Increased emissions of nitric oxide and nitrous oxide following tillage of a perennial pasture

About 40% of the agricultural land in the European Union (EU) is grassland used for animal production. When grassland is tilled, organically bound carbon and nitrogen are released, providing substrates for nitrifying and denitrifying microorganisms. The aim of this study was to examine the immediate effects of tillage of a perennial grassland carried out on different dates, on the emissions of nitric oxide (NO) and nitrous oxide (N₂O), monitored intensively over a 5-day period, in a humid, dairy farming area of northern Spain. Soil was tilled 12 days and 2 days prior to fertiliser application. Tillage, time of tillage, and N fertiliser application affected NO and N₂O emissions. Tillage 12 days before the start of the flux measurements resulted in higher emissions than tillage one day before, the difference being related to differences in soil mineral N and water-filled pore space (WFPS). Emissions of NO peaked at a WFPS of 50–60%, while N₂O fluxes peaked at 70–90% WFPS. Loss of N was greater as N₂O than as NO. The total loss of N as N₂O plus NO ranged from 0.027 kg N ha^–1 in unfertilised plots to 0.56 kg N ha^–1 in the tilled and N fertilised plot. Thereafter emissions decreased rapidly to low values. The results of this study indicate that tillage of perennial grassland may release large amounts of NO and N₂O, the amounts also depending on moisture conditions and addition of N fertiliser. We suggest that in order to reduce such emissions, application of N fertiliser should not immediately follow tillage of perennial grassland, as there is an extra supply of N from mineralisation of organic matter at this time.     

The effect of biological oxygen demand of cattle slurry and soil moisture on nitrous oxide emissions

The application of animal manure slurries to soils may cause high short-term emissions of nitrous oxide (N₂O). We performed studies on N₂O emissions varying the contents of NH₄-N and microbial available organic carbon (measured as biological oxygen demand, BOD) of cattle slurry. Additionally the effect of slurry BOD on N₂O emissions at different soil water contents (35, 54, 71% water filled pore space, WFPS) was studied. Slurries from an anaerobic digestion plant (digested slurry, BOD: 1.2 g O₂ l⁻¹) or untreated slurry (BOD: 6.8 g O₂ l⁻¹) were applied at 30 m³ ha⁻¹ and incubated at 20°C. The higher the WFPS the more N₂O was emitted independent from the type of slurry applied. At low and medium soil water contents, the digested slurry induced significantly lower N₂O emissions than the untreated slurry. The N₂O emissions were directly correlated with the BOD content of the slurry (R ²=0.61, P≤0.001). We also compared the effect of NH₄-N concentration and BOD on emissions from the slurries at 54% WFPS. Again the BOD had a significant influence on N₂O emissions but a reduction of NH₄-N had no effect on the amount of N₂O emitted. The microbially available organic carbon seems to determine the amount of N₂O emitted shortly after slurry application. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of soil physical properties, fertiliser type and moisture tension on N2O and NO emissions from nearly saturated Japanese upland soils

In Japan, upland soils are an important source of nitrous oxide (N₂O) and nitric oxide (NO) gas emissions. This paper reports on an investigation of the effect of soil moisture near saturation on N₂O and NO emission rates from four upland soils in Japan of contrasting texture. The aim was to relate these effects to soil physical properties. Intact cores of each soil type were incubated in the laboratory at different moisture tensions after fertilisation with NH₄-N, NO₃-N or zero N. Emissions of N₂O and NO were measured regularly over a 16–20 day period. At the end of the incubation, soil cores were analysed for physical properties. Moisture and N fertiliser significantly affected rates of emissions of both N₂O and NO with large differences between the soil types. Nitrous oxide emissions were greatest in the finer-textured soils, whereas NO emissions were greater in the coarser-textured soils. Emissions of N₂O increased at higher moisture contents in all soils, but the magnitude of increase was much greater in finer-textured soils. Nitric oxide emissions were only significant in soils fertilised with NH₄-N and were negatively correlated with soil moisture. Analysis of soil properties showed that there was a strong relationship between the magnitude of emissions and soil physical properties. The importance of soil wetness to gas emissions was mainly through its influence on soil air-filled porosity, which itself was related to gas diffusivity. From the results of this research, we can now estimate likely effects of soil texture on emissions through the influence of soil type on soil aeration and soil drainage. This is of particular value in modelling N₂O and NO emissions from soil moisture status and land use inputs.     

