14 November 2025
Overseeding swards with a multispecies mix post-grazing is significantly more effective than broadcasting on higher covers, according to a study which shows it almost doubles the establishment rate.
Livestock farmer Wil Evans used an electro-broadcaster mounted on a quad bike to spread a grass, legume and herb seed onto fields of permanent pasture at his family’s beef and sheep farm in Powys.
He had been awarded funding by the Farming Connect ‘Try Out Fund’ to trial a range of options for broadcast-seeding existing swards, to establish which would generate the best results.
Wil’s aim is to reduce soil cultivation at 130-hectare Hendreseifion, near Machynlleth.
Species-rich seed mixes were broadcast into grass covers at a density of either 1900-2500 kg DM/ha pre-grazing or 1200-1400 kg DM/ha post-grazing at the end of June 2025.
After broadcasting, cattle were turned onto the pasture to aid seed-to-soil contact.
On 3 September 2025, 14 weeks after the seed was sown, a survey of the post-grazed field showed an establishment rate of 46% compared to just 28% in the previously grazed ley.
Independent agricultural consultant James Holloway, who advised Wil on soil fertility status
pre-seeding, says this outcome reflects the better seed-to-soil contact and reduced canopy competition in lower density covers.
Grazing removes bulk and opens the sward, creating favourable conditions for surface-applied seed.
Changing this sequence increases the risk of seed becoming trapped in leaf litter or buried unevenly, and that reduces germination and establishment, James adds.
The post-grazing system aligns with best practice - tight grazing or cutting, followed by light harrowing to expose bare soil and remove thatch.
The trial also revealed that some species established significantly better than others - perennial ryegrass, white and red clovers, plantain and chicory were the most prolific.
These species are better-suited to low-disturbance systems, offering rapid germination, competitive root development, and resilience under grazing, says James.
“Their success supports greater targeted species selection for surface sowing in future.’’
In contrast, yarrow, burnet, bird’s foot trefoil and other herbs were less consistent in establishing.
These have a greater sensitivity to competition, making them less reliable if they are broadcast instead of being incorporated in the soil, James advises.
Some of the seed used was coated with a biological treatment yet to be launched commercially but has been shown in trials by the company developing it, Fielder Nutrition, to provide early vigour and resilience under variable conditions, allowing a more uniform emergence.
While the Farming Connect project showed the treatment had little benefit, Wil says the timing of its application to the seed may have influenced that.
The recommendation is for the seed to be broadcast within 72 hours of treatment but due to very dry soil conditions and Wil’s reluctance to broadcast until the situation improved, the timeslot was missed except in one field; in that field emergence was three days earlier compared to swards where untreated seed was broadcast, and sowing into post-grazing covers led to a 76% increase in species successfully established compared to non-treated seeds.
James says greater efficacy may also be achieved from the non-chemical treatment under drilled or cultivated seeding, options where seed placement and soil contact are more consistent.
Post-broadcasting, cattle trampled the seed into the soil, mimicking the effect of double rolling and supporting establishment.
While this is cost-effective, it needs deliberate management, James cautions, including timing.
Trampling should be done within 24 hours of sowing and at a moderate stocking density – low enough to prevent compaction but sufficiently high to give adequate seed-to-soil contact.
Soil moisture content is important too - moist but not saturated.
To optimise timing, the trial utilised LoRaWAN sensors which provided real-time data on soil moisture and temperature at different depths, as well as air temperature, before, during, and after sowing.
Farming Connect’s red meat sector officer for mid Wales, Owain Pugh, who oversaw the trial, says this data was invaluable.
“It helped correlate environmental factors with seed germination and establishment success,’’ he observes.
Practical advice for other farmers
Control broad-leaved weeds like docks, thistles, and nettles before overseeding as limited herbicide options are available after sowing due to the plant diversity in multi-species mixes.
Get soils into the best shape by sampling to check pH, P and K status.
James advises targeting a pH of 6.5, a P index of 2 and a K index of 2-. “Assess soil structure and apply remedial actions where necessary before overseeding.’’
Prepare the seedbed with tight grazing or cutting followed by light harrowing and apply seedbed fertiliser and lime, if needed, in line with RB209 recommendations.
Use a specialised herbal ley mix containing species proven to perform when surface sowing.
Broadcast evenly across the surface and follow with consolidation by either double rolling or controlled trampling.
“If trampling, treat as a deliberate intervention not incidental grazing,’’ James recommends.
Rest for the ley for four to six weeks and then lightly graze with rotational grazing to encourage rooting and tillering.
PANEL
Overseeding can cost from £200–£400/ha, depending on the seed mix used and fertiliser, lime and labour requirements.
At Hendreseifion, the overseeded fields are predicted to yield an average of 8.6t/ha of forage, with that forage worth £1,179/ha, according to the AHDB Value of Forage Calculator.
When the establishment cost is weighed up against that return, it demonstrates a return on investment of 653.67% after four years, compared 416.81% if there had been a full reseed.
For Wil, while cost is an important consideration, the impact of other establishment methods is a reason why he plans to opt for overseed more generally going forward.
The fourth-generation farmer, who farms with his wife, Nia, was inspired to rethink his approach after embarking on a Farming Connect's Prosper from Pasture program, investing in grazing infrastructure and switching from suckler beef production to rearing dairy heifers on contract.
He is a firm believer that the method a farm selects to improve grassland must align with its own individual situation – the farming system, land and other factors.
“If I was milking cows, I might consider a full reseed but for me it is about lifting quality therefore overseeding offers a good solution,’’ he says.
The Try Out Fund presented him with a chance to test his ideas before he rolled these out further - this initiative funds individuals and groups of farmers and growers to experiment with ideas and bring them to life.
The trial clearly showed that overseeding with clover was a “no brainer’’, he says. “Going forward we can be confident that we can add value in this way, especially to our steeper land where we want to avoid loosening the soil.
“Interventions like power harrowing are a big ‘no no’ on a slope because that loose soil can quickly be washed away during the periods of extreme weather that we seem to be experiencing more frequently.’’
A valuable understanding he gained from the trial was just how important soil moisture is to sward establishment. “The conditions have got to be right, especially if you are using livestock to trample in the seed, without a certain level of moisture the seed can’t be properly worked in.’’
FARM FACTS
- 787ha owned and rented
- 320 R1 and R2 heifers a year contract reared for a dairy farmer
- 125 dairy beef cattle reared annually for Buitelaar
- 1,350 Improved Welsh ewes bred to Easycare tups
- Lamb sold deadweight to Dunbia
- 1,200mm average rainfall