The concentration of nitrogen (N) and phosphorus (P) in soiled farm roadway runoff is much higher than previously expected, according a new report from the Environmental Protection Agency (EPA).

The EPA report stated that soiled roadway runoff has a similar profile to soiled dairy water and slurry in some cases.

Concentrations of P trapped in sediment on roadways surrounding fields were up to 10 times more than previously anticipated.

“This trapped phosphorus can remain stored in the ground for long periods and is released into waterways when it rains.

“This leads to year-round pollution of waterways, where it was previously thought that this pollution eased when cattle were wintering in sheds,” the report said.

The project also found that soiled waters have the highest risk of entering waterways when they drain into open ditches connected to the farmyard.

On average, there are three to four areas directly connected to water on any given farm.

Project Roadrunner

The report is based on Project Roadrunner, which partnered with Teagasc and the University of Limerick (UL) to examine farm roadway runoff and methods of nutrient-loss reduction.

Areas of the farmyard where water, soil and sediments become particularly enriched with nutrients were identified.

These include a 100m radius around the farmyard, underpasses, water troughs situated along roadways, roadway junctions or anywhere that impedes animal movement.

It was suggested that these areas be targeted in reducing soiled runoff.

The report put forward a number of ideas.

A farm roadway visual assessment booklet was developed as part of the project.

This was co-designed with stakeholders, is intended for use by farm advisers and “is a good starting point for those looking to resolve those issues”.

“This handbook aims to describe visual assessment indicators for identifying the extent of connectivity between roadway runoff and waters and helps users to examine the structure and configuration of the entire roadway network and evaluate its pollution risk potential.”

The project also trialled a low-cost diversion bar, which could be placed on roadways at a cost of €100/unit.

However, the report stated that further investigation into this diversion bar’s effectiveness is needed.