The Need to Re-Seed


Grazed and conserved grass is one of the most cost effective feeds available to producers of ruminant livestock and yet many farmers still don’t make the most of this valuable resource.


The Need to Re-Seed

This is highlighted in the DEFRA 2016 farmland survey, which shows that over 1.1 million hectares was in rotational grass under 5 years and over 6.1 million hectares was in permanent grass.

Knowing what we do about the UK grass seed market, we can calculate that the average permanent pasture in the UK is over 75 years old and even if we assume that only one third of permanent grassland can be re-seeded because of topographical restrictions this still means that over 2 million hectares of land that could be re-seeded is, on average over 25 years old.

So why does this matter?

A typical grass sward of over 5 years old will contain upwards of 40% weed grasses, which are far less productive than sown species like ryegrasses, and timothy.


Weed grasses such as annual meadow grass and Yorkshire fog are both lower yielding and have a lower feed value and so the loss is compounded.

The table above shows the loss in dry matter yield and energy yield as sown species declines in a sward. (AHDB)

An even worse scenario is where declining sown species leaves bare ground that becomes infested with broad leaved weeds such as Docks and Thistles.

A 10% weed infestation equates directly to a 10% loss in yield. In this scenario, if a rent of £395/ha (£160/acre) was being paid on the land, the rent on the productive area effectively increases by almost £44/ha because the productive ground is effectively carrying the unproductive ground, increasing the cost of every tonne of dry matter produced, as well as reducing the stocking rate of the holding.

Reseeding, or overseeding if reseeding is not feasible, should be considered if two or more of the following criteria have been met:

  • Sward productivity has fallen significantly
  • Proportion of sown species has fallen below 60%
  • High levels of native grasses and weeds are present
  • Significant evidence of soil compaction, especially at depth

Some farmers may opt to reseed a set proportion of the farm each year, eg. 10 or 15%, in a rotational pattern to ensure grass swards are regularly renewed.

There can however, be a large variation in the performance of fields across a farm, so the best way to identify swards eligible for reseeding is to measure grass growth regularly to identify the poorest performing fields.

For more information, please contact one of our Ruminant Specialists.


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