Modelling the impact of soil processes on the N and O isotope signatures of nitrate in groundwater

2021 ◽  
Author(s):  
Neus Otero ◽  
Mathieu Sebilo ◽  
Bernhard Mayer ◽  
Daren Gooddy ◽  
Dan Lapworth ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Isotope Composition ◽  
Organic N ◽  
Soil Biology ◽  
Soil N ◽  
Plant System ◽  
Soil Microbial ◽  
The Impact ◽  
Loire Valley ◽  
N Pool

<p>Stable isotope fingerprinting is widely applied to plant-soil-groundwater systems in an aim to identify and even quantify the sources of nitrates found in groundwater. Frequently, in such studies, the <em>δ</em><sup>15</sup>N and <em>δ</em><sup>18</sup>O values of nitrogen sources, such as inorganic fertilizers and manure, are directly compared to the isotope signatures of nitrate encountered in groundwater bodies below agricultural watersheds. We submit that the underlying assumptions (conservative behavior of isotope composition, rapid transfer from surface to groundwater) may only be realistic under very specific conditions whereas, in most cases, significant isotope effects exerted by the soil-microbial-plant system on the <em>δ</em><sup>15</sup>N and <em>δ</em><sup>18</sup>O values of nitrate need to be taken into account when attempting a quantitative apportionment of sources of groundwater nitrate.</p><p>We hypothesise that the isotopic signature of nitrate exported from below the root zone and migrating towards the groundwater will reflect the nitrogen isotope composition of the soil organic N pool, rather than the isotope composition of source fertilizer or organic amendments, due to processes that reset source isotope compositions within soil N pools. We test this hypothesis using empirical observations from a diversity of settings, in France, Spain and Canada with a relatively constant historic anthropogenic N source or a simple and well constrained landuse history. Furthermore, through the use of a process-based model (SIMSONIC, Billy et al., 2010) we estimate to what extent the isotopic composition of the predominant N input to the soil-microbial-plant system and the soil N pool has been modified in an attempt to consider these changes in source apportionment studies elucidating the sources of groundwater nitrate.</p><p>This research was supported through the Consortium award MUTUAL, by the LE STUDIUM® Loire Valley Institute for Advanced Studies via its SMART LOIRE VALLEY (SLV) fellowship programme, co-funded by the H2020 Marie Sklodowska-Curie programme, Contract No. 665790.</p><p> </p><p>Billy C., Billen G., Sebilo M., Birgand F., Tournebize J. (2010) Nitrogen isotopic composition of leached nitrate and soil organic matter as an indicator of denitrification in a sloping drained agricultural plot and adjacent uncultivated riparian buffer strips. Soil Biology and Biochemistry, 42, 108-117.</p>

scholarly journals Effects of Changing Temperature on Gross N Transformation Rates in Acidic Subtropical Forest Soils

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 894
Author(s):  
Xiaoqian Dan ◽  
Zhaoxiong Chen ◽  
Shenyan Dai ◽  
Xiaoxiang He ◽  
Zucong Cai ◽  
...  
Keyword(s):  
Temperature Change ◽  
N Mineralization ◽  
Organic N ◽  
Mineralization Rate ◽  
Soil N ◽  
Autotrophic Nitrification ◽  
N Transformation ◽  
Gross N Transformation ◽  
Increasing Temperature ◽  
N Pool

