Urease and nitrification inhibitors can reduce ammonia and greenhouse gas emissions from fertilizers and manure but their effectiveness depends on the conditions under which they are used. Consequently, it is essential for the credibility of emission reductions reported in regulatory emission inventories that their effectiveness is assessed under real-world conditions and not just in the laboratory. Here, we specify the criteria we consider necessary before the effects of inhibitors are included in regulatory emission inventories.

Crop residues are important inputs of carbon (C) and nitrogen (N) to soils and thus directly and indirectly affect nitrous oxide (N2 O) emissions. As the current inventory methodology considers N inputs by crop residues as the sole determining factor for N2 O emissions, it fails to consider other underlying factors and processes. There is compelling evidence that emissions vary greatly between residues with different biochemical and physical characteristics, with the concentrations of mineralizable N and decomposable C in the residue biomass both enhancing the soil N2 O production potential. High concentrations of these components are associated with immature residues (e.g., cover crops, grass, legumes, and vegetables) as opposed to mature residues (e.g., straw). A more accurate estimation of the short-term (months) effects of the crop residues on N2 O could involve distinguishing mature and immature crop residues with distinctly different emission factors. The medium-term (years) and long-term (decades) effects relate to the effects of residue management on soil N fertility and soil physical and chemical properties, considering that these are affected by local climatic and soil conditions as well as land use and management. More targeted mitigation efforts for N2 O emissions, after addition of crop residues to the soil, are urgently needed and require an improved methodology for emission accounting. This work needs to be underpinned by research to (1) develop and validate N2 O emission factors for mature and immature crop residues, (2) assess emissions from belowground residues of terminated crops, (3) improve activity data on management of different residue types, in particular immature residues, and (4) evaluate long-term effects of residue addition on N2 O emissions.

Agriculture is essential for providing food and maintaining food security while concurrently delivering multiple other ecosystem services. However, agricultural systems are generally a net source of greenhouse gases and ammonia. They, therefore, need to substantively contribute to climate change mitigation and net zero ambitions. It is widely acknowledged that there is a need to further reduce and mitigate emissions across sectors, including agriculture to address the climate emergency and emissions gap. This discussion paper outlines a collation of opinions from a range of experts within agricultural research and advisory roles following a greenhouse gas and ammonia emission mitigation workshop held in the UK in March 2022. The meeting identified the top mitigation priorities within the UK's agricultural sector to achieve reductions in greenhouse gases and ammonia that are compatible with policy targets. In addition, experts provided an overview of what they believe are the key knowledge gaps, future opportunities and co -benefits to mitigation practices as well as indicating the potential barriers to uptake for mitigation scenarios discussed.

According to the available guidelines, good practices for calculating nitrous oxide (N2O) emission factors (EFs) for livestock excreta and manure application include that sampling duration should be of at least one year after the nitrogen (N) application or deposition. However, the available experimental data suggest that in many cases most emissions are concentrated in the first months following N application. Therefore resources could be better deployed by measuring more intensively during a shorter period. This study aimed to assess the contribution of the N2O flux in the period directly after N application to the annual net emission. We used a database of 100 year-long plot experiments from different excreted-N sources (dung, urine, farmyard manure and slurry) used to derive EFs for the UK and Ireland. We explored different shorter potential measurement periods that could be used as proxies for cumulative annual emissions. The analysis showed that the majority of emissions occur in the first months after application, especially in experiments that i) had urine as the N source, ii) had spring N application, iii) were conducted on fine-textured soils, or iv) showed high annual emissions magnitude. Experiments that showed a smaller percentage of emissions in the first months also had a low magnitude of annual net emissions (below 370 gN2O-N ha-1 year-1), so the impact of measuring during a shorter period would not greatly influence the calculated EF. Accurate EF estimations were obtained by measuring for at least 60 days for urine (underestimation: 7.1%), 120 days for dung and slurry (4.7 and 5.1%) and 180 days for FYM (1.4%). At least in temperate climates, these results are promising in terms of being able to estimate annual N2O fluxes accurately by collecting data for less than 12 months, with significant resource-saving when conducting experiments towards developing country-specific EFs.

