Agronomy Advice

Heavier fertiliser spreads further

By: Mark Tucker

Some fertilisers consistently spread further and more accurately than others. A heavier and larger fertiliser granule will spread further because the spreader can put more energy into it. The granule needs to be strong enough to withstand this without shattering. So, what are the properties in a fertiliser that ensure it spreads accurately over wide bout widths?

Farmer opening up a  yara fertiliser bag
Farmer opening up a  yara fertiliser bag
Heavier fertiliser granules will spread further and more evenly

The three properties of fertiliser that influence how far it can be spread are weight, size and hardness. In other words bulk density, particle size and crush strength.

Bulk density is the weight of a given volume of fertiliser and measures how heavy a fertiliser is. This is determined by the manufacturing process and the chemical nature of the fertiliser – urea is always lighter than ammonium nitrate. YaraBela Extran has a bulk density of 1.0 kg/litre, compared to Granular urea which only has a bulk density of only 0.7 kg/litre. 

Particle size is the measure of how large the individual particles are. This is influenced by the physical structure of the particles and depends mainly on the manufacturing process so will vary from factory to factory. The YaraBela range of ammonium nitrate based fertilisers are all granular products with particle sizes ranging from 3.4 to 3.6mm average whereas ammonium nitrate prills will typically have an average particle size of only 2.4mm. Particle size distribution is also important as it affects both the evenness of spreading and the maximum spreading width. 

Crush strength or particle hardness depends on the chemical composition of the fertiliser and on the manufacturing process. If a particle is not hard enough it will shatter when it is hit by the spreader vanes and the harder they can hit it the further it will go. A cloud of dust following a fertiliser spreader is a sure sign the spread pattern will not be very accurate. YaraBela Extran has a particle strength of 9.2 kg which is more than double that of most prills or urea. 

Read more on physical properties of fertiliser

So much for the theory, what about in practice? 

At a recent demonstration YaraBela Extran and Axan were both spread accurately to over 40m and indeed some spreader manufacturers give recommended settings for YaraBela Extran up to 54m. 

When spreading over these wider bout widths it is important to maintain accuracy which requires a uniform fertiliser. A heavier and larger granule will be less affected by wind so will spread more accurately in marginal conditions. 

Just as important the fertiliser spreader must be well maintained and accurately calibrated. This can only be checked by conducting a tray test in the field. Spreader manufacturers settings are a good starting point but these must always be checked in the field with each fertiliser, this is especially important for wider bout widths of 36m and more.

Find more advice on spreading fertiliser

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