• Chemical amendment of pig slurry: control of runoff related risks due to episodic rainfall events up to 48 h after application

      O'Flynn, Cornelius J.; Healy, Mark G.; Wilson, Paul; Hoekstra, Nyncke J.; Troy, Shane M.; Fenton, Owen; Irish Research Council for Science, Engineering and Technology (Springer, 01/09/2013)
      Losses of phosphorus (P) from soil and slurry during episodic rainfall events can contribute to eutrophication of surface water. However, chemical amendments have the potential to decrease P and suspended solids (SS) losses from land application of slurry. Current legislation attempts to avoid losses to a water body by prohibiting slurry spreading when heavy rainfall is forecast within 48 h. Therefore, in some climatic regions, slurry spreading opportunities may be limited. The current study examined the impact of three time intervals (TIs; 12, 24 and 48 h) between pig slurry application and simulated rainfall with an intensity of 11.0±0.59 mm h-1. Intact grassed soil samples, 1 m long, 0.225 m wide and 0.05 m deep, were placed in runoff boxes and pig slurry or amended pig slurry was applied to the soil surface. The amendments examined were: (1) commercial-grade liquid alum (8% Al2O3) applied at a rate of 0.88:1 [Al/total phosphorus (TP)] (2) commercial-grade liquid ferric chloride (38% FeCl3) applied at a rate of 0.89:1 [Fe/TP] and (3) commercial-grade liquid poly-aluminium chloride (10 % Al2O3) applied at a rate of 0.72:1 [Al/TP]. Results showed that an increased TI between slurry application and rainfall led to decreased P and SS losses in runoff, confirming that the prohibition of land-spreading slurry if heavy rain is forecast in the next 48 h is justified. Averaged over the three TIs, the addition of amendment reduced all types of P losses to concentrations significantly different (p<0.05) to those from unamended slurry, with no significant difference between treatments. Losses from amended slurry with a TI of 12 h were less than from unamended slurry with a TI of 48 h, indicating that chemical amendment of slurry may be more effective at ameliorating P loss in runoff than current TI-based legislation. Due to the high cost of amendments, their incorporation into existing management practices can only be justified on a targeted basis where inherent soil characteristics deem their usage suitable to receive amended slurry.
    • Exploring the relationship between groundwater geochemical factors and denitrification potentials on a dairy farm in southeast Ireland

      Fenton, Owen; Healy, Mark G.; Henry, Tiernan; Khalil, Mohammed I.; Grant, Jim; Baily, Anne; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; RSF 07 525; RSF 06 383 (Elsevier Science BV., 06/05/2011)
      Nitrate (NO3−) loss from agriculture to shallow groundwater and transferral to sensitive aquatic ecosystems is of global concern. Denitrifying bioreactor technology, where a solid carbon (C) reactive media intercepts contaminated groundwater, has been successfully used to convert NO3− to di-nitrogen (N2) gas. One of the challenges of groundwater remediation research is how to track denitrification potential spatially and temporally within reactive media and subsoil. First, using δ15N/δ18O isotopes, eight wells were divided into indicative transformational processes of ‘nitrification’ or ‘denitrification’ wells. Then, using N2/argon (Ar) ratios these wells were divided into ‘low denitrification potential’ or high denitrification potential’ categories. Secondly, using falling head tests, the saturated hydraulic conductivity (Ksat) in each well was estimated, creating two groups of ‘slow’ (0.06 m day−1) and ‘fast’ (0.13 m day−1) wells, respectively. Thirdly, two ‘low denitrification potential’ wells (one fast and one slow) with high NO3− concentration were amended with woodchip to enhance denitrification. Water samples were retrieved from all wells using a low flow syringe to avoid de-gassing and analysed for N2/Ar ratio using membrane inlet mass spectrometry. Results showed that there was good agreement between isotope and chemical (N2/Ar ratio and dissolved organic C (DOC)) and physio-chemical (dissolved oxygen, temperature, conductivity and pH) parameters. To explain the spatial and temporal distribution of NO3− and other parameters on site, the development of predictive models using the available datasets for this field site was examined for NO3−, Cl−, N2/Ar and DOC. Initial statistical analysis was directed towards the testing of the effect of woodchip amendment. The analysis was formulated as a repeated measures analysis of the factorial structure for treatment and time. Nitrate concentrations were related to Ksat and water level (p < 0.0001 and p = 0.02, respectively), but did not respond to woodchip addition (p = 0.09). This non-destructive technique allows elucidation of denitrification potential over time and could be used in denitrifying bioreactor technology to assess denitrification hotspots in reactive media, while developing a NO3− spatial and temporal predictive model for bioreactor site specific conditions.
    • Good water status: The integration of sustainable grassland production and water resources in Ireland

