The contribution of carbohydrate C and earthworm activity to the water-stable aggregation of a sandy soil

Soil Research ◽  
1997 ◽  
Vol 35 (1) ◽  
pp. 61 ◽  
Author(s):  
B. P. Degens
Keyword(s):  
Organic Matter ◽  
Sandy Soil ◽  
Bulk Soil ◽  
Organic C ◽  
Water Stable Aggregates ◽  
Incubation Study ◽  
Cast Doubt ◽  
The Stability ◽  
Water Extractable ◽  
Earthworm Activity

An incubation study was conducted to test the effects of decomposing clover tops (added at 0, 6·2 or 12·5 mg organic matter/g soil) and earthworm activity on the contribution of carbohydrate C to the stability of aggregates in a sandy soil. Soils incubated with and without earthworms were separated into surface-casts and bulk soil, and the amounts of water-stable aggregates >1 mm surviving slow and rapid rewetting (when air-dry) in these soil separates were determined. Organic C and acid- and water-extractable carbohydrate C concentrations were determined in the aggregates and bulk soil. The treatments of 6·2 and 12·5 mg organic matter/g soil increased the >1 mm aggregation of the bulk soil by more than 2·2- and 2·8-fold, respectively, compared with the non-amended soils. With the addition of earthworms, there were increases from 1·7- to 1·8-fold only in aggregates surviving slow rewetting. The acid- and water-extractable carbohydrate C contents of aggregates >1 mm in the bulk and surface-cast soils were generally not greater than the carbohydrate C in the bulk soil. Generally, the carbohydrate C fractions were also not increased in the more stable aggregates (rapidly rewet) compared with the weaker aggregates (slowly rewet). Carbohydrate C in bulk soil was generally (P < 0·05) correlated with the amounts of aggregates surviving each rewetting treatment (r > 0·71, P < 0·01). In contrast, greater amounts of carbohydrate in aggregates surviving slow rewetting were not correlated (r < -0·45, P > 0·05), with a greater proportion of these aggregates resisting disruption when the soils were rapidly rewet (except for acid-extractable carbohydrate C; r = -0·84, P < 0·05). These results cast doubt on the usefulness of correlations in assessing the contribution of carbohydrate C to aggregation. The amounts of carbohydrate materials in the soil appeared to have little influence on aggregation, probably because the location of bonding compounds in the soil pore matrix is more critical.

scholarly journals Effects of long-term mowing on the fractions and chemical composition of soil organic matter in a semiarid grassland

2016 ◽  
Author(s):  
Jiang-Ye Li ◽  
Qi-Chun Zhang ◽  
Yong Li ◽  
Hong-Jie Di
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Soil Organic Matter ◽  
Functional Groups ◽  
Soil Microbial Activity ◽  
Net N Mineralization ◽  
Organic C ◽  
Semiarid Grassland ◽  
Soil Microbial ◽  
The Stability

Abstract. Grassland is the second largest carbon pool following forest. Intensive mowing is common to meet the need of increased livestock. However, little information on the quality and quantity of soil organic matter (SOM) under different mowing managements was documented. In this work, the fractions and chemical composition of SOM under different mowing managements were studied using traditional fractionation method and spectroscopy technology (13C-NMR and FTIR) based on a 13-year mowing trial with four treatments: control (CK, unmown), mowing once every second year (M1/2), mowing once a year (M1) and mowing twice a year (M2). The results showed that M1/2 and M1 significantly enhanced the SOM accumulation while M2 did not significantly impacted SOM content but it significantly limited the SOM humification and degradation. Substituted alkyl carbon (C) was the major organic C type as it made up over 40 % of the total C. M1/2 and M1 significantly increased stable C functional groups (alkyl C and aromatic C) by degrading labile C functional group (O-alkyl C) and forming calcium humic acid while M2 had opposite effects. The increase of NMR indices (HB/HI, Al/Ar, A/OA and CC/MC) in M1/2 and M1 further suggested that M1/2 and M1 increased the stability of SOM. Significant correlations between net N mineralization or MBC and C functional groups indicated that the shifts of SOM fractions and chemical composition were closely related to soil microbial activity. Meanwhile, M1 significantly increased soil MBC while M2 worked oppositely. Therefore, M1 are the most recommended mowing management while M2 should be avoided in the semiarid grassland.

