Uptake of hydrogen from the atmosphere by microbial activity in soils is the main global H2 sink mechanism. The processes and environmental drivers which modulate the H2 soil sink are highly uncertain, but research has demonstrated that moisture, soil porosity and temperature affect the magnitude of H2 uptake by soil microbes. Peatlands are carbon-rich, dynamic environments with a fluctuating water table and temporal seasonal variation. These environments harbour a relatively large capacity for microbial activity but also contain a variety of mixed environments and microtopography (hummocks and hollows). There are no dedicated studies reported in literature exploring H2 flux dynamics in peatlands to date.To investigate the drivers of H2 flux in peatland environments, in-situ field measurements of H2 flux have been carried out using the flux chamber method at two Scottish peatlands. Auchencorth Moss (AC) and Whim Bog (WH) are located within the Pentland region south of Edinburgh. AC was previously drained, with peat depth at the study site between 0.5 - 1 m, whereas WH has been left in its natural state with peat depth ranging between 3 - 6 m. At each site, chambers were placed to capture variation in H2 flux due to microtopography. Water table depth and temperature measurements were taken at each chamber at each measurement occasion. Initial results show that mean H2 flux in autumn and winter were -21.5 nmol m-2 s-1 at AC and -18.5 nmol m-2 s-1 at WB.As well as in-situ field studies, lab-based incubations using soil samples from AC and WH have been conducted to investigate H2 flux under controlled moisture conditions to identify optimum conditions for uptake. Analysis is being carried out using DNA sequencing to identify the microbial species responsible for H2 consumption in samples. Molecular sequencing will also explore the abundance of the gene which activates the expression of the hydrogenase enzyme under varying moisture levels to infer the favourable environmental conditions for H2 uptake on a microbial scale. We hope to report preliminary results at EGU. The main aim of this work is to assess the strength H2 soil sink in high carbon landscapes such as peatlands and explore the key environmental and microbial drivers that constrain H2 uptake.

Human activities emit nitrogen oxides (NOx ≡ NO + NO2; with source emissions approximated as nitric oxide (NO)), potent air pollutants and short-lived climate forcers, through direct and indirect pathways. Unlike direct releases, however, indirect NOx emissions remain poorly understood and inadequately quantified. Here, by synthesizing available observations across global terrestrial ecosystems, we show that soil moisture and pH strongly affect the ratio of annual background NO to nitrous oxide (N2O) emissions ( R NO / N 2 O ), with a critical threshold at 46% water-filled soil pore space. Combining soil moisture-stratified R NO / N 2 O modeled by machine learning with known indirect N2O emission factors, global indirect NOx emission factors ( EF 4 N O x ) are derived, yielding an aggregated median of 1.59% (95% confidence interval (CI): 0.45%-2.41%) and significantly higher (p < 0.01) disaggregated values of 1.77% (95% CI: 1.49%-2.61%) for wet climates ( EF 4 , WC N O x ) than those of 0.89% (95% CI: 0.45%-1.28%) for dry climates ( EF 4 , DC N O x ). We further estimate that the global indirect NOx emissions resulting from atmospheric deposition of nitrogen released by all anthropogenic sources amounted to approximately 886 (95% CI: 314-1639) Gg N year-1 (1 Gg = 109 g) in 2015, with fertilization, animal husbandry, and other human activities contributing about 25%, 26%, and 49%, respectively. Crucially, without soil moisture stratification, the global indirect NOx emissions would be underestimated by approximately 16% (p < 0.001), while the associated uncertainty would be about 1.5 times as large. Our novel R NO / N 2 O -based framework provides a robust approach for quantifying indirect NOx emissions in regional, national and global inventories, thereby supporting targeted strategies to mitigate air pollution and climate change.

