• Management, regulation and environmental impacts of nitrogen fertilization in northwestern Europe under the Nitrates Directive; a benchmark study

      van Grinsven, H. J. M.; ten Berge, H. F. M.; Dalgaard, T.; Fraters, B.; Durand, P.; Hart, A.; Hofman, G.; Jacobsen, B.H.; Lalor, Stanley T. J.; Lesschen, Jan Peter; et al. (European Geosciences Union, 14/12/2012)
      Implementation of the Nitrates Directive (NiD) and its environmental impacts were compared for member states in the northwest of the European Union (Ireland, United Kingdom, Denmark, the Netherlands, Belgium, Northern France and Germany). The main sources of data were national reports for the third reporting period for the NiD (2004–2007) and results of the MITERRA-EUROPE model. Implementation of the NiD in the considered member states is fairly comparable regarding restrictions for where and when to apply fertilizer and manure, but very different regarding application limits for N fertilization. Issues of concern and improvement of the implementation of the NiD are accounting for the fertilizer value of nitrogen in manure, and relating application limits for total nitrogen (N) to potential crop yield and N removal. The most significant environmental effect of the implementation of the NiD since 1995 is a major contribution to the decrease of the soil N balance (N surplus), particularly in Belgium, Denmark, Ireland, the Netherlands and the United Kingdom. This decrease is accompanied by a modest decrease of nitrate concentrations since 2000 in fresh surface waters in most countries. This decrease is less prominent for groundwater in view of delayed response of nitrate in deep aquifers. In spite of improved fertilization practices, the southeast of the Netherlands, the Flemish Region and Brittany remain to be regions of major concern in view of a combination of a high nitrogen surplus, high leaching fractions to groundwater and tenacious exceedance of the water quality standards. On average the gross N balance in 2008 for the seven member states in EUROSTAT and in national reports was about 20 kg N ha−1 yr−1 lower than by MITERRA. The major cause is higher estimates of N removal in national reports which can amount to more than 50 kg N ha−1 yr−1. Differences between procedures in member states to assess nitrogen balances and water quality and a lack of cross-boundary policy evaluations are handicaps when benchmarking the effectiveness of the NiD. This provides a challenge for the European Commission and its member states, as the NiD remains an important piece of legislation for protecting drinking water quality in regions with many private or small public production facilities and controlling aquatic eutrophication from agricultural sources.
    • Mapping Soils in Ireland

      Simo, Iolanda; Constanje, R.; Fealy, Reamonn; Hallett, S.; Hannam, Jacqueline; Holden, Nicholas M.; Jahns, G.; Jones, B.; Massey, P.; Mayr, T.; et al. (CRC Press, 2014)
      Harmonised soil data across Europe with a 1:250 000 geo-referenced soil database will allow for exchange of data across member states and the provide the information needed for reporting on issues re-lating to soil quality under a future Soil Framework Directive. The current status of soils data available in Eu-rope is inconsistent at best. The Irish Soil Information System (ISIS) project is currently developing a national soil map of 1:250,000 and an associated digital soil information system, providing both spatial and quantita-tive information on soil types and properties across Ireland. Both the map and the information system will be freely available to the public through a designated website.
    • Mapping the broad habitats of the Burren using satellite imagery

      Parr, Sharon; O'Donovan, Grace; Finn, John (Teagasc, 01/03/2006)
      This project has successfully used satellite imagery to survey and map the extent and spatial distribution of broad habitat types within the Burren, and we have represented this information on a digitised habitat map. this information on a digitised habitat map. This map is the first to show the distribution of the broad habitats of the Burren and will be an important tool in aiding future decisions as to how the habitats of the Burren should be managed to the benefit of both the farmer and the environment. The map provides the first estimate of the area of the Burren affected by scrub encroachment – this being one of the most significant threats to the EU priority habitats in the region. On a particularly challenging area with a high diversity and complexity of habitats, remote sensing appears to offer a very effective and cost-efficient alternative to broad-scale habitat mapping on a field-by-field basis. The use of high-resolution imagery and ground-truthing should be adopted to complete a detailed national survey of habitats and land use in Ireland. This would support more effective implementation of both the Agriculture sector’s obligations under the Habitats Directive, and agri-environmental schemes with wildlife objectives. The outputs provided by such mapping approaches could inform the targeting of agri-environmental objectives, and increase the efficiency of detecting areas of high conservation value for monitoring by more conventional methods. The detailed land use descriptions offered by such imagery are also of high relevance to modelling approaches and risk assessment for implementation of land use policies such as the Water Framework Directive and Nitrates Directive.
    • Measured and Simulated Nitrous Oxide Emissions from Ryegrass- and Ryegrass/White Clover-Based Grasslands in a Moist Temperate Climate