Soil acidification has negative impacts on grass biomass production and the potential of grasslands to mitigate greenhouse gas (GHG) emissions. Through a global review of research on liming of grasslands, the objective of this paper was to assess the impacts of liming on soil pH, grass biomass production and total net GHG exchange (nitrous oxide (N2O), methane (CH4) and net carbon dioxide (CO2)). We collected 57 studies carried out at 88 sites and covering different countries and climatic zones. All of the studies examined showed that liming either reduced or had no effects on the emissions of two potent greenhouse gases (N2O and CH4). Though liming of grasslands can increase net CO2 emissions, the impact on total net GHG emission is minimal due to the higher global warming potential, over a 100-year period, of N2O and CH4 compared to that of CO2. Liming grassland delivers many potential advantages, which justify its wider adoption. It significantly ameliorates soil acidity, increases grass productivity, reduces fertiliser requirement and increases species richness. To realise the maximum benefit of liming grassland, we suggest that acidic soils should be moderately limed within the context of specific climates, soils and management.

Permanent grasslands cover 34% of the European Union's agricultural area and are vital for a wide variety of ecosystem services essential for our society. Over recent decades, the permanent grassland area has declined and land use change continues to threaten its extent. Simultaneously, the management intensity of permanent grasslands increased. We performed a systematic literature review on the multifunctionality of permanent grasslands in Europe, examining the effects of land use and management on 19 grassland ecosystem service indicators. Based on the evidence in 696 out of 70,456 screened papers, published since 1980, we found that both land use change and intensification of management decreased multifunctionality. In particular, preventing conversion of permanent grasslands to croplands secured the delivery of multiple ecosystem services. A lower management intensity was associated with benefits for biodiversity, climate regulation and water purification, but impacted the provision of high-quality animal feed. Increasing the number of species in the sward enhanced multifunctionality of permanent grassland without significant trade-offs such as losses in production. Our review covered many aspects of land use, management and ecosystem services, but we also identified areas with no or only few studies. The most prominent gaps were related to comparisons between permanent and temporary grasslands, and effects of management practices on the provision of cultural values, and on erosion and flood control. We suggest that, despite apparent changes in human dietary preferences, the protection of permanent grasslands in Europe must be prioritised. At the same time, considering the need to reduce ruminant livestock's contribution to climate change, the time seems ripe to increase support for low-intensity grassland management to optimise the provision of essential ecosystem services from Europe's permanent grasslands.

Nitrous oxide (N 2 O), ammonia (NH 3 ), and methane (CH 4 ) emissions from the manure management chain of livestock production systems are important contributors to greenhouse gases (GHGs) and NH 3 emitted by human activities. Several studies have evaluated manure-related emissions and associated key variables at regional, national, or continental scales. However, there have been few studies focusing on the drivers of these emissions using a global dataset. An international project was created (DATAMAN) to develop a global database on GHG and NH 3 emissions from the manure management chain (housing, storage, and field) to identify key variables influencing emissions and ultimately to refine emission factors (EFs) for future national GHG inventories and NH 3 emission reporting. This paper describes the “field” database that focuses on N 2 O and NH 3 EFs from land-applied manure and excreta deposited by grazing livestock. We collated relevant information (EFs, manure characteristics, soil properties, and climatic conditions) from published peer-reviewed research, conference papers, and existing databases. The database, containing 5,632 observations compiled from 184 studies, was relatively evenly split between N 2 O and NH 3 (56 and 44% of the EF values, respectively). The N 2 O data were derived from studies conducted in 21 countries on five continents, with New Zealand, the United Kingdom, Kenya, and Brazil representing 86% of the data. The NH 3 data originated from studies conducted in 17 countries on four continents, with the United Kingdom, Denmark, Canada, and The Netherlands representing 79% of the data. Wet temperate climates represented 90% of the total database. The DATAMAN field database is available at http://www.dataman.co.nz .

