Dr. Ciara Beausang:

My research looked at the sustainability of grass silage. That study looked at making more silage available by using additional nitrogen fertiliser. In that way, we had a surplus of grass silage and did not compete with forage for livestock. The main environmental burden comes from that additional fertiliser. It arises from the production of the fertiliser and the emissions from nitrous oxide when it is spread on the land. That is the main point of concern when grass silage is produced in that way. My study identified that as a potential risk.

There have been developments in the area since then. It is acknowledged that we will not produce that additional grass silage with additional inorganic fertiliser. It needs to be done in a more appropriate way. There are a number of ways to do it. The first is looking at different sward types. The research by Teagasc has been mentioned already. Looking at incorporating other plants with perennial rye grass, the likes of red and white clover, is a good way of increasing the yield without any inorganic nitrogen fertiliser. That way we are maintaining a surplus of grass and not competing with livestock production.

The other possibility which has good potential is to improve grass utilisation on farms. That involves improving the amount of grass ingested by cattle per the amount of grass grow. It has been shown that utilisation rates on some farms, particularly beef farms, are lower than what could be expected by research standards. If we were able to improve the utilisation rate by cattle, it would decrease the requirement for grassland and increase the available resource for alternative applications. In that way, we would free up more grass silage for additional use without inorganic nitrogen fertiliser.