The role of NBPT protected urea
Colm Kelly, Climate Action & Sustainability Advisor, Teagasc Galway/Clare, looks at the role NBPT protected urea will play in grass growth throughout the summer, its significant positive contribution to greenhouse gas and ammonia emission reductions, and how it achieves cost reductions at farm level
What is NBPT protected urea?
It is a urea nitrogen fertiliser with a urease inhibitor (NBPT) added, which reduces the ammonia based nitrogen losses straight urea is vulnerable to. A key advantage is that it is a more stable product upon application than straight urea, which allows it to be used to substitute CAN based fertilisers throughout the summer.
How does it compare to CAN price wise?
A big selling point is that it works out at lower cost per kg of N purchased. So although it may cost more per tonne than CAN, it has more N in each tonne. As a rule of thumb, there will be approximately the same amount of N in 3 tonnes of (46%) NBPT protected urea as 5 tonnes of CAN. A cost estimate based on reported February ’24 figures for the 3 tonnes of NBPT protected urea will be €1,650 while 5 tonnes of CAN will cost approximately €1,940 for the same amount of actual N.
Why is NBPT protected urea being promoted so heavily for emissions reduction?
On the GHG emissions side, NBPT protected urea is calculated to have 71% lower Nitrous Oxide emissions than CAN, which in Galway/Clare is translating to a 2-8% reduction in overall farm emissions estimates with full substitution. It has a key role to play nationally in terms of being as easy as it currently gets for farm GHG emission reductions. There is also an Ammonia reduction target for agriculture and, compared to straight urea, the NBPT protected urea significantly reduces the calculated Ammonia emissions by 78%.
Can I get it in compound form?
Previously NBPT protected urea could not be bought with Phosphorus (P), as it made the inhibitor ineffective which could have lead the protected urea to effectively behave the same as straight urea. It could be purchased with Potassium (K) and Sulphur (S). A change this year is that ‘glazed’ compounds have entered the market with NBPT protected urea as the N source. This glazed formulation is allowing the inclusion of P, which will be a positive development for the majority who use compound fertilisers. It is important to note also where ‘glazed’ NBPT products may not be available that standard compounds such as 18-6-12 and 10-10-20 are showing lower emissions than other higher N compound types while tending to be better value.
Any issues with application?
Like with any fertiliser, having the spreader calibrated correctly for the type of fertiliser used is important along with bout width. Calibration instructions may have come with the machine or for newer models may be accessible on an app. The maintenance of the machine is also important, with wear damage over time effecting performance regardless of fertiliser spread. Due to the higher N content, the application rate will be lower than CAN. The fertiliser density is also lower for urea fertiliser versus CAN, which may make it more challenging to spread at wider bout widths. Larger and stronger granules are an indicator of fertiliser quality. NBPT protected urea does have the potential to draw more moisture, which can cause issues if the fertiliser spreader is not washed out after use.
Will NBPT protected urea effect N availability to the silage crop?
Compared to straight urea, the inhibitor moderates the rate that the urea N converts to ammonium, which occurs as soon as the granule begins to melt. The inhibitor slows the conversion rate to occurring over a few days rather than a few hours. This reduces emissions and does not hinder the response of a grass crop, as N uptake is required for longer than the first hours after application. Trial comparisons over a number of years show no significant yield or N recovery differences between CAN and NBPT protected urea.
More information on the use of NBPT protected urea is available on the Signpost Programme webpage.