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Top tips for autumn grassland reseeding

Maintaining healthy, productive grassland is crucial for the success of livestock farming businesses.

Defra statistics show that over half of livestock farms in the UK consistently reseed their grass swards at least every five years to refresh and enhance pasture quality1.

The most common time of year to do this is autumn, according to AHDB survey results, to allow time for the seedbed to settle over winter and minimise yield losses2.

Ahead of reseeding, it is crucial to invest time in preparing the grassland to achieve the best results.

This involves ensuring optimal soil conditions, effectively controlling weeds, and building a favourable soil structure, to achieve an environment that encourages seed germination and establishment.

This blog will guide you through the necessary steps to prepare your seedbed over the summer ahead of successful autumn reseeding.

Soil testing and analysis ahead of autumn reseeding

Carrying out thorough soil testing and analysis during the summer allows farmers to identify pH levels and nutrient deficiencies, so precise amendments can be made to ensure a balanced, fertile environment for grass growth.

Balancing pH levels

Soil pH affects nutrient availability and microbial activity, both essential for healthy grass growth. Grass thrives best in a slightly acidic to neutral pH range (6.0-6.5).

Farmers planning to reseed in autumn should conduct soil tests in early summer to determine current pH levels.

Then, if the pH is below 6.0, lime can be applied to the land to raise the pH level.

The required lime amount depends on soil texture and current pH. Light, sandy soils may need less lime compared to heavier, clay soils.

Ideally, lime should be incorporated evenly across the field two to three months before reseeding, to allow time for it to react with the soil.

Checking nutrient status

Key nutrients for grass growth include nitrogen (N), phosphorus (P), and potassium (K).

Each nutrient plays a unique role: N promotes foliage growth, P supports root development, and K enhances overall plant health and stress resistance.

To ensure adequate nutrient levels, perform a comprehensive soil test in early summer to allow ample time to make necessary amendments before autumn reseeding.

Applying OCI Nutramon for successful autumn reseeding

Applying the right fertilisers at the appropriate time is crucial to achieving optimal nutrient levels for autumn reseeds.

With a balanced formula of 50% nitrate nitrogen and 50% ammoniacal nitrogen, OCI’s Nutramon fertiliser provides both fast and long-lasting nutrient action to promote seedling growth.

This boost supports grass establishment, promoting strong root systems that help achieve a dense, healthy sward that provides high-quality forage.

By applying OCI Nutramon before reseeding, within the spreading regulations, you can maximise nitrogen availability when the grass seeds need it most, while minimising the risk of excessive leaching due to rain.

Find out more about the benefits of using OCI Nutramon on your grassland.

Effective weed control

Proper timing, selection, and application techniques for herbicides are essential to eliminate competition from weeds and create a favourable environment for new grass seedlings.

The best time to apply herbicides for autumn reseeding is in late spring to early summer, when perennial weeds are actively growing and more susceptible to herbicides.

Treating weeds before they set seed reduces their ability to propagate, leading to a cleaner seedbed by autumn.

It is recommended to use selective herbicides that target broadleaf weeds, like docks, thistles and nettles, without harming grass species.

Combining this with mechanical methods, such as weed wiping or hoeing, helps achieve a more comprehensive approach while minimising environmental impacts.

Soil cultivation for autumn reseeds

Proper soil cultivation practices address issues such as soil compaction, weed infestations, and poor soil structure, creating an optimal seedbed for grass seed germination and establishment in autumn.

Ploughing

In fields with severe compaction, deep ploughing helps break up compacted soil layers which restrict root growth, water infiltration, and air exchange, leading to poor plant health.

By turning the soil, ploughing buries weed seeds and old vegetation deep enough to prevent them from germinating and competing with new grass seedlings.

Power harrowing

For fields that do not require deep cultivation, power harrowing helps break up the soil crust, creating a finer tilth and smooth, even seedbed, which encourages seed-to-soil contact, moisture retention and root development.

Multiple passes with the harrow may be necessary to achieve the desired soil texture, especially if the soil is heavy or cloddy.

Rolling

After harrowing, using a roller to firm the seedbed ensures the reseeds will be in close contact with the soil and minimises surface evaporation. This not only improves water retention, but it also supports uniform germination and establishment.

Rolling is particularly important for consolidating the soil surface in light, sandy soils where loose particles can impede seedling development.

Grassland management ahead of reseeding

Effective grassland management practices help manage the existing vegetation, reduce competition for new seedlings, and optimise seedbed conditions for successful grass establishment.

Controlled grazing

Implementing controlled grazing in late summer, several weeks before the planned reseeding date helps ensure the existing grass is sufficiently grazed down without giving it too much time to regrow before reseeding.

It is advised to graze the sward tightly down to 5cm, to remove most of the above-ground biomass and reduce competition for light, water and nutrients, which are crucial for the new seedlings.

Continuously monitoring sward height is crucial to ensure it does not fall below 5 cm, which could lead to soil compaction and damage to the root systems of existing grass.

Mowing

If controlled grazing is not feasible, mowing in late summer is an effective alternative to manage the vegetation before reseeding.

Using a rotary or flail mower that can handle the existing vegetation avoids leaving large clumps of cut material, which could hinder seedling growth.

In some cases, a combination of controlled grazing and mowing may be the best approach. For example, you might graze the field first to reduce the bulk of the biomass and then mow to achieve a more uniform sward height and fine-tune the seedbed preparation.

Irrigation management

Where feasible, supplemental irrigation can help maintain adequate soil moisture on forage ground, creating optimal conditions for reseeding even in unpredictable autumn weather conditions.

Irrigating the field a few days before sowing to moisten the topsoil (0-10 cm) encourages rapid water uptake by the seeds and initiation of germination processes.

After sowing, light irrigation helps settle the soil around the seeds, enhancing seed-to-soil contact and preventing surface crusting.

Irrigation tips

  • Irrigate during early morning or late afternoon to minimise water loss through evaporation.
  • Adjust the frequency of irrigation based on soil type, weather conditions, and crop water requirements – sandy soils may need more frequent irrigation than clay soils due to their lower water-holding capacity.
  • Check soil moisture levels regularly using sensors or manual methods like soil probes, using real-time data to adjust irrigation schedules and avoid over- or under-watering.
  • Ensure your field has adequate drainage to prevent waterlogging, which can harm seeds and seedlings.
  • Apply water in smaller, more frequent amounts to prevent soil saturation, waterlogging and associated root diseases.

Proper summer preparation for successful autumn reseeding

Investing in thorough ground preparation during summer will help make the most of autumn reseeds, yielding long-term benefits for your pasture productivity and livestock performance.

For more in-depth advice on reseeding, based on farm-specific factors, contact your local agronomist or farm adviser.

Read more advice on optimising grass growth for your livestock.

References

  1. Defra (2024) – National statistics – Grassland and grazing
  2. AHDB (2024) – When to reseed grassland – autumn or spring?

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