So your neighbor is bragging about his 300 bushel corn crop at the coffee shop. If someone questions whether his corn field really averaged huge that much or not, he bristles and invites them to come look at his yield monitor. He will be glad to pull up the field and let them look a t the yield data for themselves.
There's only one problem with that scenario. Yield monitors are great tools, but if you're using them to document yields, they must be calibrated correctly, and more than once during the season.
Bob Nielsen and Jim Camberato, Purdue University Extension specialists, rely on yield monitor data in replicated strip trials both on private and public farms. However, Nielsen has a specific protocol on how to calibrate the yield monitor based on the plot. He insists that the yield monitor be calibrated correctly before running the plot.
Here's a case in point. I was in the combine cab when we harvested corn in an exclusive Indiana Prairie Farmer/Purdue University Throckmorton Farm plot recently. The first thing to do is calibrate the moisture sensor, then the yield monitor for weight and yield, said Nate Linder, the farm crew person operating the combine.
Calibration involves running at different speeds and weighing loads until you can dial in the right settings, he says. It's all about letting the combine 'know' what happens in terms of grain flow hitting the yield monitor sensor at different speeds.
Since the combine had not been running plots, it hadn't been calibrated recently. As it turns out, it was 9% off based upon weights dumped into the weigh cart. Once he got it calibrated, Linder said it was off a half percent or less.
Say your neighbor's yield monitor was running 10% high. In reality they can run too high or too low if not calibrated correctly. Suddenly his 300 bushel corn might really be 270 bushels per acre, or 250 bushel corn might be 225 bushels per acre. Conversely, 250 bushel corn could be 275 bushels per acre.
You don't know unless you calibrate, experts say.