      Richards, Karl G.; Fenton, Owen; Khalil, Mohammed I.; Haria, Atul H.; Humphreys, James; Doody, Donnacha G.; Moles, Richard; Morgan, Ger; Jordan, Philip; Department of Agriculture, Food and the Marine, Ireland; et al. (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2009)
      The challenge for sustainable grassland production is to integrate economically profitable farming systems with environmental protection. The Water Framework Directive aims to attain at least “good status” for all waters by 2015, to be achieved through the introduction of measures across all sectors of society. Historically, the impact of grassland agriculture on water quality was investigated in isolation. More recently it has been highlighted that water quality and other environmental impacts such as greenhouse gas emissions must be considered in an integrated manner. Catchment hydrology is critical to understanding the drivers behind nutrient transport to surface water and groundwaters. Flashy catchments are more susceptible to phosphorus, sediment and ammonium loss, whereas contrastingly baseflow dominated catchments are more susceptible to nitrate transport. Understanding catchment hydrology enables the targeting of measures for the mitigation of diffuse agricultural contaminants. This increased understanding can also be used to support extended deadlines for the achievement of good status. This paper reviews the potential effects of grassland agriculture on water quantity and the transport of pesticides and nutrients to water in the context of achieving good status for all waters by 2015 under the Water Framework Directive.
    • Lough Melvin: Developing cost-effective measures to prevent phosphorus enrichment of a unique aquatic habitat

      Schulte, Rogier P.; Doody, Donnacha G.; Byrne, Paul; Cockerill, C.; Carton, Owen T.; Lough Melvin Nutrient Reduction Programme (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2009)
      Lough Melvin, located on the border of Leitrim (Republic of Ireland) and Fermanagh (Northern Ireland), is unique among Irish lakes, supporting a fish community typical of a natural post-glacial salmonid lake, and has been designated as a Special Area of Conservation (SAC). The biodiversity of the lake is vulnerable to changes in water quality resulting from eutrophication, and over the last 15 years, phosphorus (P) concentrations have increased to the upper range of mesotrophic classification. Agriculture has been reported as one of the main contributors of P loadings to the lake, which poses an apparent paradox in light of the low-intensity nature of farming practices in the catchment. The objectives of the project reported on here were to identify the dominant P pressure and pathway risks governing P loss in the catchment, and to evaluate and select potential mitigation measures, based on an assessment of cost-effectiveness and farmer preference. Throughout this project, we employed an explicitly participatory approach, with farmer stakeholders inputting directly into the identification and evaluation of mitigation measures. We identified risks on 50 survey farms by using the modified P Ranking Scheme. A suite of 25 potential mitigation strategies was identified from the literature and on-farm interviews. For each measure, we derived the order of magnitude of potential costs, impact, and cost-effectiveness, and measures were preferentially ranked by 25 participating farmers. The resulting ranking of measures showed that support for nutrient management planning and soil analysis was the most cost-effective and popular measure aimed at reducing P pressures in the long term, while installation of sediment traps in drainage ditches was the most cost-effective and popular measure aimed at reducing P transport vectors in the short term. We demonstrate that through this careful evaluation and selection of mitigation measures, over 50% of potential total reduction in P loss can be achieved at c. 5% of potential total cost. In addition, we show that measures commonly proposed to mitigate against “high-visibility risks” are not necessarily cost-effective or acceptable to farmer stakeholders. The results of this study are specific to the biophysical environment and farming context of the Lough Melvin catchment, however, we suggest that the approach taken in our project may be used as a template for the formulation of regional catchment management plans, such as the draft river basin district management plans required under the Water Framework Directive.
    • Mobilisation or dilution? Nitrate response of karst springs to high rainfall events

