Watch: how to grow greener grass

Tell us how bad we are,” a farmer said as he approached the section dealing with climate change and grassland at last Tuesday’s Teagasc open day at Johnstown Castle.

By contrast, the message from the researchers present on the day was to tell us how much better we can become.

Describing the potential to make calf-to-beef systems more profitable, Nicky Byrne said that “the key is to extend the grazing season, especially in the spring”. This includes carefully planning the winter housing of older cattle for finishing and slaughter, before younger ones move inside. This reduces housing costs and slurry storage, which in turn cuts ammonia and greenhouse gas emissions.

“By conditioning swards for the next spring, you will have better grass digestibility later,” Byrne added. This means earlier turnout dates, higher animal performance, reduced methane emissions from their rumen, smaller feed imports and lower age at slaughter – all contributing to reducing the carbon footprint of each kg of beef produced.

Low-emission slurry spreading

David Wall showed swards where 3,000gal/ac slurry had been spread with different implements at the same dates. After a month, those spread with a trailing hose or shoe had achieved growth and nutrient utilisation nearly double those with splash plates.

Heavy covers were also spread one week before the event. The trailing shoe plot could be fully grazed and the hose plot had very little contamination. “You wouldn’t do that with splash plates, you’re ruining the grass,” said Wall, showing a fully contaminated sward.

In addition, spreading slurry under the grass canopy with trailing implements protects it from the sun and wind that causes volatilisation of nitrogen into toxic ammonia gas. “On a day like today, 90% of your nitrogen goes up in smoke if applied by splash plate,” said gas emissions researcher Gary Lanigan in the baking sunshine.

Trailing hose or shoe application therefore delivers 10kg more N/ha worth €10. “1,000gal of slurry is equal to one bag of 5-5-30 if using a splash plate, but 10 to 12-5-30 if using low-emission spreading,” said Wall. However, Lanigan warned that the need for larger tractors to draw trailing implements would absorb the financial savings.

Carbon sequestration

While international research indicates that grassland can store 0.25- to -1.75t/ha of carbon, Macdara O’Neill said studies in Ireland had measured up to 2t/ha stored. This is as much carbon dioxide sucked out of the atmosphere, where it is causing global warming. Ongoing Teagasc research examines the impact of tilling on carbon soil, with min-till explored as an option for reseeding. “This may need to be reseeded after five years with deeper till – this is not settled,” said O’Neill.

Another idea would be to plough the carbon-rich top layer deep into the soil, and work with the new topsoil as an empty carbon sink ready to be filled. This is at an early research stage.

Fertilisers from waste

The EU-funded Renu2Farm project explores the conversion of waste to fertiliser across six countries, including Ireland. “The objective is that farmers can use these fertilisers cheaper and with the equipment they already have,” IT Carlow researcher Anna Karpinska said, with farmers’ needs and attitudes to waste-based fertilisers a big part of the project.

She showed trial grass plots including one fertilised with incinerated poultry litter, which gives a granulated phosphorous-rich fertiliser, free from pathogen or heavy metal contaminants. The swards will now be cut and analysed along with the soil for performance measurement and any signs of environmental damage.

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