Improving grassland productivity: CAFRE advises farmers to prioritise weed control

Jack Friar, CAFRE Beef and Sheep Adviser encourages farmers to act now to control the growth of weeds to improve sward quality and productivity.

As the grass-growing season gains momentum, the College of Agriculture, Food and Rural Enterprise (CAFRE) is urging farmers across Northern Ireland to prioritise weed control to maintain productive, high-quality swards.

With rising temperatures creating optimal conditions for weed germination and growth, CAFRE Beef and Sheep Adviser Jack Friar emphasised the importance of timely action.

“As temperatures are starting to rise, weeds are also starting to grow, so you need to be prepared to control them as they will reach optimum stage for application quickly. A good start is to walk fields and assess them for signs of weed growth,” he advised.

Why Weed Control Matters

Weeds such as chickweed, thistles, docks and ragwort can have a profound economic impact on grassland. They compete with grass for essential nutrients, light and water, reduce grazing availability, and ultimately lower the palatability and nutritional value of silage and hay.

“For every 1% infestation of the sward, such as thistles and docks, grassland productivity and forage quality will be reduced by 1%. If weed infestation is above 10%, action should be taken,” Friar explained.

A well-managed, dense sward is the most effective barrier against weed establishment. Maintaining a soil pH of at least 6.3, along with correct levels of phosphorus and potash, is crucial. Poor grazing practices and poaching of ground can create the perfect conditions for weed seeds to thrive.

While topping may offer a short-term fix, it can actually exacerbate the problem by stimulating further regrowth.

Weed Control in Northern Ireland: What Farmers Need to Know

• Docks

Among the most persistent and troublesome grassland weeds, docks thrive in fertile soils, particularly those high in potash.

“One plant can produce up to 60,000 seeds a year, which can remain viable within the soil for 50 to 70 years. Docks have only 65% of the feed value of grass and are unpalatable to livestock. Cutting will not control as new shoots will regenerate,” said Friar.

The most effective time to spray docks is when they are actively growing—typically late April to early May, and again in late August or early September. Products containing fluroxypyr and triclopyr are recommended, though repeated applications may be necessary. For clover-rich swards, clover-safe sprays are also available.

• Chickweed

Two types of chickweed commonly appear in Northern Ireland—common chickweed and mouse-eared chickweed. These thrive in cool, moist, poached swards.

“Both types of chickweed will be an issue in open or poached swards as it thrives in cool, moist conditions and can germinate and grow even at relatively low temperatures,” Friar said.

Products containing fluroxypyr and florasulam work well in early spring when conditions are cooler. As temperatures rise, a fluroxypyr-only product may be used. However, these are not clover-safe, so alternative products should be used where clover is a concern.

• Thistles

Thistles often appear in older swards that are low in nitrogen and phosphorus but high in potash. They can be either creeping (perennial) or spear (biennial). The best time for treatment is at the full rosette stage, when the plants are actively growing.

Herbicides containing triclopyr and clopyralid offer high root kill effectiveness, while MCPA-based products can control leaf growth, though with limited impact on roots. None of these treatments are suitable for clover-containing swards.

• Ragwort

Ragwort is not only invasive but also highly toxic to livestock.

“Small infestations can be managed by hand-pulling and ensuring root stock is removed. Regarding large infestations, spraying is highly effective,” Friar advised.

Spraying should be done early in the season before the plant begins to shoot. Importantly, livestock should not graze treated fields for at least 4–6 weeks post-spraying to avoid ingestion of poisonous decaying plant matter.

Safe and Legal Use of Plant Protection Products

“In conclusion: Before using any plant protection products consult a BASIS registered agronomist for the latest information on product availability and application advice. Anyone supplying plant protection products will have access to a BASIS qualified Adviser at the point of purchase, either directly or by phone. There will also be a helpline number on the label for technical queries,” Friar added.

Farmers must read and follow product labels and comply with regulations on application rates, and grazing and cutting intervals. Only those with proper certification (such as PA1, PA2A, PA6A) may legally apply pesticides in agriculture.

For further guidance, producers are encouraged to contact their local CAFRE Adviser via their DAERA Direct Office or visit the CAFRE Business Support area.