• Gain in Nitrogen Yield from Grass-Legume Mixtures is Robust Over a Wide Range of Legume Proportions and Environmental Conditions

      Suter, Matthias; Finn, John; Connolly, John; Loges, Ralph; Lüscher, Andreas (Elsevier, 2015-12-31)
      Global food security is currently challenged and requires sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N) and increased protein self-sufficiency through home-grown crops. Such challenges were addressed in a continental-scale field experiment conducted over three years, in which the amount of total nitrogen yield (Ntot) and the gain in N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four-species grass-legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2 fixing legumes and two non-fixing grasses. The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all three years. Ntot and thus Ngainmix increased with increasing legume proportion up to one third of legumes. With higher percentages of legumes, Ntot and Ngainmix did not further increase. Thus, across sites and years, mixtures with one third proportion of legumes had 57% higher Ntot than grass monocultures and attained ∼95% of the maximum Ntot acquired by any stand. The relative N gain in mixture (Ngainmix/Ntotmix) was most severely impaired by minimum site temperature (R = 0.64, P = 0.010). Nevertheless, Ngainmix/Ntotmix was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass-legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels. We conclude that higher N output (Ntot or forage protein per unit area) can be achieved with grass-legume mixtures than with pure grass alone for a given amount of N fertilizer applied; conversely, the same N output can be achieved by mixed swards with less input of N. Therefore, the use of grass-legume mixtures can substantially contribute to resource-efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and greenhouse gas emissions.
    • 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.
    • Grassland vegetation from three conservation measures

      O hUallachain, Daire; Finn, John; Keogh, Blathnaid; Finch, Rochelle; Sheridan, Helen; Teagasc Walsh Fellowship Programme (Teagasc, 2017)
      Semi-natural grassland habitats have declined significantly throughout Europe. To halt the decline, grassland conservation measures have been included in most European agri-environment schemes. This is the first study to compare the botanical composition of grassland habitats managed under the Irish Agri Environment Options Scheme (AEOS). Sixty fields on dry stock pastoral farms in receipt of agri-environment payments for grassland conservation were surveyed, with twenty fields being enrolled in each of the following AEOS options: Traditional Hay Meadow (THM), Species Rich Grassland (SRG) and Natura 2000 species rich grassland (Natura). The vegetation quality of sites enrolled in the Natura measure was higher than those enrolled in the THM and SRG measures. Natura sites had the greatest species richness with a mean > 40 species per site, which included approximately 17 species indicative of high botanical quality. Traditional Hay Meadow sites had the lowest species richness (mean 29 species per site) and were dominated by species associated with improved grassland. Some THM sites had good levels of botanical richness and were similar in composition to Natura sites, with some Natura sites having a lower vegetation quality, more similar to that of THM sites. Species Rich Grassland had a botanical richness that was intermediate between THM and Natura sites. A thorough assessment of the effectiveness of these measures was confounded by a lack of quantitative objectives for the target community composition to be attained. We discuss limitations and potential opportunities regarding the design, targeting, implementation and cost-effectiveness of these agri-environment measures.
    • Gross nitrogen transformations in grassland soil react differently to urea stabilisers under laboratory and field conditions

      Harty, Mary A.; McGeough, K. L.; Carolan, Rachael; Muller, Christoph; Laughlin, Ronald J.; Lanigan, Gary; Richards, Karl G.; Watson, C. J.; Department of Agriculture, Food and the Marine, Ireland; Department of Agriculture, Environment and Rural Affairs, Northern Ireland; et al. (Elsevier, 10/02/2017)
      A laboratory and a field study were conducted on a permanent grassland soil in Northern Ireland to investigate the effects of urea in combination with N process inhibitors such as the urease inhibitor N-(butyl) thiophosphoric triamide (NBPT) and/or the nitrification inhibitor dicyandiamide (DCD) on soil N dynamics. Urea enriched with n-butyl 15N to 60 atom % was applied to soil at a rate of 100 μg N g−1 dry soil in the laboratory and 100 kg N ha−1 in the field. A numerical 15N tracing model was used to quantify several simultaneously occurring gross N transformation rates in both studies. The changes in soil nitrate (NO3−) and ammonium (NH4+) concentrations and 15N enrichment over a 25-day period as well as the concentration and 15N enrichment of plant N at harvest were used to model soil gross N transformations. The results showed that the effect of N process inhibitors varied firstly between laboratory and field studies and secondly whether the inhibitors were applied individually or in combination. Overall DCD had a greater effect on the major soil N transformations than NBPT; reducing oxidation of NH4+, total nitrification, net NO3− produced, total mineralisation and the net adsorption of NH4+ at both laboratory and field scale. The effect of DCD was similar for these transformations whether applied alone or co-applied with NBPT. In contrast NBPT had no significant effect on oxidation of NH4+, total nitrification, total mineralisation or total immobilisation compared to urea in the field, while the effect on these transformations in the laboratory was significant. The contrasting effects of inhibitors on gross N transformations between laboratory and field may relate to the differences in experimental conditions, e.g. soil preparation, environmental conditions and the contribution of plant biomass. To obtain a more realistic assessment of gross soil N transformations in situ, it is essential that laboratory experiments are supplemented with field studies.
    • Groundwater nitrate reduction versus dissolved gas production: A tale of two catchments