Abstract. Enhanced rock weathering (ERW) is a proposed carbon dioxide (CO2) removal strategy via the application of crushed silicate rocks to accelerate the natural breakdown of silicate minerals, permanently trapping atmospheric CO2. Application of rock dust may alter soil properties, such as pH, with potential consequences for soil trace gases fluxes relevant to climate forcing and air quality. However, previous ERW studies have focused mainly on the principal greenhouse gases, while broader trace gas responses remain poorly constrained. This laboratory study presents measurements of nitric oxide (NO), ammonia (NH3), carbon monoxide (CO), hydrogen (H2) and volatile organic compounds (VOCs), as well as CO2, methane (CH4) and nitrous oxide (N2O), from control and ERW-treated soils collected from arable, grassland and newly planted broadleaf and conifer forest field trials in the UK. Soils were sieved, repacked and rewetted for laboratory measurements. A dynamic air-flow-through chamber system, equipped with a high-resolution multi-gas analyser and a proton-transfer-reaction mass spectrometer, was used to measure N2O, NO, NH3, CO, and VOCs between 5 and 25 °C. CO2 and CH4 fluxes were measured online at 20 °C using a closed-loop chamber method, and H2 fluxes were measured by discrete sampling from static chamber headspace using gas chromatography. ERW-associated differences varied among gases and soils, with no consistent response across all incubated samples. The reported treatment differences included lower CO2 emissions in both forest soils, greater CH4 uptake in broadleaf forest soil, higher NO emissions in grassland soil, and changes in CO and hydrocarbon fluxes in forest soils. NH3 and H2 fluxes showed no statistically significant treatment responses, and no individual VOC remained significantly different after correction for multiple testing. Overall, rock dust application had limited and inconsistent impacts on trace gas fluxes across the soils examined in this snapshot study. Longer-term measurements at ERW field trials are needed to examine how these responses vary seasonally and evolve as the applied materials continued to weather. These measurements should be accompanied by in-depth soil characterisation and microbial analyses to elucidate the complex relationships between ERW treatment and trace gas fluxes. This evidence is needed to assess the full climate, air-quality and environmental implications of large-scale ERW deployment.

Microbial uptake in soils is the dominant natural sink of atmospheric hydrogen (H2); however, the environmental controls governing this process remain poorly constrained across different soil types and land uses. This study investigates H2 fluxes with a diverse set of soils using controlled laboratory incubations designed to isolate the effects of soil moisture, soil physical properties, carbon pools, pH, and temperature. Topsoils from 11 sites were sieved, repacked, and subjected to a moisture gradient from saturation to near-dryness, with H2 fluxes regularly measured. Across all soils, moisture was the primary control of H2 uptake. Uptake initially increased as soils dried from saturation, peaked at intermediate moisture levels (10 to 40% water-filled pore space), and then declined again under both saturated and near-dry conditions. Organic content-rich systems behaved differently to mineral soils. Peatland soil showed exceptionally strong H2 uptake across a wider moisture range, driven by its porous structure and large dissolved organic carbon (DOC) pool. When included in regression models, DOC content emerged as a major predictor of flux, contributing significantly to an overall model explanatory power of R2 = 0.51 when paired with other variables. Investigations revealed that forest litter acted as a strong H2 sink, with uptake an order of magnitude higher than soils (by mass) and remained active even at sub-zero temperatures. These results demonstrate that H2 uptake is strongly regulated by soil physical structure and moisture in mineral soils, but also by labile carbon and organic-layer properties in high-carbon environments. The findings highlight the importance of explicitly representing peatlands, the availability of labile carbon pools, and surface organic layers in models of the global H2 budget and emphasise the need for more field measurements in carbonrich and understudied ecosystems.

