Corn Stand Evaluation

Summary

Many different stress factors are capable of reducing corn stands, such as:

cold or wet soils
insect feeding
unfavorable weather conditions

Taking Stand Counts

Take several sample counts to represent the field.
Sample a length of row equal to 1/1000th of an acre.
Measure off the distance appropriate for your row width, count the number of live plants and multiply by 1,000 to obtain an estimate of plants/acre.

Estimating corn plants per acre — When an injury event such as frost or hail occurs it is best to wait a few days to perform a stand assessment, as it will allow a better determination of whether or not plants will recover.

Stand counts should be taken randomly across the entire area of a corn field being considered for replant. — Stand counts should be taken randomly across the entire area of a field being considered for replant; this may include the entire field or a limited area where damage occurred. (photo above)

Growth of green tissue near the growing point indicates that this corn plant would have recovered. — Growth of green tissue near the growing point indicates that this plant would have recovered. (photo above)

Soft translucent tissue near the growing point indicates that this corn plant will not recover. — Soft translucent tissue near the growing point indicates that this plant will not recover. (photo above)

Other Factors to Evaluate

Stand uniformity - An uneven stand will yield less than a relatively even stand with the same number of plants.
Plant health - Plants that are severely injured or defoliated will have reduced photosynthetic capability and a lower yield potential.

Young corn plant defoliated by hail. — This plant was defoliated by hail. New green tissue indicates that it is recovering, but its yield potential has been reduced.

Corn yield is influenced by stand density as well as stand uniformity:

Variation in plant size can have a negative impact on yield
Uneven emergence timing leads to uneven plant size

Several Factors That May Lead To Uneven Emergence:

Variation in soil moisture
Poor seed- to- soil contact due to working or planting into wet soil
Variation in soil temperature caused by uneven crop residue distribution
Soil crusting
Insects or disease

Late-emerging corn plants are at a competitive disadvantage with larger plants in the stand. — Late-emerging plants are at a competitive disadvantage with larger plants in the stand and will have reduced leaf area, biomass, and yield.

Impact of uneven emergence on yield

Impact of uneven corn plant emergence on yield.

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