Non-living soil organic matter: what do we know about it?

1998 ◽  
Vol 38 (7) ◽  
pp. 667 ◽  
Author(s):  
J. O. Skjemstad ◽  
L. J. Janik ◽  
J. A. Taylor
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Structure ◽  
Chemical Structure ◽  
Review Paper ◽  
Critical Component ◽  
Biological Functions ◽  
Soil Functions ◽  
Mineral Associations ◽  
Considerable Work

Summary. Non-living soil organic matter is a small but critical component of soils contributing to soil structure, fertility and a range of other chemical, physical and biological functions. Although considerable work has contributed to our knowledge of its distribution, chemical structure, mineral associations and turnover, there is still little information on which fractions or pools of non-living soil organic matter are implicated in various soil functions and to what extent. This review paper summarises some of what is known about the distribution, chemistry, mineral associations and soil structure, turnover and the measurement of non-living soil organic matter, with particular emphasis on Australia. It also discusses some of the difficulties in using current methods for describing the function of this material in soil.

scholarly journals Influence of Ammonium on Formation of Mineral-Associated Organic Carbon by an Ectomycorrhizal Fungus

2019 ◽  
Vol 85 (10) ◽  
Author(s):  
Tao Wang ◽  
Zhaomo Tian ◽  
Anders Tunlid ◽  
Per Persson
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Ex Vivo ◽  
Ectomycorrhizal Fungus ◽  
N Availability ◽  
Content Type ◽  
Mineral Particles ◽  
Mineral Associations

ABSTRACT The interactions between dissolved organic matter (DOM) and mineral particles are critical for the stabilization of soil organic matter (SOM) in terrestrial ecosystems. The processing of DOM by ectomycorrhizal fungi contributes to the formation of mineral-stabilized SOM by two contrasting pathways: the extracellular transformation of DOM (ex vivo pathway) and the secretion of mineral-surface-reactive metabolites (in vivo pathway). In this study, we examined how changes in nitrogen (N) availability affected the formation of mineral-associated carbon (C) from these two pathways. DOM was extracted from forest soils. The processing of this DOM by the ectomycorrhizal fungus Paxillus involutus was examined in laboratory-scale studies with different levels of ammonium. At low levels of ammonium (i.e., under N-limited conditions), the DOM components were slightly oxidized, and fungal C metabolites with iron-reducing activity were secreted. Ammonium amendments decreased the amount of C metabolites, and no additional oxidation of the organic matter was detected. In contrast, the hydrolytic activity and the secretion of N-containing compounds increased, particularly when high levels of ammonium were added. Under these conditions, C, but not N, limited fungal growth. Although the overall production of mineral-associated organic C was not affected by ammonium concentrations, the observed shifts in the activities of the ex vivo and in vivo pathways affected the composition of organic matter adsorbed onto the mineral particles. Such changes will affect the properties of organic matter-mineral associations and, thus, ultimately, the stabilization of SOM. IMPORTANCE Nitrogen (N) availability plays a critical role in the cycling and storage of soil organic matter (SOM). However, large uncertainties remain in predicting the net effect of N addition on soil organic carbon (C) storage due to the complex interactions between organic matter, microbial activity, and mineral particles that determine the formation of stable SOM. Here, we attempted to disentangle the effects of ammonium on these interactions in controlled microcosm experiments including the ectomycorrhizal fungus P.involutus and dissolved organic matter extracted from forest soils. Increased ammonium levels affected the fungal processing of the organic material as well as the secretion of extracellular metabolites. Although ammonium additions did not increase the net production of mineral-adsorbed C, changes in the decomposition and secretion pathways altered the composition of the adsorbed organic matter. These changes may influence the properties of the organic matter-mineral associations and, thus, the stabilization of SOM.

