By Dusty Sonnenberg, CCA, Ohio Field Leader

Ask an expert in the industry about the importance of calibrating yield monitors to collect harvest data and they will most likely tell you, “It’s about how much you value your data.” That was the response from Matt Liskai, owner of Green Field Ag in Gibsonburg, Ohio. Matt has been working with yield monitors and other precision agriculture equipment since they first came on the scene in the early 2000s.

“Everyone has a different philosophy when it comes to calibrating their yield monitor for harvest data,” Liskai said. “Some calibrate their yield monitors once a season, and some will calibrate for every field or variety. It’s about the value you place on the data you are collecting and the decisions you will make with it. You need to ask yourself how important is it that the data you collect is accurate?”

According to John Fulton, OSU Extension Specialist for Precision Ag, and Elizabeth Hawkins, OSU Extension Agronomic Systems Field Specialist, geo-referenced yield data (i.e. yield maps) are being used to provide precision agriculture insights and recommendations at the field level. Yield maps help growers understand end-of-year performance within fields, and can also be used to characterize in-field variation. Information about the variation is often used by service providers to deliver prescriptions, recommendations, or other information back to the farmer. Because yield maps continue to be an important source of information for making decisions, proper management of the yield monitor is critical to generate accurate and reliable yield data. Grain moisture and test weight, along with grain flow through the combine, will vary within passes and across fields. Therefore, the flow and moisture sensors on combines must be calibrated to these expected conditions in order to log accurate data.

“It worked just fine when I put it in the shed after last season. Now it doesn’t work.” That is a phrase Liskai has heard many times.

“Sometimes the problem is as simple as a 5 amp fuse,” Liskai said. “The moisture sensor has a fuse that can blow under certain conditions and prevent a reading. Another issue some guys run into is that the mapping and recording of data doesn’t start at the right time. This obviously can cause issues with the maps. It occurs because with many systems, the header height activates the acre counter. The header sensor may need adjusted to reflect the height you are cutting at, and when the counter should start.”

He acknowledges that not all farmers are running combines with GPS for geo-referenced mapping. Some older machines with first generation yield monitors will base the data calculations on ground speed. On some machines, the wheel speed sensor may need calibrated if they are not using GPS.

“Sometimes the issue is a combination of things, and it takes time to systematically check each component to find the issue,” Liskai said.

Fulton and Hawkins provide several reasons to routinely calibrate yield monitors.

  • It helps collect accurate yield estimates so yield variability across the field is accurately represented by the yield map; especially this growing season considering the expected field variability.
  • It can be used to generate accurate prescriptions and profit maps based on your yield maps. The generation of variable-rate fertility and seeding maps are frequently based on yield maps with few services creating profit maps to evaluate areas of profit and loss.
  • Yield maps have become a baseline data layer to assess management risks and the allocation of inputs. Precision agriculture practices have shown to provide feedback to improve profitability and helping confirm the best practices and input selections for a farm operation.

Yield monitor best practices to use pre-harvest and during harvest

  • Be sure to update firmware and/or software for the yield monitoring systems. If necessary, contact your equipment or technology service provider about available firmware updates and where they can be downloaded.
  • Most yield monitors use a mass flow sensor at the top of the clean grain elevator. Due to the grain impact, the plate will wear to the point of developing a hole if it isn’t replaced soon enough. The wear that occurs changes the reading from the mass flow sensor. Be sure to replace the plate if wear is evident. Don’t neglect to recalibrate after replacing yield monitor components. This recalibration is necessary to ensure accuracy of the yield monitor. A more simplistic explanation is that a worn impact plate can result in an incorrect yield reading on the display. It is important to not overlook the yield mapping system as a worn component will throw off yield readings.
  • Update and/or configure DGPS. Software related to auto-steer, yield monitors and other GPS-based systems require separate attention. Licenses must be renewed. Calibrations and parameters must be updated or confirmed — especially if the display in the combine cab was used for planting or spraying earlier in the year. It’s necessary to meticulously switch every setting and value, from machine dimensions to type of crop and operation, so they are relevant to harvest operations.
  • Check auto-steer operations and that previously used AB/guidance lines are available within the display. Remember, you may have to adjust sensitivity settings.
  • It is also important to calibrate yield monitors for every crop, each season to ensure that all data being collected is as accurate as possible. The yield monitor needs to “be taught” how to convert the readings from the mass flow sensor into yield; therefore, it is necessary to show the yield monitor the range of yield conditions it will encounter throughout the season.
  • It is wise to periodically check the calibration throughout the season to be sure the data being collected is still accurate.
  • Grain moisture and density can vary between crop fields and, at times, vary significantly within a field. Accounting for changes in grain moisture and density improves the accuracy of yield estimates.
  • Remember to recalibrate if harvest conditions change. For example, if: yield monitor components are replaced or adjusted; grain moistures increase or decrease by over 6% to 8%; or after a rain shower but still dry enough to harvest.
  • The use of grain carts to calibrate yield monitors can be acceptable as long as it weighs accurately compared to certified scales. One should make sure the weigh wagon is on level ground (less than 2% slope) and stationary for a few seconds before documenting the weight.
  • Bring along field notes to review during harvest as crop conditions vary or issues are observed.
  • While harvest is a busy time, taking notes and images during harvest (especially if conducting on-farm research) can be valuable data when finally sitting down for post-harvest analysis and summary. Notes and images can help document important information.

For more information on calibrating yield monitors, check out the Ohio State Precision Ag website at plus read the Extension Publication “Tips

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