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We quantified nitrous oxide emission factors (N2O EFs) for cattle urine patches established using two simulation methods: (1) a uniformly wetted area (UWA) and (2) a naturally expanding effective area (NEEA). Field experiments were conducted on long-term grasslands in New Zealand (NZ1 and NZ2) and Ireland (IRE) for varying urine nitrogen (N) application rates in two initial soil moisture regimes (below field capacity and field capacity). Nitrous oxide emissions were measured using static chambers for a period of 120, 133 and 85 days at NZ1, NZ2 and IRE, respectively. Nitrous oxide EFs were unaffected by patch type (UWA = 0.99%; NEEA = 1.07%) across varying urine N application rates in NZ1 whereas in NZ2, EFs varied with urine N application rate only for the NEEA patches in below field capacity soils (P

The effect of long-term soil phosphorus (P) on in situ nitrous oxide (N2O) emissions from temperate grassland soil ecosystems is not well understood. Grasslands typically receive large nitrogen (N) inputs both from animal deposition and fertiliser application, with a large proportion of this N being lost to the environment. Understanding optimum nutrient stoichiometry by applying N fertilisers in a relative balance with P will help to reduce N losses by enabling maximum N-uptake by plants and microbes. This study investigates the N2O response from soils of long-term high and low P management receiving three forms of applied N at two different rates: a nitrate-based fertiliser (KNO3) and an ammonium-based fertiliser ([NH4]2SO4) (both at 40 Kg N ha−1), and a synthetic urine (750 Kg N ha−1). Low soil P significantly increased N2O emissions from KNO3 and (NH4)2SO4 fertilisers by over 50% and numerically increased N2O from urine by over 20%, which is suggested to be representative of the lack of significant effect of N fertilisation on N-uptake observed in the low P soils. There was a significant positive effect of soil P on grass N-uptake observed in the synthetic urine and KNO3 treatments, but not in the (NH4)2SO4 treatment. Low P soils had a significantly lower pH than high P soilss and responded differently to applied synthetic urine. There was also a significant effect of P level on potential nitrification which was nearly three times that of low P, but no significant difference between potential denitrification and P level. The results from this study highlight the importance of synergy between relative nutrient applications as a deficiency of one nutrient, such as P in this case, could be detrimental to the system as a whole. Optimising soil P can result in greater N uptake (over 12, 23 and 66% in (NH4)2SO4, KNO3 and synthetic urine treatments, respectively) and in reduced emissions by up to 50% representing a win-win scenario for farmers. Teagasc Department of Agriculture, Australian Government, Food, and the Marine Open access funding provided by IReL

Most nitrogen (N) lost to the environment from grazed grassland is produced as a result of N excreted by livestock, released in the form of nitrous oxide (N2O) emissions, nitrate leaching and ammonia volatilisation. In addition to the N fertiliser applied, excreta deposited by grazing livestock constitute a heterogeneous excess of N, creating spatial hotspots of N losses. This study presents a yearlong N2O emissions map from a typical intensively managed temperate grassland, grazed periodically by a dairy herd. The excreta deposition mapping was undertaken using high-resolution RGB images captured with a remotely piloted aircraft system combined with N2O emissions measurements using closed statics chambers. The annual N2O emissions were estimated to be 3.36 ± 0.30 kg N2O–N ha−1 after a total N applied from fertiliser and excreta of 608 ± 40 kg N ha−1 yr−1. Emissions of N2O were 1.9, 3.6 and 4.4 times lower than that estimated using the default IPCC 2019, 2006 or country-specific emission factors, respectively. The spatial distribution and size of excreta deposits was non-uniform, and in each grazing period, an average of 15.1% of the field was covered by urine patches and 1.0% by dung deposits. Some areas of the field repeatedly received urine deposits, accounting for an estimated total of 2410 kg N ha−1. The method reported in this study can provide better estimates of how management practices can mitigate N2O emissions, to develop more efficient selective approaches to fertiliser application, targeted nitrification inhibitor application and improvements in the current N2O inventory estimation.

Dairy processing sludge is currently a bio-based fertiliser being spread to grassland without knowledge pertaining to its phosphorus (P) or nitrogen (N) fertiliser replacement value. This creates uncertainty of desired crop yield achievement and unproductive nutrient recycling and also poses a great challenge to the dairy milk processing industry in promoting their food processing by-product as valuable recyclable fertiliser. Therefore four representative samples, i.e. two activated sludge (aluminium-precipitated (Al-sludge) and iron-precipitated (Fe-sludge)), and two lime-stabilised calcium-precipitated sludge (Ca1- and Ca2-sludge), were examined at field scale to assess P and N availability for crop yield and uptake in comparison to reference mineral fertilisers over one seasonal year. The field plots were set-up on a light textured clay loam soil within the optimum plant available P (Morgan's soil P index 3, i.e. medium / adequate soil P level) in two separate adjoining areas consisting of P and N availability experiments. Each experiment consisted of 40 plots (each 8×2 m2) of 10 treatments with 4 replications arranged in a randomised complete block design. All dairy sludge (40 kg-P ha−1) and mineral P treatments (rates 0–50 kg-P ha−1) produced similar yields and uptake, and crop P was not affected by sludge applications despite the presence of high Al, Ca and Fe. During the experiment there was no significant change in P index (stayed at index 3) indicating that no treatment caused a decline in P into index 2 (i.e. low soil P level), therefore replacing P removed by the crop. The only change in Morgan's P was observed in the Ca-sludge treatments, but this was due to Morgan's reagent overestimating plant available P in high Ca conditions. From N trial plots a significantly higher grass yield and N uptake was observed for Fe and both Ca-type sludge applied plots than the control (zero N) plot during the 1st harvest, while no statistical difference observed in the subsequent harvests (up to 4th harvesting). The N fertiliser replacement value (derived from mineral N response) of sludge samples was observed to be in the order of Fe (54%)>Ca2 (25%)>Ca1 (22%)>Al (8%) with greater promise of N fertiliser efficiency of Fe and Ca types. Overall these bio-based sludges show promise in recycling P and N for grassland application but longer term trials in other soil types considering other environmental aspects (losses to soil, water and air) can further optimize the management of dairy sludge as an alternative to chemical fertiliser.

Objective Urea is one of the most widely used commercial fertilisers worldwide due to its high N density and cost effectiveness. However, it can be lost in the form of gaseous ammonia and other greenhouse gas (GHG) emissions which can potentially lead to environmental pollution. Farmers are compelled to apply more urea to account for those losses, thereby increasing their expenditure on fertilization. The objective of this paper is to present a literature review on current knowledge regarding inhibitor technologies such as urease inhibitor; n-(N-butyl) thiophosphoric triamide (NBPT), and nitrification inhibitor; dicyandiamide (DCD). Methods A thorough review of all the scientific literature was carried out and a proposed risk assessment framework developed. Results The study showed that the urease inhibitor NBPT significantly reduced NH3 loss from urea. However, concerns about NBPT safety to human health had been raised when the nitrification inhibitor DCD appeared as a residue in milk. This article presents a risk assessment framework for evaluating human exposure to chemicals like NBPT or DCD, following the consumption of foods of animal origin (e.g. milk) from cows grazing on inhibitor-treated pasture. Conclusion The EU’s target of a 40% reduction of greenhouse gas emissions by 2030 can be aided by using NBPT as part of an overall suite of solutions. A comprehensive risk assessment is advised for effective evaluation of potential risks from exposure to these inhibitors.