Soil temperature change caused by global warming could affect microbial-mediated soil nitrogen (N) transformations. Gross N transformation rates can provide process-based information about abiotic–biotic relationships, but most previous studies have focused on net rates. This study aimed to investigate the responses of gross rates of soil N transformation to temperature change in a subtropical acidic coniferous forest soil. A 15N tracing experiment with a temperature gradient was carried out. The results showed that gross mineralization rate of the labile organic N pool significantly increased with increasing temperature from 5 °C to 45 °C, yet the mineralization rate of the recalcitrant organic N pool showed a smaller response. An exponential response function described well the relationship between the gross rates of total N mineralization and temperature. Compared with N mineralization, the functional relationship between gross NH4+ immobilization and temperature was not so distinct, resulting in an overall significant increase in net N mineralization at higher temperatures. Heterotrophic nitrification rates increased from 5 °C to 25 °C but declined at higher temperatures. By contrast, the rate of autotrophic nitrification was very low, responding only slightly to the range of temperature change in the most temperature treatments, except for that at 35 °C to 45 °C, when autotrophic nitrification rates were found to be significantly increased. Higher rates of NO3− immobilization than gross nitrification rates resulted in negative net nitrification rates that decreased with increasing temperature. Our results suggested that, with higher temperature, the availability of soil N produced from N mineralization would significantly increase, potentially promoting plant growth and stimulating microbial activity, and that the increased NO3− retention capacity may reduce the risk of leaching and denitrification losses in this studied subtropical acidic forest.

scholarly journals Isotopic composition of maize as related to N-fertilization and irrigation in the Mediterranean region

2011 ◽  
Vol 68 (2) ◽  
pp. 182-190 ◽  
Author(s):  
Berta Lasa ◽  
Iosu Irañeta ◽  
Julio Muro ◽  
Ignacio Irigoyen ◽  
Pedro María Aparicio Tejo
Keyword(s):  
Isotopic Composition ◽  
Zea Mays L ◽  
Isotope Composition ◽  
Application Rate ◽  
N Fertilization ◽  
Furrow Irrigation ◽  
N Leaching ◽  
C And N ◽  
Set Up ◽  
The Impact

Nitrate leaching as a result of excessive application of N-fertilizers and water use is a major problem of vulnerable regions. The farming of maize requires high N fertilization and water inputs in Spain. Isotopic techniques may provide information on the processes involved in the N and C cycles in farmed areas. The aim of this work was studying the impact of sprinkler and furrow irrigation and N input on maize (Zea mays L.) yields, and whether isotopic composition can be used as indicator of best farming practices. Trials were set up in Tudela (Spain) with three rates of N fertilization (0, 240 and 320 kg urea-N ha-1) and two irrigation systems (furrow and sprinkler). Yield, nitrogen content, irrigation parameters, N fate and C and N isotope composition were determined. The rate of N fertilization required to obtain the same yield is considerably higher under furrow irrigation, since the crop has less N at its disposal in furrow irrigation as a result of higher loss of nitrogen by NO3--N leaching and denitrification. A lower δ13C in plants under furrow irrigation was recorded.The δ15N value of plant increased with the application rate of N under furrow irrigation.

scholarly journals Arid Ecosystem Vegetation Canopy-Gap Dichotomy: Influence on Soil Microbial Composition and Nutrient Cycling Functional Potential

2020 ◽  
Vol 87 (5) ◽  
Author(s):  
Priyanka Kushwaha ◽  
Julia W. Neilson ◽  
Albert Barberán ◽  
Yongjian Chen ◽  
Catherine G. Fontana ◽  
...  
Keyword(s):  
Microbial Diversity ◽  
Community Composition ◽  
Functional Capacity ◽  
N Mineralization ◽  
Organic N ◽  
Arid Ecosystem ◽  
Gene Abundance ◽  
Soil Microbial ◽  
Functional Potential ◽  
The Impact

