According to Teagasc, there is increasing interest among tillage farmers in switching from calcium ammonium nitrate (CAN) to protected urea this season.
Based on current fertiliser prices, there are significant financial benefits to using protected urea.
Currently, protected urea costs 30% less than CAN. The environmental benefits of protected urea are well proven with lower nitrous oxide (N₂O) emissions than CAN, as well as a reduction in ammonia emissions when compared to straight urea.
Moreover, the use of urea results in lower levels of nitrate leaching compared to CAN.
CAN vs protected urea
The big advantage of protected urea is that farmers can use it from late January to early September.
It will work as effectively as urea in spring in damp conditions. Due to the inclusion of the urease inhibitor, it releases nitrogen (N) slower and more effectively than CAN in the summer.
But the core question that many growers are asking is – what effect will switching from CAN to protected urea have on grain yield?
This specific issue was addressed as part of a three-year trial, carried out at a free-draining site in Co. Wexford.
The work was conducted over three seasons – 2013, 2014 and 2015.
Three N sources were compared, CAN, urea, protected urea (urea plus NBPT) and an unfertilised control.
A total of 150kg/ha N was applied in two splits: 30kg/ha at sowing and 120kg/ha at mid-tillering.
The results showed that grain yield was similar for all fertilisers but on average protected urea yielded 0.3t/ha more than CAN.
Application
From an application perspective, urea is less dense than CAN, making it more difficult to spread evenly at wide bout widths.
Where protected urea is being applied, trial work indicates that it is safe to apply to fields that have been limed recently.
It is, therefore, crucial that the fertiliser spreader is set up correctly, in line with manufacturer’s recommendations for the specific product being used.
Trays should always be used to check the spread pattern in the field.
Protected urea can be used with a number of blended fertilisers.
According to Teagasc, straight phosphorus (P) and potash (K) fertilisers or blends such as 0-7-30 or 0-10-20 are needed to achieve a 100% switch relative to a conventional compound.
Alternatively, farmers would need to use an application or two of high P/K products such as 18-6-12 plus sulphur (S), based on nutrient need.
In turn, this opens the opportunity for more straight N slots where protected urea, with or without S, is a good fit.