      McAleer, E.B.; Coxon, Catherine E.; Richards, Karl G.; Jahangir, Mohammad M. R.; Grant, Jim; Mellander, Per-Erik; Teagasc Walsh Fellowship Programme (Elsevier, 20/02/2017)
      At the catchment scale, a complex mosaic of environmental, hydrogeological and physicochemical characteristics combine to regulate the distribution of groundwater and stream nitrate (NO3−). The efficiency of NO3− removal (via denitrification) versus the ratio of accumulated reaction products, dinitrogen (excess N2) & nitrous oxide (N2O), remains poorly understood. Groundwater was investigated in two well drained agricultural catchments (10 km2) in Ireland with contrasting subsurface lithologies (sandstone vs. slate) and landuse. Denitrification capacity was assessed by measuring concentration and distribution patterns of nitrogen (N) species, aquifer hydrogeochemistry, stable isotope signatures and aquifer hydraulic properties. A hierarchy of scale whereby physical factors including agronomy, water table elevation and permeability determined the hydrogeochemical signature of the aquifers was observed. This hydrogeochemical signature acted as the dominant control on denitrification reaction progress. High permeability, aerobic conditions and a lack of bacterial energy sources in the slate catchment resulted in low denitrification reaction progress (0–32%), high NO3− and comparatively low N2O emission factors (EF5g1). In the sandstone catchment denitrification progress ranged from 4 to 94% and was highly dependent on permeability, water table elevation, dissolved oxygen concentration solid phase bacterial energy sources. Denitrification of NO3 − to N2 occurred in anaerobic conditions, while at intermediate dissolved oxygen; N2O was the dominant reaction product. EF5g1 (mean: 0.0018) in the denitrifying sandstone catchment was 32% less than the IPCC default. The denitrification observations across catchments were supported by stable isotope signatures. Stream NO3− occurrence was 32% lower in the sandstone catchment even though N loading was substantially higher than the slate catchment.
    • Groundwater: A pathway for terrestrial C and N losses and indirect greenhouse gas emissions

      Jahangir, Mohammad M. R.; Johnston, Paul; Khalil, Mohammed I.; Hennessy, Deirdre; Humphreys, James; Fenton, Owen; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; Department of Civil, Structural and Environmental Engineering, Trinity College Dublin; RSF 06383 (Elsevier, 16/07/2012)
      Estimating losses of dissolved carbon (C) and nitrogen (N) via groundwater in an agricultural system provides insights into reducing uncertainties in the terrestrial C and N balances. In addition, quantification of dissolved nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) in groundwaters beneath agricultural systems is important for global greenhouse gas (GHG) budgets. Dissolved C (DC: dissolved organic carbon (DOC) + CO2-C + CH4-C) and dissolved nitrogen (DN: NO3−-N + NH4+ + NO2−-N + N2O-N + N2) in groundwater were measured in two low permeability (<0.02 m d−1) and two high permeability (>0.05 m d−1) aquifers in Ireland. Groundwater in multilevel piezometers was sampled monthly over two years. Mean groundwater discharge to surface water was higher in 2009 (587–836 mm) than in 2010 (326–385 mm). Dissolved C and N delivery to surface water via groundwater caused substantial losses of terrestrial C and N. The extent of delivery was site specific and depended on N input, recharge and aquifer permeability. Mean dissolved N losses ranged from 8–12% of N input in low permeability to 27–38% in high permeability aquifers. The dominant fraction of DN was NO3−-N (84–90% of DN) in high permeability aquifers and N2 (46–77% of DN) in low permeability aquifers. Indirect N2O emissions via groundwater denitrification accounted for 0.03–0.12% of N input, which was equivalent to 3–11% of total N2O emissions. Dissolved C loss to surface waters via groundwater was not significant compared to total carbon (TC) content of the topsoil (0.06–0.18% of TC). Site characteristics contributed greatly to the distribution of N between NO3−-N and dissolved N gases, N2O and N2. Indirect GHG emissions from groundwater were an important part of farm nutrient budgets, which clearly has implications for national GHG inventories.
    • High-Resolution Denitrification Kinetics in Pasture Soils Link N2O Emissions to pH, and Denitrification to C Mineralization

