Urine Application Research Articles

Plant species identity surpasses species richness as a key driver of N2O emissions from grassland

Grassland ecosystems worldwide not only provide many important ecosystem services but they also function as a major source of the greenhouse gas nitrous oxide (N2O), especially in response to nitrogen deposition by grazing animals. To explore the role of plants as mediators of these emissions, we tested whether and how N2O emissions are dependent on grass species richness and/or specific grass species composition in the absence and presence of urine deposition. We hypothesized that: (i) N2O emissions relate negatively to plant productivity; (ii) four-species mixtures have lower emissions than monocultures (as they are expected to be more productive); (iii) emissions are lowest in combinations of species with diverging root morphology and high root biomass; and (iv) the identity of the key species that reduce N2O emissions is dependent on urine deposition. We established monocultures and two- and four-species mixtures of common grass species with diverging functional traits: Lolium perenne L. (Lp), Festuca arundinacea Schreb. (Fa), Phleum pratense L. (Php) and Poa trivialis L. (Pt), and quantified N2O emissions for 42 days. We found no relation between plant species richness and N2O emissions. However, N2O emissions were significantly reduced in specific plant species combinations. In the absence of urine, plant communities of Fa+Php acted as a sink for N2O, whereas the monocultures of these species constituted a N2O source. With urine application Lp+Pt plant communities reduced (P < 0.001) N2O emissions by 44% compared to monocultures of Lp. Reductions in N2O emissions by species mixtures could be explained by total biomass productivity and by complementarity in root morphology. This study shows that plant species composition is a key component underlying N2O emissions from grassland ecosystems. Selection of specific grass species combinations in the context of the expected nitrogen deposition regimes may therefore provide a key for mitigation of N2O emissions.

Nitrous oxide emission factors for urine and dung patches in a subtropical Brazilian pastureland

Cattle urine and dung (faeces) patches are nitrous oxide (N2O) sources in pasturelands with impacts in the global N2O budget, but specific information about those emissions are still missing for Brazilian subtropical and tropical regions. We conducted a sequence of 3 field-trials (summer, winter and spring, 90 days each) to evaluate the N2O emission and emission factor (EF) after the deposition of 3 volumes of cattle urine or 3 weights of dung (½, 1 and 1½ time the mean urination volume or defecation weight of Friesian cows) on a free-drained Cambisol of a subtropical pastureland of Brazil. The N2O emission peaks (3198μgN2O-Nm−2h−1 after urine in summer was the highest) occurred on average 17±9 days after application (DAA), both for urine and dung, and dropped to the background levels 41±10 DAA of urine and 49±10 DAA of dung. The highest contents of NH4+-N in soil (200–250mgNkg−1) occurred one day after urine application and 10–14 days later for dung (100–200mgNkg−1). Nitrate peaks occurred from 23 to 26 DAA in urine patches (∼40–50mgNkg−1) and 19–50 DAA in dung patches (∼40–50mgNkg−1). The N2O emission peaks for urine coincided with soil NH4+-N peak in winter but with soil NO3−-N peak in spring. For dung, the emission peak seemed to be more associated with soil NO3−-N than to NH4+-N, either in winter or spring (inorganic-N was not assessed in summer). It was not possible to conclude whether nitrification or denitrification was the dominant process in N2O production, but it seemed that both played relevant roles. The EF for urine, averaged across the seasons, diminished with increments in urine volume, from 0.33% in ½ volume to 0.19% in 1½ volume, possibly because urine percolated deeper into the soil and proportionally less N remained available for N2O production in the top layer. The EF for dung was 0.19%, 0.12% and 0.14% for ½, 1 and 1½ weight, respectively, showing no clear trend with increment in dung weight. The lowest EFs for urine and dung occurred in winter, possibly because of lowest temperatures and soil water-filled pore space. The average EF for dung (0.15%) was lower than that of urine (0.26%), because urea-N of urine is more readily available for the hydrolysis than organic N forms of dung. This result suggests that these two excreta should be addressed separately in national greenhouse gases inventories or communications. Our results suggest that the default 2% EF proposed in IPCC Guidelines for cattle excreta are overestimated for subtropical Brazil.

