Johnstown Castle is Ireland’s leading research centre for soils and the rural environment. The centre conducts research on soils; nutrient efficiency; recovery and losses; air and water quality; the agricultural environment and agro-ecology. The research results generated are used widely by advisors, farmers, scientists and policy makers.

Recent Submissions

  • Phylogenetic and functional potential links pH and N2O emissions in pasture soils

    Samad, Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecilia A.M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E. (Nature Publishing Group, 2016-10-26)
    Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.
  • Carbon cycling in temperate grassland under elevated temperature

    Jansen-Willems, Anne B.; Lanigan, Gary; Grunhage, Ludger; Muller, Christoph (Wiley, 2016-11-01)
    An increase in mean soil surface temperature has been observed over the last century, and it is predicted to further increase in the future. The effect of increased temperature on ecosystem carbon fluxes in a permanent temperate grassland was studied in a long-term (6 years) field experiment, using multiple temperature increments induced by IR lamps. Ecosystem respiration (R-eco) and net ecosystem exchange (NEE) were measured and modeled by a modified Lloyd and Taylor model including a soil moisture component for R-eco (average R2 of 0.78) and inclusion of a photosynthetic component based on temperature and radiation for NEE (R2 = 0.65). Modeled NEE values ranged between 2.3 and 5.3 kg CO2 m−2 year−1, depending on treatment. An increase of 2 or 3°C led to increased carbon losses, lowering the carbon storage potential by around 4 tonnes of C ha−1 year−1. The majority of significant NEE differences were found during night-time compared to daytime. This suggests that during daytime the increased respiration could be offset by an increase in photosynthetic uptake. This was also supported by differences in δ13C and δ18O, indicating prolonged increased photosynthetic activity associated with the higher temperature treatments. However, this increase in photosynthesis was insufficient to counteract the 24 h increase in respiration, explaining the higher CO2 emissions due to elevated temperature.
  • Can the agronomic performance of urea equal calcium ammonium nitrate across nitrogen rates in temperate grassland?

    Forrestal, Patrick J.; Harty, M.A.; Carolan, R.; Watson, C.J.; Lanigan, Gary; Wall, D.P.; Hennessy, Deirdre; Richards, Karl G. (Wiley, 2017-03-23)
    In temperate grassland, urea has been shown to have lower nitrous oxide emissions compared to ammonium nitrate-based fertilizer and is less expensive. However, nitrogen (N) loss via ammonia volatilization from urea raises questions regarding yield performance and efficiency. This study compares the yield and N offtake of grass fertilized with urea, calcium ammonium nitrate (CAN) and urea treated with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) at six site-years. Five annual fertilizer N rates (100–500 kg N/ha) were applied in five equal splits of 20–100 kg N/ha during the growing season. On average, urea produced slightly better yields than CAN in spring (103.5% of CAN yield) and slightly poorer yields in summer (98.4% of CAN yield). There was no significant difference in annual grass yield between urea, CAN and urea + NBPT. Urea had the lowest cost per tonne of DM grass yield produced. However, the urea treatment had lower N offtake than CAN and this difference was more pronounced as the N rate increased. There was no difference in N offtake between urea + NBPT and CAN. While this study shows that urea produced yields comparable to CAN, urea apparent fertilizer N recovery (AFNR) tends to be lower. Urea selection in place of CAN will increase national ammonia emissions which is problematic for countries with targets to reduce ammonia emissions. Promisingly, NBPT allows the agronomic performance of urea to consistently equal CAN across N rates by addressing the ammonia loss limitations of urea.
  • Gross nitrogen transformations in grassland soil react differently to urea stabilisers under laboratory and field conditions

    Harty, M.A.; McGeough, K.L.; Carolan, R.; Muller, C.; Laughlin, R.J.; Lanigan, Gary; Richards, Karl G.; Watson, C.J. (Elsevier, 2017-02-10)
    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, C.E.; Richards, Karl G.; Jahangir, M.M.R.; Grant, Jim; Mellander, Per-Erik (Elsevier, 2017-02-20)
    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.
  • Ammonia emissions from urea, stabilized urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland

