scholarly journals Pedogenic, mineralogical and land-use controls on organic carbon stabilization in two contrasting soils

2010 ◽  
Vol 90 (1) ◽  
pp. 15-26 ◽  
Author(s):  
A F Plante ◽  
I. Virto ◽  
S S Malhi
Keyword(s):  
Thermal Analysis ◽  
Organic Carbon ◽  
Clay Mineralogy ◽  
Density Fractionation ◽  
Scanning Calorimetry ◽  
Organic C ◽  
Soil C ◽  
Density Fractions

Organo-mineral complexation in soils is strongly controlled by pedogenesis, but the mechanisms controlling it and its interaction with cultivation are not yet well understood. We compared the mineralogy and quality of organic carbon (C) among organo-mineral fractions from two soils with contrasting pedogenic origin. Sequential density fractionation (SDF; using 1.6, 1.8, 2.1, 2.4 and 2.6 g mL-1 sodium polytungstate solutions) followed by thermal analysis was applied to a Chernozem from Ellerslie, Alberta, and a Luvisol from Breton, Alberta, each under native and cultivated land uses. Similar clay mineralogy suggested that pedogenic controls on organic C stabilization were related to long-term vegetation cover. In addition to large differences in total organic C quantities, bulk soil and isolated fractions showed significant differences in organic C quality. Samples under native vegetation revealed greater organo-mineral complexation at Ellerslie compared with Breton, as expressed by less solubilisation, more organic C recovered in intermediate-density fractions, and exothermic differential scanning calorimetry peak signals associated with more stable forms of organic C. Long-term cultivation resulted in an overall shift to more stable organo-mineral complexes. The proportion of soil C in the 2.1-2.4 g mL-1 fraction increased under cultivation from 21 to 32% in Breton samples, and from 6 to 16% in Ellerslie samples. The quality of inherited pedogenic soil organic C stored in a soil thus appears to determine its response to long-term cultivation.Key words: Cultivation, sequential density fractionation, organic carbon, organic matter, thermal analysis

scholarly journals Decomposition of carbon adsorbed on iron (III)-treated clays and their effect on the stability of soil organic carbon and external carbon inputs

2021 ◽  
Author(s):  
Mengyang You ◽  
Xia Zhu-Barker ◽  
Timothy A. Doane ◽  
William R. Horwath
Keyword(s):  
Organic Carbon ◽  
Layer Structure ◽  
Mineral Soil ◽  
Clay Mineralogy ◽  
Plant Residue ◽  
C Mineralization ◽  
Organic C ◽  
Soil C ◽  
Native Soil ◽  
The Stability

AbstractThe interaction of organic carbon (OC) with clay and metals stabilizes soil carbon (C), but the influence of specific clay-metal-OC assemblages (flocs) needs further evaluation. This study aimed to investigate the stability of flocs in soil as affected by external C inputs. Flocs representing OC-mineral soil fractions were synthesized using dissolved organic C (DOC) combined with kaolinite (1:1 layer structure) or montmorillonite (2:1 layer structure) clays in the absence or presence of two levels of Fe (III) (named low or high Fe). Flocs were mixed with soil (classified as Luvisol) and incubated with or without 13C labelled plant residue (i.e., ryegrass) for 30 days. The CO2 emissions and DOC concentrations as well as their 13C signatures from all treatments were examined. Total C mineralization from flocs was approximately 70% lower than non-flocced DOC. The flocs made with montmorillonite had 16–43% lower C mineralization rate than those made with kaolinite with no Fe or low Fe. However, when flocs were made with high Fe, clay mineralogy did not significantly affect total C mineralization. A positive priming effect (PE) of flocs on native soil OC was observed in all treatments, with a stronger PE found in lower Fe treatments. The high-Fe clay flocs inhibited ryegrass decomposition, while the flocs made without clay had no impact on it. Interestingly, flocs significantly decreased the PE of ryegrass on native soil OC decomposition. These results indicate that the adsorption of DOC onto clay minerals in the presence of Fe (III) stabilizes it against decomposition processes and its stability increases as Fe in flocs increases. Flocs also protect soil OC from the PE of external degradable plant C input. This study showed that Fe level and clay mineralogy play an important role in controlling soil C stability.

scholarly journals Differential long-term effects of climate change and management on stocks and distribution of soil organic carbon in productive grasslands

