Principles of autumn reseed

Tuesday, 15 August 2023

UK farmers embark on a crucial agricultural practice that is pivotal to the success of their livestock management and forage production: autumn reseeding.

This is one of the most cost-effective on-farm investments. It involves establishing new pasture or fodder crops during autumn to ensure a consistent supply of high-quality feed for grazing and silage in the coming year. The principles governing autumn reseeding play a pivotal role in enhancing livestock nutrition, supporting sustainable farming practices, and maintaining the productivity of the agricultural sector.

Timing and species selection

The timing of autumn reseeding is critical to its success.

Typically, it is carried out from mid-August to mid-September in the UK. Spring or autumn reseeding are equally advantageous, and the choice will depend on the farming system, when the field is available and when conditions are good.

The autumn window allows the newly seeded plants to establish their root systems before winter, leading to vigorous growth in the following spring.

Species selection is equally important. You must choose grass and legume species well-suited to their specific soil and climate conditions. Grass species like perennial ryegrass, timothy, meadow fescue, and legumes like clover are commonly chosen for their nutritive value and resilience.

While autumn reseeding may make sense from a feed budget perspective, soil conditions deteriorate as autumn progresses, lower soil temperatures can reduce seed germination, and variable weather conditions reduce the opportunity to apply post-emergence spray and graze the new sward. For these reasons, it is important to get in there early, especially for any mixture containing red clover, as they need to be in by August, and white clover needs to be in by September.

Soil preparation

Effective soil preparation is vital for a successful reseeding effort.

The soil should be free from compaction, weeds, and debris. You may undertake practices such as ploughing, harrowing, or tilling to create a suitable seedbed.

Check for any soil structure issues – a plough may sort some of them out, but a subsoiler may be needed if the issue is deeper.

Additionally, soil testing helps determine nutrient deficiencies, allowing for precise fertilisation to support initial plant growth. Take a soil sample at a depth of 15 cm – deeper than soil sampling in established swards, as cultivation will disturb the soil.

Seedbed establishment

Achieving proper seed-to-soil contact is essential for germination and establishment.

You can use methods such as broadcasting, drilling, or overseeding existing pastures. Drilling is often preferred as it provides more accurate seed placement and depth control, promoting uniform growth and minimising competition from established vegetation.

Research conducted by Teagasc has found there is little difference in the outcome between reseeding methods once completed correctly.

For a full reseed, it is recommended to spray the old sward using a product containing glyphosate. For a full reseed, plough, press and work down to a firm and fine seedbed. Drill or broadcast the seed onto the rolled seedbed to place it no deeper than 1 cm. Ring roll or light harrow to ensure maximum contact between seed and soil, but avoid burying the seed below 1 cm, especially small-seeded species such as clovers and timothy.

Over-sowing or stitching in can be a way to rejuvenate old or damaged grass without the cost of a full reseed. As existing grass or weeds can out-compete the new seedlings, good soil structure and nutrients are still important.

The best time is summer, as the existing grass is less vigorous, and soil temperatures will be high, although soil moisture may be a limiting factor.

The seedlings need light, so 40% of bare ground should be seen before over-sowing is considered – harrowing in two directions may help.

The seed can be broadcasted or directly drilled, and the existing sward can be sprayed off beforehand or ‘checked’ by hard grazing or cutting. Seed-to-soil contact is still important, so roll after sowing or allow sheep to graze the field for 7–10 days to tread the seed in. The seed rate will change depending on sward conditions – a minimum of 8 kg per acre and up to 15 kg for severely damaged swards.

Do not apply nitrogen, as it will only boost the growth of the existing sward (if it has not been sprayed off).

Fertilisation and nutrient management

Reseeded areas require adequate nutrients to flourish. Applying fertilisers based on soil test recommendations ensures that essential nutrients like nitrogen, phosphorus, and potassium are available for plant uptake. You should approach nutrient management with care to prevent over-application, which can lead to environmental concerns.

For autumn reseeds, the recommendation for moderate soil nitrogen supply situations is 0–50 kg per ha, depending on the sowing date and soil nitrogen supply.

Remember to deduct any nutrients applied in the seedbed from the first season’s grazing or silage/hay requirements.

Weed and pest management

Weed competition can hinder the establishment of reseeded areas. Implementing effective weed control strategies, such as using pre-emergence herbicides or mechanical weed removal, is crucial during the initial growth stages. They are best controlled when the grass is at the 2–3 leaf stage.

Docks and chickweed are two of the most critical weeds to control in new reseeds; it is important to control these at the seedling stage by applying the herbicide before the first grazing. Monitoring for pests like slugs and insects is equally important to mitigate potential damage.

Grazing management

Proper grazing management after reseeding is vital for the long-term success of the pasture.

Allowing the newly seeded plants to establish strong root systems before intensive grazing begins is essential.

You should practice rotational grazing, which involves dividing the pasture into smaller sections and moving livestock regularly. This prevents overgrazing and promotes even utilisation of the forage. The aim is to produce a uniform, well-tillered, dense sward.

Silage production

In addition to grazing, you can also utilise autumn-seeded areas for silage production.

Silage is a fermented feed made from harvested grasses or other crops. Reseeded pastures can provide high-quality silage with improved nutritional content. Harvesting the grass at the right stage of growth and ensiling it properly are critical steps in producing high-value silage.

Monitoring and adaptation

Continuous monitoring of reseeded areas is crucial to detect any challenges early on. You should observe plant growth, assess forage quality, and address any emerging weed or pest issues promptly.

Flexibility is key; adaptation of management practices based on changing conditions can ensure the best possible outcomes.

Long-term sustainability

When done correctly, autumn reseeding aligns with the principles of sustainable agriculture. It enhances soil health, promotes biodiversity, and supports efficient land use. By rotating pastures, you reduce the risk of soil erosion and nutrient depletion, contributing to the long-term sustainability of your farming operations.

In conclusion, autumn reseeding serves the dual purpose of providing high-quality forage for grazing and silage production. The principles guiding this practice emphasise careful planning, appropriate species selection, precise soil preparation, and vigilant management.

By following these principles, you can ensure the successful establishment of productive pastures, boost livestock nutrition, and contribute to the overall sustainability of the agricultural sector.

Further information

RB209 Section 3 Grass and forage crops

Recommended Grass and Clover Lists (RGCL)

Grassland reseeding