• 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.
    • Visual drainage assessment: A standardised visual soil assessment method for use in land drainage design in Ireland

      Tuohy, Patrick; Humphreys, James; Holden, Nicholas M.; O'Loughlin, James; Reidy, Brian; Fenton, Owen (Teagasc (Agriculture and Food Development Authority), Ireland, 20/08/2016)
      The implementation of site-specific land drainage system designs is usually disregarded by landowners in favour of locally established ‘standard practice’ land drainage designs. This is due to a number of factors such as a limited understanding of soil–water interactions, lack of facilities for the measurement of soil’s physical or hydrological parameters and perceived time wastage and high costs. Hence there is a need for a site-specific drainage system design methodology that does not rely on inaccessible, time-consuming and/or expensive measurements of soil physical or hydrological properties. This requires a standardised process for deciphering the drainage characteristics of a given soil in the field. As an initial step, a new visual soil assessment method, referred to as visual drainage assessment (VDA), is presented whereby an approximation of the permeability of specific soil horizons is made using seven indicators (water seepage, pan layers, texture, porosity, consistence, stone content and root development) to provide a basis for the design of a site-specific drainage system. Across six poorly drained sites (1.3 ha to 2.6 ha in size) in south-west Ireland a VDA-based design was compared with (i) an ideal design (utilising soil physical measurements to elucidate soil hydraulic parameters) and (ii) a standard design (0.8 m deep drains at a 15 m spacing) by model estimate of water table control and rainfall recharge/drain discharge capacity. The VDA method, unlike standard design equivalents, provided a good approximation of an ideal (from measured hydrological properties) design and prescribed an equivalent land drainage system in the field. Mean modelled rainfall recharge/drain discharge capacity for the VDA (13.3 mm/day) and ideal (12.0 mm/day) designs were significantly higher (P < 0.001, s.e. 1.42 mm/day) than for the standard designs (0.5 mm/day), when assuming a design minimum water table depth of 0.45 m.
    • What Does Life-Cycle Assessment of agricultural products need for more meaningful inclusion of biodiversity?

      Teillard, Felix; Maia de Souza, Danielle; Thoma, Greg; Gerber, Pierre J.; Finn, John (Wiley, 05/06/2016)
      1.Decision-makers increasingly use life-cycle assessment (LCA) as a tool to measure the environmental sustainability of products. LCA is of particular importance in globalized agricultural supply chains, which have environmental effects in multiple and spatially dispersed locations. 2.Incorporation of impacts on biodiversity that arise from agricultural production systems into environmental assessment methods is an emerging area of work in LCA, and current approaches have limitations, including the need for (i) improved assessment of impacts to biodiversity associated with agricultural production, (ii) inclusion of new biodiversity indicators (e.g. conservation value, functional diversity, ecosystem services) and (iii) inclusion of previously unaccounted modelling variables that go beyond land-use impacts (e.g. climate change, water and soil quality). 3.Synthesis and applications. Ecological models and understanding can contribute to address the limitations of current life-cycle assessment (LCA) methods in agricultural production systems and to make them more ecologically relevant. This will be necessary to ensure that biodiversity is not neglected in decision-making that relies on LCA.
    • What does Life-Cycle Assessment of agricultural products need for more meaningful inclusion of biodiversity?

      Teillard, Félix; Maia de Souza, Danielle; Thoma, Greg; Gerber, Pierre J.; Finn, John A. (Wiley, 2016-06-05)
      Decision‐makers increasingly use life‐cycle assessment (LCA) as a tool to measure the environmental sustainability of products. LCA is of particular importance in globalized agricultural supply chains, which have environmental effects in multiple and spatially dispersed locations. Incorporation of impacts on biodiversity that arise from agricultural production systems into environmental assessment methods is an emerging area of work in LCA, and current approaches have limitations, including the need for (i) improved assessment of impacts to biodiversity associated with agricultural production, (ii) inclusion of new biodiversity indicators (e.g. conservation value, functional diversity, ecosystem services) and (iii) inclusion of previously unaccounted modelling variables that go beyond land‐use impacts (e.g. climate change, water and soil quality). Synthesis and applications. Ecological models and understanding can contribute to address the limitations of current life‐cycle assessment (LCA) methods in agricultural production systems and to make them more ecologically relevant. This will be necessary to ensure that biodiversity is not neglected in decision‐making that relies on LCA.
    • Yield of temperate forage grassland species is either largely resistant or resilient to experimental summer drought

      Hofer, Daniel; Suter, Matthias; Haughey, Eamon; Finn, John; Hoekstra, Nyncke J.; Buchmann, Nina; Luscher, A.; European Union; 266018 (Wiley, 17/06/2016)
      1.Due to climate change, an increasing frequency and severity of drought events are expected to impair grassland productivity, particularly of intensively managed temperate grasslands. 2.To assess drought impacts, a common field experiment to manipulate precipitation was set up at three sites (two Swiss and one Irish) using monocultures and mixtures with two and four key forage species. Species differed in their functional traits: a shallow-rooted non-legume (Lolium perenne L.), a deep-rooted non-legume (Cichorium intybus L.), a shallow-rooted legume (Trifolium repens L.) and a deep-rooted legume (Trifolium pratense L.). A 9-week summer drought was simulated, and soil water status, above-ground biomass yield and plant nitrogen (N) limitation were compared to a rainfed control. 3.Based on soil water measurements, the drought induced severe stress at both Swiss sites and extreme stress at the Irish site. Under severe stress, the legumes were more drought resistant and showed an average change in above-ground biomass (CAB, compared to rainfed control) of only −8% and −24% (for the two Swiss sites), while the non-legumes had an average CAB of −51% and −68%. The lower resistance of non-legumes coincided with an apparent limitation of plant N, which further increased under drought. Under extreme drought (Irish site), growth nearly ceased with an average CAB of −85%. 4.During a 6-week post-drought period with adequate water supply (Swiss sites), formerly drought-stressed species were highly resilient and either attained (legumes) or clearly outperformed (non-legumes) the yield level of the rainfed controls. This outperformance coincided with post-drought reductions in N limitation in formerly drought-stressed species. As a result, aggregated over the drought and the post-drought periods, a negative drought impact was found only for the shallow-rooted L. perenne at one of the severely stressed sites. 5.Significant overyielding by multispecies mixtures was evident under rainfed control conditions (+38% across all three sites, P < 0·05) and was equally apparent under severe drought (+50%, P < 0·05). This overyielding was greatest in mixtures with approximately equal species proportions and was sufficiently large that drought-stressed mixtures at least attained the same yield as the average of the rainfed monocultures. Under extreme drought, growth almost ceased in monocultures and mixtures. 6.Synthesis and applications. Yields of selected species of intensively managed temperate grasslands are either resistant to a single severe drought or are highly resilient as soon as soil moisture levels recover after the drought event. However, these forage species seem unable to cope with an extreme drought event. Combining species in mixtures can compensate for yield reductions caused by severe drought and it offers a practical management tool to adapt forage production to climate change.