Early Stand Evaluation + Emergence Problems in Corn
Why Take Stand Counts?
It’s vital to take stand counts in newly emerged corn for several reasons. Stand counts provide a window into how well the planter spaced seeds down the row, and how close the planter got to target seed drop. Stand counts also give a first look at how plants are performing when it comes to emergence. Knowing how many plants emerged helps growers measure progress towards hitting yield potential, and provides information needed to make smart, timely management decisions for the rest of the growing season.
When and How to Take Stand Counts
Stand counts are best taken soon after emergence, to identify and address emergence problems early on. To take stand counts:
1) Walk at least twenty paces into the field before starting a stand count. At the edges of the field, tire traffic and slowed planter speed at turns may alter emergence or seed drop in comparison to the majority of the field.
2) Choose a random location, and avoid spots where stand is clearly thicker or thinner compared to average in the field.
3) Refer to this table to determine the distance in 1/1000th of an acre, based on row width. Count the number of plants in this distance, and then multiply that number by 1000 to estimate the emerged plants in an acre.
4) Take additional counts with multiple rows to get a more complete picture of emergence in the field.
5) Keep reading for help identifying common emergence problems.
What a Healthy Seedling Looks Like
One of the first steps in identifying emergence problems is understanding what a healthy corn plant looks like at the same stage in development. Many issues in emergence occur below the soil line – not just in the leaf, so be sure to “do some digging” to analyze all parts of a newly emerged plant.
Leaf shape, size and color appear normal
Spike is straight, firm, and has a white to light yellow color
Mesocotyl is white and firm to the touch
Seed is firm, shape and color appear normal
Seedling roots show normal side branching and overall length
Identifying the Cause of Common Emergence Problems
When blank spots or skips are present, or emerged seedlings appear unhealthy above or below the soil line, there are many clues to help determine the cause of these issues:
Fertilizer Burn – Seed has a caramel-brown to black color. Roots are shortened or nearly completely missing, and root tips are blackened and brittle.
Seedling Disease/Damping Off – Seed is brown, wet and squishy, mesocotyl and roots are watery, have a brownish color, and are soft (Pythum, Fusarium)
Seedling Disease - Mesocotyl and/or spike has a dry, light brown to reddish discoloration or dry rot (Rhyzoctonia)
Planted too Shallow - Mesocotyl region is missing or very short (less than ½ inch in length)
Planted too Deep - Mesocotyl region exceeds 1½ inches in length, sprout is bent and/or has unfurled (leaves have opened) before it reached the soil surface
Insect Damage - Seed has holes in it or is partly missing, mesocotyl and/or growing point has areas where tissue is missing, roots are scarred or hollowed (insect damaged tissues will develop a reddish brown discoloration and may initially resemble a dry rot appearance)
Cloddy Soil Surface, Crusted Soil Surface - Sprout is bent, curled, and/or has unfurled (leaves have opened) before it reached the soil surface
Failure to Fully Close the Seed Slot - Sprout is bent, curled, and/or has unfurled (leaves have opened) before it reached the soil surface, seedling roots are abnormally long (greater than 2½ to 3 inches)
Chilling Injury During or Immediately Following Germination - Swollen kernels that failed to germinate, stunted seedling roots and/or sprout, curling or "corkscrew" growth in mesocotyl region and/or sprout
Dead Seed - Otherwise normal appearing seed that failed to germinate
Weak Seed - Spindly, abnormal sprout that failed to reach the soil surface, seedling roots are shortened or missing
Soil Compaction - Root system shows abnormal bends or is growing at abnormal angles
Herbicide Injury - Roots are swollen, many roots are fused together as one, roots are growing upward or out, not down, leaves are smaller than normal and/or discolored (yellow, brown, etc...)
Managing Emergence Issues
Some of these issues can be mitigated in the future by adjusting planting depth, planting timing, and adherence to label recommendations for fertilizers and herbicides. Other problems, such as disease and insect damage, can be managed by treatment and management pre- and post- planting, as well as making careful hybrid selections to choose seeds shown to provide resilience to the specific pressures in your fields.
In the most severe cases, when emergence rates are predicted to have a significant impact on overall yield, replant decisions may need to be made. Refer to our “Replant Decisions” tip sheet or contact your seed dealer or agronomist for more insight about when to make a replant decision. Replant decisions should not be delayed, as later planting can also significantly impact the percent of optimal yield potential reached in a season.
