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Adequately estimating soil nitrous oxide (N2O) emissions using static chambers is challenging due to the high spatial variability and episodic nature of these fluxes. This paper discusses how static chamber N2O experiments can be designed, and protocols implemented, to better account for this variability and reduce the uncertainty of N2O emission estimates. It is part of a series of papers in this special issue, each discussing a particular aspect of N2O 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 in terms of individual chamber closures and overall experiment duration) affect the temporal variability captured. In addition, we present best practice recommendations for experimental chamber installation and sampling protocols to minimise the introduction of further uncertainty. To obtain the best N2O emission estimates, resources should be allocated to minimise the overall uncertainty in line with experiment objectives. In some cases, this will mean prioritising individual flux measurements and increasing their accuracy and precision by, for example, collecting ≥4 headspace samples during each chamber closure. However, where N2O fluxes are exceptionally spatially variable, for example, 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 N2O 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 N2O fluxes

Nitrous oxide (N2O) is an air pollutant of major environmental concern, with agriculture representing 60% of anthropogenic global N2O emissions. Much of the N2O emissions from livestock production systems result from transformation of N deposited to soil within animal excreta. There exists a substantial body of literature on urine patch N2O dynamics, we aimed to identify key controlling factors influencing N2O emissions and to aid understanding of knowledge gaps to improve GHG reporting and prioritize future research. We conducted an extensive literature review and random effect meta‐analysis (using REML) of results to identify key relationships between multiple potential independent factors and global N2O emissions factors (EFs) from urine patches. Mean air temperature, soil pH and ruminant animal species (sheep or cow) were significant factors influencing the EFs reviewed. However, several factors that are known to influence N2O emissions, such as animal diet and urine composition, could not be considered due to the lack of reported data. The review highlighted a widespread tendency for inadequate metadata and uncertainty reporting in the published studies, as well as the limited geographical extent of investigations, which are more often conducted in temperate regions thus far. Therefore, here we give recommendations for factors that are likely to affect the EFs and should be included in all future studies, these include the following: soil pH and texture; experimental set‐up; direct measurement of soil moisture and temperature during the study period; amount and composition of urine applied; animal type and diet; N2O emissions with a measure of uncertainty; data from a control with zero‐N application and meteorological data., Meta‐analysis of published data on emissions factors from urine revealed that animal type, soil pH and mean air temperature had significant effects on N2O emissions. We also identified a lack of reporting of key factors with the potential to impact emissions factors so their effect on N2O emissions could not be determined, for example, soil temperature, soil moisture and urine composition. There was also an under representation of certain geographical regions within the literature.

Slurry acidification has been shown to be effective in reducing environmentally damaging gases. However, this involved the use of concentrated acids on farms. Therefore, due to the health and safety concerns, there is an interest in self-acidification of slurry technique. This study was designed to determine the microbial dynamics leading to self-acidification of slurry. A fresh cattle slurry was amended 10% brewing sugar and stored over 30 days. This fermentable carbon source promoted self-acidification of the slurry from pH 7.0 to 4.7 within four days, and was associated with the accumulation of lactic acid and a reduction in methane and relative ammonia emissions. A metagenomics approach through next generation sequencing (NGS) using an Illumina MiSeq platform was used to determine the microbial diversity and dynamics (bacteria and archaea) in the stored amended slurry. 16S ribosomal ribonucleic acid (rRNA) sequence data revealed the presence of the Order of

Drainage and cultivation of peat soils almost always result in rapid soil degradation and a loss of soil organic matter (SOM). Winter cover crop cultivation and subsequent incorporation and watertable elevation have been considered as potential strategies to improve soil quality and decrease nutrient loss in drained and cultivated peatlands. However, the combined effect of residue incorporation and watertable management on greenhouse gas (GHG) emissions in these highly productive fen peat soils remains unknown. In the present study, two winter cover crops with contrasting carbon/nitrogen ratios (vetch [Vicia sativa], 45–60; rye [Secale cereale], 13–14) were incorporated into peat soils as green manure (without extra synthetic/organic N addition) at two watertable depths (−50 and −30 cm). Our results showed that fast mineralization of incorporated residues can cause a large pulse of GHG release under favourable environmental conditions. Both vetch and rye incorporation increased CO₂ emissions compared with the bare soil treatments due to labile C addition and removal of N constraints. However, the two cover crops had strongly contrasting effects on N₂O emissions. Incorporation of low C/N ratio vetch stimulated N₂O emissions (average 21.8 ± 7.3 mg N m⁻² hr⁻¹) compared with the bare soil treatments, whereas high C/N ratio rye decreased N₂O emissions (average 0.09 ± 0.03 mg N m⁻² hr⁻¹). Raising the watertable slightly reduced CO₂ emissions from an average of 1.3 ± 0.4 (the bare soils) to 0.9 ± 0.3 g C m⁻² hr⁻¹ by inhibiting SOM mineralization but significantly increased N₂O emissions in the vetch treatments by stimulating denitrification. CH₄ fluxes were not affected by watertable depth, and their contribution to total global warming potential was negligible. Therefore, we conclude that high C/N ratio cover crops (e.g., rye) in combination with a raised watertable may represent a viable management option to mitigate GHG fluxes in fen peat soils.

Evidence suggests that climate change is increasing the frequency of extreme weather events (e.g. excessive rainfall, heat, wind). The winter of 2013-14 saw exceptional levels of rainfall across the UK leading to extreme and prolonged flooding (up to 3 months with floodwater depths up to 3 m) in several low-lying agricultural areas (e.g. Somerset Levels, Thames Valley). The impact of extreme flooding and the speed of ecosystem recovery at the field-scale, however, remain poorly understood. The main objectives of this study were therefore to: (1) assess the effect of this extreme winter flooding event on a range of soil physical, chemical and biological quality indicators at 15 flood-affected sites (arable and grassland), (2) determine if these changes in soil health were reversible in the short term (

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., Graphical abstract Unlabelled Image, Highlights • N2O emissions and NUE were measured at 5 UK grassland sites. • Different fertilisation rates and strategies were tested in all sites. • Average N2O emission factor was 1.12%, but ranged from 0.60% to 2.08%. • Using urea and urea with DCD reduced N2O emission factor. • Yield scaled emissions and emissions relative to herbage N content show similar trend.

Soils around the world are being exposed to weather events which are unprecedented in recent history. To maintain the delivery of soil-related ecosystem services and to promote greater soil resilience it is essential to understand how plant-soil systems respond to these extreme events. In this study we replicated a recent period of extreme rainfall and prolonged spring flooding in a temperate grassland which had no previous history of flooding. Intact soil mesocosms (Eutric Cambisol) 1 kg weight were subjected to a simulated long-term spring flood (15 °C, 2 months) and maintained in the light with above ground indigenous vegetation (Lolium perenne L.) or dark with and without indigenous vegetation to simulate different flood typologies. In comparison to a no-flood control treatment, nutrient cycling, water quality, air quality (greenhouse gas emissions), habitat provision and biological population regulation shifts were evaluated. Flooding induced a rapid release of nutrients into the soil solution and overlying floodwater, resulting in potential nutrient losses up to 15 mg Fe, 16 mg NH4+, 360 mg DOC and 28 mg DON, per mesocosm. The presence of plants increased the rate of nutrient release (especially P), with the effects magnified when light transmission through the floodwater was restricted (1.3 mg P vs 0.2 mg P, per mesocosm). Flooding induced a rapid decline in redox potential and subsequent production of CH4, especially in the darkened treatments (10 and between 11 and 16 times higher than the control, without and with light restrictions, respectively). Upon removal of the floodwater, the accumulated NH4+ was nitrified leading to a shift in greenhouse gas emissions, from CH4 to N2O emissions. N2O was only significantly produced in the mesocosms kept under light restrictions (13 times higher than in other two treatments). Flooding eliminated earthworms, reduced grass production after soil recovery (from 28 g for control mesocosms to 11 g and

This study investigated the effects of phosphogypsum, superphosphate, and dicyandiamide on gaseous emission and compost quality during sewage sludge composting. Results showed that phosphogypsum reduced ammonia (NH3) and methane (CH4) emissions but increased nitrous oxide (N2O) emission. Superphosphate simultaneously reduced NH3, N2O and CH4 emissions. Dicyandiamide markedly reduced N2O emission during composting. Combination of phosphogypsum and dicyandiamide reduced CH4 and N2O emissions by 75.6% and 86.4%, while NH3 emission was increased by 22.0%. Combination of superphosphate and dicyandiamide reduced NH3, CH4 and N2O emissions by 12.3%, 81.0% and 88.2%, respectively. More importantly, with the addition of 10% initial raw materials, phosphogypsum and superphosphate conserved nitrogen and improved compost quality by introducing additional nutrients.

