Weed control can often prove a difficult task at this time of the year as when grass growths really begin to get going, weeds can spring up, especially with heat and moisture in the ground.
It would not be unusual to see toppers out in paddocks after cows have grazed to correct grass quality as well as to mechanically control weeds.
The grass plant has been under a bit of stress in the last number of weeks due to a lack of soil moisture, which has caused many to turn to seed quite early, causing issues with quality and leading to toppers having been put on.
Before starting weed control, you need to identify which weeds need to be dealt with and then discuss with an adviser or agronomist which products would rectify your problems or whether mechanical ways of weed control will suffice.
However, it may not be the case where one product will cover all, as you may have paddocks that have different issues and may require different products to be used.
Topping
Topping paddocks helps prevent the spread of weeds by making their growth less vigorous and reducing their competitiveness in the sward.
Topping is most effective when it removes the flower head and upper leaves in dense areas of thistles, docks and nettles before the bud opens.
It is recommended to top a paddock again on month after the first topping to stop the weeds from flowering.
Topping is also a popular measure to correct grass quality, though many would argue that taking out surplus paddocks for bales is more effective as no grass is wasted.
Pre-mowing is another option as cows will eat the stem and the lush grass in the paddock, increasing intakes as the grass is readily available to the cow.
This works well if paddocks have gone too strong and you are looking to ensure that grass does not run out.
The fear with topping is that it will affect the regrowth rate of the sward if paddocks are not topped immediately after grazing, as the pre-grazing cover of the next rotation may be affected.
Weed control
Realistically, topping will control weeds in the short-term, and may work in the long run if you are persistent for the next number of years, but often farmers will have to use some herbicides to get full control.
Knowing your fertility status is important, as it will indicate whether or not your soil needs lime, phosphorus (P), or potassium (K), which will allow you to grow more grass, limiting space for weeds.
Dock control at this time of the year is vital as they are at the rosette stage (measuring 150-200mm in diameter), which is the easiest stage to kill the weed.
Best practice is to spray docks shortly after a reseed ,which will stop them from establishing due to competition in the sward. A well-established reseed will also limit and suppress weeds.
Thistles should also be sprayed now, as now they will begin to develop stolons, branch out, and cover the grass, which will kill what is underneath.
The products used to target weeds are not cheap, so application must be precise and accurate to get optimal results.
To ensure precise spraying, it is important to read the label of the product carefully to make sure you are applying at the correct rate.
Tips for spraying:
- Make sure the product is suited to killing the weed;
- Read the label carefully, adhering to buffer zones and rates;
- Keep a record of the product being used;
- Spray in suitable conditions – not windy or wet;
- Wear protective gear;
- Wash spraying equipment after use;
- Adhere to recommended time between spraying and grazing, or cutting of silage (around seven days after);
- In the case of ragwort, animals should not be allowed in until the weed is completely rotten and unpalatable.
There are a few product options for the control of docks in your clover swards, however, for the treatment of chickweed, nettles, thistles, or dandelions, there are limited options.
If clover is present in your swards, you must select a clover-safe product, which rules out a lot of conventional products. If the seed and stem are present, the weeds should be topped first and then sprayed a couple of weeks later.
Farmers should target the non-clover paddocks first and get the weeds completely under control and then look to establish clover in these paddocks next April or May.
Controlling weeds prior to clover establishment will prevent issues further down the line.
Controlling weeds in your paddocks this summer will maximise grass yield, improve silage quality, increase grass utilisation, and eliminate any health risks to livestock caused by certain weeds.