      Huebsch, Manuela; Fenton, Owen; Horan, Brendan; Hennessy, Deirdre; Richards, Karl G.; Jordan, Philip; Goldscheider, N.; Butscher, C.; Blum, P.; Teagasc Walsh Fellowship Programme (European Geosciences Union, 05/11/2014)
      Nitrate (NO3−) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e. rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in South Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and on the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU) Water Framework Directive (WFD). In future, more research should focus on the high-resolution monitoring of karst aquifers to capture the high variability of hydrochemical processes, which occur at time intervals of hours to days.
    • A review of remediation and control systems for the treatment of agricultural waste water in Ireland to satisfy the requirements of the water framework directive

      Fenton, Owen; Healy, Mark G.; Schulte, Rogier P. (Royal Irish Academy, 28/08/2008)
      In Ireland agricultural activities have been identified as major sources of nutrient input to receiving waters, and it has been estimated that these activities contribute 75.3% of the N and 33.4% of the P found in these waters. The strategy at European level focuses on the prevention of nutrient loss by improved farm management. However, it does not focus on nutrient remediation or incidental nutrient loss from farmyard manures to surface water and groundwater. This review describes the impact of agriculture on the environment in Ireland and examines emerging technologies for agricultural waste-water treatment. An integrated approach at pretreatment and field stages for nitrate (NO3) remediation and P control is recommended.
    • Surface and Groundwater Interactions: Location of a sub-surface remediation trench

      Fenton, Owen (Teagasc, 01/12/2006)
      The Water Framework Directive aims to achieve at least “good status” of all surface and groundwater bodies by 2015. In 2009 programmes of measures to achieve this status must be implemented. In 2012 water quality response to these measures will be examined at river basin catchment level. The adoption of the Water Framework Directive from the 1st January 2007 restricts the amount of nutrients which can be applied to agricultural land. A nutrient discharge to a waterbody has a negative impact on the environment and may lead to eutrophication. A broad strategy exists at European level to minimise nutrient loss to a waterbody. This strategy examines the source/pressure, pathway and receptor approach for nutrient transport. Such nutrient management strategies try to minimise nutrient loss while maintaining productivity. Nitrogen usage is now associated with environmental degradation even at lower levels than the maximum allowable concentration (11.3 mg NO3-N L-1). A further strategy proposes that nutrient management and increased utilisation of nutrients alone will fail to recognise nutrient loss even at high levels of efficiency. This strategy attempts to use remediation (Nitrate) and control technologies (Phosphorous) to intercept nutrients before discharge. Another function would be to further reduce concentrations presently at allowable levels. This introduces an interceptor phase into the nutrient transfer model.
    • Sustainable grassland systems in Europe and the EU Water Framework Directive

