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Soil Syst., Volume 4, Issue 1 (March 2020) – 17 articles

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Open AccessArticle
Methane and Nitrous Oxide Emission Fluxes Along Water Level Gradients in Littoral Zones of Constructed Surface Water Bodies in a Rewetted Extracted Peatland in Sweden
Soil Syst. 2020, 4(1), 17; https://doi.org/10.3390/soilsystems4010017 - 24 Mar 2020
Viewed by 403
Abstract
Rewetted extracted peatlands are sensitive ecosystems and they can act as greenhouse gas (GHG) sinks or sources due to changes in hydrology, vegetation, and weather conditions. However, studies on GHG emissions from extracted peatlands after rewetting are limited. Methane (CH4) and [...] Read more.
Rewetted extracted peatlands are sensitive ecosystems and they can act as greenhouse gas (GHG) sinks or sources due to changes in hydrology, vegetation, and weather conditions. However, studies on GHG emissions from extracted peatlands after rewetting are limited. Methane (CH4) and nitrous oxide (N2O) emission fluxes were determined using the opaque closed chamber method along water level gradients from littoral zones to the open water body of constructed shallow lakes with different vegetation zones in a nutrient-rich rewetted extracted peatland in Sweden. Vegetation communities and their position relative to water level, together with short-term water level fluctuations, such as inundation events and seasonal droughts, and temperature had a significant impact on CH4 emissions fluxes. During “normal” and “dry” conditions and high soil temperatures, CH4 emissions were highest from Carex spp.-Typha latifolia L. communities. During inundation events with water levels > 30 cm, sites with flooded Graminoids-Scirpus spp.-Carex spp. emitted most CH4. Methane emissions from the water body of the constructed shallow lakes were low during all water level conditions and over the temperature ranges observed. Nitrous oxide emissions contributed little to the emission fluxes from the soil-plant-water systems to the atmosphere, and they were only detectable from the sites with Graminoids. In terms of management, the construction of shallow lakes showed great potential for lowering GHG emission fluxes from nutrient rich peatlands after peat extraction, even though the vegetated shore emitted some N2O and CH4. Full article
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Open AccessArticle
Mass Balances of a Drained and a Rewetted Peatland: on Former Losses and Recent Gains
Soil Syst. 2020, 4(1), 16; https://doi.org/10.3390/soilsystems4010016 - 16 Mar 2020
Viewed by 345
Abstract
Drained peatlands are important sources of greenhouse gases and are rewetted to curb these emissions. We study one drained and one rewetted fen in terms of losses—and, after rewetting—gains of organic matter (OM), carbon (C), and peat thickness. We determined bulk density (BD) [...] Read more.
Drained peatlands are important sources of greenhouse gases and are rewetted to curb these emissions. We study one drained and one rewetted fen in terms of losses—and, after rewetting—gains of organic matter (OM), carbon (C), and peat thickness. We determined bulk density (BD) and ash/OM (and C/OM) ratios for 0.5 cm thick contiguous slices from peat monoliths to calculate losses. Whereas one site has lost 28.5 kg OM m−2 corresponding to annual emissions of ~10 t CO2 ha−1 a−1 over 50 years of effective drainage, the other site has lost 102 kg OM m−2, corresponding to an annual loss of ~30 t CO2 ha−1 a−1 for 30 years of intensive drainage and 6 t CO2 ha−1 a−1 during ~225 years of weak drainage before that. Height losses ranged from 43 to 162 cm. In the 20 years after rewetting, 2.12 kg C m−2 was accumulated, equaling an average annual uptake of ~0.4 kg CO2 m−2 a−1. The results indicate that rewetting can lead to carbon accumulation in fens. This sink function is only small compared with the high emissions that are avoided through rewetting. Full article
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Open AccessArticle
Kinetics of Phosphorus Release from Vivianite, Hydroxyapatite, and Bone Char Influenced by Organic and Inorganic Compounds
Soil Syst. 2020, 4(1), 15; https://doi.org/10.3390/soilsystems4010015 - 16 Mar 2020
Viewed by 321
Abstract
The availability of P is often insufficient and limited by accumulation in soils. This led to the necessity of solutions for the recovery as well as recycling of secondary P resources. Batch experiments were conducted with CaCl2 and citric acid to characterize [...] Read more.