      Samad, Sainur; Bakken, Lars R.; Nadeem, Shahid; Clough, Timothy J.; de Klein, Cecile A.M.; Richards, Karl G.; Lanigan, Gary; Morales, Sergio E.; New Zealand Fund for Global Partnerships in Livestock Emissions Research; 16084 (PLOS, 18/03/2016)
      Denitrification in pasture soils is mediated by microbial and physicochemical processes leading to nitrogen loss through the emission of N2O and N2. It is known that N2O reduction to N2 is impaired by low soil pH yet controversy remains as inconsistent use of soil pH measurement methods by researchers, and differences in analytical methods between studies, undermine direct comparison of results. In addition, the link between denitrification and N2O emissions in response to carbon (C) mineralization and pH in different pasture soils is still not well described. We hypothesized that potential denitrification rate and aerobic respiration rate would be positively associated with soils. This relationship was predicted to be more robust when a high resolution analysis is performed as opposed to a single time point comparison. We tested this by characterizing 13 different temperate pasture soils from northern and southern hemispheres sites (Ireland and New Zealand) using a fully automated-high-resolution GC detection system that allowed us to detect a wide range of gas emissions simultaneously. We also compared the impact of using different extractants for determining pH on our conclusions. In all pH measurements, soil pH was strongly and negatively associated with both N2O production index (IN2O) and N2O/(N2O+N2) product ratio. Furthermore, emission kinetics across all soils revealed that the denitrification rates under anoxic conditions (NO+N2O+N2 μmol N/h/vial) were significantly associated with C mineralization (CO2 μmol/h/vial) measured both under oxic (r2 = 0.62, p = 0.0015) and anoxic (r2 = 0.89, p<0.0001) conditions.
    • Hydrogeochemical controls on the occurrence of nitrate in groundwater

      Jahangir, Mohammad M. R.; Johnston, Paul; Richards, Karl G. (International Association of Hydrogeologists (Irish Group), 15/04/2014)
    • An Immortalized Genetic Mapping Population for Perennial Ryegrass: A Resource for Phenotyping and Complex Trait Mapping

      Velmurugan, Janaki; Milbourne, Dan; Connolly, Vincent; Heslop-Harrison, J. S.; Anhalt, Ulrike C. M.; Lynch, M. B.; Barth, Susanne; Teagasc Walsh Fellowship Programme (Frontiers, 2018-05-31)
      To address the lack of a truly portable, universal reference mapping population for perennial ryegrass, we have been developing a recombinant inbred line (RIL) mapping population of perennial ryegrass derived via single seed descent from a well-characterized F2 mapping population based on genetically distinct inbred parents in which the natural self-incompatibility (SI) system of perennial ryegrass has been overcome. We examined whether it is possible to create a genotyping by sequencing (GBS) based genetic linkage map in a small population of the F6 generation of this population. We used 41 F6 genotypes for GBS with PstI/MspI-based libraries. We successfully developed a genetic linkage map comprising 6074 SNP markers, placing a further 22080 presence and absence variation (PAV) markers on the map. We examined the resulting genetic map for general and RIL specific features. Overall segregation distortion levels were similar to those experienced in the F2 generation, but segregation distortion was reduced on linkage group 6 and increased on linkage group 7. Residual heterozygosity in the F6 generation was observed at a level of 5.4%. There was a high proportion of chromosomes (30%) exhibiting the intact haplotype of the original inbred parents of the F1 genotype from which the population is derived, pointing to a tendency for chromosomes to assort without recombining. This could affect the applicability of these lines and might make them more suitable for situations where repressed recombination is an advantage. Inter- and intra-chromosomal linkage disequilibrium (LD) analysis suggested that the map order was robust. We conclude that this RIL population, and subsequent F7 and F8 generations will be useful for genetic analysis and phenotyping of agronomic and biological important traits in perennial ryegrass.
    • Impact of agronomic practices of an intensive dairy farm on nitrogen concentrations in a karst aquifer in Ireland