The long-term effect of biochar on composition of soil organic matter 

2021 ◽  
Author(s):  
Sandra Pärnpuu ◽  
Karin Kauer ◽  
Henn Raave
Keyword(s):  
Organic Matter ◽  
Nmr Spectroscopy ◽  
Soil Organic Matter ◽  
Soil Samples ◽  
Bulk Soil ◽  
Organic C ◽  
Native Soil ◽  
Soil Hydrophobicity ◽  
Som Decomposition

&lt;p&gt;Biochar has been described as relatively stable form of C with long mean residence time due to its predominantly aromatic structure. Addition of biochar can sequester C in the soil, albeit the effect of biochar on native soil organic C decomposition, whether it stimulates or reduces the decomposition of native soil organic matter, requires further understanding. The aim of this research was to study the long-term impact of biochar (BC) on the composition of soil organic matter (SOM) in Fragi-Stagnic Albeluvisol. The work was compiled on the basis of field experiment, set up on a production field in 2011. The experiment was drawn up of two treatments and four replicates, where on half of the replicates slow-pyrolysis hardwood BC (51.8% C, 0.43% N) produced at 500-600 &amp;#176;C was applied 50 Mg ha&lt;sup&gt;-1&lt;/sup&gt;. The soil samples were collected from 0-10 cm soil layer in autumn 2020. The air-dried samples were sieved through a 2-mm sieve and divided into two fractions: the particulate organic matter (POM) fraction (soil particles larger than 0.063 mm) and the mineral-associated organic matter (MAOM) (&lt;0.063 mm) by density fractionation method. The soil organic carbon (SOC) and total nitrogen (Ntot) concentrations of bulk soil and fractions were measured. The chemical composition of SOM was studied using &lt;sup&gt;13&lt;/sup&gt;C nuclear magnetic resonance (NMR) spectroscopy. Bulk soil samples and fractions were pretreated with 10% HF solution before NMR spectroscopy analysis. Two indices were calculated: the ratio of alkyl C/O-alkyl C, which describes the degree of SOM decomposition and soil hydrophobicity (HI): (aromatic-C+alkyl-C)/O/N-Alkyl-C.&lt;/p&gt;&lt;p&gt;The addition of BC to the soil increased the SOC concentration but did not influence the Ntot concentration and the soil C/N ratio increased from 11.6 to 16.7. The distribution of POM and MAOM was not affected by the BC and POM proportion accounted for an average of 57&amp;#8211;58%. The SOC concentrations of POM and MAOM fractions were higher in the BC variant. The BC increased the proportion of aromatic-C in the SOM, as the proportion of aromatic-C in initial BC was high (almost 92%). Initially the BC is inherently highly hydrophobic and increased the HI of bulk soil, POM, and MAOM fractions. The HI increased in line: MAOM&lt;bulk&lt;POM (1.51&lt;1.67&lt;1.97). An increase in HI inhibits the decomposition of SOM and it was also confirmed by a decreased ratio of alkyl-C/O-alkyl-C after the BC addition. The decomposition degree was lowest in POM fraction where SOC concentration was more than doubled due to BC. The suppressed decomposition was caused by the limitation of soil Ntot concentration and increased C/N ratio.&lt;/p&gt;&lt;p&gt;In conclusion, the effect of BC on the composition of SOM was still evident after 10 years of increasing SOC concentration and soil hydrophobicity and decreasing SOM decomposition degree promoting C sequestration to the soil.&lt;/p&gt;&lt;p&gt;This work was supported by the Estonian Research Council grant PSG147.&lt;/p&gt;

scholarly journals Timescales of carbon turnover in soils with mixed crystalline mineralogies

