Prompt and effective weed control should be high on the agenda for livestock farmers looking to safeguard the long-term performance of their grassland.
Now that it has rained in many areas and become warmer, weeds are growing quickly. Andy Bailey, Dow AgroSciences’s grassland specialist, says: “Farmers need to apply herbicide as soon as the weeds are at the optimum stage for control. Docks and thistles should be actively growing and healthy, at the rosette stage and up to 20cm across or high.”
Weed control is vital in maintaining the quality of grazing swards and silage as infestations can result in reduced yields and feed value, sub-optimal intakes and compromised livestock performance.
Choosing the correct herbicide to treat the appropriate weed challenge is crucial in ensuring optimum control. Generally perennial weeds such as docks, thistles and nettles are of most concern in grassland, as well as buttercups, dandelions and ragwort. In situations where docks are the main problem, selecting a narrow spectrum herbicide may be appropriate, however, where a field has a mix of docks, thistles and nettles, a wide spectrum product should be selected.
Either way, Mr Bailey says farmers looking to invest in the long-term productivity of their grassland will benefit from choosing a translocated herbicide.
He says: “Products based around triclopyr, fluroxypyr, clopyralid or aminopyralid, translocate into the root system and give more lasting levels of control.”
Translocated products generally achieve 10-15 per cent better control in the short-term than older chemistry products based around MCPA or 2,4-D, or a combination of these with CMPP (mecoprop), which just burn off the foliage. The long-term benefits of using translocated products are also likely to be greater, with the need for a follow up spray much more likely to be significantly reduced or not needed at all.
Mr Bailey also stresses topping is not an effective long-term weed control strategy and will only provide short-term visual satisfaction, while stimulating active regrowth.
To ensure the best treatment success from any herbicide, correct mixing and sprayer management is also important. Herbicides should be applied to a dry leaf, at least one hour before any scheduled rain. It is also important to calibrate farm sprayers prior to application to ensure the herbicide is applied at the correct dose rate, as cost effectively as possible.
“Water volume is also a key consideration when trying to get the best performance from a herbicide. Follow recommendations on the product label and do not be tempted to reduce water volume per hectare to try and speed up the process,” says Mr Bailey.
Once a good level of weed control has been achieved, steps should be put in place to prevent weeds from becoming a problem again.
Weeds will be quick to populate bare ground, so maintaining a tight sward through good grazing management and avoiding poaching can help stop weeds from ingressing.
“Make sure you also spot spray around slurry stores as weed seeds can survive in slurry which also creates an ideal environment for weed germination when spread on grassland,” says Mr Bailey.
Gareth Davies from Gareth’s Grassland Advisory Service believes all farmers should be looking at weed prevention, rather than fire fighting.
“You should always ask why weeds are there and not just how to get rid of them. I am a firm believer weeds thrive in imbalanced soils. Weeds are like a red flag that shows there is something wrong with the soils,” he says.
As a result, long-term weed control strategies should include establishing soil nutrient status and correcting any imbalances. Mr Davies also recommends all farmers graze new spring reseeds prior to silage cutting as part of a weed control strategy.
“Do not just leave spring reseeds until silage cutting – think about grazing with youngstock or sheep as soon as you are able to without damaging the grass,” says Mr Davies. This will help suppress the weed burden by grazing off new weeds and also promote good grass growth which will outcompete any weeds.
Clover should also be considered when planning herbicide use. Its presence can provide valuable nitrogen, increase intakes and maintain soil structure, however there are few clover-safe sprays available and they can struggle to give long lasting control.
Mr Davies says: “In clover rich swards, you could spray with a conventional herbicide to control the weeds and then stitch in the clover afterwards.”
All products should also be handled in a responsible and professional manner in line with sprayer guidelines, with appropriate personal protective equipment (PPE) worn.
Once in the field, using visual markers can also aid efficiencies of application and prevent overdosing or missing areas, says Mr Bailey.
“Because you do not have tram lines in grassland, you need some way of knowing how wide the sprayer is and when to turn. One way is to put stakes in the hedge once you’ve measured the field or use a sprayer with a ‘blobber’ on the end,” he explains.
Taking the time to check product labels to ensure buffer zones between spraying and watercourses are met – in line with LERAP requirements – is also crucial. This will help ensure the long term availability of grassland herbicides.
This responsible approach should be mirrored during herbicide storage, sprayer filling and wash down. Check drains at filling sites to ensure they do not flow into water sources and if possible, carry out sprayer wash down in the field.
Mr Bailey also reminds sprayers this will be the last spring farmers applying products under grandfather rights will be able to do so without a professional certificate of competence. “After November 16 this year, everyone needs to be qualified to apply professional products, so think about getting the training done before next spring,” he says.