      Huebsch, Manuela; Horan, Brendan; Blum, P.; Richards, Karl G.; Grant, Jim; Fenton, Owen; Teagasc Walsh Fellowship Programme (Elsevier, 24/09/2013)
      Exploring the relationship between agricultural nitrogen loading on a dairy farm and groundwater reactive nitrogen concentration such as nitrate is particularly challenging in areas underlain by thin soils and karstified limestone aquifers. The objective of this study is to relate changes in detailed agronomic N-loading, local weather conditions, hydrogeological and geological site characteristics with groundwater N occurrence over an 11-year period on an intensive dairy farm with free draining soils and a vulnerable limestone aquifer. In addition, the concept of vertical time lag from source to receptor is considered. Statistical analysis used regression with automatic variable selection. Four scenarios were proposed to describe the relationships between paddock and groundwater wells using topographic and hydrogeological assumptions. Monitored nitrate concentrations in the studied limestone aquifer showed a general decrease in the observed time period (2002–2011). Statistical results showed that a combination of improved agronomic practices and site specific characteristics such as thicknesses of the soil and unsaturated zone together with hydrogeological connections of wells and local weather conditions such as rainfall, sunshine and soil moisture deficit were important explanatory variables for nitrate concentrations. Statistical results suggested that the following agronomic changes improved groundwater quality over the 11-year period: reductions in inorganic fertiliser usage, improvements in timing of slurry application, the movement of a dairy soiled water irrigator to less karstified areas of the farm and the usage of minimum cultivation reseeding on the farm. In many cases the explanatory variables of farm management practices tended to become more important after a 1- or 2-year time lag. Results indicated that the present approach can be used to elucidate the effect of farm management changes to groundwater quality and therefore the assessment of present and future legislation implementations.
    • The impact of cattle dung pats on earthworm distribution in grazed pastures

      Bacher, M. G.; Fenton, Owen; Bondi, G.; Creamer, Rachel; Karmarkar, M.; Schmidt, O.; Department of Agriculture, Food and the Marine; 13/S/468 (Springer Science and Business Media LLC, 2018-12-19)
      Background Grazed grassland management regimes can have various effects on soil fauna. For example, effects on earthworms can be negative through compaction induced by grazing animals, or positive mediated by increases in sward productivity and cattle dung pats providing a food source. Knowledge gaps exist in relation to the behaviour of different earthworm species i.e. their movement towards and aggregation under dung pats, the legacy effects of pats and the spatial area of recruitment. The present study addressed these knowledge gaps in field experiments, over 2 years, using natural and simulated dung pats on two permanent, intensively grazed pastures in Ireland. Results Dung pats strongly affected spatial earthworm distribution, with up to four times more earthworms aggregating beneath pats, than in the control locations away from pats. In these earthworm communities comprising 11 species, temporally different aggregation and dispersal patterns were observed, including absence of individual species from control locations, but no clear successional responses. Epigeic species in general, but also certain species of the anecic and endogeic groups were aggregating under dung. Sampling after complete dung pat disappearance (27 weeks after application) suggested an absence of a dung pat legacy effect on earthworm communities. Based on species distributions, the maximum size of the recruitment area from which earthworms moved to pats was estimated to be 3.8 m2 per dung pat. Since actual grazing over 6 weeks would result in the deposition of about 300 dung pats per ha, it is estimated that a surface area of 1140 m2 or about 11% of the total grazing area can be influenced by dung pats in a given grazing period. Conclusions This study showed that the presence of dung pats in pastures creates temporary hot spots in spatial earthworm species distribution, which changes over time. The findings highlight the importance of considering dung pats, temporally and spatially, when sampling earthworms in grazed pastures. Published comparisons of grazed and cut grasslands probably reached incorrect conclusions by ignoring or deliberately avoiding dung pats. Furthermore, the observed intense aggregation of earthworms beneath dung pats suggests that earthworm functions need to be assessed separately at these hot spots.
    • Impact of chemical amendment of dairy cattle slurry on phosphorus, suspended sediment and metal loss to runoff from a grassland soil