Understanding the change in function of the biological community under different soil conditions is key to effective soil quality monitoring and mitigation of soil degradation. Current measures of biological soil quality suffer from drawbacks with most techniques having high expense, low throughput or a narrow focus on one component of the community. The aim of this study was to assess the use of volatilomics as a method to profile the soil microbial community and compare the technique to phospholipid fatty acid (PLFA) profiling as a measure of biological soil quality. An agricultural grassland soil (Eutric Cambisol) was subjected to a range of stresses in replicate laboratory mesocosms. Treatments included the imposition of hypoxia/anoxia by flooding with freshwater or saltwater in the presence or absence of plant residues. The volatile organic compound (VOC) and PLFA profile of each treatment was then compared to unamended mesocosms. We hypothesized that the VOC fingerprint of soil would be highly responsive to changes in microbial metabolic status/functioning and thus provide a complementary approach to PLFAs for evaluating soil biological health. We also hypothesized that the VOC profile would have greater discriminatory power than PLFAs for determining differences between soil treatments. A headspace solid phase microextraction (HSSPME) method coupled with gas chromatography quadrupole-time of flight mass spectrometry (GC/Q-TOFMS) was used to analyse the broad spectrum of VOCs produced by each soil. Across all soil treatments 514 unique VOC peaks were detected. Overall, VOCs showed greater sensitivity than the PLFA analysis in separating soil quality treatments. Eighteen individual VOCs were identified which were primarily responsible for this separation (e.g. indole, α-ionone, isophorone, 3-octanone, p-cresol, 2-ethyl-phenol). Anaerobic soils amended with residues showed the greatest separation from other treatments, with most of this differentiation associated with ten individual VOCs. The anaerobic soils also showed a significant reduction in the number of VOCs emitted but an increase in total VOC emissions. In conclusion, our findings provide evidence that soil VOCs rapidly respond to changes in soil quality and therefore hold great potential as a novel functionally relevant diagnostic measure of biological soil quality.

Nitrification inhibitors (NIs) have been shown to be an effective tool to mitigate direct N2O emissions from soils. However, emerging findings suggest that NIs may increase soil ammonia (NH3) volatilization and, subsequently, indirect N2O emission. A quantitative synthesis is lacking to evaluate how NIs may affect NH3 volatilization and the overall N2O emissions under different environmental conditions. In this meta-analysis, we quantified the responses of NH3 volatilization to NI application with 234 observations from 89 individual studies and analysed the role of experimental method, soil properties, fertilizer/NI type, fertilizer application rate and land use type as explanatory factors. Furthermore, using data sets where soil NH3 emission and N2O emission were measured simultaneously, we re-evaluated the effect of NI on overall N2O emissions including indirect N2O emission from NH3 volatilization. We found that, on average, NIs increased NH3 volatilization by 35.7% (95% CI: 25.7–46.7%) and increased indirect N2O emission from NH3 emission (and subsequent N deposition) by 2.9%–15.2%. Responses of NH3 volatilization mainly varied with experimental method, soil pH, NI type and fertilizer type. The increase of NH3 volatilization following NI application showed a positive correlation with soil pH (R2 = 0.04, n = 234, P < 0.05) and N fertilizer rate (R2 = 0.04, n = 187, P < 0.05). When the indirect N2O emission was considered, NI’s N2O mitigation effect decreased from 48.0% to 39.7% (EF = 1%), or 28.2% (EF = 5%). The results indicate that using DMPP with ammonium-based fertilizer in low pH, high SOC soils would have a lower risk for increasing NH3 volatilization than using DCD and nitrapyrin with urea in high pH, lower SOC soil. Furthermore, reducing N application rate may help to improve NIs’ overall N2O emission mitigation efficiency and minimize their impact on NH3 volatilization.

Greenhouse gas (GHG) fluxes from livestock grazed pasture soils are highly variable in both space and time but the quantitative importance of the factors regulating this variation remain poorly understood. Our aim was to explore this variability on contrasting extensively (low input) and intensively managed sheep-grazed ‘case-study’ pastures. We quantified (through standard and spatially-informed regressions) the statistical relationships between GHG fluxes (nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4)) and a range of soil, field and management characteristics. Fluxes of these three GHGs at two study sites were highly variable, but spatial structure (i.e. autocorrelation) was only observed in the variability of N2O fluxes across the intensive site and CO2 fluxes across the extensive site. The regression analyses identified significant GHG predictor variables for the extensive site as: NO3- (p < 0.001) and vegetation-type (p < 0.01) for N2O (R2 = 0.57; p = 0.000); NH4+ (p < 0.05), slope (p < 0.05) and elevation (p < 0.01) for CO2 (R2 = 0.34; p = 0.000); and NO3- (p < 0.01), NH4+ (p < 0.05) and soil moisture (p < 0.05) for CH4 (R2 = 0.25; p = 0.005). Significant GHG predictor variables for the intensive site were soil moisture (p < 0.01) and bulk density (p < 0.01) for N2O (R2 = 0.27; p = 0.005); soil moisture (p < 0.001) for CO2 (R2 = 0.31; p = 0.001); while none were found for CH4 (R2 = 0.10; p = 0.655). Key factors driving GHG variation were both site- and GHG-specific, with fluxes controlled by local conditions leading to differences in limiting factors (possibly even at the within-site scale). Our statistical analyses suggest a larger range of driving variables (e.g. air and soil temperature or other soil chemical properties such as total extractable N) may be required to more fully capture the observed variability in the GHG processes considered here, and that it may also be fruitful for future analyses to consider non-linear, non-stationary and interacting relationships across space- and time-scales. Adequacies of each site’s sample design also played a key interpretive role in the GHG processes, requiring further evaluation through additional sampling campaigns.

Excess chemical fertilizer application results in substantial N2O emission. Manure application into agricultural soil can reduce chemical fertilizer input while maintaining crop yield. However, little is known about the potential effects of reduction in chemical fertilizer with green manure or organic manure on yield-scaled N2O emissions in orchards. A two-year experiment was carried out in a citrus orchard, including (i) chemical fertilizer (urea), 0%, 70%, 85% and 100% of N supplied, respectively (CK, C70, C85, CF), (ii) organic manure (rapeseed cake) incorporation with 0%, 70%, 85% and 100% of N supplied from chemical fertilizer (OM, OMC70, OMC85, OMCF), (iii) green manure (smooth vetch) incorporation with 0%, 70%, 85% and 100% of N supplied from chemical fertilizer (GM, GMC70, GMC85, GMCF) treatments. The soil physical-chemical properties, N2O emissions and yields were measured during 2018–2019. N2O emissions were 1.57 and 1.80 kg N ha−1 yr−1 under CF treatment in 2018 and 2019, respectively, and decreased by 25.4%−31.6% under C70, 32.5%−55.4% under OMC70 and OMC85 treatments and by 16.1–32.2% under GMC70 and GMC85 treatments. The 70% N rate of chemical fertilizer was the optimal N rate for maximizing yield in no manure, organic manure and green manure treatments, respectively. The C70, OMC70 and GMC70 treatments both significantly decreased yield-scaled N2O emission with the lowest emission in OMC70 treatment relative to CF treatment. N2O fluxes in OMC70 and OMC85 treatments were mainly controlled by the DOC/NO3- ratio, while soil NH4+ was the dominant factor controlling N2O fluxes in GMC70 and GMC85 treatments, suggesting that more NH4+ provided from green manure than from organic manure contributed to higher N2O emission. We conclude that applying organic manure incorporation with 30% reductions of chemical fertilizer is a fertilizer management strategy worth pursuing for sustainable productivity and environmental protection in citrus orchards.