      Li, Dejun; Lanigan, Gary; Humphreys, James; Department of Agriculture, Food and the Marine, Ireland; RSF 07 516; RSF 07 511 (PLoS, 10/10/2011)
      There is uncertainty about the potential reduction of soil nitrous oxide (N2O) emission when fertilizer nitrogen (FN) is partially or completely replaced by biological N fixation (BNF) in temperate grassland. The objectives of this study were to 1) investigate the changes in N2O emissions when BNF is used to replace FN in permanent grassland, and 2) evaluate the applicability of the process-based model DNDC to simulate N2O emissions from Irish grasslands. Three grazing treatments were: (i) ryegrass (Lolium perenne) grasslands receiving 226 kg FN ha−1 yr−1 (GG+FN), (ii) ryegrass/white clover (Trifolium repens) grasslands receiving 58 kg FN ha−1 yr−1 (GWC+FN) applied in spring, and (iii) ryegrass/white clover grasslands receiving no FN (GWC-FN). Two background treatments, un-grazed swards with ryegrass only (G–B) or ryegrass/white clover (WC–B), did not receive slurry or FN and the herbage was harvested by mowing. There was no significant difference in annual N2O emissions between G–B (2.38±0.12 kg N ha−1 yr−1 (mean±SE)) and WC-B (2.45±0.85 kg N ha−1 yr−1), indicating that N2O emission due to BNF itself and clover residual decomposition from permanent ryegrass/clover grassland was negligible. N2O emissions were 7.82±1.67, 6.35±1.14 and 6.54±1.70 kg N ha−1 yr−1, respectively, from GG+FN, GWC+FN and GWC-FN. N2O fluxes simulated by DNDC agreed well with the measured values with significant correlation between simulated and measured daily fluxes for the three grazing treatments, but the simulation did not agree very well for the background treatments. DNDC overestimated annual emission by 61% for GG+FN, and underestimated by 45% for GWC-FN, but simulated very well for GWC+FN. Both the measured and simulated results supported that there was a clear reduction of N2O emissions when FN was replaced by BNF.
    • A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation

      Vero, Sara E.; Healy, Mark G.; Henry, Tiernan; Creamer, Rachel E.; Ibrahim, Tristan G.; Forrestal, Patrick J.; Richards, Karl G.; Fenton, Owen; Teagasc Walsh Fellowship Programme (Teagasc (Agriculture and Food Development Authority), Ireland, 30/12/2016)
      During laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.
    • Methodological tests of the use of trace elements as tracers to assess root activity

      Hoekstra, Nyncke J.; Finn, John; Buchmann, Nina; Gockele, A.; Landert, L.; Prill, N.; Scherer-Lorenzen, M.; Luscher, L.; European Union; Irish Research Council; et al. (Springer, 2014-03)
      Background and aims There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species. Methods We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method. Results The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method. Conclusions The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.
    • Methodology for environmental assessment of agri-environment schemes: the Agri Environmental Footprint Index

      Finn, John; Louwagie, G.; Northey, G.; Purvis, Gordon; Balazs, K.; Mortimer, S.R.; Primdahl, J.; Vesterager, J.-P.; AE-Footprint project (Teagasc, 01/11/2010)
      Agri-environment schemes pay farmers for the provision of environmental services. Such schemes tend to have multiple measures that deliver multiple environmental objectives, and there is a lack of consistent methodology with which to measure the environmental benefits of such schemes. Funded by EU FP6, the Agri-Environment Footprint project (www.footprint.rdg.ac.uk) aimed to address this challenge, and this report provides results from selected components of the project.
    • Methodology for the location of a subsurface permeable reactive barrier for the remediation of point source pollution on an Irish farm

