Duane A. Lienemann UNL Extension Educator,
Webster County
August 19, 2011 Edition
We are really getting to the time of year that I love most. It is getting cooler in the evenings, football season is just around the corner, school is back in session and the Nebraska State Fair is upon us! There is something else that always seems to happen this time of year. I would bet that in about every Co-op or coffee shop, or wherever farmers meet, there are probably fresh hand-picked ears of corn being compared and thoughts of harvest are being incubated. I know it happens every year in the local elevator where local farmers succumb to the aroma of coffee and the taste of donuts, cookies and perhaps a sliver of a roll or donut that somebody’s wife may have missing from their kitchen --or more likely an opportune stop at the Qwik Shop or the grocery store. This morning I witnessed the annual comparison of corn ears and heard farmers trying to determine possible yields. Of course the first liar never has a chance, but it did get me thinking back to Agronomy 101 and the lesson I learned years ago on determining potential yield, using an ear of corn. OK, it isn’t quite that easy but there is a simple way that I thought I would share for those that are interested or always wondered how it was done. Of course in today’s world of computers, smart phones, and iPads a lot the work is taken out of it. But I am still of the old school and like hands on and perhaps the use of a pencil once in awhile. Let’s take a look at an age old way of trying to outguess Mother Nature. I know you won’t determine your market strategies with the outcome, or at least I highly suggest that you don’t, but it does give you a little idea of what may be out there. Let’s look at one of the standard methods called the “Yield Component Method.”
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. You should be aware that when below normal rainfall occurs during grain fill (resulting in low kernel weights), the yield component method will overestimate yields. In a year with good grain fill conditions (resulting in high kernel weights) the method will underestimate grain yields. It will be interesting to see what the heat at pollination does to kennel size this year.
First we need to 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. Now grab every fifth ear and then count the number of rows per ear and determine the average. (It will always be an even number.) On each of these ears count the number of kernels per row and determine the average. Do not count kernels on either end that are less than half the size of normal size kernels. Repeat the procedure for at least four additional sites across the field. Now comes the math exercise – here is the formula: Yield (bushels per acre) equals (ear #) x (avg. row #) x (avg. kernel #) divided by 90.
Let’s do an example: You are evaluating a dryland field with 30-inch rows. You counted 24 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 30. The estimated yield for that site in the field would be (24 x 16 x 30) divided by 90, which equals 128 bu/acre. Now if you are mathematically challenged and/or have a computer, you can simply go to an on-line calculator using this same method by going to: http://www.wfsag.com/wfs/calculator.aspx?key=cornyield/.
For the lazy ones out there, I have a simpler but probably less accurate method. This method is to select an ear (or ears) that represent the average ear size in the field. This would be appropriate for the example that I talked about of farmers bringing in representative ears to coffee. Now simply count the number of kernels per ear (# rows x #kernels/row) and then multiply that number by the standard multiplier of 0.300 to get a very rough yield estimate. To add a little more accuracy to the simplest method, you can count the kernels on each ear of 10 consecutive ears in a row. Then you average the counts from the 10 ears to have a better estimate of kernels per ear. Let’s do an example: You grab an ear and count 12 rows per ear and 50 kernels per row which will equal 600 kernels per ear. Take that 600 x 0.300 = 180 bushels/acre. Simple!
While this method is a very fast way of estimating yield, it makes several assumptions and could be misleading. The multiplier of 0.300 assumes 27,000 ears per acre and an average seed size of 90,000 kernels per bushel. Changes in either ears per acre or kernel size affect this multiplier. Seeding rate, stress on developing plants, and pests can all change the final number of ears per acre. Not every field will have 27,000 ears per acre. If you want to adjust seed size based on the growing season, you can use the multipliers from a chart, that I can provide you, that can come in handy and helps accuracy in making your yield estimate. This chart will adjust for seed size and population counts. It would be fun to have several farmers to try one of these methods and then see just how close they are, my guess on average we will be off about 20 bushels per acre either way.
On a side note for the BH Co-op crew…How much $7 corn does it take to feed a $1,000 pig? I just had to put that in…. I would be remiss if I didn’t close the column this week by wishing our South Central Nebraska youth and their parents the very best as they prepare their exhibits for the 2011 Nebraska Sate Fair. We will be taking static exhibits down to the State Fair this week and then of course Labor Day weekend is the big weekend for livestock. Good Luck to our 4-H and FFA Exhibitors!
The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu or go to the website at: http://www.webster.unl.edu/home
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