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Opportunities To Control Rushes 

23 June 2020

Rushes are a major challenge to beef and sheep producers across the country.  Rushes are an indicator of poor fertility, poor drainage and low soil pH.  However, when you look at the conditions that rushes will grow in, you will see that rushes have the capacity to grow in a very wide range of pH, P&K status and moisture contents.  Although they seem to be a very competitive plant, they are not as competitive as you might think.  In fact, a good crop of grass will always outcompete a crop of rushes.  In order to win the fight against rushes, we need to alter our focus and put more emphasis on optimising grass production 

Drainage

To do this, firstly correct any major drainage problems, this may be as simple as clearing drainage outflows, or as complex as installing a whole new drainage system.  It is also important to consider soil compaction, alleviating this will boost grass growth and give grass the competitive edge over the rushes.  Lime would be next in the order of importance.  By adding lime, soil pH will rise towards the ideal of 6 for grass.  Don’t apply lime before taking a soil sample, to understand your requirement and maximise your return on investment.  Phosphate and Potash levels should also be corrected, this can be done in one step by using products like Muriate of Potash or triple super Phosphate.  You could also target applications of organic manures to gradually build up soil P&K reserves.   

Apply Nitrogen

Last on the order of things to apply is nitrogen, often referred to as the green paint brush, nitrogen fertiliser is a powerful tool to boost grass growth, particularly in the spring.  However, when pH is low and drainage is poor, the return on investment is very low with nitrogen. For rushy fields, it may be worth stopping applying nitrogen and investing in lime instead.   

While growing more grass should be the priority in the fight against rushes, any fields that have established stands of rushes do require some form of treatment to kill the rushes, while you work to improve soil health.  The options for killing rushes are many and varied.  Some are highly effective, while others burn a lot of diesel and do very little. 

Topping

Topping is the most common treatment for controlling rushes in Scotland.  Many try to do this prior to flowering to stop the plant from producing seed.  A valiant effort but as rush seeds survive in the soil for at least 60 years, the effort is ultimately in vain.  This operation is costly in terms of diesel and machinery depreciation but has relatively little impact on the overall rush population.  Topping has a place, on organic units or in environmentally sensitive sights but better options exist for achieving good control on most sites. 

Spraying

Spraying with MCPA is a longstanding and very effective treatment for fields with rushes.  The spray is a selective herbicide, killing rushes and other broadleaves weeds, without adversely affecting grass.  This option is relatively cheap and very effective in killing rushes.  However, the environmental impact of spraying must be considered before opting for this method of control.  MCPA presents a major risk to aquatic life, so farmers must ensure that buffer zones are adhered to and that a suitably qualified operator does the job.  In the right hands, this is one of the best options for controlling rushes.   

Weed Wiper

A more modern method of rush control is contact weed control, using a weed wiper.  After grazing the field hard, the rushes will stand well above the grass sward, meaning a weed wiper can be used to apply Glyphosate directly to the rush plants, to good effect.  The weed wiper has the advantage of needing very little chemical to cover a lot of ground, the contact approach rather than spray approach means that the weed wiper provides a targeted control method.  It is particularly useful where you want to preserve clover or herbs in your pasture.  This is an economic and environmentally sensitive method of controlling rushes. As with all machine operations, it is only as good as the operator using it.  Remember that weed wipers are only licensed to use glyphosate, other products are illegal to use and are also likely to be less effective.  

Cut & Bale

With good weather, many producers will be tempted to cut and bale their rush crops Similar to topping, this is likely to be a lot of work and be relatively ineffective, without a follow up treatment.  Be very cautious if using rushes as bedding, if they haven’t yet flowered, then they can be used.  However, if they have flowered, then there is a major risk of taking rush seeds from your poorer land and then spreading them on your silage fields, perpetuating a problem.  

Reseeding

Burning off and fully reseeding a field is the extreme option to eliminate rushes but if doing this, you need to make sure that the grass establishment will be ideal.  A reseed without correcting pH issues and drainage is a very expensive method of getting 1 year of reasonable grass before rushes start to encroach again. If you are ploughing a field and conditions/land allow, consider deep ploughing the field to put rush seeds, plants and trash as deep as you can.  While a good option, shallow soils in many of the fields where rushes are a problem, wouldn’t allow for this to be done.   

At the time of writing, May, rushes have not yet reached their reproductive stage, so are growing vegetative, as such they are growing rapidly.  When they change to their reproductive state (flowering), growth dramatically reduces, as the plant changes its priorities from producing leaves to producing seeds.  A plant in its vegetative state will take up much more chemical than one in its reproductive stage.  You have a much better chance of achieving a good kill before rushes have a flower on them.  Later in the year, when rushes are flowering, it is worth thinking about cutting the plants, allowing a few weeks of vegetative regrowth before spraying or weed wiping.   

MCPA is probably the most economic method of rush control currently available.  However, with many other sprays being taken off the market, it is very important that everyone using MCPA treats the product with respect and adheres to best practice, otherwise we risk losing another vital chemical from our systems. 

The fight against rushes is a huge challenge to most beef and sheep farmers.  For more information on controlling rushes, please visit the FAS website, or contact the helpline.       

Robert Ramsay, robert.ramsay@sac.co.uk

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