Uniform Plant Spacing in Corn
Corn farmers should evaluate their uniformity of plant spacing every spring, following planting. A well-tuned planter operating at a reasonable speed should optimize plant spacing within a row. Planting at high speeds with a poorly maintained planter can result in many doubles (two-plant hills) and skips (missing plants), both resulting in lost yield potential for the field.
There is a quick and easy way to determine yield potential and/or yield loss from non-uniform plant spacing:
1. Take a 20-foot tape measure and lay next to the row of plants to be evaluated for uniformity of spacing (see figure below).
2. Record the location within each row in inches of each corn plant (up to 20 feet).
3. Enter the data into a spreadsheet where average plant spacing and standard deviation (SD) can be calculated. See below table for an example. Yield loss due to non-uniform plant spacing is estimated using the following equation:
So, what should producers be aiming for? Doerge and Hall (2000) previously found a standard deviation of two inches is the best spacing uniformity that a commercial farmer can typically expect to obtain under normal planting conditions. They found that if the SD is greater than three (seen above), then the planter needs calibration. If the SD is less than three, calibration is not needed.
“Estimating Corn Yield Losses from Unevenly Spaced Planting” by Carlson, Doerge and Clay can be found at https://nue.okstate.edu/CORN/Corn_YieldLoss.pdf.