Multispecies grasslands can alter nitrogen (N) cycling processes. A mesocosm experiment was performed comparing bare soil, soil planted with perennial ryegrass (Lolium perenne), white clover (Trifo...

Dairy processing wastewater treatment sludge (DPWTS) is applied to grassland to recycle valuable nutrients and organic matter. Until recently the chemical composition of the dominant DPWTS types (calcium, aluminium or iron rich) was unknown, but the latest study (Ashekuzzaman et al. in J Clean Prod 230:1266–1275, 2019) indicates that DPWTS has high nitrogen (N) and phosphorus (P) content and their inherent chemical properties may influence their availability and losses. Herein for the first time edge of field-losses and plant-available P changes are simulated in an agitator test 48 h after application. In terms of overall losses, metals are not of concern across treatment types, iron-rich DPWTS has the highest losses in terms of concentration of ammonium-N and carbon, whereas calcium-rich DPWTS has the highest dissolved reactive P (DRP) losses but lowest losses of ammonium-N and carbon. The loss of DRP was found to be strongly positively associated with the increase in water-extractable P, degree of P saturation, Morgan’s and Mehlich-3 extractable phosphorus (Pm, M3-P), respectively. Runoff concentrations presented here represent edge of field-losses and may not represent final concentrations entering a surface waterbody. In terms of plant-available P, there were no negative effects with Pm exhibiting a positive trend across DPWTS types and soils. In particular, a significant increase was found for the calcium-rich DPWTS across all soils (average increase in Pm by fivefold). As applying DPWTS to grassland is an understudied area, further field trials should focus on emissions to air and water and examine the fertilizer value from N and P perspectives. Thus a better management of DPWTS as fertiliser can be maintained from an agronomic and environmental context.

Quantifying nitrous oxide (N2O) emissions from grazed pastures can be problematic due to the presence of hotspots and hot moments of N2O from animal excreta and synthetic fertilisers. In this study, we quantified field scale N2O emissions from a temperate grassland under a rotational grazing management using eddy covariance (EC) and static chamber techniques. Measurements of N2O by static chambers were made for four out of nine grazing events for a control, calcium ammonium nitrate (CAN), synthetic urine (SU) + CAN and dung + CAN treatments. Static chamber N2O flux measurements were upscaled to the field scale (FCH FIELD) using site specific emission factors (EF) for CAN, SU+CAN and dung + CAN. Mean N2O EFs were greatest from the CAN treatment while dung + CAN and SU + CAN emitted similar N2O-N emissions. Cumulative N2O-N emissions over the study period measured by FCH FIELD measurements were lower than gap-filled EC measurements. Emission factors of N2O from grazing calculated by FCH FIELD and gap-filled were 0.72% and 0.96%, respectively. N2O-N emissions were derived mainly from animal excreta (dung and urine) contributing 50% while N2O-N losses from CAN and background accounted for 36% and 14%, respectively. The study highlights the advantage of using both the EC and static chamber techniques in tandem to better quantify both total N2O-N losses from grazed pastures while also constraining the contribution of individual N sources. The EC technique was most accurate in quantifying N2O emissions, showing a range of uncertainty that was seven times lower relative to that attributed to static chamber measurements, due to the small chamber sample size per treatment and highly variable N2O flux measurements over space and time.

Animal waste contains high numbers of microorganisms and therefore can present a potential biological threat to human health. During episodic rainfall events resulting in runoff, microorganisms in the waste and soil may migrate into surface runoff, contaminating surface water resources. A probabilistic human exposure (HE) model was created to determine exposure to faecal indicator bacteria (FIB): total coliforms (TC), E. coli and enterococci following application of bio-based fertiliser (dairy cattle slurry, digestate) to grassland; using a combination of experimental field results and literature-based data. This step was followed by a quantitative microbial risk assessment (QMRA) model for pathogenic E. coli based on a literature-based dose-response model. The results showed that the maximum daily HE (HEdaily) is associated with E. coli for unprocessed slurry (treatment T1) on day 1, the worst-case scenario where the simulated mean HEdaily was calculated as 2.84 CFU day -1. The results indicate that the overall annual probability of risk (Pannual) of illness from E. coli is very low or low based on the WHO safe-limit of Pannual as 10 -6. In the worst-case scenario, a moderate risk was estimated with simulated mean Pannual as 1.0 × 10 -5. Unpasteurised digestate application showed low risk on day 1 and 2 (1.651 × 10 -6, 1.167 × 10 -6, respectively). Pasteurised digestate showed very low risk in all scenarios. These results support the restriction imposed on applying bio-based fertiliser if there is any rain forecast within 48 h from the application time. This study proposes a future extension of the probabilistic model to include time, intensity, discharge, and distance-dependant dilution factor. The information generated from this model can help policymakers ensure the safety of surface water sources through the quality monitoring of FIB levels in bio-based fertiliser. ispartof: JOURNAL OF ENVIRONMENTAL MANAGEMENT vol:299 ispartof: location:England status: published

Microbial disease outbreaks related to fresh produce consumption, including leafy green vegetables, have increased in recent years. Where contamination occurs, pathogen persistence may represent a risk for consumers’ health. This study analysed the survival of E. coli and L. innocua on lettuce plants watered with contaminated irrigation water via a single irrigation event and within stored irrigation water. Separate lettuce plants (Lactuca sativa var. capitata) were irrigated with water spiked with Log10 7 cfu/mL of each of the two strains and survival assessed via direct enumeration, enrichment and qPCR. In parallel, individual 20 L water microcosms were spiked with Log10 7 cfu/mL of the individual strains and sampled at similar time points. Both strains were observed to survive on lettuce plants up to 28 days after inoculation. Direct quantification by culture methods showed a Log10 4 decrease in the concentration of E. coli 14 days after inoculation, and a Log10 3 decrease in the concentration of L. innocua 10 days after inoculation. E. coli was detected in water samples up to 7 days after inoculation and L. innocua was detected up to 28 days by direct enumeration. Both strains were recovered from enriched samples up to 28 days after inoculation. These results demonstrate that E. coli and L. innocua strains are able to persist on lettuce after a single contamination event up until the plants reach a harvestable state. Furthermore, the persistence of E. coli and L. innocua in water for up to 28 days after inoculation illustrates the potential for multiple plant contamination events from stored irrigation water, emphasising the importance of ensuring that irrigation water is of a high quality.

Anaerobic digestion (AD) has been identified as a potential green technology to treat food and municipal waste, agricultural residues, including farmyard manure and slurry (FYMS), to produce biogas. FYMS and digestate can act as soil conditioners and provide valuable nutrients to plants; however, it may also contain harmful pathogens. This study looks at the critical indicators in determining the microbial inactivation potential of AD and the possible implications for human and environmental health of spreading the resulting digestate on agricultural land. In addition, available strategies for risk assessment in the context of EU and Irish legislation are assessed. Storage time and process parameters (including temperature, pH, organic loading rate, hydraulic retention time), feedstock recipe (carbon-nitrogen ratio) to the AD plant (both mesophilic and thermophilic) were all assessed to significantly influence pathogen inactivation. However, complete inactivation of all pathogens is unlikely. There are limited studies evaluating risks from FYMS as a feedstock in AD and the spreading of resulting digestate. The lack of process standardisation and varying feedstocks between AD farms means risk must be evaluated on a case by case basis and calls for a more unified risk assessment methodology. In addition, there is a need for the enhancement of AD farm-based modelling techniques and datasets to help in advancing knowledge in this area.

