Introducing a weed control programme to grass reseeds within the next few weeks will be vital for farmers to maximise their success.

Last autumn grass seed sales soared by approximately 30% as farmers attempted to restore scorched grazing and patchy leys following the extended summer drought. Furthermore, mild conditions allowed reseeding as late as November.

“If you were amongst those farmers who invested up to £450 to £500 per ha in reseeding and have yet to apply herbicide, then March provides an opportunity to clean up the weeds, and fully exploit the potential return on investment,” says independent grassland consultant, Dr George Fisher.

“Every 1% increase in weed ground cover will result in a 1% decrease in grass growth, consequently controlling common weeds in a grazing sward with 10% infestation levels could improve yield from 10t DM/ha to 11t DM/ha enabling improved grazing availability and subsequent stocking rates to deliver a 14:1 return on investment (ROI)," he said, adding that similar results can be achieved from grassland for silage.

However, Dr Fisher stressed that achieving that level success will be dependent this spring on set-up, to include a weed control programme, particularly since many of the reseeded fields did not receive a herbicide due to the late sowing dates, last year.

“Weeds such as seedling docks, mouse ear, fumitory, cranesbill, dead nettles and chickweed have been growing quite happily through the mild winter. These seedling weeds will become increasingly competitive with the young grass ley as spring temperatures rise.”

Nufarm Scottish agronomy manager, Iain Allan added: “Achieving that level of ROI is linked to controlling the overwintered weeds before they get too large. Weeds in reseeds are best controlled when at the two to six leaf stage. Docks and chickweed are the two most critical weeds to tackle in reseeds and must be controlled at the seedling stage."

He advised waiting for a mild forecast to be confident that the weeds are actively growing then mixing a tank of CloverMaster (2,4-DB)2.5l/ha + fluroxypyr 0.75l/ha for use through March to tackle problem overwintered weeds.

If clover is present, Mr Allan pointed out that fluroxypyr with 30g of Squire Ultra/ha, giving a mix of CloverMaster 2.5l/ha + Squire Ultra 30g/ha would be better.

“Farmers should note that a herbicide application is essential before the first grazing and leave at least a two week interval," concluded Mr Allan.

Getting ahead with spring reseeds

If you are planning to reseed in the next few weeks, then consider introducing the following programme to combat competitive weeds thinning out the newly sown grass, in particular resilient perennial weeds such as docks, says Iain Allan.

“Perennials are easy to control at the two to three leaf growth stage; timing is their Achilles heel. Once the grass becomes established, the weeds find it very difficult to get back into the sward. Also beware of competitive spring annuals such as fat hen which were a real problem last year and phenoxy-based products will be essential for control.”

• Sward destruction: apply Kyleo (glyphosate + 2,4-D), unlike straight glyphosate, the mix destroys the old sward and also controls weeds such as nettles, thistles, clover, docks.

• Check the label for reseed interval; it may be up to a month if not ploughing.

• Once the grass is sown and reaches the four leaf stage, consider a herbicide

• Think phenoxy-based herbicides, for example PastureMaster (2,4-D + MCPA) 2.5l/ha + fluroxypyr 0.75l/ha, to deal with seedling docks, thistles, nettles, chickweed, fat hen plus a whole host of other annuals. Apply from April onwards.

• If clover is present, then from one trifoliate leaf onwards apply Clovermaster 2.5L/ha + Squire Ultra 30g/ha.

• Always read the product label and seek advice from a BASIS qualified agronomist.