The physical quality of protected urea is extremely important in order to be able to spread it evenly, Dermot Forristal from Teagasc has said.

Speaking on last Friday’s Teagasc Signpost webinar, Forristal said it’s important to remember that urea is physically different to nitrogen-based fertilisers, and because of that it spreads differently.

“We still can spread urea evenly provided that the physical quality is OK,” Forristal said. “The factors that impact on evenness are the physical quality itself, the fertiliser machine design, the machine setting and field conditions like wind,” he said.

Characteristics of good protected urea include the granule size – this will affect the distance the fertiliser will throw on a broadcast spreader.

Density will also affect the distance of travel, but also its susceptibility to wind.

The shape of the granule will affect the distance, but also the trajectory.

However, the strength of the granule is most important – weak granules will break during handling and spreading, according to Forristal, who said it’s “impossible to spread dust”.

“The one thing that’s different with urea is that it has lower bulk density, so typically it’s about 0.8kg/l versus other fertiliser products being about 1kg/l to 1.3kg/l,” he said. “You could compare this density effect to be something like comparing a table tennis ball with a golf ball. They both might be the same size, but you’re going to throw a golf ball much further with much more accuracy than you would a table tennis ball, because of the difference in the density.”

Labelling

Forristal said that there should be an agreed particle strength that’s deemed to be acceptable or not.

He also argued that the fertiliser physical quality should be on the bags that farmers are buying – including the particle size distribution, density, strength and the date and batch number.

“This would bring a whole awareness of physical quality as it has a value, as does good spreading and we need to be conscious of that,” he said.