SOIL ◽  
2017 ◽  
Vol 3 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Lesego Khomo ◽  
Susan Trumbore ◽  
Carleton R. Bern ◽  
Oliver A. Chadwick
Keyword(s):  
Organic Matter ◽  
Arid Zone ◽  
Turnover Time ◽  
Bulk Soil ◽  
Humid Climate ◽  
Mineral Contents ◽  
Organic C ◽  
Soil C ◽  
Fe Oxyhydroxides ◽  
The Mean

Abstract. Organic matter–mineral associations stabilize much of the carbon (C) stored globally in soils. Metastable short-range-order (SRO) minerals such as allophane and ferrihydrite provide one mechanism for long-term stabilization of organic matter in young soil. However, in soils with few SRO minerals and a predominance of crystalline aluminosilicate or Fe (and Al) oxyhydroxide, C turnover should be governed by chemisorption with those minerals. Here, we correlate mineral composition from soils containing small amounts of SRO minerals with mean turnover time (TT) of C estimated from radiocarbon (14C) in bulk soil, free light fraction and mineral-associated organic matter. We varied the mineral amount and composition by sampling ancient soils formed on different lithologies in arid to subhumid climates in Kruger National Park (KNP), South Africa. Mineral contents in bulk soils were assessed using chemical extractions to quantify Fe oxyhydroxides and SRO minerals. Because of our interest in the role of silicate clay mineralogy, particularly smectite (2 : 1) and kaolinite (1 : 1), we separately quantified the mineralogy of the clay-sized fraction using X-ray diffraction (XRD) and measured 14C on the same fraction. Density separation demonstrated that mineral associated C accounted for 40–70 % of bulk soil organic C in A and B1 horizons for granite, nephelinite and arid-zone gabbro soils, and > 80 % in other soils. Organic matter strongly associated with the isolated clay-sized fraction represented only 9–47 % of the bulk soil C. The mean TT of C strongly associated with the clay-sized fraction increased with the amount of smectite (2 : 1 clays); in samples with > 40 % smectite it averaged 1020 ± 460 years. The C not strongly associated with clay-sized minerals, including a combination of low-density C, the C associated with minerals of sizes between 2 µm and 2 cm (including Fe oxyhydroxides as coatings), and C removed from clay-sized material by 2 % hydrogen peroxide had TTs averaging 190 ± 190 years in surface horizons. Summed over the bulk soil profile, we found that smectite content correlated with the mean TT of bulk soil C across varied lithologies. The SRO mineral content in KNP soils was generally very low, except for the soils developed on gabbros under more humid climate that also had very high Fe and C contents with a surprisingly short, mean C TTs. In younger landscapes, SRO minerals are metastable and sequester C for long timescales. We hypothesize that in the KNP, SRO minerals represent a transient stage of mineral evolution and therefore lock up C for a shorter time. Overall, we found crystalline Fe-oxyhydroxides (determined as the difference between Fe in dithionate citrate and oxalate extractions) to be the strongest predictor for soil C content, while the mean TT of soil C was best predicted from the amount of smectite, which was also related to more easily measured bulk properties such as cation exchange capacity or pH. Combined with previous research on C turnover times in 2 : 1 vs. 1 : 1 clays, our results hold promise for predicting C inventory and persistence based on intrinsic timescales of specific carbon–mineral interactions.