      Brennan, Raymond B.; Fenton, Owen; Grant, Jim; Healy, Mark G.; Teagasc Walsh Fellowship Programme (Elsevier, 01/11/2011)
      Emerging remediation technologies such as chemical amendment of dairy cattle slurry have the potential to reduce phosphorus (P) solubility and consequently reduce P losses arising from land application of dairy cattle slurry. The aim of this study was to determine the effectiveness of chemical amendment of slurry to reduce incidental losses of P and suspended sediment (SS) from grassland following application of dairy cattle slurry and to examine the effect of amendments on metal concentrations in runoff water. Intact grassed-soil samples were placed in two laboratory runoff boxes, each 200-cm-long by 22.5-cm-wide by 5-cm-deep, before being amended with dairy cattle slurry (the study control) and slurry amended with either: (i) alum, comprising 8% aluminium oxide (Al2O3) (1.11:1 aluminium (Al):total phosphorus (TP) of slurry) (ii) poly-aluminium chloride hydroxide (PAC) comprising 10% Al2O3 (0.93:1 Al:TP) (iii) analytical grade ferric chloride (FeCl2) (2:1 Fe:TP), (iv) and lime (Ca(OH)2) (10:1 Ca:TP). When compared with the study control, PAC was the most effective amendment, reducing dissolved reactive phosphorus (DRP) by up to 86% while alum was most effective in reducing SS (88%), TP (94%), particulate phosphorus (PP) (95%), total dissolved phosphorus (TDP) (81%), and dissolved unreactive phosphorus (DUP) (86%). Chemical amendment of slurry did not appear to significantly increase losses of Al and Fe compared to the study control, while all amendments increased Ca loss compared to control and grass-only treatment. While chemical amendments were effective, the reductions in incidental P losses observed in this study were similar to those observed in other studies where the time from slurry application to the first rainfall event was increased. Timing of slurry application may therefore be a much more feasible way to reduce incidental P losses. Future work must examine the long-term effects of amendments on P loss to runoff and not only incidental losses.
    • Impact of chemically amended pig slurry on greenhouse gas emissions, soil properties and leachate

      O'Flynn, Cornelius J.; Healy, Mark G.; Lanigan, Gary; Troy, Shane M.; Somers, Cathal; Fenton, Owen; Irish Research Council for Science, Engineering and Technology (Elsevier, 10/07/2013)
      The effectiveness of chemical amendment of pig slurry to ameliorate phosphorus (P) losses in runoff is well studied, but research mainly has concentrated only on the runoff pathway. The aims of this study were to investigate changes to leachate nutrient losses, soil properties and greenhouse gas (GHG) emissions due to the chemical amendment of pig slurry spread at 19 kg total phosphorus (TP), 90 kg total nitrogen (TN), and 180 kg total carbon (TC) ha-1. The amendments examined were: (1) commercial grade liquid alum (8% Al2O3) applied at a rate of 0.88:1 [Al: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 (PAC) (10% Al2O3) applied at a rate of 0.72:1 [Al:TP]. Columns filled with sieved soil were incubated for 8 mo at 10oC and were leached with 160 ml (19 mm) distilled water wk-1. All amendments reduced the Morgan’s phosphorus and water extractable P content of the soil to that of the soil-only treatment, indicating that they have the ability to reduce P loss in leachate following slurry application. There were no significant differences between treatments for nitrogen (N) or carbon (C) in leachate or soil, indicating no deleterious impact on reactive N emissions or soil C cycling. Chemical amendment posed no significant change to GHG emissions from pig slurry, and in the cases of alum and PAC, reduced cumulative N2O and CO2 losses. Chemical amendment of land applied pig slurry can reduce P in runoff without any negative impact on nutrient leaching and GHG emissions. Future work must be conducted to ascertain if more significant reductions in GHG emissions are possible with chemical amendments.
    • The Impact of Chemically Amended Pig Slurry on Surface Runoff, Leachate and Greenhouse Gasses

