By TIM ALEXANDER
Illinois Correspondent EAST PEORIA, Ill. — There’s an old saying about counting chickens before they’re hatched, and the adage rings true concerning estimating corn yields, as well.
Most corn crops are now at least two weeks past pollination, which is the ideal time for producers to assess their potential yields. An educator for the University of Illinois extension is offering corn growers a tried-and-true method for estimating corn yields that can be completed in six easy steps.
“Yield estimates can be helpful to farmers needing to make decisions about harvesting and marketing their 2007 corn crops,” said Robert Frazee, a natural resources educator with the East Peoria extension office. “In most cases, yield estimates for corn are more accurate than for most other crops. This is because the corn crop typically has fewer plants per acre than other crops, the plants are equally spaced and the size of the ears tends to be rather uniform.”
Frazee said the formula for estimating yields is useless until corn plants complete flowering and pollination so that the number of kernels on each ear are fixed. Only then will the formula, known as the “thousandth-of-an-acre” method, produce reliable results.
These fixed figures are key to the formula: a thousandth of an acre in 20-inch rows equals 26 feet, 2 inches; 30-inch rows equal 17 feet, 5 inches; 36-inch rows equals 14 feet, 6 inches; and 38-inch rows equal 13 feet, 9 inches.
The thousandth-of-an-acre method begins with selecting a spot in your cornfield and measuring 1/1000th of an acre with a tape measure.
“Second, count the number of ears that you find in the length of row that corresponds to your row width and multiply that number by 1,000 to get the number of ears per acre,” Frazee said.
“Third, count the number of kernel rows per ear on every fifth ear. (Then) count the number of kernels per row, but do not count immature kernels or either the tip or the butt end of the ear.
“Fifth, calculate the average of both the kernel rows and the kernels per row.”
Finally, insert the calculated numbers from earlier into the following equation to obtain estimated yield per acre: Multiply (number of ears) times the (average number of kernel rows) times the (number of kernels per row) – then, divide this total by 90 to find the yield per acre.
(Note: This formula uses 90,000 kernels as a standard bushel – hence the 90 – and assumes a numerical constant for kernel weight.)
For example: (26 ears) multiplied by (16 rows) multiplied by (42 kernels) equals 17,472. Divide 17,472 by 90, and 194.13 is the expected yield per acre.
“The six-step crop estimate formula should be repeated once for every five to 10 acres in the field, making sure that the sampling provides a random coverage of the field,” Frazee advised. “The closer to harvest this crop estimate calculation is made, the more accurate the yield estimate will be.”
Frazee cautioned that during drought years, kernel weight is usually considerably lower and the formula may tend to overestimate yields. For more information on the corn yield estimate formula, contact him at 309-694-7501, ext. 226, or by e-mail at rfrazee@uiuc.edu
This farm news was published in the Aug. 22, 2007 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee. |