Smallholder oil palm (OP) systems are central to rural livelihoods and global vegetable oil supply, yet the evidence base informing their environmental management is heavily concentrated in Southeast Asia (SEA). At the same time, OP cultivation is expanding across Sub-Saharan Africa (SSA), where production systems differ markedly. The uneven distribution of research and the rapid growth of the sector in Africa create a need for careful comparative synthesis to clarify where lessons are transferable and where they are not. This review compares smallholder OP systems in SEA and SSA to examine how contrasting development histories, agronomic practices, and governance shape current and future potential for environmental sustainability. This review synthesises evidence on nutrient management, soil fertility, yield potential, greenhouse gas emissions, crop residue management, and institutional constraints. SEA systems are generally characterised by higher external inputs, established processing infrastructure, and more developed certification and policy frameworks, alongside well-documented challenges related to nutrient losses, soil degradation, and emissions. In contrast, many SSA systems operate under lower-input, resource-constrained conditions, with complex land tenure systems, resulting in distinct productivity and environmental profiles. Rather than assuming a common development trajectory, the review highlights major differences that influence environmental performance across regions. By distinguishing between context-specific challenges and potentially transferable practices, this synthesis provides a clearer evidence base for researchers, policymakers, and practitioners working to improve the sustainability of smallholder OP systems.

The current inventory framework of the Intergovernmental Panel on Climate Change (IPCC) relies on a single generalized default direct emission factor (EF), which inadequately captures the substantial heterogeneity in nitric oxide (NO) emissions from managed soils and may therefore lead to systematic biases in nitrogen oxides (NOx) inventories across vegetation types and environmental conditions. To address this limitation, and given that soil-emitted NOx is predominantly released as NO, we synthesized global field observations of direct EFs for NO to develop an updated methodological framework for Tier 1- and Tier 2-based inventories of national and global direct NOx emissions from managed soils. For Tier 1, our synthesis yielded 0.49% (95% confidence interval: 0.41%–0.58%), 1.66% (1.17%–2.15%), 0.10% (0.05%–0.17%), and 0.11% (0.06%–0.18%) as aggregated EFs for managed soils (I) growing upland vegetation types other than tea plantations (EF1,O(NOx)), (II) utilized for tea plantations (EF1,Tea(NOx)), (III) cultivated with flooded rice (EF1,FR(NOx)), and (IV) receiving urine and dung deposition by grazing animals (EF3(NOx)), respectively. Significant differences in direct EFs were observed among major cropping systems, with the highest, intermediate and lowest values occurring in types II, I and III, respectively (p = 0.001). For type I, soil organic carbon (SOC) content was identified as the most robust factor regulating direct EFs of NO (p = 0.001). Accordingly, for one Tier 2 option, this type was further disaggregated into two SOC-based subcategories, with direct EFs of 0.31% (0.25%–0.37%) for SOC ≤1% (EF1,O,SOC≤1%(NOx)), and 0.62% (0.49%–0.75%) for SOC >1% (EF1,O,SOC>1%(NOx)). These newly developed direct EFs would enable more accurate inventories of NOx emissions from managed soils and better support targeted mitigation strategies.

Nitrogen (N) fertilizers boost agricultural yields, but N lost from agricultural systems may endanger the ecosystem. The agronomic practices leading to high N recovery with decreased losses without compromising yields need to be identified. Field experiments were conducted for two consecutive wheat growing seasons using three levels of N fertilizers as urea: recommended dose N (134 kg N ha− 1), 25