Comparative effect of human urine and ammonium nitrate application on maize (Zea mays L.) grown under various salt (NaCl) concentrations

AbstractThe present study investigates the effect of urine and ammonium nitrate on maize (Zea mays L.) vegetative growth, leaf nutrient concentration, soil electrical conductivity, and exchangeable‐cations contents under various concentrations of NaCl in a soil substrate. The experiment was arranged in a completely randomized block design with eight replications under greenhouse conditions. The experimental soil substrate was made from a 1 : 1 : 1 volume‐ratio mixture of compost, quartz sand, and silty‐loam soil. Salinity was induced by adding 0, 15, and 30 mL of 1 M NaCl solution per kg of substrate to achieve an electrical conductivity (EC) of 1.3 (S0), 4.6 (S1), and 7.6 (S2) dS m–1. Nitrogen sources were urine and ammonium nitrate applied at 180 and 360 mg N (kg soil substrate)–1. Basal P and K were added as mono potassium phosphate in amounts equivalent to 39 mg P and 47 mg K (kg substrate)–1, respectively. In the S0 treatment, a 3‐fold increase in EC was measured after urine application compared to an insignificant change in ammonium nitrate–fertilized substrates 62 d after sowing. Under saline conditions, application of 360 mg N (kg soil)–1 as urine significantly decreased soil pH and maize shoot dry weight. At the highest salt and N dose (S2, N360) 50% of urine‐fertilized plants died. Regardless of salinity there was no significant difference between the two fertilizers for investigated growth factors when N was supplied at 180 mg (kg soil)–1. Leaf N and Ca contents were higher after urine application than in ammonium nitrate–fertilized plants. At an application rate of 180 mg N (kg soil)–1, urine was a suitable fertilizer for maize under saline conditions. Higher urine‐N dosages and/or soil salinity exceeding 7.6 dS m–1 may have a deleterious effect on maize growth.

Effects of a urease inhibitor and aluminium chloride alone or combined with a nitrification inhibitor on gaseous N emissions following soil application of cattle urine

Addition to soil of separated cattle-urine obtained from housing with urine-faeces segregation systems is an important source of gaseous nitrogen (N) emissions. This study aimed to evaluate the effect of adding different concentrations of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and aluminium chloride (AlCl 3 ), alone or combined with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), on gaseous N losses and N transformations in soil amended with cattle-urine. Using laboratory incubations soil was amended with cattle-urine (200 kg total N ha −1 ) containing NBPT (0.1 or 1.0%) or AlCl 3 (0.5 or 1.0%) either as a single additive or combined with 0.5% DMPP. Three additional treatments were included: soil only (Control), soil amended only with cattle-urine and soil amended with cattle-urine and DMPP. The addition of NBPT at 1% significantly delayed urea hydrolysis during the first 4-d after urine application comparatively to treatments receiving AlCl 3 . Nitrification was inhibited by addition of DMPP, with no further effect ( P > 0.05) when DMPP was combined with NBPT or AlCl 3 . The AlCl 3 treatment had no effect on urea hydrolysis or nitrification. The combination of DMPP with NBPT or AlCl 3 increased ( P < 0.05) NH 3 emissions and reduced ( P < 0.05) NO and N 2 O emissions compared with urine alone. It was concluded that NBPT was more effective at reducing gaseous N emissions from cattle-urine applications than AlCl 3 , and that NBPT alone was more effective than NBPT combined with DMPP. No advantages were gained from the combination of one of these additives with DMPP on total gaseous N emissions. • The effects of NBPT or AlCl 3 alone or combined with DMPP on emissions were evaluated. • DMPP with either NBPT or AlCl 3 had the same effect on nitrification as DMPP alone. • Increasing the concentration of NBPT or AlCl 3 did not significantly reduce gaseous N emissions. • DMPP with either NBPT or AlCl 3 increased NH 3 emissions and reduced NO and N 2 O emissions. • NBPT, with or without DMPP, was more effective at reducing gaseous N emissions than AlCl 3 .

