• Ammonia emissions from cattle dung, urine and urine with dicyandiamide in a temperate grassland

      Fischer, K.; Burchill, William; Lanigan, Gary; Kaupenjohann, M.; Chambers, B. J.; Richards, Karl G.; Forrestal, Patrick J.; Department of Agriculture, Food and the Marine, Ireland (Wiley, 03/09/2015)
      Deposition of urine and dung in pasture-based livestock production systems is a major source of ammonia (NH3) volatilization, contributing to the eutrophication and acidification of water bodies and to indirect nitrous oxide emissions. The objectives of this study were to (i) measure NH3 volatilization from dung and urine in three seasons, (ii) test the effect of spiking urine with the nitrification inhibitor dicyandiamide (DCD) on NH3 volatilization and (iii) generate NH3 emission factors (EFs) for dung, urine and urine + DCD in temperate maritime grassland. Accordingly, simulated dung, urine and urine spiked with DCD (at 30 kg DCD/ha equivalent rate) patches were applied to temperate grassland. Treatments were applied three times in 2014 with one measurement of NH3 loss being completed in spring, summer and autumn. The NH3-N EF was highest in spring, which was most likely due to the near absence of rainfall throughout the duration of loss measurement. The EFs across the experiments ranged between 2.8 and 5.3% (mean 3.9%) for dung, 8.7 and 14.9% (mean 11.2%) for urine and 9.5 and 19.5% (mean 12.9%) for urine + DCD, showing that ammonia loss from dung was significantly lower than from urine. Aggregating country-specific emission data such as those from the current experiment with data from climatically similar regions (perhaps in a weighted manner which accounts for the relative abundance of certain environmental conditions) along with modelling is a potentially resource-efficient approach for refining national ammonia inventories.
    • Reducing nitrous oxide emissions by changing N fertiliser use from calcium ammonium nitrate (CAN) to urea based formulations

      Harty, Mary A.; Forrestal, Patrick J.; Watson, C. J.; McGeough, K. L.; Carolan, Rachael; Elliott, C.; Krol, Dominika; Laughlin, Ronald J.; Richards, Karl G.; Lanigan, Gary; et al. (Elsevier, 04/05/2016)
      The accelerating use of synthetic nitrogen (N) fertilisers, to meet the world's growing food demand, is the primary driver for increased atmospheric concentrations of nitrous oxide (N2O). The IPCC default emission factor (EF) for N2O from soils is 1% of the N applied, irrespective of its form. However, N2O emissions tend to be higher from nitrate-containing fertilisers e.g. calcium ammonium nitrate (CAN) compared to urea, particularly in regions, which have mild, wet climates and high organic matter soils. Urea can be an inefficient N source due to NH3 volatilisation, but nitrogen stabilisers (urease and nitrification inhibitors) can improve its efficacy. This study evaluated the impact of switching fertiliser formulation from calcium ammonium nitrate (CAN) to urea-based products, as a potential mitigation strategy to reduce N2O emissions at six temperate grassland sites on the island of Ireland. The surface applied formulations included CAN, urea and urea with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and/or the nitrification inhibitor dicyandiamide (DCD). Results showed that N2O emissions were significantly affected by fertiliser formulation, soil type and climatic conditions. The direct N2O emission factor (EF) from CAN averaged 1.49% overall sites, but was highly variable, ranging from 0.58% to 3.81. Amending urea with NBPT, to reduce ammonia volatilisation, resulted in an average EF of 0.40% (ranging from 0.21 to 0.69%)-compared to an average EF of 0.25% for urea (ranging from 0.1 to 0.49%), with both fertilisers significantly lower and less variable than CAN. Cumulative N2O emissions from urea amended with both NBPT and DCD were not significantly different from background levels. Switching from CAN to stabilised urea formulations was found to be an effective strategy to reduce N2O emissions, particularly in wet, temperate grassland.
    • The effect of cattle slurry in combination with nitrate and the nitrification inhibitor dicyandiamide on in situ nitrous oxide and dinitrogen emissions