Emissions of hydrogen (H2) gas from human activities are associated with indirect climate warming effects. As the hydrogen economy expands globally (e.g. the use of H2 gas as a fuel), the anthropogenic release of H2 into the atmosphere is expected to rise rapidly as a result of increased leakage. The dominant H2 removal process is uptake into soils; however, removal mechanisms are poorly understood, and the fate and impact of increased H2 emissions remain highly uncertain. Fluxes of H2 within soils are rarely measured, and data to inform global models are based on few studies. This study presents soil H2 fluxes from two field sites in central Scotland, a managed grassland and a planted deciduous woodland, with flux measurements of H2 covering full seasonal cycles. A bespoke flux chamber measurement protocol was developed to deal with the fast decline in headspace concentrations associated with rapid H2 uptake, in which exponential regression models could be fitted to concentration data over a 7 min enclosure time. We estimate annual H2 uptake of -3.1±0.1 and -12.0±0.4 kg H2 ha−1 yr−1 and mean deposition velocities of 0.012±0.002 and 0.088±0.005 cm s−1 for the grassland and woodland sites, respectively. Soil moisture was found to be the primary driver of H2 uptake at the grassland site, where the high silt/clay content of the soil resulted in anaerobic conditions (near zero H2 flux) during wet periods of the year. Uptake of H2 at the forest site was highly variable and did not correlate well with any localised soil properties (soil moisture, temperature, total carbon and nitrogen content). It is likely that the high silt/clay content of the grassland site (55 % silt, 20 % clay) decreased aeration when soils were wet, resulting in poor aeration and low H2 uptake. The well-drained forest site (60 % sand) was not as restricted by exchange of H2 between the atmosphere and the soil, showing instead a large variability in H2 flux that is more likely to be related to heterogeneous factors in the soil that control microbial activity (e.g. labile carbon and microbial densities). The results of this study highlight that there is still much that we do not understand regarding the drivers of H2 uptake in soils and that further field measurements are required to improve global models.

Smallholder farmers produce over 40% of global palm oil, the world’s most traded and controversial vegetable oil. Awareness of the effects of palm oil production on ecosystems and human communities has increased drastically in recent years, with ever louder calls for the private and public sector to develop programs to support sustainable cultivation by smallholder farmers. To effectively influence smallholder practices and ensure positive social outcomes, such schemes must consider the variety in perspectives of farmers and align with their priorities. We conducted social surveys on smallholder farmers in Indonesia and Malaysia with varying degrees of participation in programs that offer advice and support with plantation management (“management-assistance programs”) led by an industrial palm oil producer in Indonesia and a conservation-focused NGO in Malaysia. We surveyed farmers on their demographics, attitudes, and management decisions. Our analyses act as case studies to investigate the similarities and differences between smallholder palm oil producers involved in different schemes, allowing us to determine the alignment between the intentions of partnership programs and the current realities of smallholder plantations. The relationship between heterogeneity of social factors and management decisions and degree of program involvement differed across different groups and region: Indonesian smallholders most closely partnered with the private sector were the most varied in socio-demographics and attitudes but showed little variation in management inputs, while Malaysian smallholders most closely partnered with an NGO were the most heterogenous across all survey sections. Specifically, Indonesian farmers partnered with the private sector used less herbicide, more fertilizer, and had higher yield and total household income than farmers completely uninvolved with management assistance programs. In Malaysia, farmers partnered with an NGO also had higher yield and fertilizer application than independent farmers, however they used significantly more herbicide and had lower total household income. Our findings demonstrate the wide variety of smallholder farmers in both regions, directly opposing a ‘one-size-fits-all’ approach to sustainability. The wide variety of existing management practices also provides a potentially valuable natural experiment to identify high-yield, environmentally-friendly management approaches. When taken in context, our findings may inform the interventions of management-assistance programs, ensuring they are approaching the most relevant farmer groups in the most effective way.

The Indo-Gangetic Plain (IGP) faces significant challenges related to greenhouse gas (GHG) emissions and declining soil health due to intensive rice-based cultivation systems. This study evaluated the efficacy of enhanced efficiency fertilizers (EEF), including slow-release fertilizer (Sulphur-coated urea, SCU), and nitrification inhibitors (Neem-coated urea, NCU; Karanj-coated urea, KCU) in reducing GHG intensity and improving soil biological activity in rice systems in the IGP. Field experiments conducted over two years assessed yield parameters, GHG emissions, and indicators of soil microbial biomass, nutrient content, and enzymatic activity. NCU reduced CH4 emissions by 11 % and N2O emissions by 16.5 % relative to prilled urea (PU), while SCU and KCU also demonstrated notable emission reductions. Sulphur coated urea demonstrated the lowest greenhouse gas intensity (GHGi) (0.128 kg CO2-eq kg(-1) grain yield), followed by NCU and KCU. All EEFs significantly improved rice grain yield compared to PU, with SCU and KCU recording the highest mean yields (similar to 5600 and similar to 5560 kg ha(-1), respectively) versus 5010 kg ha(-1) under PU. Additionally, EEFs improved microbial biomass carbon and nitrogen, dehydrogenase activity, and reduced nitrate reductase and urease activity compared to conventional prilled urea (PU), with KCU and SCU showing the greatest improvements and highest net returns. Among the EEFs, SCU consistently achieved the highest yield, lowest GHGi, and overall improvements in soil health, making it a promising alternative for sustainable rice production. Projections indicate that while application of NCU in the IGP region during rice cultivation could reduce the GHGi by 12.2 % while adopting SCU may achieve a 25.8 % reduction, supporting India's commitment to the Paris Climate Agreement and promoting sustainable agricultural practices in the IGP.

