(CN) - Ireland's plan to let farmers spread more manure ran into a hard check Thursday, with a top EU court adviser warning the government can't raise limits without proving it won't pollute rivers, lakes or protected habitats.

It all turns on nitrogen. Livestock manure contains high levels of it, and when too much is spread on fields, it can seep into groundwater and run off into rivers and coastal waters, harming water quality and ecosystems by fueling algae blooms and depleting oxygen.

Under EU law, farmers can generally apply up to 170 kilograms, or about 375 pounds, of nitrogen annually per hectare, an area just under two and a half acres. Ireland, however, has long relied on a special exemption allowing some farms to go as high as 250 kilograms, or about 551 pounds, a practice tied to its grass-based dairy model.

An environmental group, An Taisce, challenged that approach, arguing the government never properly showed the higher limits were safe. Irish judges then asked the Court of Justice of the European Union whether those rules were adequately assessed under EU environmental standards, and whether they could stand if that scrutiny was missing.

Advocate General Juliane Kokott boils it down to a simple rule: Higher limits are possible, but only if countries can prove they won't harm the environment.

The opinion leans on EU water law, which requires countries to prevent any deterioration in water quality and work toward "good status" for all surface waters. The question is not what works for farmers, but whether the water can take the pressure.

Kokott sees a problem with Ireland's approach. In her view, authorities focused on safeguards written into the plan, such as annual applications for derogations, a 250-kilogram cap and nutrient management rules, without properly testing the real-world impact of allowing more nitrogen on farms.

That gap is key. It is not enough to point to protections on paper. What matters is whether, in practice, letting thousands of farms spread more manure will push water quality in the wrong direction.

The opinion also links the issue to Natura 2000, Europe's network of protected sites that depend on clean water. Any plan likely to affect them must undergo a detailed environmental assessment, and Kokott makes clear that review must look at the actual farming activity, not just the safeguards.

Ireland has defended its approach by arguing that its grass-based dairy system, with long growing seasons and high grass uptake, allows manure to be absorbed more efficiently, making higher nitrogen limits environmentally sustainable under strict conditions.

But environmental groups say the data tells a different story. An Taisce, which brought the case, says water quality has been declining for years in intensive farming regions and that successive action plans have failed to curb pollution, with no solid evidence that higher limits are actually safe.

Elaine McGoff, head of advocacy at An Taisce, welcomed the opinion as a step in the right direction and framed the issue plainly: "The objective here is simple. We want Ireland to be a country that can provide and protect clean water."

She added the opinion reinforces what the group has long argued: that proper, evidence-based assessments are missing, especially at farm and catchment level. "All the evidence indicates that they are not working adequately, as water quality is declining year on year," McGoff said.

Hendrik Schoukens, professor of environmental law at Ghent University, said the opinion sends a broader and sharper message about how EU environmental rules apply to farming. Even where Brussels has approved higher manure limits, he said, those policies still have to pass strict checks under EU water and nature laws.

In his view, the opinion makes clear that derogations are not a free pass. "Nitrate action plans and derogation do not provide a shield against actions aimed at limiting agricultural activities that generate impacts that do not allow compliance" with international law. He added that countries must properly assess those plans, including through detailed environmental reviews and monitoring, and ensure they do not undermine water quality or protected habitats in practice.

From the farming side, the Irish Farmers' Association, which took part in the case, said its legal team is "studying the judgment in full."

Ireland's Department of Agriculture, Food and the Marine did not immediately respond to a request for comment.

For now, the opinion does not settle the case. It is not binding, but it carries weight - EU judges often follow such advice when issuing their final rulings.

That judgment, expected later this year, will decide whether Ireland's current system can stand or must be reworked. If the court follows Kokott's reasoning, the implications could be significant: Dublin may need to revisit how it assesses agricultural impacts, tighten monitoring and potentially rethink how much nitrogen farms are allowed to use at all.

Courthouse News reporter Eunseo Hong is based in the Netherlands.

Source: Courthouse News Service