Manure application to land and deposition of urine and dung by grazing animals are major sources of ammonia (NH3 ) and nitrous oxide (N2 O) emissions. Using data on NH3 and N2 O emissions following land-applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed, and the effects of mitigation strategies were evaluated. The NH3 data represent emissions from cattle and swine manures in temperate wet climates, and the N2 O data include cattle, sheep, and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH3 EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH3 -N kg-1 total N (TN), respectively, whereas the NH3 EF of broadcast swine slurry was 0.29. Emissions from both cattle and swine slurry were reduced between 46 and 62% with low-emissions application methods. Land application of cattle and swine manure in wet climates had EFs of 0.005 and 0.011 kg N2 O-N kg-1 TN, respectively, whereas in dry climates the EF for cattle manure was 0.0031. The N2 O EFs for cattle urine and dung in wet climates were 0.0095 and 0.002 kg N2 O-N kg-1 TN, respectively, which were three times greater than for dry climates. The N2 O EFs for sheep urine and dung in wet climates were 0.0043 and 0.0005, respectively. The use of nitrification inhibitors reduced emissions in swine manure, cattle urine/dung, and sheep urine by 45-63%. These enhanced EFs can improve national inventories; however, more data from poorly represented regions (e.g., Asia, Africa, South America) are needed.

Crop residue incorporation is a common practice to increase or restore organic matter stocks in agricultural soils. However, this practice often increases emissions of the powerful greenhouse gas nitrous oxide (N2O). Previous meta-analyses have linked various biochemical properties of crop residues to N2O emissions, but the relationships between these properties have been overlooked, hampering our ability to predict N2O emissions from specific residues. Here we combine comprehensive databases for N2O emissions from crop residues and crop residue biochemical characteristics with a random-meta-forest approach, to develop a predictive framework of crop residue effects on N2O emissions. On average, crop residue incorporation increased soil N2O emissions by 43% compared to residue removal, however crop residues led to both increases and reductions in N2O emissions. Crop residue effects on N2O emissions were best predicted by easily degradable fractions (i.e. water soluble carbon, soluble Van Soest fraction (NDS)), structural fractions and N returned with crop residues. The relationship between these biochemical properties and N2O emissions differed widely in terms of form and direction. However, due to the strong correlations among these properties, we were able to develop a simplified classification for crop residues based on the stage of physiological maturity of the plant at which the residue was generated. This maturity criteria provided the most robust and yet simple approach to categorize crop residues according to their potential to regulate N2O emissions. Immature residues (high water soluble carbon, soluble NDS and total N concentration, low relative cellulose, hemicellulose, lignin fractions, and low C:N ratio) strongly stimulated N2O emissions, whereas mature residues with opposite characteristics had marginal effects on N2O. The most important crop types belonging to the immature residue group - cover crops, grasslands and vegetables - are important for the delivery of multiple ecosystem services. Thus, these residues should be managed properly to avoid their potentially high N2O emissions.

Adequately estimating soil nitrous oxide (N2 O) emissions using static chambers is challenging due to the high spatial variability and episodic nature of these fluxes. We discuss how to design experiments using static chambers to better account for this variability and reduce the uncertainty of N2 O emission estimates. This paper is part of a series, each discussing different facets of N2 O chamber methodology. Aspects of experimental design and sampling affected by spatial variability include site selection and chamber layout, size, and areal coverage. Where used, treatment application adds a further level of spatial variability. Time of day, frequency, and duration of sampling (both individual chamber closure and overall experiment duration) affect the temporal variability captured. We also present best practice recommendations for chamber installation and sampling protocols to reduce further uncertainty. To obtain the best N2 O emission estimates, resources should be allocated to minimize the overall uncertainty in line with experiment objectives. Sometimes this will mean prioritizing individual flux measurements and increasing their accuracy and precision by, for example, collecting four or more headspace samples during each chamber closure. However, where N2 O fluxes are exceptionally spatially variable (e.g., in heterogeneous agricultural landscapes, such as uneven and woody grazed pastures), using available resources to deploy more chambers with fewer headspace samples per chamber may be beneficial. Similarly, for particularly episodic N2 O fluxes, generated for example by irrigation or freeze-thaw cycles, increasing chamber sampling frequency will improve the accuracy and reduce the uncertainty of temporally interpolated N2 O fluxes.