Effects of nitrogen application rate and a nitrification inhibitor dicyandiamide on methanotroph abundance and methane uptake in a grazed pasture soil

Methane-oxidizing bacteria (methanotrophs) in the soil are a unique group of methylotrophic bacteria that utilize methane (CH4) as their sole source of carbon and energy which limit the flux of methane to the atmosphere from soils and consume atmospheric methane. A field experiment was conducted to determine the effect of nitrogen application rates and the nitrification inhibitor dicyandiamide (DCD) on the abundance of methanotrophs and on methane flux in a grazed pasture soil. Nitrogen (N) was applied at four different rates, with urea applied at 50 and 100 kg N ha(-1) and animal urine at 300 and 600 kg N ha(-1). DCD was applied at 10 kg ha(-1). The results showed that both the DNA and selected mRNA copy numbers of the methanotroph pmoA gene were not affected by the application of urea, urine or DCD. The methanotroph DNA and mRNA pmoA gene copy numbers were low in this soil, below 7.13 × 10(3) g(-1) soil and 3.75 × 10(3) μg(-1) RNA, respectively. Daily CH4 flux varied slightly among different treatments during the experimental period, ranging from -12.89 g CH4 ha(-1) day(-1) to -0.83 g CH4 ha(-1) day(-1), but no significant treatment effect was found. This study suggests that the application of urea fertilizer, animal urine returns and the use of the nitrification inhibitor DCD do not significantly affect soil methanotroph abundance or daily CH4 fluxes in grazed grassland soils.

Influence of soil bulk density and matric potential on microbial dynamics, inorganic N transformations, N2O and N2 fluxes following urea deposition

Transformation of ruminant urine-nitrogen (N) can contribute to negative environmental outcomes such as nitrate leaching which leads to eutrophication of waterways and production of nitrous oxide (N2O), a greenhouse gas. Although abiotic factors influencing urine-N processing have been well studied, detailed studies of the soil microbial community dynamics following urine application are required to improve mitigation strategies for reducing harmful N fluxes from urine deposition. A factorial laboratory experiment using packed silt-loam soil cores with two levels each of urea (±), soil matric potential (ψ −6.0 or −0.2 kPa) and soil bulk density (ρb 1.1 or 1.5 g cm−3) was performed to study the interaction of urea and soil physical conditions on both soil inorganic N transformations and the abundance of ammonia-oxidizers and denitrifiers. Soil ψ and ρb treatments had an immediate impact on soil pH, dissolved organic carbon, inorganic N pools and emissions of N2O and N2 following urea deposition, and microorganisms carrying the nosZ gene were present in lower numbers in the most aerobic soil (−6.0 kPa and 1.1 g cm−3) from day 7. In all treatments, both bacterial amoA and denitrifier nirS, nirK and nosZ gene copy numbers increased within 1 day following urea application. Dynamics in the NH4+ concentrations were significantly correlated with cumulative changes in the abundance of the ammonia-oxidizers, but no relation was found between cumulative changes in the denitrifier nirS, nirK and nosZ gene copy numbers and the dynamics in soil inorganic N, N2O or N2 emissions. Throughout most of the study period the specific soil conditions, induced by the ψ and ρb treatments, determined nitrifier and denitrifier activity rather than the size of the microbial communities involved. However, by day 35 soil ψ and ρb treatments exerted large treatment effects on bacterial amoA, nirS and nirK gene copy numbers. Thus, although nitrate concentrations and N2O emissions following urea deposition were determined by the soil ψ and ρb conditions in the short-term, our results indicate that changes in the population sizes of denitrifiers and AOB in ruminant urine patches may influence environmental N fluxes in the long-term.

Do We Need High-Resolution MS in Forensic and Clinical Toxicology?

