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Forage & Nutrition
Guide 2018
25
grassland. Some of the most commonly found species and their
growth habit are listed in Table 1.
ANNUALS
When establishing new leys, annual weeds are the most
common problem and a wide range of species can appear.
However, most of these fade away once the sward has been
cut and the density of the sward starts to increase. Common
chickweed is an exception to this rule and can appear in
established grasslands where there are bare patches of soil.
BIENNIAL WEEDS
Biennial weeds, such as ragwort and spear thistle, could have
a significant impact on grass productivity, particularly in
rotational leys. The plants germinate and produce vegetative
growth in the first season and the flower and die in the second.
PERENNIAL WEEDS
Many perennial weeds exist in grassland and can have long-
term implications for sward productivity. Perennials, such as
creeping thistle, buttercups and docks, can appear in a variety
of ways in the sward. They may survive as rhizomes or roots in
the soil during reseeding and, consequently, appear in the new
ley. Disturbing the seed bank at reseeding can also encourage
new weeds to generate.
Probably the most common way of weeds entering a sward is
through exploiting gaps in the sward (eg. areas of poor growth
or bare soil) and germinating.
Docks produce a large number of wind-transmitted seeds,
which can generate at any stage throughout the growing
season. In addition, the plant has a large tap root and rapid
growth response to nutrient inputs, an ability to grow in low-
light conditions and a resilience to trampling from animals, all
fuelling its competitiveness in grassland swards.
The seed is incredibly resilient (lasting over 25 years) and can
be passed through the gut of the animal, stored in slurries and
reapplied to land where it can germinate. As a result, docks can
rarely be removed by one treatment. Setting out a plan for the
season to managing your weed control is advisable.
CONTROLLING WEEDS
Spraying with a selective herbicide is the most effective
method of controlling weeds. This should happen when weeds
have a large proportion of leaf and are actively growing. Once
weeds develop flower heads spraying is less effective and it is
advisable to top them first and then spray the leafy regrowth.
Chemical control is expensive, so it is important to select
the correct herbicide and follow the manufacturer's
recommendations when applying the spray.
Good grassland management and a knowledge of the
growth habit of individual weeds (Table 1) can go a long way
to reducing the weed burden. Management practices that
encourage a dense competitive grass sward will reduce the
risk of weed infestation, as for many seeds, the absence of
light via a densely packed grass sward will stop them from
germinating.
Practices such as maintaining soil fertility, grazing, topping,
mowing and drainage will all help reduce weed burden and are
particularly effective in situations where herbicides will not
work, for example, with unproductive perennial grasses such
as couch or creeping soft-grass.
SUMMARY
Weed control is an essential requirement for good grassland
management. Select an appropriate herbicide for the weed
problem and spray at the correct stage of growth under
suitable weather conditions following the manufacturer's
recommendations.