Globally, the processing of milk and dairy products leads to huge volumes of dairy processing wastewater treated sludge. Currently, there are knowledge gaps relating to the volumes generated and the nutrient and metal contents of these sludges. This lack of knowledge prevents the dairy processing industry from making informed pre and post waste generation decisions. Using Ireland as a case study volumes generated are estimated (2012–2017) and a two year seasonal database (2016–2018) across four sludge types (bio-chemically treated activated sludge; lime treated dissolved air flotation processing sludge; a combined treatment sludge and anaerobically digested sludge) utilising samples from nine dairy processing plants was created. Results show that dairy processing sludge increased by 39% in the period up to 126,718 tonnes (wet weight). Database results showed that nutrient contents did not vary seasonally but varied significantly across sludge type and processing plants. The median values (g kg−1 dry weight) for N:P:K for the four sludge types were N: 57.2, 19.5, 46 and 70.4, P: 36.8, 65.9, 20 and 14.6, and K: 7.2, 3.9, 2.9 and 6.1, respectively. Heavy metal concentrations across all samples were significantly lower than those regulated by the European Union for controlling metals accumulation in agricultural land due to sludge recycling. The characterization profile presented in this paper serves as a national and international reference database for future investigations that focus on the valorisation of dairy processing sludge.

Urine is a critical nitrogen (N) input in temperate grazed grasslands and can drive substantial nitrous oxide (N2O) production in soils. However, it remains unclear how differences in the N input rate affect N2O fluxes and vary between different grassland soils. The effect of increasing urine N application on ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−) concentrations and N2O production was tested in two grassland soils, a free-draining loam and an imperfectly drained sandy-loam. It was hypothesized that high-urine N application rates would lead to ammonia/ammonium (NH3/NH4+) accumulation influencing N transformation rates and N2O production which differ between grassland soils. Fresh cattle urine was applied at rates equivalent to 300 and 1000 kg N/ha in an aerobic incubation experiment. Soils were destructively sampled over 80 days to measure changes in inorganic-N and pH. The higher N addition rate was associated with elevated NH3concentrations up to day 35 in soils, probably inhibiting NO2−to NO3−reduction. In contrast, there was no inhibition of nitrification in the 300 kg N/ha treatment. Cumulative N2O fluxes were greatest from the 300 kg N/ha treatment for the loam soil, but were greater for the sandy-loam under the 1000 kg N/ha treatment. The results also show that differences in soil properties, in particular carbon availability, can be important in regulating N transformation and N2O production. Collectively, these results demonstrate the proposed mechanism of nitrification inhibition at high-N input rates, driven by either high NH3/NH4and/or increased levels of NH4HCO3from urea hydrolysis.

Pyrogenic char (PC) materials derived from the pyrolysis of dairy processing sludge (DPS) could be a cost effective option to develop carbonaceous adsorbent for phosphorus (P) removal from wastewater. The main objectives of the present work were to: (1) determine the efficacy of DPS derived PC (DPS-PC) to remove P from synthetic and dairy wastewater samples, (2) identify possible P removal mechanisms, and identify parameters that could be used to quickly identify the P removal capacity of a char and (3) propose a ranking system for the selection of DPS-PC which includes energy, char yield and P removal criterion. DPS-PC samples were obtained from the pyrolysis process (700 °C) of two sludge streams: (1) bio-chemically treated mixed sludge and (2) lime treated dissolved air floatation (DAF) sludge. Herein, 12 DPS-PC samples were assessed and pre-screened in batch experiments to determine the P removal efficacy from both synthetic and dairy wastewater solutions. The effect of solid to liquid dosage, contact time, pH and P concentration was investigated. Statistical regression and correlation analyses were performed to understand P removal mechanism. The quantitative assessment of char yield, energy balance and P removal performance were combined to propose a ranking system for DPS feedstock selection. P removal varied across DPS-PC type and composition, with mixed sludge derived char exhibiting 85–98% P removal at a dose of between 10 and 50 g/L, whereas, those from DAF sludge removed > 99% at 3 g/L. The P removal process was associated with a number of strongly significant mineral phase correlations pertaining to mineral composition (i.e. availability of Ca, Mg and Si) of the DPS-PC samples. A quick water extractible P test together with knowledge of the major P locking minerals can be used to pre-screen the potential of PC for P removal application. This study also provides a physicochemical reference and ranking of DPS feedstock selection, which will be useful for future investigation on the pyrolysis of DPS at pilot-scale and subsequently, to develop PC based efficient adsorbent for application in wastewater treatment.

Using earthen liners at the base of an integrated constructed wetland (ICW) maintains a hydraulic continuum between the ICW and the underlying groundwater body. This may enable migration of reactive carbon (dissolved organic and inorganic carbon (DOC, DIC)) and reactive nitrogen (Nr) across this liner to groundwater along this continuum to groundwater. Therefore, in terms of a holistic assessment of ICWs, quantification of these losses is important and indeed from an environmental perspective comparing such losses to other ICW dis-connected areas within the same groundwater body is critical. The main objective of the present study on an ICW site in SE Ireland was to compare reactive forms of C and N in groundwater (three piezometer nests) representing the continuum end point of ICW Cell 2 and 3 with that of groundwater dis-connected to the ICW system. For this purpose two control planes consisting of shallow and deep groundwater piezometer nests were installed and monitored at 1 and 4 m depths, respectively underneath the earthen liners at 0.2 m adjacent to the ICW cells. Fieldwork was conducted between Nov 2013 and Nov 2014 and results showed that groundwater beneath the ICW liner had a highly reduced signal with C and N concentrations being significantly higher to those of the disconnected up-gradient groundwater. The DOC, DIC and dissolved CO2 and CH4 concentrations in groundwater beneath the ICW cells were significantly higher than the up-gradient groundwater. All the reactive forms of C were higher in Cell 2 than in Cell 3. With respect to depth, all forms of reactive C were higher in deeper groundwater than the shallow equivalents except for DOC. Equally, Nr concentrations (NH4+, DON, NO3−-N and N2O) were higher in groundwater beneath the ICW cells than the up-gradient groundwater. They were higher in Cell 2 than in Cell 3 and higher in shallow rather than deep groundwater. The fate of the reactive C and N is unknown. Typically DOC delivery from groundwater to surface water drives many biogeochemical processes as an electron donor to microbes or can be converted to CO2 and CH4 emissions and the dissolved CO2 and CH4 can be indirectly exchanged to the atmosphere. The results suggest that nutrient delivery from the ICW cells to the underlying groundwater needs to be evaluated and the design of earthen-lined ICWs should consider this nutrient loss continuum across the liner.