      O'Flynn, Cornelius J.; Irish Research Council (2013-05)
      In Ireland, the pig industry is concentrated in a small number of counties. Pig farms typically have a high stocking rate. Therefore, the disposal of slurry in a cost-effective and environmentally-responsible way is a serious issue for farmers. Slurry is commonly applied to land, but this may not be possible if the land is at, or approaching, phosphorus (P) saturation. As pig farmers dispose of slurry in the vicinity of their properties, most of the nearby land is at P saturation, so alternative treatment methods need to be utilised (e.g. constructed wetlands, anaerobic digestion, filtration) or the slurry needs to be transported to another location. These alternatives are not currently financially viable in Ireland. Existing legislation (S.I. 610 of 2010) and recent changes in the implementation of legislation governing the timing and quantities of slurry that may be applied to land, means that pig farmers will no longer be able to exceed the maximum legal application rate to land (from January 2017). European policy aiming to intensify pig production will only accentuate this problem. If pig farmers are forced, in exceptional circumstances, to land apply slurry to unsuitable land, surface and subsurface losses of nutrients and suspended solids (SS) may occur. This could be potentially problematic if the land is located in a critical source area (CSA), an area that is highly likely to pollute receiving waters. In these circumstances, a possible novel solution is to chemically amend the pig slurry prior to landspreading. This would mean that pig farmers may, in exceptional circumstances, utilise the land in the vicinity of their farms for landspreading, without releasing excessive nutrients and SS into receiving waters. However, knowledge gaps exist concerning the type of amendments to be used, the characteristics of the soil on which they can be most effectively used, and their impact on incidental (short-term) and chronic (long-term) losses of nutrients, SS and greenhouse gas (GHG) to surface and subsurface water and the atmosphere. Therefore, the aims of this project were to: (1) identify the most appropriate chemical amendments, and their addition rates, to reduce P losses in runoff from pig slurry based on effectiveness, cost and feasibility; (2) investigate the impacts of these chemical amendments on nutrient losses in leachate, soil properties and GHG emissions; and (3) identify suitable soil types on which to landspread chemically-amended pig slurry. Laboratory bench-scale experiments were designed to identify the amendments which had the potential to reduce P in overland runoff and to quantify the stoichiometric rates at which to add them to the slurry. Based on effectiveness, cost and feasibility, the amendments identified were alum, which reduced dissolved reactive phosphorus (DRP) in overlying water by 86%, poly-aluminium chloride (PAC) (73%) and ferric chloride (FeCl3) (71%). Following these bench-scale experiments, rainfall simulation experiments were conducted to quantify the impact of chemical amendments to slurry on surface runoff losses at various time intervals from the time of application. Poly-aluminium chloride performed best in these experiments. For the first time, the effect of these amendments on GHG emissions, soil properties and leachate was also examined. Chemical amendment did not adversely affect GHG emissions, soil properties or leachate from pig slurry, but FeCl3 increased nitrous oxide (N2O) and carbon dioxide (CO2) losses. Finally, a 3-mo incubation experiment was conducted using a range of soil types to examine the effect of amendments on the long-term plant availability of P in soil and P solubility. Alum reduced more water extractable P than PAC, but also resulted in less plant available P. Considering cost, surface runoff and subsurface leachate losses, GHG emissions and impacts on soil chemistry, PAC was found to be the most suitable amendment with which to chemically amend pig slurry. There is the potential, in combination with existing programmes of measures, to employ chemical amendment as a measure to mitigate the environmental impact arising from the landspreading of pig slurry. This should be conducted in targeted areas of the CSA and should take into account soil type and its chemical properties. Before implementation, these tests must first be validated in long-term testing at field-scale over a wide variety of soil types, and include repeated application and incorporation. At present, there is no provision in legislation for chemical amendments to be used as a mitigation measure in the land application of pig slurry, but if they are to be utilised, a regulatory framework will need to be introduced by the relevant bodies.
    • The impact of grazing cattle on soil physical properties and nutrient concentrations in overland flow from pasture, Part B