      McGeough, K. L.; Laughlin, Ronald J.; Watson, C. J.; Muller, Christoph; Ernfors, M.; Cahalan, E.; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; RSF 07 519 (European Geosciences Union, 04/12/2012)
      A field study was conducted to determine the effect of the nitrification inhibitor dicyandiamide (DCD) on N2O and N2 emissions after cattle slurry (CS) application in the presence of nitrate (NO3) fertiliser on seven different occasions (between March 2009 and March 2011). N2O emissions from CS in the presence of NO3 fertiliser were very high (0.4–8.7% of applied N) over a 20-day period, under mild moist conditions. Emissions were significantly larger from the CS treatment compared to an NH4+-N source, supplying the same rate of N as in the slurry. This study supports the view that organic fertilisers should not be applied at the same time as nitrate-based fertilisers, as significant increases in N2O emissions occur. The average N2O mole fraction (N2O/(N2O + N2)) over all seven application dates was 0.34 for CSNO3 compared to 0.24 for the NH4ClNO3 treatment, indicating the dominance of N2 emissions. The rate of nitrification in CSNO3 was slower than in NH4ClNO3, and DCD was found to be an effective nitrification inhibitor in both treatments. However, as N2O emissions were found to be predominantly associated with the NO3 pool, the effect of DCD in lowering N2O emissions is limited in the presence of a NO3 fertiliser. To obtain the maximum cost-benefit of DCD in lowering N2O emissions, under mild moist conditions, it should not be applied to a nitrate containing fertiliser (e.g. ammonium nitrate or calcium ammonium nitrate), and therefore the application of DCD should be restricted to ammonium-based organic or synthetic fertilisers.
    • 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.
    • 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.
    • 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.
    • Effect of an agri-environmental measure on nitrate leaching from a beef farming system in Ireland

      Richards, Karl G.; Jahangir, Mohammad M. R.; Drennan, Michael J; Lenehan, J.J.; Connolly, John; Brophy, C.; Carton, Owen T. (Elsevier, 07/01/2015)
      Agricultural nitrogen (N) management remains a key environmental challenge. Improving N management is a matter of urgency to reduce the serious ecological consequences of the reactive N. Nitrate (NO3−–N) leaching was measured under suckler beef production systems stocked at two intensities: (1) intensive, 210 kg organic N ha−1 with two cut silage harvests; and (2) rural environmental protection scheme (REPS), 170 kg organic N ha−1 with one cut silage harvest. Three replicate plots of each treatment were instrumented with ceramic cups (8 per plot), randomly placed within each plot at a depth of 1 m to collect soil solution for NO3−–N at 50 kPa suction to collecting vessels one week prior to sampling. Samples were taken on a total of 53 sampling dates over 3 winter drainage periods (2002/03, 2003/04 and 2004/05). Over the course of the experiment the mean annual soil solution NO3−–N concentration exceeded the MAC twice out of 15 means (5 treatments over 3 years). The REPS grazing and silage sub treatments had significantly lower mean annual soil solution total oxidized N (TON) concentrations than the respective intensive treatments in years 2 and 3. Annual total NO3−–N losses over the three years in intensive and REPS systems ranged from 55 to 71 and 15 to 20 kg N ha−1, respectively. Mean N surpluses in intensive and REPS systems were 210 and 95 kg ha−1, respectively with the corresponding mean N inputs of 272 and 124 kg N ha−1. The reduction in N inputs under the REPS system results in lower N leaching losses and contributed to a significant reduction in pressures on water quality.
    • Effect of organic, conventional and mixed cultivation practices on soil microbial community structure and nematode abundance in a cultivated onion crop

      Reilly, Kim; Cullen, Eileen; Lola-Luz, Theodora; Stone, Dote; Valverde, Juan; Gaffney, Michael; Brunton, Nigel; Grant, Jim; Griffiths, Bryan; Department of Agriculture, Food and the Marine, Ireland; et al. (Wiley, 07/06/2013)
      BACKGROUND: Responses of the soil microbial and nematode community to organic and conventional agricultural practices were studied using the Teagasc Kinsealy Systems Comparison trial as the experimental system. The trial is a long term field experiment which divides conventional and organic agriculture into component pest-control and soil treatment practices. We hypothesised that management practices would affect soil ecology and used community level physiological profiles (CLPP), microbial and nematode counts, and denaturing gradient gel electrophoresis (DGGE) to characterise soil microbial communities in plots used for onion (Allium cepa L.) cultivation. RESULTS: Microbial activity and culturable bacterial counts were significantly higher under fully organic management. Culturable fungi, actinomycete and nematode counts showed a consistent trend towards higher numbers under fully organic management but these data were not statistically significant. No differences were found in the fungal/bacterial ratio. DGGE banding patterns and sequencing of excised bands showed clear differences between treatments. Putative onion fungal pathogens were predominantly sequenced under conventional soil treatment practices whilst putative soil suppressive bacterial species were predominantly sequenced from the organic pest-control treatment plots. CONCLUSION: Organic management increased microbial activity and diversity. Sequence data was indicative of differences in functional groups and warrants further investigation.
    • Field boundary habitats and their contribution to the area of semi-natural habitats on lowland farms in east Galway, western Ireland