Department of Experimental & Clinical Toxicology, Institute of Experimental & Clinical Pharmacology & Toxicology, Saarland University, D-66421 Homburg, Germany E-mail: markus.meyer@uks.eu It is my current opinion that high-resolution MS (HRMS) is not a must in clinical and forensic toxicology, but is ‘nice-to-have’. I see this technique as a wonderful, complementary tool to facilitate the daily work of a toxicologist. In various publications, HRMS has been proven to be a helpful tool in drug metabolism studies, laying the foundation for screening applications in human urine and/or plasma samples required in toxicological analysis. Furthermore, highly sensitive quantification procedures are possible allowing very low detection limits in combination with fast and easy sample preparation. Despite the usefulness of HRMS, one should always think about the high costs, especially in contrast with well-established techniques such as GC–MS or even LC–MS/MS. I do not only mean the costs for purchasing the instrument, but also the running costs, which are much higher than for LC low-resolution MS. If using LC coupled to HRMS, you need very clean mobile phases and special calibration solutions, and in order to avoid contaminations or carryover extensive cleaning steps are necessary. Furthermore, teething troubles when using new developments should be considered when s tarting with HRMS.

Using the Receptivity model to uncover ‘urine blindness’: perceptions on the re-use of urine

Population growth, climatic changes and over-exploitation of natural resources are at the basis of the world's food crisis, which counts almost one million people without sufficient food sustenance. These changes require novel environmental practices which are based on nutrient recovery and management in agriculture. This contribution analyses and discusses users' perceptions on re-use of urine as fertilizer through the lenses of the Receptivity model. A search was performed on Scopus (as well as other web search engines) using the keywords: urine, nutrient recovery and sanitation. Results shows how questions related to awareness, association, acquisition and application of the environmental change can represent hurdles to novel models of nutrient recovery and the use of urine in agriculture. Examples of hurdles identified from the literature relate to poor understanding of potential for urine reuse, social stigma attached to using dry sanitation and applying urine in agriculture and poor operational knowledge of application of urine in agriculture. Conclusion relates to the illustration of implications of such challenges on the design of environmental interventions.

Excreta Deposition on Grassland Patches. II. Spatial Pattern and Duration of Forage Responses

ABSTRACTForage dry matter harvested (DMH) and nutritive value (NV) are affected by livestock excreta. Efforts to model nutrient cycling in grazed grasslands would benefit from increased understanding of the duration and spatial pattern of excreta effects on grassland patches. These responses were measured on ‘Pensacola’ bahiagrass (Paspalum notatum Flüggé) swards treated with two excreta types (dung and urine) from two excreta source pastures (Average and High management intensities based on N fertilizer and stocking rates) applied at four frequencies (0, 1, 2, 3 per year) during 2 yr. Forage DMH under dung pats decreased, but DMH surrounding the pat was not affected by application frequency. Suppression of DMH by dung was ≥112 d and extent of suppression increased as application frequency increased. In contrast, DMH under urine increased linearly (2950 to 6250 kg ha−1 for the Average management intensity and 3480 to 6450 kg ha−1 for the High management intensity) as application frequency increased and effects were observed 15 cm beyond the deposit's edge. Forage NV was not affected by dung, but it increased with increasing urine application frequency and for distances up to 30 cm from the edge of the urine deposit. Urine increased DMH for ≥84 d and increased crude protein for ≥28 d following a single urine application and ≥84 d after multiple applications. Data show that duration and spatial patterns of forage response to dung and urine differ, but effects of both can be long lived and are increased by multiple deposits to a patch.

Excreta Deposition on Grassland Patches. I. Forage Harvested, Nutritive Value, and Nitrogen Recovery

ABSTRACTLivestock excreta deposition in grazed grassland is nonuniform and concentrated around shade, water, and supplement feeding locations. The consequences of repeated dung or urine deposition to grassland patches have not been well quantified in terms of effects on forage dry matter harvested (DMH), forage nutritive value, and nutrient recovery. These responses were measured on ‘Pensacola’ bahiagrass (Paspalum notatum Flüggé) swards treated with two excreta types (dung and urine) from two excreta source pastures (the Average and High management intensities based on N fertilizer and stocking rates) applied at four frequencies (0, 1, 2, 3 yr−1) during 2 yr. Responses were measured within a circular quadrat of radius 45 cm whose center was the midpoint of the excreta deposit. Forage DMH decreased linearly from 3040 to 2800 kg ha−1 with increasing dung application frequency and increased from 3040 to 4820 kg ha−1 as urine application frequency increased. Forage nutritive value did not differ among dung application frequencies but generally increased with urine application frequency. Nitrogen recovery relative to an untreated control was negative for dung, positive for urine, and decreased with increasing urine application frequency. Forage DMH was suppressed by dung, but urine increased forage DMH, nutritive value, and nutrient removal. Decreasing nutrient recovery with increasing excreta application frequency supports use of grazing strategies that increase uniformity of deposition.

