Now is the time for autumn reseeds

Autumn can be the best time for grassland reseeds, bringing all the benefits of sward rejuvenation at what is often the most Reseeding _photoconvenient time on the farm. However, whether it will repay the substantial investment – around £600/ha (£240/acre) for ploughing, tilling and sowing  depends on both the existing sward’s productivity and how well the reseed is done.

Siwan Howatson, Dairy Scientist with AHDB says “If it is carried out for the right reasons and in the correct manner, reseeding can be one of the most cost-effective investments on the farm.

“Furthermore, if it’s undertaken in autumn, reseeding will cause minimal loss of yield, as growth in the peak season won’t be lost.”

A survey conducted by AHDB in 2016 reported that 66% of respondents reseeded between August and October. Autumn reseeds also allow time for the seedbed to settle over the winter, allowing good structure formation.

Deciding to reseed

Deciding whether a reseed is due requires close analysis of the pasture, and it is worth undertaking this with an eye on the cost of opting out.

Siwan says, “Research indicates that pastures with a low proportion of perennial ryegrass are costing dairy farmers up to £250/ha/year due to a loss of grass dry matter production and reduced nitrogen efficiency use during the growing season.”

“For this reason it’s important to closely and regularly monitor each paddock’s performance to identify those which will benefit most. This includes assessing soil compaction and the weed burden as these problems can be dealt with at the same time.”

She continued, “Use the checklist below to determine if your swards are candidates. If you select two of more, reseeding should be considered.”

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

Preparing to reseed

“Before reseeding begins it’s important to check the field drainage system is working and soil tests are carried out to make sure you get the right nutrients in the soil,” explains Siwan.

Drainage can be assessed using the AHDB Field Drainage Guide, while the Healthy Grassland Soils Pocket Book will help with soil structure assessment.

Choosing the right varieties

“Variety selection is a key component in any reseed and it is important to select the most appropriate species for your situation, even at the field level. However, with over 900 varieties of perennial ryegrass available choosing the best can be a confusing and daunting task” Siwan continues.

The Recommended Grass and Clover Lists (RGCL) are the ideal place to start as they are drawn up after rigorous trials and testing, with as few as one in 20 varieties tested actually making it to full recommendation, classified as (G).

Key steps to successfully select varieties:

Step 1 – is it on the lists?

When selecting grass mixtures check that the varieties listed are present on the latest version of RGCL. AHDB has developed an online tool which can help you to choose the right varieties for your system.

Step 2 – what will the sward be used for?

Individual varieties can perform better under silage than grazing management and vice versa. It is important to consider whether the reseed will be mostly cut or mostly grazed, as selecting the correct variety for use can have a significant impact on financial returns. The RGCL testing programme provides specific data for all varieties for both silage and grazing management.

Selecting for grazing specific swards

Selecting for silage specific swards

Choose top-performing varieties under a grazing management in the RGCL

Select varieties with high digestibility

Aim for a maximum heading date range of 15 days

Aim for a maximum heading date range of 7 days

Later heading grasses tend to perform better in grazing than silage swards

Earlier heading grasses tend to perform better in silage swards

Match seasonal growth of variety to grazing demand


Aim for a maximum tetraploid content of 20% on wet soils

In wetter areas, choose varieties with higher ground cover


Step 3 – which traits are most important for your farm?

Once the purpose of the ley has been decided and a subset of varieties identified from the RGCL, individual traits most important to the farm should be considered. Varieties are also tested for attributes such as seasonal growth, ground cover and disease resistance.

Managing new reseeds

Good management of reseeds in the first year is key to help new pastures thrive and persist. This includes early grazing which accelerates growth rates and tillering in reseeds. Aim to graze autumn reseeds before the first winter to encourage tillering. Teagasc work suggests grazing at around 6-8cm in the autumn, but making sure it is grazed tight (4cm) before the winter. The challenge is to do this without over-grazing or poaching and the lightest class of stock available should be used. Also, remember to avoid applying excessive slurry.

Top tips for reseed management:

  1. Walk your reseed twice a week until post establishment
  2. Avoid overgrazing. Plant reserves necessary for survival and regrowth are stored above the ground in grasses, in the bottom 3-4 cm of pasture stubble
  3. Avoid cutting silage swards in the first six months, as this does not encourage the sward to tiller
  4. Carefully manage fertilisation. Avoid applying excessive slurry and use the Nutrient Management Guide (RB209) which provides guidance on nutrient requirements of grasslands
  5. Review weed control practices for new leys to ensure good establishment and to avoid variable ground cover.

The newly launched AHDB Grassland Reseeding Guide provides a best practice guide to help you achieve the best from your investment.

Siwan says, “It’s well known that well managed grass is the most cost effective feed for ruminants, but in order to maximise its productivity and maintain feed quality it needs regular renewal. Reseeding should improve pasture yield and quality and drive higher farm output, so reducing reliance on bought in feed.

“If the proportion of the farm reseeded each year increases, the amount of grass grown and used will also go up, which also results in increased farm profit.”