ABSTRACT Increasing temperatures and drought in desert ecosystems are predicted to cause decreased vegetation density combined with barren ground expansion. It remains unclear how nutrient availability, microbial diversity, and the associated functional capacity vary between the vegetated canopy and gap soils. The specific aim of this study was to characterize canopy versus gap microsite effect on soil microbial diversity, the capacity of gap soils to serve as a canopy soil microbial reservoir, nitrogen (N)-mineralization genetic potential (ureC gene abundance) and urease enzyme activity, and microbial-nutrient pool associations in four arid-hyperarid geolocations of the western Sonoran Desert, Arizona, United States. Microsite combined with geolocation explained 57% and 45.8% of the observed variation in bacterial/archaeal and fungal community composition, respectively. A core microbiome of amplicon sequence variants was shared between the canopy and gap soil communities; however, canopy soils included abundant taxa that were not present in associated gap communities, thereby suggesting that these taxa cannot be sourced from the associated gap soils. Linear mixed-effects models showed that canopy soils have significantly higher microbial richness, nutrient content, and organic N-mineralization genetic and functional capacity. Furthermore, ureC gene abundance was detected in all samples, suggesting that ureC is a relevant indicator of N mineralization in deserts. Additionally, novel phylogenetic associations were observed for ureC, with the majority belonging to Actinobacteria and uncharacterized bacteria. Thus, key N-mineralization functional capacity is associated with a dominant desert phylum. Overall, these results suggest that lower microbial diversity and functional capacity in gap soils may impact ecosystem sustainability as aridity drives open-space expansion in deserts. IMPORTANCE Increasing aridity will drive a shift in desert vegetation and interspace gap (microsite) structure toward gap expansion. To evaluate the impact of gap expansion, we assess microsite effects on soil nutrients, microbiome community composition and functional capacity, and the potential of gap soils to serve as microbial reservoirs for plant root-associated microbiomes in an arid ecosystem. Results indicate that gap soils have significantly lower bioavailable nutrients, microbial richness, and N-mineralization functional capacity. Further, abundance of the bacterial urease gene (ureC) correlates strongly with N availability, and its major phylogenetic association is with Actinobacteria, the dominant phylum found in deserts. This finding is relevant because it identifies an important N-mineralization capacity indicator in the arid soil microbiome. Such indicators are needed to understand the relationships between interplant gap expansion and microbial diversity and functional potential associated with plant sustainability. This will be a critical step in recovery of land degraded by aridity stress.

Overwinter soil nitrogen dynamics in seasonally frozen soils

2000 ◽  
Vol 80 (4) ◽  
pp. 541-550 ◽  
Author(s):  
M. C. Ryan ◽  
R. G. Kachanoski ◽  
R. W. Gillham
Keyword(s):  
Soil Water ◽  
Microbial Biomass Carbon ◽  
Nitrogen Dynamics ◽  
Frozen Soil ◽  
Organic N ◽  
Soluble Nitrogen ◽  
Soil N ◽  
Freezing And Thawing ◽  
N Accumulation ◽  
Soil Microbial

An overwinter soil-monitoring study was conducted at two sites in southern Ontario. Soluble soil N accumulation at both sites occured in early winter, peaked when soil water was frozen, and then declined during the period that frozen soil water was present. The amount of soluble soil N accumulated was 48 ± 12 kg N ha−1 at one site, and 21 ± 6 kg N ha−1 at the other. In both cases, the overwinter accumulation approximately doubled the amount of soluble N in the soil. Similar trends were observed in both mineral and organic N, with 60 to 74% of the accumulation occurring in the organic form. No clear correlations between soluble nitrogen dynamics and soil extractable organic carbon or soil microbial biomass carbon dynamics were observed. Denitrification apparently occurred in shallow soil during the thaw period at one site. Since soil nitrate levels decreased before significant thawing occurred, leaching was probably not the primary dissipation mechanism. We hypothesize that the soluble N accumulation was due to death and lysis of soil microorganims during freezing and thawing. The presence of soil ice apparently decreased the lethality of the soil enviroment, allowing N dissipation to occur. Soil N dissipation could be due to gaseous losses, and is likely related to significant N2O fluxes commonly observed during spring thaw. Key words: Nitrogen, overwinter, soil ice

Nitrogen pools and processes in agricultural systems of Coastal British Columbia — A review of published research

2000 ◽  
Vol 80 (1) ◽  
pp. 1-10 ◽  
Author(s):  
C. G. Kowalenko
Keyword(s):  
British Columbia ◽  
Soil Analysis ◽  
Great Influence ◽  
Growing Season ◽  
N Cycling ◽  
Annual Rainfall ◽  
Organic N ◽  
Soil N ◽  
The Impact ◽  
Coastal British Columbia