The effect of soil moisture on mineral nitrogen, soil electrical conductivity, and pH

Inorganic nitrogen in the soil is the source of N for non-legume plants. Rapid methods for monitoring changes in inorganic N concentrations would be helpful for N nutrient management. The effect of varying soil moisture content on soil mineral nitrogen, electrical conductivity (EC), and pH were studied in a laboratory experiment. Soil NO₃-N increased as soil water-filled pore space (WFPS) increased from 0 to 80 cm³ cm^–3. At soil moisture levels greater than 80 cm³ cm^–3, NO₃-N concentration declined rapidly and NH₄-N concentration increased, likely due to anaerobic conditions existing at higher WFPS levels. Soil pH did not change as soil moisture increased from 100 g kg^–1 to 400 g kg^–1 and increased from 6.2 to 6.6 at higher levels of soil moisture. Soil EC was correlated with soil mineral N concentration when measured in situ with a portable EC meter (R ²=0.85) or in the laboratory as 1:1 soil water slurries (R ²=0.92). Results suggest that EC can be used to rapidly detect changes in soil inorganic N status in soils where salts and free carbonates are not present in large amounts.     

Quantification of N-losses as NH3, NO, and N2O and N2 from fertilized maize fields in southwestern France

Emissions of nitrogen compounds (NO, NH₃, N₂O and N₂) from heavily fertilized (280 kg(N) ha^-1) and irrigated maize fields were studied over an annual cultivation cycle in southwestern France. NO and N₂O emissions were measured by chamber techniques throughout the year. During fertilization and maize growth periods, chamber measurements were intensified and complemented by flux-gradient micrometeorological measurements of NO_x and NH₃. The two methods used, Bowen ratio and a simplified aerodynamical techniques, agree quite well and quantify NO_x and NH₃ flux variations during the period of intense emission which followed fertilizer application. Over a yearly cycle, nitrogen loss in the form of NH₃, NO and N₂O were calculated using micrometeorological flux measurements and emission algorithms calibrated with field data (chambers). The soil denitrification potential represented by the ratio N₂O/(N₂O+N₂) was measured in the laboratory to calculate potential total gaseous nitrogen loss. Taking into account all uncertainties, the total N loss into the atmosphere represents 30 to 110 kg(N) ha^-1 with about less than 1% as NH₃, 40% as NO, 14% as N₂O and 46% as N₂. This is in agreement with the agronomic nitrogen budget based on the N fertilizer input and soil furniture and, on the N-output by crops and crop residues, which displays a net imbalance of 50 to 100 kg(N) ha^-1.     

Predicting nitrous oxide emissions from N-fertilized grassland soils in the UK from three soil variables,using the B-LINE 2 model

Emissions of nitrous oxide (N₂O) from N-fertilized silage grassland in the UK were modelled with a hybrid part-empirical part-mechanistic model, B-LINE 2. N₂O fluxes were predicted from combinations of three soil variables: soil water-filled pore space (WFPS), soil temperature (T) and soil mineral N content (N_min). Pooled field “training” data from several sites and seasons were used to parameterise the model. N₂O fluxes were assigned one of three values: the geometric means of the ranges 1–10, 10–100 and 100–1,000 g N₂O-N ha^?1 day^?1, respectively, depending on threshold lines (a) relating flux and N_min and (b) relating flux, WFPS and T. The model was applied to give daily and seasonal total fluxes, and the overall relationships with measured emissions from ammonium nitrate treatments were analysed separately for those site-seasons not used as a source of training data, for the training data site-seasons, and for all site-seasons together. Results for both training and non-training site-seasons showed, with some exceptions, reasonable agreement with experimental measurements in the timings of main emission peaks, and also in the magnitude of daily flux rate variations over time. Generally, modelled seasonal N₂O emissions were somewhat higher than measured values, possibly because at very high WFPS values the actual N₂O flux was lower than predicted as a result of greater reduction of nitrate to N₂, rather than release as N₂O. However, one site was an outlier, with predicted emissions much lower than those observed. Overall, the modelling results compared well with those obtained elsewhere with other models.     