2012 ◽  
Vol 9 (1) ◽  
pp. 1055-1096 ◽  
Author(s):  
A. M. G. De Bruijn ◽  
P. Calanca ◽  
C. Ammann ◽  
J. Fuhrer
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Climate Change Scenarios ◽  
Long Term Effects ◽  
Organic C ◽  
Soil C ◽  
The Impact ◽  
Soc Stocks

Abstract. We studied the impact of climate change on the dynamics of soil organic carbon (SOC) stocks in productive grassland systems undergoing two types of management, an intensive type with frequent harvests and fertilizer applications and an extensive system where fertilization is omitted and harvests are fewer. The Oensingen Grassland Model was explicitly developed for this study. It was calibrated using measurements taken in a recently established permanent sward in Central Switzerland, and run to simulate SOC dynamics over 2001–2100 under three climate change scenarios assuming different elements of IPCC A2 emission scenarios. We found that: (1) management intensity dominates SOC until approximately 20 yr after grassland establishment. Differences in SOC between climate scenarios become significant after 20 yr and climate effects dominate SOC dynamics from approximately 50 yr after establishment, (2) carbon supplied through manure contributes about 60% to measured organic C increase in fertilized grassland. (3) Soil C accumulates particularly in the top 10 cm soil until 5 yr after establishment. In the long-term, C accumulation takes place in the top 15 cm of the soil profile, while C content decreases below this depth. The transitional depth between gains and losses of C mainly depends on the vertical distribution of root senescence and root biomass. We discuss the importance of previous land use on carbon sequestration potentials that are much lower at the Oensingen site under ley-arable rotation and with much higher SOC stocks than most soils under arable crops. We further discuss the importance of biomass senescence rates, because C balance estimations indicate that these may differ considerably between the two management systems.

scholarly journals Differential long-term effects of climate change and management on stocks and distribution of soil organic carbon in productive grasslands

2012 ◽  
Vol 9 (6) ◽  
pp. 1997-2012 ◽  
Author(s):  
A. M. G. De Bruijn ◽  
P. Calanca ◽  
C. Ammann ◽  
J. Fuhrer
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Climate Change Scenarios ◽  
Long Term Effects ◽  
Organic C ◽  
Soil C ◽  
The Impact ◽  
Soc Stocks

Abstract. We studied the impact of climate change on the dynamics of soil organic carbon (SOC) stocks in productive grassland systems undergoing two types of management, an intensive type with frequent harvests and fertilizer applications and an extensive system without fertilization and fewer harvests. Simulations were conducted with a dedicated newly developed model, the Oensingen Grassland Model. It was calibrated using measurements taken in a recently established permanent sward in Central Switzerland, and run to simulate SOC dynamics over 2001–2100 under various climate change scenarios assuming different elements of IPCC A2 emission scenarios. We found that: (1) management intensity dominates SOC until approximately 20 years after grassland establishment. Differences in SOC between climate scenarios become significant after 20 years and climate effects dominate SOC dynamics from approximately 50 years after establishment. (2) Carbon supplied through manure contributes about 60 % to measured organic C increase in fertilized grassland. (3) Soil C accumulates particularly in the top 10 cm of the soil until 5 years after establishment. In the long-term, C accumulation takes place in the top 15 cm of the soil profile, while C content decreases below this depth. The transitional depth between gains and losses of C mainly depends on the vertical distribution of root senescence and root biomass. We discuss the importance of previous land use on carbon sequestration potentials that are much lower at the Oensingen site under ley-arable rotation with much higher SOC stocks than most soils under arable crops. We further discuss the importance of biomass senescence rates, because C balance estimations indicate that these may differ considerably between the two management systems.

scholarly journals Decomposition of Carbon Adsorbed on Iron (III)-Treated Clays and Their Effect on the Stability of Soil Organic Carbon and External Carbon Inputs

2021 ◽  
Author(s):  
Mengyang You ◽  
Xia Zhu-Barker ◽  
Timothy A. Doane ◽  
William R. Horwath
Keyword(s):  
Organic Carbon ◽  
Layer Structure ◽  
Mineral Soil ◽  
Clay Mineralogy ◽  
C Mineralization ◽  
Organic C ◽  
Soil C ◽  
Native Soil ◽  
Decomposition Processes ◽  
The Stability

