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Growth Watch: Controlling weeds in May reseeds

Growth Watch: Controlling weeds in May reseeds

The timing of reseeding plays a crucial role in the ability to control problematic weeds going forward. Where reseeding was completed earlier this year, there’s an opportunity to tackle problem weeds, like docks and chickweed, now. James Fitzgerald & Seán Cummins, Green Acres Advisors provide advice

James Fitzgerald and Seán Cummins, Programme Advisors to the Green Acres farms offer some timely advice on Controlling weeds in May reseeds and share the current grassland management plans of two of the programmes farmers; Shane Cranny and Michael Culhane here.

The Advice

Best practice weed control in reseeds

Problem weeds, like docks and chickweed, if not tackled post-emergence, will complete with the grass seedling and potentially smoother the grass plant. For best control of grassland weeds in reseeds, it is best practice to apply an appropriate herbicide before grazing, with the timing of this application generally targeted 6-8 weeks post sowing.

In terms of the efficacy of herbicide products, they tend to work best when the weed targeted is at the seedling stage. This is particularly the case for dock seedlings. Where docks are allowed to become established, its tap root – which provides the plant with an enviable level of persistence - may make removal from the sward more challenging down the line.

Before purchasing a herbicide, make sure to consult your advisor or merchant to ensure the product will achieve the desired results and is suitable for applying to newly-established swards. Where a product has been selected, ensure that conditions are appropriate for spray – not to wet, windy or dry and that the rest period between application and grazing is adhered to.

In addition, under cross-compliance regulations, farmers are required to adhere and follow the instructions on the product label, which pesticide users must comply with the regulations as outlined in the Sustainable Use Directive.


Shane Cranny  and   Michael Culhane

Farmer focus: Shane Cranny, Myshall, Co. Carlow

  • Growth: 73kg DM/ha/day
  • Demand: 42kg DM/ha/day
  • Average farm cover: 759kg DM/ha
  • Stocking rate: 2.58LU/ha
  • Days ahead: 18

The farm here needed rain and luckily enough it arrived last Wednesday and Thursday. Growth rates had stalled somewhat before this – falling to 35kg DM/ha/day – but with the arrival of moisture they have climbed again to 73kg DM/ha/day.

Demand on the farm has dropped considerably over recent weeks, with the re-introduction of first-cut silage ground to the rotation. First-cut silage crops yielded well and just over 85% of the yearly silage requirement is in the yard, with the balance to be made up with surplus bales between now and the end of the year. Some 10ac of paddocks will be taken out for bales in the near future and if further bales are required to correct the wedge they will be taken out.

Spring growth has been challenging on the farm here in recent years and to correct this, I plan on reseeding 12ac this year. 4ac have already been completed and have received a post-emergence spray, while a further 8ac has been sprayed off for reseeding later this week. I have been measuring grass for almost three years at this stage and the worst performing paddocks in terms of overall yield and spring growth will be targeted for reseeding this year.

In terms of fertiliser, the volume of nitrogen being applied to grazing ground tends to fall back this time of year and just 14units/ac of N are being applied to maintain grass quality and to avoid it sending up seed heads.

Farmer focus: Michael Culhane, Killaloe, Co. Clare

  • Growth: 27kg DM/ha/day
  • Demand: 45kg DM/ha/day
  • Farm cover: 1103kg DM/ha
  • Stocking rate: 5.48LU/ha
  • Days ahead: 25

With an average farm cover of 1103kg DM/ha the home block of land being measured is in a surplus of grass. The heaviest cover on the farm is not gone beyond grazing at a cover of 1800kg DM/ha which gives me additional options as to how to reduce the average farm cover on this area without compromising on grass quality in the animal’s diet.

I have a preference for pit silage over bales when it comes to labour management and ease of feeding so I aim to make as few bales as possible while keeping control of grass quality.

My grazing plan for the next couple of weeks will be to take cattle from an outside block which has a lower grass cover and graze them on the home block until the grass availability on the home block reduces. A reduction in stocking rate for the home block is then inevitable over the next month as older animals are drafted for slaughter and silage ground comes available for grazing after the second cut.

The second cut silage will be harvested later in July and if paddocks go beyond grazing in the meantime they may well be added into the second cut. The plan is to spray off the second cut before harvesting and reseed this ground to help increase the production and quality of the silage ground for the next few years. A key aspect of ensuring the success of the reseed will be getting the post emergence weed control right as outlined above.

If you liked this Growthwatch article you might like to keep up with the weekly Growthwatch articles from the Teagasc Green Acres Calf to Beef team here on Teagasc Daily. You might also like to read the second issue (June) of the Teagasc Green Acres Calf to Beef e-Newsletter here. The Teagasc Green Acres Calf to Beef e-Newsletter will issue fortnightly and you can read it here each fortnight on Teagasc Daily.

To find out more about the Green Acres Calf to Beef Programme click here https://www.teagasc.ie/animals/beef/demonstration-farms/green-acres-calf-to-beef/