Microbial communities in agricultural soils underpin many ecosystem services including the maintenance of soil structure, food production, water purification and carbon storage. However, the impact of fertilization on the health of microbial communities is not well understood. This study investigates the spatial and temporal dynamics of nitrogen (N) transport away from a fertilizer granule with pore scale resolution. Specifically, we examined how soil structure and moisture content influence fertilizer derived N movement through the soil pore network and the subsequent impact of on soil microbial communities. We develop a mathematical model to describe N transport and reactions in soil at the pore-scale. Using X-ray Computed Tomography scans, we reconstructed a microscale description of a soil-pore geometry as a computational mesh. Solving two-phase water/air model produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The N-speciation model considered ammonium (NH4+), nitrate (NO3−) and dissolved organic N (DON), and included N immobilization, ammonification and nitrification processes, as well as diffusion in soil solution. We simulated the dissolution of a fertilizer pellet and a pore scale N cycle at three different water saturations. To aid interpretation of the model results, microbial activity at a range of N concentrations was measured. The model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predict that the maximum NH4+ and NO3− concentrations in soil solution around the pellet under dry conditions are in the order of 1 × 103 and 1 × 104 mol m−3 respectively, and under wet conditions 2 × 102 and 1 × 103 mol m−3, respectively. Supporting experimental evidence suggests that these concentrations would be sufficient to reduce microbial activity in the short-term in the zone immediately around the fertilizer pellet (ranging from 0.9 to 3.8 mm), causing a major loss of soil biological functioning. This model demonstrates the importance of pore-scale processes in regulating N movement and their interactions with the soil microbiome.

Microplastics represent an emerging threat to terrestrial ecosystems, however, our understanding of the fate and behaviour of microplastics in the plant-soil system remains poor. In this replicated, field-scale study we added microplastics (low density polyethylene) to soil at different dose rates representing contamination levels ranging from 0 to 10 t ha-1. These levels were chosen to cover both agricultural and urban contamination levels. Over a 12 month period, we studied a range of chemical, physical and biological soil quality indicators and wheat productivity to evaluate the impact of microplastics on the delivery of soil-related ecosystem services. Overall, we found little evidence to suggest that microplastics affect plant growth even at high dose rates. In contrast, microplastics had a significant impact on soil quality. The use of PLFA profiling and 16S metabarcoding of the bacterial and archaeal community, revealed changes in key microbial taxa at high microplastic doses. In addition, physiological profiling of the microbial community using lipidomics, untargeted metabolomics and targeted nitrogen metabolomics (using GC-MS platform) revealed significant shifts in microbial physiology. No appreciable effect of microplastics was seen on soil N and P dynamics, earthworm abundance or greenhouse gas emissions (CO2, N2O and CH4). Overall, our results suggest that microplastics do induce changes in soil quality, but that this has little overall effect on the delivery of key soil-related ecosystem services. These results contrast strongly with experiments performed in laboratory mesocosms where microplastics negatively affected plant growth and soil quality, and highlight the need to study the impact of microplastics at the field scale over longer timescales.

Urine patches in grassland ecosystems present unique environments where extreme nitrogen (N) loading occurs. This results in N losses into the atmosphere or leaching from soil. N losses vary due to climate conditions, soil conditions, and management practices. However, we do not fully understand how these factors influence N cycling and nitrous oxide (N2O) emissions from urine patches. Much of the current literature on urine patch N cycling has focused on typical lowland agricultural systems. Very little work has explored other grazing systems, such as upland farming which is conducted across much of Wales. We have investigated this by using a catena sequence crossing both upland and lowland agricultural grazing systems. The range of soil types allowed us to explore how N2O emissions and N losses vary under different conditions. Here we report on both a laboratory incubation and a mesocosm experiment examining these issues. This work should help to fill the knowledge gap around how emissions from urine patches could vary between UK uplands and lowlands. We hope to improve understanding of N losses and provide more realistic, regional, and accurate emission factors for upland farming systems.

Global peatlands store >600 Gt of Carbon (C) but are highly vulnerable to degradation following drainage for agriculture. The extensively drained East Anglian Fens include half of England’s most productive agricultural land, produce ~33% of England’s vegetables and support a food production industry worth approximately £3 billion GBP. However under arable management, these fen peat soils produce ~37.5 t CO2 eq ha-1 of total greenhouse gas (GHG) emissions annually. This is likely to be the largest source of land use GHG emissions in the UK per unit area and there is interest in developing responsible management approaches to reduce emissions whilst maintaining economically productive systems. Lettuce (Lactuca sativa) is amongst the UK’s most valuable crops and a substantial proportion of UK production occurs in the Fens. We undertook a life cycle assessment to compare the carbon footprint of UK Fen lettuce with alternative sources of lettuce for the UK market. We also examined the potential for responsible peat management strategies and more efficient production to reduce the carbon footprint of Fen lettuce. It is hoped this study will help to inform land use decision making and encourage responsible management of UK lowland peat resources.

Made available in DSpace on 2020-12-10T19:44:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) FAPEG Goids Research Foundation FAPEMA Maranhao Research Foundation Biotechnology and Biological Sciences Research Council Part of the nitrogen (N) fertilizer applied to crops is lost to the environment, contributing to global warming, eutrophication, and groundwater contamination. However, low N supply stimulates soil organic N turnover and carbon (C) loss, since the soil N/C ratio in soil is quasi-constant, ultimately resulting in land degradation. Grasses such as ruzigrass (Urochloa ruziziensis) grown as winter pasture or a cover crop in rotation with maize (Zea mays) can reduce N leaching, however, this may induce N deficiency and depress yields in the subsequent maize crop. Despite the potential to decrease N loss, this rotation may negatively affect the overall N balance of the cropping system. However, this remains poorly quantified. To test this hypothesis, maize, fertilized with zero to 210 kg N ha(-1), was grown after ruzigrass, palisade grass (Urochloa brizanta) and Guinea grass (Pannicum maximum), and the N inputs, outputs and partial N balance determined. Despite the intrinsically poor soil quality associated with the tropical Ultisol, maize grown after the grasses was efficient in acquiring N, resulting in a negative N balance even when 210 kg ha(-1) of N was applied after Guinea grass. Losses by leaching, N2O emission and NH3 volatilization did not exceed 13.8 kg ha(-1) irrespective of the grass type. Despite a similar N loss among grasses, Guinea grass resulted in a higher N export in the maize grain due to a higher yield, resulting in a more negative N balance. Soil N depletion can lead to C loss, which can result in land degradation. Sao Paulo State Univ, Sch Agr Sci, Dept Crop Sci, Univ Av 3780, BR-18610034 Botucatu, SP, Brazil Bangor Univ, Sch Nat Sci, Bangor LL57 2UW, Gwynedd, Wales Univ Western Australia, UWA Sch Agr & Environm, Crawley, WA 6009, Australia Univ Nottingham, Fac Sci, Div Agr & Environm Sci, Sutton Bonington Campus, Loughborough LE12 SRB, Leics, England Sao Paulo State Univ, Sch Agr Sci, Dept Crop Sci, Univ Av 3780, BR-18610034 Botucatu, SP, Brazil FAPESP: 2015/50305-8 FAPEG Goids Research Foundation: 2015-10267001479 FAPEMA Maranhao Research Foundation: RCUK-02771/16 Biotechnology and Biological Sciences Research Council: BB/N013201/1

Composting technology is widely used and different technologies have been applied from static heap to windrow composting, and to intelligent reactor composting since the rapid development of landless intensive livestock farms and improved awareness of environmental impacts. However, the lack of a systematic analysis has limited the objective evaluation of these different technologies from the perspective of treatment efficiency, and environmental and economic benefit. This study aimed to use quantitative data from full-scale composting systems (static heap, windrow composting and reactor composting with 8 t treatment capacity per day) installed on a commercial pig farm (6000 head) to compare their treatment efficiency, nutrient losses, product quality and investment and operational costs. The results showed that fresh feedstock entered the thermophilic phase in reactor composting much more quickly (within a few hours) than the other composting methods, and maintained a relatively stable high temperature (55–65 °C). This improved the biodegradation process and shortened the composting period. Within the first week, the organic matter degradation in the reactor composting treatment reached 35.7%, significantly greater than for the other treatments. Rapid heating and sustained high temperature promoted the removal rates of the antibiotics tetracycline, doxycycline and sulfamethoxazole. More than 90% of these antibiotics were degraded in the reactor composting treatment, and antibiotic resistance gene abundance was significantly reduced by 79% after composting. Nitrogen loss from the reactor composting was 34% less compared with windrow composting. Although the reactor composting has a higher equipment cost and greater depreciation than the other composting technologies, the total investment and operational costs are comparable to windrow composting. Moreover, with low nitrogen loss, high antibiotic and resistance gene removal rates, reactor composting has benefits regarding nutrient use efficiency and environmental impact.

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.

