How Does a GPS Fertiliser Spreader Actually Work?
A key driver that would encourage farmers to use a Global Positioning Satellite (GPS) fertiliser spreader is its ability to self calibrate the delivery of material up to 12 times per minute.
Weight cells are critically important in this regard as is the electronic linkages between GPS software with the belt speed of the spreader forward drive of the tractor.
It was an issue discussed in depth by Topcon’s Craig England on a recent Tillage Edge podcast.
GPS fertiliser spreader operation
According to Teagasc, there is a range of technologies on the GPS-controlled spreader, which takes care of the calibration and flow rate adjustment for the operator. The weight cells on the hopper work in a similar fashion, as those fitted on a diet feeder.
A set of electronic rams adjust the shutter openings at the bottom of the hopper. The control box in-cab allows the operator to input the application rate, and the desired working width.
The GPS system picks up the forward speed of the tractor and with all this information combined, the machine can automatically calculate the desired flow rate.
The machine will then measure the actual flow rate by weighing the amount of fertiliser which has left the hopper over a set period of time and it will automatically adjust the shutters at the bottom of the hopper to maintain the required rate.
It is constantly rechecking the calculation and recalibrating the spreader. If the forward speed increases, it will increase the flow rate, if speed decreases, it will decrease the flow rate and so on.
“One thing that could upset the system somewhat would be the inclusion of wet and dry bags of fertiliser in the hopper at the same time,” England explained.
“But the great advantage of a GPS-controlled spreader is that it will adjust the distribution rate of fertiliser while the tractor is moving.”
According to the Topcon representative, the GPS systems acts to open or close off the shutter on a three-point linkage fertiliser spreader.
Intelligence of GPS?
So how does a GPS fertiliser spreader know to differentiate the various physical characteristics of different fertiliser types? At a very fundamental level, some are true compounds while others are blends.
“Each manufacturer now makes an app available. The operator fits in the make and model of the machine plus what discs are to be used,” England said.
“The type of fertiliser to be spread is also inputted, as is the desired width of spread and average ground speed.
“The app will then advise on the vein width that should be used on the disc. Some trailed spreaders change the drop point location.
“A lot of Irish distributors have sent actual fertiliser sample from this country over to the spreader manufacturers, so as to ensure that the apps available have been fully programmed to work well under local conditions.”
