Fertiliser quality – and knowing what characteristics to look out for when calibrating – is the subject of the latest video produced by the Fertiliser Association of Ireland.
The sixth video in the association’s video series on the Efficient Use of Fertilisers looks at the importance of fertiliser quality characteristics when calibrating and achieving an even application across the spread width.
According to the association fertiliser spreading and machinery has evolved over the past decade with wider spread widths.
As a result a major emphasis has to be given to fertiliser quality and characteristics as this will determine spread width and evenness of application.
What are the most important fertiliser characteristics to know?
- Fertiliser Type
- Bulk Density
- Granule Strength & Hardiness
- Granule Size & Shape
The association provides info on each of these characteristics below.
Fertiliser type
Fertiliser can come in the forms of granular, prilled or small prilled – the latter of which is cheaper to produce but is light in density and has limited spreading capabilities.
When setting the fertiliser spreader rate this is one of the first characteristics required when using calibration charts or phone apps.
This is a very important factor especially on spread widths of greater than 18m.
Bulk density
Granule density affects the ballistic potential of the granule and has a direct impact on the spread width of a fertiliser.
A heavier granule will travel further than a light granule. Urea has a 25% lower bulk density than CAN (0.7-0.75 kg/L vs 1.03kg/L) – and this needs to be considered when setting the fertiliser spreader.
For example this is why it is important to always ask what is the nitrogen source of a particular product (check label) – is as this will determine your spreading limitations.
Blending fertilisers of similar density will be important to prevent segregation / stripping of the fertiliser.
On larger bout widths (over 24m) consider a CCF (complex compound fertiliser) type fertiliser to ensure even application across the full spread width.
Granule size and shape
Particle size and size distribution will have a large impact on the fertiliser spread width and uniformity. Generally larger particles will throw further, the fertiliser association notes.
Farmers should aim for the majority of fertiliser granules (80%) in the 2-4mm size range will allow a good even spread to be achieved, but larger diameters (3 – 4.5mm) will make it easier achieve wider spread widths.
For fertiliser blends the component parts should ideally have similar size distributions.
A fertiliser sieve box is a quick test that can be carried out to determine granule size and some fertiliser spreader manufacturers require this information when calibrating the spreader.
Fertiliser granule shape will vary among fertilisers. For example nitrogen (CAN, urea and phosphorus) tend to be round in shape whereas potassium tends to be angular.
Round granules tends to roll along the vanes while angular granules tend to slide along the vales.
Strength and hardness
Granule hardness refers to the force that can be applied before the granule breaks, the association says.
All fertiliser granules, whether it be as a straight or in a blend, have to be fit for purpose to make it to its intended landing site.
A number of tests can be carried out to determine the granules’ strength such as a granule crushing strength.
This is a measurement of the pressure a granule can withstand before crushing; this is important as the granule has to withstand the sheer force when the disc hits it to send it to its location.
Granule hardness will influence both the spread width and the disc speed where softer fertilisers may shatter on the disc resulting in granule breakage.
One can check fertiliser granule hardness with a hardness indicator.
Fertiliser spreader calibration and tray testing
Fertiliser blenders/manufacturers regularly send product samples to the fertiliser spreader manufacturer in order to get guide settings.
It is the responsibility of the farmer/operator to:
- Ensure that the spreader is calibrated correctly as per spreader manufacturer settings before fertiliser application.
- Carry out a tray test to ensure an even spread pattern is achieved.
- Consider factors such as wind conditions and field topography as they could have an impact on spreading capabilities and these factors should be taken into consideration before application.