As the demand for livestock products continues to increase in China, so too does the challenge of managing increasing quantities of manure. Urgent action is needed to control point source (housing, storage and processing) and diffuse (field application) pollution and improve the utilization of manure nutrients and organic matter. Here, we review strategies to improve management at each stage of the manure management chain and at different scales. Many strategies require infrastructure investment, e.g., for containment of all manure fractions. Engineering solutions are needed to develop advanced composting systems with lower environmental footprints and design more efficient nutrient stripping technologies. At the field-scale, there is an urgent need to develop a manure nutrient recommendation system that accounts for the range of manure types, cropping systems, soils and climates throughout China. At the regional scale, coordinated planning is necessary to promote recoupling of livestock and cropping systems, and reduce nutrient accumulation in regions with little available landbank, while minimizing the risk of pollution swapping from one region to another. A range of stakeholders are needed to support the step change and innovation required to improve manure management, reduce reliance on inorganic fertilizers, and generate new business opportunities.

Excreta deposition onto pasture, range and paddocks (PRP) by grazing ruminant constitute a source of nitrous oxide (N2O), a potent greenhouse gas (GHG). These emissions must be reported in national GHG inventories, and their estimation is based on the application of an emission factor, EF3PRP (proportion of nitrogen (N) deposited to the soil through ruminant excreta, which is emitted as N2O). Depending on local data available, countries use various EF3PRPs and approaches to estimate N2O emissions from grazing ruminant excreta. Based on ten case study countries, this review aims to highlight the uncertainties around the methods used to account for these emissions in their national GHG inventories, and to discuss the efforts undertaken for considering factors of variation in the calculation of emissions. Without any local experimental data, 2006 the IPCC default (Tier 1) EF3PRPs are still widely applied although the default values were revised in 2019. Some countries have developed country-specific (Tier 2) EF3PRP based on local field studies. The accuracy of estimation can be improved through the disaggregation of EF3PRP or the application of models; two approaches including factors of variation. While a disaggregation of EF3PRP by excreta type is already well adopted, a disaggregation by other factors such as season of excreta deposition is more difficult to implement. Empirical models are a potential method of considering factors of variation in the establishment of EF3PRP. Disaggregation and modelling requires availability of sufficient experimental and activity data, hence why only few countries have currently adopted such approaches. Replication of field studies under various conditions, combined with meta-analysis of experimental data, can help in the exploration of influencing factors, as long as appropriate metadata is recorded. Overall, despite standard IPCC methodologies for calculating GHG emissions, large uncertainties and differences between individual countries' accounting remain to be addressed.

A large number of sheep graze extensively managed grasslands, including upland and hill areas. Excretal deposition of nitrogen (N) to upland soil is a potentially large source of the powerful greenhouse gas (GHG), nitrous oxide (N2O), however, few studies have assessed urine-patch N2O emissions from upland areas. Current default excretal N2O emission factors (EFs) are based on intensively managed lowland systems, with cattle excreta as the N source. We hypothesised that N2O emissions could differ substantially from those of lowland systems, due to differences in soil type, climate, topography, pasture composition and management factors along altitudinal and productivity gradients. We investigated N2O emission factors across two seasons (spring and autumn), for an extensive semi-improved, temperate grassland using IPCC-compliant and representative sheep urine patches (in terms of urine chemical composition, urine patch size and N loading rates). An automated GHG monitoring system provided high-frequency GHG data from sheep urine patches (756 and 1112 kg N ha−1 applied in spring and autumn, respectively), reference artificial sheep urine patches (1066 and 1004 kg N ha−1 applied in spring and autumn, respectively) and control treatments. In spring, urine patch N2O emission factors were −0.02 ± 0.04 (artificial sheep urine) and 0.03 ± 0.09% (real sheep urine) of the applied N; in autumn emission factors were 0.02 ± 0.03 (artificial sheep urine) and 0.08 ± 0.04% (real sheep urine) of the applied N. These values are much lower than default inventory values (1% of applied N) for excreta deposited by grazing livestock. There was a greater pasture foliar N content following urine application in spring as opposed to autumn, and a significantly longer residence time of extractable mineral N in autumn. Our findings demonstrate the importance of generating country-specific N2O EFs based on altitude/productivity gradients of livestock production, with implications for national inventories and the accuracy of sustainability metrics of lamb produced in the UK uplands.

Handling of digestate produced by anaerobic digestion impacts the environment through emission of greenhouse gases, reactive nitrogen, and phosphorus. Previous life cycle assessments (LCA) evaluating the extraction of nutrients from digestate using struvite precipitation and ammonia stripping did not relate synthetic fertilizer substitution (SFS) to nutrient use efficiency consequences. We applied an expanded LCA to compare the conventional management of 1 m3 of liquid digestate (LD) from food waste against the production and use of digestate biofertilizer (DBF) extracted from LD, accounting for SFS efficacy. Avoidance of CH4, N2O, and NH3 emissions from LD handling and enhanced SFS via more targeted use of nutrients in the versatile DBF product could generate environmental savings of up to 0.129 kg Sb eq, 4.16 kg SO2 eq, 1.22 kg PO4 eq, 33 kg CO2 eq, and 20.6 MJ eq per m3 LD, for abiotic resource depletion, acidification, eutrophication, global warming, and cumulative energy demand burdens, respectively....

Due to climate change, the frequency and duration of flood events are predicted to increase in many regions of the world. This is expected to cause large changes in soil functioning and to a progressive decline in soil quality such as reduced rates of nutrient cycling, enhanced greenhouse gas emissions and loss of soil biodiversity. There is a knowledge gap, however, on how temperate agricultural soils under different management practices (e.g. manure application) respond to prolonged river or coastal flooding. The main objective of this work was to determine the effects of a simulated prolonged flooding with saline and freshwater on soil N cycling, following application of a low C:N organic amendment (broiler litter) at two temperatures, representative of a winter and a spring flood event. Using laboratory mesocosms we simulated prolonged winter (6 °C) and spring (14 °C) flooding of soil amended with broiler litter. We also compared the effects of inundation with either river (freshwater) or coastal (saline) water. An agricultural grassland soil (Eutric Cambisol) was subjected to different combinations of treatments (flood with fresh or saline water, winter vs spring temperatures, with/without poultry manure). The impact of these treatments on soil solution N dynamics, greenhouse gas emissions (CO2, CH4, N2O) and microbial community structure (by PLFA analysis) were evaluated over an 11 week simulated flood event followed by an 8 week soil recovery period (without flood). Overall, potential losses of NH4+ and cumulative GHG emissions were increased by flooding and the presence of manure. CH4 emissions were found to dominate under freshwater flooding conditions and N2O under saline flooding. Significant releases of GHG occurred during both flooding and after floodwater removal. Temperature was less influential on regulating GHG under the different treatments. These releases in GHG were associated with disruption in N cycling and changes in soil microbial composition and these changes persisted after floodwater removal. Extreme flooding negatively impacts soil functioning, however, the magnitude of any changes remain critically dependent on flood duration and source of flood water, and management conditions. Further work is required at the field scale to understand the molecular basis of the responses observed in this study.

Livestock production in peri-urban areas constitutes an important sub-sector of the agricultural production system in China, and contributes to environmental degradation and local air borne pollution contributing to smog. As a result, local policies are being implemented to safeguard the environment. However, there has been little attempt to quantify the impact of environmental policies on livestock production structure, spatial distribution and their related greenhouse gases (GHGs) and ammonia (NH3) emissions. Here, we calculated the inventories of GHGs and NH3 emissions for 2010 and 2014 for peri-urban livestock production in Beijing, using reliable spatially explicit data, which was collected from 1748 industrial farms in 2010 and 2351 industrial farms in 2014, including pig, dairy, beef cattle, poultry and sheep farms. Our estimates indicated that total industrial livestock production increased by 17% between 2010 and 2014, even under the more strict environmental protection polices, with farm size decreasing by between 7% and 47%. Up to 50% of the industrial livestock farms have remained in operation, with the rest closing down or being moved to other regions. Following this trend, total GHGs emission decreased from 5.0 to 4.5 Tg CO2-eq between 2010 and 2014. Most of the GHGs emission reduction was due to the lowering of energy related carbon dioxide (CO2) emission in 2014. Total NH3 emission decreased from 102 to 96 Gg between 2010 and 2014, mainly due to more stringent environmental regulations for new and extended farms (increased in farm size), e.g. Discharge standard for pollutants for livestock and poultry breeding. Our study identified that GHGs and NH3 emission hotspots were concentrated in suburban areas (around the city centre and with less agricultural resource and population density) in 2010. However, between 2010 and 2014 these hotspots moved to the exurban plain and mountain area following the closure or sub-division of intensive farms in suburban regions and construction of new and small farms in exurban areas (around the suburban and with more agricultural resource and lower population density). Scenario analysis suggests that total GHGs emission can be reduced by up to 1.0 Tg CO2-eq (23% of total livestock sector emissions) in Beijing, using a combination of modifications of farm type, livestock diet and manure management. The integrated scenario can reduce CH4, N2O and NH3 emissions by 27%, 9% and 35%, compared to the reference scenario. Within this short period of time (5 years), policies have had direct impacts on peri-urban livestock production in Beijing, resulting in marked changes in the structure of different livestock sectors, as well as the GHGs and NH3 emission inventories and their spatial distribution. Our analysis clearly shows that the success of these (and future) polices relies on optimizing spatial management of new livestock production systems. Policy and farmer guidance should focus on optimizing livestock diet and on-farm manure management, industrial production systems and the pig and poultry sectors in peri-urban regions.