    Forrestal, Patrick J.; Harty, M.; Carolan, R.; Lanigan, Gary; Watson, C.J.; Laughlin, R. J.; McNeill, G.; Chambers, B.J.; Richards, Karl G. (Wiley, 2015-11-17)
    Fertilizer nitrogen (N) contributes to ammonia (NH3) emissions, which European Union member states have committed to reduce. This study focused on evaluating NH3-N loss from a suite of N fertilizers over multiple applications, and gained insights into the temporal and seasonal patterns of NH3-N loss from urea in Irish temperate grassland using wind tunnels. The fertilizers evaluated were calcium ammonium nitrate (CAN), urea and urea with the N stabilizers N-(n-butyl) thiophosphoric triamide (NBPT), dicyandiamide (DCD), DCD+NBPT and a maleic and itaconic acid polymer (MIP). 200 (and 400 for urea only) kg N/ha/yr was applied in five equal applications over the growing season at two grassland sites (one for MIP). Mean NH3-N losses from CAN were 85% lower than urea and had highly variable loss (range 45% points). The effect of DCD on NH3 emissions was variable. MIP did not decrease NH3-N loss, but NBPT caused a 78.5% reduction and, when combined with DCD, a 74% reduction compared with urea alone. Mean spring and summer losses from urea were similar, although spring losses were more variable with both the lowest and highest losses. Maximum NH3-N loss usually occurred on the second day after application. These data highlight the potential of stabilized urea to alter urea NH3-N loss outcomes in temperate grassland, the need for caution when using season as a loss risk guide and that urea hydrolysis in temperate grassland initiates quickly. Micrometeorological measurements focused specifically on urea are needed to determine absolute NH3-N loss levels in Irish temperate grassland.
  • Temperate Grassland Yields and Nitrogen Uptake Are Influenced by Fertilizer Nitrogen Source

    Harty, Mary A.; Forrestal, Patrick J.; Carolan, Rachael; Watson, Catherine J.; Hennessy, Deirdre; Lanigan, Gary; Wall, David P.; Richards, Karl G. (American Society of Agronomy, 2017-01-25)
    In temperate grasslands, N source influences greenhouse gas emissions. Nitrification and urea hydrolysis inhibitors can reduce these losses. The objective of this study was to evaluate the impact of N source, urease inhibitors, and nitrification inhibitors on temperate grassland yields and N uptake. Experiments were conducted at three locations over 2 years (6 site-years) on the island of Ireland, covering a range of soils and climatic conditions. Results showed that calcium ammonium nitrate (CAN), urea+N-(n-butyl) thiophosphoric triamide (NBPT), urea+NBPT+dicyandiamide (DCD), and urea had equal annual dry matter yield. Urea+DCD had lower dry matter yield than CAN for 3 site-years. Calcium ammonium nitrate and urea+NBPT consistently had the same N uptake, urea+DCD had lower N uptake than CAN in 4 of 6 site-years, urea had lower N uptake than CAN in 2 site-years, and urea+NBPT+DCD had lower N uptake than CAN in 1 site-year. Urea+NBPT is a cost-effective alternative to CAN, which is consistently equal in terms of yield and N uptake in temperate grassland.
  • Effects of urease and nitrification inhibitors on yields and emissions in grassland and spring barley

    Forrestal, Patrick J.; Wall, David; Carolan, Rachael; Harty, Mary; Roche, Leanne; Krol, Dominika; Watson, Catherine; Lanigan, Gary; Richards, Karl G. (International Fertiliser Society, 2016-12-09)
    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.
  • Ammonia emissions from cattle dung, urine and urine with dicyandiamide in a temperate grassland

    Fischer, K.; Burchill, W.; Lanigan, Gary; Kaupenjohann, M.; Chambers, B. J.; Richards, Karl G.; Forrestal, Patrick J. (Wiley, 2015-09-03)
    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.
  • An evaluation of urine patch simulation methods for nitrous oxide emission measurement

