Practical steps from Teagasc to minimise ammonia loss in urea application
“The biggest concern with urea is the possible loss of ammonia while it is converting to ammonium (after which it is fixed to the soil and is less prone to loss by volatilisation to the air),” Teagasc says.
Teagasc says that at 90c/kg of nitrogen (N), urea is a much cheaper source compared to CAN at 120c/kg and that it is also less prone to leaching than CAN especially for earlier N applications.
Teagasc advises to apply urea shortly before moderate rainfall (less than eight hours) or rainfall that is adequate to wash urea into the soil (five to 10mm).
It says that care should be taken that rainfall volume will likely infiltrate the soil rather than generate run-off/overland flow as this may carry N with it. It says that periods with small rainfall volumes followed by drying spells in the days after urea application can promote N losses.
Teagasc is advising farmers to avoid recently limed areas and to also avoid high pH soils, in particular soils that have a greater pH than 7-7.5.
“Apply urea in smaller applications, e.g. 40kg/ha loses a lower percentage of N applied than 80kg/ha,” Teagasc says.
It says that “during drier or sunny periods that may promote volatilisation, use urea with an effective urease inhibitor as it delays urea hydrolysis for a short period, allowing the urea granule to disperse by diffusion or be washed into the soil by rainfall”.
Teagasc also reminds farmers to be prepared for being busy that March is a high accident month when, on average, the risk of a fatal accident increases by 40%.
Teagasc says that this is associated with high workload. It also tells farmers to prevent accidents by being well organised, removing farm hazards as they arise and adopting safe procedures, particularly avoiding rushing.