Abstract The interaction of organic carbon (OC) with clay and metals stabilizes soil carbon (C), but the influence of specific clay-metal-OC assemblages (flocs) needs further evaluation. Clay-metal-OC assemblages representing OC-mineral soil fractions were synthesized using dissolved organic C (DOC) combined with kaolinite (1:1 layer structure) or montmorillonite (2:1 layer structure) clays in the absence or presence of two levels of Fe (III). Flocs were mixed with soil and incubated for 30 days. Total C mineralization from flocs was approximately 70% lower than non-flocced DOC. The flocs made with montmorillonite had 16–43% lower C mineralization rate than those made with kaolinite with no Fe or low Fe. However, when flocs were made with high Fe, clay mineralogy did not significantly affect total C mineralization. A positive priming effect (PE) of flocs on native soil OC was observed in all treatments, with a stronger PE found in lower Fe treatments. The high-Fe clay flocs inhibited ryegrass decomposition, while the flocs made without clay had no impact on it. Interestingly, flocs significantly decreased the PE of ryegrass on native soil OC decomposition. These results indicate that the adsorption of DOC onto clay minerals in the presence of Fe (III) stabilizes it against decomposition processes and its stability increases as Fe in flocs increases. Flocs also protect soil OC from the PE of external degradable plant C input. This study showed that Fe level and clay mineralogy play an important role in controlling soil C stability.

Predicting bi-decadal soil organic carbon mineralization with Rock-Eval® thermal analysis

2020 ◽  
Author(s):  
Pierre Barré ◽  
Laure Soucémarianadin ◽  
Baudin François ◽  
Chenu Claire ◽  
Bent Christensen ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Regression Models ◽  
Soil Samples ◽  
Organic C ◽  
Significant Regression ◽  
Rock Eval ◽  
Soc Mineralization

<p>The organic carbon reservoir of soils is a key component of climate change, calling for an accurate knowledge of the residence time of soil organic carbon (SOC). Existing proxies of the labile SOC pool such as particulate organic carbon or basal respiration tests are time consuming and unable to consistently predict SOC mineralization over years to decades. Similarly, models of SOC dynamics often yield unrealistic values of the size of SOC kinetic pools. Rock-Eval® 6 (RE6) thermal analysis of bulk soil samples has recently been shown to provide useful and cost-effective information regarding the long-term in-situ decomposition of SOC. The objective of this study was to design a method based on RE6 indicators to assess for a given soil, the proportion of SOC that will be mineralized in the coming 20 years.</p><p>To do so, we needed samples ready to be analyzed using RE6 with a known proportion of SOC mineralized in 20 years. We used archived soil samples from 4 long-term bare fallows and 8 C<sub>3</sub>/C<sub>4</sub> chronosequences. For each sample, the value of bi-decadal SOC mineralization was obtained from the observed SOC dynamics of its long-term bare fallow plot or the calculated C<sub>3</sub>-derived SOC decline following the conversion to C<sub>4</sub> plants. Those values ranged from 0.3 to 14.3 gC·kg<sup>−1</sup> (concentration data), representing 8.6 to 52.6% of total SOC (proportion data). All samples were analyzed using RE6 and simple linear regression models were used to predict bi-decadal SOC loss (concentration and proportion data) from 4 RE6 parameters: 1) HI (the amount of hydrogen-rich effluents formed during the pyrolysis phase of RE6; mgCH.g<sup>-1</sup> SOC), 2) OI<sub>RE6</sub> (the O recovered as CO and CO<sub>2</sub> during the pyrolysis phase of RE6; mgO<sub>2</sub>.g<sup>-1</sup> SOC), 3) PC/SOC (the amount of organic C evolved during the pyrolysis phase of RE6; % of total SOC) and 4) T50 CO<sub>2</sub> oxidation (the temperature at which 50% of the residual organic C was oxidized to CO<sub>2</sub> during the RE6 oxidation phase; °C).</p><p>The RE6 HI parameter yielded the best predictions of bi-decadal SOC mineralization, for both concentration and proportion data. PC/SOC and T50 CO<sub>2</sub> oxidation parameters also yielded significant regression models. The OI<sub>RE6</sub> parameter was not a good predictor of bi-decadal SOC loss, with non-significant regression models. The results showed that SOC chemical composition (HI is a proxy for SOC H/C ratio), and to a lesser degree SOC thermal stability, are related to bi-decadal SOC dynamics. The RE6 thermal analysis method can therefore provide a quantitative and accurate estimate of SOC biogeochemical stability.</p>

The effects of cultivation method, fertilizer input and previous sward type on organic C and N storage and gaseous losses under spring and winter barley following long-term leys

