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Ammonia (NH3) emissions from a range of soil types have been found to differ under laboratory conditions. However, there is lack of studies comparing NH3 emissions from different soil types under field conditions. The objective was to compare NH3 emissions from six different soil types under similar environmental conditions in the field following urea fertiliser application. The study was conducted on a lysimeter unit and NH3 emissions were measured, using wind tunnels, from six different soil types with varying soil characteristics following urea fertiliser application (80 kg N/ha). On average, 17.6% (% total N applied) was volatilised, and there was no significant difference in NH3 emissions across all soil types. Soil variables, including pH, cation exchange capacity and volumetric moisture, were not able to account for the variation in emissions. Further field studies are required to improve the urea-NH3 emission factor used for Ireland’s NH3 inventory.

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. [ABSTRACT FROM AUTHOR]

A small proportion (15–35%) of nitrogen (N) entering pasture-based livestock production systems is converted to tradable agricultural products. The majority of remaining N (surplus N) is largely unaccounted for. While some surplus N is retained in the system, which can be beneficial, most is lost through a range of pathways with potential environmental consequences. The objectives of this study were to (i) account for the N entering a pasture-based dairy production system by determining the amount of N exiting in products and lost to the wider environment and (ii) determine the relative importance of the components of this balance sheet. Detailed measurements and estimates of N entering and exiting a pasture-based dairy production system in Ireland (52°51′N, 08°21′W) was completed in 2011 and 2012. Total N entering and exiting the system was 245 kg ha −1 and 269 kg ha −1 , respectively, averaged over both years. The latter being comprised of N exiting in products: 79 kg ha −1 and losses to the wider environment: 190 kg ha −1 . The N use efficiency of the system was 29% and 37% in 2011 and 2012, respectively. The system N balance (mean ± 95% confidences intervals) was –50 ± 82 kg ha −1 in 2011 and +1 ± 22 kg ha −1 in 2012 and, hence, came close to equality between N entering and existing the system. Of N lost by various pathways, 6.1% was lost to groundwater, 41.6% as ammonia, 8.0% as nitrous oxide and 43.7% as dinitrogen gas. Although N surpluses on pasture based livestock production systems can be substantial, the results of this study suggest that a high proportion of surplus N was lost as environmentally benign dinitrogen gas. This study also highlights that emphasis should be on ammonia and nitrous oxide to minimise environmentally damaging N losses and improve the N-efficiency of such systems of dairy production. [ABSTRACT FROM AUTHOR]

Aims: The objectives of this study were to compare techniques for measuring biological nitrogen fixation (BNF) and to assess how fertiliser N input affects the balance between BNF and sustainable herbage production on perennial ryegrass ( Lolium perenne L.)/white clover ( Trifolium repens L.) grassland. Methods: Biological N fixation and herbage production by white clover based grassland was measured in 2011 and 2012 under four nominal annual fertiliser N inputs: 0 (0N), 86 (86N), 140 (140N) and 280 kg ha (280N). Biological N fixation was measured using the N isotope dilution and N natural abundance techniques under all fertiliser N inputs and also using the nitrogen difference technique under 0N. Results: The two N techniques produced similar annual estimates of above-ground BNF across the range of fertiliser N inputs. Fertiliser N input resulted in higher herbage dry matter yield, but reduced annual BNF which averaged 80, 64, 66 and 47 kg ha on 0N, 86N, 140N and 280N, respectively, across both techniques and years. Conclusions: The two N techniques were comparable in estimating BNF. Intermediate fertiliser N inputs achieved a balance between minimising detrimental impact on BNF and potential N loss while producing more herbage DM yield than clover swards receiving no fertiliser N. [ABSTRACT FROM AUTHOR]

This study investigated changes in soil organic carbon ( SOC) in a poorly drained clay loam soil under (i) permanent grassland ( PG) over 7 years and (ii) after PG renovation over 2·5 years. The experimental area was divided into four blocks with four paddocks per block. Composite soil samples from each PG block were taken to 30-cm depth on five occasions between 2004 and 2011. In June 2008, one paddock per block was renovated by ploughing and reseeding and sampled as above on the latter four occasions. Renovation decreased SOC ( P < 0·05) by 32·2 t ha−1 in the 2·5 years following ploughing; the difference developed almost entirely (86%) in the first four months. Renovation had no effect on above-ground productivity, standing root and stubble phytomass or on dissolved organic matter leaching. Therefore, soil respiration was considered to be a single potential pathway responsible for the SOC loss from renovated grassland. Although a simple linear regression indicated a tendency for PG to accumulate SOC, there was no evidence of recovery in SOC to previous levels following renovation during the study period. These results could have implications for greenhouse gas inventories in countries where PG is an important land-use type. [ABSTRACT FROM AUTHOR]

