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Farming Influence on Water Quality- Findings of the Agricultural Catchments Programme (ACP)

08 July 2020
Type Media Article

A better environment and supporting the production of high-quality food are the twin aims of the ACP. Funded by the Department of Agriculture, Food and the Marine, staff have been working with 300 farmers across six catchments in Ireland for over ten years to achieve these goals while also evaluating the Nitrates Directive regulations.

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There are six catchments covering a range of soil types (free draining, heavy, drumlin and Karst) and farming enterprises (tillage, dairy, beef and sheep). With the support and co-operation of the catchment farmers the ACP are able to monitor soils, weather, farming practice, ground water and surface water. Each catchment has a KIOSK that measures water quality and volume leaving the area every 10 minutes. There is also a weather station recording rainfall, temperature, wind etc and live weather data can be found at www.acpmet.ie. Each farm was soil tested every 2ha, every 4 years and received a detailed nutrient management plan. This allowed us to see trends in soil fertility as a result of fertiliser usage and nutrient uptake. Farmer engagement through the catchment advisor is a key part of the catchments programme.

Discussion group meeting, Kiosk and ACP advisor Kevin Madden & Cregduff farmer, Matt Shoughnessy

We also gather information on their economic performance and by building up this information over the years we learn how farming influences water quality and how the regulations impact on farming.

Key Findings of the ACP to date

There is a trend of declining soil phosphorous levels

This falling trend is not only in soils with high P index’s, but worryingly it has also occurred in less fertile fields with lower than optimum P levels.

Soil type has a greater influence on P loss than soil P level

The more poorly drained the soil the greater the risk of loss of phosphorous to water, this is mainly due to overland flow with phosphorous running off the surface.

Point sources can have a bigger impact when streams are at low flow during the summer

Recent EPA reports have highlighted a falling trend in river water quality. This is mostly a result of what is and is not living in riverbeds. An ecological standard (Q value) is assigned to a stream based on the species found by taking a “kick sample”. Slightly raised P concentrations during low flow periods are more likely to have impact on species that indicate good water quality.

Closed period for slurry spreading is effective

The continuous high resolution monitoring over the last 11 years has shown that the closed period is when there is a higher risk of nutrient loss from farmland. The closed period is effective in minimising these losses. It is important to note here that very small amounts of P will have an impact on water quality, and N spread outside the growing season is inefficient.

Extreme weather events (very wet periods such as last winter, or prolonged dry spells as in the summer of 2018) have a major influence on nutrient losses to water from farming

In the end of the summer of 2018 when it started to rain after the prolonged drought, nitrogen concentrations in the rivers increased to levels never seen before in the catchments programme. Poor grass growth and dried out soils contributed to this. In November 2014 after a very wet storm, the amount of phosphorous that usually leaves a catchment in one year left in 24 hours.