      Sullivan, C. A.; Finn, John; Gormally, Michael; Sheehy Skeffington, Micheline; Teagasc Walsh Fellowship Programme (Royal Irish Academy, 07/11/2013)
      Sustainable agriculture and the provision of environmental public goods are key deliverables for European farming and food production. Farmland biodiversity, cultural landscapes, soil functionality and climate stability are among the environmental public goods provided through agriculture. Future Common Agricultural Policy (CAP) direct payments are intended to be more targeted at the provision of these agricultural deliverables. Field boundaries are an example of such deliverables. They are widespread features that have both environmental and aesthetic functions in farmed landscapes. However, research on their variety, density and contribution to semi-natural habitat cover on farms in Ireland is lacking. This study investigates the diversity and density of all field boundary habitat types on 32 lowland farms in east County Galway, western Ireland. A total of 286km of field boundaries were surveyed across six study sites. Five types of field boundary habitats were recorded. The density of field boundaries on the farms studied was high and could have positive implications for delivery of environmental public goods and sustainable farming metrics. In more intensively farmed areas, field boundaries were the only remaining semi-natural habitat on some farms highlighting the need to retain, and improve the ecological quality, of these features. The condition of one field boundary type (hedgerows) was also investigated in further detail. While the density of field boundaries was high on many of the surveyed farms, we found that the hedgerows on these farms were not necessarily in good condition for wildlife.
    • Atypical Listeria innocua strains possess an intact LIPI-3

      Clayton, Evelyn M; Daly, Karen M.; Guinane, Caitriona M.; Hill, Colin; Cotter, Paul D.; Ross, R Paul; Enterprise Ireland; Science Foundation Ireland; 06/IN.1/B98; 10/IN.1/B3027 (Biomed Central, 08/03/2014)
      Background: Listeria monocytogenes is a food-borne pathogen which is the causative agent of listeriosis and can be divided into three evolutionary lineages I, II and III. While all strains possess the well established virulence factors associated with the Listeria pathogenicity island I (LIPI-1), lineage I strains also possess an additional pathogenicity island designated LIPI-3 which encodes listeriolysin S (LLS), a post-translationally modified cytolytic peptide. Up until now, this pathogenicity island has been identified exclusively in a subset of lineage I isolates of the pathogen Listeria monocytogenes. Results: In total 64 L. innocua strains were screened for the presence of LIPI-3. Here we report the identification of an intact LIPI-3 in 11 isolates of L. innocua and the remnants of the cluster in several others. Significantly, we can reveal that placing the L. innocua lls genes under the control of a constitutive promoter results in a haemolytic phenotype, confirming that the cluster is capable of encoding a functional haemolysin. Conclusions: Although the presence of the LIPI-3 gene cluster is confined to lineage I isolates of L. monocytogenes, a corresponding gene cluster or its remnants have been identified in many L. innocua strains.
    • The short-term effects of management changes on watertable position and nutrients in shallow groundwater in a harvested peatland forest

      Finnegan, Joanne; Regan, J. T.; Fenton, Owen; Lanigan, Gary; Brennan, Raymond B.; Healy, Mark G.; Environmental Protection Agency; Department of Agriculture, Food and the Marine, Ireland (Elsevier, 08/05/2014)
      Management changes such as drainage, fertilisation, afforestation and harvesting (clearfelling) of forested peatlands influence watertable (WT) position and groundwater concentrations of nutrients. This study investigated the impact of clearfelling of a peatland forest on WT and nutrient concentrations. Three areas were examined: (1) a regenerated riparian peatland buffer (RB) clearfelled four years prior to the present study (2) a recently clearfelled coniferous forest (CF) and (3) a standing, mature coniferous forest (SF), on which no harvesting took place. The WT remained consistently below 0.3 m during the pre-clearfelling period. Results showed there was an almost immediate rise in the WT after clearfelling and a rise to 0.15 m below ground level (bgl) within 10 months of clearfelling. Clearfelling of the forest increased dissolved reactive phosphorus concentrations (from an average of 28–230 μg L−1) in the shallow groundwater, likely caused by leaching from degrading brash mats.
    • The Effect of Chemical Amendments Used for Phosphorus Abatement on Greenhouse Gas and Ammonia Emissions from Dairy Cattle Slurry: Synergies and Pollution Swapping

