Early Nitrogen application guidelines

Wednesday 22.01.2020 , News

After quite a wet autumn and winter there are many fields around the country that will benefit from the application of Nitrogen (N).

With the closed period for spreading both chemical and organic fertilisers coming to an end, it is now worth putting a bit of thought into having a planned approach to your spring fertiliser decisions.

The response to early N application is dependent on the sward content, soil temperature, soil fertility and soil type. Using spring N is beneficial to grass production, however incorrect application or poor timing of application is wasteful, costly and can have negative environmental effects.

Table 1. Closed Periods for the application of organic & chemical fertiliser



Chemical Fertiliser

Organic Fertiliser

Farm Yard Manure


Carlow, Cork, Dublin, Kildare, Kilkenny, Laois, Offaly, Tipperary, Waterford, Wexford, Wicklow

15 Sept – 12 Jan

15 Oct – 12 Jan

1 Nov – 12 Jan


Clare, Galway, Kerry, Limerick, Longford, Louth, Mayo, Meath, Roscommon, Sligo, Westmeath

15 Sept – 15 Jan

15 Oct – 15 Jan

1 Nov – 15 Jan


Donegal, Leitrim, Cavan, Monaghan


15 Sept – 31 Jan

15 Oct – 31 Jan

1 Nov –31 Jan


Nitrogen and organic fertiliser should only be spread after the above closing dates have passed in the relevant county (Table 1). Best practice is to avoid spreading in saturated fields or where the soil temperature is below 6°C and do not apply fertiliser if heavy rain is forecast in the next 2 days or so.

For early N application, choose fields containing a high percentage of perennial ryegrass or younger swards, as they will give the greatest response, as will drier, free draining fields. Spread N in the form of protected urea and target fields with higher covers on the farm, as they will be grazed sooner. On fields with lower grass covers or low P and K levels using slurry will be more beneficial.

Best practice guidelines advise spreading slurry on one third of the grazing platform with the lowest covers at approximate 2500 gallons/acre. The remaining two thirds of the grazing platform can be spread with 23 units/acre of protected urea (NBPT) in January/February; depending on suitable conditions. Do not spread slurry and fertiliser N on the same fields in the first round of application. A further 46 units/acre of N in the form of protected urea can be spread on the entire grazing platform between March and early April. Do not apply more than 90 kg N/ha before early April.

Setting out a fertiliser plan is always useful and now is a good time to do so. Now is also a good time to calibrate your fertiliser spreader before you get too busy with other jobs on the farm.