Emissions of nitrous oxide from boreal agricultural clay and loamy sand soils

Long-term studies of greenhouse gas fluxes from agricultural soils in different climate regions are needed to improve the existing calculation models used in greenhouse gas inventories. The aim of this study was to obtain more information on nitrous oxide (N₂O) emissions from agricultural mineral soils in the boreal region. N₂O emissions were studied during 2000–2002 on two soil types in Finland, a loamy sand and a clay with plots of grass, barley and fallow. N₂O fluxes were measured with static chambers throughout the year. Other parameters measured were water filled pore space (WFPS), soil mineral nitrogen concentration, soil porosity, soil temperature and depth of soil frost. The annual fluxes from the clay soil ranged from 3.7 to 7.8 kg N ha^–1 and those from sandy loam from 1.5 to 7.5 kg N ha^–1. On average 60% of the annual fluxes occurred outside the growing season, from October to April. Increasing the number of freeze-thaw events was found to increase the fluxes during winter and during the thawing period in spring. The results suggest that N₂O fluxes from these boreal mineral soils do not vary much as a function of applied fertiliser N and could probably be better estimated from soil physical properties, including soil porosity.     

Effects of nitrogen fertilisers,calcium and water regime on the incidence of cavity spot in carrot

Two pot trials were conducted in the growth cabinet to examine the effects of rates and sources of nitrogen (N) fertilisers, rates of calcium (Ca), and two water regimes on the incidence of cavity spot in carrot (Daucus carota) roots. Treatments in Trial I included 4 rates (0, 100, 250, 500 kg N ha^?1) of sodium nitrate (NaNO₃), 4 rates (0, 460, 920, 1380 kg Ca ha^?1) of calcium carbonate (CaCO₃), and 2 water regimes (65 and 100% of the soil water-holding capacity). These treatments were repeated in Trial II, except that ammonium chloride (NH₄ Cl) + N-serve was used instead of NaNO₃. The incidence of cavity spot was found to increase significantly with increasing rates of NH₄Cl + N-serve applied, but not with NaNO₃ or CaCO₃ applications. The high water regime increased the incidence significantly only in Trial I. The results are discussed in relation to changes in soil NH ₄ ⁺ -N and NO ₃ ^- -N levels and other soil properties.     

Nitrous oxide mitigation potential of reduced tillage and N input in durum wheat in the Mediterranean

In Italy, managed soils account for about 50% of annual national emissions of nitrous oxide (N₂O), thus the effect of agricultural practices on N₂O emissions must be studied in order to develop mitigation strategies. Soil N₂O emissions were measured in two field campaigns (2013–2014 and 2014–2015) on durum wheat in a Mediterranean environment to test the mitigation potential of reduced tillage and nitrogen (N) fertilization rate. N₂O emissions were measured with a fully-transportable instrument developed during the project LIFE?+?IPNOA “Improved flux Prototypes for N₂O emission reduction from Agriculture” and equipped with an infrared laser detector. Reducing tillage from ploughing to minimum tillage had no effect on average daily N₂O flux, while decreasing the N rate from 170 to 110 kg N ha^?1 reduced the average daily N₂O flux, without negatively affecting the grain yield. Furthermore, N₂O daily flux were positively correlated with soil water filled pore space, NO₃-N, and NH₄-N concentrations, and they were largely variable between the two field campaigns as a result of different environmental and management conditions (i.e.: rainfall, different amount of crop residues incorporated in soil). Overall, the innovative fully-transportable instrument performed well in the field and allowed us to conclude that decreasing the N fertilizer rate was a valuable option to mitigate N₂O emissions without negative effects on wheat productivity.     

