The last couple of weeks have offered good opportunity for farmers to get up to date with much needed fieldwork.
Grass growth has been slow due to low night time temperatures but chickweed will have grown away through the winter and will need controlled especially in autumn reseeds. The presence of broad-leaved weeds will always take away from grass yield and quality.
Docks and chickweed are nutrient loving weeds, thriving in nutrient rich regimes, ie more intensively managed swards. Docks have only 65% of the feed value of grass and are unpalatable to stock.
Where infested swards are ensiled, their high nitrogen content adversely hampers a good fermentation, so leading to high pH silage that spoils quickly when opened and depresses intake. Dock seeds can also survive in silage and pass through the cow, infesting a field where slurry has been spread. The best defence against perennial broad-leaved weeds is to stop them establishing in the first place. This can be achieved by having a well-managed, dense sward, growing in well-structured non-compacted soil.
Over or under-grazed leys that have been poached, offer perfect conditions for weed seeds to germinate. Topping or mowing weed plants provides short-term visual satisfaction but stimulates active regrowth – so the problem gets worse not better. The long-term solution for controlling persistent weeds in grass is to use modern systemic herbicides.
A well-timed treatment with an appropriate herbicide can transform a weedy pasture into a productive ley, without the need for costly reseeding. Farmers may have to be more pro-active this year, as weeds have generally survived the mild winter and kind spring, so weed numbers are much higher than usual.
As thoughts turn to silaging, treating dock-ridden leys with DOXSTAR PRO four weeks before cutting will significantly increase the amount of grass that ends up in the clamp and improve silage quality. Docks have much less feed value than grass and pull down dry matter. FOREFRONT T is the most effective herbicide available to grassland farmers for the control of docks, ragwort, chickweed, thistles, dandelions, nettles and buttercups.
It is the longest lasting weed control product in grassland to date with a single well timed spray giving up to 18 months control so whilst it may appear expensive it really is good value for money. Once the established docks have been controlled it is best to keep the problem under control with follow-up treatments every year. This controls new growth of seedling docks that will reappear because all that is required for dormant seeds to germinate is a gap in the sward caused by poaching or tractor marks.
In fertile soils, the dock root system consists of a large tap root with a highly branched mass of smaller fibrous roots. This means what appears to be a small dock plant above ground may in fact be growing from a large rooting system below ground.
In order to achieve effective herbicide application docks should be at the rosette stage, with foliage 8-10 inches high or across. If grass has been cut or grazed a period of three weeks must occur to allow sufficient regrowth and a suitable target for spraying.
If applying FOREFRONT T, DOXSTARPRO or PASTOR, livestock should be kept out of treated areas for seven days before grazing and until the foliage of any poisonous weeds has died and become unpalatable, where clover is important SQUIRE may be applied in established grass.
There are two types of chickweed, common chickweed which is the most commonly found type, with a smooth leaf and mouse-eared chickweed which has a larger leaf than common, with a very hairy surface on the leaf and stem. Chickweed levels have built up very quickly this spring as this weed grows at lower temperatures than grass, and should be treated as soon as possible to avoid choking out the young grass.
Similarly, established swards that have been poached by autumn grazing tend to be very open in the early spring and this allows chickweed a chance to become a problem. Chickweed can mature and produce seed in five to six weeks hence there can be several generations in a year. Mouse-eared chickweed is very common on many local farms and it is important to note the distinct differences and treatments.
PASTOR applied at 2lt/ha, and DOXSTAR applied at 1lt/ha, will control both types of chickweed in established swards. Neither will check the growth of immature grass plants but are not clover safe. Where clover is part of the mixture then a clover safe product must be used. TRIAD is an SU type herbicide that is safe to clover when used correctly. As well as controlling a wide range of BLW’s TRIAD gives excellent control on chickweed. It will also control seedling docks (not those regrowing from roots), but has no effect on thistles or buttercup. Add SPRUCE to bring in control of these weeds also.
It is extremely difficult to achieve satisfactory control once weeds get beyond the seedling (young plant) stage. Clover content of the sward needs to be higher than is often appreciated. As a rule of thumb there should be 10 plants per square metre at the start of the season. Where plant populations are below this level it is more important to focus on other aspects and be prepared to treat the field as a grass only crop. High levels of nitrogen will significantly reduce clover growth, but by reducing nitrogen inputs overall forage yield will be reduced.
To ensure a well fermented silage sufficient fertiliser must be applied at the correct time for intended cutting dates. On average allow one day’s growth for each 2-3 units of nitrogen between application and cutting. The younger the grasses the higher the feed value but the lower its yield.
In general aim to cut before 50% of the ears have emerged to gain as much yield as possible. Short chopping speeds up fermentation and aids consolidation ensuring not to cut too short as long fibre is required for rumen function. Where conditions allow fast wilting in good weather this will increase the concentration of sugars and reduce effluent production.