Over the past century, the inefficient use of reactive nitrogen (Nr) has raised concerns regarding global food production and planetary sustainability. This study investigates nitrogen (N) losses in tomato production near Kabul, Afghanistan, aiming to improve nitrogen use efficiency (NUE) for enhanced food security and environmental protection. Three fertilizer treatments were tested: (A) animal manure + ¼ dose of chemical fertilizer, (B) night soil + ¼ dose of chemical fertilizer, and (C) full dose of chemical fertilizer, with sub-treatments varying in N application (25% less, 25% excess, and farmers’ practice). A no-fertilizer control treatment was included. Nitrogen losses through ammonia emissions and nitrate–N leaching were monitored, while nitrogen balances and NUE were calculated. The findings revealed that ammonia emissions decreased by 33% in treatment A2 and by 30% in treatment B3 compared to surface application. However, nitrate–N leaching peaked at 145 kg N ha−1 in A2 and 128 kg N ha−1 in B3, with positive N balances observed across treatments, the highest being 300 kg N ha−1 in treatment A. NUE ranged from 30% (A and B) to 55% (control), highlighting the widespread overapplication of N in Afghan agriculture. This study demonstrates that efficient N management practices can reduce environmental losses while maintaining tomato yield, offering a novel pathway toward sustainable farming in the region.

Forest ecosystems play an important role in the terrestrial nitrogen (N) cycle, accounting for over a quarter of the land area of the Earth. However, our understanding of nitrogen dynamics in forest systems is limited. The consequences of N deposition to forest ecosystems are often overlooked. In this study, dry deposition of NH3 was replicated over a two-year period in a temperate semi-natural birch forest via a unique custom-built automated NH3 release system to investigate the impact on emissions of the greenhouse gas nitrous oxide (N2O). This study provides evidence that in both natural forest soils (in-situ) and soils under controlled laboratory conditions (ex-situ), the substantial addition of reduced N compounds (NH3/NH4+) had no direct impact on N2O emissions. Emissions of N2O from these soils were dependant on the meeting of several additional thresholds, below which N2O producing activity was constrained. When environmental conditions in-situ were considered warm and wet (soil temperature >12 °C and volumetric water content >20 %), emissions of N2O were an order of magnitude higher than when either of these thresholds was not met, regardless of exposure to NH3 deposition. Ex-situ experiments indicated that microbial activity in the soils was highly constrained by the availability of labile carbon. The addition of glucose to these soils resulted in a considerable increase in N2O emissions after N application. While cumulative NH3 deposition to the in-situ soils was relatively large over the measurement period, there was no accumulation of mineral N observed in the soil, suggesting plant-uptake of N was able to mitigate N loading. The implication of these results is that forest ecosystems may be able to mitigate localised NH3 pollution plumes, in the short-term at least, without incurring an N2O penalty. However, the long-term impacts of N enhancement remain unclear and further long-term field experiments are required to examine the impact of prolonged exposure to high quantities of N deposition to forest soils.