Agricultural soils are the primary source of nitrous oxide emissions due to management practices including fertiliser application. While fertiliser rates are one of the main drivers of nitrous oxide emissions, emissions are also dependent on other variables such as climate and soil properties. To understand the spatial and inter-annual variations in emission rate, simulations of N2O emissions were made from 2000 to 2010 for UK grass and croplands. In addition, the sensitivity of these emissions to soil and climate inputs was also tested. Emissions of between 0.3 to 3.5 kg N ha−1 yr−1 and 0.7–7 kg N ha−1 yr−1 were simulated across UK croplands and grasslands, respectively. While inter-annual variations can be attributed to climate influences, the primary driver of spatial variations in emissions was soil clay content. However, when the sensitivity of nitrous oxide emissions to soil clay content alone was tested, it was not always the best predictor of emissions, when soil texture is altered outside of the normal range used as inputs to the model from different databases.

Drained peatlands support highly profitable agriculture, but also represent a globally important source of greenhouse gas (GHG) emissions. Grasslands can typically be maintained at higher water levels than croplands, so conversion of cropland to grassland represents a potential CO2 mitigation strategy that allows for continued agricultural production. However, the presence of high water levels and livestock on grasslands risks generating high emissions of N2O, particularly associated with livestock urine patches. In the present study, a controlled mesocosm experiment was carried out to quantify the interactive impacts of groundwater level (10 cm, 30 cm and 50 cm water table depth, WTD) and sheep urine deposition on GHG emissions from peat soils. Our results showed that N2O emissions were significantly higher at 30 cm for both urine-treated and control mesocosms, due to the conditions favouring the interplay of nitrification and incomplete denitrification. The urine N2O emission factor was 0.25±0.17% at the 30 cm WTD and 0.20±0.07% at 50 cm WTD, lower than typical values for grasslands. No significant difference was observed in ecosystem respiration or methane flux between 30 cm and 50 cm WTDs. Overall, we conclude that strategies to raise water levels in drained peatlands through conversion of cropland to grassland need to account for the potential impacts of N2O emissions when seeking to minimise overall GHG emissions. Shifting from cropland to grassland management on peatlands for climate change mitigation also requires consideration of the effects of livestock methane emissions, and displaced emissions resulting from increased land demand for crop production elsewhere.

Climate change is expected to increase the frequency and severity of droughts in many regions of the world. Soil health is likely to be negatively impacted by these extreme events. It is therefore important to understand the impact of drought on soil functioning and the delivery of soil-related ecosystem services. This study aimed to assess the resilience and change in physiological status of the microbial community under extreme moisture stress conditions using novel metabolic profiling approaches, namely complex lipids and untargeted primary metabolites. In addition, we used phospholipid fatty acid (PLFA) profiling to identify changes in microbial community structure. Soil samples were collected during a natural, extreme drought event and post-drought from replicated grassland split plots, planted with either deep-rooting Festulolium (cv. AberNiche) or Lolium perenne L. (cv. AberEcho), receiving nitrogen (N) fertiliser loading rates at either 0 or 300 kg N ha−1 yr−1. These plots were split at the start of the drought period, and half of each subplot was irrigated with water throughout the drought period at a rate of 50 mm week−1 to alleviate moisture stress. PLFA analysis revealed a distinct shift in microbial community between drought and post-drought conditions, primarily driven by N loading and water deficit. Complex lipid analysis identified 239 compounds and untargeted analysis of primary metabolites identified 155 compounds. Both soil complex lipids and primary metabolites showed significant changes under drought conditions. Additionally, the irrigated ‘reference’ plots had a significantly higher cumulative greenhouse gas (CO2 and N2O) flux over the period of sampling. Recovery of the microbial lipidome and metabolome to reference plot levels post-drought was rapid (within days). Considerable changes in soil primary metabolomic and lipidomic concentrations shown in this study demonstrate that while soil metabolism was strongly affected by moisture stress, the system (plant and soil) was highly resilient to an intense drought.

Wood represents the single most important source of renewable energy worldwide and depending on the mechanism of energy production can lead to the production of by-products with vastly different properties (i.e. wood ash (WA) from incineration and biochar (BC) from pyrolysis). These are typically applied to land, however, a critical comparison of their impact on soil quality and carbon (C) cycling is lacking. To address this, we generated biochar (450 °C) and wood ash (870 °C) from the same mixed hardwood feedstock and added it to an agricultural grassland at comparable rates under both laboratory and field conditions (10 t ha −1 and 571 kg ha −1 for BC and WA, respectively). We hypothesized that alkaline, nutrient-rich wood ash would stimulate microbial activity, resulting in the loss of soil organic matter (SOM), while biochar which is recalcitrant to microbial attack would promote the stabilization of native SOM. The effects on the soil microbial community and soil C and N cycling were determined over 1 year. Overall, biochar promoted soil quality by enhancing nutrient availability (P and K), moisture retention and increasing soil C content. However, it was also associated with an increase in below-ground CO 2 loss. As plant productivity was unaffected and laboratory incubations of biochar with 14 C-labelled SOM showed no indication of priming, we deduce that this CO 2 originates from the biochar itself. This is supported by the lack of effect of biochar on soil N cycling, microbial biomass and community structure. Wood ash had almost no effect on either soil quality or vegetation quality (yield and foliar nutrient content) under field conditions but did induce negative SOM priming under both laboratory and field conditions. We conclude that when applied at field-relevant rates, neither amendment had a detrimental effect on native SOM cycling. While wood ash promotes the retention of native SOM, biochar may be a better strategy for enhancing SOM levels because of its intrinsic recalcitrant character, however, this needs to be offset against the reduced amount of energy derived from pyrolysis in comparison to incineration.

Extreme flood events are predicted to have a negative impact on soil quality. Currently, there is a lack of information about the effect of agricultural practices on soil functioning and microbial processes under these events. We hypothesized that the impact of flooding on soil quality will be exacerbated when crop residues are present in the soil as they will induce more extreme anaerobicity. A spring extreme flood event (10 °C, 9 weeks) was simulated in mesocosms containing an arable sandy-loam soil low in nutrients. The main treatments were (1) with and without flooding and (2) with and without maize residue addition (8 Mg ha−1). We monitored changes in soil chemical quality indicators (e.g. pH, salinity, Fe3+, P, C, NH4 +, NO3 − and organic N), greenhouse gas (GHG) emissions (CO2, CH4, N2O) and soil microbial community composition (PLFAs) during a prolonged flood period (9 weeks) and an 8-week “recovery” period after flooding. In comparison to the other treatments, flooding in the presence of crop residues resulted in a dramatic drop in soil redox potential. This was associated with the enhanced release of Fe and C into solution and an increase in CH4 emissions. In contrast, maize residues reduced potential nitrate losses and N2O emissions, possibly due to complete denitrification and microbial N immobilization. Both flooding and maize residues stimulated microbial growth and promoted a shift in microbial community composition. Following floodwater removal, most of the soil quality indicators returned to the levels of the control treatment within 5 weeks. After this short recovery phase, no major impact of flooding could be observed on plant growth (maize pot-grown). Overall, we conclude that both extreme flooding and management regime negatively impact upon a range of soil quality indicators (e.g. redox, GHG emissions); however, the soil showed high resilience and recovered quickly after floodwater removal. Further work is required to investigate the impact of repeated extreme flood events on soil quality and function over longer timescales. Electronic supplementary material The online version of this article (doi:10.1007/s00374-017-1214-0) contains supplementary material, which is available to authorized users.