      Brennan, Raymond B.; Healy, Mark G.; Fenton, Owen; Lanigan, Gary; European Union; Teagasc Walsh Fellowship Programme; FP7-KBBE-2010-4 (PLoS, 08/06/2015)
      Land application of cattle slurry can result in incidental and chronic phosphorus (P) loss to waterbodies, leading to eutrophication. Chemical amendment of slurry has been proposed as a management practice, allowing slurry nutrients to remain available to plants whilst mitigating P losses in runoff. The effectiveness of amendments is well understood but their impacts on other loss pathways (so-called ‘pollution swapping’ potential) and therefore the feasibility of using such amendments has not been examined to date. The aim of this laboratory scale study was to determine how the chemical amendment of slurry affects losses of NH3, CH4, N2O, and CO2. Alum, FeCl2, Polyaluminium chloride (PAC)- and biochar reduced NH3 emissions by 92, 54, 65 and 77% compared to the slurry control, while lime increased emissions by 114%. Cumulative N2O emissions of cattle slurry increased when amended with alum and FeCl2 by 202% and 154% compared to the slurry only treatment. Lime, PAC and biochar resulted in a reduction of 44, 29 and 63% in cumulative N2O loss compared to the slurry only treatment. Addition of amendments to slurry did not significantly affect soil CO2 release during the study while CH4 emissions followed a similar trend for all of the amended slurries applied, with an initial increase in losses followed by a rapid decrease for the duration of the study. All of the amendments examined reduced the initial peak in CH4 emissions compared to the slurry only treatment. There was no significant effect of slurry amendments on global warming potential (GWP) caused by slurry land application, with the exception of biochar. After considering pollution swapping in conjunction with amendment effectiveness, the amendments recommended for further field study are PAC, alum and lime. This study has also shown that biochar has potential to reduce GHG losses arising from slurry application.
    • Denitrification and indirect N2O emissions in groundwater: Hydrologic and biogeochemical influences

      Jahangir, Mohammad M. R.; Johnston, Paul; Barrett, Maria; Khalil, Mohammed I.; Groffman, P.M.; Boeckx, P.; Fenton, Owen; Murphy, John; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; et al. (Elsevier, 08/07/2013)
      Identification of specific landscape areas with high and low groundwater denitrification potential is critical for improved management of agricultural nitrogen (N) export to ground and surface waters and indirect nitrous oxide (N2O) emissions. Denitrification products together with concurrent hydrogeochemical properties were analysed over two years at three depths at two low (L) and two high (H) permeability agricultural sites in Ireland. Mean N2O–N at H sites were significantly higher than L sites, and decreased with depth. Conversely, excess N2–N were significantly higher at L sites than H sites and did not vary with depth. Denitrification was a significant pathway of nitrate (NO3−–N) reduction at L sites but not at H sites, reducing 46–77% and 4–8% of delivered N with resulting mean NO3−–N concentrations of 1–4 and 12–15 mg N L− 1 at L and H sites, respectively. Mean N2O–N emission factors (EF5g) were higher than the most recent Intergovernmental Panel on Climate Change (IPCC, 2006) default value and more similar to the older IPCC (1997) values. Recharge during winter increased N2O but decreased excess dinitrogen (excess N2–N) at both sites, probably due to increased dissolved oxygen (DO) coupled with low groundwater temperatures. Denitrifier functional genes were similar at all sites and depths. Data showed that highly favourable conditions prevailed for denitrification to occur — multiple electron donors, low redox potential (Eh < 100 mV), low DO (< 2 mg L− 1), low permeability (ks < 0.005 m·d− 1) and a shallow unsaturated zone (< 2 m). Quantification of excess N2–N in groundwater helps to close N balances at the local, regional and global scales.
    • The interactive effects of fertiliser nitrogen with dung and urine on nitrous oxide emissions in grassland

