Before Replanting Corn, Consider Direct and Indirect Costs
May 13, 2011
Conditions over the past month have been cooler and drier than normal. While planting was delayed in much of the state, those fields planted in early April are growing and developing slowly. In some of these fields the starnds are spotty and thin and growers are considering replanting.
Figure 1. Corn row where gaps in the stand were common. With a light rain, delayed plants broke through the soil surface and will likely recover. (Photos by Mark Hinze)
Crop Scene Investigation
Before deciding to replant, thoroughly investigate the field in question.
Figure 2. Corn leafed out underground, coleoptile split and kinked.
In south central Nebraska, one field recently examined showed a population range of 24,000 to 32,000 plants per acre with an average of about 29,000.
Upon further investigation in the low-lying areas of the field, approximately 4,000 plants per acre were leafing out underground (see Figure 1). These plants will not likely survive and should not be included in stand counts.
Other seedlings may be just about to break the soil surface and appear to be developing normally, even if slower than usual. Include these plants in the stand counts when deciding whether to replant.
Figure 3. Corn seedling that leafed out underground next to a plant at the V0 to early V1 stage.
In an April 26 CropWatch article, we suggested a few things to consider before rushing out to replant.
Replanting corn often comes down to a financial decision. When weighing costs and potential benefits, a few things often may be misrepresented or unaccounted for in the equation. Consider these factors.
Yield potential of the existing and replanted crops. Early planted corn is going to have greater yield potential than late planted corn. Corn plants that started a month ago have a month's head start (albeit a slow one due to cool weather).
Management of the previous corn stand. Another CropWatch article discusses options for controlling an existing stand. When considering this option, consider the additional costs associated with making an otherwise unnecessary pesticide application.
Seed costs. For some of you, this may not be a concern, but for others this will definitely play a role in how you proceed. While many seed companies insure their seeds, there may limitations on how much seed you can be compensated for and under what conditions. Check with your seed dealer if you are unsure. (Very early planted seed is not always covered.)
Time. Because you are going to have to manage the existing stand and replant, you are committing to a significant investment in time. Will other time-sensitive work need to be delayed? Remember, your time is valuable.
Long-term impacts from making two more trips across the field. While compaction issues can be mitigated by using controlled traffic and some soils are more prone to compaction than others, making additional trips across the field will cause compaction. This compaction will lead to long-term, but often unseen, yield loss and therefore, a loss in your pocket.
- Potential loss of nutrients. Depending on how far along the existing corn stand is at the time of management, nutrients may be lost. The corn may have already taken up a significant amount of nutrients, especially nitrogen.
Probably all too often, a thin corn stand is replanted because both the direct and indirect costs weren't fully considered. When all the costs are considered, replanting may not be justified.
Research: Even Emergence Less of a Factor
While it is certainly true that uniform plant spacing and even emergence/plant development have the highest yield potential, recent research suggests this may not be as much of a concern as originally thought.
In a recent research article (Agronomic Responses of Corn to Stand Reduction at Vegetative Growth Stages, 2011) by Jeff Coulter et al. in the Agronomy Journal, results from Illinois, Iowa, and Ohio showed that with a 17% stand loss at the V5, V8, and V11 growth stages, there was only a 4% yield loss. Additionally, they showed that neither uniform nor random patterns in stand loss affecting inter-row spacing of plants affected corn yields. Their work suggests that corn may have a greater ability to compensate for lost plants than previously assumed.
Given that recent showers have graced many parts of the state, it is likely that corn seedlings will start to develop more quickly now. Seeing a thin or spotty stand can be frustrating. If you are unsure of whether to replant a field, consult a local agronomist or agricultural professional for an unbiased assessment of the situation.
Greg Kruger, Extension Cropping Systems Specialist
West Central REC, North Platte
Extension Educator – Weeds, Lincoln
Extension Educator, Hall County