Gaseous emissions from animal manure are considerable contributor to global ammonia (NH3) and agriculture greenhouse gas (GHG) emissions. Given the demand to promote mitigation of GHGs while fostering sustainable development of the Paris Agreement, an improvement of management systems is urgently needed to help mitigate climate change and to improve atmospheric air quality. This study presents a meta-analysis and an integrated assessment of gaseous emissions and mitigation potentials for NH3, methane (CH4), and nitrous oxide (N2O) (direct and indirect) losses from four typical swine manure management systems (MMSs). The resultant emission factors and mitigation efficiencies allow GHG and NH3 emissions to be estimated, as well as mitigation potentials for different stages of swine operation. In particular, changing swine manure management from liquid systems to solid-liquid separation systems, coupled with mitigation measures, could simultaneously reduce GHG emissions by 65% and NH3 emissions by 78%. The resultant potential reduction in GHG emissions from China's pig production alone is greater than the entire GHG emissions from agricultural sector of France, Australia, or Germany, while the reduction in NH3 emissions is equivalent to 40% of the total NH3 emissions from the European Union. Thus, improved swine manure management could have a significant impact on global environment issues.

The largest livestock production and greatest fertilizer use in the world occurs in China. However, quantification of the nutrient flows through the manure management chain and their interactions with management-related measures is lacking. Herein, we present a detailed analysis of the nutrient flows and losses in the “feed intake−excretion−housing−storage−treatment−application” manure chain, while considering differences among livestock production systems. We estimated the environmental loss from the manure chain in 2010 to be up to 78% of the excreted nitrogen and over 50% of the excreted phosphorus and potassium. The greatest losses occurred from housing and storage stages through NH 3 emissions (39% of total nitrogen losses) and direct discharge of manure into water bodies or landfill (30−73% of total nutrient losses). There are large differences among animal production systems, where the landless system has the lowest manure recycling. Scenario analyses for the year 2020 suggest that significant reductions of fertilizer use (27−100%) and nutrient losses (27−56%) can be achieved through a combination of prohibiting manure discharge, improving manure collection and storages infrastructures, and improving manure application to cropland. We recommend that current policies and subsidies targeted at the fertilizer industry should shift to reduce the costs of manure storage, transport, and application.

Industrialised agriculture is heavily reliant upon synthetic nitrogen fertilisers and imported protein feeds, posing environmental and food security challenges. Increasing the cultivation of leguminous crops that biologically fix nitrogen and provide high protein feed and food could help to address these challenges. We report on the innovative use of an important leguminous crop, pea (Pisum sativum L.), as a source of starch for alcohol (gin) production, yielding protein-rich animal feed as a co-product. We undertook life cycle assessment (LCA) to compare the environmental footprint of 1 L of packaged gin produced from either 1.43 kg of wheat grain or 2.42 kg of peas via fermentation and distillation into neutral spirit. Allocated environmental footprints for pea-gin were smaller than for wheat-gin across 12 of 14 environmental impact categories considered. Global warming, resource depletion, human toxicity, acidification and terrestrial eutrophication footprints were, respectively, 12%, 15%, 15%, 48% and 68% smaller, but direct land occupation was 112% greater, for pea-gin versus wheat-gin. Expansion of LCA boundaries indicated that co-products arising from the production of 1 L of wheat- or pea-gin could substitute up to 0.33 or 0.66 kg soybean animal feed, respectively, mitigating considerable greenhouse gas emissions associated with land clearing, cultivation, processing and transport of such feed. For pea-gin, this mitigation effect exceeds emissions from gin production and packaging, so that each L of bottled pea gin avoids 2.2 kg CO2 eq. There is great potential to scale the use of legume starches in production of alcoholic beverages and biofuels, reducing dependence on Latin American soybean associated with deforestation and offering considerable global mitigation potential in terms of climate change and nutrient leakage — estimated at circa 439 Tg CO2 eq. and 8.45 Tg N eq. annually. Keywords: Pea, Legumes, Life cycle assessment, LCA, Animal feed, DDGS, Distillation, Ethanol

Grasslands cover more than 70% of the world's agricultural land playing a pivotal role in global food security, economy, and ecology due to their flexibility and functionality. Climate change, characterized by changes in temperature and precipitation patterns, and by increased levels of greenhouse gases in the atmosphere, is anticipated to increase both the frequency and severity of extreme weather events, such as drought, heat waves, and flooding. Potentially, climate change could severely compromise future forage crop production and should be considered a direct threat to food security. This review aimed to summarize our current understanding of the physiological and metabolic responses of temperate grasses to those abiotic stresses associated with climate change. Primarily, substantial decreases in photosynthetic rates of cool‐season grasses occur as a result of high temperatures, water‐deficit or water‐excess, and elevated ozone, but not CO2 concentrations. Those decreases are usually attributed to stomatal and non‐stomatal limitations. Additionally, while membrane instability and reactive oxygen species production was a common feature of the abiotic stress response, total antioxidant capacity showed a stress‐specific response. Furthermore, climate change‐related stresses altered carbohydrate partitioning, with implications for biomass production. While water‐deficit stress, increased CO2, and ozone concentrations resulted in higher carbohydrate content, the opposite occurred under conditions of heat stress and flooding. The extent of damage is greatly dependent on location, as well as the type and intensity of stress. Fortunately, temperate forage grass species are highly heterogeneous. Consequently, through intra‐ and in particular inter‐specific plant hybridization (e.g., Festuca x Lolium hybrids) new opportunities are available to harness, within single genotypes, gene combinations capable of combating climate change.

In 2015, the Chinese government banned livestock production in some regions (called non-livestock production regions, NLPRs) to control surface water pollution near vulnerable water bodies. In total, 90,000 NLPRs had been established by 2017, covering a land area of 0.82 million km2 and shutting down 0.26 million pig farms1. As a consequence, the number of slaughtered pigs decreased by 46 million head yr–1 between 2014 and 2017. The NLPRs policy is globally unprecedented in terms of the geographical area and number of farms affected, as well as its implementation speed. The NLPRs policy has reduced pork self-sufficiency in some provinces by up to 40% (ref. 2). However, it is unclear which farms and regions may take over the market share.

Composting of solid waste can be associated with a loss of the agronomic value (nutrient loss), as well as a source of environmental impact through the emission of the greenhouse gases (GHG) nitrous oxide (N2O) and methane (CH4) and volatilization of ammonia (NH3). Additives have been considered as a useful option to mitigate these environmental emissions, but the wider effects of using different additives on multiple gas emissions is still uncertain. Here, a global meta-analysis was conducted using 105 studies with 303 paired comparisons, to quantify the impact of different additives on NH3 and GHG emissions, considering different composting feedstock properties. On average, additives reduced the total nitrogen (TN) loss (46.4%), NH3 (44.5%), N2O (44.6%) and CH4 (68.5%) emissions, and total GHG emissions expressed as global warming potential (GWP) (54.2%) during composting. Chemical, physical and microbial additives all significantly reduced TN loss and NH3 emission; however, the strongest effect was observed for chemical additives under the condition of low moisture content (≤65%), low C/N ratios (≤20) or alkalinity (pH > 7.5). Specifically, PO4 3− and Mg2+ salt had the greatest mean mitigation for TN loss (68.0%) and NH3 emission (62.0%). In contrast, physical additives (e.g. biochar and zeolite) were more effective at reducing the total GHG emissions (67.2%) compared with chemical additives because of the greater mitigation of N2O emission. Low moisture content (≤65%) or low C/N ratios (≤20) enhanced the effectiveness of chemical additives in reducing TN loss and NH3 emission. Physical additives were suggested to be more effective in reducing N2O emission at low moisture content (≤65%) or high C/N ratios (>20 to ≤ 30). The magnitude of the mitigation of TN loss and NH3 emission increased as the dosage rate of PO4 3− and Mg2+ salt/superphosphate increased between 0 and 20%. This meta-analysis suggests that an optimized combination of chemical and physical additives tailored to feedstock characteristics and application dosage may be a promising approach for the synergistic mitigation of NH3 and GHG emissions.

