Top tips for successful autumn reseeding

With strong grass growth and second-cut silage completed on many farms, there is now an opportunity to take out poor-performing grazing swards for reseeding.

While the window of opportunity is shorter than with spring reseeding, August and early September is still a good time to lay down new grass.

However, key to a successful autumn reseed is timing.

Speed is the key; therefore, preparing ground and sowing out grass seed should be carried out as soon as weather conditions permit.

The earlier the new sward is sown, the greater the cover will be before winter sets in.

As such, the new sward will be more frost-tolerant and there is a greater chance of applying a post-emergence spray for weed control in autumn.

Outlined are some question farmers commonly ask before carrying out autumn reseeding.

How late can I leave reseeding?

Many farmers will ask 'when is it too late for sowing grass seed?'

Shorter days and cooler temperatures at night mean the later you leave reseeding, the slower it will be to establish.

Ideally, in the northern half of the country, grass seed should be in the ground by the first week of September at the latest.

Therefore, target 5 to 7 September as a cut-off date.

In the southern half of the country, this could be pushed back to the second week of September in a mild year, but no later.

Use the target dates to work backwards and plan out when burning off old swards, ploughing and tilling need to be completed.

How long should I wait after burning off an old sward?

Burning off an old sward before reseeding is recommended, as it limits the amount of weed grass coming through in the reseed.

Once sprayed, leave the sward for at least 10 days before ploughing.

If there is a heavy infestation of docks in the sward, leave it closer to 14 days before ploughing.

Docks have a deep root system, so waiting a few extra days will ensure the chemicals have killed the root system properly.

Around 10 days after spraying, you can graze off the dead grass with livestock, reducing the amount of trash to bury.

Is ploughing the best option for reseeding?

If the field has compaction or drainage problems, then ploughing is recommended to alleviate these issues.

Ploughing will open soils for aeration and remove surface water.

Provided existing drains are maintained and cleaned annually, there is little need to add further drainage.

A downside with ploughing is it leaves a soft seed bed. This limits what stock can graze a new reseed in autumn.

Rolling the ground after sowing grass, especially if broadcasting grass seed, will help to tighten the seed bed and improve soil contact.

Also, when ploughing, it may take a few extra days for soil to dry out.

This will delay tilling and sowing, thereby shortening the window for reseeding.

What are the advantages of direct-drilling into an old sward?

Direct-drilling into a burned off sward is a good alternative.

A big advantage is that the seed bed is firmer compared with ploughing.

Also, as the soil is not disturbed, there are fewer problems with weeds coming through in the reseed.

However, as the old grass decays, it makes the seed bed acidic.

Applying lime is advisable to improve germination.

When direct-drilling, it is important to graze the reseed frequently.

This keeps the older grasses from coming back and smothering new grass seedlings.

Should I take soil samples before reseeding?

Normally, the advice would be to take a soil sample before reseeding.

However, when reseeding in August, a soil test is not practical.

Swards that have been grazed and fertilised over the summer will have higher readings for P and K.

Therefore, it is better to wait until February or March before soil testing, as the sample will give a true reflection of soil fertility.

That said, if reseeding in autumn, applying lime, phosphate (P) and potash (K) is recommended to get seeds germinated.

Is a post-emergence spray needed?

Targeting early September as a cut-off date for autumn reseeding means there should be enough time to get a post-emergence spray applied by early October.

With autumn reseeding, weeds will be less of an issue compared with a spring reseed.

This means it should be easier to get on top of chickweed, red shank and docks.

Weeds compete with grass for nutrients, so spraying will increase the chance of successful autumn reseed.

Should I try to graze the reseed or will livestock damage it?

Ideally, you should aim to graze the reseed before closing for winter. This will help new grass to tiller out.

Sheep or weaned calves are more suitable for grazing reseeds, as they are lighter and will inflict less damage than stores or cows.

How quickly can I graze a reseed?

Once established, a quick test to determine if the sward is ready for grazing is to grab a few plants between the thumb and index finger and pull.

If the seedlings are pulled up from the soil, the sward is not ready to graze. If the seedlings remain in the soil, the sward can be grazed.

However, a new reseed should not be over-grazed. Best practice is to graze hard and fast, then allow the sward to rest.

Therefore, grazing should be limited to a two- and three-day paddock, before shifting animals off the reseed.

Use an electric fence to control grazing areas and protect grazed areas using a back fence.