      Fenton, Owen; Healy, Mark G.; Richards, Karl G. (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2008)
      Nutrient loss from agricultural sources to water continues to be a national challenge. Diffuse pollution from agricultural sources is considered to be the primary cause of slight-to-moderate water pollution in Ireland, but agricultural point sources, such as farmyards, are often not considered due to their scattered spatial distribution and small areal extent. Agricultural point sources tend to be small and localised hot spots of nutrients and, therefore, can be efficiently treated using environmental technologies developed for wastewater and contaminated land treatment. A small area associated with soiled water irrigation, on a 4.27 ha case study site at Teagasc, Johnstown Environmental Research Centre, Ireland, was identified, where groundwater nitrate-nitrogen (NO3-N) concentration exceeds the maximum admissible drinking water concentration of 11.3 mg N L-1. A continuous, shallow permeable reactive barrier may be suitable to remediate point source pollution at this site. A methodology, based on site and groundwater characterisation, successfully located a site for a permeable reactive barrier.
    • Mid-infrared spectroscopy as an alternative to laboratory extraction for the determination of lime requirement in tillage soils

      Metzger, Konrad; Zhang, Chaosheng; Ward, Mark; Daly, Karen; Teagasc Walsh Fellowship Programme; Department for Agriculture Food and the Marine; RMIS 6837; 15/ICTAGRI 2 (Elsevier BV, 2020-04)
      Lime is a crucial soil conditioner to bring agricultural soils to optimum pH values for nutrient availability. Lime recommendations are typically determined in laboratory extractions, the most common being the “Shoemaker- McLean and Pratt” (SMP) buffer method, that requires carcinogenic reagents soon to be abolished under the EU legislation. As an alternative to wet chemistry, mid-infrared (MIR) spectroscopy has shown to be a cost-and time effective method at predicting soil properties. The capability and feasibility of diffuse reflectance infrared spectroscopy (DRIFTS) to predict lime requirement (LR) in tillage fields is examined. Samples from 41 cereal tillage fields (n = 655) are used to build a calibration for DRIFTS using partial least squares regression (PLSR). The samples were split into calibration set (31 fields, n=495) and validation set (10 fields, n= 160). After preprocessing with trim, smoothing and standard normal variate, a calibration model using 6 latent variables, provided R2 of 0.89 and root mean square error of cross-validation (RMSECV) of 1.56 t/ha. Prediction of all fields from the validation set resulted in R2 of 0.76 and root mean square error of prediction (RMSEP) of 1.68 t/ ha. The predictions of the single fields ranged from R2 values of 0.41 to 0.72, RMSEP of 0.48 to 4.2 t/ha and ratios of performance to inter-quartile distance (RPIQ) of 0.45 to 3.56. It was shown that the signals of soil constituents having an influence on the LR were picked up in the spectra and were identified in the loading weights of the PLSR. While the error is too high to predict the variability of LR within the field, MIR prediction using field averages provided a viable alternative to current laboratory methods for blanket spreading of lime on tillage fields.
    • 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.
    • Modelling Phosphorus for Grassland: Agronomically and Environmentally Sustainable Advice

      Schulte, Rogier P. (Teagasc, 01/01/2006)
      In 2006, the Nitrates Directive (through S.I. 378 (Anon, 2006)) was implemented in Ireland, aimed at reducing nutrient losses from agriculture to water bodies, i.e. surface waters, groundwater and estuarine waters. This legislation introduced strict regulation of nutrient management on Irish farms. Thus far, nutrient management had largely been based on Teagasc advice (Coulter, 2004). However, in the new policy climate, in addition to advice, compliance with legal limits is also required. This significant change in the practicalities surrounding nutrient management led to a review of Teagasc nutrient (phosphorus and nitrogen) advice, based on the following considerations: Traditionally, nutrient advice had largely been based on fertiliser rates for economically optimal productivity, i.e. rates at which further fertiliser applications would not result in higher economic returns. Now, SI 378 of 2006 demands that nutrient application rates do not exceed crop (grass) demand, nor result in nutrient losses that may have a negative impact on water quality. Previous phosphorus (P) advice (Coulter, 2004) was similar for all soil types, and did not account for potentially different P-requirements, or indeed potentially different risks of P-loss to water between soils. Previous P advice was based on returning optimum crop yields. However, grassland management in Ireland is increasingly focussed on maximising the amount of herbage grazed in situ. With extended grazing seasons and an increasing share of the animal diet consisting of grazed herbage, the scope and flexibility of diet supplementation through straights and concentrates is reduced. An increasing proportion of dietary P must be obtained from this grazed herbage as a result. Therefore P fertiliser strategies should no longer be based on yield responses alone, but in addition sustain adequate herbage P-concentrations in order to ensure that the dietary P requirements can be met on a non-supplemented diet of grazed herbage. Against this background, Teagasc, Johnstown Castle Environment Research Centre, undertook a major research programme, reviewing both agronomic and environmental aspects of P-advice for grassland.
    • Modelling soil bulk density at the landscape scale and its contributions to C stock uncertainty

