farmgate: Is Your Yield Monitor Really Monitoring Your Yield?
Last year your corn was heavy, and test weights were 56 pounds and up. This year your corn has patches of diplodia fungus in the field and fluffy corn may be a good description of some of it. Will your yield monitor be able to adjust itself for the difference and give you a reliable reading of bushel yield? (Grimace) Probably not.
You have been relying on a yield monitor for field mapping, reports to landowners, and keeping your lender apprised of your financial prospects. But has that piece of equipment been providing a service or a disservice? Ag engineer Matt Digman at the University of Wisconsin suggests you monitor your yield monitor. His latest newsletter says your yield monitor depends on many sensors on the combine but needs to ensure that all of them are giving it the best information possible. If the brain in the system is misinterpreting what it is being told, it will not be able to make its calculations properly and give you reliable information.
Digman says there are specific steps that must be taken by you and the yield monitor to ensure it is accurate:
1. Determine the area that has been harvested. Each brand may have a different way of doing it, but it needs to know when the combine is actually operating. That is done with a sensor that indicates the header is at harvest height and the separator is operating.
2. The monitor needs to know the width of the swath you are taking or number of rows being harvested. You will need to tell it the number of rows or width of your header.
3. The width combined with the speed of the combine allows the yield monitor to calculate the area harvested within a given amount of time, which is usually reported in acres per hour. A linked GPS system will automatically calibrate speed. The yield monitor will use the area harvested combined with the grain sensor to correct its calibration.
4. When the monitor has computed the area harvested, it needs to know how much grain has been taken into the combine. Digman says development of a reliable weighing system has eluded ag engineers, so the task depends on sensors that detect the flow of a mass of grain entering the combine. Sensors that detect the volume of grain in the clean grain elevator will store that information until you can enter the aggregate weight of grain from an elevator scale ticket. At that point the yield monitor has a good indication of the density of the grain (either heavy or light test weight), and can compute its estimated yield.
If the density of the corn is uniform throughout the field the yield monitor will provide a perfect indication of the yield. But if patches of diplodia-damaged fluffy corn are harvested, there will be a variation in the accuracy of the unit. Digman recommends a recalibration of the unit every 2-3 weeks or more often if crop quality changes.
Another technology used by yield monitors requires an impact plate that the grain hits as it moves from the clean grain elevator into the combine tank. The accumulated force on the impact plate keeps a running calculation of the yield. The impact plate will not only wear over time and provide varying reliability, but will also need regular recalibration depending on grain quality. The impact plate creates a small current that increases in voltage as the total weight of the grain increases as it hits the plate. Digman says, “What this means for the operator is that multiple calibration loads are necessary to ensure yields collected at very high and very low mass-flow rates are accurate.”
Yield monitors vary too widely in how they are calibrated to be discussed here, but Digman says follow the instructions closely to ensure you have an accurate yield calculation as is possible for that unit.
What about moisture of the grain, since it determines number of bushels? Digman says yields must be corrected for moisture, since grain that is wet and heavy will give you a false hope of high yields.
Summary:
Yield monitors can be valuable tools in your information technology process, however they have to be calibrated to the density of the grain, the area being harvested, and the moisture of the grain to give an accurate report of your yield. Different manufacturers will rely upon sensors in different locations in the combine, but all have to be working properly to each other to ensure accuracy. The calibration process may be complex for some units, but it must be accomplished regularly to ensure that yield reports will accurate describe the changing condition of the grain being harvested.
Posted by Stu Ellis on October 7, 2009 12:38 AM to farmgate