Combine Calibration and Yield Mapping Best Practices for Wheat

October 7, 2024

KEY POINTS

  • The first step for combine monitor calibration is to follow the specific calibration method outlined in the manufacturer's owner operation manual.
  • Understand the formats and directories used by the yield monitor to store the harvest data used by the data service provider.
  • Back up data from the previous season, if not already completed.
    • Copy each season's data to a folder with a name that describes the yield data for the year of harvest
    • During the harvest season monitor data can be lost, damaged, or changed so store multiple backup copies of the display/raw yield data in various locations.
    • Delete old files from the memory card or USB drive.
    • Delete old files from display memory if close to full.
  • Make sure all memory devices and USB drives are working properly.
  • Contact your equipment dealer to make sure you have the most recent software and firmware upgrades.
  • Inspect all sensors, wires, cables, and connections to make sure that they are clean and working properly.
  • Check all combine functions to ensure that everything is working correctly and adjusted.
  • Make sure to set proper platform cutting width.1

Introduction

Yield monitors do not directly measure grain yield but instead estimate yield by using readings from sensors mounted in a combine. These sensors measure grain flow over a distance traveled and the width of the header to determine the area harvested. Sensors also estimate grain moisture and temperature. Monitors collect this information every second or two and store it on a memory device, and the firmware/software uses an equation to estimate dry grain yield per acre for that area.

It is important to calibrate the combine yield monitor (if the combine has a monitor installed) prior to harvest or when switching crops to accurately record harvest results. Multiple yield monitor systems are available from different manufacturers, and it is important to follow the calibration procedures outlined in the operation manual as each monitor may be different. After calibration, the harvest record allows the producer to create a yield map for post-harvest analysis, including any test plots, to support crop management decisions that can positively affect profitability for following seasons.

Grain yield monitor.
Figure 1. Grain yield monitor.

What is yield monitor calibration?

Calibration is the act of baselining ̶ matching the combine’s sensors estimated recorded weight to a certified scale weight to have the most accurate yield detection system, second by second, as the combine moves through the field.2

Before yield monitor calibration takes place, it is important to make sure the support equipment used to make these calibration measurements are accurate. If the weight calibration uses a grain cart to check the harvest weights from the combine, it important to make sure these grain cart weights match the weights checked with a certified scale weight.

If a producer uses a hand-held field moisture tester to determine grain moisture, take the time to compare this moisture reading and calibrate this moisture tester with a moisture test at a certified scale. The moisture calibration will need to use the same grain type that the combine will be harvesting. If these tools are not giving accurate readings, it will only increase the inaccuracies in the yield data collected.

A typical three step calibration process:

  1. Harvest a calibration test load.
    • Loads should be between 3,000 to 6,000 lbs for multi-point calibrations.
    • To calibrate a single-point yield monitor, use a larger load size of up to a full grain tank.
  2. Use a grain cart, weigh wagon, or truck weight on a certified scale to confirm the calibration load weight.
  3. Enter the confirmed weight into the yield monitor display.3

Testing multiple test loads is important to increase monitor accuracy. Harvesting a minimum of four load samples under different load conditions is important to establish the calibration curve needed to reduce yield estimate error. Start with a load when the combine is operating at full load capacity and then weigh up to six other loads when the combine is harvesting at variable load capacities. Harvesting at different ground speeds at less than full load capacity simulates harvesting at low and medium yield environments. Each calibration load should be between 3,000 and 6,000-lbs (50 to 100 bushels of grain) and calibration weights should not be taken from the headlands or areas in the field with variable yield conditions like heavy weed pressure or highly variable soil conditions.4

Yield Monitor Sensors

The yield monitor uses multiple sensors to accurately estimate yield. If any of these sensors are not functioning properly or are not accurately calibrated, then the accuracy of the yield monitor will be reduced.

Grain yield monitor sensors include:

  • Grain flow sensor (weight)
    • Mass impact
    • Optical sensor
  • Zero-flow combine vibration sensor
  • Grain temperature sensor
  • Grain moisture sensor
  • Travel speed sensor (if ground speed is determined by GPS, then this sensor may not be needed)
  • Header position sensor
  • Clean grain elevator speed sensor (not all mapping systems use this sensor to improve accuracy of grain flow measurements)
  • Lag time setting

What can influence calibration accuracy?

Yield monitor accuracy can change when harvesting the crop with the following conditions and a recalibration should take place when:

  • Harvesting yield levels outside of the range of grain flow rates used for calibration.
  • Harvesting late in the season when temperature and grain moisture content are often quite different than temperature and moisture used for the initial calibration.
  • Harvesting when there are differences in grain test weight, grain shape, and field topography.4

Conclusion

The importance of a pre-harvest combine calibration is critical for an accurate estimate of area specific yield comparisons. Although it is a busy time when getting ready for wheat harvest, it is important to set aside time to recalibrate the yield monitor to ensure accuracy and data reliability to help identify yield variability within a field. This allows the opportunity to help correct issues for the following crops. Important management decisions that can be made clearer with yield monitor data include varieties and product selection, fertility, tillage, fungicide applications, or planting rates. A single year yield map is a good start for a producer when using this precision agriculture tool, but multi-year maps can generate more dependable and accurate data needed to make better management decisions. A post-harvest calibration is also an option, by keeping accurate field load weights separate for each field. This can provide a field-by-field comparisons but does not allow for use of accurate data for specific areas in a field. For more information about combine calibration, read Combine Calibration. During the harvest season producers should back up yield data every other day or so on another storage devise or the cloud to protect against any potential loss of harvest information. The use of a virus security protection program is also highly recommended to help protect against any potential viruses damaging valuable yield information.



Sources:

1Hawkins, E., and Fulton, J. 2024. Tips for calibrating grain yield monitors—Maximizing value of your yield data. ANR-8, Ohio State University Extension, Ohioline. https://ohioline.osu.edu/factsheet/anr-8

2Jodlowski, C. 2023. Calibration is key to harvest data utilization. Illinois Soybean Association. ILSOY Advisor. https://www.ilsoyadvisor.com/calibration-is-key-to-harvest-data-utilization/

3Powell, L., Darr, W. and Bergman, R. W. 2020. Tips for calibrating your combine's yield monitor. Iowa State University. Extension and Outreach. Integrated Crop Management. https://crops.extension.iastate.edu/blog/levi-powell-matt-darr-ryan-w-bergman/tips-calibrating-your-combines-yield-monitor

4Nielsen, R. 2020. Yield monitor calibration: garbage in, garbage out. Purdue University Extension. Corny News Network. http://www.kingcorn.org/news/timeless/YldMonCalibr.html

Web sites verified 08/15/2024. 1710_441251