This review paper discusses the potential and limitations of polymer composites for smart nitrogen (N) supply to meet the needs of agricultural crops. Unlike most conventional fertilizers, nano-clay polymer composites (NCPCs) offer a slow-release mechanism that enhances nitrogen use efficiency and reduces its loss to the environment. NCPCs are normally synthesized using solution blending, melt blending and in situ polymerization. Solution blending offers a better clay dispersion in the polymer matrix than melt blending owing to its low viscosity and strong stirring force. NCPCs have been characterized by several techniques, including equilibrium water absorbency, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and nutrient release kinetics. The potential benefits of using these composites are highlighted, including improved nitrogen use efficiency and reduced environmental impacts, as are their prospects for widespread use in agriculture and mitigation of the adverse environmental effects from conventional fertilizers. In addition, the limitations of NCPC technology, such as cost, scalability and potential negative environmental effects, are also investigated. The paper provides a wide perspective on the NCPC technology, including the regulatory environment and policy, industry trends and commercialization potential. NCPCs offer many benefits to increase nitrogen use efficiency and reduce pollution affecting water quality, air quality and climate. The main current barrier to overcome is to reduce production costs, so that farmers may also benefit financially from the higher nitrogen use efficiency and associated reduced amounts of nitrogen wasted to the environment.

Introduction: Leaching losses of applied N are an indirect source of nitrous oxide (N2O) emission, a major greenhouse gas emitted from fertilized soils. Mineral nitrogen (N) leaching research has largely concentrated on nitrate (NO3-), while ammonium (NH4+) leaching remains understudied. The cultivation conditions for rice and wheat are distinctly different, impacting the leaching losses of both NH4+ and NO3-. Methods: This study investigated the influence of different N treatments, i.e., no-N control, neem coated urea (NCU-N 100%; 120 kgN ha(-1)), 60 kgN ha(-1) Neem coated urea +30 kgN ha(-1) compost (75% N); 90 kgN ha(-1) Neem coated urea +30 kgN ha(-1) compost (100% N) and 120 kgN ha(-1) Neem coated urea +30 kgN ha(-1) compost (125% N) in comparison with prilled urea (PU, 120 kgN ha(-1)). Compost was applied @ 2.6 tonnes ha(-1) to all integrated treatments to provide 30 kgN ha(-1). Results and discussion: The peak concentration of soil NH4+ and NO3- was delayed by two-three days in NCU and integrated NCU + compost compared to PU in both rice and wheat, due to the slow-release effect of neem oil coating in NCU. In rice, the percolation rate of water was almost half than in wheat soil. The mineral N leaching loss in rice ranged from 0.4 to 4.6 kg NH4+-N ha(-1) and 0.46-5.12 kg NO3-N ha(-1) during the 2 years. In an annual rice-wheat cycle, the total N leaching loss was 6.2%-7.0% of the applied N fertilizer. The total mineral N loss was higher in PU than NCU by 7.8% and 10% in rice and wheat, respectively. Substitution of 25% of mineral N with compost decreased the total N leaching by 14.8% and 10.3% in rice and wheat, respectively, compared to NCU (100%). The crop N uptake increased significantly (p < 0.05) with NCU and integrated NCU + compost (100%) over PU. Application of 125%-N significantly increased the total mineral N leaching. The total mineral-N leaching loss was 15.9% higher in rice than wheat across the different treatments. The integrated N application, combining 75% NCU and 25% compost, can reduce mineral-N leaching, improve nitrogen uptake and maintain economic yields in rice-wheat cropping system.

This programme examines the climate and air quality implications of transitioning from fossil fuels to hydrogen-based energy systems. It comprises three independent projects – ELGAR, HECTER and COSH-AIR – that investigate various aspects of hydrogen usage and its effects on the atmosphere. The research explores future global and UK energy scenarios, focusing on the development of hydrogen infrastructure and the potential for fugitive hydrogen emissions. It also examines the role of microbial soil processes in removing atmospheric hydrogen, as well as the impacts of hydrogen deployment on climate and air quality. This overview will provide a summary of the research undertaken and the insights gained throughout the programme.

