheet calculations from the damaged field itself. You will need an estimate of the surviving plant population that is representative of the damaged areas of the field. Depending on the nature of the crappy stand, you may also need estimates of after-damage stand uniformity and plant defoliation.
I will be the first to admit that it takes some time and patience to complete the replant worksheet; both of which are usually in short supply at the time the decision is being made. Recognize, though, that much of the replanting that occurs every year throughout the state is based primarily on emotion and not on estimates of economic returns. Taking the time to work through the steps of my replanting worksheet will help clarify the economic returns (or losses) to replanting and reduce the influence of emotions in this important crop management decision.
Johnson, Bill, Tom Jordan, & Glen Nice. 2010. Methods to Control Volunteer Roundup Ready or Glyphosate-Tolerant Corn in a Corn Replant Situation. Botany & Plant Path. Dept, Purdue Univ. Online at http://www.btny.purdue.edu/WeedScience/2010/VolCorn2010.pdf [URL accessed 2012].
Nielsen, RL (Bob). 2003. Estimating Yield and Dollar Returns From Corn Replanting. Purdue Univ. Cooperative Extension Service publication AY-264-W. Online at http://www.agry.purdue.edu/ext/pubs/AY-264-W.pdf. [URL verified 5/15/06].
Nielsen, R.L. (Bob). 2012. A Recipe for Crappy Stands of Corn. Corny News Network, Purdue Univ. Online at http://www.kingcorn.org/news/timeless/CrappyStands.html [URL accessed May 2012].
Nielsen, Bob and Peter Thomison. 2003. Delayed Planting & Hybrid Maturity Decisions. Purdue Univ. Cooperative Extension Service publication AY-312-W. Online at http://www.agry.purdue.edu/ext/pubs/AY-312-W.pdf. [URL verified 5/15/06].