Targeted approach needed on nitrogen
Adapt fertiliser planning to weather and grazing changes
Published 15/02/2011 | 12:05
Soil temperatures need to be at least 5C before nitrogen application can boost spring grass growth. However, the date that soil temperatures reach this critical point varies from year to year.
In some years, 1kg of nitrogen (N) has the ability to grow 10-15kg of grass dry matter during February, while in other years there can be little or no grass growth response to it because of prolonged cold weather going into March.
This year would be classed as one of the later years and figures show soil temperatures above 5C only in the past week.
Until recently, the recommendation has been to apply nitrogen fertiliser six weeks before your expected turnout date.
However, as farmers move towards turning out smaller groups of cattle at intervals and starting with an earlier turnout date, this recommendation no longer applies and a more targeted approach is needed.
Teagasc experts Michael O'Donovan, Emer Kennedy and Pearse Kelly outlined some guidelines for nitrogen application on spring grass.
They advise that paddocks or fields that have heavy covers of grass -- more than 10cm -- built up on them since the previous autumn and over the winter should be grazed first before applying N.