How early nitrogen application can improve grassland yield

Nitrogen (N) is the major nutrient required by grass and is often strategically used to increase grassland yields. Teagasc research has shown that every 1kg of N applied in early spring produces in the region of 10kg dry matter (DM) of grass.

The key to achieving high yields is to apply the correct amount of N, from the right source at the right time.

Take a look at Target Fertiliser’s Q&A below:

What application rate of N should I use?

The general rule of thumb is to apply 30kg/ha or 24 units of N on the first application which equates to a half bag of urea or one bag of calcium ammonium nitrate (CAN) +/- sulphur (S).

It is important that your N application rate is linked to your stocking rate; the amount and timing of your N application should be carefully considered to meet the current Nitrates Regulations; therefore, it is recommended to discuss your N application plan with your local advisor.

What sources of N should I use?

There are two sources of N available for application: organic; or chemical.

Organic N is usually cattle slurry and while the opening dates are the same as with chemical fertilisers, the level of N within cattle slurry is low. Unless you are under pressure to spread slurry, it is recommended to retain it for application on silage ground, as it has a nutrient balance more suited to a harvested crop. Every 1,000 gallons of cattle slurry of 7% DM applied per acre is the equivalent to 5 N – 5 phosphorus (P) – 30 potassium (K) when using a splash plate. The level of N will increase by three units when using Low Emission Slurry Spreading (LESS) i.e., a dribble bar or trailing shoe;
CAN (27% N) is in the form of ammonium nitrate and is immediately available for plant growth. Both forms are available for plant utilisation but normally, the ammonium fraction is changed to nitrate for plant uptake by soil micro-organisms;
Urea is the product of choice for early grass growth once soils have an adequate pH of 6.3 for maximum N use efficiency. Urea undergoes hydrolysis after its incorporation within three-to-seven days. Urea is then converted to ammonium and this must be nitrified to convert to nitrate before it can be utilised by the plant. The table below shows the conversion time of ammonium to nitrate depending on soil temperature.

When is the right time for me to use early N?

The “right” time to apply early N is dependent on your requirement for grass and your intended grazing start date. As the response time for N following application is approximately three weeks, it is recommended to apply N three weeks before your intended grazing start date.

Grass growth initiates once soil temperatures reach 5-6º. The opportunity to apply fertiliser will however depend on ground conditions and the forecasted weather; therefore, ground must be firm and not subject to wheel damage causing ruts and the risk of compaction.

It is not recommended to apply N during or prior to expected high rainfall events due to the risk of de-nitrification or run-off.

It is also best to avoid application during a period of severe frost cover due to the risk of grass burning at the tyre tracks. It is best practice to apply urea just before 4–5mm of rain is forecast within the next 12 hours to ensure good soil incorporation.

The chemical fertiliser application period reopens on specific dates in the following regions:

January 13 in Zone A – Carlow; Cork; Dublin; Kildare; Kilkenny; Laois; Offaly; Tipperary; Waterford; Wexford; Wicklow;
January 16 in Zone B – Clare; Galway; Kerry; Limerick; Longford; Louth; Mayo; Meath; Roscommon; Sligo; Westmeath;
February 1 in Zone C – Donegal; Leitrim; Cavan; Monaghan.

What protected urea products are available?

Target Fertilisers offers a range of protected urea products. The Target Max fertiliser range is protected by Limus®, a unique urease inhibitor that slows down the conversion of urea to ammonium and thus reduce ammonia losses by up to 98% whilst protecting the environment.

There are three products available from the Target Max range to suit different soil fertility requirements.