      Tunney, Hubert; Watson, C. J.; Kronvang, B.; Stamm, C.; Vertes, F.; Richards, Karl G.; Gibson, Mark; Fenton, Owen; Schulte, Rogier P. (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2009)
      The International Conference on ‘Sustainable grassland systems in Europe and the EU Water Framework Directive’ took place at Teagasc, Johnstown Castle, Wexford from 12th to 14th November 2008. There were approximately 150 participants from Europe, the USA and New Zealand. Most of the invited papers are published in this conference issue. The main aim of the Conference was to identify the challenges that the Water Framework Directive (WFD) presents for grassland agriculture and to help guide the implementation of cost effective mitigation measures. The Conference focused on nutrient (mainly nitrogen and phosphorus) loss from grassland and the implications for sustainable production and water quality. This paper summarises the main points and outcomes of discussions and recommendations from the Conference. It was concluded that it is difficult to link the management practices on individual fields or farms with the effects on water quality and ecological conditions in surface waters at the catchment-scale. There is a need to identify areas of highest risk of nutrient loss from point and diffuse sources to a waterbody of vulnerable status and then to focus mitigation measures in the critical source areas, where there is the greatest risk to water quality. Participants agreed that there can be a substantial lag time between the implementation of measures and improvements in water quality. A participatory approach at local level, with personal contact, is considered more productive for securing a positive response to adopting measures. Concerns were expressed that maps and models may be misinterpreted. It was recommended that estimates of accuracy should always be shown when presenting map data and modelled results. Success stories in reducing nutrient loss to water were reported and examples from Denmark and Switzerland were outlined. There is no consensus about the most important mitigation options; they will vary for different situations. The effective implementation of the Nitrates and Urban Waste Water Directives should go a long way towards meeting farming obligations under the WFD. The need for adaptive integrated management was recognised. How mitigation measures can be compared across a wide range of agricultural systems in several EU states, has not yet been explored and to achieve this, further cooperation on the most appropriate options is needed. Similarities and differences between the situation in New Zealand and the USA compared to the EU were also presented and discussed.
    • Time lag: a methodology for the estimation of vertical and horizontal travel and flushing timescales to nitrate threshold concentrations in Irish aquifers

      Fenton, Owen; Schulte, Rogier P.; Jordan, Philip; Lalor, Stanley T. J.; Richards, Karl G.; Department of Environment, Heritage and Local Government; RPS Group Ltd (Elsevier Science Ltd., 02/04/2011)
      The Water Framework Directive (WFD) in Europe aims, inter alia, to achieve at least “good” water quality status by 2015 by mitigating the causes of pollution. However, with the implementation of programmes of measures in 2012, many catchments may not achieve good water quality status within this timeframe due to the time lag of nutrient transport from source to receptor via hydrological and hydrogeological pathways. An appraisal of catchment time lag issues offers a more realistic scientifically based timescale for expected water quality improvements in response to mitigation measures implemented under the WFD. A simplified methodology for the calculation of nitrate time lag in a variety of Irish hydrogeological scenarios is presented, based on unsaturated vertical and aquifer flushing times required to reach environmental quality standards. Horizontal travel time is estimated for first occurrence of nutrients in a surface water body. The results show that achievement of good water quality status in the Republic of Ireland for some waterbodies may be too optimistic within the current timeframe of 2015 targets but improvements are predicted within subsequent 6 and 12 year cycles.
    • Variations in travel time for N loading to groundwaters in four case studies in Ireland:Implications for policy makers and regulators

      Fenton, Owen; Coxon, Catherine E.; Haria, Atul H.; Horan, Brendan; Humphreys, James; Johnston, Paul; Murphy, Paul N. C.; Necpalova, Magdalena; Premrov, Alina; Richards, Karl G. (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2009)
      Mitigation measures to protect waterbodies must be implemented by 2012 to meet the requirements of the EU Water Framework Directive. The efficacy of these measures will be assessed in 2015. Whilst diffuse N pathways between source and receptor are generally long and complex, EU legislation does not account for differences in hydrological travel time distributions that may result in different water quality response times. The “lag time” between introducing mitigation measures and first improvements in water quality is likely to be different in different catchments; a process that should be considered by policy makers and catchment managers. Many examples of travel time variations have been quoted in the literature but no Irish specific examples are available. Lag times based on initial nutrient breakthrough at four contrasting sites were estimated to a receptor 500 m away from a source. Vertical travel times were estimated using a combination of depth of infiltration calculations based on effective rainfall and subsoil physical parameters and existing hydrological tracer data. Horizontal travel times were estimated using a combination of Darcian linear velocity calculations and existing tracer migration data. Total travel times, assuming no biogeochemical processes, ranged from months to decades between the contrasting sites; the shortest times occurred under thin soil/subsoil on karst limestone and the longest times through thick low permeability soils/subsoils over poorly productive aquifers. Policy makers should consider hydrological lag times when assessing the efficacy of mitigation measures introduced under the Water Framework Directive. This lag time reflects complete flushing of a particular nutrient from source to receptor. Further research is required to assess the potential mitigation of nitrate through denitrification along the pathway from source to receptor.