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Drying and rewetting cycles are known to be important for the dynamics of carbon (C), phosphorus (P), and nitrogen (N) in soils. This study reports the short‐term responses of these nutrients to consecutive drying and rewetting cycles and how varying soil moisture content affects microbial biomass C and P (MBC and MBP), as well as associated carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The soil was incubated for 14 d during which two successive drying–rewetting episodes were imposed on the soils. Soils subjected to drying (DRW) were rewetted on the seventh day of each drying period to return them to 60% water holding capacity, whilst continually moist samples (M), with soil maintained at 60% water holding capacity, were used as control samples. During the first seven days, the DRW samples showed significant increases in extractable ammonium, total oxidized nitrogen, and bicarbonate extractable P concentrations. Rewetting after the first drying event produced significant increases only in CO2 flux (55.4 µg C g−1 d−1). The MBC and MBP concentrations fluctuated throughout the incubation in both treatments and only the second drying–rewetting event resulted in a significantly MBC decrease (416.2 and 366.8 mg kg−1 in M and DRW soils, respectively). The two drying–rewetting events impacted the microbial biomass, but distinguishing the different impacts of microbial versus physical impacts of the perturbation is difficult. However, this study, having a combined approach (C, N, and P), indicates the importance of understanding how soils will react to changing patterns of drying–rewetting under future climate change. [ABSTRACT FROM AUTHOR]

According to the available guidelines, good practices for calculating nitrous oxide (N 2 O) emission factors (EFs) for livestock excreta and manure application include that sampling duration should be of at least one year after the nitrogen (N) application or deposition. However, the available experimental data suggest that in many cases most emissions are concentrated in the first months following N application. Therefore resources could be better deployed by measuring more intensively during a shorter period. This study aimed to assess the contribution of the N 2 O flux in the period directly after N application to the annual net emission. We used a database of 100 year-long plot experiments from different excreted-N sources (dung, urine, farmyard manure and slurry) used to derive EFs for the UK and Ireland. We explored different shorter potential measurement periods that could be used as proxies for cumulative annual emissions. The analysis showed that the majority of emissions occur in the first months after application, especially in experiments that i) had urine as the N source, ii) had spring N application, iii) were conducted on fine-textured soils, or iv) showed high annual emissions magnitude. Experiments that showed a smaller percentage of emissions in the first months also had a low magnitude of annual net emissions (below 370 gN 2 O–N ha−1 year−1), so the impact of measuring during a shorter period would not greatly influence the calculated EF. Accurate EF estimations were obtained by measuring for at least 60 days for urine (underestimation: 7.1%), 120 days for dung and slurry (4.7 and 5.1%) and 180 days for FYM (1.4%). At least in temperate climates, these results are promising in terms of being able to estimate annual N 2 O fluxes accurately by collecting data for less than 12 months, with significant resource-saving when conducting experiments towards developing country-specific EFs. • Sampling period to calculate country-specific N 2 O emission factors was revised. • We analyzed data from 100 year-long IPCC compliant manure and excreta experiments. • A high proportion of annual emissions occurred in the months directly after N application. • Accurate EFs were measured at 60–180 days, with significant resource saving. [ABSTRACT FROM AUTHOR]

Unravelling the impacts of climate change on agriculture becomes increasingly important, as the rates and magnitude of its effects are accelerating. Current estimates of the consequences of climate change on nitrous oxide (N 2 O) emissions remain largely uncertain; there is a need for more consistent and comprehensive assessments of this impact. In this study we explored the implications of two IPCC climate change projections (high and medium emissions scenarios) on N 2 O emissions from South West England grasslands for the time slices of a baseline, the 2020s, the 2050s and the 2080s, employing a process-based model (SPACSYS). The model was initially calibrated and validated using datasets collected from three grassland sites of the region. Statistical analysis showed that simulated results had no significant total error or bias compared to measured values. We found a consistent increase in N 2 O emissions of up to 94% under future climate change scenarios compared to those under the baseline, and warming rather than precipitation variability was the overriding factor controlling the N 2 O rise. Modelling fertilizer forms showed that replacing ammonium-nitrate fertilizers with urea or slurry significantly reduced N 2 O emissions (c. 30%). Our study highlights the urgent necessity to adopt viable N 2 O mitigation measures now in order to avoid higher emissions in the future. [ABSTRACT FROM AUTHOR]

• Soil microbial community structure varied at different slope positions under maize cultivation. • Greater incorporation of old SOC (C3-C) by soil microorganisms in the bottom position of slope. • Use of maize-carbon is dominated by Gram positive bacteria and fungi. • Potential CO 2 and N 2 O emissions increased at bottom of ploughed slope. • Carbon sink potential of bottom slopes may be diminished by GHG emissions. Determining whether agricultural soils act as sinks or sources of greenhouse gases (GHGs) requires the quantification of variations in the pools and fluxes of soil organic carbon (SOC) and nutrients, e.g. nitrogen (N), as well as the associated soil microbial responses. In this study, soil was collected from experimental plots of maize (Zea mays) under conventional, minimum or strip tillage treatments established in a sloping field (~10%) of loamy soil in SW England, UK, where maize had been cultivated conventionally for 12 years. Topsoil (0–10 cm) cores were collected from the top, mid, bottom and foot slope positions to investigate soil C, N and microbial properties. The impact of conventional management on potential GHG emissions was assessed by incubating soils collected from the top, mid and bottom slope positions from the conventional treatment. Contents of SOC and total N were greatest at the top slope position and soil mineral N (NO 3 −-N and NH 4 +-N) concentrations were greater at the bottom and foot slope positions in all treatments. Biomarker phospholipid fatty acids (PLFA) for Gram positive bacteria and fungi were relatively 13C-enriched at each slope position regardless of treatment, indicating preferential utilization of organic matter from maize (C 4) rather than SOC (C 3). Around 70% of carbon incorporated into total PLFA was derived from C 3 -SOC at the slope foot, indicating that more SOC older than 12 years was being mineralized at the depositional position. Effluxes of N 2 O and CO 2 , and total GHG emission were greatest from the incubated soils sampled from the bottom slope position, suggesting that conditions in depositional positions of regularly ploughed sloping arable fields may have increased the potential for mineralization and denitrification. We conclude that the C sink potential of the depositional positions of slopes may be diminished by coincidental GHG emissions. [ABSTRACT FROM AUTHOR]