2002 ◽  
Vol 139 (3) ◽  
pp. 231-243 ◽  
Author(s):  
A. J. A. VINTEN ◽  
B. C. BALL ◽  
M. F. O'SULLIVAN ◽  
J. K. HENSHALL
Keyword(s):  
Spring Barley ◽  
Balance Sheet ◽  
N Fertilizer ◽  
Net N Mineralization ◽  
No Tillage ◽  
Confidence Limits ◽  
Organic C ◽  
Soil C ◽  
C And N

The effects of ploughing or no-tillage of long-term grass and grass-clover swards on changes in organic C and N pools and on CO2 and denitrified gas emissions were investigated in a 3-year field experiment in 1996–99 near Penicuik, Scotland. The decrease in soil C content between 1996 and 1999 was 15·3 t/ha (95% confidence limits were 1·7–28·9 t/ha). Field estimates of CO2 losses from deep-ploughed, normal-ploughed and no-tillage plots were 3·1, 4·5 and 4·6 t/ha over the sampling periods (a total of 257 days) in 1996–98. The highest N2O fluxes were from the fertilized spring barley under no-tillage. Thus no-tillage did not reduce C emissions, caused higher N2O emissions, and required larger inputs of N fertilizer than ploughing. By contrast, deep ploughing led to smaller C and N2O emissions but had no effect on yields, suggesting that deep ploughing might be an appropriate means of conserving C and N when leys are ploughed in. Subsoil denitrification losses were estimated to be 10–16 kg N/ha per year by measurement of 15N emissions from incubated intact cores. A balance sheet of N inputs and outputs showed that net N mineralization over 3 years was lower from plots receiving N fertilizer than from plots receiving no fertilizer.

scholarly journals Boreal-forest soil chemistry drives soil organic carbon bioreactivity along a 314-year fire chronosequence

SOIL ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 195-213
Author(s):  
Benjamin Andrieux ◽  
David Paré ◽  
Julien Beguin ◽  
Pierre Grondin ◽  
Yves Bergeron
Keyword(s):  
Organic Carbon ◽  
Indirect Effect ◽  
Soil Chemistry ◽  
Mineral Soil ◽  
Chemical Properties ◽  
Soil C ◽  
C Pools ◽  
Time Since Fire ◽  
C Stock

Abstract. Following a wildfire, organic carbon (C) accumulates in boreal-forest soils. The long-term patterns of accumulation as well as the mechanisms responsible for continuous soil C stabilization or sequestration are poorly known. We evaluated post-fire C stock changes in functional reservoirs (bioreactive and recalcitrant) using the proportion of C mineralized in CO2 by microbes in a long-term lab incubation, as well as the proportion of C resistant to acid hydrolysis. We found that all soil C pools increased linearly with the time since fire. The bioreactive and acid-insoluble soil C pools increased at a rate of 0.02 and 0.12 MgC ha−1 yr−1, respectively, and their proportions relative to total soil C stock remained constant with the time since fire (8 % and 46 %, respectively). We quantified direct and indirect causal relationships among variables and C bioreactivity to disentangle the relative contribution of climate, moss dominance, soil particle size distribution and soil chemical properties (pH, exchangeable manganese and aluminum, and metal oxides) to the variation structure of in vitro soil C bioreactivity. Our analyses showed that the chemical properties of podzolic soils that characterize the study area were the best predictors of soil C bioreactivity. For the O layer, pH and exchangeable manganese were the most important (model-averaged estimator for both of 0.34) factors directly related to soil organic C bioreactivity, followed by the time since fire (0.24), moss dominance (0.08), and climate and texture (0 for both). For the mineral soil, exchangeable aluminum was the most important factor (model-averaged estimator of −0.32), followed by metal oxide (−0.27), pH (−0.25), the time since fire (0.05), climate and texture (∼0 for both). Of the four climate factors examined in this study (i.e., mean annual temperature, growing degree-days above 5 ∘C, mean annual precipitation and water balance) only those related to water availability – and not to temperature – had an indirect effect (O layer) or a marginal indirect effect (mineral soil) on soil C bioreactivity. Given that predictions of the impact of climate change on soil C balance are strongly linked to the size and the bioreactivity of soil C pools, our study stresses the need to include the direct effects of soil chemistry and the indirect effects of climate and soil texture on soil organic matter decomposition in Earth system models to forecast the response of boreal soils to global warming.

