Remarkable results from Teagasc research carried out at Solohead, Co Tipperary and Moorepark, Co Cork indicate that the frequency fertiliser spreading on intensive dairy farms can be reduced by 90%, without losing grass production.
The researchers harvested grass every four weeks from March to November.
They found the difference in grass yield was insignificant, whether nitrogen was applied after every grazing, applied twice per month, or once per month.
During 2004, nitrogen application after each grazing delivered 4% more grass than monthly applications.
This slight yield advantage occurred mainly during May, June and July.
In a similar trial in 2005, there was no difference in grass yield between the two systems, and applying nitrogen only once per month proved slightly superior in the spring.
However, the blanket application of nitrogen once a month wins hands down, in terms of labour input.
It requires as few as eight fertiliser spreadings, whereas fertiliser after each grazing may have to be applied as many as 85 times per year.
The Teagasc research team comprised James Humphreys, Kevin McNamara, and Aidan Lawless.