Abstract: Current research on macronutrient cycling in UK agricultural systems aims to optimise soil and nutrient management for improved agricultural production and minimise effects on the environment and provision of ecosystem services. Nutrient use inefficiencies can cause environmental pollution through the release of greenhouse gases into the atmosphere and of soluble and particulate forms of N, P and carbon (C) in leachate and run-off into watercourses. Improving nutrient use efficiencies in agriculture calls for the development of sustainable nutrient management strategies: more efficient use of mineral fertilisers, increased recovery and recycling of waste nutrients, and, better exploitation of the substantial inorganic and organic reserves of nutrients in the soil. Long-term field experimentation in the UK has provided key knowledge of the main nutrient transformations in agricultural soils. Emerging analytical technologies, especially stable isotope labelling, that better characterise macronutrient forms and bioavailability and improve the quantification of the complex relationships between the macronutrients in soils at the molecular scale, are augmenting this knowledge by revealing the underlying processes. The challenge for the future is to determine the relationships between the dynamics of N, P and C across scales, which will require both new modelling approaches and integrated approaches to macronutrient cycling. [Copyright &y& Elsevier]

Abstract: A detailed inventory framework was developed to estimate nitrous oxide (N2O) and methane (CH4) emissions from UK agriculture using the IPCC approach. The inventory framework model was illustrated by combining relevant emission factors with agricultural census data for England, Wales, Scotland and Northern Ireland for the year 2000 to derive country-specific emission estimates which were summed to derive the UK total. The framework enables simple assessment to be made of the impact on national emissions of using different emission factors (EFs) (e.g. site- or local-specific compared with IPCC default factors). The framework was used to calculate the average annual emissions of nitrous oxide (N2O) and methane (CH4) for specific livestock and crops, and amounts lost through volatilisation, leaching and runoff for each country in the UK. The framework provides a simple, realistic and transparent approach to estimating national emissions and can easily be updated. [Copyright &y& Elsevier]

Purpose: Summer catch crop (CC) has been introduced into the vegetable rotating system in greenhouse fields to reduce nitrogen (N) losses through crop uptake and residual N immobilization. However, the effects of planting sorghum with high N uptake and biomass, and biological nitrification inhibition (BNI) potential as a CC on soil N dynamics and subsequent crop yield remain unclear. Methods: In the two-year field experiment, the comprehensive effects of planting sorghum as CC on subsequent eggplant yield, soil mineral N dynamics, ammonia-oxidizing archaea (AOA) and bacteria (AOB) amoA gene abundances were determined, in comparison to the sweet corn and fallow treatments. Results: Compared to the fallow and sweet corn, planting sorghum as CC increased subsequent eggplant yield by 24.88% and 18.94% in the 2014–2015 and 2015–2016 over-winter growing season, respectively. CC planting reduced soil nitrate (NO3−-N) accumulation during the summer fallow season. Sorghum planting could significantly maintain higher level of ammonium (NH4+-N) concentration during the summer fallow season and the first month of succeeding over-winter season. In addition, sorghum planting reduced soil net nitrifying potential, which could be partially attributed to the decreased amoA gene abundance of AOA at the 0–30 and 30–60 cm soil layers and AOB at 0–30 cm soil layer. Conclusion: We conclude that planting sorghum in the summer fallow season is a promising strategy to retain soil NH4+-N, reduce soil NO3−-N accumulation, and enhance subsequent eggplant yield. [ABSTRACT FROM AUTHOR]

Within sustainable transportation systems, the adoption of electric vehicles (EVs) is considered as a potential solution to problems such as energy security, climate change, urban-air quality, and public health. This EV-adoption process is a complex system that considers the relationships between the dimensions of sustainability, car-ownership transition to EVs, market dynamics, and the government. Several models have been designed to address this system. However, these models have only partially developed these relationships because they did not consider all the components or relationships between the elements of this process. This article proposes a systemic approach based on previous models, which integrates all the components and relationships and incorporates the analysis of sustainability into the EV-adoption process. The system structure of this EV-adoption process is presented and discussed. This approach deepens the understanding of the synergies between market dynamics and sustainability, allowing to model the system more broadly. It can thus help in the sustainable and integrated evaluation of different policy scenarios, thereby contributing to a clearer understanding of the dynamic behavior and leverage points of the system. [ABSTRACT FROM AUTHOR]

This paper analyzes the production cycle of a Colombian flower producing company, focusing on the sowing and cutting processes. These processes are characterized by the presence of delays that imply large losses of money for the company. To facilitate the decision-making process and analyze alternatives to increase the company's profit, a discrete-event simulation model was built where three scenarios were evaluated: 1) a scenario of forced acceleration of flowering, 2) a scenario of sale of flowers that are considered waste, and 3) a scenario that combines the forced acceleration of flowering and eliminates a line of work. The results indicate that under a scenario of forced acceleration of flowering together with the elimination of a work line, greater profitability could be achieved for the company and counteract the economic losses caused by the delays present in the production process, due to the saving in human resources and at the same time achieving an increase in the production of flowers. [ABSTRACT FROM AUTHOR]

Solar-generated energy supply has been applied as a solution to address the increasing global population, global warming challenges, and the search for alternative sources of renewable and clean energy supply. Regions such as Latin America and the Caribbean have a significant rural population that lacks access to electricity, impeding their development, and increasing unemployment rates. This paper presents a system dynamics model (SD) for assessing the implementation of a solar energy supply chain (SESC), combining the analysis with the national industry's development for the manufacture of solar modules used in the implementation of solar farms and individual solution projects, especially in the non-interconnected zones of Colombia. This case study examines three scenarios in Colombia: national government-implemented solar farm projects; development of national supply chain implementation; and development of the solar energy market. These scenarios are evaluated using performance indicators for supply chain variables, including coverage, diversification, emissions, and job creation. The results indicate that implementing a supply chain and developing solar module production in Colombia can positively impact the proposed indicators, resulting in improvements of 5.9% in coverage, 6.3% in diversification, 6.7% in emission reductions, and 13% in job creation. • A novel model is developed for the solar energy supply chain. • The solar energy supply chain modeled prospectively and sustainably. • Analysis of energy, economic, environmental and social sustainability performance indicators. [ABSTRACT FROM AUTHOR]

Governments consider electric vehicle (EV) adoption as one of the strategies for reducing the negative impacts of the transport sector. However, the assessments that are usually conducted do not consider the impact that this transition may have on other aspects of the transport and energy sectors. This paper presents a system dynamics model to evaluate the effects that policies associated with EV adoption have on sustainability indicators, as well as on the vehicle and energy supply chains in Colombia. The main findings show that the proposed fiscal measures do not achieve massification in the medium term and that the capacity of the energy system may be a limiting factor in the adoption process. Systemic policy evaluation identifies problems that may emerge in their implementation, such as limiting factors and that policy efforts are not leverage points. It would, therefore, allow for better strategies to be formulated. [ABSTRACT FROM AUTHOR]

