Farmers are coming under increased pressure to reduce the environmental impact on water quality and ammonia emissions. In an effort to reduce these emissions, many farmers have included protected urea in their nutrient management plans.

In simple terms, protected urea is regular urea, but it’s coated with a urease inhibitor in order to reduce ammonia losses. The benefit of protected urea is that it can be spread throughout the summer period when temperatures are higher, where calcium ammonium nitrate (CAN) would traditionally be used.

Along with being able to spread protected urea in the summer months, it has an ability to reduce ammonia losses by up to 70% due to the urease inhibitor.

The inhibitor is a protective layer around the fertiliser, it is an enzyme which slows down the conversion of urea to ammonium. Slowing this reaction reduces a high influx of ammonium available to the soil at one time, therefore, reducing leaching and volatilisation.

In the past five years or so, there has been a good uptake of farmers who have either changed from using CAN to protected urea throughout the summer months, or have changed over to using all protected urea as their chemical N supply.

The Department of Agriculture released figures showing the percentage of urea sold in Ireland in 2022 containing an inhibitor was 36%.

The reason that many farms haven’t yet made the switch to protected urea has been down to price and the inability to include compound fertilisers with protected urea.

Some good news is that there are new compound fertiliser products coming on the market which also have a urease inhibitor. One downside was that phosphorus (P) couldn’t be included in any protected urea products due to the acidity of phosphorus. The Department of Agriculture has released a list of products with active ingredients that can be marketed in Ireland as urease inhibitors, as per legislation. This includes NBPT, 2-NPT, NBPT+NPPT and Maleic Itaconic CoPolymer. The below products are recognised within this list.

Glaze Extend

In past trials, the acidity of P was breaking down the urease inhibitor, making the urea unprotected again.

A New Zealand-based company, Glaze Coatings, has brought its NBPT product to the Irish market for 2024. The product is a suspension of water and pH buffers.

Trials in New Zealand were tested at both 500 and 300 ppm (parts per million). In the Grassland Agro product, it is being used at a rate of 650 ppm, says head of sustainability at Grassland Agro, John O’Loughlin.

O’Loughlin says trials have shown that the new protected urea compound fertilisers can reduce ammonia emissions by up to 50% on their 24:2.5:10+2.5% S and 27:2.5:5+2.5% S products, when compared with their unprotected counterpart. Trials from the 18:6:12+S product showed a 13% reduction in emissions.

These advancements in NBPT technology should lead to a greater uptake in the number of farmers using protected urea on farms. Having NBPT blended with Di-ammonium Phosphate (DAP) is an innovation which could have a big impact on soil fertility across the country.

Tests taken out by Grassland Agro also showed the shelf life of Glaze Extend products was a minimum of 10 months, with no breakdown of the urease inhibitor, which was a concern in the past.

O’Loughlin also said that the Glaze Extend products have been approved and qualified by most of the co-ops. The Glaze Extend products will be eligible for sustainability programmes in which spreading protected urea is one of the criteria.

He also said Glaze Extend will be readily available on the market for 2024 at a guided price of approximately €10/t less than CAN-based alternatives.

Grassland Agro does not have exclusivity for NBPT products blended with DAP on the Irish market. It is believed that other Irish fertiliser companies will have similar compound products on the market for 2024, but are waiting for finalisation.

Nutrisphere N

Taking a different approach to the market in 2024 is Goulding, with a new range of protected urea products that include phosphorus. This uses a maleic itaconic copolymer, which is a non-chemical way of protecting urea.

The maleic itaconic copolymer shields nitrogen on a molecular level by inhibiting enzymes and keeping more nitrogen in the immobile ammonium form for a longer period of time. It does this by sequestering nickel, which deactivates the urease enzyme.

According to Goulding’s trial data, there is less leaching with a 21% reduction, less emissions with an 85% ammonia reduction and a 61% nitrous oxide reduction. This would mean up to four times more usable nitrogen as ammonium compared to untreated urea fertiliser.

Nutrisphere has been now recognised by the Department of Agriculture as a nitrogen stabilising product, as it limits the loss of volatilisation. There is also a minimum shelf life of 12 months on any fertiliser within this range.