N-(n-butyl) thiophosphoric triamide (NBPT) is a urease inhibitor utilised in urea-based fertilizers. In Ireland, fertilizer treated with NBPT is applied to pasture to mitigate both ammonia and nitrous oxide emissions, but concerns arise as to the potential for residues in milk products. A quick ultrafiltration extraction and ultra-high performance liquid chromatography coupled with mass spectrometry triple quadrupole (UHPLC-MS/MS) quantitation method was developed and validated in this study. The method was applied in the analysis of samples collected from a field study investigating potential transfer of NBPT residues into milk. NBPT and NBPTo residues, were extracted from fortified milk samples and analysed on a UHPLC-MS/MS with recoveries ranging from 74 to 114%. Validation of the UHPLC-MS/MS method at low (0.0020 mg kg-1) and high (0.0250 mg kg-1) concentration levels in line with SANTE/12682/2019 showed overall trueness in the range of 99 to 104% and precision between 1 and 10%, RSD for both compounds. The limit of quantitation (LOQ) was 0.0020 mg kg-1 and other tested parameters (linearity, sensitivity, specificity, matrix effect, robustness, etc.) satisfied acceptance criteria. Stability assessment using spiked samples revealed the compounds were stable in raw and pasteurised milk for 4 weeks at -80 °C storage temperature. Maintaining samples at pH 8.5-9.0 further improved stability. Analysis of 516 milk samples from the field study found that NBPT and NBPTo concentrations were below the LOQ of 0.0020 mg kg-1, thus suggesting very low risk of residues occurring in the milk. The method developed is quick, robust, and sensitive. The method is deemed fit-for-purpose for the simultaneous determination of NBPT and NBPTo in milk. ispartof: MOLECULES vol:26 issue:10 ispartof: location:Switzerland status: published

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) emitted from agricultural soils and is influenced by nitrogen (N) fertiliser management and weather and soil conditions. Source partitioning N2O emissions related to management practices and soil conditions could suggest effective mitigation strategies. Multispecies swards can maintain herbage yields at reduced N fertiliser rates compared to grass monocultures and may reduce N losses to the wider environment. A restricted-simplex centroid experiment was used to measure daily N2O fluxes and associated isotopomers from eight experimental plots (7.8 m2) post a urea-N fertiliser application (40 kg N ha−1). Experimental pastures consisted of differing proportions of grass, legume and forage herb represented by perennial ryegrass (Lolium perenne), white clover (Trifolium repens) and ribwort plantain (Plantago lanceolata), respectively. N2O isotopomers were measured using a cavity ring down spectroscopy (CRDS) instrument adapted with a small sample isotope module (SSIM) for the analysis of gas samples ≤20 mL. Site preference (SP = δ15Nα – δ15Nβ) and δ15Nbulk ((δ15Nα + δ15Nβ) / 2) values were used to attribute N2O production to nitrification, denitrification or a mixture of both nitrification and denitrification over a range of soil WFPS (%). Daily N2O fluxes ranged from 8.26 to 86.86 g N2O-N ha−1 d−1. Overall, 34.2% of daily N2O fluxes were attributed to nitrification, 29.0% to denitrification and 36.8% to a mixture of both. A significant diversity effect of white clover and ribwort plantain on predicted SP and δ15Nbulk indicated that the inclusion of ribwort plantain may decrease N2O emission through biological nitrification inhibition under drier soil conditions (31%–75% WFPS). Likewise, a sharp decline in predicted SP indicates that increased white clover content could increase N2O emissions associated with denitrification under elevated soil moisture conditions (43%–77% WFPS). Biological nitrification inhibition from ribwort plantain inclusion in grassland swards and management of N fertiliser source and application timing to match soil moisture conditions could be useful N2O mitigation strategies. Teagasc University College Dublin

Nitrous oxide (N2O) is a potent greenhouse gas (GHG), with a global warming potential (GWP) of 265 relative to carbon dioxide (CO2) and a lifespan of over 100 years. Where N input from fertilizers exceeds plant demands, hotspots of N2O can be produced releasing short-lived pulses of N2O from the soil that exhibit disproportionately high rates of emissions relative to longer periods of time, known as hot moments. Hotspots and hot moments of N2O are sensitive to changes in agricultural management and the environment making it difficult to accurately quantify N2O emissions with low uncertainties. This study investigates the methods used to quantify N2O emissions in time and space, using both static chambers (SC) and eddy covariance (EC) techniques.N2O fluxes were measured from both techniques from an intensively managed grassland site under four fertilizer applications of calcium ammonium nitrate (CAN) in 2019. EC measurements of N2O were gap-filled by using a simple linear empirical model that incorporated environmental and management data. SC N2O fluxes were calculated using the arithmetic method and Bayesian statistics via Markov Chain Monte-Carlo (MCMC) simulations to account for the log-normal distribution of fluxes measured. N2O emissions were weakest in winter for both techniques (-3.27 µg N2O-N m-2 hr-1 for SC and -3.9 µg N2O-N m-2 hr-1 for EC). Following fertilizer application, daily averaged N2O emissions peaked in March (538.89 µg m-2 hr-1 for SC, 491.18 µg m-2 hr-1 for EC) and April (117.91 µg m-2 hr-1for SC and 306.90 µg m-2 hr-1 for EC). Delayed peaks in N2O emissions following fertilizer application occurred in June (101.03 µg m-2 hr-1 for SC and 814.76 µg m-2 hr-1 for EC) and October (417.14 µg m-2 hr-1 for SC and 313.22 µg m-2 hr-1 for EC) and these high emissions events coincided with dry periods followed by rainfall events. EC and SC measurements were most comparable when emissions were > 115 µg m-2 hr-1, when the flux footprint of half-hourly EC flux measurements overlapped with the position and time of SC measurements and when the number of chamber replicates were ≥ 15 on a given sampling day. Where the chamber sample size was small (n ≤ 5), the Bayesian method produced large uncertainties (> 25,000 µg m-2 hr-1) due to the inability to constrain an arithmetic mean from a log-normally distributed data set. Annual cumulative N2O fluxes from EC and SC by the arithmetic and Bayesian method, were 3.35(± 0.5) kg N ha-1, 2.98 (± 0.17) kg N ha-1and 3.13 (± 0.24) kg N ha-1 respectively. Emission factors from EC and SC by the arithmetic and Bayesian method were higher than the Intergovernmental Panel on Climate Change (IPCC) default value of 1%, at 1.46%, 1.30% and 1.36%, respectively. Our study highlights that disparities exist between SC and EC in quantifying N2O fluxes from a managed grassland and we recommend constraining disparities by utilizing a SC sample size > 5 and by accounting for the log-normal distribution of N2O flux data to accurately estimate N2O flux uncertainty.