      Kurz, Isabelle; O’Reilly, Conor; Tunney, Hubert; Bourke, David; Environmental Protection Agency (Teagasc, 01/06/2007)
      The loss of nutrients from agricultural land to water bodies is a serious concern in many countries. To gain information on the contribution of grazing animals to diffuse nutrient losses from pasture areas to water, this study looked at the impact of cattle on nutrient concentrations in overland flow and on soil hydrology (bulk density, macroporosity and resistance to penetration). Rainfall simulations to produce overland flow were conducted and soil physical measurements were taken on experimental plots assigned to one of two treatments: 1) cattle had unrestricted access to the plot; 2) cattle could graze the plot but they could neither walk on the plot area nor deposit excrements on it. Areas to which the cattle had free access were characterised by 57%-83% lower macroporosity, by 8%-17% higher bulk density and by 27%-50% higher resistance to penetration than areas from which the cattle were excluded. The nutrients in overland flow from grassland that were affected by the presence of grazing animals were mainly the particulate nitrogen, the organic phosphorus and the potassium concentrations. Overall, the presence of cattle had a longer lasting effect on the soil hydrological parameters measured than on the nutrient concentrations in overland flow.
    • Impact of P inputs on source-sink P dynamics of sediment along an agricultural ditch network

      Ezzati, G.; Fenton, Owen; Healy, M.G.; Christianson, L.; Feyereisen, G.W.; Thornton, S.; Chen, Q.; Fan, B.; Ding, J.; Daly, Karen; et al. (Elsevier BV, 2020-03)
      Phosphorus (P) loss from intensive dairy farms is a pressure on water quality in agricultural catchments. At farm scale, P sources can enter in-field drains and open ditches, resulting in transfer along ditch networks and delivery into nearby streams. Open ditches could be a potential location for P mitigation if the right location was identified, depending on P sources entering the ditch and the source-sink dynamics at the sediment-water interface. The objective of this study was to identify the right location along a ditch to mitigate P losses on an intensive dairy farm. High spatial resolution grab samples for water quality, along with sediment and bankside samples, were collected along an open ditch network to characterise the P dynamics within the ditch. Phosphorus inputs to the ditch adversely affected water quality, and a step change in P concentrations (increase in mean dissolved reactive phosphorus (DRP) from 0.054 to 0.228 mg L−1) midway along the section of the ditch sampled, signalled the influence of a point source entering the ditch. Phosphorus inputs altered sediment P sorption properties as P accumulated along the length of the ditch. Accumulation of bankside and sediment labile extractable P, Mehlich 3 P (M3P) (from 13 to 97 mg kg−1) resulted in a decrease in P binding energies (k) to < 1 L mg−1 at downstream points and raised the equilibrium P concentrations (EPC0) from 0.07 to 4.61 mg L−1 along the ditch. The increase in EPC0 was in line with increasing dissolved and total P in water, demonstrating the role of sediment downstream in this ditch as a secondary source of P to water. Implementation of intervention measures are needed to both mitigate P loss and remediate sediment to restore the sink properties. In-ditch measures need to account for a physicochemical lag time before improvements in water quality will be observed.
    • Impact of pig slurry amendments on phosphorus, suspended sediment and metal losses in laboratory runoff boxes under simulated rainfall

      O'Flynn, Cornelius J.; Fenton, Owen; Wilson, Paul; Healy, Mark G.; Irish Research Council for Science, Engineering and Technology (Elsevier, 30/12/2012)
      Losses of phosphorus (P) when pig slurry applications to land are followed by a rainfall event or losses from soils with high P contents can contribute to eutrophication of receiving waters. The addition of amendments to pig slurry spread on high P Index soils may reduce P and suspended sediment (SS) losses. This hypothesis was tested at laboratory-scale using runoff boxes under simulated rainfall conditions. Intact grassed soil samples, 100 cm-long, 22.5 cm-wide and 5 cm-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 (PAC) (10% Al2O3) applied at a rate of 0.72:1 [Al:TP]. The grassed soil was then subjected to three rainfall events (10.3 ± 0.15 mm h−1) at time intervals of 48, 72, and 96 h following slurry application. Each sod received rainfall on 3 occasions. Results across three rainfall events showed that for the control treatment, the average flow weighted mean concentration (FWMC) of TP was 0.61 mg L−1, of which 31% was particulate phosphorus (PP), and the average FWMC of SS was 38.1 mg L−1. For the slurry treatment, there was an average FWMC of 2.2 mg TP L−1, 47% of which was PP, and the average FWMC of SS was 71.5 mg L−1. Ranked in order of effectiveness from best to worst, PAC reduced the average FWMC of TP to 0.64 mg L−1 (42% PP), FeCl3 reduced TP to 0.91 mg L−1 (52% PP) and alum reduced TP to 1.08 mg L−1 (56% PP). The amendments were in the same order when ranked for effectiveness at reducing SS: PAC (74%), FeCl3 (66%) and alum (39%). Total phosphorus levels in runoff plots receiving amended slurry remained above those from soil only, indicating that, although incidental losses could be mitigated by chemical amendment, chronic losses from the high P index soil in the current study could not be reduced.
    • The Impact of Policy Instruments on Soil Multifunctionality in the European Union

