Grass is crying out for a nitrogen boost

According to Teagasc dairy specialist John Maher, grass availability is pretty good on dairy farms across Ireland at the present time.

“Most of this growth took place during the month of December. However, many farmers are telling me that swards are now taking on a yellow tinge,” he said.

“This tells me that they are crying out for a nitrogen boost. This can be in the form of slurry or a chemical fertiliser.

Modern grass varieties have tremendous potential to grow during the early spring months.

Maher made the comments while taking part in a recent Teagasc Dairy Edge podcast.

“The present cold and wet conditions are combining to stifle grass growth right now. This is because the microbes in the soil are not active enough to mineralise the nitrogen that can be absorbed by the grass plants making up a sward,” Maher added.

“But nitrogen, from either slurry or a chemical fertiliser, will act to boost grass growth soon, as soil temperatures increase.”


Maher went on to confirm that getting dairy cows, or any other ruminant animal, out to early grass means that they are spreading their own slurry. In turn, this will result in lower greenhouse gas (GHG) and ammonia emission levels.

“Grass covers on dairy farms should be in the region of 850kg of DM/ha at this time of the year. This figure is highly dependent on the closing date achieved for paddocks the previous autumn,” he said.

“Daily grass growth rates over the past months have been in the region of 4kg to 5kg of DM/ha. These figures are very much within the expected range.”

Slurry or protected urea

Maher confirmed that milk producers wanting to achieve early spring grass growth should target paddocks with either slurry or protected urea – but not both.

“Slurry should be spread on paddocks with the lowest grass covers. These will benefit from the nitrogen [N] applied but also the added P [phosphorus] and K [potassium].

According to the Teagasc specialist, a slurry application of 2,500 gallons/ac will deliver the required 23 to 24 units of nitrogen (N) to grass swards.

“Paddocks receiving protected urea should receive half a bag per acre. Spreading should be undertaken once frost has lifted and the weather is forecast to be mild and dry.

“Rain subsequent to application will lead to run-off,” according to Maher.

Maher stressed the benefits of spreading slurry using a trailing shoe or dribble bar.

“Lower emission spreading systems [LESS] make the nitrogen available in ways that are easier to take up by the grass. In addition, there is less coating of swards while ammonia volatilisation levels are also reduced,” he concluded.