    Forrestal, Patrick J.; Krol, Dominika; Lanigan, Gary; Jahangir, M.M.R.; Richards, Karl G. (Cambridge University Press, 2016-11-28)
    Global nitrous oxide (N2O) inventory estimates for pasture systems are refined based on measurements of N2O loss from simulated urine patches. A variety of methods are used for patch simulation but they frequently use a uniform wetted area (UWA), often smaller than a bovine urine patch. However, natural patches follow non-uniform infiltration patterns expanding naturally from a point of deposit with a non-wetted zone of influence. Using 2 litres of urine the UWA method was compared, using a 0·156 m2 collar, with a naturally expanding effective area (NEEA) method, using a 0·462 m2 collar under high (HL) and low (LL) N2O loss conditions. The method chosen affects urine nitrogen (N) loading to the soil. Under HL the UWA method induced a N2O-N loss of 280·6 mg/patch, significantly less than the 434·8 mg/patch loss for the NEEA method, for the same simulated urination. Under LL there was no method effect. Efforts should be made to employ patch simulation methods, which mimic natural deposits and can be achieved, at least in part, by: (a) Using a urine volume and N content similar to that of the animal of interest. (b) Allowing natural infiltration of the chosen urine volume to permit tapering towards the edges. (c) Measuring from the zone of influence in addition to the wetted area, i.e. the patch effective area.
  • Digital Soil Mapping in the Irish Soil Information System

    Corstanje, R.; Mayr, T.; Fealy, Reamonn; Zawadzka, J.; Lopapa, G.; Creamer, Rachel E.; Schulte, Rogier P. O. (International Union of Soil Sciences, 2009-12)
    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 by the European Commission and European Environment Agency for reporting on issues relating to soil quality under a fu-ture Soil Framework Directive. Within this context, the Environmental Protection Agency of the Republic of Ireland commissioned a project run by Teagasc to produce a 1:250 000 soil map of the Republic of Ire-land. Delivery of this map and associated database is a collaborative effort between Teagasc, the National Soil Resources Institute at Cranfield in the UK and University College Dublin.
  • Grassland vegetation from three conservation measures

    O'hUallachain, Daire; Finn, John A.; Keogh, Blathnaid; Finch, Rochelle; Sheridan, Helen (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.
  • Mapping Soils in Ireland

    Simo, Iolande; Constanje, R.; Fealy, Reamonn; Hallett, S.; Hannam, J.; Holden, N.; Jahns, G.; Jones, B.; Massey, P.; Mayr, T.; McDonald, E.; Reidy, Brian; Schulte, Rogier P. O.; Sills, P.; Spaargaren, O.; Zawadka, J.; Creamer, Rachel E. (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.
  • Pedotransfer functions for Irish soils – estimation of bulk density (ρb) per horizon type

    Reidy, Brian; Simo, Iolando; Sills, P.; Creamer, Rachel E. (European Geosciences Union, 2016-01-18)
    Soil bulk density is a key property in defining soil characteristics. It describes the packing structure of the soil and is also essential for the measurement of soil carbon stock and nutrient assessment. In many older surveys this property was neglected and in many modern surveys this property is omitted due to cost both in laboratory and labour and in cases where the core method cannot be applied. To overcome these oversights pedotransfer functions are applied using other known soil properties to estimate bulk density. Pedotransfer functions have been derived from large international data sets across many studies, with their own inherent biases, many ignoring horizonation and depth variances. Initially pedotransfer functions from the literature were used to predict different horizon type bulk densities using local known bulk density data sets. Then the best performing of the pedotransfer functions were selected to recalibrate and then were validated again using the known data. The predicted co-efficient of determination was 0.5 or greater in 12 of the 17 horizon types studied. These new equations allowed gap filling where bulk density data were missing in part or whole soil profiles. This then allowed the development of an indicative soil bulk density map for Ireland at 0–30 and 30–50 cm horizon depths. In general the horizons with the largest known data sets had the best predictions, using the recalibrated and validated pedotransfer functions.
  • 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. (European Geosciences Union, 2013-07-12)
    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.
  • 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 A. (Wiley, 2016-06-05)
    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.
  • Yield of temperate forage grassland species is either largely resistant or resilient to experimental summer drought

