Crop Tour-How We Do It

August 17, 2009

Calculating corn yieldsThere is no one magic formula for unlocking the secrets of a corn field’s yield potential. There are lots of them.


“There are about as many yield formulas as there are ways of doing anything,” said Roger Bernard,  the leader of the eastern leg of the Pro Farmer Midwest crop tour.


The basic equation involves multiplying the total corn area by the plant population and dividing by the number of rows.


The Pro Farmer method is a little more involved. It requires a 30-foot length of rope with a hook on it, a tape measure, calculator and basic algebra. Not to mention all the personal supplies tour scouts need.


To fill in the variables in the yield equation, scouts on the Pro Farmer tour walk about 50 paces into a corn field, hook the rope onto a corn stalk and begin counting. They measure the distance between the rows of corn. Scouts then tally the number of corn ears in two rows as they walk up and back the length of the rope. They also pull the fifth, eighth, and eleventh ears of corn from the stalks.


Next, they head back to the car, taking extra care to remember the rope and tape measure. They will need it for the next field. They also need to make note of where they came from because it can take hours to find the way out of a field filled with six-foot high corn stalks if they head the wrong direction.


After emerging from the field, scouts remove the husks and measure the length of the ears. Next, they count the number of kernels around each ear of corn.


Here is where the calculator comes in handy. They divide the total ear count by two and multiply that total by the average length of the ears and the average number of kernels around. Take the sum and divide it by the row width. That’s the projected corn yield for each field.


Repeat this process about 1,000 times, add in a little knowledge after years of  organizing the tour, and Pro Farmer is able to project the corn crop for the entire Midwest.

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