Fertilizer Association of Ireland - Frequently Asked Questions

Q.7 Does frost damage recently applied fertilizers?

A. Frost does no damage to recently applied fertilizer. Growth conditions will obviously be very poor during frosty weather and there will be little or no uptake of fertilizer but the fertilizer nutrients will retain their potency for when growth conditions improve. Fertilizer should not be applied to frozen fields due to the risk of run off losses when the thaw sets in.

Q.8 When is the best time of the year to apply phosphorous (P) and potassium (k) to grassland.

A. This depends on soil fertility and soil type. On peaty soils it is best to apply P and K during the growing season because peat has a poor capacity to retain fertilizer. Potash shouldn’t be applied to sandy soils during late Autumn/Winter as it is readily leached from sandy soils.

On non sandy mineral soils where soil fertility is poor (Index 1) it is best to apply a fairly large application of P and K in the Autumn in order to promote tillering and root development. As soil fertility improves (index 2 or better) the timing of P and K becomes less critical but there are time and labour advantages to applying P and K with nitrogen during the growing season. Risk of losses should be less with smaller more frequent applications of P and K during the growing season compared to a large single application out of season.

Q.9 When is the best time of the year to apply sulphur to grassland and how much should I apply?

A. From May onwards is the best time. 15 units of sulphur per acre is recommended for second cut silage. In very deficient areas apply 15 units of sulphur for first cut as well. 15 to 20 units per acre should be applied to grazing fields preferably in a number of applications.