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Reseeding with climate-smart varieties: production and environmental benefits

With Teagasc recently announcing an updated Marginal Abatement Cost Curve, outlining how Irish agriculture can reduce greenhouse gas (GHG) emissions by 25 per cent from 2023 to 2030, there is more pressure than ever on farmers. But there are highly productive, climate-smart grass and forage varieties that can make the difference in your autumn reseeding plans, grassland expert Dr Mary McEvoy of Germinal explains

Grazed grass is the most important component of livestock diets, so will have a major impact on the carbon footprint of milk and meat production. Building homegrown feed systems around climate-smart grass and forage varieties will ensure farmers are productive while reducing greenhouse gas (GHG) emissions. By helping to drive efficient food production, these grass and forage varieties lower the carbon footprint and production costs of milk or meat by reducing the need for inputs. There are sustainable forage options that can improve soil structure and fertility while better tolerating the climate challenges in our changing environment.

Using clovers to reduce applied nitrogen

Red and white clover deliver homegrown forage, which is highly digestible, high in protein, and drives meat and milk production. Clover’s nitrogen (N)-fixing ability is a fundamental strength – with input costs rising compared to years gone by, clover provides a nitrogen source for swards once established, reducing the dependency on artificial N, and resulting in lower nitrous oxide emissions.
Clover has been specifically highlighted among the recommended MACC measures for its ability to fix free N from the atmosphere in your soils. Increased use of red and white clover has the potential to reduce fertiliser use to 285,727 tonnes of N by 2030. Grazed grass-clover swards can achieve high levels of intake and increase animal performance compared to grass-only swards, making it both financially and environmentally sound.

The power of multi-species

Multi-species mixtures bring the benefit of superior sward performance through complementary plant species providing high-quality livestock feed throughout the summer. The performance of multi-species swards during dry periods has received particular attention as the benefits of including a variety of species with diverse root structures have been realised. Different species will also bring the benefits of improving soil structure and fertility and increasing biodiversity, while including legumes will reduce the requirement for artificial nitrogen. The incorporation of clovers and multi-species swards has been highlighted as one of the most cost-effective and impactful measures in the MACC measures for reducing nitrous oxide emissions.

Reducing emissions with high sugar grasses

Germinal’s Aber High Sugar Grasses (Aber HSG), according to Dr McEvoy, bring significant production gains, with research quantifying a 6 per cent increase in milk production and a 20 per cent increase in liveweight for beef and sheep. Used at scale, Aber HSG are also scientifically proven to reduce emissions from livestock,” she adds. The high water-soluble carbohydrate content (sugars) feeds microbes in the rumen, resulting in more of the plant protein being converted into amino acids, which are the building blocks of meat and milk. With more efficient protein use, less is wasted in urine and faeces and GHG emissions of ammonia and nitrous oxide are reduced. High sugar grasses represent another valuable measure for farmers seeking to be productive and sustainable.

The impact of multi-species on beef finishing

The MACC also highlights a significant potential to reduce agricultural emissions by achieving a high level of adoption of protected urea, the Economic Breeding Index (EBI) and reduced age to finish. Additionally, there is potential for feed additives that inhibit methane production to have a significant role in the future. After supporting multi-species research at University College Dublin (UCD), we saw in the grazing trials that steers were achieving an average growth of 80kg more than steers grazed on grass only over two years. The research also found that multi-species silage outperformed perennial ryegrass silage. Livestock fed indoors over the winter period achieved an average daily liveweight gain (DLG) of 0.89kg, representing a 39 per cent increase compared with 0.64kg DLG for stock fed on perennial ryegrass silage.

Autumn reseeding advice

With all that in mind, it’s important to revisit reseeding best practices as autumn approaches. Timing is important with autumn reseeding. Earlier sown seed will benefit from warmer soil conditions, giving quicker germination and establishment. This means spraying off by mid-August and having your seed sown by the first week of September, but the earlier the better. Any delay can risk germination being harmed by worsening weather conditions and reduce the ability of the plant to withstand pest burdens.

Soil fertility: Before taking any action, it’s important to perform a soil test to determine your requirements. For an effective reseed, especially when establishing clover, target a pH of 6.2-6.5 and phosphorus (P) and potassium (K). Having optimal soil fertility will ensure that vital nutrients are available to grasses and clovers.

Sowing methods: Ploughing can help correct soil compaction and achieves reliable results. However, farmers in derogation cannot plough grassland after May 31. So, the alternative options of min-till or direct-drilling must be considered by those farmers for an autumn reseed. Min-till is a light cultivation method that creates effective seed-to-soil contact. Achieved via discing and one-pass, min-till is well suited to rocky soils but allow up to three weeks after spraying off your old sward for weeds to break down and sods to break up. You should remove the trash 10 days post-spraying and, subsequently, apply lime to break down your decaying sward. A second option is direct-drilling and you can start by spraying off your old sward before cutting tightly and liming. You can use a tine harrow to remove thatch and maximise seed-to-soil contact. A broken forecast will ensure you have enough moisture and rolling post-sowing will further improve contact. Applying a fertiliser compound with P and K is recommended at sowing, as they are essential nutrients for root and tiller development. All chemical fertilisers must be applied prior to September 15.

Pest and weed control: By preparing your seedbed properly with the advice above, you can reduce the risk of pests and weeds damaging your reseed. Post-emergence weed control is an important aspect of reseeding. For grass-clover swards, ensure you use a clover-safe herbicide. There is no option for post-sowing weed control in multi-species swards.

First grazing: You should aim for first grazing once plants withstand the pull test, assuming ground conditions allow. Grazing is essential to help tiller out the sward and increase sward density.

Mixture options for autumn reseeding

When reseeding in autumn, it makes more sense to focus on grass and clover mixtures, with multi-species establishing better if sown in spring, as determined in trials by Germinal Horizon, our research and innovation division. Reseeding with a grass and clover mixture will ensure that you’re combining production with sustainability benefits that align with MACC.