How relationships between soil organic matter parameters and soil structure characteristics are affected by the long-term fertilization of a sandy soil

Geoderma ◽  
2019 ◽  
Vol 342 ◽  
pp. 75-84 ◽  
Author(s):  
Vladimír Šimanský ◽  
Martin Juriga ◽  
Jerzy Jonczak ◽  
Łukasz Uzarowicz ◽  
Wojciech Stępień
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Sandy Soil ◽  
Soil Structure ◽  
Structure Characteristics

Measuring Soil Loss and Subsequent Nutrient and Organic Matter Loss on Farmland

2017 ◽  
Author(s):  
Vito Ferro ◽  
Vincenzo Bagarello
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Loss ◽  
Soil Structure ◽  
Overland Flow ◽  
Organic Matter Content ◽  
Matter Content ◽  
Water Infiltration ◽  
Surface Erosion ◽  
Rill Erosion

Field plots are often used to obtain experimental data (soil loss values corresponding to different climate, soil, topographic, crop, and management conditions) for predicting and evaluating soil erosion and sediment yield. Plots are used to study physical phenomena affecting soil detachment and transport, and their sizes are determined according to the experimental objectives and the type of data to be obtained. Studies on interrill erosion due to rainfall impact and overland flow need small plot width (2–3 m) and length (< 10 m), while studies on rill erosion require plot lengths greater than 6–13 m. Sites must be selected to represent the range of uniform slopes prevailing in the farming area under consideration. Plots equipped to study interrill and rill erosion, like those used for developing the Universal Soil Loss Equation (USLE), measure erosion from the top of a slope where runoff begins; they must be wide enough to minimize the edge or border effects and long enough to develop downslope rills. Experimental stations generally include bounded runoff plots of known rea, slope steepness, slope length, and soil type, from which both runoff and soil loss can be monitored. Once the boundaries defining the plot area are fixed, a collecting equipment must be used to catch the plot runoff. A conveyance system (H-flume or pipe) carries total runoff to a unit sampling the sediment and a storage system, such as a sequence of tanks, in which sediments are accumulated. Simple methods have been developed for estimating the mean sediment concentration of all runoff stored in a tank by using the vertical concentration profile measured on a side of the tank. When a large number of plots are equipped, the sampling of suspension and consequent oven-drying in the laboratory are highly time-consuming. For this purpose, a sampler that can extract a column of suspension, extending from the free surface to the bottom of the tank, can be used. For large plots, or where runoff volumes are high, a divisor that splits the flow into equal parts and passes one part in a storage tank as a sample can be used. Examples of these devices include the Geib multislot divisor and the Coshocton wheel. Specific equipment and procedures must be employed to detect the soil removed by rill and gully erosion. Because most of the soil organic matter is found close to the soil surface, erosion significantly decreases soil organic matter content. Several studies have demonstrated that the soil removed by erosion is 1.3–5 times richer in organic matter than the remaining soil. Soil organic matter facilitates the formation of soil aggregates, increases soil porosity, and improves soil structure, facilitating water infiltration. The removal of organic matter content can influence soil infiltration, soil structure, and soil erodibility.

scholarly journals Changes in Soil Structure and Soil Organic Matter Due to Different Severities of Fire

2015 ◽  
Vol 34 (3) ◽  
pp. 226-234 ◽  
Author(s):  
Vladimír Šimanský
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Structure ◽  
Cold Water ◽  
Fire Severity ◽  
Size Fraction ◽  
Water Soluble ◽  
Hot Water ◽  
The Other ◽  
Other Hand

Abstract The effect of different fire severity on the changes of the soil organic matter (SOM) and soil structure was evaluated. Soil samples were collected (May 2010) in the locality of Nitra-Dražovce (Slovakia) from the following plots: 1) control (unburned place), 2) low severity of fire and 3) higher severity of fire. The results showed that the content of water-stable microaggregates (WSAmi) increased by 20% in the area with a low severity of fire, but on the other hand, it decreased by 42% in the area with the higher severity of fire in comparison to control. The higher severity of fire resulted in a decrease of smaller size fractions of water-stable macroaggregates (WSAma) (0.5−0.25) and a low severity of fire resulted in the decrease of WSAma 2−0.5 mm. On the other hand, the content of WSAma in the size fraction >5 mm was higher by 54% and by 32% in the lower and higher severity of fire, respectively, than in unburned soil. The higher severity of fire had a more positive effect on increases of the structure coefficient and coefficient of aggregate stability, as well as on the decrease of the vulnerability coefficient compared to the low severity of fire. After burning, the contents of soil organic carbon (Corg) and labile carbon were significantly increased by the severity of fire. However, the low severity of fire affected more markedly the increase of hot water-soluble and cold water-soluble carbon than the higher severity of fire. After burning and due to the severity of fire, both the carbon of humic and carbon of fulvic acids ratios and SOM stability increased. The parameters of SOM due to fire significantly increased also in WSA with the least changes in WSAmi. The results showed that a low severity of fire increased Corg mainly in WSAma >2mm and WSAmi, whereas high severity fire increased Corg content in the smaller fraction of WSAma.

