Experts say controlling rushes could lead to improvements in the ground’s yield potential and offer a decent return on investment
Soft rushes, which thrive in boggy, acidic soils, have an obvious impact on grassland productivity.
However, experts suggest controlling the perennial weed could lead to improvements in the ground’s yield potential and offer a decent return on investment.
Dr George Fisher, an independent grassland consultant, says of the 5.2 million hectares (12.8m acres) of rough grazing in the UK, an estimated 0.5m ha (1.28m acres) of ‘in-bye’ land is ‘at risk’ from soft rush.
Its impact on grass growth is similar to that of weeds like docks and nettles, with Dr Fisher giving a ‘conservative’ estimate that for every per cent cover of soft rush, grass growth will be reduced by the same proportion.
Dr Fisher says recent soft rush control work in Northern Ireland, carried out over 12 months by the Water Catchment Partnership, reduced soft rush cover from an average of 81 per cent, to 20 per cent, representing a 75 per cent control rate. He says: “Controlling a 40 per cent infestation to 10 per cent could increase grass yields from 7tonne/DM/ha to 9.1tonne/DM/ha.”
When costed at £37/ha (£15/acre) for the herbicide product and application, Dr Fisher says there is potential for a good return on investment for sheep and suckler herds in terms of increased stocking rate, and it also would mean more, better quality silage was available for cutting.
It is possible to control rushes in two ways – with a boom sprayer applying selective herbicides, or using a weed wiper and glyphosate. Brent Gibbon, from Nufarm, says the ideal time to start a rush control programme is late spring. “If using a boom sprayer, apply the herbicide pre-flowering or top and apply to regrowth a month later,” he says.
“Farmers preferring to weed wipe should go in from late spring up to flowering when rushes have exceeded grass height. Pre-grazing with sheep provides good height differential between rushes and grass.”
Mr Gibbon adds he would advise using a contra-rotating brush weed wiper to get the best results.
“Longer term, a well-established, well-managed competitive grass sward will prevent significant rush re-infestation,” he says.
“Good field drainage where practical, combined with appropriate lime application to bring soil pH to 6.5 is also essential.”
However, caution needs to be taken to ensure the active ingredient MCPA, contained in soft rush control herbicides does not get near water sources.
“While pnenoxy herbicides, including MCPA, are key tools used to control soft rush, their levels in drinking water should not exceed 0.1 parts per billion,” says Mr Gibbon.
“These minute parts can be detected in water samples, so it is important to adopt effective stewardship and observe best practice guidelines.”