Altitude affects the quality of the water-extractable organic matter (WEOM) from rhizosphere and bulk soil in European beech forests

Geoderma ◽  
2017 ◽  
Vol 302 ◽  
pp. 6-13 ◽  
Author(s):  
M. De Feudis ◽  
V. Cardelli ◽  
L. Massaccesi ◽  
D. Hofmann ◽  
A.E. Berns ◽  
...  
Keyword(s):  
Organic Matter ◽  
European Beech ◽  
Bulk Soil ◽  
Beech Forests ◽  
Extractable Organic Matter ◽  
Water Extractable

scholarly journals Stability of soil aggregates and their ability of carbon sequestration

2014 ◽  
Vol 9 (No. 3) ◽  
pp. 111-118 ◽  
Author(s):  
V. Šimanský ◽  
D. Bajčan
Keyword(s):  
Organic Matter ◽  
Carbon Sequestration ◽  
Soil Organic Matter ◽  
Soil Aggregates ◽  
Size Fraction ◽  
Size Fractions ◽  
Water Stable Aggregates ◽  
Binding Agents ◽  
Carbon Reservoir ◽  
The Stability

One of the most important binding agents for forming stable aggregates is a soil organic matter (SOM), which can be retained in various size fractions of aggregates. If aggregates are water-resistant, they retain more carbon. Therefore, the aim of this study was to evaluate the stability of aggregates and their ability of carbon sequestration in different soil types and soil management systems in Slovakian vineyards. The highest content of water-stable macro-aggregates (WSA<sub>ma</sub>) was determined in Cambisols, and the lowest in Fluvisols. The highest content of WSA<sub>ma</sub> (size fraction 0.5&ndash;3 mm) was determined in Chernozems, decreasing within the following sequence: Fluvisols &gt; Leptosols &gt; Cambisols &gt; Luvisols. The soil type had a statistically significant influence on the re-distribution of soil organic matter in size fractions of water-stable aggregates. The highest content of SOM in water-stable aggregates of the vineyards was determined in grassy strips in-between the vineyard rows in comparison to intensively cultivated rows of vineyard. The highest values of carbon sequestration capacity (CSC) in WSA<sub>ma</sub> were found in Cambisols &gt; Leptosols and the lowest values of CSC were in Fluvisols. The micro-aggregates represented a significant carbon reservoir for the intensively cultivated soils (rows of vineyard). On the other hand, increasing of macro-aggregates (size fraction 0.5&ndash;3 mm) was characteristic for grassland soils (between the rows of vineyard).

scholarly journals SOIL ORGANIC MATTER FRACTIONS UNDER SECOND-ROTATION EUCALYPTUS PLANTATIONS IN EASTERN RIO GRANDE DO SUL

2017 ◽  
Vol 41 (1) ◽  
Author(s):  
Emanuelle Mercês Barros Soares ◽  
Ivo Ribeiro Silva ◽  
Nairam Félix Barros ◽  
Rafael Silva Teixeira ◽  
Sebastião Fonseca ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Sandy Soil ◽  
Soil Layer ◽  
Rio Grande ◽  
Rio Grande Do Sul ◽  
Organic C ◽  
C Stocks ◽  
Eucalyptus Plantations ◽  
C And N

ABSTRACT The aim of the present study was to evaluate the effect of eucalyptus plantations on total organic C (TOC) and total N (TN) stocks as well as the C and N in the fulvic acid (FA), humic acid (HA), humin (HU), light organic matter (LOM) and microbial biomass (MB) fractions in soils with different textures in the eastern part of the state of Rio Grande do Sul, Brazil. Soil samples were collected from the 0-10-cm, 10-20-cm, 20-40-cm, 40-60-cm and 60-100-cm soil layers in a completely randomized experimental design with subdivided plots. Under the eucalyptus plantation, clay loam soil presented lower HA, HU and MB C stocks in the 0-100-cm soil layer compared to reference vegetation, whereas sandy soil presented higher and C and N in HA and LOM as well as C in MB. The observed increase in TOC in eucalyptus plantations was more pronounced in the surface soil layer (0-10 cm), i.e., approximately 150% higher than under native vegetation, which was probably due to the high contribution of the eucalyptus litter. Differences in C and N stocks in soil organic matter (SOM) fractions between eucalyptus plantations and areas with reference vegetation were more pronounced in sandy soil, showing the capacity of the clay fraction to protect SOM.

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