Impact of short-interval, repeat application of dicyandiamide on soil N transformation in urine patches

In pastoral farming systems, bovine urine patches are ‘hot-spots’ of elevated soil nitrogen (N). Nitrification in urine patches is linked to deleterious environmental outcomes, such as formation of the greenhouse gas nitrous oxide (N2O). The nitrification inhibitor dicyandiamide (DCD) reduces the rate of nitrification in soils subsequently limiting N-losses. Dicyandiamide's bacteriostatic mode of inhibiting ammonia oxidising bacteria (AOB), has raised concerns about the efficacy of frequent DCD use. For example, frequent use could result in selection for a DCD-tolerant AOB community. Furthermore, the impacts of DCD on other aspects of microbial N transformation in soil are largely unknown. To test the influence of short-term repeat application of DCD on soil N cycling, we established a replicated field-trial in which ±urine and ±DCD were added to pasture soils (fully crossed, 2×2 factorial design). After 57 d, treatments were re-applied. Mineral N pools, pH, DCD concentration, moisture and temperature were measured, along with N2O fluxes. Microbial communities involved in ammonia oxidation (bacteria and archaea), nitrite reduction, and N2O reduction were quantified using real-time PCR targeting functional genes (amoA, nirS, and nosZ). Overall, the addition of DCD significantly (P<0.05) reduced both the formation of nitrate (∼64%), and N2O loss from urine-treated soils (∼44%). The effect of repeating the urine and DCD applications produced similar results with no decline in DCD efficacy. This was despite a doubling in the size of the AOB community, stimulated by the initial urine application. The application of urine+DCD had a significant but minor impact on denitrifying bacteria (nirS), rather the population size of these bacteria correlated with increasing soil temperature over time (rho=0.7; P=0.002). In contrast, copies of nosZ increased with urine addition (P<0.05) but were unaffected by sampling date (increasing soil temperature). Our results demonstrate that an initial DCD application does not affect its efficacy to inhibit nitrification and reduce N2O emissions following a subsequent DCD application 57 days later.

Effect of amending cattle urine with dicyandiamide on soil nitrogen dynamics and leaching of urinary-nitrogen

Oral administration of dicyandiamide (DCD) to grazing ruminants for excretion in urine represents an alternative delivery technique to conventional broadcast application of DCD to reduce urinary nitrogen (N) losses from grazed pastures. A field lysimeter trial and an allied plot mowing trial were conducted to examine the effects of intermixing DCD in cattle urine on soil and pasture N dynamics and leaching losses in a free-draining pumice soil. DCD was either intermixed with urine to achieve equivalent application rates of 10, 30 or 60kgDCDha−1, or surface broadcasted as a spray solution (10 or 30kgDCDha−1) onto the soil surface following urine application and compared to controls (urine and nil-controls without DCD). A single application of 15N-labelled artificial cattle urine (equivalent to 600kgNha−1) and corresponding DCD treatments were applied in late autumn and monitored over the following 300 days. DCD altered the partitioning of the applied urine-15N by increasing plant uptake of urinary-N by 32–60% and decreasing urine-15N in leachate, which was primarily influenced by the amount of DCD applied. The method of DCD application had no significant effect on leaching of any N constituent, except for ammonium-N, which was higher in the intermixed relative to the spray DCD treatments (26 vs. 18kgNha−1, respectively; P<0.05). The total amount of nitrate-N leached was reduced from 217kgNha−1 in the urine-control to 143, 80 and 61kgNha−1 (P<0.05) with increasing rates of DCD application of 10, 30 and 60kgha−1, respectively. Application of DCD also significantly (P<0.05) decreased the total amounts of ammonium-N and dissolved organic-N (DON) leached, but led to leaching losses of DCD-N. Rapid and large leaching losses of DCD down the soil profile led to spatial separation from the ammonium-N retained in the surface layer. Leaching of DCD (below 600mm) at 55–69% of that applied represented an important leachable organic-N source (equivalent to 4–27kgNha−1), and reduced the overall efficacy of DCD in decreasing total N leaching losses. The total N leaching losses from all measured N fractions were 332kgNha−1 in the urine-control compared to 236, 157 and 154kgNha−1 at DCD application rates of 10, 30 and 60kgha−1, respectively. This study highlights the potential benefit from delivering DCD in cattle urine to reduce urinary-N leaching losses, with the most effective targeted single application rate being 30kgha−1 under the experimental conditions of this study.