      Hyde, Bernard; Forrestal, Patrick J.; Jahangir, Mohammad M. R.; Ryan, Michael; Fanning, A.; Carton, Owen T.; Lanigan, Gary; Richards, Karl G.; Environmental Protection Agency; Department of Agriculture, Food and the Marine, Ireland; et al. (Teagasc (Agriculture and Food Development Authority), Ireland, 08/09/2016)
      Nitrous oxide (N2O) is an important and potent greenhouse gas (GHG). Although application of nitrogen (N) fertiliser is a feature of many grazing systems, limited data is available on N2O emissions in grassland as a result of the interaction between urine, dung and fertiliser N. A small plot study was conducted to identify the individual and interactive effects of calcium ammonium nitrate (CAN) fertiliser, dung and urine. Application of CAN with dung and urine significantly increased the mass of N2O-N emission. Importantly, the sum of N2O-N emitted from dung and CAN applied individually approximated the emission from dung and CAN fertiliser applied together, that is, an additive effect. However, in the case of urine and CAN applied together, the emission was more than double the sum of the emission from urine and CAN fertiliser applied individually, that is, a multiplicative effect. Nitrous oxide emissions from dung, urine and fertiliser N are typically derived individually and these individual emission estimates are aggregated to produce estimates of N2O emission. The presented findings have important implications for how individual emission factors are aggregated; they suggest that the multiplicative effect of the addition of CAN fertiliser to urine patches needs to be taken into account to refine the estimation of N2O emissions from grazing grasslands.
    • Phosphorus management on Irish dairy farms post controls introduced under the EU Nitrates Directive

      Buckley, Cathal; Wall, David; Moran, Brian; O'Neill, Stephen; Murphy, Paul N. C.; Department of Agriculture, Food and the Marine, Ireland (Elsevier, 08/11/2015)
      The Republic of Ireland was one of a minority of EU member states to include direct controls on chemical phosphorus (P) fertilisers in its EU Nitrates Directive National Action Plan, first introduced in 2006. This study estimates farm gate phosphorus balances and use efficiencies across 150 specialist dairy farms over the seven year period since these controls were introduced (2006–2012) using nationally representative data. Results indicate that P balances declined by 50% over the study period from 11.9 in 2006 to 6.0 kg ha− 1 in 2012. This decline was driven by a reduction in chemical fertiliser imports of 6.5 kg ha− 1. This is equivalent to a reduction of 281 kg of P and represents a cost saving of €812 per annum across the average farm. Phosphorus use efficiency also improved over the period from 60% in 2006 to 78% in 2012, peaking in 2011 at 88.3%. This was achieved while increasing milk solids output per hectare and per cow. Results of a random effects panel data model indicated that P balance and use efficiency are significantly influenced by factors such as fertiliser prices, stocking rates, land use potential, use of milk recording technology, contact with extension services and rainfall patterns.
    • Effects of urease and nitrification inhibitors on yields and emissions in grassland and spring barley

      Forrestal, Patrick J.; Wall, David; Carolan, Rachael; Harty, Mary A.; Roche, Leanne; Krol, Dominika; Watson, C. J.; Lanigan, Gary; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; et al. (International Fertiliser Society, 09/12/2016)
      In trials conducted in the temperate maritime climate of Ireland on a range of acidic soils, calcium ammonium nitrate (CAN) and urea gave comparable yield performance. There was little evidence of reduced yields by using urea for grassland or spring barley. Our finding that urea produced annual yields that were not significantly different from CAN differs from previous studies which found that yields from urea were lower than those from ammonium nitrate or nitrate based fertiliser in the UK. However, there are also published results from trials conducted in temperate Irish grassland showing equal yield performance of CAN and urea in the 1970s. Based on yield performance and the cost of fertiliser there is scope to dramatically increase the level of urea usage in straight and blended fertilisers in the temperate maritime climate of Ireland in both grassland and spring barley. Such an increase will bring substantial benefits in terms of reducing direct nitrous oxide (N2O) emissions from fertiliser applied to soil, particularly in poorly draining soils subject to high levels of precipitation. Nitrogen recovery by plants tends to be more sensitive to differences in fertiliser efficiency than is yield. Although yields did not differ between urea and CAN; urea had a lower nitrogen recovery indicating that urea usage will also result in a reduced level of fertiliser use efficiency. Reduced efficiency is less tangible to farmers who tend to be primarily concerned with dependable yield results. Reduced efficiency is a problem nonetheless, particularly as it is closely linked to NH3 emissions in urea usage. European countries including Ireland have committed to reduce national NH3 emissions to comply with the revised National Emission Ceilings Directive (2001/81/EC) in Europe. Increased urea usage, which looks attractive from a yield, cost and direct N2O perspective in Ireland, runs counter to meeting these commitments. Additionally, NH3 is a source of indirect N2O emissions that will negate some of the N2O savings from urea. Due to the issues of yield dependability, fertiliser efficiency, N2O and NH3 emissions the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) is a particularly attractive option for making urea use more efficient by addressing its key weakness in the area of variable NH3 loss and efficiency. The urease inhibitor NBPT along with the nitrification inhibitor dicyandiamide (DCD) were tested with urea in comparison with calcium ammonium nitrate (CAN). The nitrification inhibitor DCD was very effective in reducing fertiliser N associated N2O emissions. Indeed, its usage allowed N2O levels to be reduced to levels comparable to where no application of N fertiliser was made at some site-years. However, at the DCD incorporation rate tested, DCD contributed to variability in NH3 loss from urea and suppressed both yield response and fertiliser efficiency. Use of the urease inhibitor NBPT in addition to DCD went a substantial way to resolving these shortcomings. Continuing work is needed to tailor the rate of existing and new urease and nitrification inhibitors to optimise the balance between suppression of gaseous N emissions, agronomic performance and economic considerations.
    • 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.
    • Indirect emissions of N2O, CO2 and CH4 via groundwater in contrasting agricultural systems

