Submitted by

Wayne Flanary, Field Specialist in Agronomy

The last few weeks, I have had the opportunity to measure corn and soybean yield plots and the growers took the harvested grain across the scale for weight and moisture measurement. These were yield contests for both corn and soybeans and the yield monitor yield data was much higher yielding than the scale measured grain yield from a physically measured area of the field.

Yield monitors estimate grain yield by converting electrical signals from sensors in the clean grain elevator of the combine into grain flow during travel. Yield monitor calibration is a series of steps to ensure the yield monitor software is converting these signals into accurate grain flow rates.

Typically, yield monitor manufacturers require loads of grain that represent different flow rates you would find during harvest of your field. Most University Extension staff would suggest between three to six loads to calibrate a yield monitor. This type of calibration increases accuracy at different speeds and yields found throughout the field and will help the yield monitor interpret the electrical signals for low and high grain flow.

Yield monitor accuracy is excellent if the monitor is well calibrated. Yield errors may be as much as eight to 10% late season if the monitor was only calibrated at the first of the season. Without any calibration, who knows the size of error.

Keeping yield data for future use requires accuracy. Data can be used to monitor fields and areas of fields, conducting experimental trials and checking hybrids or variety comparison and among many other uses. Future uses include analyzing data over years to determine profitability of fields.

Accuracy can be affected by grain moisture, temperature change and field topography. We need to recalibrate through the season to maintain accuracy. Also, calibrate the combine grain moisture sensor, zero-flow and temperature sensor.

Be sure to keep the user’s guide handy and follow a checklist of calibration steps. Remember, grain yield monitors are measuring electrical signals from a sensor.

For more information, call 816-279-1691, University of Missouri Extension.