Dr. Frank O'Mara:

Briefly, the main form of nitrogen fertiliser used in this country is calcium ammonium nitrate, CAN, which is associated with emissions of nitrous oxide, a greenhouse gas. The main alternative fertiliser type available and which is used in many other countries is urea. We use some of it in Ireland, but much more of CAN than urea. Urea is associated with emissions of ammonia. Protected urea is the one that hits the sweet spot in that it is a urea that does not produce ammonia.

It is low in both nitrous oxide and ammonia, which is why it is the fertiliser type we would advocate as the main nitrogen source on our grassland farms.