      Taalab, K.P.; Corstanje, R.; Creamer, Rachel E.; Whelan, M. J.; Environmental Protection Agency (European Geosciences Union, 12/07/2013)
      Soil bulk density (Db) is a major contributor to uncertainties in landscape-scale carbon and nutrient stock estimation. However, it is time consuming to measure and is, therefore, frequently predicted using surrogate variables, such as soil texture. Using this approach is of limited value for estimating landscape-scale inventories, as its accuracy beyond the sampling point at which texture is measured becomes highly uncertain. In this paper, we explore the ability of soil landscape models to predict soil Db using a suite of landscape attributes and derivatives for both topsoil and subsoil. The models were constructed using random forests and artificial neural networks. Using these statistical methods, we have produced a spatially distributed prediction of Db on a 100 m × 100 m grid, which was shown to significantly improve topsoil carbon stock estimation. In comparison to using mean values from point measurements, stratified by soil class, we found that the gridded method predicted Db more accurately, especially for higher and lower values within the range. Within our study area of the Midlands, UK, we found that the gridded prediction of Db produced a stock inventory of over 1 million tonnes of carbon greater than the stratified mean method. Furthermore, the 95% confidence interval associated with total C stock prediction was almost halved by using the gridded method. The gridded approach was particularly useful in improving organic carbon (OC) stock estimation for fine-scale landscape units at which many landscape–atmosphere interaction models operate.
    • Multiple factors control the environmental effectiveness of agri-environment schemes: implications for design and evaluation

      Finn, John; Kurz, Isabelle; Bourke, David; European Union; European Commission; SSPE-CT-2003-502070 (School of Agriculture, Food Science and Veterinary Medicine, University College Dublin in association with Teagasc, 2008)
      Achieving and evaluating the environmental effectiveness of agri-environment schemes (AESs) has proven difficult. The design and ex ante evaluation of AESs is a crucial phase for ensuring effectiveness, but seems to receive relatively little attention. We propose a programme theory (a structured description of the various cause-and-effect relationships that underpin and achieve a policy initiative) for AESs that considers multiple factors that drive environmental performance at farm-scale (appropriate farm-level objectives, farmer compliance, implementation by institutions, and cause-and-effect relationship between management prescriptions and environmental objectives), and factors that determine how farm-scale performance aggregates to produce scheme-scale performance (participation rate, targeting, and threshold effects). These factors can be used as assessment criteria with which to pinpoint specific causes of AES failure, and thereby offer a practical approach to complement the design and evaluation of the environmental effects of AESs.
    • Mustard catch crop enhances denitrification in shallow groundwater beneath a spring barley field

      Jahangir, Mohammad M. R.; Minet, E.; Johnston, Paul; Premrov, Alina; Coxon, Catherine E.; Hackett, Richard; Richards, Karl G.; Department of Agriculture, Food and the Marine, Ireland; RSF 06383 (Elsevier, 26/12/2013)
      Over-winter green cover crops have been reported to increase dissolved organic carbon (DOC) concentrations in groundwater, which can be used as an energy source for denitrifiers. This study investigates the impact of a mustard catch crop on in situ denitrification and nitrous oxide (N2O) emissions from an aquifer overlain by arable land. Denitrification rates and N2O-N/(N2O-N + N2-N) mole fractions were measured in situ with a push–pull method in shallow groundwater under a spring barley system in experimental plots with and without a mustard cover crop. The results suggest that a mustard cover crop could substantially enhance reduction of groundwater nitrate NO3--N via denitrification without significantly increasing N2O emissions. Mean total denitrification (TDN) rates below mustard cover crop and no cover crop were 7.61 and 0.002 μg kg−1 d−1, respectively. Estimated N2O-N/(N2O-N + N2-N) ratios, being 0.001 and 1.0 below mustard cover crop and no cover crop respectively, indicate that denitrification below mustard cover crop reduces N2O to N2, unlike the plot with no cover crop. The observed enhanced denitrification under the mustard cover crop may result from the higher groundwater DOC under mustard cover crop (1.53 mg L−1) than no cover crop (0.90 mg L−1) being added by the root exudates and root masses of mustard. This study gives insights into the missing piece in agricultural nitrogen (N) balance and groundwater derived N2O emissions under arable land and thus helps minimise the uncertainty in agricultural N and N2O-N balances.
    • N leaching to groundwater from dairy production involving grazing over the winter on a clay-loam soil