• RFR and XGB favourably fill gaps in challenging ecosystems. • RFR and XGB reproduced ecosystem responses well. • RFR and XGB overcame the effects of slow biomass changes on gap-filling. • Identifying the main environmental drivers were imperative to filling methane gaps. Eddy covariance serves as one the most effective techniques for long-term monitoring of ecosystem fluxes, however long-term data integrations rely on complete timeseries, meaning that any gaps due to missing data must be reliably filled. To date, many gap-filling approaches have been proposed and extensively evaluated for mature and/or less actively managed ecosystems. Random forest regression (RFR) has been shown to be stable and perform better in these systems than alternative approaches, particularly when filling longer gaps. However, the performance of RFR gap filling remains less certain in more challenging ecosystems, e.g., actively managed agri-ecosystems and following recent land-use change due to management disturbances, ecosystems with relatively low fluxes due to low signal to noise ratios, or for trace gases other than carbon dioxide (e.g., methane). In an extension to earlier work on gap filling global carbon dioxide, water, and energy fluxes, we assess the RFR approach for gap filling methane fluxes globally. We then investigate a range of gap-filling methodologies for carbon dioxide, water, energy, and methane fluxes in challenging ecosystems, including European managed pastures, Southeast Asian converted peatlands, and North American drylands. Our findings indicate that RFR is a competent alternative to existing research standard gap-filling algorithms. The marginal distribution sampling (MDS) is still suggested for filling short (< 12 days) gaps in carbon dioxide fluxes, but RFR is better for filling longer (> 30 days) gaps in carbon dioxide fluxes and also for gap filling other fluxes (e.g. sensible heat, latent energy and methane). In addition, using RFR with globally available reanalysis environmental drivers is effective when measured drivers are unavailable. Crucially, RFR was able to reliably fill cumulative fluxes for gaps > 3 moths and, unlike other common approaches, key environment-flux responses were preserved in the gap-filled data. [ABSTRACT FROM AUTHOR]

Urea present in cattle urine contributes large amounts of nitrogen (N) to grazed pastures, which can be the equivalent to approximately 1000 kg N ha−1. However, there are no studies in volcanic soils of southern Chile on the effect of different concentrations of urinary N deposited in the soil, nor of the effect different wetting and drying conditions mimicking the variation in weather conditions on the nitrification process from urea to NH4+ and total oxidized nitrogen (TON) over time. In addition, the inhibition of nitrification driven by the accumulation of NH3 at high rates of N applied to Andisol has not been evaluated. Fresh cattle urine was applied at three different rates of N equivalent to 247 kg N ha−1 (Low N), 461 kg N ha−1 (Medium N), and 921 kg N ha−1 (High N), as well as deionized water as a control. Further, three moisture conditions were imposed: constant moisture (CM), drying–rewetting (DRW) cycles at 7-day intervals, and soil drying (SD). Destructive soil core samples were evaluated for top and bottom halves individually every 7 days over a 36-day period to measure changes on inorganic N and pH. There were no interaction effects for N rates and soil moisture. The main effect of the different rates of N on mineralization was significant throughout the incubation period, while the effect of the different moisture conditions was variable over time. High N was associated with elevated NH3 concentrations and could explain why total N mineralization was partially inhibited. These results suggest that the presence of different nitrifying microorganisms in soil under different chemical and physical conditions determines nitrification, and thus, the oxidation of ammonia should be studied in more detail as the first step of nitrification, specifically in volcanic soils. [ABSTRACT FROM AUTHOR]

Purpose : Nitrogen (N) transfer from white clover (Trifolium repens cv.) to ryegrass (Lolium perenne cv.) has the potential to meet ryegrass N requirements. This study aimed to quantify N transfer in a mixed pasture and investigate the influence of the microbial community and land management on N transfer. Methods: Split root 15N-labelling of clover quantified N transfer to ryegrass via exudation, microbial assimilation, decomposition, defoliation and soil biota. Incorporation into the microbial protein pool was determined using compound-specific 15N-stable isotope probing approaches. Results: N transfer to ryegrass and soil microbial protein in the model system was relatively small, with one-third arising from root exudation. N transfer to ryegrass increased with no microbial competition but soil microbes also increased N transfer via shoot decomposition. Addition of mycorrhizal fungi did not alter N transfer, due to the source-sink nature of this pathway, whilst weevil grazing on roots decreased microbial N transfer. N transfer was bidirectional, and comparable on a short-term scale. Conclusions: N transfer was low in a model young pasture established from soil from a permanent grassland with long-term N fertilisation. Root exudation and decomposition were major N transfer pathways. N transfer was influenced by soil biota (weevils, mycorrhizae) and land management (e.g. grazing). Previous land management and the role of the microbial community in N transfer must be considered when determining the potential for N transfer to ryegrass. [ABSTRACT FROM AUTHOR]

Simple Summary: The livestock sector contributes a considerable proportion of greenhouse gas emissions. Mechanisms must be developed in this sector to reduce these gases' emissions. This generates a demand for studies that evaluate plant species or their extracts to define their potential in modulating ruminal fermentation with the objective of reducing enteric methane emissions. The yerba mate extract (YME) is obtained from a plant widely consumed in the southern region of Brazil for its biological properties, with few studies on rumen fermentation, meat quality, and production parameters. For this reason, this study sought to evaluate the inclusion of different levels of YME and analyze its effects on ruminal fermentability, methane emissions, and animal performance. Our results show that the inclusion of YME does not affect ruminal fermentation parameters or apparent digestibility. The inclusion of plant extracts that contain secondary compounds with the potential to modulate rumen fermentation and improve animal performance has gained attention in recent years. The aim of this study was to evaluate the effect of the inclusion of yerba mate extract (Ilex paraguariensis ST. Hilaire) (YME) on the ruminal parameters. Eight castrated cattle were divided into four groups, a control without YME (0%) and three treatment groups with 0.5, 1 and 2% inclusion of YME in the dry matter. The inclusion of YME did not show differences in ruminal methane emissions (CH4), and total apparent digestibility (p = 0.54). Likewise, YME did not modify ruminal pH, but positively affected NH3-N, which decreased linearly as the extract level in the diet increased (p = 0.01). No short chain fatty acids (SCFA) were influenced by YME, except isovaleric acid (p = 0.01), which showed a lower concentration in the inclusion of 2% YME. Our results show that up to 2% YME does not affect digestibility, ruminal fermentation parameters, or the concentration of short-chain fatty acids in the rumen. [ABSTRACT FROM AUTHOR]

This position paper summarizes the current understanding of biological nitrification inhibition (BNI) to identify research needs for accelerating the development of BNI as a N2O mitigation strategy for grazed livestock systems. We propose that the initial research focus should be on the systematic screening of agronomically desirable plants for their BNI potency and N2O reduction potential. This requires the development of in situ screening methods that can be combined with reliable N2O emission measurements and microbial and metabolomic analyses to confirm the selective inhibition of nitrification. As BNI-induced reductions in N2O emissions can occur by directly inhibiting nitrification, or via indirect effects on other N transformations, it is also important to measure gross N transformation rates to disentangle these direct and indirect effects. However, an equally important challenge will be to discern the apparent influence of soil N fertility status on the release of BNIs, particularly for more intensively managed grazing systems. [ABSTRACT FROM AUTHOR]