Soil organic matter in rainfed cropping systems of the Australian cereal belt

Soil Research ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 435 ◽  
Author(s):  
R. C. Dalal ◽  
K. Y. Chan
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Management Practices ◽  
Performance Indicator ◽  
Annual Rainfall ◽  
Soil Productivity ◽  
Organic C ◽  
Soil C ◽  
Eastern Australia

The Australian cereal belt stretches as an arc from north-eastern Australia to south-western Australia (24˚S–40˚S and 125˚E–147˚E), with mean annual temperatures from 14˚C (temperate) to 26˚C (subtropical), and with annual rainfall ranging from 250 mm to 1500 mm. The predominant soil types of the cereal belt include Chromosols, Kandosols, Sodosols, and Vertosols, with significant areas of Ferrosols, Kurosols, Podosols, and Dermosols, covering approximately 20 Mha of arable cropping and 21 Mha of ley pastures. Cultivation and cropping has led to a substantial loss of soil organic matter (SOM) from the Australian cereal belt; the long-term SOM loss often exceeds 60% from the top 0–0.1 m depth after 50 years of cereal cropping. Loss of labile components of SOM such as sand-size or particulate SOM, microbial biomass, and mineralisable nitrogen has been even higher, thus resulting in greater loss in soil productivity than that assessed from the loss of total SOM alone. Since SOM is heterogeneous in nature, the significance and functions of its various components are ambiguous. It is essential that the relationship between levels of total SOM or its identif iable components and the most affected soil properties be established and then quantif ied before the concentrations or amounts of SOM and/or its components can be used as a performance indicator. There is also a need for experimentally verifiable soil organic C pools in modelling the dynamics and management of SOM. Furthermore, the interaction of environmental pollutants added to soil, soil microbial biodiversity, and SOM is poorly understood and therefore requires further study. Biophysically appropriate and cost-effective management practices for cereal cropping lands are required for restoring and maintaining organic matter for sustainable agriculture and restoration of degraded lands. The additional benefit of SOM restoration will be an increase in the long-term greenhouse C sink, which has the potentialto reduce greenhouse emissions by about 50 Mt CO2 equivalents/year over a 20-year period, although current improved agricultural practices can only sequester an estimated 23% of the potential soil C sink.

Soil acidification and the carbon cycle in a cropping soil of north-eastern Victoria

Soil Research ◽  
1998 ◽  
Vol 36 (2) ◽  
pp. 273 ◽  
Author(s):  
W. J. Slattery ◽  
D. G. Edwards ◽  
L. C. Bell ◽  
D. R. Coventry ◽  
K. R. Helyar
Keyword(s):  
Soil Depth ◽  
Organic C ◽  
Soil Layers ◽  
Soil C ◽  
Soil Zone ◽  
North Eastern ◽  
Soil Buffering ◽  
The Impact ◽  
Total Organic C

Changes in soil organic matter were determined for a long-term (1975–95) experiment at the Rutherglen Research Institute in north-eastern Victoria. The crop rotations in this experiment were continuous lupins (LL) and continuous wheat (WW). The soil at this site was a solodic or Yellow Dermosol with a soil pH of 6·08 (pH in 0·01 М CaCl2 1 : 5) in 1975 in the surface 10 cm, which had declined by 0·8 and 1·5 pH units for WW and LL, respectively, in the 0–20 cm soil zone by 1992. Acidification rates decreased with increasing soil depth. The acidification rate in the 0–60 cm soil zone was 12·5 kmol(H+)/ha·year for the LL rotation and 4·6 kmol(H+)/ha·year for the WW rotation. The amount of CaCO3 required to neutralise the acidification of wheat-lupin rotations as calculated in this paper was up to 3·8 t/ha ·10 years for a WLWL rotation or 3 ·3 t/ha ·10 years for a WWL rotation; these amounts are significantly higher than previously reported rates. In this paper, we calculate the impact of changes in soil carbon (C) status over time, and therefore soil buffering, on the rates of acidification in incremental soil layers to a depth of 60 cm. Total organic C for these rotations in 1992 was 1·12% for WW and 1·17% for LL in the 0–10 cm soil zone. An investigation of the humic and fulvic acid fractions of these 2 rotations to a depth of 60 cm showed that the LL rotation had significantly higher (P < 0·05) C at depth than the WW rotation. Acidification due to the net decrease in soil C over the 15-year study period plus acidification due to the alkali removed in the seed was calculated to be –4·88 kmol(H+)/ha·year for the LL rotation and –6·52 kmol(H+)/ha·year for the WW rotation.

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