When it comes to harvesting, every grain counts – literally. Modern harvesters are equipped with advanced technology, including grain loss sensors to help growers monitor grain losses and maximise productivity during harvest. However, technology isn’t always perfect. Enter the “ghosts” of harvesting, with losses slipping past sensors and giving false readings. Using the right calibration tools can help ensure you’re getting an accurate picture of your harvest losses.
Sensors are typically mounted at the rear of the combine harvester with various technologies used including optical, acoustic, capacitive and piezoelectric being the most common. The piezoelectric sensors detect impact vibrations caused by grain kernels striking the sensor plates and convert the mechanical energy into electrical signals. The more grains hitting the sensor, the higher the loss reading.
John Deere S600/S700/X9 harvesters use piezoelectric sensors.
There are three challenges with today’s harvest loss sensors.
- What is the actual loss? Is it 300 or 30kg/ha? While grain loss sensors provide a useful indication of harvester losses they cannot provide an actual grain loss number. Without calibration it is unknown if that loss is acceptable or not.
- False, or ‘ghost’, readings occur when non-grain material—such as straw, chaff, or other debris—strikes the sensor plate, triggering inaccurate indications of grain loss. This can lead operators to make unnecessary adjustments to the harvester, including reducing operating speed
- No reading occurs when grain remains trapped in the straw and fails to be read by the sensor almost as if an unseen hand were holding it in. This can result from straw size, moisture content in the straw or how the machine operates.
During the summer harvest of 2025, David Keevers and Peter Broley from Primary Sales, along with Jim Pike from Bushel Plus, visited Morella Ag near Toobeah, Queensland. They were joined by precision ag consultant from GRoh Ag, Christian Capp, to conduct grain loss testing during sorghum harvest.
Using the Bushel Plus harvest loss drop trays, they measured machine losses (sieve and rotor) on the John Deere S780. While in the cab there were no losses showing on the screen and initial drop tray measures showed no losses out wide to the left or right of the rear tyres, losses were visible on the ground in the centre of the machine behind the harvester. The next step was to find out if these losses were off the front or out the back of the machine.
The guys from Primary Sales and Bushel Plus did several drop tray tests, dropping the tray remotely off the axle whilst still allowing the harvester to continue to harvest. While there was grain in the pan, lifting the tray after the tests and looking at what was under it, clearly showed no grain under the pan. The learning:
there were negligible losses coming off the header-front, but losses were coming through the machine. The losses from several drop trays tested showed losses of 250-280kg/Ha (See screen capture from Bushel Plus App).
Still allowing the harvester to keep harvesting, the guys asked the operator to make individual harvester setting changes and then tested the impact of these changes. These changes included fan speed down 30 and then up 30, top sieve open to 16, bottom sieve open to 10. Through this process they dropped losses from 9.4% to 1.6% (280kg/ha to less than 50kg/ha). An extrapolated saving over the 800ha program of $55,000.
The testing work using the Bushel Plus drop pans identified that sieve loss was occurring despite these “ghouls” not being visible to sensors. Sensors can be bypassed where spinners on John Deere machines push material to the centre of the machine or where the straw holds on to the grain.
The Morella example serves as a reminder that drop trays are essential for accurately determining harvester losses and for ground-truthing sensor readings. By measuring the grain in the Bushel Plus Drop Tray, operators can compare real loss (% grain loss) with the sensor’s output.
Without proper calibration, grain loss sensors can mislead operators, resulting in higher losses, reduced efficiency, and increased costs. Whether using a manual setup or an automated system ((CEMOS™, Harvest Command™, IntelliSense™ or Combine Advisor™), regular calibration is essential for precision harvesting and optimum harvester performance.
Loss sensors are the backbone of all harvester automation systems, using real-time loss data from the sensors to adjust setting for all the modes of operation. Once the actual grain loss is determined from the drop tray readings, the sensor’s sensitivity can be calibrated to provide more accurate readings, helping operators know when the loss is within an acceptable range. Regularly calibrating your sensors is a game-changer, keeping harvest losses low, efficiency high, and costs in check—something every grower can appreciate when it comes to the bottom line!
Primary Sales (08) 9250 3500 sales@primarysales.com.au
GRoh Ag 0400 077 971 www.grohag.com.au
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