scholarly journals Land use impact on carbon mineralization is mainly caused by variation of particulate organic matter content rather than of soil structure

2021 ◽  
Author(s):  
Steffen Schlüter ◽  
Tim Roussety ◽  
Lena Rohe ◽  
Vusal Guliyev ◽  
Evgenia Blagodatskaya ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Particulate Organic Matter ◽  
Soil Structure ◽  
Predictive Power ◽  
Carbon Mineralization ◽  
Basal Respiration ◽  
Microstructural Properties ◽  
Soil Functions ◽  
Microbial Hotspots

Abstract. Land use is known to exert a dominant impact on a range of essential soil functions like water retention, carbon sequestration, matter cycling and plant growth. At the same time, land use management is known to have a strong influence on soil structure, e.g. through bioturbation, tillage and compaction. However, it is often unclear whether differences in soil structure are the actual cause for differences in soil functions or just co-occurring. This impact of land use (conventional and organic farming, intensive and extensive meadow, extensive pasture) on the relationship between soil structure and short-term carbon mineralization was investigated at the Global Change Exploratory Facility, in Bad Lauchstädt, Germany. Intact topsoil cores (n = 75) were sampled from each land use type at the early growing season. Soil structure and microbial activity were measured using X-ray computed tomography and respirometry, respectively. Grasslands had a greater microbial activity than croplands, both in terms of basal respiration and rate of carbon mineralization during growth. This was caused by a larger amount of particulate organic matter (POM) in the topsoil of grasslands. The frequently postulated dependency of basal respiration on soil moisture was absent even though some cores were apparently water limited. This finding was related to microenvironments shaping microbial hotspots where the decomposition of plant residues was obviously decoupled from water limitation in bulk soil. Differences in microstructural properties between land uses were surprisingly small, mainly due huge variability induced by patterns of compacted clods and loose areas caused by tillage in cropland soils. The most striking difference was larger macropore diameters in grasslands soil due to the presence of large biopores that are periodically destroyed in croplands. Variability of basal respiration among all soil cores amounted to more than one order of magnitude (0.08–1.42 µg CO2-C h−1 g−1 soil) and was best described by POM mass (R2 = 0.53, p < 0.001). Predictive power was hardly improved by considering all bulk, microstructure and microbial properties jointly. The predictive power of image-derived microstructural properties was low, because aeration was not limiting carbon mineralization and was sustained by pores smaller than the image resolution limit (< 30 µm). The rate of glucose mineralization during growth was explained well by substrate-induced respiration (R2 = 0.84) prior to growth, which was in turn correlated with total microbial biomass, basal respiration and POM mass and again not affected by pore metrics. These findings stress that soil structure had little relevance in predicting carbon mineralization in well-aerated soil, as this predominantly took place in microbial hotspots around degrading POM that was detached from the pore structure and moisture of the bulk soil. Land use therefore affects carbon mineralization in well-aerated soil mainly by the amount and quality of labile carbon.

scholarly journals Soil Erodibility Analysis and Mapping in Gilgel Gibe-I Catchment, Omo-Gibe River Basin, Ethiopia

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Gizaw Tesfaye ◽  
Tolesa Ameyu
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Erosion ◽  
Catchment Area ◽  
Soil Structure ◽  
Soil Erodibility ◽  
Soil Permeability ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Texture Class