Electric vehicles (EV) are considered an option for reducing the transport sector's environmental impacts. Motivated by environmental concerns, governments are formulating policies for the promotion of EV. However, the EV transition has more than environmental benefits; it also has economic and social impacts that are usually not considered. Understanding the effects of the transition to EV on sustainability has become increasingly important in the appropriate public policies formulation and evaluation. This article presents a system dynamics model representing the Colombian EV market and the relationships between the market dynamics and sustainability. This model is used to understand the synergistic effects between the Colombian-market dynamics and sustainability system. The results show that the synergies between market dynamics and sustainability are important. Neglecting them would result in different behaviours from those exhibited in real life and overestimating performance measures. Therefore, the effects of policies that promote EVs would be inadequate if synergies are not considered. This approach is a first step towards improving the understanding of sustainable transport impacts from a holistic perspective and can formulate more robust policies. • System dynamics model broadens understanding of EV market and sustainability feedbacks • Synergistic and constant growth model of the system are compared • Analysis of extreme market scenarios to capture maximum impacts on sustainability • Synergies assessment between Colombian EV market dynamics and sustainability • Constant growth model fails to represent dynamics between sustainability and market [ABSTRACT FROM AUTHOR]

Background: Brachiaria humidicola (Bh) has the ability to produce biological nitrification inhibitors (NIs) and release NIs from the root to the soil. Aims: To compare the effects of growing Bh with Brachiaria ruziziensis (Br, which is not able to produce NIs) on soil nitrogen (N) dynamics, N gases and carbon dioxide (CO2) emissions and nitrifiers and denitrifiers following sheep urine application, a laboratory incubation was conducted in a He/O2 continuous flow denitrification system (DENIS). This incubation was conducted in the absence of light. Hence the measured effects of Bh and Br on N cycling were the residual effect of biological NIs released into the soil prior to the incubation and released via root death. Methods: The treatments were: (1) Bh with water application (Bh + W); (2) Bh with sheep urine (Bh + U); (3) Br with water application (Br + W); (4) Br with sheep urine (Br + U). Results: Results showed that soil NO3– concentration increased significantly in the soil with sheep urine application after the incubation. Soil nitrous oxide (N2O) and nitric oxide (NO) emissions increased immediately after the sheep urine application and peaked twice during the incubation. Cumulative emissions for the first peak were significantly lower from the Bh + U treatment (0.054 kg N ha–1) compared with the Br + U treatment (0.111 kg N ha–1), but no significant differences were observed in the total cumulative N2O and NO emissions between the Bh + U and Br + U treatment at the end of the incubation. Sheep urine addition did not affect the AOA, nirS and nosZ gene copies, but significantly increased the AOB gene copies after the incubation. Conclusions: We conclude that the residual effect of Bh to mitigate N2O emissions in a highly nitrifying soil is short‐lived. [ABSTRACT FROM AUTHOR]

Biological nitrification inhibition is a plant‐mediated rhizosphere process where natural nitrification inhibitors can be produced and released by roots to suppress nitrifier activity in soil. Nitrification is one of the critical soil processes in the nitrogen (N) cycle, but unrestricted and rapid nitrification in agricultural systems can result in major losses of N from the plant–soil system (i.e., by NO3− leaching and gaseous N emissions). In this study, we explored the potential efficacy of biological nitrification inhibitors (linoleic acid [LA] and linolenic acid [LN]) and a proven efficient synthetic (dicyandiamide [DCD]) nitrification inhibitor on N dynamics, nitrous oxide (N2O) and carbon dioxide (CO2) emissions in a highly nitrifying soil. 14C‐labelled LA, LN and DCD mineralization was determined in a parallel experiment to explore the fate of inhibitors after application. We found that LA and LN had no effect on soil NH4+ concentrations, but significantly decreased NO3− concentrations. Soil that received DCD had lower NO3− and higher NH4+ concentrations than the control (soil without nitrification inhibitors). LA and LN increased the cumulative N2O and CO2 emissions when they were applied at high concentrations (635 or 1,270 mg kg−1 dry soil). LA and LN had a much greater mineralization rate than that of DCD: 47–56%, 37–61% and 2.7–5.5%, respectively, after 38 days incubation. We conclude that in contrast to the direct inhibition of nitrification caused by DCD, addition of LA and LN may cause apparent nitrification inhibition by promoting microbial immobilization of soil NH4+ and/or NO3−. Future studies on nitrification inhibitors need to clearly differentiate between the direct and indirect effects that result from addition of these compounds to soil. Highlights: The efficacy and stability of nitrification inhibitors in a highly nitrifying soil were explored.This study supports efforts to mitigate N losses and improve nitrogen use efficiency of inputs.Addition of LA, LN and DCD can decrease NO3− concentration, but their modes of action may be different.The apparent effect of LA and LN on soil NO3− concentration could be indirect. [ABSTRACT FROM AUTHOR]

The application of organic materials to soil can recycle nutrients and increase organic matter in agricultural lands. Digestate can be used as a nutrient source for crop production but it has also been shown to stimulate greenhouse gas (GHG) emissions from amended soils. While edaphic factors, such as soil texture and pH, have been shown to be strong determinants of soil GHG fluxes, the impact of the legacy of previous management practices is less well understood. Here we aim to investigate the impact of such legacy effects and to contrast them against soil properties to identify the key determinants of soil GHG fluxes following digestate application. Soil from an already established field experiment was used to set up a pot experiment, to evaluate N2O, CH4 and CO2 fluxes from cattle‐slurry‐digestate amended soils. The soil had been treated with farmyard manure, green manure or synthetic N‐fertilizer, 18 months before the pot experiment was set up. Following homogenization and a preincubation stage, digestate was added at a concentration of 250 kg total N/ha eq. Soil GHG fluxes were then sampled over a 64 day period. The digestate stimulated emissions of the three GHGs compared to controls. The legacy of previous soil management was found to be a key determinant of CO2 and N2O flux while edaphic variables did not have a significant effect across the range of variables included in this experiment. Conversely, edaphic variables, in particular texture, were the main determinant of CH4 flux from soil following digestate application. Results demonstrate that edaphic factors and current soil management regime alone are not effective predictors of soil GHG flux response following digestate application. Knowledge of the site management in terms of organic amendments is required to make robust predictions of the likely soil GHG flux response following digestate application to soil. [ABSTRACT FROM AUTHOR]