Farm-to-fork quantitative microbial risk assessments (QMRA) typically start with a preliminary estimate of initial concentration (Cinitial) of microorganism loading at farm level, consisting of an initial estimate of prevalence (P) and the resulting pathogen levels in animal faeces. An average estimation of the initial concentration of pathogens can be achieved by combining P estimates in animal populations and the levels of pathogens in colonised animals' faeces and resulting cumulative levels in herd farmyard manure and slurry (FYM&S). In the present study, 14 years of data were collated and assessed using a Bayesian inference loop to assess the likely P of pathogens. In this regard, historical and current survey data exists on P estimates for a number of pathogens, including Cryptosporidium parvum, Mycobacterium avium subspecies paratuberculosis (MAP), Salmonella spp., Clostridium spp., Campylobacter spp., pathogenic E. coli, and Listeria monocytogenes in several species (cattle, pigs, and sheep) in Ireland. The results revealed that Cryptosporidium spp. has potentially the highest mean P (Pmean) (25.93%), followed by MAP (15.68%) and Campylobacter spp. (8.80%) for cattle. The Pmean of E. coli is highest (7.42%) in pigs, while the Pmean of Clostridium spp. in sheep was estimated to be 7.94%. Cinitial for Cryptosporidium spp., MAP., Salmonella spp., Clostridium spp., and Campylobacter spp. in cattle faeces were derived with an average of 2.69, 4.38, 4.24, 3.46, and 3.84 log10 MPN g -1, respectively. Average Cinitial of Cryptosporidium spp., Salmonella spp., Clostridium spp., and E. coli in pig slurry was estimated as 1.27, 3.12, 3.02, and 4.48 log10 MPN g -1, respectively. It was only possible to calculate the average Cinitial of Listeria monocytogenes in sheep manure as 1.86 log10 MPN g -1. This study creates a basis for future farm-to-fork risk assessment models to base initial pathogen loading values for animal faeces and enhance risk assessment efforts. ispartof: SCIENCE OF THE TOTAL ENVIRONMENT vol:786 ispartof: location:Netherlands status: published

RATIONALE N2 O isotopomers are a useful tool to study soil N cycling processes. The reliability of such measurements requires a consistent set of international N2 O isotope reference materials to improve inter-laboratory and inter-instrument comparability and avoid reporting inaccurate results. All these are the more important given the role of N2 O in anthropogenic climate change and the pressing need to develop our understanding of soil N cycling and N2 O emission to mitigate such emissions. Cavity ring-down spectroscopy (CRDS) could potentially overcome resource requirements and technical challenges, making N2 O isotopomer measurements more feasible and less expensive than previous approaches (e.g., gas chromatography [GC] and isotope ratio mass spectrometry [IRMS]). METHODS A combined laser spectrometer and small sample isotope module (CRDS & SSIM) method enabled N2 O concentration, δ15 Nbulk , δ15 Nα , δ15 Nβ and site preference (SP) measurements of sample volumes

In a field experiment, annual nitrous oxide (N

NA combined laser spectrometer and small sample isotope module (CRDSSSIM) method enabled NThe repeatability (mean ± 1σ; n = 10) of the CRDSSSIM measurements of the Ref Gas was 710.64 ppb (± 8.64), 2.82‰ (± 0.91), 5.41‰ (± 2.00), 0.23‰ (± 0.22) and 5.18‰ (± 2.18) for NCRDSSSIM is a promising approach that enables N

Anthelmintics are antiparasitic drugs used to control helminthic parasites such as nematodes and trematodes in animals, particularly those exposed through pasture-based production systems. Even though anthelmintics have been shown to be excreted into the environment in relatively high amounts as unmetabolized drug or transformation products (TPs), there is still only limited information available on their environmental occurrence, particularly in groundwater, which has resulted in them being considered as potential emerging contaminants of concern. A comprehensive study was carried out to investigate the occurrence of 40 anthelmintic residues (including 13 TPs) in groundwaters (and associated surface waters) throughout the Republic of Ireland. The study focused on investigating the occurrence of these contaminants in karst and fractured bedrock aquifers, with a total of 106 sites (88 groundwaters and 18 surface waters) samples during spring 2017. Seventeen anthelmintic compounds consisting of eight parent drugs and nine TPs were detected at 22% of sites at concentrations up to 41 ng L−1. Albendazole and its TPs were most frequently detected residues, found at 8% of groundwater sites and 28% of surface water sites. Multivariate statistical analysis identified several source and pathway factors as being significantly related to the occurrence of anthelmintics in groundwater, however there was an evident localised effect which requires further investigation. An investigation of the temporal variations in occurrence over a 13 month period indicated a higher frequency and concentration of anthelmintics during February/March and again later during August/September 2018, which coincided with periods of increased usage and intensive meteorological events. This work presents the first detections of these contaminants in Irish groundwater and it contributes to broadening our understanding of anthelmintics in the environment. It also provides insight to seasonal trends in occurrence, which is critical for assessing potential future effects and implications of climate change.

Nitrous oxide (N

Nitrous oxide (N2O) is a strong greenhouse gas produced by biotic/abiotic processes directly linked to both fungal and prokaryotic communities that produce, consume or create conditions leading to its emission. In soils exposed to nitrogen (N) in the form of urea, an ecological succession is triggered resulting in a dynamic turnover of microbial populations. However, knowledge of the mechanisms controlling this succession and the repercussions for N2O emissions remain incomplete. Here, we monitored N2O production and fungal/prokaryotic community changes (via 16S and 18S amplicon sequencing) in soil microcosms exposed to urea. Contributions of microbes to emissions were determined using biological inhibitors. Results confirmed that urea leads to shifts in microbial community assemblages by selecting for certain microbial groups (fast growers) as dictated through life history strategies. Urea reduced overall community diversity by conferring dominance to specific groups at different stages in the succession. The diversity lost under urea was recovered with inhibitor addition through the removal of groups that were actively growing under urea indicating that species replacement is mediated in part by competition. Results also identified fungi as significant contributors to N2O emissions, and demonstrate that dominant fungal populations are consistently replaced at different stages of the succession. These successions were affected by addition of inhibitors which resulted in strong decreases in N2O emissions, suggesting that fungal contributions to N2O emissions are larger than that of prokaryotes.

Microbial contamination of fresh produce is a major public health concern, with the number of associated disease outbreaks increasing in recent years. The consumption of sprouted beans and seeds is of particular concern, as these foodstuffs are generally consumed raw, and are produced in conditions favourable for the growth of zoonotic pathogens, if present in seeds prior to sprouting or in irrigation water. This work aimed to evaluate the activity of plasma activated water (PAW) as a disinfecting agent for alfalfa (Medicago sativa) and mung bean (Vigna radiata) seeds, during seed soaking. Each seed type was inoculated with Escherichia coli O157, E. coli O104, Listeria monocytogenes or Salmonella Montevideo, and treated with PAW for different times. A combination of PAW and ultrasound treatment was also evaluated. The germination and growth rate of both seeds were assessed after PAW treatments. PAW was demonstrated to have disinfecting ability on sprouted seeds, with reductions of up to Log10 1.67 cfu/g in alfalfa seeds inoculated with E. coli O104, and a reduction of Log10 1.76 cfu/g for mung bean seeds inoculated with E. coli O157 observed. The germination and growth rate of alfalfa and mung bean sprouts were not affected by the PAW treatments. The combination of a PAW treatment and ultrasound resulted in increased antimicrobial activity, with a reduction of Log10 3.48 cfu/g of S. Montevideo in mung bean seeds observed. These results demonstrate the potential for PAW to be used for the inactivation of pathogenic microorganisms which may be present on sprouted seeds and beans, thereby providing greater assurance of produce safety.