      Necpalova, Magdalena; Fenton, Owen; Casey, Imelda A.; Humphreys, James; Department of Agriculture, Food and the Marine, Ireland; RSF07-511 (Elsevier B. V., 15/08/2012)
      This study investigated concentrations of various N species in shallow groundwater (< 2.2 m below ground level) and N losses from dairy production involving grazing over the winter period on a clay loam soil with a high natural attenuation capacity in southern Ireland (52˚51’N, 08˚21’W) over a two year period. A dense network of shallow groundwater piezometers was installed to determine groundwater flow direction and N spatial and temporal variation. Estimated vertical travel times through the unsaturated zone (<0.5 yr, time lag) allowed the correlation of management with groundwater N within a short space of time. There was a two way interaction of the system and sampling date (P < 0.05) on concentrations of DON, oxidised N and NO3--N. In contrast, concentrations of NH4+-N and NO2--N were unaffected by the dairy system. Grazing over the winter had no effect on N losses to groundwater. Mean concentrations of DON, NH4+-N, NO2--N and NO3--N were 2.16, 0.35, 0.01 and 0.37 mg L-1 respectively. Soil attenuation processes such as denitrification and DNRA resulted in increased NH4+-N levels. For this reason, DON and NH4+-N represented the highest proportion of N losses from the site. Some of the spatial and temporal variation of N concentrations was explained by correlations with selected chemical and hydro-topographical parameters (NO3--N/Cl- ratio, distance of the sampling point from the closest receptor, watertable depth, depth of sampling piezometer, DOC concentration). A high explanatory power of NO3--N/Cl- ratio and the distance of the sampling point from the closest receptor indicated the influence of point sources and groundwater-surface water interactions.
    • National Soils Database

      Fay, Deirdre; McGrath, David; Zhang, Chaosheng; Carrigg, Cora; O'Flaherty, Vincent; Kramers, Gaelene; Carton, Owen T.; Grennan, Eamonn J. (Teagasc, 01/07/2007)
      The objectives of the National Soils Database project were fourfold. The first was to generate a national database of soil geochemistry to complete the work that commenced with a survey of the South East of Ireland carried out in 1995 and 1996 by Teagasc (McGrath and McCormack, 1999). Secondly, to produce point and interpolated spatial distribution maps of major, minor and trace elements and to interpret these with respect to underlying parent material, glacial geology, land use and possible anthropogenic effects. A third objective was to investigate the microbial community structure in a range of soil types to determine the relationship between soil microbiology and chemistry. The final objective was to establish a National Soils Archive.
    • Nitrogen fertiliser interactions with urine deposit affect nitrous oxide emissions from grazed grasslands

      Maire, J.; Krol, Dominika; Pasquier, D.; Cowan, N.; Skiba, U.; Rees, R.M.; Reay, D.; Lanigan, Gary; Richards, Karl J.; Teagasc Walsh Fellowship Programme; et al. (Elsevier, 2019-12-06)
      Cattle excreta deposited on grazed pastures are responsible for one fifth of the global anthropogenic nitrous oxide (N2O) emissions. One of the key nitrogen (N) sources is urine deposited from grazing animals, which contributes to very large N loadings within small areas. The main objective of this plot study was to establish whether the application of N fertiliser and urine deposit from dairy cows synergistically interacts and thereby increases N2O emissions, and how such interaction is influenced by the timing of application. The combined application of fertiliser (calcium ammonium nitrate) and urine significantly increased the cumulative N2O emissions as well as the N2O emission factor (EF) from 0.35 to 0.74 % in spring and from 0.26 to 0.52 % in summer. By contrast, EFs were lower when only fertiliser (0.31 % in spring, 0.07 % in summer) or urine was applied (0.33 % in spring, 0.28 % in summer). In autumn, N2O emissions were larger than in other seasons and the emissions from the combined application were not statistically different to those from either the separately applied urine or N fertiliser (EF ranging from 0.72 to 0.83, p-value < 0.05). The absence of significant synergistic effect could be explained by weather conditions, particularly rainfall during the three days prior to and after application in autumn. This study implies that the interactive effects of N fertilisation and urine deposit, as well as the timing of the application on N2O emission need to be taken into account in greenhouse gas emission inventories.
    • Nitrogen fertilisers with urease inhibitors reduce nitrous oxide and ammonia losses, while retaining yield in temperate grassland