This study argues that several metrics are necessary to build up a picture of yield gain and nitrogen losses for ryegrass sheep pastures. Metrics of resource use efficiency, nitrous oxide emission factor, leached and emitted nitrogen per unit product are used to encompass yield gain and losses relating to nitrogen. These metrics are calculated from field system simulations using the DAYCENT model, validated from field sensor measurements and observations relating to crop yield, fertilizer applied, ammonium in soil and nitrate in soil and water, nitrous oxide and soil moisture. Three ryegrass pastures with traditional management for sheep grazing and silage are studied. As expected, the metrics between long-term ryegrass swards in this study are not very dissimilar. Slight differences between simulations of different field systems likely result from varying soil bulk density, as revealed by a sensitivity analysis applied to DAYCENT. The field with the highest resource use efficiency was also the field with the lowest leached inorganic nitrogen per unit product, and vice versa. Field system simulation using climate projections indicates an increase in nitrogen loss to water and air, with a corresponding increase in biomass. If we simulate both nitrogen loss by leaching and by gaseous emission, we obtain a fuller picture. Under climate projections, the field with the lowest determined nitrous oxide emissions factor, had a relatively high leached nitrogen per product amongst the three fields. When management differences were investigated, the amount of nitrous oxide per unit biomass was found to be significantly higher for an annual management of grazing only, than a silage harvest plus grazing, likely relating to the increased period of livestock on pasture. This work emphasizes how several metrics validated by auto-sampled data provide a measure of nitrogen loss, efficiency and best management practise. Unlabelled Image • Provides yield-nitrogen metrics for ryegrass sheep pastures • Combination of climate, sensor and sampling data applied to agri-system modelling • Highest resource use efficiency coincides with lowest leaching per unit product. • N 2 O per unit biomass significantly lower for silage & grazing than grazing only. • Several related metrics reveal info about the system, hidden by using one metric. [ABSTRACT FROM AUTHOR]

In grassland systems, cattle and sheep urine patches are recognized as nitrous oxide (N2O) emission hot spots due to the high urinary nitrogen (N) concentrations. Hippuric acid (HA) is one of the constituents of ruminant urine that has been reported as a natural inhibitor of soil N2O emissions. The aim of this study was to examine the potential for elevated ruminant urine HA concentrations to reduce N2O emissions, in situ, on an acidic heavy clay soil under poorly drained conditions (WFPS > 85%). A randomized complete block design experiment with three replications and four treatments was conducted using the closed‐static‐flux chamber methodology. The four treatments were applied inside the chambers: control with no artificial urine application (C), control artificial urine (U), and enriched artificial urine with two rates of HA (55.8 and 90 mM, U+HA1, U+HA2). Soil inorganic‐N, soil dissolved organic carbon (DOC), soil pH as well as N2O and methane (CH4) fluxes were monitored over a 79‐d period. Although N2O emissions were not affected by the HA enriched urine treatments, U+HA2 positively affected the retention of N as NH4+ until day 3, when the soil pH dropped to values < 5. Subsequently, as a consequence of rainfall events and soil acidification, it is likely that leaching or sorption onto clay reduced the efficacy of HA, masking any treatment differential effect on N2O emissions. Moreover, CH4 fluxes as well as DOC results reflected the soil anaerobic conditions which did not favour nitrification processes. Further research is needed to determine the fate of HA into the soil which might clarify the lack of an in situ effect of this compound. [ABSTRACT FROM AUTHOR]

This chapter reviews contributions made to agricultural and environmental science and practice from research on temperate grassland carried out from 1982 to present at Rothamsted Research's North Wyke Research Station, Devon, UK. It describes the evolution of the research program and demonstrates the importance of sustained, interdisciplinary, and collaborative research. North Wyke has maintained a clear research focus, alongside an ability to adapt to changing grassland and environmental research needs and funding sources, and despite having changed affiliations on several occasions. The substantial contribution to agricultural and environmental science arising from the research station has influenced and continues to influence farm practice, research, and policy nationally and internationally. Some key topics have included nutrient cycling, farm waste management, gaseous emissions, biodiversity, grazing management, animal production (meat and milk), and forage quality. Currently, North Wyke Research Station is leading the way on taking increasingly holistic approaches to researching more efficient, sustainable approaches to grazing-livestock agricultural production. This involves the use of world-leading, facilities such as the North Wyke Farm Platform, comprising three farmlets, designed to test the productivity and environmental sustainability of contrasting temperate grassland beef and sheep systems. Future perspectives highlight key challenges facing the agricultural industry including climate change mitigation and adaptation, and the growing world population. Opportunities exist to tackle these challenges through technological advances, but also through increased integration of agricultural, environmental, economic and social research. North Wyke Research Station provides an example of a research facility where such challenges can be addressed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tillage versus no tillage and the use of DMPSA tested in rainfed semiarid barley. • DMPSA decreased 15N 2 O emissions during the preharvest period. • Remarkable postharvest N 2 O peak after rewetting derived from endogenous N. • No tillage and DMPSA increased crop recovery of exogenous and endogenous N, respectively. • No tillage reduced soil residual N, while DMPSA increased topsoil N retention. The sustainability of rainfed crops under semiarid conditions is threatened by low plant nitrogen (N) recovery as well as the potential loss of reactive N to the environment. A field 15N tracing experiment on barley (Hordeum vulgare L.) under rainfed conditions was carried out to study how different tillage management practices and the use of the nitrification inhibitor DMPSA affected the fate of N. The experiment consisted of a factorial combination of tillage (i.e., no tillage, NT, and conventional tillage, T) and fertilizer treatments (unfertilized control and ammonium nitrate, AN, with or without DMPSA). Single-labelled ammonium nitrate (15NH 4 NO 3 , 15AN, or NH 4 15NO 3 , A15N) was applied at top-dressing to microplots at a rate of 80 kg N ha−1. Our results show out that DMPSA modulates the nitrification process from both fertilizer-N and endogenous soil-N (which was the main contributor to plant N uptake and N 2 O emissions), affecting soil residual N at the end of the cropping period (i.e., higher topsoil retention of 15AN in DMPSA-amended plots). Generally, cumulative N 2 O emissions from fertilizer were derived from 15AN rather than from A15N, thus confirming the site-specific choice of the source of synthetic N as an effective N 2 O mitigation strategy. Two months after harvest, a rewetting event produced a remarkable N 2 O emission peak that drove total cumulative N 2 O emissions and was also mainly derived from endogenous N. These results suggest that dry seasons could decrease N 2 O losses after fertilization while causing critical peaks after rewetting, thus potentially limiting the effectiveness of mitigation strategies. The average plant N recovery from the synthetic fertilizer was 22.6%, while the use of DMPSA combined with NT enhanced plant N uptake from endogenous soil-N. This could be a result of the improved crop development and plant N acquisition under NT, consistent with the decrease of soil N retention for A15N in the deeper layer at the end of the experiment in the nontilled plots. This study contributes to the mechanistic understanding of the effect of nitrification inhibitors and tillage on N 2 O emissions, soil N dynamics and N plant recovery, revealing relevant effects of both management strategies and a critical role of endogenous soil-N under dry rainfed conditions. It can be concluded that, under the conditions of our study, combining DMPSA with NT could help to improve plant N recovery, thus resulting in positive impacts on reactive N loss and climate change mitigation and adaptation. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the ability of the SPACSYS model to simulate water run-off, soil moisture, N 2 O fluxes and grass growth using data generated from a field of the North Wyke Farm Platform. The field-scale model is adapted via a linked and grid-based approach (grid-to-grid) to account for not only temporal dynamics but also the within-field spatial variation in these key ecosystem indicators. Spatial variability in nutrient and water presence at the field-scale is a key source of uncertainty when quantifying nutrient cycling and water movement in an agricultural system. Results demonstrated that the new spatially distributed version of SPACSYS provided a worthy improvement in accuracy over the standard (single-point) version for biomass productivity. No difference in model prediction performance was observed for water run-off, reflecting the closed-system nature of this variable. Similarly, no difference in model prediction performance was found for N 2 O fluxes, but here the N 2 O predictions were noticeably poor in both cases. Further developmental work, informed by this study's findings, is proposed to improve model predictions for N 2 O. Soil moisture results with the spatially distributed version appeared promising but this promise could not be objectively verified. [ABSTRACT FROM AUTHOR]