A significant amount of research on nitrogen (N) dynamics has been conducted within the past 20 yr in south coastal British Columbia. This succinct set of data has practical and environmental information on N cycling particularly focusing on gains to and losses from agricultural fields, and transformations of soil N pools. Coastal British Columbia fields have received large annual additions by application of fertilizer and manure. Some of the manure N from animals using locally grown forages is recycled within the farm operation, but a large amount of N is imported as feed especially for intensive animal production. Budget calculations estimated that there may be substantial losses of N through volatilization from manure, particularly from housing and storage areas, and during application to fields. Some of the volatilized ammonia in holding areas may be recycled to fields via precipitation. Direct measurements of these losses and returns of N have not been made. Studies have shown that there is limited risk of leaching of nitrate beyond the root zone during the growing season because most of the annual rainfall occurs over the winter and because nitrate can be adsorbed to soil particles. However, any extractable inorganic N (nitrate directly and ammonium after nitrification) in the profile at the end of the growing season will be lost over the winter. Most of that loss is due to nitrate leaching, but conditions are also favorable for denitrification. There is considerable (> 200 mg N k−1 in some soils) ammonium-N fixed in Fraser Valley soils, but the impact of this phenomenon to crop growth is still poorly understood. Wetting and drying cycles have a great influence on the dynamics of this pool of soil N. The response of spring growth of grass to the time of N application was influenced by the relative competitiveness of microorganisms and plants for available soil N. A study comparing short-season (broccoli) and long-season (sweet corn) crop responses to N applications showed that the rate at which the plants require N influences their response to N amendments. Raspberries were found to require relatively small quantities of N on a land area basis because of the wide inter-row distances. An autumn soil nitrate test has been proposed for making fertilizer N recommendations for raspberries. Although knowledge gained from this research has provided a basis for interpreting studies for the development of N management practices and for making interim recommendations, a method to predict the amount of N mineralized from soil organic matter is key to the development of soil-analysis-based N rate recommendations. Key words: N cycling, nitrate, ammonium, fixed ammonium, soil organic N, mineralization

scholarly journals Effect of Elevated CO2, O3, and UV Radiation on Soils

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Pavel Formánek ◽  
Klement Rejšek ◽  
Valerie Vranová
Keyword(s):  
Heavy Metals ◽  
Uv Radiation ◽  
Current Knowledge ◽  
Root Exudation ◽  
Future Research ◽  
Soil N ◽  
Soil C ◽  
Soil Microbial ◽  
Competitive Efficiency ◽  
The Impact

In this work, we have attempted to review the current knowledge on the impact of elevated CO2, O3, and UV on soils. Elevated CO2increases labile and stabile soil C pool as well as efficiency of organic pollutants rhizoremediation and phytoextraction of heavy metals. Conversely, both elevated O3and UV radiation decrease inputs of assimilates to the rhizosphere being accompanied by inhibitory effects on decomposition processes, rhizoremediation, and heavy metals phytoextraction efficiency. Contrary to elevated CO2, O3, or UV-B decreases soil microbial biomass, metabolisable C, and soil Ntcontent leading to higher C/N of soil organic matter. Elevated UV-B radiation shifts soil microbial community and decreases populations of soil meso- and macrofauna via direct effect rather than by induced changes of litter quality and root exudation as in case of elevated CO2or O3. CO2enrichment or increased UV-B is hypothesised to stimulate or inhibit both plant and microbial competitiveness for soluble soil N, respectively, whereas O3favours only microbial competitive efficiency. Understanding the consequences of elevated CO2, O3, and UV radiation for soils, especially those related to fertility, phytotoxins inputs, elements cycling, plant-microbe interactions, and decontamination of polluted sites, presents a knowledge gap for future research.

scholarly journals Compound-specific <sup>15</sup>N stable isotope probing of N assimilation by the soil microbial biomass: a new methodological paradigm in soil N cycling

