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OSU Extension

College of Food, Agricultural, and Environmental Sciences

August 14, 2015 - 3:17pm -- Anonymous

If you followed the Ohio Ag Net I-71/I-75 crop tour last week, you may be wondering how your potential corn yield compares to those figures.  Some producers may want a yield estimate to help them make a decision whether to harvest corn for grain or silage.  For yield estimates before corn grain reaches physiological or black layer maturity, the yield component method should be used.  Recently Peter Thomison, OSU Extension corn specialist described this method in the Extension crop team CORN newsletter.

The principle advantage of the yield component method is that it can be used as early as the milk stage of kernel development.  The yield component method involves use of a numerical constant for kernel weight which is figured into an equation in order to calculate grain yield. This numerical constant is sometimes referred to as a "fudge‑factor" since it is based on a predetermined average kernel weight. Since weight per kernel will vary depending on hybrid and environment, the yield component method should be used only to estimate relative grain yields, i.e. "ballpark" grain yields.

  • Step 1. Count the number of harvestable ears in a length of row equivalent to 1/1000th acre. For 30‑inch rows, this would be 17 ft. 5 in.
  • Step 2. On every fifth ear, count the number of kernel rows per ear and determine the average.
  • Step 3. On each of these ears count the number of kernels per row and determine the average. (Do not count kernels on either the butt or tip of the ear that are less than half the size of normal size kernels.)
  • Step 4. Yield (bushels per acre) equals (ear #) x (avg. row #) x (avg. kernel #) divided by 85.
  • Step 5. Repeat the procedure for at least four additional sites across the field. Keep in mind that uniformity of plant development affects the accuracy of the estimation technique.

The more variable crop development is across a field, the greater the number of samples that should be taken to estimate yield for the field.

Example: You are evaluating a field with 30‑inch rows. You counted 29 ears (per 17' 5" = row section). Sampling every fifth ear resulted in an average row number of 16 and an average number of kernels per row of 33. The estimated yield for that site in the field would be (29 x 16 x 33) divided by 85, which equals 180 bu/acre.