Reseeding a portion of farms every year is common practice, and the benefits of a reseeding programme are well proven. Reseeding revitalizes pastures, leading to optimum grass output, which boosts animal performance.

According to Chris Maughan, technical manager at Whelehan Crop Protection, while reseeding is a cost-effective investment much of the cost can be wasted and the benefits of reseeding can be negatively impacted if weeds in the new pasture are not controlled early.

"However, this spring, I have seen fields heavily infected with chickweed, and in some cases, the chickweed had almost smothered the grass.

"The end result will be a very poor pasture and a wasted investment,” said Chris.

Pastor Trio is the ideal herbicide for controlling weeds in new reseeds. Manufactured by Corteva Agriscience, it contains the three active ingredients: Florasulam, fluroxypyr, and clopyralid. It has the most advanced weed control technology.

"It is also effective on annual weeds such as redshank, charlock, mayweed and fumitory,” explained Chris.

Uncontrolled docks will seriously limit grassland output and productivity in a newly reseeded pasture.

“New reseeds are also very prone to thistle infestation. Even swards that have a relatively low number of thistles can be subject to heavy infestations in the new sward. If not controlled early, they can become a massive problem the following year. 

“Pastor Trio is highly effective on both seedling docks and thistles. It should be applied to new reseeds at 1L/ha in 200L of water," Chris added.

Many farms are planning to reseed pastures over the coming weeks and months. Farmers are advised to make weed control a central part of the reseeding programme.

"A post-emergent application of Pastor Trio will result in a weed-free sward and allow the new grass to tiller out which will ensure that the reseed can reach it's full potential. Pastor Trio can be applied from the third leaf-visible stage of grass growth," said Chris.

“Envy, is another great herbicide option from Corteva Agriscience. It contains the two potent active ingredients fluroxypyr and florasulam, and it is powerful against the same range of weeds as Pastor Trio, except for thistles.

“Both Envy and Pastor Trio are tailor-made for the control of weeds in reseeded pastures,” Chris added.

As clover is susceptible to Pastor Trio, Envy and other systemic herbicides that kill broad-leaved weeds, the option to exclude clover from the seed mixture has become more common.

The practice of sowing ryegrass first, followed by the application of a post-emergent herbicide, and finally over-sowing clover seed on a clean sward is becoming a popular practice.

“The effects of heavy infestations of weeds outweigh the benefits of clover in a reseeded sward.

Where clover has been included in the mixture and where weeds account for 20% or more of the grazed area, it is uneconomical to kill clover with Pastor Trio or Envy and re-introduce clover again at a later stage.

Clover can be over-sown three months after the application of Pastor Trio or Envy.

The technique of over-sowing clover was pioneered by Dr. James Humphreys of Teagasc Moorepark.

It involves mixing clover seeds at 5kg/ha with Phosphorus (P) and Potassium (K) fertiliser, followed by spreading the mix at 2.5 bags/ha in two runs at right angles to each other.

Quad bikes fitted with slug pellet applicators are also a good method of applying clover seed.

Apply about 7,500 gallons/ha of watery slurry after spreading the clover seed. This will help wash the seed into the soil and seal the ground to reduce moisture loss.

This method can also be used to introduce clover into existing swards. It can be very successful after silage cutting and also works well in grazed swards. However, tight grazing before and after over-sowing is vital for success.  

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