European Journal of Soil Science
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Carbon dioxide emissions from biochar in soil: role of clay, microorganisms and carbonates Summary The stability of biochar in soil is of importance if it is to be used for carbon sequestration and long‐term improvement of soil properties. It is well known that a significant fraction of biochar is highly stable in soil, but carbon dioxide (CO2 ) is also released immediately after application. This study investigated the nature of the early release of CO2 and the degree to which stabilizing mechanisms protect biochar from microbial attack. Incubations of 14 CCO2 released from carbonates in short‐term experiments is misinterpreted as mineralization of biochar, the impact of this process may be significantly over‐estimated. In addition to the CO2 released from carbonates, there appears to be a labile fraction of biochar that is oxidized quickly during the first days of incubation, probably by both abiotic and biotic processes. Later in the incubation, biotic mineralization appears to be the primary cause of CO2 evolution. Finally, we found that both production temperature and clay content affect biochar mineralization. As protective mechanisms hypothesized to prevent degradation of organic matter in soil usually implicate clay, we conclude that biochar is likely to be protected from mineralization during the early stages of incubation by its own recalcitrant chemical and physical nature as well as by physical protective mechanisms.
European Journal of Soil Science - Tập 65 Số 1 - Trang 52-59 - 2014
Penetration resistance of gypsiferous horizons
European Journal of Soil Science - Tập 48 Số 3 - Trang 535-543 - 1997
Submicroscopy and stable isotope geochemistry of carbonates and associated palygorskite in Iranian Aridisols Summary Pedogenic carbonates in arid and semi‐arid regions of the world have a great significance as palaeoecological and palaeoclimatological indicators and form a major pool in the carbon cycle. We analysed the ultra‐microfabric and the stable isotope composition of C and O in pedogenic carbonates in colluvial soils derived from limestone in an arid region of central Iran. Our objective was to determine the conditions for the formation of soft pedogenic carbonate nodules and their co‐existence with palygorskite in the palaeo‐argillic horizon. Scanning electron microscopy revealed that the calcite aggregates were matted with palygorskite. Ultra‐microtome cuts, examined using transmission electron microscopy, provided more detailed information about the fundamental particle association of secondary carbonates and palygorskite. Although less abundant, other silicate clays were detected in both the acid‐insoluble clay fractions and in ultra‐cuts, mostly in fine clay size, suggesting the engulfing of palygorskite by growing calcite or illuviation of palygorskite during or after formation of the calcite. Coatings of illuvial clays on calcite crystals support the hypothesis that palygorskite was trapped by pedogenic carbonate when the climate was wetter than it is today to form an argillic horizon. However, electron microscopic evidence of the occurrence of fibres on the immediate pedogenic carbonate particle surfaces suggests the in situ formation of palygorskite. The δ13 C and δ18 O values of pedogenic carbonates suggest that these carbonates were formed in an environment with more available moisture and more C4 plants than now.
European Journal of Soil Science - Tập 50 Số 2 - Trang 207-216 - 1999
Effects of microsized rice straw on soil clay dispersibility Abstract The incorporation of straw into soil has been encouraged as an alternative straw‐disposal strategy to the on‐site burning that occurs in many paddy regions. However, this practice may lead to changes in the colloidal properties of soil clays that potentially intensify clay and nutrient losses. This study aimed to demonstrate the effect of engineered microsized straw powder on the colloidal properties of two soil clays, that is, illitic and kaolinitic soil clays. Dynamic light scattering was coupled with the test tube method to evaluate time‐resolved changes in the particle size, zeta potential and dispersibility for the suspensions of straw powder and its mixtures with illitic and kaolinitic soil clays. Data from kinetic experiments over a time span of 20 days revealed that straw powder remarkably increased the dispersibility of soil clays. It was found that straw particles carried negative charges; thus, the introduction of straw powder into the clay suspensions increased the number of negative charges in the system, thereby increasing internal repulsive forces and eventually favouring clay dispersion. Moreover, certain mutual processes, that is, the biodegradation and dissolution of phytoliths (silica in straw), resulted in the release of dissolved organic matter and silicon, which aggravated clay dispersibility. In addition to the “traditional” awareness of the impacts of straw incorporation, for example, creating toxic, reduced environments or increasing CH4 emissions, the changes in the colloidal properties of soil clays should also be highlighted. We propose that the incorporation of straw requires additional solutions for the prevention of clay loss. Highlights
Straw powder was examined for possible effect on colloidal properties of soil clays It was found that straw particles carried negative charges Introduction of straw powder increase repulsive forces and favor clay dispersion Microorganism, B. amyloliquefaciens , enhances the effect of straw powder
European Journal of Soil Science - Tập 73 Số 3 - 2022
Defining the relation between soil water content and net nitrogen mineralization Summary Simulation models of net mineralization of nitrogen (N) in soil need to be able to incorporate the effect of soil water. Our objective was to identify and define the best way of expressing soil water and its effect on net mineralization across a range of soil types. We collated data from 12 laboratory incubation studies, including a total of 33 different soils, where rates of net mineralization of N were determined from the net accumulation of mineral N under a range of water contents at near‐optimal temperatures. Measurements of water potential and limits of water content observed in the field were available for most of these soils. The percentage of pore space filled with water was estimated from measurements of soil bulk density. We found that relative water content, particularly when expressed relative to an upper and lower limit of water content observed in the field, was the best descriptor for net mineralization. The next best descriptions were soil water potential, water content relative to the optimal water content for mineralization, and percentage of pore space filled with water, with water content alone being poor. Although various functions may be used to describe the relation between relative water content and net mineralization of N, an equation for a sigmoidal curve provided the best fit, and explained 78% of the variation.
