Top tips for successful autumn reseeding

Ground conditions are excellent at present and with silage ground coming back into grazing rotations once second cuts have been harvested, there will be an opportunity to reseed less productive swards.

For many farmers, summer and early autumn is the preferred time to reseed grass due to the increased availability of grazing ground after second cut silage.

However, when it comes to autumn reseeds, there is still a limited window to get new swards sown out and properly established before the winter sets in.

Therefore, the advice is to reseed at the earliest opportunity once grass supply, ground conditions and weather conditions are suitable.

Outlined below are 10 tips to consider when carrying out an autumn reseed.

While early reseeding is encouraged, this may not be an option. So, how late can you delay reseeding?

If weather conditions are favourable, farms on heavier land, or located in the northern half of the country, should aim to have grass seed sown out by the second week in September.

For farms on drier land, or located towards the southern half of the country, the cut-off date for sowing grass seed should be the third week in September.

Reseeding any later reduces the chances of getting new grass properly established before night frosts set in.

Old swards should be burned off before reseeding, especially if using a stitching or direct-drilling method.

Burning off the old sward will reduce weeds and older grasses competing with new grass for soil nutrients, or smothering grass seedlings.

Leave at least 10 days between burning off and ploughing. If there is a heavy infestation of docks in the sward, leave 14 days before ploughing.

Docks have a deep-root system and take longer to kill, so the extra days ensure that the chemicals give more effective control.

As grazing swards will have received regular applications of fertiliser, as well as urine and dung from animals, there is little point taking soil samples before reseeding such swards.

Soil fertility readings will be distorted from fertiliser and cattle dung. However, work on the principle that soil is low in lime, phosphate (P) and potash (K).

Spreading 1t to 2t/ac of lime is recommended and will help the new sward establish. Applying P and K through farmyard manure will condition soil and help new grass establish.

A compound NPK fertiliser can be applied if farmyard manure is not an option. Soil samples can be taken in winter, seven to eight weeks after the closed period for fertiliser.

However, if reseeding after silage and fertiliser has not been applied since early June, a soil sample can be taken in advance of reseeding

Where fields tend to hold surface water, new drains may be required or existing ones repaired before reseeding. If stitching in new grass, use a sub-soiler or pan buster to relieve compaction and improve soil aeration.

Use this opportunity to relocate drinking troughs to a more practical location to service multiple paddocks in the field.

Ploughing will be favoured by most farmers when reseeding, as it helps to improve drainage and soil aeration.

Once ploughed ground has been tilled, grass seed can be broadcast and rolled to improve soil contact. Alternatively, grass seed can be sown out using some form of precision drill.

However, there are drawbacks to ploughing. It tends to be more expensive and weather-dependent. Weed control and gathering stones are other issues to consider.

The process takes longer, as ploughed soil needs to dry before tilling and sowing grass seed, which shortens the window for reseeding as autumn approaches.

Ploughing leaves a softer seed bed, limiting the type of stock that can graze reseeds in September and October.

Stitching new grass into an existing sward tends to be less weather dependent than ploughing and is faster to carry out.

As there is less soil preparation work, it tends to be cheaper than a ploughed reseed. However, stitching or drilling machines are specialist machinery, so there is a greater reliance on contractors.

Stitching does not disturb the soil to the same extent, so seed beds are firmer after reseeding and weeds are less of an issue. Dense swards will benefit from discing or power-harrowing beforehand to expose soil before stitching or drilling grass seed.

On the downside, as the old sward dies back and decays, it makes the seed bed acidic, which can hinder germination of new grass seed. Applying lime before reseeding can remedy this problem.

Once new grass seedlings have established after stitching or direct-drilling, it is important to graze hard for two to three days, then rest the sward for three weeks. This helps new grass tiller and keeps older grasses under control.

For predominantly grazing swards, choose a mix that has more diploid grasses with late heading dates and good early and autumn growth. Include some Timothy on heavier soils and grasses with greater sward density. There is an option to consider a mix with herbal leys for new grazing swards.

For silage swards in a multiple cutting system, choose a mix with a greater percentage of late heading tetraploid grasses.

If the aim is to get a high clover content in the sward, autumn is the best time to reseed, as weeds are less of an issue.

Stitching should also be considered, as there tends to be fewer weeds after reseeding with less soil disturbance. Grazing the new sward tight helps to control weeds without spraying.

Some farmers prefer to sow out grass seed earlier, spray weeds, then stitch clover seed into the soil at a later date.

If going down this route, early reseeding is recommended to give time for the clover seed to germinate before winter.

Where an autumn reseed is established in August, there should be plenty of time to apply a post-emergence spray to control weeds. With a September reseed, there will be fewer windows for a post-emergence spray. If a spray cannot be applied, it is important the new sward is treated in early spring to control weeds.