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Timoleague Agricultural Catchment Programme Update


Teagasc’s Agricultural Catchments Programme has been monitoring water quality in 6 locations across Ireland to investigate the impact of agriculture on water quality in these catchments. Oisín Coakley, ACP Advisor, provides an update on the 8km square Timoleague catchment here

Monitoring water qualiy

Teagasc’s Agricultural Catchments Programme (ACP) has been monitoring water quality in six locations across Ireland of contrasting soil type and farming for the past 12 years.  The purpose of the ACP programme is to investigate the impact of agriculture on water quality in these catchments.  Its principal objective is assessing the effectiveness of the measures being implemented in Ireland under the Nitrates Directive.   Water quality readings are continuously collected at the outlet-point in Timoleague at 10 minute intervals for the last 12 years. Ground-water readings are collected in a series of deep water wells located in the catchment.  Surface-water is sampled every month along with ecological analysis and identification of critical-source pathways.  All this information allows scientists to form a holistic picture of the water quality story in the catchment.

The Timoleague catchment

The Timoleague catchment is 8km² in size and stretches from Ardgehane in Barryroe to Barryshall just west of Timoleague.  It is representative of some of the most intensively farmed dairying areas in Ireland. The catchment is predominately grassland on a free-draining soil and over the course of our study an average annual rainfall of 1105mm has been recorded. Agriculturally relevant data from our Campbell scientific met station can be accessed live on our website www.acpmet.ie along with a lot more information about the ACP.

Soil type and Nitrogen retention

The Timoleague catchment feeds into the Argideen estuary and Coutmacsherry Bay has the second highest yearly average Nitrogen concentration in the programme at 6 mg / litre.  The load of organic and chemical N applied here annually to grow grass is over three times higher than that in the Castledockrell tillage catchment in Co. Wexford.  Expectations of higher nitrogen losses from more intensively stocked catchments may seem logical but actual results from the six study catchments have not followed this logic.  In fact, the catchment with the lowest amount of livestock per ha (Castledockrell in Co. Wexford) has the highest yearly average concentration of N, at 7 mg / litre.  This is a result of the free draining soil type there and the large amount of spring cereals grown.  Therefore, the many years of study have shown that the underlying soil type has a major impact on the ability of the land to retain nitrogen for grass or crop production.

Good Agricultural Practice regulations (GAP)

In 2006, the Good Agricultural Practice regulations (GAP) were introduced, bringing the European directive into law in Ireland.  This regulation aims to protect water quality from agricultural sources of pollution.  To be more specific, the directive focuses on “Nitrates” and “Eutrophication”.  Too much nitrate can make water unsafe to drink and a limit has been set at 11.3 mg N / litre, below which it is considered not to be a risk to human health. 

The GAP regulations are reviewed and changed every four years and so far, on these anniversaries, Ireland has applied for and received permission for its farmers to exceed the 170 kg N / hectare stocking rate limit set out in the directive.  

Nitrates Derogation

The scientific information collected in the 6 catchments, including Timoleague, is used to demonstrate the effectiveness of the Nitrates Derogation and to underline Ireland’s case to renew the Nitrates Derogation to farm at a stocking rate of above 170 kg/ha.   There are many factors including stocking rate that impact the concentration of nutrients in streams.  These include: land drainage; depth of the underlying water table; soil moisture deficit (how wet or dry the soil is); farm nutrient management; soil pH; chemical nitrogen and organic fertiliser application rates and timing; re-seeding; ploughing; grazing intensity; soil type and geology. All of these factors are reflected in the scientific information collected in the Timoleague and other catchments across the country.

The ACP influence on Nitrates Derogation

Ireland is required to report annually on the water quality in our rivers and streams. In addition, the Department of Agriculture, Food and the Marine and the EPA, the Agricultural Catchment Programme (ACP) contributes to this report and all the points outlined above have been included. While the ACP has very detailed scientific results from six catchments, water quality from over 1,800 catchments compiled by the EPA show declining trends since 2017. This does not help the application for derogation renewal, which takes place later this year.  If Ireland is to continue to receive permission to allow farmers exceed the 170 kg stocking rate limit, farm practice may need to be tailored to suit the local soil conditions and weather.   

The review will present changes to the Nitrates derogation for farmers across Ireland including West Cork. Spreading chemical and organic manure at the right time, rate and location will be required if we are to maintain our exemption. Decisions on where and when to spread slurry can no longer be based on tanks being full, and the driest ground available at that time.  We must make the best use of nutrients in slurry and reduce chemical applications accordingly to achieve balance. The consensus among the decision makers when it comes to legislation is that to date, this has not been achieved to a satisfactory level.  Slurry storage and ensuring that these facilities on each farm are sufficient will strongly influence the nitrates derogation continuation. It is important for farmers to assess the quantity of slurry storage in relation to the number of animals that are kept over the winter and make use of the grant aid available while also taking account of the capital allowances available on the taxation side to put additional storage in place where required. 

More on the Agricultural Catchments can be found here