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Controlling docks with Future Beef farmer Michael McGuigan

Controlling docks with Future Beef farmer Michael McGuigan

Michael McGuigan has worked hard to control docks on his farm. Docks are the major weed of intensively-managed grassland. Despite the best efforts of many farmers to control them, their persistence is stubborn and unyielding.

There are many species of docks, but the most common and damaging in Ireland are the broad leaf dock and curly dock. Docks mainly prosper in silage fields, where soil fertility is high. Docks favour high index K soils, in particular, and silage fields tend to get high volumes of slurry and high K fertiliser.

Silage fields also tend to have an open sward, which favours dock establishment. Docks compete with grass for light, moisture and nutrients, thus reducing grass yields. The big concern is that with a heavy infestation of docks, silage yields could be reduced by up to 20%.

One dock plant can produce 60,000 viable seeds in a year and the seeds can germinate in the ground from July onwards in favourable conditions. Dock seeds can remain viable in the ground for up to 70 years and will germinate any time when conditions are suitable. Taproots have a large surface area and an ability to take in large amounts of water and nutrients. These taproots can penetrate deeper than one metre into the soil. In this way, it is easy to understand why and how docks persist in grassland swards.

Michael McGuigan is a suckler farmer with 30 cows, and farms outside Longwood in Co. Meath. He has worked hard on controlling docks over the last number of years. While walking the farm recently, it was evident that the majority of the docks are now gone.


Having previously been a stud farm, a part of Michael’s five year plan was to improve the grassland and to focus on better grass utilisation. The farm was divided with permanent electric fences and water troughs were added throughout the farm. With very little ryegrass in the sward, he had no choice but to start a reseeding programme. This is an easier way to eliminate all the weeds and docks than controlling them in existing swards.

Before any reseed, Michael sprays off the poor-quality sward with a glyphosate herbicide, which kills all surface weeds and scutch grass. After two weeks, the ground is tilled and sown. After another 5-6 weeks, Michael will always follow up with a post-emergence spray. Docks and other weeds can survive in a new ley and therefore need to be sprayed. Michael believes that the post-emergence spray is the most important application of a herbicide in the lifetime of a grassland sward.

Reseeding is a costly investment, so it is crucial that everything is done to give the new reseed the best chance to establish successfully. Controlling weeds with a post-emergence spray that is clover safe gives the greatest opportunity for creating a clean, weed-free sward that will be productive for the long term.

When to use the post-emergence spray?

When the seedling docks is the size of a €2 coin in the new pasture is the ideal time to use a post-emergence spray. This takes 5-6 weeks after sowing. Spraying too early could mean that the weed seeds have not germinated; too late and the dock root will have had time to develop. As Michael is focusing on incorporating clover into the farm, he will always use a clover-safe spray. There are a number of other considerations also to ensure success, including:

  • Follow the manufacturer’s recommendations closely, using the correct dosage and water rate;
  • Michael sprays in good conditions when its dull and calm;
  • The weed/dock plant must be actively growing;
  • All records are kept for cross-compliance purposes;
  • Spraying equipment and nozzles are in correct working order.

Existing grassland

Even though most of the docks and weeds are now under control, there is always outbreaks which can now be spot sprayed without having to spray the entire field. Michael has started incorporating clover by oversowing in the last year. In the year prior to oversowing, he will ensure that the paddock or field in completely weed free as sourcing a clover-safe spray is increasingly becoming a challenge.

Also keeping a thick, dense and leafy sward will reduce or even eliminate docks as grass will out-compete the docks for space, light and nutrients. 

 Image 1: Silage closed since April 4th

Keeping control of grass - maintain a leafy sward in May

Michael’s objective during the main grazing season (May to August) is to achieve high daily live weight gain from a grass-only diet. High animal performance will be achieved by maintaining a consistent grass supply for the herd and monitoring farm grass cover every 5 days. This will allow decisions to be made to alter grass supply early, for example, adjusting stocking rates or removing surplus grass.

The key grassland management guidelines for this period are:

  • Aim to consistently offer animals a sward where there is green leaf to the base and very little stem;
  • Ideal pre-grazing yield targets are 7-10cm (1,300-1,600kg DM/ha);
  • Maximum pre-grazing yield is 10-11cm (1,600-1,800kg DM/ha);
  • If this is exceeded, excess grass should be removed as baled silage (depending on grass supply);
  • Rotation length should be maintained at 19-21 days;
  • Early identification of surpluses by measuring grass weekly;
  • Surpluses are taken as a light crop of bales;
  • No more than a maximum of 14 and a minimum of 10 days ahead should be maintained during the main grazing season;
  • Farm grass cover should be maintained at 550-600kg DM/ha.

Michael aims to grow 14t DM/ha of grass this year, while reducing his chemical nitrogen by 10% through better use of clover. He has also added to the existing farm infrastructure by increasing the number of water troughs. All fields can be further sub-divided with pigtails and reels.

Managing clover swards

In 2022 , Michael selected paddocks which had excellent soil fertility, a pH of 6.7 and that were weed free for the oversowing of clover. Clover can provide nitrogen for grass growth as well as having a positive effect on livestock performance. Grassland management needs to be top-class and Michael  is very careful in managing these pastures.

  • The paddocks were grazed bare at the of last year to allow light into the pasture over the winter;
  • During this year's grazing season, the stock are let into slightly lower covers of 1,000-1,200kg DM/ha (dense grass covers that will shade out the clover is avoided);
  • The paddocks are grazed bare to 4cm at each grazing;
  • The application of chemical nitrogen will be stopped during the summer months;
  • Paddocks are grazed every 14-16 days during May and June;
  • Each paddock is grazed in 2-3 days and then stock are moved on.

This article first appeared in the Future Beef Programme newsletter for May. For more information on the Future Beef Programme, click here.