2015 ◽  
Vol 2 (2) ◽  
pp. 1135-1160
Author(s):  
A. F. Charteris ◽  
T. D. J. Knowles ◽  
K. Michaelides ◽  
R. P. Evershed
Keyword(s):  
Stable Isotope ◽  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Stable Isotope Probing ◽  
N Cycling ◽  
Organic N ◽  
Soil N ◽  
Soil Microbial ◽  
Incubation Experiments ◽  
N Assimilation

Abstract. A compound-specific nitrogen-15 stable isotope probing (15N-SIP) technique is described which allows investigation of the fate of inorganic- or organic-N amendments to soils. The technique uses gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to determine the δ15N values of individual amino acids (AAs; determined as N-acetyl, O-isopropyl derivatives) as proxies of biomass protein production. The δ15N values are used together with AA concentrations to quantify N assimilation of 15N-labelled substrates by the soil microbial biomass. The utility of the approach is demonstrated through incubation experiments using inorganic 15N-labelled substrates ammonium (15NH4+) and nitrate (15NO3-) and an organic 15N-labelled substrate, glutamic acid (15N-Glu). Assimilation of all the applied substrates was undetectable based on bulk soil properties, i.e. % total N (% TN), bulk soil N isotope composition and AA concentrations, all of which remained relatively constant throughout the incubation experiments. In contrast, compound-specific AA δ15N values were highly sensitive to N assimilation, providing qualitative and quantitative insights into the cycling and fate of the applied 15N-labelled substrates. The utility of this 15N-AA-SIP technique is considered in relation to other currently available methods for investigating the microbially-mediated assimilation of nitrogenous substrates into the soil organic N pool. This approach will be generally applicable to the study of N cycling in any soil, or indeed, in any complex ecosystem.

scholarly journals Isotopic composition of daily precipitation along the southern foothills of the Himalayas: impact of marine and continental sources of atmospheric moisture

2018 ◽  
Vol 18 (12) ◽  
pp. 8789-8805 ◽  
Author(s):  
Ghulam Jeelani ◽  
Rajendrakumar D. Deshpande ◽  
Michal Galkowski ◽  
Kazimierz Rozanski
Keyword(s):  
Isotopic Composition ◽  
Daily Precipitation ◽  
Isotope Composition ◽  
Himalayan Region ◽  
Water Evaporation ◽  
Western Himalayas ◽  
Atmospheric Moisture ◽  
Air Masses ◽  
Continental Origin ◽  
The Impact

Abstract. The flow of the Himalayan rivers, a key source of fresh water for more than a billion people primarily depends upon the strength, behaviour and duration of the Indian summer monsoon (ISM) and the western disturbances (WD), two contrasting circulation regimes of the regional atmosphere. An analysis of the 2H and 18O isotope composition of daily precipitation collected along the southern foothills of the Himalayas, combined with extensive backward trajectory modelling, was used to gain deeper insight into the mechanisms controlling the isotopic composition of precipitation and the origin of atmospheric moisture and precipitation during ISM and WD periods. Daily precipitation samples were collected during the period from September 2008 to December 2011 at six stations, extending from Srinagar in the west (Kashmir state) to Dibrugarh in the east (Assam state). In total, 548 daily precipitation samples were collected and analysed for their stable isotope composition. It is suggested that the gradual reduction in the 2H and 18O content of precipitation in the study region, progressing from δ18O values close to zero down to ca. −10 ‰ in the course of ISM evolution, stems from regional, large-scale recycling of moisture-driven monsoonal circulation. Superimposed on this general trend are short-term fluctuations of the isotopic composition of rainfall, which might have stem from local effects such as enhanced convective activity and the associated higher degree of rainout of moist air masses (local amount effect), the partial evaporation of raindrops, or the impact of isotopically heavy moisture generated in evapotranspiration processes taking place in the vicinity of rainfall sampling sites. Seasonal footprint maps constructed for three stations representing the western, central and eastern portions of the Himalayan region indicate that the influence of monsoonal circulation reaches the western edges of the Himalayan region. While the characteristic imprint of monsoonal air masses (increase of monthly rainfall amount) can be completely absent in the western Himalayas, the onset of the ISM period in this region is still clearly visible in the isotopic composition of daily precipitation. A characteristic feature of daily precipitation collected during the WD period is the gradual increase of 2H and 18O content, reaching positive δ2H and δ18O values towards the end of the period. This trend can be explained by the growing importance of moisture of continental origin as a source of daily precipitation. High deuterium-excess (d-excess) values of daily rainfall recorded at the monitoring stations (38 cases in total, range from 20.6 to 44.0 ‰) are attributed to moisture of continental origin released into the atmosphere during the evaporation of surface water bodies and/or soil water evaporation.