Terrestrial ecosystems, both natural ecosystems and agroecosystems, generate greenhouse gases (GHGs). The chamber method is the most common method to quantify GHG fluxes from soil-plant systems and to better understand factors affecting their generation and mitigation. The objective of this study was to review and synthesize literature on chamber designs (non-flow-through, non-steady-state chamber) and associated factors that affect GHG nitrous oxide (N2 O) flux measurement when using chamber methods. Chamber design requires consideration of many facets that include materials, insulation, sealing, venting, depth of placement, and the need to maintain plant growth and activity. Final designs should be tailored, and bench tested, in order to meet the nuances of the experimental objectives and the ecosystem under study while reducing potential artifacts. Good insulation, to prevent temperature fluctuations and pressure changes, and a high-quality seal between base and chamber are essential. Elimination of pressure differentials between headspace and atmosphere through venting should be performed, and designs now exist to eliminate Venturi effects of earlier tube-type vent designs. The use of fans within the chamber headspace increases measurement precision but may alter the flux. To establish best practice recommendations when using fans, further data are required, particularly in systems containing tall plants, to systematically evaluate the effects that fan speed, position, and mixing rate have on soil gas flux.

Nitrous oxide (N2O) emission from agricultural soils represents a significant source of greenhouse gas to the atmosphere. We evaluated the suitability of a modified Soil and Water Assessment Tool (SWAT) model to estimate the N2O flux from the application of solid manure at two grassland sites (North Wyke [NW] and Pwllpeiran [PW]) in the United Kingdom. The simulated N2O emissions were validated against field observations measured in 2011 and 2012 for model calibration and validation, respectively. The SWAT model predicts water-filled pore space (WFPS) very well with Nash-Sutcliffe efficiency (NSE), R-2, RMSE, and percentage bias (PBIAS) values of 0.67, .72, 0.06, and 3.64, respectively, during the calibration period for NW site, whereas it gives 0.68, .69, 0.07, and 3.04, respectively during the validation period. At PW, the model predicted the NSE, R-2, RMSE, and PBIAS of 0.55, .69, 0.04, and -4.5, respectively, during calibration and 0.63, .71, 0.05, and -2.6, respectively, during the validation period. Compared with WFPS, the model resulted in a slightly lower fit for N2O emissions for NW (NSE = 0.47, R-2 = .63 during calibration, and NSE = 0.55, R-2 = .58 during validation) and for PW (NSE = 0.54, R-2 = .71 for calibration, and NSF = 0.47, R-2 = .69 for validation). Results revealed that the SWAT model performed reasonably well in representing the dynamics of N2O emissions after solid manure application to grassland.

Nitrous oxide (N2O) emission factors (EFs) were calculated from measurements of emissions from livestock manures applied to UK arable crops and grassland as part of a wider research programme to reduce uncertainty in the UK national agricultural N2O inventory and to enhance regional inventory reporting through increased understanding of processes and factors controlling emissions. Field studies were undertaken between 2011 and 2013 at 3 arable and 3 grassland sites in the UK. Nitrous oxide emissions were measured following the autumn and spring application of different manures (pig slurry, cattle slurry, cattle farmyard manure (FYM), pig FYM, poultry layer manure, and broiler litter) at typical rates, using representative manure application and soil incorporation methods. In addition, ammonia emissions and nitrate leaching losses (1 site on a light sandy soil) were measured to calculate indirect N2O losses. IPCC comparable, direct N2O EFs ranged from −0.05 to 2.30% of total nitrogen applied, with the variability driven by a range of factors including differences in manure composition, application method, incorporation and climatic conditions. When data from the autumn applications were pooled, the mean N2O EF from poultry manure (1.52%) was found to be greater (P < 0.001) than from FYM (0.37%) and slurry (0.72%), with no difference found (P = 0.784) in the EF for bandspread compared with surface broadcast slurry application, and no effect (P = 0.328) of the nitrification inhibitor, Dicyandiamide (DCD). For the spring applications, the mean N2O EF for bandspread slurry (0.56%) was greater (P = 0.028) than from surface broadcast slurry (0.31%), but there were no differences (P = 0.212) in the mean N2O EFs from poultry manure (0.52%), slurry (0.44%), and FYM (0.22%). The study did confirm, however, that DCD reduced N2O emissions from slurries applied in the spring by 45%. EF data from this project have been used in the derivation of robust Tier 2 country specific EFs for inclusion in the UK national agriculture greenhouse gas inventory.