Typically, half of the nitrogen (N) fertiliser applied to agricultural fields is lost to the wider environment. This inefficiency is driven by soil processes such as denitrification, volatilisation, surface run-off and leaching. Rainfall plays an important role in regulating these processes, ultimately governing when and where N fertiliser moves in soil and its susceptibility to gaseous loss. The interaction between rainfall, plant N uptake and N losses, however, remains poorly understood. In this study we use numerical modelling to predict the optimal N fertilisation strategy with respect to rainfall patterns and offer mechanistic explanations to the resultant differences in optimal times of fertiliser application. We developed a modelling framework that describes water and N transport in soil over a growing season and assesses nitrogen use efficiency (NUE) of split fertilisations within the context of different rainfall patterns. We used ninety rainfall patterns to determine their impact on optimal N fertilisation times. We considered the effects of root growth, root N uptake, microbial transformation of N and the effect of soil water saturation and flow on N movement in the soil profile. On average, we show that weather-optimised fertilisation strategies could improve crop N uptake by 20% compared to the mean uptake. In drier years, weather-optimising N applications improved the efficiency of crop N recovery by 35%. Further analysis shows that maximum plant N uptake is greatest under drier conditions due to reduced leaching, but it is harder to find the maximum due to low N mobility. The model could capture contrasting trends in NUE seen in previous arable cropping field trials. Furthermore, the model predicted that the variability in NUE seen in the field could be associated with precipitation-driven differences in N leaching and mobility. In conclusion, our results show that NUE in cropping systems could be significantly enhanced by synchronising fertiliser timings with both crop N demand and local weather patterns.

The use of livestock manure as an organic fertiliser on agricultural land is an attractive alternative to synthetic fertiliser. The type of manure and the timing and method of application can however be crucial factors in reducing the extent of nitrogen lost from the system. This is important not only to enhance crop production, but in controlling gaseous emissions, including nitrous oxide (N2O) and ammonia (NH3). Emissions of N2O and NH3 were measured for 12 months from two experiments at an arable site in Scotland, to determine the effect of manure type and the timing (season) of application. Emission factors (EFs) were calculated for each manure applied in each season, and compared to IPCC standard EFs of 1% for N2O and 20% for NH3. Cattle farmyard manure, broiler litter, layer manure, and cattle slurry by surface broadcast and trailing hose application were applied to one experiment in October 2012 (autumn applications) and one in April 2013 (spring applications). Experimental areas were sown with winter wheat (Triticum aestivum) and manures were applied at typical rates. Crop yield was recorded to allow calculation of N2O and NH3 emission intensities. Mean annual N2O emissions across all manure treatments were greater from autumn (2 kg N2O–N ha− 1) than spring (0.35 kg N2O–N ha− 1) applications, and in the spring experiment were significantly lower from cattle slurry than other treatments. Ammonia emissions were generally greater (though not significantly) from spring than autumn applications. Significantly greater NH3 emissions were measured from layer manure than all other manures at both times of application. N2O and NH3 EFs were highly variable depending on the season of application and manure type. The mean autumn and spring N2O EFs across all manure treatments were 1.72% and − 0.33% respectively, and mean NH3 EFs across all treatments were 8.2% and 15.0% from autumn and spring applications, respectively. These results demonstrate large deviation from the IPCC default values for N2O and NH3 EFs, and the considerable effect that manure type and time of application have on N2O and NH3 emissions.

SUMMARYIncreasing recognition of the extent to which nitrous oxide (N2O) contributes to climate change has resulted in greater demand to improve quantification of N2O emissions, identify emission sources and suggest mitigation options. Agriculture is by far the largest source and grasslands, occupying c. 0·22 of European agricultural land, are a major land-use within this sector. The application of mineral fertilizers to optimize pasture yields is a major source of N2O and with increasing pressure to increase agricultural productivity, options to quantify and reduce emissions whilst maintaining sufficient grassland for a given intensity of production are required. Identification of the source and extent of emissions will help to improve reporting in national inventories, with the most common approach using the IPCC emission factor (EF) default, where 0·01 of added nitrogen fertilizer is assumed to be emitted directly as N2O. The current experiment aimed to establish the suitability of applying this EF to fertilized Scottish grasslands and to identify variation in the EF depending on the application rate of ammonium nitrate (AN). Mitigation options to reduce N2O emissions were also investigated, including the use of urea fertilizer in place of AN, addition of a nitrification inhibitor dicyandiamide (DCD) and application of AN in smaller, more frequent doses. Nitrous oxide emissions were measured from a cut grassland in south-west Scotland from March 2011 to March 2012. Grass yield was also measured to establish the impact of mitigation options on grass production, along with soil and environmental variables to improve understanding of the controls on N2O emissions. A monotonic increase in annual cumulative N2O emissions was observed with increasing AN application rate. Emission factors ranging from 1·06–1·34% were measured for AN application rates between 80 and 320 kg N/ha, with a mean of 1·19%. A lack of any significant difference between these EFs indicates that use of a uniform EF is suitable over these application rates. The mean EF of 1·19% exceeds the IPCC default 1%, suggesting that use of the default value may underestimate emissions of AN-fertilizer-induced N2O loss from Scottish grasslands. The increase in emissions beyond an application rate of 320 kg N/ha produced an EF of 1·74%, significantly different to that from lower application rates and much greater than the 1% default. An EF of 0·89% for urea fertilizer and 0·59% for urea with DCD suggests that N2O quantification using the IPCC default EF will overestimate emissions for grasslands where these fertilizers are applied. Large rainfall shortly after fertilizer application appears to be the main trigger for N2O emissions, thus applicability of the 1% EF could vary and depend on the weather conditions at the time of fertilizer application.

Cultivated agricultural soils are the largest anthropogenic source of nitrous oxide (N2O), a greenhouse gas approx. 298 times stronger than carbon dioxide. As agricultural land covers 40–50% of the earth’s surface agricultural N2O emissions could significantly influence future climate. The timing, amount and form of manufactured nitrogen (N) fertiliser applied to soils are major controls on N2O emission magnitude, and various methods are being investigated to quantify and reduce these emissions. A lack of measured N2O emission factors (EFs) means that most countries report N2O emissions using the IPCC’s Tier 1 methodology, where an EF of 1% is applied to mineral soils, regardless of soil type, climate, or location. The aim of this research was to generate evidence from experiments to contribute to improving the UK’s N2O agricultural inventory, by determining whether N2O EFs should vary across soil types and agroclimatic zones. Mitigation methods were also investigated, including assessing the impact of the nitrification inhibitor (NI) dicyandiamide (DCD), the application of more frequent smaller doses of fertiliser, and the impact of different rates and forms of manufactured N fertiliser. Nitrous oxide emissions were measured at one cropland site in Scotland and two in England for 12 months in 2011/2012, along with soil and environmental variables. Crop yield was also measured, and emission intensities were calculated for the contrasting fertiliser treatments. The greatest mean annual cumulative emissions from a range of ammonium nitrate (AN) fertiliser rates were measured at the Scottish site (2301 g N2O-N ha−1), which experienced 822 mm rainfall compared to 418 mm and 472 mm at the English sites, where cumulative annual emissions were lower (929 and 1152 g N2O-N ha−1, respectively). Climate and soil mineral N influenced N2O emissions, with a combination of factors required to occur simultaneously to generate the greatest fluxes. Emissions were related to fertiliser N rate; however the trend was not linear. EFs for AN treatments varied between sites, but at both English sites were much lower than the 1% value used by the IPCC, and as low as 0.20%. DCD reduced AN- and urea-generated N2O emissions and yield-scaled emissions at all sites. AN application in more frequent smaller doses reduced emissions at all sites, however, the type of fertiliser (AN or urea) had no impact. A significant difference in mean annual cumulative emissions between sites reflected differences in rainfall, and suggests that location specific or rainfall driven emission estimates could be considered.

China has significantly increased its production and per capita consumption of animal-derived food. However, many livestock farms in China are industrialized and landless, and have poor animal manure management. As a result, losses of nutrients to the environment are large. These losses can cause severe pollution of (i) air, via ammonia (NH3) emissions that contribute to smog and (ii) water, via direct discharge of manure to watercourses and leaching of nitrate (NO3–), causing eutrophication and increasing nitrate accumulation in drinking water.

