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Preharvest Downtime Tasks, Part II: Yield Monitor Prep

Though last-minute corn scouting is still critical at this late point in the growing season, don't spend all of your time before harvest in the field and farm shop. Make sure you spend some quality time with your yield monitor, says Purdue University Extension agronomist and corn expert Bob Nielsen.

It starts in the farm office. Dig out your yield monitor's user manual and do your preharvest homework so you know what you're doing when you go to calibrate your monitor.

"Go to your refrigerator for two bottles of your favorite beverage, open each one, and set them down on your desk next to the filing cabinet," Nielsen says. "Next, pick up the user manual, open it, and read through the table of contents or perhaps in the index in the back and look for the section that describes the procedure for calibrating the yield monitor. Drink the first bottle of your favorite beverage and careful begin reading through the yield monitor calibration procedure in the user manual. If necessary, drink the second bottle of your favorite beverage and continue reading through the yield monitor calibration procedure.

"Carefully and clearly highlight each of the calibration steps and, if necessary, transcribe carefully to individual Post-It notes, or use the impossibly small keypad on your smartphone and type them into your favorite Notes app on your smartphone for future reference. If necessary, go to your refrigerator for a third bottle of your favorite beverage and drink all of it," Nielsen adds.

Nielsen is of the garbage in, garbage out school of thought when it comes to calibrating a yield monitor. Though this tool can track and manage a lot of data from your harvest work, it's only as good as its operator. And that starts way before you turn a wheel in the field.

"The essence of yield monitor calibration is to train the black box of the monitor to accurately interpret the electrical signals coming from the impact sensor or the electric eye as they relate to grain flow rates and, therefore, accurately estimate grain yield from the estimated grain flow rates. Sound complicated? Not really," Nielsen says. "The yield monitor simply needs to experience the range of grain flow rates that it is likely to encounter in your fields in order to accurately estimate grain yields that correspond to those grain flow rates. If you only use high yield calibration loads, then the monitor has no idea what to do when it encounters grain flow rates in areas of the field that are yielding significantly lower. That is why many user manuals suggest using calibration loads harvested at different speeds or different numbers of corn rows through the head in order to artificially create that range of grain flow rates (and, thus, yields) during calibration."

The process of calibrating a yield monitor may not be the most enjoyable experience in the world, but it's important. Nielsen says it's important not to underestimate the importance of doing a good job with this preharvest job. Also, be willing to do it at other times in the harvest season so your yield picture remains accurate.

"Calibration requires patience, access to an accurate grain moisture meter, access to accurate weigh scales, and those Post-It notes or smartphone Notes referenced in the previous honey-do item. It sometimes helps if you are also anal-retentive about accuracy," Nielsen says. "Recognize that many yield monitors should be frequently checked for accuracy as harvest moves along into the fall and then recalibrated when necessary. One of the biggest factors that influences the accuracy of yield monitors over time is the change in grain moisture from one field to another. That's why you also need access to an accurate grain moisture meter."

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