Highlights • We measured soil nitrous oxide flux, methane flux and soil respiration followiing driange installation. • We measuered water filled pore space (WFPS), soil mineral nitrogen (N), herbage N uptake, soil organic carbon (SOC) and soil total nitrogen (TN) following the installation of mole and gravel mole drainage systems in a clay-loam soil in two experiments over 36 months. • Drainage treatment deepened the water table and decreased WFPS. • Mole and gravel mole drainage had no impact on soil GHG fluxes, soil N mineralisation, soil N nitrification, SOC and TN. Abstract Shallow drainage (e.g. mole and gravel mole drainage installed at 0.55 m below soil surface) is used on pasture-based farms to reduce soil moisture, deepen water table depth and thus increase grass utilization on soils with impeded drainage. There is, however, a lack of research on the effect that these drainage techniques have on soil greenhouse gas (GHG) emissions. Hence the objective of this study was to investigate the effects of mole and gravel mole drainage on soil GHG fluxes. Soil nitrous oxide (N 2 O), soil root respiration (CO 2) and soil methane (CH 4) fluxes were measured in two experiments conducted over a 36 month period. The experiments were conducted on permanent grassland with impeded drainage on a eutric gleysol (humic) in Ireland (52°30′N, 08°12′W). Both experiments were arranged in randomized complete block design. There were three treatments: (i) undrained control, (ii) mole drainage and (iii) gravel mole drainage. Soil GHG fluxes, soil water filled pore space (WFPS) and soil temperature were measured on a weekly basis and soil mineral nitrogen (N), herbage N uptake, soil organic carbon (SOC) and soil total N (TN) were measured seasonally and annually over the sampling period. Drainage treatments (P < 0.05) deepened (mean ± SE) the water table by 0.17±0.03 m and decreased WFPS by 7±0.2%. However no (P > 0.05) impact of drainage treatment was detected on soil average daily GHG fluxes (9.84±6.34g N 2 O-N ha−1day−1, 34.05 ± 12.90 kg CO 2 -C ha−1day−1 and −0.91 ± 3.70 g CH 4 -C ha-1day-1), soil N mineralisation, soil N nitrification, SOC and TN in both experiments. The results indicate that mole and gravel mole drainage can be installed on farms with similar management and soil type to that described in the present study without impact on the soil GHG emissions. [ABSTRACT FROM AUTHOR]

The production of bovine slurry and its subsequent storage are significant sources of ammonia (NH 3) and greenhouse gases (GHGs). Chemical acidification of manures has been shown to significantly reduce these emissions. Waste products, derived from food processing and on-farm practices, may be used as "natural" acidifiers. However, the efficacy of these products in reducing pH and any subsequent emissions are unknown. Commercial "slurry improvers" or "additives" may also be a viable mitigation option; however, their effectiveness is questionable. This study investigated the efficacy and cost of a range of waste and commercial amendments and a chemical acidifier, ferric chloride (FeCl 3), to identify the most effective amendment for NH 3 and GHG emissions reduction. Ammonia abatement potential was observed for 5% sugar beet molasses (67% reduction), 7% apple pulp (49% reduction), and 7% grass silage (38% reduction). Methane (CH 4) emissions were reduced only by spent brewers' grain, sugarbeet molasses, and grass silage effluent at the higher inclusions (i.e. amounts added), with reductions ranging from 15% to 70%. Carbon dioxide (CO 2) emissions were significantly increased with the addition of waste amendments. Commercially available additives had little impact on emissions, with the exception of one treatment, which reduced CH 4 by approximately 10%. Ferric chloride reduced NH 3 emissions by 20%–68%, CH 4 by 6%–65%, and CO 2 by 6%–38%, depending on the inclusion. All waste amendments had low marginal abatement costs ranging from -€0.46 to €0.88 kg−1 NH 3 abated compared to FeCl 3 and commercial amendments (€1.80 to €231 kg−1 NH 3). This incubation experiment demonstrated that a range of on-farm and industry waste streams could be valorised to reduce NH 3 emissions. However, many of these may result in higher CH 4 and CO 2 emissions due to input of labile carbon sources. Therefore, based on the results of the current study, it is recommended that sugarbeet molasses and ferric chloride, at 5% and 1.1% inclusions respectively, be examined in field experiments. [Display omitted] • Farm waste products may be used to reduce NH 3 and GHG emissions. • Ferric chloride and sugarbeet molasses reduced emissions. • A cost saving of ∼ €0.46 kg−1 NH 3 was achieved using waste amendments. • Commercial products were ineffective in abating NH 3 and GHG emissions. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2 O) emissions are subject to intra- and interannual variation due to changes in weather and management. This creates significant uncertainties when quantifying estimates of annual N2 O emissions from grazed grasslands. Despite these uncertainties, the majority of studies are short-term in nature (<1 year) and as a consequence, there is a lack of data on interannual variation in N2 O emissions. The objectives of this study were to (i) quantify annual N2 O emissions and (ii) assess the causes of interannual variation in emissions from grazed perennial ryegrass/white clover grassland. Nitrous oxide emissions were measured from fertilized and grazed perennial ryegrass/white clover grassland (WC) and from perennial ryegrass plots that were not grazed and did not receive N input (GB), over 4 years from 2008 to 2012 in Ireland (52°51'N, 08°21'W). The annual N2 O-N emissions (kg ha(-1); mean ± SE) ranged from 4.4 ± 0.2 to 34.4 ± 5.5 from WC and from 1.7 ± 0.8 to 6.3 ± 1.2 from GB. Interannual variation in N2 O emissions was attributed to differences in annual rainfall, monthly (December) soil temperatures and variation in N input. Such substantial interannual variation in N2 O emissions highlights the need for long-term studies of emissions from managed pastoral systems., (© 2014 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.)