Soil phosphorus (P) improvement is one of the important aims of vegetation restoration. However, the effects of different vegetation restoration types on soil P cycling and the underlying mechanisms remain unclear. Together with vegetation structure and soil properties, we measured the soil P fractions and P transformation rates to evaluate the characteristics of ecologically relevant soil P fraction distributions and their dynamics for the most common vegetation restoration types in a subtropical mountain ecosystem (i.e., PF, Pinus forest; EF, Eucalyptus forest; SL, shrubland; and NSF, natural secondary forest). We found that water-extractable inorganic P (Pi), organic P (Po), and acid phosphatase activity (APA) were significantly higher in NSF than those in the other vegetation types (P

Fen peatlands represent a globally important carbon (C) store, while also providing highly productive agricultural land. Drainage of these organic soils is required to create conditions suitable for crop growth, but this results in substantial greenhouse gas (GHG) emissions. One potential GHG mitigation option is to raise the groundwater table to reduce the duration and volume of peat exposure to aerobic conditions. However, the trade-off between maintaining food production and securing ecosystem function under a high water table (WT) presents a serious challenge for both land managers and policy makers. Therefore, we conducted a controlled mesocosm experiment to investigate the effects of WT elevation (from −50 cm to −30 cm) under three contrasting scenarios: (i) WT raised throughout the year, (ii) WT raised in the winter only, and (iii) WT raised in the growing season only. We measured GHG emissions, nitrate, ammonium and dissolved organic C concentrations in soil solution, alongside the yield of a commercially important crop (lettuce). Raising the WT throughout the year reduced lettuce yields by 37% and reduced CO2 emissions by 36% without changing the loss rates of N2O or CH4. Raising the WT only in the winter did not significantly reduce crop yield, but still suppressed CO2 emissions during the fallow period (by 30%). Raising the WT only in the growing season reduced root growth and CO2 emissions (by 27%), but had no major effect on lettuce yield. In conclusion, the present study shows that raising the groundwater table in the non-growing season reduced GHG emissions without negatively affecting lettuce yields, and may therefore represent a viable GHG mitigation option for agricultural peatlands.

Drainage and cultivation have turned peatlands from carbon (C) sinks into hotspots for greenhouse gas (GHG) emissions. Raising the water table and planting of winter cover crops are potential strategies to help reduce peat oxidation and re-initiate net C accumulation during the non-cropping period. However, the effects of these practices as well as their interactions on GHG emissions remain unclear. Here, we carried out an outdoor mesocosm experiment to elucidate the effect of water table levels (−30 cm and −50 cm) and winter cover crop cultivation (vetch, rye, no plant) on carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes during the winter period (November-April). Soil-atmosphere GHG exchange, GHG concentrations within the peat profile and soil water solute concentrations were monitored. Our results showed that high water table significantly reduced ecosystem respiration, while it had no net effect on N2O and CH4 fluxes. Uptake of available N by the cover crop significantly reduced nitrate in soil solution, thereby lowering the potential for leaching and both direct and indirect N2O emissions. No interactive effects between water table levels and cover crops were detected for any of the measured GHG fluxes. Seasonal variations of GHG fluxes were positively correlated with soil air concentrations at −15 cm and −40 cm depths, which were further regulated by dissolved organic C, nitrate concentration, and anaerobic conditions in the soil. This study suggests that there is great potential to raise water table levels and introduce green cover crops to reduce GHG emissions. Further studies are needed to achieve a complete evaluation of these strategies outside of the growing season, which may provide a significant mitigation benefit in C-rich cultivated peatlands.

Soils support a wide range of ecosystem services that underpin Earth system functioning. It is therefore essential that we have robust approaches to evaluate how anthropogenic perturbation affects soil quality and the delivery of these services. Metabolomics, the large-scale study of low molecular weight organic compounds in soil, offers one potential approach to characterise soils and evaluate the metabolic status of the soil biological community. The aims of the present study were to 1) characterise the soil metabolome across a contrasting range of soil types, 2) understand the relationships between common chemical and physical soil quality indicators and its metabolome, and 3) evaluate the discriminatory power of soil metabolomics and its potential use as a soil quality indicator. Nine different topsoils with 5 replications were collected along an altitudinal primary productivity gradient encompassing a wide range of soil types and land uses. Metabolites were extracted from soil using 3:3:2 (v/v/v) acetonitrile:isopropanol:water and individual compounds identified using a gas chromatography-mass spectrometry (GC-MS) platform. Overall, 405 individual compounds were detected, of which 146 were positively identified, including sugars, amino acids, organic acids, nucleobases, sugar alcohols, lipids and a range of secondary metabolites. The concentration and profile of metabolites was found to vary greatly between the soil types. Further, the soils’ metabolomic fingerprints correlated to a number of environmental factors, including pH, land-use, moisture and salinity. We also tentatively attributed soil-specific metabolites to potential functional pathways, although complementary proteomic, genomic and transcriptomic approaches would be needed to provide definitive supporting evidence. In conclusion, soil metabolomics offers the potential to reveal the complex molecular networks and metabolic pathways operating in the soil microbial community and a means of evaluating soil function. Further work is now required to benchmark soil metabolomes under a wide range of management regimes so that they can be used for the quantitative assessment of soil quality.

The addition of cattle slurry to agricultural land is a widespread practise, but if not correctly managed it can pose a contamination risk to aquatic ecosystems. The transport of inorganic and organic components of cattle slurry to watercourses is a major concern, yet little is known about the physical transport mechanisms and associated fluxes and timings of contamination threats. Therefore, the aim of the study was to ascertain the importance of flow pathway partitioning in the transport (fluxes and timing) of dissolved and particulate slurry-derived compounds with implications for off-site contamination. A series of rainfall–runoff and erosion experiments were carried out using the TRACE (Test Rig for Advancing Connectivity Experiments) experimental hillslope facility. The experiments allowed the quantification of the impact of changing slope gradient and rainfall intensity on nutrient transport from cattle slurry applied to the hillslope, via surface, subsurface, and vertical percolated flow pathways, as well as particulate transport from erosion. The dissolved components were traced using a combination of ammonium (NH4+) and fluorescence analysis, while the particulate fraction was traced using organic biomarkers, 5β-stanols. Results showed that rainfall events which produced flashy hydrological responses, resulting in large quantities of surface runoff, were likely to move sediment and also flush dissolved components of slurry-derived material from the slope, increasing the contamination risk. Rainfall events which produced slower hydrological responses were dominated by vertical percolated flows removing less sediment-associated material, but produced leachate which could contaminate deeper soil layers, and potentially groundwater, over a more prolonged period. Overall, this research provides new insights into the partitioning of slurry-derived material when applied to an unvegetated slope and the transport mechanisms by which contamination risks are created.

The hydrological transport of low-molecular weight organic nitrogen (LMWON) compounds has received little attention in the literature, particularly relative to inorganic nitrogen (N), with less attention given to the decoupling of the carbon (C) and N cycles following rainfall events. We determined the impacts of the soil biota on the transport of N compounds in a loam soil, using 15N and 13C to trace the vertical transport of 15N13C-urea, 15N13C-amino acids, 15NO3, and 15NH4 through the soil profile, following simulated rainfall events. This research has demonstrated that biotic assimilation leads to rapid decoupling of the C and N cycles during leaching, with C transport limited to the soil surface (< 2 cm), whereas N which was stored within the soil profile during a single rainfall event could be remobilised and leached (a further 2–6 cm) following an additional rainfall event.

Livestock emissions account for 74% of nitrous oxide contributions to greenhouse gases in the UK. However, it remains uncertain how much is directly attributable to localised sheep urination events, which could generate nitrous oxide emission ‘hot spots’. Currently, IPCC emission factors are mainly extrapolated from lowland grazing systems and do not incorporate temporal or spatial factors related to sheep behaviour and movement. Being able to gather data that reliably measures when, where, and how much sheep urinate is necessary for accurate calculations and, to inform best management practices for reducing greenhouse gas emissions and minimizing emission-based climate change. Animal-attached movement sensors have been shown to be effective in classifying different behaviours, albeit with varying classification accuracy depending on behaviour types. Previous studies have used accelerometers on cattle and sheep to assess active and non-active behaviours to help with grazing management, although no study has yet attempted to identify sheep urination events using this method. We attached tri-axial accelerometer sensor tags to thirty Welsh Mountain ewes for thirty days to assess if we could identify urination events. We used random forest models using different sliding mean windows to classify behaviours. Urination had a distinctive pattern and could be identified from accelerometer data, with a 5 s window providing the best recall and a 10 s window giving the best precision. ‘State’ behaviours considered (foraging, walking, running, standing and lying down) were also identified with high recall and precision. This demonstrates the extent to which the identification of discrete ‘event’ behaviours may be sensitive to the window size used to calculate the summary statistics. The method shows promise for identifying urination in sheep and other livestock, being minimally invasive compared to other methods, and has clear potential to inform agricultural management practices and policies.