Nitrification inhibitors, originally proposed for nitrate leaching mitigation, are recommended as effective nitrous oxide (N 2 O) mitigation strategies. Several compounds have been trialled and used in the past including dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP). Yet, little is known about the new nitrification inhibitor 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA). A field experiment using 15 N single-labelled ammonium nitrate ( 15 NH 4 NO 3 or NH 4 15 NO 3 ) was conducted to understand the effectiveness of DMPSA on a biochemical basis in an irrigated maize ( Zea mays L.) crop. Gaseous fluxes, i.e. N 2 O, 15 N 2 O, 15 N 2 , methane (CH 4 ), and carbon dioxide (CO 2 ) were measured, as well as soil mineral N, yield components and 15 N recovery in plant and soil. During the maize cropping period, the use of DMPSA significantly reduced cumulative N 2 O emissions (118 g N ha −1 ) compared to ammonium nitrate without inhibitor (231 g N ha −1 ). The 15 N analyses revealed that most N 2 O losses (particularly during the emission peak) came from 15 NH 4 NO 3 (i.e. nitrification, nitrifier denitrification and/or coupled nitrification denitrification) rather than NH 4 15 NO 3 in this calcareous low C-content soil. As expected, DMPSA decreased N 2 O losses from 15 NH 4 + oxidation, but an effect on non-target microorganisms was noticed, as shown by the significant reduction of respiration rates and N 2 O losses coming from 15 NO 3 − . No significant effect of DMPSA on CH 4 oxidation or 15 N 2 fluxes was observed. The DMPSA did not lead to a significant improvement of the dry weights of grain or biomass, although an increment of root biomass by 64% was found. This compound also tended to increase plant N recovery (average 67.8%) and to decrease soil N recovery (average 18.3%) but differences were not statistically significant. Conversely, the nitrification inhibitor significantly reduced the residual fertilizer-N in the 15–30 cm and 30–45 cm soil layers. The use of DMPSA was confirmed as a highly effective tool to reduce N 2 O emissions from irrigated crops in semi-arid areas. [ABSTRACT FROM AUTHOR]

Agricultural soils are a major source of nitric- (NO) and nitrous oxide (N 2 O), which are produced and consumed by biotic and abiotic soil processes. The dominant sources of NO and N 2 O are microbial nitrification and denitrification, and emissions of NO and N 2 O generally increase after fertiliser application. The present study investigated the impact of N-source distribution on emissions of NO and N 2 O from soil and the significance of denitrification, rather than nitrification, as a source of NO emissions. To eliminate spatial variability and changing environmental factors which impact processes and results, the experiment was conducted under highly controlled conditions. A laboratory incubation system (DENIS) was used, allowing simultaneous measurement of three N-gases (NO, N 2 O, N 2 ) emitted from a repacked soil core, which was combined with 15 N-enrichment isotopic techniques to determine the source of N emissions. It was found that the areal distribution of N and C significantly affected the quantity and timing of gaseous emissions and 15 N-analysis showed that N 2 O emissions resulted almost exclusively from the added amendments. Localised higher concentrations, so-called hot spots, resulted in a delay in N 2 O and N 2 emissions causing a longer residence time of the applied N-source in the soil, therefore minimising NO emissions while at the same time being potentially advantageous for plant-uptake of nutrients. If such effects are also observed for a wider range of soils and conditions, then this will have major implications for fertiliser application protocols to minimise gaseous N emissions while maintaining fertilisation efficiency. [ABSTRACT FROM AUTHOR]

Agricultural soils are a major source of nitric oxide (NO) and nitrous oxide (N 2 O), which are produced and consumed by biotic and abiotic soil processes. The dominant sources of NO and N 2 O are microbial nitrification and denitrification. While N 2 O emissions have been attributed to both processes, depending on the environmental conditions such as substrate availability, pH and water filled pore space (WFPS), NO emissions are thought to predominantly derive from nitrification. Although attributing gaseous emissions to specific processes is still difficult, recent findings challenge the latter of those assumptions. Using the gas-flow-soil-core method, i.e soil cores incubated under a He/O 2 atmosphere at constant surface gas flow, combined with 15 N labelled isotopic techniques, the present study investigated the role of denitrification on NO, N 2 O and N 2 emissions in a UK grassland soil under high soil moisture and an aerobic headspace atmosphere. With the application of KNO3 and glucose to support denitrification, denitrification was the source of N loss of between 0.61 and 0.67% of the added N via NO emissions, 1.60–1.68% via N 2 O and 0.03–0.05% via N 2 emissions. Overall, our study showed that denitrification has been overlooked as a source of NO emissions. [ABSTRACT FROM AUTHOR]

China accounts for a third of global nitrogen fertilizer consumption. Under an International Panel on Climate Change (IPCC) Tier 2 assessment, emission factors (EFs) are developed for the major crop types using country-specific data. IPCC advises a separate calculation for the direct nitrous oxide (N 2 O) emissions of rice cultivation from that of cropland and the consideration of the water regime used for irrigation. In this paper we combine these requirements in two independent analyses, using different data quality acceptance thresholds, to determine the influential parameters on emissions with which to disaggregate and create N 2 O EFs. Across China, the N 2 O EF for lowland horticulture was slightly higher (between 0.74% and 1.26% of fertilizer applied) than that for upland crops (values ranging between 0.40% and 1.54%), and significantly higher than for rice (values ranging between 0.29% and 0.66% on temporarily drained soils, and between 0.15% and 0.37% on un-drained soils). Higher EFs for rice were associated with longer periods of drained soil and the use of compound fertilizer; lower emissions were associated with the use of urea or acid soils. Higher EFs for upland crops were associated with clay soil, compound fertilizer or maize crops; lower EFs were associated with sandy soil and the use of urea. Variation in emissions for lowland vegetable crops was closely associated with crop type. The two independent analyses in this study produced consistent disaggregated N 2 O EFs for rice and mixed crops, showing that the use of influential cropping parameters can produce robust EFs for China. [ABSTRACT FROM AUTHOR]