Effect of human urine as fertilizer on crop production

Nutrient cycling in the soil-plant ecosystem is an essential component of sustainable agriculture. Human excreta though have high nutrient value is being neglected and simply dumped as waste. Out of the human excreta, urine has high nitrogenous fertilizer value than feces. Hence by separating urine in ECOSAN toilet, it can be of great use in fulfilling the fertilizer demand of the country. The main objective of this study is to assess the effect of human urine on crop yield and to find out the appropriate urine dose and time of application to different crops. The study shows that urine can act as effective as a chemical fertilizer and can be used as an efficient source of plant nutrients. In general, 2-3 splits urine application in addition with phosphorus and potash fertilizer gave the comparable result with that of chemical fertilizer. Though there is no statistical difference in production of the crops, the average yield was found to be higher in the application of chemical fertilizer in all crops except in wheat. From the study, it can be concluded that any crops can be grown using urine as a fertilizer without significant reduction in the yield if nutrient losses during handling could minimize. The study recommends the further study in a long-term urine application trial to verify the obtained result and also to observe the effect of urine on soil properties and plant health as well as on the efficacy of urine along with compost in crop production. DOI: http://dx.doi.org/10.3126/ajn.v2i0.7532 Agronomy Journal of Nepal (Agron JN) Vol. 2: 2011 pp.168-172

Nitrate and Nitrous Oxide Dynamics Under Urine Application in an Alluvial Gravel Vadose Zone

Understanding nitrogen (N) processes within the vadose zone is important to estimate N losses to groundwater systems. A field trial was undertaken to examine the dynamics of nitrate (NO3) and nitrous oxide (N2O) in an alluvial gravel vadose zone underlain by shallow groundwater. Synthetic urine (980 kg N ha−1) with a bromide (400 kg Br ha−1) tracer was applied to the surface of a 10‐ by 20‐m plot, and changes in subsurface NO3, Br, and N2O concentrations were compared with those from an adjacent plot, with just the Br tracer applied. Soil solution and air were monitored at multiple depths (from 0.2 to 5 m) over an 18‐mo period. Transport of solution was rapid in the gravel material with some Br transported to 3‐m depth immediately after the urine application. N2O was produced within the soil after urine application. NO3 to Br ratios indicated denitrification in the soil above the gravels, but none within the alluvial gravel vadose zone. In the “–urine” plot N2O concentrations increased with depth, with upward fluxes above the water table to the soil, suggesting N2O production near the water table. A different pattern was observed in the “+urine” plot where N2O was produced both at the soil zone above the gravels and near the water table leading to both upward and downward N2O fluxes. Overall N2O fluxes in the soil zone were greater than at the water table.

Can nail, hair and urine be used for biomonitoring of human exposure to perfluorooctane sulfonate and perfluorooctanoic acid?

Because of the disadvantages of invasive sampling, it is desirable to explore non-invasive matrices for human biomonitoring of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). The aim of this study was to evaluate the application of nail, hair and urine for human biomonitoring of PFOS and PFOA. The concentrations of PFOS and PFOA in matched nail, hair, urine and serum samples collected from 64 donors were measured. The chemicals of interest were detected with high detection frequency in these matrices (90%–100%) except for PFOA in urine samples (56%). Generally, the gender influences on the levels of PFOS and PFOA in these non-invasive matrices were in agreement with that in serum. For PFOS, the coefficients of Spearman correlation between serum samples and nail, hair and urine samples were 0.786 (p<0.001), 0.545 (p<0.001) and 0.302 (p<0.05), respectively. For PFOA, the correlation was only observed between nail samples and serum samples with a correlation coefficient of 0.299 (p<0.05). The results suggested that nail has more potential than hair and urine to be applied in human biomonitoring for PFOS and PFOA in general populations.