Intensification of grasslands is necessary to meet the increasing demand of livestock products. The application of nitrogen (N) on grasslands affects the N balance therefore the nitrogen use efficiency (NUE). Emissions of nitrous oxide (N2O) are produced due to N fertilisation and low NUE. These emissions depend on the type and rates of N applied. In this study we have compiled data from 5 UK N fertilised grassland sites (Crichton, Drayton, North Wyke, Hillsborough and Pwllpeiran) covering a range of soil types and climates. The experiments evaluated the effect of increasing rates of inorganic N fertiliser provided as ammonium nitrate (AN) or calcium ammonium nitrate (CAN). The following fertiliser strategies were also explored for a rate of 320 kg N ha-1: using the nitrification inhibitor dicyandiamide (DCD), changing to urea as an N source and splitting fertiliser applications. We measured N2O emissions for a full year in each experiment, as well as soil mineral N, climate data, pasture yield and N offtake. N2O emissions were greater at Crichton and North Wyke whereas Drayton, Hillsborough and Pwllpeiran had the smallest emissions. The resulting average emission factor (EF) of 1.12% total N applied showed a range of values for all the sites between 0.6 and 2.08%. NUE depended on the site and for an application rate of 320 kg N ha-1, N surplus was on average higher than 80 kg N ha-1, which is proposed as a maximum by the EU Nitrogen Expert Panel. N2O emissions tended to be lower when urea was applied instead of AN or CAN, and were particularly reduced when using urea with DCD. Finally, correlations between the factors studied showed that total N input was related to Nofftake and Nexcess; while cumulative emissions and EF were related to yield scaled emissions.

Many studies have shown the efficiency of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in suppressing nitrification and nitrous oxide (N2O) emissions. However, the effect of DMPP on soil gross nitrogen transformations and the mechanism of its inhibitory effects on N2O production pathways remain unknown. A 15N tracing experiment was conducted to investigate the effect of DMPP on gross N transformation rates and pathways of N2O production in two typical Chinese and UK agricultural soils. The soils differed in organic carbon (C) and clay content but otherwise had similar properties. The results showed that the application of DMPP decreased the gross autotrophic nitrification rate (p < 0.05) by 21.6% in the Chinese soil and 9.4% in the UK soil. The lower inhibitory efficiency of DMPP in the UK soil was likely to have been due to high rates of adsorption by soil organic C and clay. The total gross rate of mineralization was lower in the presence of DMPP in both soils, likely because there was a regulatory feedback when ammonium concentrations were high. DMPP also significantly reduced cumulative N2O emissions (p < 0.05) in both soils (by between 15.8 and 68.4%), which might be attributed to the dual inhibitory effect of the DMPP on autotrophic nitrification rate and the proportion of N2O produced by autotrophic nitrification processes. This finding will help to predict the sites where DMPP is likely to be most effective and allow the user to target DMPP application to soils with particular properties.