RATIONALE This study aimed (i) to determine the isotopic fractionation factors associated with N2O production and reduction during soil denitrification and (ii) to help specify the factors controlling the magnitude of the isotope effects. For the first time the isotope effects of denitrification were determined in an experiment under oxic atmosphere and using a novel approach where N2O production and reduction occurred simultaneously. METHODS Soil incubations were performed under a He/O2 atmosphere and the denitrification product ratio [N2O/(N2 + N2O)] was determined by direct measurement of N2 and N2O fluxes. N2O isotopocules were analyzed by mass spectrometry to determine δ18O, δ15N and 15 N site preference within the linear N2O molecule (SP). An isotopic model was applied for the simultaneous determination of net isotope effects (η) of both N2O production and reduction, taking into account emissions from two distinct soil pools. RESULTS A clear relationship was observed between 15 N and 18O isotope effects during N2O production and denitrification rates. For N2O reduction, diverse isotope effects were observed for the two distinct soil pools characterized by different product ratios. For moderate product ratios (from 0.1 to 1.0) the range of isotope effects given by previous studies was confirmed and refined, whereas for very low product ratios (below 0.1) the net isotope effects were much smaller. CONCLUSIONS The fractionation factors associated with denitrification, determined under oxic incubation, are similar to the factors previously determined under anoxic conditions, hence potentially applicable for field studies. However, it was shown that the η18O/η15N ratios, previously accepted as typical for N2O reduction processes (i.e., higher than 2), are not valid for all conditions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Carbon (C) and nitrogen (N) process-based models are important tools for estimating and reporting greenhouse gas emissions and changes in soil C stocks. There is a need for continuous evaluation, development and adaptation of these models to improve scientific understanding, national inventories and assessment of mitigation options across the world. To date, much of the information needed to describe different processes like transpiration, photosynthesis, plant growth and maintenance, above and below ground carbon dynamics, decomposition and nitrogen mineralization. In ecosystem models remains inaccessible to the wider community, being stored within model computer source code, or held internally by modelling teams. Here we describe the Global Research Alliance Modelling Platform (GRAMP), a web-based modelling platform to link researchers with appropriate datasets, models and training material. It will provide access to model source code and an interactive platform for researchers to form a consensus on existing methods, and to synthesize new ideas, which will help to advance progress in this area. The platform will eventually support a variety of models, but to trial the platform and test the architecture and functionality, it was piloted with variants of the DNDC model. The intention is to form a worldwide collaborative network (a virtual laboratory) via an interactive website with access to models and best practice guidelines; appropriate datasets for testing, calibrating and evaluating models; on-line tutorials and links to modelling and data provider research groups, and their associated publications. A graphical user interface has been designed to view the model development tree and access all of the above functions. [ABSTRACT FROM AUTHOR]

Understanding the behaviour of grazing animals at pasture is crucial in order to develop management strategies that will increase the potential productivity of grazing systems and simultaneously decrease the negative impact on the environment. The objective of this review was to summarize and analyse the scientific literature that has addressed the site use preference of grazing cattle using global positioning systems (GPS) collars in the past 21 years (2000–2020) to aid the development of more sustainable grazing livestock systems. The 84 studies identified were undertaken in several regions of the world, in diverse production systems, under different climate conditions and with varied methodologies and animal types. This work presents the information in categories according to the main findings reviewed, covering management, external and animal factors driving animal movement patterns. The results showed that some variables, such as stocking rate, water and shade location, weather conditions and pasture (terrain and vegetation) characteristics, have a significant impact on the behaviour of grazing cattle. Other types of bio-loggers can be deployed in grazing ruminants to gain insights into their metabolism and its relationship with the landscape they utilise. Changing management practices based on these findings could improve the use of grasslands towards more sustainable and productive livestock systems. [ABSTRACT FROM AUTHOR]

Bacteria and fungi have been shown to produce nitrous oxide (N 2 O) during denitrification, but their contribution after nitrate (NO 3 −) application to soil is not clearly established. In a microcosm experiment, the relative contribution of bacteria and fungi to N 2 O and carbon dioxide (CO 2) production by four contrasting soils representing different land uses after KNO 3 addition was studied. The soils were daily wetted to 80% water-filled pore space (WFPS) and kept under greenhouse conditions for 10 days. The fungicide cycloheximide and the bactericide streptomycin were used to determine the possible microbial origin of the N 2 O and CO 2 emissions. Non-target effects of the antibiotics on the emission of N 2 O and CO 2 were evaluated using the inhibitor additivity ratio (IAR). The abundance of the bacterial and fungal communities was estimated by quantitative PCR (qPCR) of the bacterial 16S rRNA gene and the fungal internal transcribed spacer (ITS) region, respectively. The gene copy number of bacterial denitrifiers was calculated after quantification of the nirK , nirS , norB , nosZ I and nosZ II genes. After 10 d, regardless of the soil type, the cumulative N 2 O emission from the soils treated with cycloheximide or streptomycin were similar. In all the four soils, N 2 O fluxes were greater (on average 1.8 ± 0.3 times) in soils amended with the fungicide than with the bactericide during incubation for the first 48–96 h. Greater N 2 O emissions (on average 1.7 ± 0.2 times) were detected in soils where bacteria were inhibited in comparison to those treated with the fungicide from 96 to 240 h. On average, 68.5% of the total CO 2 emitted during the 10-d incubation period was produced in soils treated with the fungicide and 31.5% in those treated with the bactericide. The greater contribution of bacteria to the production of N 2 O than fungi during the first 48–96 h was possibly due to a faster used of nitrate. Variations in the abundance of bacterial 16S rRNA genes, the ITS region, and the nirK , nirS , norB and nosZ I bacterial denitrification genes indicated that the antibiotics used to prevent the growth of bacteria and fungi were effective during incubation. These results suggest that both bacteria and fungi should be considered when designing and applying greenhouse gas mitigation strategies in soils and that their relative contribution to produce N 2 O and CO 2 can vary with time and nitrate availability. • In a 10-d microcosm experiment, bacteria dominated fungi for N 2 O emissions during the first 3 d after N-fertilisation. • Fungi dominated bacteria for N 2 O emissions during the remaining 7-d of treatment. • After 10-d, bacteria and fungi similarly contributed to N 2 O production in the four soils analysed. • Bacteria were greater CO 2 producers than fungi after the 10-d treatment in the four soils analysed. • Bacteria and fungi should be considered when designing greenhouse gas mitigation strategies. [ABSTRACT FROM AUTHOR]

