Why use Protected Urea in 2023?
Protected urea (protected with a urease inhibitor) is cheaper than CAN and straight urea. Protected urea is cheaper than CAN on a cost per kg of nitrogen basis, and, while it may appear slightly more expensive than straight urea, it will give the same “effective N” for the plant as urea, at a 12.0% lower spreading rate.
Assuming a rate of 27 kg of N per acre spread as protected urea or 27 kg of N per acre spread as CAN in March 2023. Looking at this purely on a cost per tonne basis, the CAN is €150 per tonne cheaper. But, CAN has just 27% nitrogen in it and the protected urea used in this example has 46% nitrogen in it. The total cost of buying the 5 tonnes of CAN, needed to spread 27kg / acre on 50 acres is €4,250. However, the total cost of buying the 3 tonnes of protected urea, needed to spread 27kg / acre on 50 acres is €3,000. A saving of €1,250 or a saving of €25 / per acre.
Table 1. Relative cost of an application of N using different fertiliser types
|CAN (27% N)||
NBPT Protected Urea (46% N)
|€ / tonne||€850||€1,000|
To supply 1,350 kg of nitrogen or
an application of 27 kg / ac on 50 acres
|5 tonnes||3 tonnes|
|Total cost €||€4,250||€3,000|
|Cost per acre||€85||€60|
At these prices, the farmer will get better value for money by using protected urea. Using current fertiliser prices, shows that the extra cost of the urease inhibitor more than covers its cost relative to straight urea, with a return of 2.5:1. The value of retaining N that had previously been lost as ammonia has increased dramatically in line with the increased fertiliser cost. Also, in a situation where N application rate is limited, it makes sense to use less of a more effective product.
The quantity of grass grown by using CAN, protected urea and urea was similar across all fertiliser types in short-term Teagasc trials. However, in a long-term trial at Johnstown Castle, the grass grown by the fertiliser (i.e. net of the zero N control) for protected urea was greater than standard urea in 6 out of 7 years, 2018 being the exception due to drought when water was the limiting factor not nitrogen. Protected urea grew 13% more grass on average compared to standard urea. The additional yield is similar in magnitude to the extra effective N level delivered to the plant by protected urea over standard urea. CAN yielded 9% more than standard urea.
By switching to 100% protected urea on dairy farms, total farm emissions have the potential to be reduced by 7-8% at a spreading rate of between 200 to 250 kg N / ha. The equivalent savings on total emissions on suckler farms is 1-2%, at a spreading rate of 60 to 80 kg N / ha. Straight P and K fertilisers or blends such as 0-7-30 or 0-10-20 would be needed to achieve a 100% switch or alternatively use of a split or two of high P-K products such as 18-6-12 +S based on nutrient need opens the opportunity for more straight N slots where protected urea +/-S is a good fit.
Table 2. Benefits of using different fertiliser types
|Highest grass growth||
|Lowest ammonia emissions||√||√|
|Lowest GHG emissions||√||√|
|Lowest GHG and ammonia emissions||√|
|Lowest cost € / kg of nitrogen||√|
|Lowest cost € / kg of effective N||√|