The properties of agricultural soils in various regions of the world are variable and can have a significant but poorly understood impact on soil nitrogen (N) transformations and nitrous oxide (N2O) emissions. For this reason, we undertook a study of gross N transformations and related N2O emissions in contrasting agricultural soils from China and the UK. Seven Chinese and three UK agricultural soils were collected for study using a 15N tracing approach. The soil pH ranged from 5.4 to 8.7, with three acidic soils collected from Jinjing, Lishu and Boghall; one neutral soil collected from Changshu, and the other six alkaline soils collected from Quzhou, Zhangye, Changwu, Jinzhong, Boxworth and Stetchworth. Our results showed that the main N transformation processes were oxidation of ammonium (NH4+) to nitrate (NO3-) (ONH4), and mineralization of organic N to NH4+. The gross autotrophic nitrification rates calculated in the three acidic soils were between 0.25 and 4.15 mg N kg-1 d-1, which were significantly lower (p < 0.05) than those in the remaining neutral and alkaline soils ranging from 6.94 to 14.43 mg N kg-1 d-1. Generally, soil pH was positively correlated (p < 0.001) with gross autotrophic nitrification rate and cumulative N2O emissions, indicating that soil pH was an important factor regulating autotrophic nitrification and N2O emissions. There was also a significant positive correlation between the gross autotrophic nitrification rate and cumulative N2O emissions, highlighting the importance of this process for producing N2O emissions in these agricultural soils under aerobic conditions. Gross NH4+ immobilization rates were very low in most soils except for the Jinjing soil with the lowest pH. In conclusion, the gross autotrophic nitrification rates and related N2O emissions were controlled by soil pH irrespectively of the soil's origin in these agricultural soils.

Organic fertilizers, such as manure and compost, are promising additions for synthetic fertilizers in order to increase soil fertility and crop yields. However, the organic fertilizers applied to soils may increase nitrous oxide (N2O, a greenhouse gas) emissions due to their lower C/N ratios, and therefore potentially contribute to global warming. Very few studies have used process-based models to assess the environmental advantages and drawbacks of compost soil amendments compared to other field treatments. In this study, the UK-DNDC model was modified for simulation of nitrous oxide (N2O) fluxes emitted from the soils treated with green compost and farmyard manure at three UK farms (WE, PW and NW): one winter wheat and two grasslands. The results show that the annual overall N2O emissions were 1.45 kg N ha(-1) y(-1) for WE treated with farmyard manure, 0.71 for WE with green compost, 1.09910 for PW treated with farmyard manure, 0.94 for PW treated with green compost, 1.19 for NW treated with farmyard manure, and 1.18 for NW treated with green compost. A two dimensional linear model was developed to correlate nitrogen loading and soil pH for calculations of emissions and emission factors (EFs). The linear model could fit the emissions obtained from the UK-DNDC model well. The squares of correlation coefficients of the emissions between two models are 0.993 and 0.985 for farmyard manure and green compost, respectively. Analysis of correlation coefficients between N2O emissions and air temperature, precipitation as well as the time period between fertilizer application and sample measurement (PFS) for the three sites treated with farmyard manure and compost indicated that N2O emissions were mainly related to PFS. The modified DNDC model provides an approach to estimating N2O emissions from compost amended soils. (C) 2018 Elsevier B.V. All rights reserved.

Urine patches and dung pats from grazing livestock create hotspots for production and emission of the greenhouse gas, nitrous oxide (N2O), and represent a large proportion of total N2O emissions in many national agricultural greenhouse gas inventories. As such, there is much interest in developing country specific N2O emission factors (EFs) for excretal nitrogen (EF3, pasture, range and paddock) deposited during gazing. The aims of this study were to generate separate N2O emissions data for cattle derived urine and dung, to provide an evidence base for the generation of a country specific EF for the UK from this nitrogen source. The experiments were also designed to determine the effects of site and timing of application on emissions, and the efficacy of the nitrification inhibitor, dicyandiamide (DCD) on N2O losses. This co-ordinated set of 15 plot-scale, year-long field experiments using static chambers was conducted at five grassland sites, typical of the soil and climatic zones of grazed grassland in the UK. We show that the average urine and dung N2O EFs were 0.69% and 0.19%, respectively, resulting in a combined excretal N2O EF (EF3), of 0.49%, which is <25% of the IPCC default EF3 for excretal returns from grazing cattle. Regression analysis suggests that urine N2O EFs were controlled more by composition than was the case for dung, whilst dung N2O EFs were more related to soil and environmental factors. The urine N2O EF was significantly greater from the site in SW England, and significantly greater from the early grazing season urine application than later applications. Dycandiamide reduced the N2O EF from urine patches by an average of 46%. The significantly lower excretal EF3 than the IPCC default has implications for the UK's national inventory and for subsequent carbon footprinting of UK ruminant livestock products.