      Jahangir, Mohammad M. R.; Johnston, Paul; Richards, Karl G.; Irish Research Council; Department of Agriculture, Food and the Marine, Ireland (10/03/2014)
      The dynamics of dissolved carbon (C) and nitrogen (N) in groundwater is a key ‘‘missing piece’’ in our understanding of global C and N balances. In addition, quantification of dissolved nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) in groundwater beneath an agricultural system is of huge importance for global greenhouse gas (GHG) budget estimation. This research aimed to (i) measure the amount of dissolved C and N losses from two terrestrial ecosystems to the aquatic ecosystems via groundwater, and (ii) estimate the contribution of indirect emissions of GHG to the atmosphere.
    • 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.
    • Risk Assessment of E. coli Survival Up to the Grazing Exclusion Period After Dairy Slurry, Cattle Dung, and Biosolids Application to Grassland

      Ashekuzzaman, S.M.; Richards, Karl G.; Ellis, Stephanie; Tyrrel, Sean; O'Leary, Emma; Griffiths, Bryan; Ritz, Karl; Fenton, Owen; European Union; 265269 (Frontiers in Sustainable Food Systems, 10/07/2018)
      Grassland application of dairy slurry, cattle dung, and biosolids offers an opportunity to recycle valuable nutrients (N, P, and K), which may all introduce pathogens to the soil environment. Herein, a temporal risk assessment of the survival of Escherichia coli (E. coli) up to 40 days in line with the legislated grazing exclusion time points after application was examined across six scenarios: (1) soil and biosolids mixture, (2) biosolids amended soil, (3) dairy slurry application, (4) cattle dung on pasture, (5) comparison of scenario 2, 3, and 4, and (6) maximum legal vs. excess rate of application for scenario 2 and 3. The risk model input parameters were taken or derived from regressions within the literature and an uncertainty analysis (n = 1,000 trials for each scenario) was conducted. Scenario 1 results showed that E. coli survival was higher in the soil/biosolids mixture for higher biosolids portion, resulting in the highest 20 day value of residual E. coli concentration (i.e., C20, log10 CFU g−1 dw) of 1.0 in 100% biosolids or inoculated soil and the lowest C20 of 0.098 in 75/25 soil/biosolids ratio, respectively, in comparison to an average initial value of 6.4 log10 CFU g−1 dw. The E. coli survival across scenario 2, 3, and 4 showed that the C20 value of biosolids (0.57 log10 CFU g−1 dw) and dairy slurry (0.74 log10 CFU ml−1) was 2.9–3.7 times smaller than that of cattle dung (2.12 log10 CFU g−1 dw). The C20 values of biosolids and dairy slurry associated with legal and excess application rates ranged from 1.14 to 1.71 log10 CFU ha−1, which is a significant reduction from the initial concentration range (12.99 to 14.83 log10 CFU ha−1). The E. coli survival in un-amended soil was linear with a very low decay rate resulting in a higher C20 value than that of biosolids or dairy slurry. The risk assessment and uncertainly analysis showed that the residual concentrations in biosolids/dairy slurry applied soil after 20 days would be 45–57% lower than that of the background soil E. coli concentration. This means the current practice of grazing exclusion times is safe to reduce the risk of E. coli transmission into the soil environment.