If pathogens are present in feedstock materials and survive in anaerobic digestion (AD) formulations at 37 &deg, C, they may also survive the AD process to be disseminated in digestate spread on farmland as a fertilizer. The aim of this study was to investigate the prevalence of Salmonella spp., Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium spp. in AD feed and output materials and survival/growth in four formulations based on food waste, bovine slurry and/or grease-trap waste using International Organization for Standardization (ISO) or equivalent methods. The latter was undertaken in 100 mL Ramboldi tubes, incubated at 37 &deg, C for 10 d with surviving cells enumerated periodically and the T90 values (time to achieve a 1 log reduction) calculated. The prevalence rates for Salmonella spp., Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium spp. were 3, 0, 5, 11 and 10/13 in food waste, 0, 0, 2, 3 and 2/3 in bovine slurry, 1, 0, 8, 7 and 8/8 in the mixing tank, 5, 1, 17, 18 and 17 /19 in raw digestate and 0, 0, 0, 2 and 2/2 in dried digestate, respectively. Depending on the formulation, T90 values ranged from 1.5 to 2.8 d, 1.6 to 2.8 d, 3.1 to 23.5 d, 2.2 to 6.6 d and 2.4 to 9.1 d for Salmonella Newport, Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium sporogenes, respectively. It was concluded that AD feed materials may be contaminated with a range of bacterial pathogens and L. monocytogenes may survive for extended periods in the test formulations incubated at 37 &deg, C.

Currently, nitrogen fertilizers are utilized to meet 48% of the total global food demand. The demand for nitrogen fertilizers is expected to grow as global populations continue to rise. The use of nitrogen fertilizers is associated with many negative environmental impacts and is a key source of greenhouse and harmful gas emissions. In recent years, urease and nitrification inhibitors have emerged as mitigation tools that are presently utilized in agriculture to prevent nitrogen losses and reduce greenhouse and harmful gas emissions that are associated with the use of nitrogen-based fertilizers. Both classes of inhibitor work by different mechanisms and have different physiochemical properties. Consequently, each class must be evaluated on its own merits. Although there are many benefits associated with the use of these inhibitors, little is known about their potential to enter the food chain, an event that may pose challenges to food safety. This phenomenon was highlighted when the nitrification inhibitor dicyandiamide was found as a residual contaminant in milk products in 2013. This comprehensive review aims to discuss the uses of inhibitor technologies in agriculture and their possible impacts on dairy product safety and quality, highlighting areas of concern with regards to the introduction of these inhibitor technologies into the dairy supply chain. Furthermore, this review discusses the benefits and challenges of inhibitor usage with a focus on EU regulations, as well as associated health concerns, chemical behavior, and analytical detection methods for these compounds within milk and environmental matrices.

Intensification of the food production system to meet increased global demand for food has led to veterinary pharmaceuticals becoming a critical component in animal husbandry. Anticoccidials are a group of veterinary products used to control coccidiosis in food-producing animals, with primary prophylactic use in poultry production. Excretion in manure and subsequent land-spreading provides a potential pathway to groundwater. Information on the fate and occurrence of these compounds in groundwater is scant, therefore these substances are potential emerging organic contaminants of concern. A study was carried out to investigate the occurrence of anticoccidial compounds in groundwater throughout the Republic of Ireland. Twenty-six anticoccidials (6 ionophores and 20 synthetic anticoccidials) were analysed at 109 sites (63 boreholes and 46 springs) during November and December 2018. Sites were categorised and selected based on the following source and pathway factors: (a) the presence/absence of poultry activity (b) predominant aquifer category and (c) predominant groundwater vulnerability, within the zone of contribution (ZOC) for each site. Seven anticoccidials, including four ionophores (lasalocid, monensin, narasin and salinomycin) and three synthetic anticoccidials (amprolium, diclazuril and nicarbazin), were detected at 24% of sites at concentrations ranging from 1 to 386 ng L−1. Monensin and amprolium were the two most frequently detected compounds, detected at 15% and 7% of sites, respectively. Multivariate statistical analysis has shown that source factors are the most significant drivers of the occurrence of anticoccidials, with no definitive relationships between occurrence and pathway factors. The study found that the detection of anticoccidial compounds is 6.5 times more likely when poultry activity is present within the ZOC of a sampling point, compared to the absence of poultry activity. This work presents the first detections of these contaminants in Irish groundwater and it contributes to broadening our understanding of the environmental occurrence and fate of anticoccidial veterinary products.

Nitrous oxide (N2O) is a potent greenhouse gas associated with nitrogen fertiliser inputs to agricultural production systems. Minimising N2O emissions is important to improving the efficiency and sustainability of grassland agriculture. Multispecies grassland swards composed of plants from different functional groups (grasses, legumes, herbs) have been considered as a management strategy to achieve this goal. Numerous soil nitrogen transformation pathways can lead to the production of N2O emissions. These transformation pathways are regulated by soil microbial communities and the environmental conditions and management practices that impact on them. Much research has been carried out on N cycling and N2O emissions from predominantly grass monoculture systems. However, there is a lot yet to understand about how agricultural grasslands with diverse plant communities influence soil N cycling and N2O emissions. A lysimeter experiment was set up as a completely randomised block design and carried out over a full year to investigate N2O production, and nitrogen cycling associated with four sward types. The swards four swards were: perennial ryegrass (PRG, Lolium perenne); PRG and low white clover (PRG + LWC, Trifolium repens); PRG and high white clover (PRG + HWC); PRG, WC and ribwort plantain (PRG + WC + PLAN, Plantago lanceolata) managed at 250, 90, 0, and 45 kg N ha-1yr-1, respectively. Fertiliser N was applied by syringe as urea in splits at suitable timings to meet grass growth demands. N2O fluxes were measured using a static chamber technique and additional samples were taken after the final flux sample to measure the associated N2O isotopomers using a novel Cavity Ring Down Spectroscopy technique. Leachate volumes were measured on a weekly basis and composite monthly samples were used to determine the total amount of N leached from each treatment over the full year. Herbage was harvested on a monthly basis to measure DM yield (kg DM ha-1), total N (%) and N yield (kg N ha-1).This work reports on the N2O emissions and N leaching associated with the four sward treatments and related these N losses to the treatments DM yields and N uptake as an estimation of the efficiency of these differing grassland management strategies. N2O isotopomer measurements were used to indicate N transformation pathways driving N loss over the growing season particularly around periods of peak N2O emissions.

peer-reviewed Cattle excreta deposited on grazed pastures are responsible for one fifth of the global anthropogenic nitrous oxide (N2O) emissions. One of the key nitrogen (N) sources is urine deposited from grazing animals, which contributes to very large N loadings within small areas. The main objective of this plot study was to establish whether the application of N fertiliser and urine deposit from dairy cows synergistically interacts and thereby increases N2O emissions, and how such interaction is influenced by the timing of application. The combined application of fertiliser (calcium ammonium nitrate) and urine significantly increased the cumulative N2O emissions as well as the N2O emission factor (EF) from 0.35 to 0.74 % in spring and from 0.26 to 0.52 % in summer. By contrast, EFs were lower when only fertiliser (0.31 % in spring, 0.07 % in summer) or urine was applied (0.33 % in spring, 0.28 % in summer). In autumn, N2O emissions were larger than in other seasons and the emissions from the combined application were not statistically different to those from either the separately applied urine or N fertiliser (EF ranging from 0.72 to 0.83, p-value < 0.05). The absence of significant synergistic effect could be explained by weather conditions, particularly rainfall during the three days prior to and after application in autumn. This study implies that the interactive effects of N fertilisation and urine deposit, as well as the timing of the application on N2O emission need to be taken into account in greenhouse gas emission inventories. Funding for this work was supported by the Walsh fellowship program at Teagasc, Ireland (fellowship number 2014079) and under the project Manipulation and Integration of Nitrogen Emissions (MINE). This research was also financially supported under the National Development Plan, through the Research Stimulus Fund, administered by the Department of Agriculture, Food and the Marine (grant number 15S655).