European Journal of Soil Science - Tập 54 Số 1 - Trang 39-48 - 2003
Comparison of greenhouse gas fluxes and nitrogen budgets from an ombotrophic bog in Scotland and a minerotrophic sedge fen in Finland Northern peatlands cover approximately 4% of the global land surface area. Those peatlands will be particularly vulnerable to environmental and climate change and therefore it is important to investigate their total greenhouse gas (GHG) budgets, to determine the feedback on the climate. Nitrogen (N) is known to influence the GHG budget in particular by affecting the methane (CH4 ) balance. At two peatland sites in Scotland and Finland GHG fluxes of carbon dioxide (CO2 ), methane and nitrous oxide (N2 O) and nitrogen fluxes were measured as part of the European project ‘NitroEurope’. The Scottish site, Auchencorth Moss, was a GHG sink of −321, −490 and −321 g CO2 eq m−2 year−1 in 2006, 2007 and 2008, respectively, with CO2 as the dominating GHG. In contrast, the dominating GHG at the Finnish site, Lompolojänkkä, was CH4 , resulting in the site being a net GHG source of +485 and +431 g CO2 eq m−2 year−1 in 2006 and 2007, respectively. Therefore, Auchencorth Moss had a negative global warming potential (GWP) whilst Lompolojänkkä had a positive GWP over the investigated time period. Initial results yielded a positive N budget for Lompolojänkkä of 7.1 kg N ha−1 year−1 , meaning the site was gaining nitrogen, and a negative N budget for Auchencorth Moss of −2.4 kg N ha year−1 , meaning the site was losing nitrogen.
European Journal of Soil Science - Tập 61 Số 5 - Trang 640-650 - 2010
Factors controlling the variation in organic carbon stocks in agricultural soils of Germany This study gives an overview of soil organic carbon (SOC) stocks in Germany's agricultural soils, and quantifies and explains the influence of explanatory variables such as land use and management, soil type and climate. Over 2500 agricultural sites were sampled and their SOC stocks determined, together with other soil properties. Machine‐learning algorithms were used to identify the most important variables. Land use, land‐use history, clay content and electrical conductivity were the main predictors in the topsoil, whereas bedrock material, relief and electrical conductivity governed the variation in subsoil carbon stocks. We found that 32% of all soil profiles were anthropogenically transformed. The influence of climate variables was surprisingly small, whereas site variables, in particular in the subsoil, explained a large proportion of the variation in soil carbon. The understanding of SOC dynamics at the regional scale requires a thorough description of the spatial variation in soil properties. The effect of agronomic management on SOC stocks was important near the soil surface, but was mainly attributable to land use (grassland or arable and not to other management factors. Highlights
Factors affecting spatial variation of soil organic carbon stocks are largely unknown. More than 200 possible predictors for this variation were assessed for over 2500 sites. Land use (history), texture, electrical conductivity, bedrock and relief were main controlling factors of carbon stock variation. Aggregation and carbon storage capacity of soil determine much of the spatial variation in carbon stocks.