Anthropogenic emissions of NOX, NH3 and N2O in India

Emissions of NO_x, NH₃ and N₂O from anthropogenic activities in India have been estimated based on actual field measurements as well as available default methodologies. The NO_x emissions are mainly from the transport sector and contribute about 5% of the global NO_x emission from fossil fuel. NH₃ emissions from urea seems to be highly uncertain. However, emissions of NH₃ from fertilizers and livestock are estimated to be 1175 Gg and 1433 Gg, respectively. N₂O emissions seem to be derived predominantly from fertilizer applications, resulting in the release of 199–279 Gg N₂O. Other sources of N₂O, viz. agricultural residue burning, biomass burning for energy and nitric acid production are estimated to be 3, 35–187 and 2–7 Gg, respectively.     

Zeolite from alkali modified kaolin increases NH4 retention by sandy soil: Column experiments

Sandy soils have low water and nutrient retention capabilities so that zeolite soil amendments are used for high value land uses including turf and horticulture to reduce leaching losses of NH₄⁺ fertilisers. MesoLite is a zeolitic material made by caustic treatment of kaolin at 80–95 °C. It has a moderately low surface area (9–12 m²/g) and very high cation exchange capacity (494 cmol(+)/kg). Laboratory column experiments showed that an addition of 0.4% MesoLite to a sandy soil greatly (90%) reduced leaching of added NH₄⁺ compared to an unamended soil and MesoLite is 11 times more efficient in retaining NH₄⁺ than natural zeolite. Furthermore, NH₄-MesoLite slowly releases NH₄⁺ to soil solution and is likely to be an effective slow release fertiliser.     

Ammonia and nitrous oxide emissions from grass and alfalfa mulches

Ammonia (NH₃) and nitrous oxide (N_-2O) emissions were measured in the field for three months from three different herbage mulches and from bare soil, used as a control. The mulches were grass with a low N-content (1.15% N in DM), grass with a high N-content (2.12% N in DM) and alfalfa with a high N-content (4.33% N in DM). NH₃ volatilization was measured using a micrometeorological technique. N_-2O emissions were measured using closed chambers. NH₃ and N_-2O emissions were found to be much higher from the N-rich mulches than from the low-N grass and bare soil, which did not differ significantly. Volatilization losses of NH₃ and N_-2O occurred mainly during the first month after applying the herbage and were highest from wet material shortly after a rain. The extent of NH₃-N losses was difficult to estimate, due to the low frequency of measurements and some problems with the denuder technique, used on the first occasions of measurements. Nevertheless, the results indicate that NH₃-N losses from herbage mulch rich in N can be substantial. Estimated losses of NH₃-N ranged from the equivalent of 17% of the applied N for alfalfa to 39% for high-N grass. These losses not only represent a reduction in the fertilizer value of the mulch, but also contribute appreciably to atmospheric pollution. The estimated loss of N_-2O-N during the measurement period amounted to 1% of the applied N in the N-rich materials, which is equivalent to at least 13 kg N_-2O-N ha^-1 lost from alfalfa and 6 kg ha^-1 lost from high-N grass. These emission values greatly exceed the 0.2 kg N_-2O-N ha^-1 released from bare soil, and thus contribute to greenhouse gas emissions.     

Fungal and bacterial contributions to codenitrification emissions of N<Subscript>2</Subscript>O and N<Subscript>2</Subscript> following urea deposition to soil

Grazed pastures contribute significantly to anthropogenic emissions of N₂O but the respective contributions of archaea, bacteria and fungi to codenitrification in such systems is unresolved. This study examined the relative contributions of bacteria and fungi to rates of denitrification and codenitrification under a simulated ruminant urine event. It was hypothesised that fungi would be primarily responsible for both codenitrification and total N₂O and N₂ emissions. The effects of bacterial (streptomycin), fungal (cycloheximide), and combined inhibitor treatments were measured in a laboratory mesocosm experiment, on soil that had received ¹⁵N labelled urea. Soil inorganic-N concentrations, N₂O and N₂ gas fluxes were measured over 51 days. On Days 42 and 51, when nitrification was actively proceeding in the positive control, the inhibitor treatments inhibited nitrification as evidenced by increased soil NH ₄ ⁺ -N concentrations and decreased soil NO ₂ ^? -N and NO ₃ ^? -N concentrations. Codenitrification was observed to contribute to total fluxes of both N₂O (≥ 33%) and N₂ (≥ 3%) in urine-amended grassland soils. Cycloheximide inhibition decreased NH ₄ ⁺ –¹⁵N enrichment and reduced N₂O fluxes while reducing the contribution of codenitrification to total N₂O fluxes by ≥ 66 and ≥ 42%, respectively. Thus, given archaea do not respond to significant urea deposition, it is proposed that fungi, not bacteria, dominated total N₂O fluxes, and the codenitrification N₂O fluxes, from a simulated urine amended pasture soil.     