Increased global demand for dairy produce and the abolition of EU milk quotas have resulted in expansion in dairy production across Europe and particularly in Ireland. Simultaneously, there is increasing pressure to reduce the impact of nitrogen (N) losses to air and groundwater on the environment. In order to develop grassland management strategies for grazing systems that meet environmental targets and are economically sustainable, it is imperative that individual mitigation measures for N efficiency are assessed at farm system level. To this end, we developed an excel-based N flow model simulating an Irish grass-based dairy farm, to evaluate the effect of farm management on N efficiency, N losses, production and economic performance. The model was applied to assess the effect of different strategies to achieve the increased production goals on N utilization, N loss pathways and economic performance at farm level. The three strategies investigated included increased milk production through increased grass production, through increased concentrate feeding and by applying a high profit grass-based system. Additionally, three mitigation measures; low ammonia emission slurry application, the use of urease and nitrification inhibitors and the combination of both were applied to the three strategies. Absolute N emissions were higher for all intensification scenarios (up to 124 kg N ha−1) compared to the baseline (80 kg N ha−1) due to increased animal numbers and higher feed and/or fertiliser inputs. However, some intensification strategies showed the potential to reduce the emissions per ton milk produced for some of the N-loss pathways. The model showed that the assessed mitigation measures can play an important role in ameliorating the increased emissions associated with intensification, but may not be adequate to entirely offset absolute increases. Further improvements in farm N use efficiency and alternatives to mineral fertilisers will be required to decouple production from reactive N emissions.

Where nitrogen input from fertilizer application exceeds plant demands, hotspots of microbially produced nitrous oxide (N 2 O) can exhibit disproportionately high rates of emissions relative to longer periods of time, known as hot moments. Hotspots and hot moments of N2O are sensitive to changes in agricultural management and weather, making it difficult to accurately quantify N 2 O emissions. This study investigates the spatial and temporal variability of N2O emissions using both static chambers (CH) and eddy covariance (EC) techniques, measured at a grassland site subject to four fertilizer applications of calcium ammonium nitrate (CAN) in 2019. Daily mean CH emissions were calculated using the arithmetic method and Bayesian statistics to explicitly account for the log-normal distribution of the dataset. N2O fluxes measured by CH and EC were most comparable when flux measurements were > 115 N 2 O N µg m − 2 hr −1, and EC and CH measurements showed spatial and temporal alignment when CH n ≥ 15. Where n ≤ 5, the Bayesian method produced large uncertainties due to the difficulty of fitting an arithmetic mean from a log-normally distributed data set with few flux measurements. Annual EC fluxes, gap-filled using a multi-variate linear model, showed a strong correlation with measured flux values (R 2 = 0.92). Annual cumulative fluxes by EC were higher (3.35 [± 0.5] kg N ha−1) than CH using the arithmetic (2.98 [± 0.17] kg N ha−1 ) and Bayesian method (3.13 [± 0.24] kg N ha−1), which quantified emission factors of 1.46%, 1.30% and 1.36%, respectively. This study implies that a large sample size and frequent CH flux measurements are necessary for comparison with EC fluxes and that Bayesian statistics are an appropriate method for estimating realistic means and ranges of uncertainty for CH flux data sets.

Increased emissions of N2O, a potent greenhouse gas (GHG), from agricultural soils is a major concern for the sustainability of grassland agriculture. Emissions of N2O are closely associated with the rates and forms of N fertilisers applied as well as prevailing weather and soil conditions. Evidence suggests that multispecies swards require less fertiliser N input, and may cycle N differently, thus reducing N loss to the environment. This study used a restricted simplex-centroid experimental design to investigate N2O emissions and soil N cycling following application of urea-N (40 kg N ha−1) to eight experimental swards (7.8 m2) with differing proportions of three plant functional groups (grass, legume, herb) represented by perennial ryegrass (PRG, Lolium perenne), white clover (WC, Trifolium repens) and ribwort plantain (PLAN, Plantago lanceolata), respectively. Swards were maintained under two contrasting soil moisture conditions to examine the balance between nitrification and denitrification. Two N2O peaks coincided with fertiliser application and heavy rainfall events; 13.4 and 17.7 g N2O-N ha−1 day−1 (ambient soil moisture) and 39.8 and 86.9 g N2O-N ha−1 day−1 (wet soil moisture). Overall, cumulative N2O emissions post-fertiliser application were higher under wet soil conditions. Increasing legume (WC) proportions from 0% to 60% in multispecies swards resulted in model predicted N2O emissions increasing from 22.3 to 96.2 g N2O-N ha−1 (ambient soil conditions) and from 59.0 to 219.3 g N2O-N ha−1 (wet soil conditions), after a uniform N application rate. Soil N dynamics support denitrification as the dominant source of N2O especially under wet soil conditions. Significant interactions of PRG or WC with PLAN on soil mineral N concentrations indicated that multispecies swards containing PLAN potentially inhibit nitrification and could be a useful mitigation strategy for N loss to the environment from grassland agriculture. Department of Agriculture, Food and the Marine Teagasc University College Dublin

Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic matter draining from soils, plays a significant role in soil C cycling and in nutrient and pollutant transport. DOM from undisturbed soil profiles has rarely been studied. Hydrophobic acids (Ho) and hydrophilic acids (Hi), the major components of DOM, were recovered, using XAD-8 and XAD-4 resins in series, from waters draining in winter and in spring periods from well-drained and poorly drained Irish grassland soil profiles in lysimeters. Waters were collected from 45 soil undisturbed lysimeters at the Teagasc Research Centre, Johnstown Castle, Wexford, Ireland. Four Irish representative soils had been collected as undisturbed 1.0-m-deep monoliths, transported to the experiment site and arranged randomly in an experimental facility. Water collections were carried out in winter and spring periods. The DOM was isolated and fractionated using an XAD-8 and XAD-4 resins in-tandem procedure, and hydrophobic acids (Ho) and hydrophilic acids (Hi) were isolated. The amounts of DOM recovered in the winter period were much greater than those in the spring period, and the soil types had only minor influences on the DOM concentrations recovered. The Ho and Hi fraction contents ranged from 62 to 90 and 10 to 28%, respectively, of the total DOM content extracted. The Hi acids were most enriched in 13C, and considered to reflect greater microbial inputs. The neutral sugar (NS) contents for the Ho and Hi fractions were in the range of 15 to 52 μg mg−1, with the Hi fraction most enriched. The amino acids (AAs) for the Ho and Hi fractions varied from 0.6 to 2.4%, and the total AAs and NS of the Ho acids were well correlated. The DOM fractions from the drainage waters contained much less AAs and NS than the corresponding fractions in the parent soils. The solid- and liquid-state NMR data indicated organic structures with low aromaticity, significant amounts of carbohydrate and with lesser amounts of peptide structures, and with long-chain methylene (CH2)n and methine (-CH-) groups. The application of a variety of wet chemistry and of spectroscopy procedures has given a more in-depth awareness of the compositions of the DOM in the drainage waters from four different soils in 1.0-m-deep lysimeter arrangements. Based on wet chemistry analyses, and FTIR and liquid- and solid-state NMR spectrometry, it is clear that there are some differences between the compositions of the DOM fractions recovered. Alkyl functionalities dominated the structures. These included significant amounts or O-alkyl (predominantly carbohydrate), and with lesser (and variable amounts in the different fractions) aromatic structures (to which aromatic amino acid components were considered to be significant contributors), and with no evidence for lignin-derived structures The results suggest that, during residence in the soil solution, microbiological processes transform the SOM components released into products that are greatly different from their materials of origin in the SOM.

