As many farmers continue to wait patiently for soil temperatures to rise before spreading, now is the ideal time to make sure your fertiliser spreader is set up and ready for the season ahead. As the cost of fertiliser continues to rise, it is vitally important that the fertiliser spreader is in good working order and set up to spread accurately and evenly.
Inspecting the spreader
Start by ensuring the machine is mechanically in good shape. This is something that should be done at the start of every season.
Pre-season maintenance will be much easier if the machine has been washed down and oiled before storage at the end of the previous season. A fertiliser spreader is one machine in particular that should ideally be dry stored over the winter months, protected from the elements to help prevent corrosion.
Examine the frame, the hopper and the spreading mechanism for signs of wear or fatigue, such as severe corrosion or cracks that may have a negative effect on performance or load carrying ability. After examining the frame, check the hopper for cracks and that shutters are opening and closing properly and the agitators are in good order, with no play in the bearings. Wear in components such as shutter linkages and disc bearings can all have a negative effect on a spreader’s performance.
On a disc machine, examine the disc bearings for wear by shaking each disc vertically, assessing the level of play. Ideally there should be none. If there is excessive play then investigate this further. Bearings or shafts may need replacing depending on their condition. Wagtail spreaders should also have their spreading mechanism checked for wear and that the bearings are in good order. The diffuser band on the wagtail spout should be intact and not broke as this would have a major effect on the spread pattern.
Vanes that show a rough or wrinkled surface and a leading edge that is no longer straight will need replacing. Spreading vanes are critical in the performance of any spreader. Given the way that these machines operate, what one may class as a small bit of wear will generally have an increasingly negative effect on spread pattern the wider the bout width.
All other moving parts should move as intended. Higher-specification spreaders equipped with a headland management system should be checked over that the system is engaging and disengaging. Directional change levers on the gearbox should be properly engaging and disengaging (should slot in and out of position easily). Finally, grease all lubrication points including the PTO shaft before mounting the spreader to the tractor.
Mounting the spreader
The first thing to do before mounting the spreader is to measure (using a tape) that both lift arms are level. Check that the pressure in both rear tyres is equal. An unlevel spreader may not empty evenly and may have its spread pattern affected. Once mounted on the tractor, ensure both stabilisers are tight, allowing no lateral movement and that the spreader is mounted to the centre of the tractor’s track width.
Now raise the spreader to the correct working height, the general rule of thumb is to have a distance of 75cm from the top of the crop to the spreading mechanism (discs or wagtail). Now, adjust the toplink to the angle advised by either the spread chart or manufacturer. Once the spreader is correctly mounted it is important to make sure it is correctly calibrated and set to the desired application rate.
Settings and calibration
Setting a spreader is easier than most may think. A disc machine has two main areas of adjustment – fertiliser flow rate and disc and vane settings. Flow rate is the only adjustment of a wagtail machine. The steps involved in setting the desired flow rate on both machine types is quite similar.
Flow rate is adjusted by moving the regulator. Obviously, the one regulator setting for a desired application rate will not work for all fertilisers as the flow rates of each vary depending on characteristics of the sample (shape, size and brand) – no two samples are the same. Knowing the correct flow rate is essential if a correct application rate (kg/ha) is to be achieved. Setting the regulator only ensures that the correct amount is coming out of the machine.
Further adjustments may need to be made to ensure that fertiliser is being spread evenly. These adjustments will vary for each machine, so refer to calibration settings for your particular machine.
Depending on the manufacturer and model, a number of the following adjustments may need to be made: vane type and position, fertiliser drop point, disc size and toplink angle.
All may need to be adjusted in accordance with the spreading chart at the set working width (m), application rate (kg/ha), forward speed (km/h) and type of fertiliser being applied. These adjustments vary from brand to brand so you will need to refer to the manufacturer’s settings and spread charts (in spreader manual or settings book).
Most manufacturers have smartphone apps that show spread charts and have calculators that allow you to input information such as fertiliser type, application rate, forward speed and spreading width and then display the machine settings to achieve this.
Most manufacturers have a huge selection of fertiliser types and brands already tested in their test halls. The spread chart will also indicate the accurate kg/min for each particular fertiliser for a machine. However, fertiliser will vary over time and calibrating the flow rate is the only way to make sure that the output setting is fully correct.
To do this, shut off one side, and remove the disc on the other side before fitting on the calibration container or you can use a bucket. The spreader should be run for one minute while the container/bucket gathers the fertiliser. The PTO should be running during the calibration as the agitator at the bottom of the hopper needs to be moving to ensure an even and steady flow of fertiliser. After one minute, the container’s weight should match the kg/min rate as displayed by the app or spread chart.
Pendulum spreaders or wagtail as they are more commonly referred too, require no further setting up once mounted correctly and the flow rate has been established. This is done using the regulator, depending on working width (m), application rate (kg/ha), forward speed (km/h) and type of fertiliser being applied. Many manufacturers have smartphone apps that allow you to input all these variables along with the fertiliser type.
The app will then provide you with a setting or spread chart to suit the fertiliser being used – granular, prilled or even seed. A wagtail spreader’s flow rate should be calibrated to ensure that it spreads what it is set to spread.
The calibration procedure is similar to that of a disc machine. You remove the spout and fit on a calibration container. The app or spread chart will provide a rate in kg/min which should match that coming from the spreader.
Run the spreader at the setting recommended by the app or spread chart and then weigh the fertiliser that comes out over the course of the minute. If the two figures don’t match up, some fine-tuning may be required.
In the field
Once the machine has been correctly set up, it is down to the operator to drive accurately, ensuring both the PTO and forward speed is correct and the correct bout width is being maintained.
To check the spread pattern of the fertiliser across the bout width, a tray test should be carried out. This involves laying out trays evenly across the working width, before making a pass spreading fertiliser over the trays. The material in each tray is then put into small tubes so that the balance of spread can be assessed. It is important that the trays are level and that there is no wind which will affect the results. This is important to ensure accurate application and should be carried out at least once a season for each fertiliser type.
When using a wagtail/pendulum type spreader with a typical working width in the region of 10- 12m, it is reasonably easy to maintain an accurate bout width by eye.
Once working with wider bout widths or spreading in a recently cut field, it becomes much more difficult to maintain accuracy. Over the course of the past few years, there has been a large uptake in entry level GPS. These systems can help to cut out overlapping and reduce fertiliser usage.