Among all precision ag technologies, the yield monitor is one of the most valuable pieces of equipment that not only helps growers in evaluating different management decisions made throughout the year but also guides the crop management decisions for the upcoming year. Yield data from an uncalibrated yield monitor can lead to poor management decisions that can have a lasting impact on a grower’s financial stability. Cotton harvest will be in full swing across the state before we realize it, therefore growers who plan to collect and utilize yield data this season must consider checking yield monitor components and performing calibration procedure to ensure quality data collection. A cotton yield monitoring system is comprised of a mass flow sensor, a ground speed sensor (can be substituted for GPS data in some cases) and a header height sensor along with a GPS receiver and an in-cab display. To minimize any downtime due to yield monitor issues during harvest, growers should consider doing a quick pre-harvest check on the yield monitoring components which includes verifying that the mass flow sensors are clean and free of any debris or obstructions, all systems (including sensors, GPS, and monitor) and wiring harnesses are connected and working correctly, and the header height sensor is installed and functioning as intended.
Mass Flow Sensor Calibration: A mass flow sensor is the most critical component of the yield monitoring system as it measures the flow of cotton through the air ducts while it is transported to the storage basket. Currently, there are two brands of cotton yield monitors (John Deere and Ag Leader) available for cotton pickers. Unfortunately, the Ag Leader yield monitor is no longer available for new purchase. These two systems differ in the way they sense cotton flow. The Ag Leader yield monitor uses optical sensors (Figure 1a) mounted in the ducts for sensing cotton flow whereas the John Deere yield monitor uses a microwave sensor (Figure 1b) mounted outside the air ducts.
While the specific calibration procedure depends on the yield monitor manufacturer (example of a calibration screen on a John Deere 2630 display in the image below), the general calibration principle remains the same:
- Operator starts the calibration or flags a load in the yield monitor display to be used for calibration prior to harvest
- Operator harvests cotton for a certain distance (anywhere from ¼ to ¾ basket of cotton) or until a full round module is created
- Harvested cotton is weighed using a boll buggy equipped with scales or truck scales (usually for round modules)
- Actual cotton weight is entered into the calibration screen on the yield monitor display
- Display software adjusts the calibration curve or factor based on difference between the mass flow sensor reading and actual weight.
Depending on the manufacturer, this calibration procedure can require harvesting three to five different harvest loads and entering each load weight either separately or all together into the display at the end. Therefore, it is critical to follow the calibration procedure specific to the display and yield monitor manufacturer as outlined in the operator’s manual. It is also important to note that any significant change in crop or field conditions (variety, moisture, etc.) during the harvest season may require additional calibrations to be performed in order to maintain the yield data accuracy. Growers should also consider checking the yield monitor components as well as accuracy of yield data regularly throughout the season by performing additional checks as needed.
Wishing everyone a safe and smooth harvest!