Corn producers should evaluate their uniformity of plant spacing. A well-tuned planter operating at a reasonable speed should optimize uniform plant spacing within a row. Planting at high speeds with a poorly maintained planter can result in a large number of 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 yield loss from non-uniform plant spacing.
#1. Take a 20-ft 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 ft).
#3. Enter the data into a spreadsheet where average plant spacing and standard deviation (SD) can be calculated. See below 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 2 inches is the best spacing uniformity that a commercial producer can typically expect to obtain under normal production planting conditions. They found that if the SD is greater than 3, then the planter needs calibration. If the SD is less than 3, then calibration is not required.
The entire article titled “Estimating Corn Yield Losses from Unevenly Spaced Planting” by Carlson, Doerge and Clay can be found at: http://nue.okstate.edu/CORN/Corn_YieldLoss.pdf