European Journal of Soil Science - Tập 70 Số 3 - Trang 550-564 - 2019
Availability and speciation of cadmium added to a calcareous soil under various managements Summary Potential risks for human health and adverse effects on soil quality caused by accumulation of cadmium (Cd) in soil at concentrations around or exceeding current European Union (EU) permitted limits have long been recognized. We have assessed availability and partitioning of Cd in a Mediterranean calcareous soil under four management regimes. Cadmium was added as a single pulse of CdSO4 at the maximum Cd concentration established by the EU for sludge‐amended agricultural soils and concentrations exceeding the mandatory limits. Soils were treated with 0, 3, 10 and 50 mg Cd kg−1 soil, incubated moist and analysed at selected times up to 600 days. Cadmium availability and distribution in soil were studied by neutral electrolyte and sequential extractions. During the incubation, the availability of Cd was not strictly dependent on the amount of metal added as the exchangeable fractions were similar shortly after the additions of Cd regardless of its initial concentration. Sequential extractions showed that for concentrations of 3 and 10 mg Cd kg−1 soil Cd was evenly distributed among the soil phases, and its mobility was reduced mainly by adsorption on carbonates. At Cd concentrations exceeding 10 mg Cd kg−1 soil a residual fraction appeared, perhaps from precipitation of Cd. Most of the Cd was associated with carbonates; land management and organic matter content had no major effects on the Cd distribution among different soil phases. The extraction protocols were effective for studying the fate of Cd in this calcareous soil as almost all of the Cd added was recovered. However, the introduction of a preliminary step with buffered NH4 NO3 improved the determination of the most labile pools. Availability of Cd in calcareous soils estimated with reference methods appeared to be very small even when its total concentration far exceeded the current EU limits.
European Journal of Soil Science - Tập 55 Số 1 - Trang 123-133 - 2004
A model incorporating the diffuse double layer to predict the electrical conductivity of bulk soil Summary A model has been developed to predict the electrical conductivity of bulk soil. The total soil‐water content is divided into free water and water in the diffuse double layer (DDL) around clay particles. These two fractions of soil water conduct electrical current through the soil and are assumed to act in parallel with the soil solid. The volume of water in the DDL is evaluated from the surface area of the clay and the thickness of the DDL. The surface area of the clay is estimated from its cation exchange capacity (CEC) and surface charge density. A transmission coefficient correcting for the effect of the tortuous flow path of current through the soil, and a proportionality constant relating the electrical conductivity of water in the DDL to that of free water, are included in the model. The transmission coefficient is a function of the contents of water and clay and has been modelled in terms of these factors. The values of the proportionality constant and those relating to the transmission coefficient were optimized for five different soils. The electrical conductivities of the five soils estimated by the model compare well with the measured values, which, however, deviate systematically from predictions by the three‐component model of Rhoades et al .
European Journal of Soil Science - Tập 58 Số 3 - Trang 560-572 - 2007
The effect of compaction on soil electrical resistivity: a laboratory investigation Among the geophysical tools used in soil science, electrical methods are considered as potentially useful to characterize soil compaction intensity. A laboratory investigation was undertaken on agricultural and forest soils in order to study the impact of compaction on bulk soil electrical resistivity. Samples taken from four different types of loamy soils were compacted at three bulk densities (1.1, 1.3 and 1.6 g cm−3 ). Bulk soil resistivity was measured at each compacted state for gravimetric water contents ranging from 0.10 to 0.50 g g−1 . A specific experimental procedure allowed the control of the water‐filling of the intra‐aggregate pores and the inter‐aggregate pores. Soil resistivity decreased significantly with increase in density and typically for gravimetric water contents less than 0.25 g g−1 . The decrease was more pronounced for the drier soils, indicating the strong impact of the surface conductance, especially in agricultural soils. The experimental data were in good agreement with simulated values given by the petro‐physical model of Waxman‐Smits (1968) , at least for water saturation greater than 0.3. The analysis of the petro‐physical parameters derived from the experimental data suggested that: (i) the electrical tortuosity of the loamy agricultural soil was significantly affected by compaction and (ii) the forest soil had a singular microstructure from an electrical point of view and had isolated conductive zones associated with clay embedded in a poorly conductive medium comprised mainly of soil solution and quartz grains. Our results provide the phenomenological basis for assessing, in the field, the relationship between soil electrical resistivity and compaction intensity.
European Journal of Soil Science - Tập 61 Số 6 - Trang 1043-1055 - 2010
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