Broken weather in the first half of June has stopped some farmers from harvesting high-quality, first-cut grass silage. But, in general, across much of Northern Ireland, this spring and early summer there have been plenty of opportunities to get grass ensiled and also keep productive swards ahead of livestock.

“There can be no excuse for not producing good silage and ensure grazing at the right stage in a year like this,” maintained Dr Sinclair Mayne, the chief executive of the Agri-food and Biosciences Institute (AFBI), speaking at the ‘‘More from Grass’’ event held at Loughgall this week.

Welcoming several hundred farmers to the event, Mayne described grass as our most important, but also, often our most neglected crop. To reinforce the point, the AFBI chief had three piles of grass laid out representing the average production on a NI beef and sheep farm (4.1t dry matter per hectare), the average on a NI dairy farm (7.5t) and what is possible from NI trial work (15t).

Soil analysis

He emphasised that the process of growing more grass starts with soil analysis, correcting soil pH by applying lime and adding phosphorus, potassium and sulphur, where required. On too many farms, he said that there is a significant underuse of nitrogen fertiliser, which is reflected in results from silage analysis showing protein levels typically at 13% to 14% and below, when a good quality sward should have protein levels of 18% to 19%.

Under the correct management, he maintained that an older sward dominated by perennial ryegrass still has the ability to produce 12 to 13t of grass dry matter. “Reseeding is the last thing you do. If you want the extra 2t, reseeding is the way forward. But it has a role at the end of the chain, not the start of the chain,” he said.

Nutrient status

The importance of getting soil nutrient status correct was also emphasised by AFBI scientist Dr John Bailey who pointed out that nitrogen aside, the other two nutrients most likely to limit grass yields in NI are sulphur and potassium (K).

The potassium status of soils drops very quickly in a silage situation and must be replaced by slurry and also potassium containing fertiliser.

In terms of sulphur, he said that up to 50% of NI is deficient in this nutrient, and advised that it should be routinely included in fertiliser for first cuts and also first grazing. On light soils, additional sulphur might be required. Yield losses of up to 30% can occur at first cut as a result of sulphur deficiency, said Bailey.

With no recommended list of grass and clover varieties (from AFBI Crossnacreevy) to be published in NI this year, the alternative for local farmers is to refer to the Irish list for 2017 where varieties are ranked on a pasture profit index (PPI).

The PPI assigns an economic value in €/ha for each variety against a baseline and is based on spring, summer and autumn growth, quality, persistency and silage yield. The list is currently headed by two varieties bred at Aberystwyth University in Wales, Aberclyde and Abermagic. The top ranking AFBI-bred variety is Fintona in fourth place.

However, according to Professor Jim McAdam from AFBI, the PPI list might be valuable for a dairy farmer in Cork, but it is not tailored to systems in NI where grass varieties could perform differently due to our climate.

New system

Instead, AFBI is keen to move away from grass variety evaluation using manicured plots, and produce a new system for grass variety evaluation, involving grazing studies, initially at AFBI Hillsborough, but also out on-farm. The ultimate aim is to develop a herbage value index, that will identify varieties best suited to NI conditions.

“A proposal is currently with the department (DAERA). We are working our way through the nuts and bolts of that” said McAdam.