Flux chamber methodologies are used at the global scale to measure the exchange of trace gases between terrestrial surfaces (soils) and the atmosphere. These methods evolved as a simplistic necessity to measure gas fluxes from a time when gas analysers were limited in capability and costs were prohibitively high, since which thousands of studies have deployed a wide variety of chamber methodologies to build vast datasets of soil fluxes. However, analytical limitations of the methods are often overlooked and are poorly understood by the flux community, leading to confusion and misreporting of observations in some cases. In recent years, the number of commercial suppliers of gas analysers claiming to be capable of measuring trace gas fluxes from chambers has drastically increased, with a myriad of analysers (and low-cost sensors) now on offer with a wide variety of capabilities. While chamber designs and the capabilities of analysers vary by orders of magnitude, the rudimentary analytical uncertainties of individual flux measurements can still be standardised for direct comparison of methods. This study aims to serve as a guide to calculate the analytical uncertainty of chamber flux methodologies in a standardised way for direct comparisons. We provide comparisons of a variety of chamber measurement methodologies (closed static and dynamic chamber methods) to highlight the impact of analytical noise, chamber size, enclosure time and number of gas samples. With the associated tools, researchers, commercial suppliers and other stakeholders in the flux community can easily estimate the limitations of a particular methodology to establish and tailor the suitability of particular chambers and instruments to experimental requirements.

Ammonia (NH _3 ) volatilization and nitrate leaching are significant pathways of reactive nitrogen (N r ) losses in agriculture, leading to environmental concerns. This study investigates nitrogen (N) losses in wheat production near Kabul, Afghanistan, aiming to improve nitrogen use efficiency (NUE) for food security and environmental protection. Three fertilizer treatments were tested: (A) animal manure (2 t h ^−1 ) + 50% chemical fertilizer (urea and diammonium phosphate, DAP), (B) night soil (2 t ha ^−1 ) + 50% chemical fertilizer, and (C) full dose of chemical fertilizer, with sub-treatments varying in N application (25% less, 25% excess, and farmers’ practice). A no-fertilizer control treatment was included. Ammonia emissions and nitrate-N (NO _3 -N) and ammonium (NH _4 -N) leaching were monitored, and NUE was calculated. Subsurface application (treatment A _2 ) reduced ammonia emissions by 41.82% compared to 55% in surface applications (treatment A _3 ) and 15% in control plots. Ammonium-N losses were lower in subsurface application (31%) than surface applications (53%). NUE was highest in surface application (103%) and lowest in subsurface (84%). Moreover, Partial Factor Productivity (PFP) was higher in treatments with 25% less N compared to those with 25% excess and conventional practice. The novelty of this study lies in the implementation of subsurface application techniques to reduce N losses and enhance NUE in this region, where such techniques are rarely used. These results offer a model for improving NUE by optimizing fertilizer and manure inputs, applicable to similar agricultural systems globally.

An improved quantification of the soil sink of Hydrogen (H2) gas is required to understand the environmental implications of a future Hydrogen economy and global atmospheric models. Typically, soil microbes utilise H2 as an energy source, but we also have evidence that emission of H2 from soils is also possible via microbial processes. We present new H2 flux data from several field sites and lab studies in which a variety of soils from around the world have been measured from. These sites include agricultural and forest soils from the UK where we have preliminary data of a longer-term measurement campaign. We have developed flux chamber methodology to establish a best practice for measuring H2 flux in soils, which is radically different from typical greenhouse gas protocols. We present our work so far on the development of H2 measurement methodology and on the characterisation of the H2 soil sink in relation to soil physical & chemical properties, vegetation and climate under controlled environment conditions. We also present observations of spatial and temporal soil H2 uptake rates from sites across the UK. We highlight the importance of soil aeration and the physical barriers that strongly interfere with H2 uptake in soils, particularly the influence of high water-filled pore space which should be accounted for in future modelling efforts.