Many factors can cause unexpected stand loss or unevenness. Deciding whether or not to replant to achieve a desired plant population is often a difficult decision farmers must make. Before making a replant decision that incurs additional costs, it is important to evaluate the existing stand, its health, population and distribution, and yield potential versus replant.
Evaluating Seed and Seedling Health
When corn is not germinating or emerging as it should, it is time to dig. If the seed is firm and looks healthy, it still has a good chance for germination and emergence. A water-soaked, mushy appearance indicates seed rot or decay. The same is true for the seedling. If the coleoptile (shoot), radicle (root) and seed tissue appear healthy, the seedling is in good condition. A water-soaked, mushy appearance indicates poor health and seedling decay. It is important to check the condition of the stand every few days to evaluate growth. If an emerged stand is uneven or damaged, the potential for recovery and growth should be evaluated. It will be necessary to locate the growing point to evaluate it.
Dig up a few plants, split them down the center and look for a triangular-shaped structure at the point of nodal root growth, about ¾ to 1 inch below the soil surface. The growing point will remain below the soil surface until 5 to 6 collared leaves (V5 to V6) have fully unfurled. A healthy growing point will have a light colored appearance with a firm texture. New leaves emerging every 3 to 5 days indicate normal growth. A damaged growing point will have a distinct yellow to brown, water-soaked appearance with a mushy texture.
Evaluating Stands: Plant Population and Distribution
It is important to determine the plant population and distribution (uniformity) of the existing stands. Count the number of viable plants in 1/1000th of an acre and multiply by 1,000 to obtain plant population per acre. Take enough counts in the field to represent the existing stand. Sometimes, plants that are weak or questionable in growth should not be counted. Are plants evenly spaced in the row(s) or are there skips or gaps? Observe the general plant population pattern over the field. Is it low overall or just in spots?
Existing Stand Potential versus Replanting
After plant population and health have been evaluated, yield potential of the current stand versus replanting can be determined. The following tables can be used to estimate stand potential. The yield values (expressed as a percent of maximum) are based on uniform distribution of plants within the row(s), which is not usually the case.
Equal to 1/1,000th Acre |
Row Width | Row Length |
20” | 26’ 2” |
30” | 17’ 5” |
36” | 14’ 6” |
38” | 13’ 9” |
Relative Yield Potential of Corn by Planting Date and Population |
| Planting Date |
| April 20 – May 5 | May 5 – 15 | May 15 – 25 | May 25 – June 5 | June 5 – 15 |
Population (Plants/Acre) | Percent Maximum Yield |
45,000 | 97% | 93% | 85% | 68% | 52% |
40,000 | 99% | 95% | 86% | 69% | 53% |
35,000 | 100% | 96% | 87% | 70% | 54% |
30,000 | 99% | 95% | 86^ | 69% | 53% |
25,000 | 95% | 91% | 83% | 67% | 51% |
20,000 | 89% | 85% | 77% | 63% | 48% |
15,000 | 81% | 78% | 71% | 57% | 44% |
10,000 | 71% | 68% | 62% | 50% | 38% |
Note: Values based on preliminary Iowa research and modeling; 100% yield potential is estimated to occur with 35,000 plant population and early planting. From: Iowa State University Extension, Corn Field Guide, CSI 001. 2009. In Press. |
If stand health is very questionable or regrowth can delay maturity, replanting may be the best option. Due to unique characteristics and adaptability, some hybrids can tolerate and compensate for lower stands better than others. However, if the existing stand is lower than the adapted population range of a hybrid and calendar date is not an issue, replanting may be best.
Decision Guidelines
- Each field has a unique set of conditions and should be evaluated individually.
- Evaluate the existing stand, its health, growth potential and yield versus replanting.
- Early replant decisions should be based on existing population and its potential, while later decisions are based more on calendar date and maturity.
- If replanting early, use adapted hybrids to maximize yield.
- After optimum planting dates, select earlier maturing hybrids.
To help transform your stand count info into a data-driven decision, Golden Harvest has developed a calculator to understand if existing stands will yield more or less than a delayed replant scenario. Go to
https://www.goldenharvestseeds.com/replant-calculator/ and enter your original and replant dates, along with current and anticipated replant stand counts, to quickly understand the yield benefit or loss from replanting.
Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.
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