Before we talk about any VRA option, we need to understand the basics of how a spreader operates.
A standard spreader has a flow gate position that is manually fixed to a determined setting. Then there is a hydraulic fast gate that is used to open or close the flow-gate opening. The contents (Fertiliser etc.) then drops onto the moving spinner that has its veins set to achieve the desired width and spread pattern.
The flow gate position is determined by looking at a settings chart. This matches speed, width, and rate. This chart will then instruct the user of the correct flow gate lever position setting. The limitations with this standard setup are, the flow-gate is only manually fixed position for one particular speed. Meaning if you drive faster or slower than the set target speed then your rate will be incorrect (either overdosing or underdosing the area of the paddock). This system also relies on the operator opening and shutting the flow-gate when they are spreading over areas they have already been. Resulting in the potential for overlap and/or missed sections.
Option 1 - Rate Controller
Installing a rate controller to your spreader, which consists of 2 electric actuators which are mounted to connect to the flow gate arms, that would be normally manually set to a fixed position. This gives the flow gate opening the ability to adjust to match ground speeds, so the Spreader can achieve the same rate over a variety of ground speeds. The installation of the rate controller is the basis of what VRA needs to be, to be able to control the dose by automating the flow gate.
There are many ways to Look at VRA, the most important one is to acknowledge that every paddock is not completely uniform, so why do we treat them as uniform when spreading fertilisers?
Installing a rate controller is the first step that allows you to achieve the desired target rate throughout a wide range of speeds. Giving the spreader the ability to match the flow required for different speeds. This also allows the use of section control, which limits overlap on headlands and around obstacles within the field resulting in the product being used where it’s needed and ultimately saving you money.
Step 2 - Variable Rate Application (VRA)
The second step is to go VRA (Variable Rate Application) this is achieved by using a digital map to vary control to the “rate controller” that will deliver different crop rates to different zones of the field. This is typically done in conjunction with your agronomist with differing paddock zones created based on soil types and setting target yields. This allows for fertiliser rates that can be set to maximise yield in each particular zone. Then a map is easily created and loaded onto the tractor's ISO BUS system which will then control the target rate in any zone of the paddock. If you don’t have an ISO-BUS ready tractor, OzValue AG has bolt-on solutions/options available.
The benefits are being able to feed zones of the paddock that has more nutritional requirements, perhaps due to a higher yield potential or maybe because of fewer nutrients in the soil. Ultimately VRA gives you the ability to achieve higher paddock averages based on applying fertiliser where the crop requirements and returns are greatest. This can also work the other way, in zones with lower potential yield, you can limit product output.
Step 3 - Variable Rate Application + Scales (VRA-X)
The complete precision ag solution is to add the use of scales on the spreader and integrate this with the VRA rate controller. Using scales alone on a spreader can easily be set up and used without a rate control. This can be used by knowing exactly what’s onboard the spreader when starting an area and then once finishing that area a few calculations can be made to correct the manually set flow gate position, to achieve a more precise target application rate. If scales are used alongside a rate controller, then the scale inputs can be integrated by selecting on-the-go calibration. This uses a set quantity for example 200kgs and gives the rate controller the ability to adjust itself for every 200kgs of product used by changing the calibration factor. This gives you the most precise form of calibration possible as the system is constantly checking and changing the applied rate as needed across the whole field and farm.
