Across Northern Ireland, around 40% of farm fields already have adequate or high levels of soil phosphorus. That's a lot of farmers adding a nutrient their land doesn't need, and paying for the privilege. Yara's grassland agronomist Philip Cosgrave says it's time to look at what's actually missing.

Decades of intensive fertiliser applications, combined with phosphorus inputs through animal feed, have left many fields at or above the adequate soil phosphate index. For farmers still choosing fertiliser products that contain phosphate, that decision is worth revisiting. "There's no benefit in applying a nutrient the soil already has enough of. It costs money, and it increases the risk of phosphorus being lost into waterways," says Philip. 

The consequences are already showing up in the water. There is an excess of approximately 7,000 tonnes of phosphorus going onto Northern Irish farm each year – a figure that has contributed to the water quality problems visible in Lough Neagh and other water bodies. While fertiliser is far from the only source, farmers applying phosphate to soils that don't need it are adding to a problem that the whole sector is being asked to help solve.

The nutrient you are probably short of

Potash doesn't attract the same attention as nitrogen or phosphorus. On many Northern Irish farms, it probably should. On grassland farms it can be the biggest limiting factor on yield. 

Grass contains nearly as much potash as it does nitrogen. If you're applying 100kg of nitrogen per hectare, the crop likely needs a similar quantity of potash to match it. Every silage cut strips significant amounts of potash from the soil, and while organic manures and slurry can replace some of it, they rarely replace all of it. The result is a gradual depletion that shows up in yield figures long before it becomes obvious elsewhere. Soil analysis will tell you where potash levels currently stand, and for most farmers in Northern Ireland, those results are already there to be looked at. Reviewing those results and grouping fields with similar fertility profiles together is the starting point for a fertiliser plan that reflects what the soil actually needs. Fields sitting at phosphate Index 3 or above don't need a phosphate input, but they very likely still need potash, and that's where the yield response will come.

Not every field needs everything

Grassland nutrition comes down to four nutrients: nitrogen, phosphate, potash, and sulphur. The key is applying the ones that are actually needed, in the right amounts, based on what the soil analysis says and what the crop is being asked to produce. In practice, that means choosing the product that fits the field, not the farm as a whole.

Yara's zero-phosphate range has been developed for exactly the conditions found across much of Northern Irish farmland. For silage fields with high potash offtake, YaraMila Zero P Cut delivers higher potash levels within a zero-phosphate formulation. For grazing, YaraMila Zero P Sward is a better fit, though it can also be used on silage fields where the potash requirement is lower. Where nitrogen and sulphur are the only two nutrients required, that solution exists too.

"In most situations, we can match what's needed to one of our products," says Philip. "The point is that farmers shouldn't be paying for nutrients their soils don't require, and they shouldn't be missing out on nutrients that would actually make a difference to yield."

What the regulations require and what good agronomy requires are now the same thing

The regulatory pressure isn't going away. Northern Ireland's Nutrients Action Programme (NAP) has clear goals: reduce nutrient losses, improve balance, and protect water quality. The ambition is a farming sector where nutrient applications are driven by crop need rather than convenience or assumption.

For most farmers, it's also the logical approach. Phosphate that sits in a soil already well supplied with it doesn't grow more grass. It's an expense with no return. Redirecting that spend to the nutrients that are genuinely deficient – potash in particular – is both agronomically sound and commercially sensible.

The soil analysis is already there and the products are available. The only question is whether farmers are making fertiliser choices that reflect the actual state of their soils, or whether old habits are making that decision for them.