The soil erosion factor, erodibility, measures the susceptibility of soil particles to transport and detachment by erosive agents. Soil erosion and sedimentation models use soil properties and erodibility as the main input. However, in developing countries such as Ethiopia, data on soil erosion and soil-related properties are limited. For this reason, different researchers use different data sources that are adopted from a large scale and come with very different results. For this reason, the study was proposed to analyze and map the soil erodibility of the catchment area using primary data. 80 mixed soil samples were taken from the catchment with GPS coordinates and analyzed in the laboratory for soil texture class and soil organic matter. Accordingly, sandy clay loam is a dominant soil texture class covering 65% of the catchment area with 2.46% average soil organic matter, which is high in the mountainous part and lower in the lower valley of the catchment area. Most of the catchment area, which accounts for more than 78% of the area, was dominated by medium- or coarse-grained soil structure, and in the upper parts of the catchment area, 21% of the catchment area was covered with fine-grained soil structure. Similarly, 66% of the catchment area was covered with slow to moderate soil permeability, followed by slow soil permeability covering 21% of the area. Finally, the soil erodibility value of the Gilgel Gibe-I catchment was determined to be 0.046 ton h·MJ−1·mm−1 with a range of 0.032 to 0.063 ton·h·MJ−1·mm−1. In general, soils with slow permeability, high silt content, and medium- to fine-grained soil structures are the most erodible. They are conveniently separate; they tend to crust and form high drainage. Knowing this, the catchment has a moderate soil erodibility value. Thus, the study recommends evidence of land cover and the protection of arable land through suitable soil and water protection measures to improve soil permeability and soil structure.

Assessing the Impact of No-Till on Water Related Soil Functions and the Role of Farmer Networks in Knowledge Exchange and Implementation.

2020 ◽  
Author(s):  
◽  
Kamilla Skaalsveen
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Soil Organic Matter ◽  
Bulk Density ◽  
Water Purification ◽  
Knowledge Exchange ◽  
No Tillage ◽  
Soil Functions ◽  
Soil And Water

No-tillage is a non-inversion farming practice that is becoming more widely used in farming and often considered to enhance soil functions, by increasing soil organic matter levels and thereby improving soil structure. Knowledge about the effects of different management practices on separate soil functions is important to understand potential trade-offs between them. Studies have shown that no-tillage affects soil functions of water purification and water retention and can reduce erosion rates and inputs from agriculture to water bodies, however evidence from north western European countries is still limited. Alongside this gap in evidence about the physical impacts of no-tillage, knowledge about how farmers share knowledge about no-tillage, a knowledge intensive practice, and the role of farmer networks is still growing. This paper presents results from interdisciplinary (PhD) research which measured the effect of no-tillage on water related soil functions in a UK case study and analysed the distribution of no-tillage knowledge through farmer networks. The field-scale monitoring compares two neighbouring farms (one using conventional ploughing and the other no-tillage) with similar soil and topographic characteristics to assess spatial and temporal changes in soil and water variables. The 2-year monitoring included nutrient analysis of surface and sub-surface soil samples, bulk density, soil moisture, infiltration capacity, surface runoff and analysis of Dissolved Reactive Phosphorous (DRP), Total Phosphorous (TP) and Suspended Solids (SS) in downstream waters. Farmers’ networks were mapped using Social Network Analysis (SNA) to reveal the nature and extent of their knowledge exchange about no-tillage. This was complemented by semi-structured interviews with farmers to understand their reasons for implementing no-tillage. This paper presents findings from both aspects of this research. The soil and water data show varying impacts of no-tillage on soil functions and water quality with different soil types and climate. The no-tillage fields had higher bulk density and soil organic matter content and thereby increasing the soil moisture levels, but the free-draining porous limestone was providing greater benefits under no-tillage in this study compared with the limerich loamy soil with high silt and clay content. The SNA suggests that farmers’ networks expanded with the conversion to no-tillage and that their main influencers were other more experienced no-tillage farmers. In this respect I question the role of external organisations in supporting no-tillage adoption. The research offers a significant new contribution to the field as it assesses the effects of no-tillage on water purification and retention functions of the soil, and at the same time contributes to understanding the dynamics of farmer networks and the link to implementation.

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