Maximise nitrogen use efficiency by reseeding grassland

Monday 13.06.2022 , News

Nitrogen fertiliser costs have soared in recent years, stretching input budgets. With other costs rising, too, increasing grass production to secure more homegrown forage is crucial.

Germinal grass and forage expert Ben Wixey suggests how to maximise nitrogen use efficiency on your grassland this season. 

Improve grass production by reseeding older pasture

Short-term improvements in production can be seen from overseeding grassland, and with budgets tight, gaining an extra year from an older pasture is tempting.

However, Ben advises farmers to think carefully about the return on investment (ROI) from a reseed versus the cost of stimulating an older pasture to provide enough forage.

“Nitrogen use isn’t as effective in older swards, so not only are you wasting what you have, you may even need to apply more to keep up production levels. For most farmers, this is just not an option this year.

“Nitrogen use efficiency is best in newer swards, so if you’re keen to go easy on what you use, I suggest focusing on establishing new grass swards – especially if they are for cutting.”

Grassland production: New leys versus old leys

Sward type


t DM/ha


(MJ/kg DM)

ME per ha

Lost milk production L/ha

Lost meat production kg LW/ha

New ley (95% PRG)






Old ley (70% PRG)




9,000 L

540 kg

Permanent pasture (50% PRG)




15,200 L

916 kg

Source: AHDB

Modern seed genetics improve nitrogen use efficiency

To see the best value for money from agricultural grass seed, the Recommended Grass and Clover List (RGCL) is the place to start. The varieties on the list are independently tested and assessed for their performance in typical British conditions.

Only one in 20 varieties tested will make the final list, so you can be confident you’re picking a variety which will give you the best ROI.

You can also review which varieties are best for silage, grazing, disease resistance or other agronomic characteristics. Germinal varieties continually top the RGCL list – reflecting our commitment to only producing the top varieties.

“The varieties on the RGCL represent decades of seed genetic research and can vastly improve your grass quality and persistence. It’s something to consider when you’re deciding between whether to reseed or rejuvenate.

“You won’t be replacing the old sward with the same grass seeds. You’ll have an improved seed which delivers better nitrogen use efficiency – and drives production via genetics, not applied nitrogen.”

Assess your sward performance

To help you decide when and where to reseed, assess each sward thoroughly during your weekly farm walks, looking at individual fields as well as overall farm performance. Swards which need targeting often have:

  • A high level of weeds such as docks or thistles
  • An increased proportion of unproductive grass
  • Reduced silage production
  • Slow recovery in rotations
  • Poor nitrogen use response
  • Damaged ground or poaching
  • A drop in milk yield seen when grazed

For more videos and guides on reseeding, visit our Germinal Knowledge Hub.

This article is the first in our series on reseeding. Next time, we will look at the techniques behind sowing correctly. If you have any queries, please ask our grass and forage seed experts.