Nitrogen dynamics during till and no-till pasture restoration sequences in Rondônia,Brazil

The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N₂O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH₄⁺ and NO₃^? pools but NH₄⁺ and NO₃^? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6 months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N₂O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N₂O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover.     

Season and location–specific nitrous oxide emissions in an almond orchard in California

Almonds are an important commodity in California and account for around 15% of the state’s fertilizer nitrogen (N) consumption. Motivated by strong correlations typically observed between fertilizer N inputs and emissions of the potent greenhouse gas and ozone depleting molecule nitrous oxide (N₂O), this study aimed to characterize spatial and temporal patterns in N₂O emissions in an almond orchard under typical agronomic management. N₂O fluxes were measured for a total of 2.5 years, including 3 growing seasons and 2 dormant seasons. Measurements targeted two functional locations, defined as tree rows and tractor rows. In conjunction with the flux measurements, we determined driving variables including soil ammonium (NH₄ ⁺) and nitrate (NO₃ ^?), dissolved organic carbon (DOC), soil water-filled pore space (WFPS), soil pH, air temperature and precipitation. Cumulative annual N₂O emissions were low (0.65 ± 0.07 and 0.53 ± 0.19 kg N₂O–N ha^?1 year^?1 in year 1 and 2, respectively), likely due to the coarse soil texture and microject sprinkler irrigation and fertigation system. Emission factors (EF), conservatively calculated as the ratio of N₂O emitted to fertilizer N applied, were 0.25 ± 0.03% and 0.19 ± 0.07% for year 1 and 2, respectively, which is below the IPCC EF range of 0.3–3%. Correlation analyses between N₂O and driving variables suggested that overall N₂O production was limited by microbial activity and nitrification was likely the major source process, but specific drivers of N₂O emissions varied between seasons and functional locations.     

Land use impact on nitrogen discharge by stream: a case study in subtropical hilly region of China

As a crucial factor of water eutrophication, nitrogen (N) discharge by agricultural non-point sources (NPS) has become a worldwide concern, and so has its relationship to land use. This study was aimed at the quantitative relationships between N discharge by stream and land use. It was conducted in the Meicun watershed of Xuancheng County, Anhui Province, in the subtropical low hilly area of China. The study integrated dynamic monitoring of nutrient discharge by stream water and Geographic Information Systems (GIS) analysis of land use of the watershed. Results showed that NO₃⁻-N discharge ranged between 50 and 60% of the total nitrogen (T-N) and was 2.5–3.0 times as much as NH₄⁺-N. There was a significant difference between forested and mixed sub-watersheds for NH₄⁺-N, NO₃⁻-N and T-N concentrations. Significant correlations existed between NH₄⁺-N, NO₃⁻-N and T-N concentrations in stream water and the area percentages of forest and paddy fields. The study found that the discharges of NH₄⁺-N, NO₃⁻-N and T-N decreased exponentially with forest area increase, but a steep decline for NO₃⁻-N and T-N seemed to occur when the forest percentage surpassed 70% and then there was almost no change. Similarly, the discharges of NH₄⁺-N, NO₃⁻-N and T-N increased exponentially with the paddy fields increase, but a steep augmentation occurred for NO₃⁻-N and T-N when the paddy percentage surpassed 20% and then it remained at a plateau. The study showed that in the subtropical hilly region, paddy fields could increase N discharge due to farming management practices. Thus, primary measures to reduce N in the receiving water body would include a change in farming management and building an ecological interception system for paddy fields.     

