Farmers strongly advised not to Cut Nitrogen Blindly as Fertiliser Costs Rise - AFBI Grassland Insights: From Soil to Sward

Date published: 26 March 2026

The final event in the AFBI Grassland Insights: From Soil to Sward webinar series delivered a clear and timely message for livestock farmers facing unprecedented input costs: cutting fertiliser use does not automatically reduce the cost of producing grass.

With global energy and fertiliser markets shaken by the war in Iran, farmers across Northern Ireland are understandably under pressure to try and reduce costs of production. Prices have soared and many are questioning every unit of fertiliser they spread.

However, speakers at the event — Dr Paul Cottney, senior agronomist at AFBI, and Omagh dairy farmer and UFU representative Andrew Wright — warned that slashing nitrogen without a plan can backfire, raising the cost per tonne of forage and leaving farms short of home‑grown feed.

Dr Cottney explained that every farm has an economic optimum rate of nitrogen, and aiming for this point delivers far better value than either over‑ or under‑applying. He emphasised that soil condition remains the foundation of good nutrient management, noting that “to reduce long‑term costs, farmers should aim to improve soil pH and measure field performance.” Correcting low pH offers one of the clearest returns available, and he reminded farmers that “for every pound spent on lime, it’s estimated you get seven pounds back — an incredible return on investment.”

He also highlighted how sward performance declines as they age. Perennial ryegrass yields drop as weeds and less productive grasses creep in, cutting nitrogen response and pushing up the cost of home‑grown forage. Targeted reseeding or overseeding of tired swards can restore productivity, with typical payback periods of two and a half to three years even at today’s prices. The priority, he said, is to direct nitrogen, lime and reseeding to the fields where they will make a difference.

Bringing the theory into a farm context, Andrew Wright agreed with AFBI’s message and shared how he has approached the fertiliser price shock on his own dairy unit. While the temptation to cut nitrogen sharply is strong, he warned farmers that “traditional artificial fertiliser is still the most cost‑effective way to get nutrients into your soil to grow grass. Don’t cut back on nitrogen — focus on balancing your N, P, K and S levels.”

Wright encouraged farmers to focus on the basics: soil tests, lime where needed, and nutrient applications that match crop demand. “Tackle it in small chunks and don’t be afraid of a bit of trial and error,” he said.

The session ended with a panel discussion and a clear message: don’t make blanket cuts. Instead, assess fields individually and prioritise investment where it will return the most. The panel agreed that reseeding and fertiliser will remain central to profitable grassland farming in Northern Ireland.

The event brought the Grassland Insights series to a close, showing how AFBI research and farmer experience can support confident, cost‑effective decisions in a challenging year.

You can watch all three webinar recordings here