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Weed control – essential tool to boost grassland performance

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Nufarm is a global manufacturer and supplier of crop protection chemicals. It synthesises and manufactures a wide range of chemicals including MCPA, 2-4 D, CMPP-P 2,4-DB, MCPB, 2-4 Dichlorprop-P.

Nufarm has produced phenoxies over 50 years and operates the largest flexible phenoxy production site in the world, at its state of the art’ global production plant near Bradford, West Yorkshire. The site also manufactures glyphosate, intermediates and inhibitors.

Weed control is not just about crop protection; it’s about boosting performance and it can achieve a 10:1 return on investment (ROI), says independent grassland consultant, Dr George Fisher.

“Weed control is a key element of productive grassland farming and it is important that herbicide applications are effective, made safely and with care for the environment.

“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).* see figure 1 below. Similar results can be achieved from grassland for silage. 

“Timing is everything. Achieving the above level of ROI is linked to correct timing of herbicide application.

“Herbicides applied too early or too late will not work as effectively, if at all.

“Generally, herbicides should be applied when weeds are healthy and the leaves actively growing. Once stem extension starts, translocation of the herbicide to the weed roots is insufficient for the operation to work effectively.”



“In established and permanent grassland, assess weed pressure as soon as grass starts to grow in spring,” explains Nufarm agronomy manager, Brent Gibbon.

“If you are going to achieve a significant return on investment, then early assessment allows time to prepare, choose the right product and plan for timely application, either using on-farm resources or getting in a contractor to do the job.

“April offers a good opportunity to make an application on Docks – a recommended product combination is Thrust 2.5 litres/ha + fluroxypyr 1.0 litres/ha.

“Follow the rule of thumb: following application, allow at least three weeks prior to first cut. Docks need two weeks of regrowth post cutting and then a further three weeks after application before cutting again.

“This approach can fit within a traditional three cut silage system but with multi-cut, it is best to tackle Docks either pre first cut or wait until late summer for weed regrowth when cutting is finished. As always, the weather in April may dictate which approach is adopted.

“Weeds in reseeds are best controlled when at the 2 – 6 leaf stage. Docks and Chickweed are the two most critical weeds to control in reseeds and must be controlled at the seedling stage. Herbicide application is essential before the first grazing.

“Clover safe options are available such as CloverMaster and Squire Ultra, but again, timing of application is crucial – before the first grazing.”

Reseeding: the five-step weed control programme, Nufarm’s Brent Gibbon

  1. Assess the weed burden pre-ploughing; at the outset, identify the species present and population levels.
  2. Sward destruction: apply Kyleo (glyphosate + 2,4-D) at 5L/ha. Unlike straight glyphosate, the mix completely destroys the old sward and also controls weeds such as Nettles, Thistles, and Docks together with Clovers and volunteer brassicas which frequently survive a straight glyphosate spray.
  3. Check the label for reseed interval: for example, the time between Kyleo application and drilling will range from seven days if ploughed, to 28 days if direct drilled. For grass and Clover mixes following ploughing you can go in 14 days after Kyleo application.
  4. Timing + application: 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 together with other annuals. Apply from April onwards.
  5. Clover + timing: if 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.

Weed control costs

  • £20/ha to £25/ha weed control product (Nufarm)
  • £12.63/ha contractor costs (NAAC 2017)
  • Total: £37/ha


DM value

Farmer utilisation (%)

Additional production potential

Concentrate replacement value


Grazing based dairy farmer increasing stocking rate: improving yield by 10%, from 10t DM/ha to 11t DM/ha


1t DM @12ME = 12,000MJ ME



1,778 litres/ha @ 29ppl = £516




Silage based dairy farmer increasing stocking rate: improving yield by 10%, from 10t DM/ha to 11t DM/ha


1t DM

@ 10.5 ME = 10,500MJ ME



1,361 litres/ha @ 29ppl = £395





Grazing based dairy farmer replacing concentrate feed: improving yield by 10%, from 10t DM/ha to 11t DM/ha


1t DM @12ME = 12,000MJ ME




0.83t of a 13MJ ME concentrate @ £250/t = £208