scholarly journals Nitrogen balance in soil under eucalyptus plantations

2012 ◽  
Vol 36 (4) ◽  
pp. 1239-1248 ◽  
Author(s):  
Patrícia Anjos Bittencourt Barreto ◽  
Antonio Carlos da Gama-Rodrigues ◽  
Emanuela Forestieri da Gama-Rodrigues ◽  
Nairam Félix de Barros
Keyword(s):  
N Balance ◽  
Organic N ◽  
Soil N ◽  
Mineral N ◽  
Wood Harvesting ◽  
N Supply ◽  
Eucalyptus Plantations ◽  
Different Ages ◽  
The Difference ◽  
N Pool

An understanding of the role of organic nitrogen (N) pools in the N supply of eucalyptus plantations is essential for the development of strategies that maximize the efficient use of N for this crop. This study aimed to evaluate the distribution of organic N pools in different compartments of the soil-plant system and their contributions to the N supply in eucalyptus plantations at different ages (1, 3, 5, and 13 years). Three models were used to estimate the contributions of organic pools: Model I considered N pools contained in the litterfall, N pools in the soil microbial biomass and available soil N (mineral N); Model II considered the N pools in the soil, potentially mineralizable N and the export of N through wood harvesting; and Model III (N balance) was defined as the difference between the initial soil N pool (0-10 cm) and the export of N, taking the application of N fertilizer into account. Model I showed that N pools could supply 27 - 70 % of the N demands of eucalyptus trees at different ages. Model II suggested that the soil N pool may be sufficient for 4 - 5 rotations of 5 years. According to the N balance, these N pools would be sufficient to meet the N demands of eucalyptus for more than 15 rotations of 5 years. The organic pools contribute with different levels of N and together are sufficient to meet the N demands of eucalyptus for several rotations.

scholarly journals From the Ground Up: Prairies on Reclaimed Mine Land—Impacts on Soil and Vegetation

Land ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 455
Author(s):  
Rebecca M. Swab ◽  
Nicola Lorenz ◽  
Nathan R. Lee ◽  
Steven W. Culman ◽  
Richard P. Dick
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Properties ◽  
Plant Community ◽  
Prairie Restoration ◽  
Native Plant ◽  
Soil Microbial ◽  
Prairie Restorations ◽  
Mine Lands ◽  
The Impact

After strip mining, soils typically suffer from compaction, low nutrient availability, loss of soil organic carbon, and a compromised soil microbial community. Prairie restorations can improve ecosystem services on former agricultural lands, but prairie restorations on mine lands are relatively under-studied. This study investigated the impact of prairie restoration on mine lands, focusing on the plant community and soil properties. In southeast Ohio, 305 ha within a ~2000 ha area of former mine land was converted to native prairie through herbicide and planting between 1999–2016. Soil and vegetation sampling occurred from 2016–2018. Plant community composition shifted with prairie age, with highest native cover in the oldest prairie areas. Prairie plants were more abundant in older prairies. The oldest prairies had significantly more soil fungal biomass and higher soil microbial biomass. However, many soil properties (e.g., soil nutrients, β-glucosoidase activity, and soil organic carbon), as well as plant species diversity and richness trended higher in prairies, but were not significantly different from baseline cool-season grasslands. Overall, restoration with prairie plant communities slowly shifted soil properties, but mining disturbance was still the most significant driver in controlling soil properties. Prairie restoration on reclaimed mine land was effective in establishing a native plant community, with the associated ecosystem benefits.

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