• Heterotrophic nitrification is an important source of N 2 O at low WFPS. • Similar contributions of nitrification, heterotrophic nitrification and denitrification occurred at medium WFPS level. • High N 2 O emissions result via nitrification coupled denitrification at medium & high WFPS. • Abiotic factors need to be considered as well as biotic factors to understand the cause of emissions. To identify the production and consumption pathways and temporal dynamics of N 2 O emitted from soil, this study uses 15N-labelled substrate-N to quantify the underlying gross N transformation rates using the Ntrace analysis tool and link them to N-emissions. In three experiments twelve soil cores each were incubated in a lab incubation system to measure gaseous emissions, while parallel incubations under the same conditions were set up for destructive soil sampling at 7 time points. Using the triple labelling technique (applying NH 4 NO 3 with either the NH 4 +-N or the NO 3 −-N, or both being 15N labelled), this study investigated the effects of 55, 70 and 85% water filled pore space (deemed to promote nitrification, both nitrification and denitrification, and denitrification, respectively) in a clay soil on gaseous N emissions and investigates the source and processes leading to N 2 O emissions. To assess the utilisation of applied NO 3 − vs. nitrified NO 3 − from applied NH 4 +, the 15N tracing tool Ntrace was used to quantify the rates of immobilisation of NO 3 − and NH 4 +, oxidation of NH 4 +, mineralisation of organic N and subsequent nitrification by the analysis of the 15N in the soil. Gross transformation rates were calculated, indicating the relative importance of added NO 3 − and NO 3 − derived from nitrified added NH 4 +. Results show an important contribution of heterotrophic nitrification (organic N oxidation to NO 3 −) which was highest at the 55% water filled pore space (WFPS), decreasing in its contribution to N-transformation processes with increasing WFPS, while nitrification (NH 4 + oxidation to NO 3 −) was contributing the most at 70% WFPS. The contribution of denitrification increased with increasing WFPS, but only became dominant at 85% WFPS. While denitrification still showed to be most important at high and nitrification at lower WFPS, the actual % WFPS values were not as expected and highlight the fact that WFPS is a contributor, but not the sole/most important parameter determining the type of N-transformation processes taking place. [ABSTRACT FROM AUTHOR]

• Sheep urination data is important for quantifying downstream nitrogen losses. • Assessed frequency, volume and chemical composition of sheep urine events. • Greater N excretion rate for sheep on improved versus semi-improved pasture. • Site and seasonal differences in sheep urine chemical composition observed. • Data will be useful for modelling/experimental studies assessing urine-N losses. Ruminant urine patches are potential sites of reactive nitrogen (N) loss to the environment. Quantification of N losses from grazed grasslands requires measurement of the frequency of urine deposition, as well as its volume and chemical composition. However, studies to date are typically restricted to analyses of few replicate animals and urination events, especially for sheep. Here, we present data on urine frequency, volume, chemical composition (n = 193 events from n = 6 sheep) and metabolomic profile (n = 4–5 events from n = 4–5 sheep) from penned sheep. Differences in urine parameters and chemical composition data were compared seasonally and between two sites (improved and semi-improved pasture). Sheep urinated 8–11 times d−1, assuming time within pens represented a 24 h period. The mean urine event volume recorded was 289 ± 14 mL, from which we estimated a daily urine production value of 2.77 ± 0.15 L urine sheep−1 d−1. Daily urine N excretion and individual urine N concentrations were greater from sheep in improved pasture (26.7 ± 2.3 g N sheep−1 d−1; 7.0 ± 0.2 g N L−1) compared to those in semi-improved pasture (16.7 ± 1.2 g N sheep−1 d−1; 5.5 ± 0.4 g N L−1), but this did not equate to greater individual urine patch N loadings due to site differences in the urine-to-soil surface area influenced (17.5 L m-2 at the semi-improved site and 8.9 L m-2 at the improved site). Urine chemical composition varied seasonally and by site. Site- and season-specific urine should, therefore, be used in studies assessing N losses from urine patches. Based on the urine chemical composition data, we provide an updated artificial sheep urine 'recipe' which could be utilised to replicate natural sheep urine. The urine metabolomic profile clustered according to pasture quality, while clustering according to season was less evident. Our results provide important information for experimental and modelling studies assessing the scale and nature of N pollution arising from sheep-grazed pastures. [ABSTRACT FROM AUTHOR]

Nitrogen (N) stabilizers such as urease inhibitors (UI) and nitrification inhibitors (NI) are promising tools to mitigate N losses from fertilized soils. To better understand the efficacy of UI and NI, a 2-year field trial was carried out in the North China Plain (NCP) to analyze the impact of UI and NI on NH 3 loss and N transformations following urea fertilizer application. Additionally, a laboratory study using an automated continuous-flow incubation system was conducted under controlled conditions, using the same soil, to evaluate the mitigation potential of the N stabilizers on NO, N 2 O and CO 2 emission. The results showed that a novel UI product, Limus® (BASF, Germany), containing active ingredients N-(n-butyl) thiophosphoric triamide (NBPT) and N-(n-propyl) thiophosphoric triamide (NPPT), limited ammonium formation rate and reduced NH 3 loss in both maize (by 85 and 96% for year 1 and 2, respectively) and wheat (by 41 and 64%, for year 1 and 2, respectively) seasons. The 3, 4-dimethypyrazole phosphate (DMPP) amendment significantly retarded nitrate formation rate but the effectiveness was compromised by high ambient temperature; additionally, the NI amendment increased NH 3 emission (by 16 and 24% for maize and wheat year 2, respectively). In the laboratory incubation experiment, addition of the UI reduced emissions of NO, N 2 O and CO 2 by 89, 73 and 19%, respectively, while the addition of the NI reduced the respective emissions by 95, 83 and 24% over the 16 d incubation period. These results suggest that N stabilizers can play a significant role in the mitigation of the environmental impacts of intensive agriculture, and, in particular, that the UI amendment may have the better potential to reduce N losses in the climatic and soil conditions of the NCP, and that the NI should be avoided under high ambient temperatures. Image 1 • Urease inhibitor amendment of urea reduced NH 3 , NO and N 2 O emissions. • Nitrification inhibitor amendment of urea reduced NO and N 2 O but increased NH 3 emissions. • Efficacy of the nitrification inhibitor was compromised by high ambient temperature. • Urease and nitrification inhibitor amendment of urea reduced CO 2 emissions. [ABSTRACT FROM AUTHOR]