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Making The Most Of Grassland Re-Seeding

Grazing livestock producers should be re-seeding 5-10% of their grassland area each year on a carefully-planned basis for the greatest productivity and profitability. They should to do so in programmes that combine the most effective new sward establishment with the least time out of production. And they should look beyond ryegrasses alone to other species in general and hybrid  festuloliums in particular for the most palatable and robust seed mixtures.

 This was the key advice from grassland management and seed specialists at a recent meeting exploring latest developments in grassland re-seeding at DLF’s national forage academy at Didbrook in Gloucestershire.


“All our work shows a direct relationship between the proportion of productive grass species in the sward and grazing livestock profitability,” stressed Dr Michael O’Donovan, head of grassland science at Teagasc Moorepark in Ireland.

“At the same level of nitrogen, we’ve recorded new perennial ryegrass swards delivering
13-15 kg DM/ha compared to just 8.5 kg/ha from older pastures. They are notably more productive in both the spring and the autumn, extending the grazing season significantly. At the same time, the quality of grass they produce is markedly higher.

“As well as supporting almost an extra livestock unit per hectare, the most productive swards re-grow faster and make much more efficient use of applied nitrogen.

“Our studies show annual dairy herd grass utilisation rising from 7.4 t DM/ha with 1% of the grass area re-seed each year to 10.42 t DM/ha at a 15% annual re-seeding rate. We calculate the
current cost of re-seeding will typically be recouped in just two years and suggest re-seeding
5-10% of the grass area annually for the greatest overall farm value.”

Dr O’Donovan advises that re-seeding should always be carried out on a carefully-planned basis, with the pastures producing the lowest levels of utilised grass –  rather than necessarily the oldest – replaced each year.

He reports that Moorepark research shows no difference between the success of conventional plough-based, minimum tillage or direct drilling regimes in either spring or autumn re-seeding; insists that effective sward destruction and weed control is essential; advocates careful choice of grass varieties based on several key performance parameters; and  recommends light early grazing to encourage the greatest plant tillering.

Echoing Dr O’Donovan’s  advice, Monsanto technical development manager, Barrie Hunt pointed out that less productive grasses like Yorkshire Fog, rough stalked meadow grass and creeping bent as well as docks, thistles and other problem grassland weeds can substantially compromise sward output and quality.

“Unless the old sward is reliably destroyed and any problem weeds controlled as part of the reseeding process they will seriously undermine the establishment and value of the new sward, making re-seeding little more than a costly waste of time, effort and money in many cases,” he warned. “With intense pressures on dairy, beef and sheep margins, it’s equally important re-seeding takes pastures out of production for the least possible time.

“To address both these challenges we’ve introduced a specialist new 360 g/l Roundup for grassland farmers this season.”

 As well as proving markedly more reliable in controlling problem grass and broadleaved weeds under challenging conditions than a range of other generic glyphosates, Roundup Biactive GL is approved for spraying ahead of silage-making or grazing for the most rapid 

re-seeding turn-around.

“You can silage or graze five days after spraying then cultivate and drill your new seeds the next day, secure in the knowledge that even the toughest weeds have taken-up enough glyphosate to kill them,” said Barrie Hunt. “This cuts a good three weeks or more from the traditional approach of waiting for sufficient regrowth after utilisation to spray-off the old sward then a further 5-7 days before cultivation and sowing.

“So you can take a second silage cut or extra grazings off your old sward right up to the end of July and still re-seed at the early autumn timing that gives the best perennial weed control, rather than having to shut your ground-up for re-seeding from early June.

“What’s more, Roundup Biactive GL is rainfast in just one hour on annual grasses and couch, and four hours on perennial weeds and old swards; doesn’t need adjuvants with even the hardest water; has valuable in-built drift risk reduction properties; and carries a completely ‘clean’ hazard-free label for product use, handling, transport and storage.”

When it comes to new seeds, DLF forage grass product manager, Rod Bonshor urges managers to consider the site, situation and end use carefully in order to select the best species (let alone varieties) to include in their seed mixtures.

 “On good soils with adequate rainfall and fertilisation, ryegrasses continue to be our most nutritious and productive species,” he said. “But it’s important to appreciate the particular attributes of deeper-rooted species when conditions turn dry or water-logging is prolonged. 


“Equally, we’re seeing festulolium (ryegrass/fescue hybrids) giving the same speed of establishment, yield, spring growth, feeding value and persistence as hybrid ryegrasses.  And our most popular variety, Lofa is doing so with greater palatability and stress tolerance.

 “Interestingly too, grazing preference studies show the best of today’s cocksfoots and  timothys to be more palatable than ryegrasses with the added benefit of putting yield on the shoulders of the year. So they continue to have a valuable place in modern seed mixtures.” 


Rod Bonshor strongly advises managers to select grass seed mixtures carefully not only to suit the site they are to be grown on, but also their required place in the farm’s grazing or conservation regime and ultimately the ration. A final important consideration is the fertiliser regime and weed control options to be employed.

 He also believes they should be chosen on the basis of trials with mixtures themselves rather than simply their individual variety components. Ley mixture formulations, sowing methods and establishment management need to be carefully geared to the mixtures used for the most consistent results.