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

    Fischer, K.; Burchill, W.; Lanigan, Gary; Kaupenjohann, M.; Chambers, B. J.; Richards, Karl G.; Forrestal, Patrick J. (Wiley, 2015-09-03)
    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 resourceefficient approach for refining national ammonia inventories.
  • Ammonia emissions from urea, stabilized urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland

    Forrestal, Patrick J.; Harty, M.; Carolan, R.; Lanigan, Gary; Watson, C.J.; Laughlin, R. J.; McNeil, G.; Chambers, B. J.; Richards, Karl G. (Wiley, 2015-11-17)
    Fertilizer nitrogen (N) contributes to ammonia (NH3) emissions, which European Union member states have committed to reduce. This study focused on evaluating NH3-N loss from a suite of N fertilizers over multiple applications, and gained insights into the temporal and seasonal patterns of NH3-N loss from urea in Irish temperate grassland using wind tunnels. The fertilizers evaluated were calcium ammonium nitrate (CAN), urea and urea with the N stabilizers N-(n-butyl) thiophosphoric triamide (NBPT), dicyandiamide (DCD), DCD+NBPT and a maleic and itaconic acid polymer (MIP). 200 (and 400 for urea only) kg N/ha/yr was applied in five equal applications over the growing season at two grassland sites (one for MIP). Mean NH3-N losses from CAN were 85% lower than urea and had highly variable loss (range 45% points). The effect of DCD on NH3 emissions was variable. MIP did not decrease NH3-N loss, but NBPT caused a 78.5% reduction and, when combined with DCD, a 74% reduction compared with urea alone. Mean spring and summer losses from urea were similar, although spring losses were more variable with both the lowest and highest losses. Maximum NH3-N loss usually occurred on the second day after application. These data highlight the potential of stabilized urea to alter urea NH3-N loss outcomes in temperate grassland, the need for caution when using season as a loss risk guide and that urea hydrolysis in temperate grassland initiates quickly. Micrometeorological measurements focused specifically on urea are needed to determine absolute NH3-N loss levels in Irish temperate grassland.
  • The effect of renovation of long-term temperate grassland on N2O emissions and N leaching from contrasting soils

    Krol, D. J.; Jones, M. B.; Williams, M.; Richards, Karl G.; Bourdin, F.; Lanigan, Gary (Elsevier, 2016-04-19)
    Renovation of long-term grassland is associated with a peak in soil organic N mineralisation which, coupled with diminished plant N uptake can lead to large gaseous and leaching N losses. This study reports on the effect of ploughing and subsequent N fertilisation on the N2O emissions and DON/NO3− leaching, and evaluates the impact of ploughing technique on the magnitude and profile of N losses. This study was carried out on isolated grassland lysimeters of three Irish soils representing contrasting drainage properties (well-drained Clonakilty, moderately-drained Elton and poorly-drained Rathangan). Lysimeters were manually ploughed simulating conventional (CT) and minimum tillage (MT) as two treatments. Renovation of grassland increased N2O flux to a maximum of 0.9 kg N2O–N ha− 1 from poorly-drained soil over four days after treatment. Although there was no difference between CT and MT in the post-ploughing period, the treatment influenced subsequent N2O after fertiliser applications. Fertilisation remained the major driver of N losses therefore reducing fertilisation rate post-planting to account for N mineralised through grassland renovation could reduce the losses in medium to longer term. Leaching was a significant loss pathway, with the cumulative drainage volume and N leached highly influenced by soil type. Overall, the total N losses (N2O + N leached) were lowest from poorly and moderately draining soil and highest for the well draining soil, reflecting the dominance of leaching on total N losses and the paramount importance of soil properties.

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