      Vrebos, Dirk; Bampa, Francesca; Creamer, Rachel E.; Gardi, Ciro; Ghaley, Bhim Bahadur; Jones, Arwyn; Rutgers, Michiel; Sandén, Taru; Staes, Jan; Meire, Patrick; et al. (MDPI, 2017-03-09)
      Agricultural ecosystems provide a range of benefits that are vital to human well-being. These benefits are dependent on several soil functions that are affected in different ways by legislation from the European Union, national, and regional levels. We evaluated current European Union soil-related legislation and examples of regional legislation with regard to direct and indirect impacts on five soil functions: the production of food, fiber, and fuel; water purification and regulation; carbon sequestration and climate regulation; habitat for biodiversity provisioning; and the recycling of nutrients/agro-chemicals. Our results illustrate the diversity of existing policies and the complex interactions present between different spatial and temporal scales. The impact of most policies, positive or negative, on a soil function is usually not established, but depends on how the policy is implemented by local authorities and the farmers. This makes it difficult to estimate the overall state and trends of the different soil functions in agricultural ecosystems. To implement functional management and sustainable use of the different soil functions in agricultural ecosystems, more knowledge is needed on the policy interactions as well as on the impact of management options on the different soil functions.
    • Impact of Soil Type, Biology and Temperature on the Survival of Non-Toxigenic Escherichia Coli O157

      Moynihan, Emma; Richards, Karl G.; Ritz, Karl; Tyrrel, Sean; Brennan, Fiona P.; Teagasc Walsh Fellowship Programme (Royal Irish Academy, 14/06/2013)
      The occurrence of microbial enteropathogens in the environment can represent a serious risk to human health. The fate of enteropathogens introduced into the soil environment is dependent on a wide range of complex interacting environmental factors. While the effect of abiotic factors on enteropathogen survival has been widely examined, the interaction of enteropathogens with the soil microbial community is poorly understood. This study investigated the effect of soil biology and soil type on the survival of a non-toxigenic strain of Escherichia coli O157 under different temperature regimes. Soil microcosms of two soil types, with and without an intact microbial community, were inoculated with the enteropathogen surrogate, and survival was determined over a 64-day period, encompassing a shift from cold to ambient temperatures. In both soil types bacterial numbers decreased in soil with an intact microflora, while in the absence of an intact community E. coli populations increased. This effect was temperature specific, with E. coli populations remaining stable at low temperature, regardless of treatment. Soil type was of importance in survival at both cold and ambient temperatures. This work highlights the signifi cance of the soil microbial community in suppressing enteropathogens in soil, and of investigating die-off in a multi-factorial manner.
    • The impact of the grazing animal on phosphorus, nitrogen, potassium and suspended solids loss from grazed pastures, Part A

      Tunney, Hubert; Kurz, Isabelle; Bourke, David; O'Reilly, Colin; Jeffrey, D.W.; Dowding, P.; Foy, B.; Kilpatrick, D.J.; Haygarth, P. (Teagasc, 01/06/2007)
      In Ireland 90% of the 4.2 million ha of farmland is grassland. Phosphorus deficiency limited grassland production in Ireland and this was corrected by chemical fertiliser use in the 1960s and 1970s. The increased inputs of fertilisers led to increased intensification of grassland with a doubling of grass yield and of grazing animal numbers, from about 3 million to over 6 million livestock units. There is little information on relative contribution of increased chemical fertiliser use compared to increased grazing animal numbers on phosphorus loss to water. The main objective of this study was to obtain information on nutrient loss, particularly phosphorus, in overland flow from cut and grazed grassland plots, with a range of soil test phosphorus levels over three years and implications.