Nitrogen Cycling in an Irrigated Wheat System in Sonora, Mexico: Measurements and Modeling

An improved version of an ecosystem nitrogen cycling model (NLOSS) is described, tested, and used to analyze nitrogen cycling in the Yaqui Valley, Sonora, Mexico. In addition to previously described modules in NLOSS that simulate soil water and solute fluxes, soil evaporation, soil energy balance, and denitrification, modules were added to estimate crop growth, soil carbon cycling, urea hydrolysis, and nitrification. We first tested the model against season-long measurements of soil NO₃⁻, NO₂⁻, and NH₄⁺ aqueous concentrations; NO and N₂O soil effluxes; and crop biomass accumulation in three fertilizer treatments. We used NLOSS to test the sensitivity of wheat production, NO₃⁻ losses, and trace-gas emissions to fertilizer application rate. With the␣model, we compared the typical farmer’s fertilization of 250 kg N ha⁻¹ with five other fertilization scenarios, ranging from 110 to 220 kg N ha⁻¹. The typical farmer’s practice produced higher wheat yield than the lower fertilization treatments. However, the increase in yield per increase in kg N applied decreased with increasing fertilizer addition as a result of higher leaching losses, higher residual N, and higher trace-gas emissions. In addition, with respect to the lowest fertilization treatment, the highest fertilization treatment resulted in an 11% decrease, a 10% increase, and a 157% increase in N₂, N₂O, and NO emissions, respectively, and a 41% increase in leached NO₃⁻ + NO₂⁻. These results demonstrate that a small decrease in fertilizer application rate can increase N-use efficiency for wheat growth, while reducing leaching losses and emissions of harmful trace gas fluxes.     

Comparison of several nitrogen fertilisers applied in surface irrigation systems. II. Nitrogen transformations

The movement and transformations in the mineral N pool below the hill and furrow were studied when different N fertilisers were applied in the irrigation water on three occasions during the growth of two maize crops. They included anhydrous ammonia, ammonium sulphate, potassium nitrate and urea. These were compared with anhydrous ammonia injected below the hill before the crop was sown. The ammonium-forming fertilisers increased the mineral-N in the surface of the furrow in both seasons. However no differential adsorption of NH₄ near the surface of the furrow was observed. We have postulated that NH₄ showed preferential movement through the voids in these cracking soils and was not adsorbed at the surface as occurs on soils with discontinuous voids. The proportion of NO₃ in the profile was higher after urea application than with NH₄ sources and was consistent with urea moving further into the peds than NH₄. Nitrification of the anhydrous ammonia band below the hill was rapid in these soils. The proportion of NO₃-N in the mineral N pool below both the hill and furrow declined with time in those locations where the air-filled porosity was generally below 10%. The implications of applying various N sources in the irrigation water on the potential loss processes taking place in the soil are discussed.     

Fertiliser timing and use of inhibitors to reduce N<Subscript>2</Subscript>O emissions of rainfed wheat in a semi-arid environment

Nitrogen (N) management is critical to the profitability of grain production systems, however careful management of fertiliser is needed to minimise environmental impacts. We investigated the effect of five N fertilisation strategies on nitrous oxide (N₂O) emissions and nitrogen use efficiency (NUE) of rainfed wheat grown on a clay soil in a temperate, semi-arid environment of south eastern Australia during 2013 and 2014. Treatments included urea application (50 kg N/ha) at sowing with and without nitrification inhibitor (3,4–dimethylpyrazole phosphate) and surface broadcasting of urea with and without urease inhibitor (n-butyl thiophosphoric triamide) at the end of tillering plus an unfertilised control. Daily N₂O emissions were low and responsive to in-season rainfall and fertiliser addition at sowing. Cumulative emissions from sowing until harvest were highest where N was applied at sowing in 2013; 160 g N₂O-N/ha, while the 0 N control emitted 28 g N₂O-N/ha (over 201 days). Emissions during 2014 were 77% lower than 2013 due to dry seasonal conditions; cumulative emissions were 49 g N₂O-N/ha where N was applied at sowing, with background emissions of around 0 g N₂O-N/ha (over 177 days). Inhibitors showed limited scope for reducing N₂O emissions in this environment, however deferring N application until the end of tillering reduced N₂O emissions. Grain yield responses to fertiliser were significant; increasing grain yield by 11–31% and NUE was generally high (recovery efficiency?>?68%). However, deferring N application until the end of tillering in 2014 reduced yield (??19%) and recovery of applied N (??74%).