Organic fertilizers, such as digestates and manure, are increasingly applied in agricultural systems because of the benefits they provide in terms of plant nutrients and soil quality. However, there are few investigations of N2O emissions following digestate application to agricultural soils using process-based models. In this study, we modified the UK-DNDC model to include digestate applications to soils by adding digestate properties to the model and considering the effect of organic fertilizer pH. Using the modified model, N2O emissions were simulated from two organic fertilizers (digested food waste and livestock slurry) applied to three farms in the United Kingdom: one growing winter wheat at Wensum (WE) and two grasslands at Pwllpeiran (PW) and North Wyke (NW). The annual cumulative gross (i.e. not excluding control emission) N2O emissions were calculated using MATLAB trapezoidal numerical integration. The relative errors of the modeled annual cumulative emissions to the measured emissions ranged from -5.4% to 48%. Two-factor models, including linear, exponential and hyperbola responses, correlating total N loading and soil clay content to calculations of N2O emissions and N2O emission factors (EFs) were developed for calculations of emission fluxes and EFs. The squares of the correlation coefficients of the measured and two-factor linear modeled emissions were 0.998 and 0.999 for digestate and slurry, respectively, and the corresponding squares of correlation coefficients of the EFs were 0.998 and 0.938. The two-factor linear model also predicted that the EFs increased linearly with decreasing clay content and the maximum EFs for digestate and slurry were 0.95 and 0.76% of total N applied, respectively. This demonstrates that the modified UK_DNDC is a good tool to simulate N2O emission from digestate and slurry and to calculate UK EFs using TIER 3 methodology. (C) 2018 Elsevier Ltd. All rights reserved.

The anaerobic digestion of food waste for energy recovery produces a nutrient-rich digestate which is a valuable source of crop available nitrogen.(N). As with any 'new' material being recycled to agricultural land it is important to develop best management practices that maximise crop available N supply, whilst minimising emissions to the environment. In this study, ammonia (NH3) and nitrous oxide (N2O) emissions to air and nitrate (NO3-) leaching losses to water following digestate, compost and livestock manure applications to agricultural land were measured at 3 sites in England and Wales. Ammonia emissions were greater from applications of food-based digestate (c.40% of total N applied) than from livestock slurry (c.30% of total N applied) due to its higher ammonium-N content (mean 5.6 kg/t compared with 1-2 kg/t for slurry) and elevated pH (mean 83 compared with 7.7 for slurry). Whilst bandspreading was effective at reducing NH3 emissions from slurry compared with surface broadcasting it was not found to be an effective mitigation option for food-based digestate in this study. The majority of the NH3 losses occurred within 6 h of spreading highlighting the importance of rapid soil incorporation as a method for reducing NH3 emissions. Nitrous oxide losses from food-based digestates were low, with emission factors all less than the IPCC default value of 1% (mean 0.45 +/- 0.15%). Overwinter N-3(-) leaching losses from food-based digestate were similar to those from pig slurry, but much greater than from pig farmyard manure or compost. Both gaseous N losses and NO3- leaching from green and green/food composts were low, indicating that, in these terms, compost can be considered as an 'environmentally benign' material. These findings have been used in the development of best practice guidelines which provide a framework for the responsible use of digestates and composts in agriculture. (C) 2017 Elsevier Ltd. All rights reserved.