Agronomy Advice
February 22, 2024

How do I Maximise Spring Grass?

By: Philip Cosgrave

Grass is at its highest value in Spring, so a lot of research has gone into how we maximise grass growth at this crucial time.

Farmer and Agronomist in a field with dairy cows

The latest research out of Teagasc Moorepark tested three different application rates of spring nitrogen to see the impact it had on grass growth.

Tested Applications

The trial looked into how different splits of nitrogen between two timed applications impacted grass growth.

Fertiliser was spread on the same days in each instance: 3rd February and 19th March. They tested three different total amounts of spread nitrogen: 30, 60 and 90 kg N/ha. Within each total, they then varied how much was spread on each date, with ratios of 0:100, 50:50 and 33:66.

What measures did Teagasc look at?

There are lots of barometers for success, but Tegasc were looking at two specific measures:
• Spring herbage production (kg DM/ha)
• Nitrogen efficiency (Nitrogen response per kg of nitrogen spread)

Looking at these two measures together allows us to take a balanced approach to our nitrogen choices and application strategies. We want to find that sweet spot between nitrogen efficiency and grass yield.

What were the results?

If we look at just the total amount of spring herbage production, the highest amount was 3,026 kg DM/ha which was delivered with the 90kg N/ha. Here’s the results at all nitrogen rates:

Nitrogen Totals Spring Herbage Production
90kg N/ha 3,026 kg DM/ha
60kg N/ha 2,753 kg DM/ha
30kg N/ha

2,308 kg DM/ha


But when we look at the nitrogen response per kg of nitrogen applied, we get a different story with the 30kg N/ha delivering the best efficiency:

Nitrogen Totals Nitrogen response 
90kg N/ha 15.7 kg/DM/ha/kg N
60kg N/ha 18.2 kg/DM/ha/kg N
30kg N/ha 21 kg/DM/ha/kg N


However, it is worth pointing out that despite these differences, all three results delivered a greater response rate than the previously reported response figures of 10 - 13 kg DM/kg N, and greater than the required economic break even point.

How did the application strategy affect these results?

No matter the total amount of nitrogen spread, delivering it all in March at the 0:100 ratio, resulted in a reduced spring herbage production of 200kg DM/ha when compared to the other application ratios of 50:50 and 33:66.

The best N response was for the 33:66 ratio delivering 27.3 kg DM/kg N where the 50:50 approach returned 21.1kg DM/kg N.

It’s clear from these results that a single application of high levels of nitrogen in spring results in an oversupply of available nitrogen for the plant to utilise. This reduces nitrogen efficiency as it’s lost to the surrounding environment and therefore the impact on grass growth is reduced.

What's Yara recommendation ?

To maximise nitrogen efficiency and deliver the highest return on grass growth in the spring, we would recommend, on intensively stocked grazing platforms, that you spread 20kg N/ha for the first application in February, followed by 40kg N/ha in March. We believe this will help boost spring grass growth and maximise the proportion of grass in the diet of grazing livestock.

Feed your grass with Yara’s Booster range of fertilisers:

  • Contains Selenium for healthier livestock
  • Sodium enrichment encourages longer grazing times 
  • Addtional sulphur increases yield by 10-15% in first and second cut 
  • True unifrom fertiliser - every granule contains every nutrient 
  • No nutrient segregation - achieves an even spread