Using Your GMW Fertiliser Spreader – A Guide for Growers
Got a new GMW 1-tonne fertiliser spreader? This page has everything you need to use it safely and get the best results in your paddock. Whether you’re setting up for the first time or training a worker, start here. Watch the videos, follow the steps, and use the calculator to get your settings right.
Note: This guide is specific to the GMW 1-tonne hydraulic fertiliser spreader, designed and built by Larry Grant of GMW Engineering, Innisfail.
Read this before you start.
- Never put any part of your body in the bin while the spreader is connected to the tractor.
- Never put your hands, feet or any object near the spinner outlets while it is connected.
- Always be seated in the tractor before operating. Check that the throw path is clear – fertiliser can contain solid objects that eject at speed and cause serious injury.
- Do not operate this machine – or let anyone else operate it – without proper training.
- Before connecting hydraulic hoses: turn off the tractor, release pressure at the male connectors, then connect. Make sure fittings are fully seated before you start.
- Do not operate with guards or warning decals removed.
- Hydraulic hoses and motors get hot during use. Do not touch them until they have cooled down.
- Be careful when the spreader is fully loaded. Even though it can carry up to 1 tonne, the weight can affect tractor balance on hills. Take extra care on uneven terrain.
- Avoid fertilisers that may contain rocks (for example, lime picked up from a storage pad without a concrete base). Rocks can jam the worms.
Watch the video first, then follow the steps below.
- Turn off the tractor before connecting anything.
- Release pressure at the male connectors before attaching hydraulic hoses.
- Connect the hydraulic quick-release fittings and make sure they are fully seated before you start.
- Once connected, check the throw path is clear before operating.
Watch the video for a visual walkthrough of every control on the machine.
Your spreader has two main controls:
Worm speed controller (output)
This controls how much fertiliser comes out. Check the output by pushing the button on the digital readout. As a guide, a setting of 40 is roughly 10 kg per minute for one side – 20 is half that, and 80 is double. Each worm (left and right) can be turned off independently while the machine is running, which is useful for headlands or part-paddock applications. All fertilisers behave differently, so always calibrate for your specific product.
Needle valve (spinner speed and throw)
This controls how fast the spinners turn and how far the fertiliser is thrown. Turning anticlockwise slows the spinners and reduces throw distance. You can also adjust throw by raising or lowering the three-point linkage – a higher position increases throw distance. On most tractors you will need to stop the machine before adjusting the linkage.
What you need: A bag or container to catch product, a set of scales, a measuring tape, and a phone or watch to time yourself.
Before you calibrate – get the machine ready
Follow these steps first, in order. This makes sure your worm is fully charged with product before you start measuring.
- With no product in the machine, set your worm speed to your saved speed. Set spinner speed to low – this makes product easier to catch. (In this guide we use worm speed 35.)
- Fill the spreader with at least 100 kg of product.
- Start the spreader with both worms turned off.
- Run the spreader for 30 seconds with only the left worm on. Catch the product and put it back in the bin. (This charges the worm so your measurement is accurate.)
- Turn the left worm on for exactly 1 minute. Catch all the product in a bag or container.
- Weigh what you collected and multiply by 2. This is your output per minute for both worms.
Work out your tractor speed
- Drive your tractor over a measured 100 metres at your normal paddock speed and time it in seconds.
Use the calculator
Enter your numbers below to find out your exact worm speed setting.
Spreader Calibration Calculator
Enter your numbers below to find out the exact worm speed setting you need for your target application rate.
Band vs Broadcast Application
Your spreader can apply fertiliser in two ways:
Band application (default)
Fertiliser is directed in a concentrated band along the row. This is the standard setup – no changes needed.
Broadcast application
To switch to broadcast, remove the 3 bolts holding the band director plate. This spreads fertiliser more widely across the paddock. When switching back to band, refit the locknuts when replacing the plate.
Don’t skip this. Watch the video for the full process.
After every use
Clean the spreader thoroughly. Fertiliser left sitting in the machine can form lumps that get ejected when the machine restarts – this is a safety risk and can damage the equipment.
Greasing
- Grease with multipurpose grease after every use.
- There are 6 grease nipples – one on each bearing and one on each spinner shaft.
- Pump until the bearing is full.
If storing for an extended period
- Pressure wash the machine.
- Cover all hydraulic fittings with Tectyl or a similar protective coating.
Need Help?
📞 0408 642 116
✉️ [email protected]
✉️ [email protected]