Effects of drought and N-fertilization on N cycling in two grassland soils

Changes in frequency and intensity of drought events are anticipated in many areas of the world. In pasture, drought effects on soil nitrogen (N) cycling are spatially and temporally heterogeneous due to N redistribution by grazers. We studied soil N cycling responses to simulated summer drought and N deposition by grazers in a 3-year field experiment replicated in two grasslands differing in climate and management. Cattle urine and NH4NO3 application increased soil NH4(+) and NO3(-) concentrations, and more so under drought due to reduced plant uptake and reduced nitrification and denitrification. Drought effects were, however, reflected to a minor extent only in potential nitrification, denitrifying enzyme activity (DEA), and the abundance of functional genes characteristic of nitrifying (bacterial and archaeal amoA) and denitrifying (narG, nirS, nirK, nosZ) micro-organisms. N2O emissions, however, were much reduced under drought, suggesting that this effect was driven by environmental limitations rather than by changes in the activity potential or the size of the respective microbial communities. Cattle urine stimulated nitrification and, to a lesser extent, also DEA, but more so in the absence of drought. In contrast, NH4NO3 reduced the activity of nitrifiers and denitrifiers due to top-soil acidification. In summary, our data demonstrate that complex interactions between drought, mineral N availability, soil acidification, and plant nutrient uptake control soil N cycling and associated N2O emissions. These interactive effects differed between processes of the soil N cycle, suggesting that the spatial heterogeneity in pastures needs to be taken into account when predicting changes in N cycling and associated N2O emissions in a changing climate.

Priming of soil decomposition leads to losses of carbon in soil treated with cow urine

The extent to which priming of soil carbon (C) decomposition following treatment with cow urine leads to losses of soil C has not been fully investigated. However, this may be an important component of the carbon (C) cycle in intensively grazed pastures. Our objective was to determine soil C losses via priming in soil treated with cow urine and artificial urine. Cow urine, water, 14C-urea artificial urine, and 14C-glucose artificial urine were applied to repacked soil cores and incubated at 25°C for 84 days. We used radio-labelled artificial urine to determine the extent to which urea hydrolysis contributed to elevated carbon dioxide (CO2) emissions in urine-treated soil and as a comparison to the priming effects of cow urine. Water-soluble C, pH, dehydrogenase activity, urease activity, and CO2 evolution were monitored during the incubation. Priming of soil C decomposition (more CO2-C evolved than was added as a C source) in the cow urine treatment was 4.2 ± 0.7 mg C g–1 (5.2 ± 0.9% of soil C concentration, corrected for water control). In the cow urine treatment, ~54% of retained urea was hydrolysed and it contributed 0.4 ± 0.1 mg CO2-C g–1 to total CO2 fluxes. Low urea hydrolysis may have been due to decreased urease activity in the cow urine treatment due to the large amounts of urea present and the increased pH. Dehydrogenase activity was elevated immediately after cow urine application, and indicates that priming was likely due to heightened microbial activity. Negative priming (less CO2-C evolved than was added as a C source) was measured in the artificial urine treatments and this may reflect the differences in composition between the cow and artificial urines. Solubilisation of soil C was also found in the artificial urine treatments, but it did not appear to be correlated with increased pH or periods of greater urea hydrolysis. While cow urine decreased soil C by positively priming soil C decomposition, our artificial urine did not. Therefore, caution is recommended when using artificial urine for C-cycling research. The mechanisms by which both increased soil pH and priming occurs in urine-treated soils require further investigation.