      Krol, Dominika; Forrestal, P. J.; Wall, David P.; Lanigan, G. J.; Sanz-Gomez, J.; Richards, K. G.; Irish Research Council; EPSPD/2016/54 (Elsevier, 2020-04-02)
      Nitrogen fertilisation, although a cornerstone of modern agricultural production, negatively impacts the environment through gaseous losses of nitrous oxide (N2O), a potent greenhouse gas (GHG), and ammonia (NH3), a known air pollutant. The aim of this work was to assess the feasibility of urea treated with urease inhibitors to reduce gaseous N losses in temperate grassland, while maintaining or improving productivity compared to conventional fertiliser formulations. Urease inhibitors were N-(n-butyl)-thiophosphoric triamide (NBPT) (urea + NBPT) and N-(n-propyl)-thiophosphoric triamide (NPPT) (urea+ NBPT + NPPT), while conventional fertilisers were urea and calcium ammonium nitrate (CAN). N2O emission factors were 0.06%, 0.07%, 0.09% and 0.58% from urea + NBPT, urea, urea + NBPT + NPPT and CAN, respectively, with CAN significantly higher than all the urea formulations, which were not significantly different from each other. Ammonia loss measured over one fertiliser application was significantly larger from urea, at 43%, compared with other formulations at 13.9%, 13.8% and 5.2% from urea + NBPT, urea + NBPT + NPPT and CAN, respectively. Changing fertiliser formulation had no significant impact on grass yield or N uptake in four out of five harvests. In the last harvest urea + NBPT significantly out-yielded urea, but not CAN or urea + NBPT + NPPT. Overall, urea treated with either one or both urease inhibitors significantly reduced emissions of N2O and NH3, while preserving yield quantity and quality. Therefore, changing fertiliser formulation to these products should be encouraged as a strategy to reduce GHG and air pollution from agricultural practices in temperate climate.
    • Nitrogen yield advantage from grass-legume mixtures is robust over a wide range of legume proportions and environmental conditions

      Suter, Matthias; Connolly, John; Finn, John; Loges, R.; Kirwan, Laura; Sebastia, Maria Teresa; Luscher, A.; European Union (Wiley, 28/01/2015)
      Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self-sufficiency through home-grown crops, and reduced N losses to the environment. 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 of 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 legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures.Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture 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 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 thus greenhouse gas emissions and a considerable potential for climate change mitigation.
    • Nitrous Oxide Emissions

      Hyde, Bernard; Ryan, Mary; Hawkins, M.; Connolly, John; Carton, Owen T.; Environmental Protection Agency (Teagasc, 01/04/2005)
      Nitrous oxide (N2O) is one of the three most important greenhouse gases (GHG). Nitrous oxide emissions currently account for approximately one third of GHG emissions from agriculture in Ireland. Emissions of N2O arise naturally from soil sources and from the application of nitrogen (N) in the form of N fertilizers and N in dung and urine deposition by grazing animals at pasture. Nitrous oxide emission measurements were conducted at three different scales. Firstly, a large-scale field experiment was undertaken to compare emission rates from a pasture receiving three different rates of N fertilizer application and to identify the effects of controlling variables over a two-year period. Variation in emission rates was large both within and between years. Two contrasting climatic years were identified. The cooler and wetter conditions in year 1 gave rise to considerably lower emission levels than the warmer and drier year 2. However, in both years, peak emissions were associated with fertilizer N applications coincident with rainfall events in the summer months. A small-plot study was conducted to identify the individual and combined effects of fertilizer, dung and urine applications to grassland. Treatment effects were however, difficult to obtain due to the overriding effects of environmental variables. Thirdly, through the use of a small-scale mini-lysimeter study, the diurnal nature of N2O emission rates was identified for two distinct periods during the year. The occurrence of a diurnal pattern has important implications for the identification of a measurement period during the day which is representative of the true daily flux. The research presented aims to identify the nature and magnitude of N2O emissions and the factors which affect emission rates from a grassland in Ireland. Further work is required to integrate the effects of different soil types and contrasting climatic regimes across soil types on N2O emissions.