Nitrate (NO3−) leaching and nitrous oxide (N2O) emission from urine patches in grazed pastures are key sources of water and air pollution, respectively. Broadcast spraying of the nitrification inhibitor dicyandiamide (DCD) has been shown to reduce these losses, but it is expensive. As an alternative, it had been demonstrated that feeding DCD to cattle (after manual mixing with supplementary feeds) was a practical, effective and cheaper method to deliver high DCD rates within urine patches. This two-year study carried out on simulated urine patches in three application seasons (spring, summer, autumn) explored the efficacy of DCD feeding to cattle to reduce N losses from grazed pasture soil in a heavy-textured soil under temperate climatic conditions. In each application season, DCD fed to cows, then excreted with urine and applied at a rate of 30 kg DCD ha− 1 (treatment U + DCD30-f) was as effective as powdered DCD mixed with normal urine and applied at the same rate (treatment U + DCD30) at reducing cumulative N2O-N emissions and the N2O-N emission factor (EF3, expressed as % of N applied). Increasing DCD loading within urine patches from 10 to 30 kg DCD ha− 1 improved efficacy by significantly reducing the EF3 from 34% to 64%, which highlights that under local conditions, 10 kg DCD ha− 1 (the recommended rate for commercial use in New Zealand) was not the optimum DCD rate to curb N2O emissions. The modelling of EF3 in this study also suggests that N mitigation should be given more attention when soil moisture is going to be high, which can be predicted with short-term weather forecasting. DCD feeding, for instance in autumn when cows are not lactating and the risk of N losses is high, could then be reduced by focusing mainly on those forecasted wet periods.

Soil N2O emission potential is commonly investigated under idealized denitrifying conditions (e.g. nitrate-N supplied and anaerobic soil), with pH commonly identified as a major determinant of N2O emission potential. However, under urine patch conditions in grazed pastures soils a more complex series of abiotic and biotic factors may influence emissions due to the complex N transformations that occur following urea hydrolysis. These transformations may decouple native and/or expected controls of N2O emissions encountered under classic denitrifying conditions. Here, we tracked O2, CO2, NO, N2O and N2 emissions from urine amended soils (i.e. simulating a urine patch) to determine putative controls of N2O emissions within 13 different pasture soils from northern (Ireland) and southern hemispheres (New Zealand). Incubations were performed under aerobic conditions±artificial urine (13.3 mg N vial−1) equivalent to field ruminant urine deposition rates of 1000 kg N ha−1. Results revealed that pH was not an important regulator of the emission ratio (N2O/(NO + N2O + N2)) in urine amended soils. Within urine affected soils, a new set of variables emerged as regulators of N2O emissions, likely due to the unique environment created within this system. We show that urine results in decoupling of the initial soil pH control of the emission ratio allowing other regulators such as nitrite to dominate. In addition, we observed that the emission ratio of N2O increased linearly with the rate of N- gas loss (NO + N2O + N2 μmol N h−1), O2 consumption was positively associated with ammonia oxidising bacteria (AOB) and that the production of NO and N2O were also enhanced under urine conditions.

Farmyard manure and slurry (FYM&S) is a valuable feedstock for anaerobic digestion (AD) plants. However, FYM&S may contain high concentrations of pathogens, and complete inactivation through the AD process is unlikely. Thus, following land application of digestate, pathogens may contaminate a range of environmental media posing a potential threat to public health. The present study aimed to combine primary laboratory data with literature-based secondary data to develop an Excel-based exposure assessment model (ADRISK) using a gamma generalised linear model to predict the final microorganism count in the digestate. This research examines the behaviour of a suite of pathogens (Cryptosporidium parvum, norovirus, Mycobacterium spp., Salmonella spp., Listeria monocytogenes, Clostridium spp., and pathogenic Escherichia coli) and indicators (total coliforms, E. coli, and enterococci) during mesophilic anaerobic digestion (M-AD) at 37 °C, pre/post-AD pasteurisation, and after a period of storage (with/without lime) for different feedstock proportions (slurry:food waste: 0:1, 1:3, 2:1, and 3:1). ADRISK tool simulations of faecal indicator bacteria levels across all scenarios show that the digestate can meet the EU standard without pasteurisation if the AD runs at 37 °C or a higher temperature with a higher C:N ratio (recipe 3) and a hydraulic retention time ≥ 7 days. The storage of digestate also reduced levels of microorganisms in the digestate. The Irish pasteurisation process (60 °C for 4 days), although more energy-intensive, is more effective than the EU pasteurisation (70 °C for 1 h) specification. Pre-AD pasteurisation was more effective for C. parvum, norovirus, Mycobacterium thermoresistibile. However, post-AD literature-based pasteurisation is most likely to assure the safety of the digestate. The information generated from this model can inform policy-makers regarding the optimal M-AD process parameters necessary to maximise the inactivation of microorganisms, ensuring adverse environmental impact is minimised, and public health is protected. ispartof: SCIENCE OF THE TOTAL ENVIRONMENT vol:800 ispartof: location:Netherlands status: published

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

Animal urine patches, particularly bovine, are the major source of gaseous and leaching losses of nitrogen (N) in livestock-grazed pastoral systems. One method of mitigating these losses is the application of N inhibitors to patches that slow down the N transformations, thus allowing more time for plant uptake. If inhibitors can be applied as spot-treatments, then the overall volume of chemical can be minimized without compromising inhibitor efficacy. To enable this, accurate and reliable methods of detecting patches within hours of deposition are required. In this study, we aimed to validate the output of the newly developed and modified instrument ‘Spikey-R’ for detecting and mapping urine patches via measurement of soil surface electrical conductivity with the aim of using these data for targeting in-situ spot treatment of detected patches. We compared measurements from Spikey-R against thermal imagery from a handheld camera taken during urine deposition, as well as imagery taken from a remotely piloted aircraft system (RPAS or ‘drone’) 2 weeks after deposition. Wetted areas, as a result of urine application, across all sites were 0.2–0.3 m2 (1 L urine), 0.3–0.5 m2 (2 L), and 0.3–0.8 m2 (3 L). Spikey-R data generally compared well with the reference map produced from the thermal imagery, with slightly larger mean patch areas that still fell within the bounds of uncertainty. Repeat Spikey-R runs over the same patches showed no significant difference in detected areas up to 48 h after application. The drone was successful in detecting most urine patches 14 days post-application and identified a much larger pasture response (average > 150% larger again) than the initial wetted area with sizes ranging from 0.4 to 0.7 m2 (1 L), to 0.5 to 1.1 m2 (2 L), to 0.5 to 1.5 m2 (3 L). Spikey-R proved to be an effective tool in a research setting; advantages and disadvantages of each technology are discussed in detail.