IL-1β-independent activation of lung immunity in male mice by female odor

In previous studies, we showed that long-term perception of female odor increases flu virus resistance in male mice. To expand on this finding, we examined the ability of female chemical cues to rapidly induce leukocyte mobilization into male lung tissue as a critical condition of signal-derived respiratory infection risk reduction, which is usually associated with sniffing scent marks. Here, we compared the immune and endocrine effects of female chemical cues and lipopolysaccharide (LPS) as common triggers of innate immunity. The number of leukocytes in the lung tissue, concentrations of IL-1β in lung and hypothalamus, and plasma corticosterone and testosterone levels were assessed in ICR male mice 2h after the intranasal application of female urine, LPS or urine and LPS. Both stimuli induced leukocyte mobilization but, in contrast to LPS, female urine alone did not stimulate increased IL-1β levels in lung and hypothalamus. Plasma corticosterone increased and plasma testosterone decreased in response to LPS, whereas the concentrations of these hormones did not change in response to female chemical cues. Thus, the present study gives additional evidence for an anticipatory adaptation of male mice to potential breeding risks. Appreciable mobilization of leukocytes to the lungs requires less than 2h and develops through an IL-1β-independent pathway.

Underestimation of urinary biomarker-to-creatinine ratio resulting from age-related gain in muscle mass in rats

Recent efforts have been made to identify useful urinary biomarkers of nephrotoxicity. Furthermore, the application of urine to the other toxicities as new biomarker source has been recently expanded. Meanwhile, correction of urinary biomarker concentrations according to fluctuations in urine flow rate is required for adequate interpretation of the alteration. The urinary biomarker-to-creatinine ratio (UBCR) is widely used because of the convenience, while the urinary biomarker-excretion rate is regarded as the gold standard corrective method. Because creatinine is a catabolite in energy production in muscles, we hypothesized that altered muscle mass could affect creatinine kinetics, ultimately affecting UBCR. However, no study has examined this hypothesis. In this study, we examined the influence of muscle mass gain on UBCR, using male Sprague-Dawley rats during the growth phase, 6–12-week old. Both plasma creatinine and excretion of urinary creatinine (Ucr excretion) showed increases with muscle mass gain in rats, in which the alterations of UBCR were lowered. The renal mRNA level of the organic cation transporter-2 (Oct2), a creatinine transporter, showed an age-related increase, whereas the mRNA level of multidrug and toxin extrusions-1 (Mate1) remained constant. Multiple regression analysis showed that the increase in creatinine clearance highly contributed to the age-related increase in Ucr excretion compared to the mRNA levels of Oct2 and Mate1. This suggested that the age-related increase in Ucr excretion may be attributable to the increased transglomerular passage of creatinine. In conclusion, the results suggest that muscle mass gain can affect creatinine kinetics, leading to underestimation of UBCR. Therefore, it is important to understand the characteristics of the corrective method when using urinary biomarker, the failure of which can result in an incorrect diagnosis.

The effect of the nitrification inhibitor dicyandiamide (DCD) on spring and annual herbage production in urine patches when applied in late summer or early autumn

AbstractA cut plot experiment was undertaken at two sites in Ireland, one a free‐draining acid brown earth at Moorepark (MPK) and the other a fine loam soil with imperfect drainage at Johnstown Castle (JC). The effect of applying the nitrification inhibitor dicyandiamide (DCD) at 10 kg ha−1 in July, August and September or not applying DCD to plots receiving synthetic urine or zero urine on spring and annual herbage production was examined. In the experiment, each site received 350 kg nitrogen (N) fertilizer ha−1 year−1. The application of DCD in August at a rate of 10 kg ha−1 significantly increased spring and annual herbage production by 14 and 15%, respectively, at MPK, when applied following urine application in year 1. There was no effect of DCD applied in year 1 on herbage production at JC. The application of DCD in August resulted in lower soil total oxidized N (TON) content up to sampling day 56 post‐urine application, at MPK in year 1, retaining higher N content in the soil. There was no effect of DCD on any of the parameters measured in year 2 at MPK or at JC. Urine application did not increase spring herbage production at either site. Urine application significantly increased annual herbage production at MPK only in year 1. Urine application increased annual herbage N uptake, herbage crude protein (CP) content and soil mineral N at both sites in both years.