The availability of P is often insufficient and limited by accumulation in soils. This led to the necessity of solutions for the recovery as well as recycling of secondary P resources. Batch experiments were conducted with CaCl2 and citric acid to characterize P release kinetics from vivianite, hydroxyapatite, and bone char. While the P release during the CaCl2 treatment was so low that only vivianite and hydroxyapatite showed a slightly higher release with increasing CaCl2 concentration, the increase of dissolved P was more pronounced for citric acid. The application of citric acid resulted in a 32,190-fold higher P release for bone char. Fourier-transform infrared spectroscopic data suggested higher instability of hydroxyapatite than for bone char. The kinetic data showed that bone char, especially at a lower particle size, had a higher long-term P release than hydroxyapatite or vivianite. The suitability of hydroxyapatite and bone char as a poorly soluble, but sustainable P source is better than that of vivianite. However, the efficiency as a P fertilizer is also dependent on present soil P mobilization processes. The results underline the importance of the accessibility of fertilized or naturally bound P for plant roots to benefit from the excretion of organic acids. Full article
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Open AccessArticle
From Understanding to Sustainable Use of Peatlands: The WETSCAPES Approach
Soil Syst. 2020, 4(1), 14; https://doi.org/10.3390/soilsystems4010014 - 11 Mar 2020
Cited by 2 | Viewed by 674
Abstract
Of all terrestrial ecosystems, peatlands store carbon most effectively in long-term scales of millennia. However, many peatlands have been drained for peat extraction or agricultural use. This converts peatlands from sinks to sources of carbon, causing approx. 5% of the anthropogenic greenhouse effect [...] Read more.
Of all terrestrial ecosystems, peatlands store carbon most effectively in long-term scales of millennia. However, many peatlands have been drained for peat extraction or agricultural use. This converts peatlands from sinks to sources of carbon, causing approx. 5% of the anthropogenic greenhouse effect and additional negative effects on other ecosystem services. Rewetting peatlands can mitigate climate change and may be combined with management in the form of paludiculture. Rewetted peatlands, however, do not equal their pristine ancestors and their ecological functioning is not understood. This holds true especially for groundwater-fed fens. Their functioning results from manifold interactions and can only be understood following an integrative approach of many relevant fields of science, which we merge in the interdisciplinary project WETSCAPES. Here, we address interactions among water transport and chemistry, primary production, peat formation, matter transformation and transport, microbial community, and greenhouse gas exchange using state of the art methods. We record data on six study sites spread across three common fen types (Alder forest, percolation fen, and coastal fen), each in drained and rewetted states. First results revealed that indicators reflecting more long-term effects like vegetation and soil chemistry showed a stronger differentiation between drained and rewetted states than variables with a more immediate reaction to environmental change, like greenhouse gas (GHG) emissions. Variations in microbial community composition explained differences in soil chemical data as well as vegetation composition and GHG exchange. We show the importance of developing an integrative understanding of managed fen peatlands and their ecosystem functioning. Full article
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Open AccessArticle
Digital, Three-Dimensional Visualization of Root Systems in Peat
Soil Syst. 2020, 4(1), 13; https://doi.org/10.3390/soilsystems4010013 - 29 Feb 2020
Cited by 1 | Viewed by 701
Abstract
Belowground plant structures are inherently difficult to observe in the field. Sedge peat that mainly consists of partly decayed roots and rhizomes offers a particularly challenging soil matrix to study (live) plant roots. To obtain information on belowground plant morphology, research commonly relies [...] Read more.
Belowground plant structures are inherently difficult to observe in the field. Sedge peat that mainly consists of partly decayed roots and rhizomes offers a particularly challenging soil matrix to study (live) plant roots. To obtain information on belowground plant morphology, research commonly relies on rhizotrons, excavations, or computerized tomography scans (CT). However, all of these methods have certain limitations. For example, CT scans of peat cores cannot sharply distinguish between plant material and water, and rhizotrons do not provide a 3D structure of the root system. Here, we developed a low-cost approach for 3D visualization of the root system in peat monoliths. Two large diameter (20 cm) peat cores were extracted, frozen and two smaller peat monoliths (47 × 6.5 × 13 cm) were taken from each core. Slices of 0.5 mm or 1 mm were cut from one of the frozen monoliths, respectively, using a paper block cutter and the freshly cut surface of the monolith was photographed after each cut. A 3D model of the fresh (live) roots and rhizomes was reconstructed from the resulting images of the thinner slices based on computerized image analysis, including preprocessing, filtering, segmentation and 3D visualization using the open-source software Fiji, Drishti, and Ilastik. Digital volume measurements on the models produced similar data as manual washing out of roots from the adjacent peat monoliths. The constructed 3D models provide valuable insight into the three-dimensional structure of the root system in the peat matrix. Full article
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Open AccessArticle
Roots, Tissues, Cells and Fragments—How to Characterize Peat from Drained and Rewetted Fens
Soil Syst. 2020, 4(1), 12; https://doi.org/10.3390/soilsystems4010012 - 28 Feb 2020
Cited by 1 | Viewed by 453
Abstract
We present analyses of macroscopic and microscopic remains as a tool to characterise sedge fen peats. We use it to describe peat composition and stages of peat decomposition, to assess the success of rewetting of a formerly drained fen, and to understand the [...] Read more.
We present analyses of macroscopic and microscopic remains as a tool to characterise sedge fen peats. We use it to describe peat composition and stages of peat decomposition, to assess the success of rewetting of a formerly drained fen, and to understand the workings of these novel ecosystems. We studied two percolation fen sites, one drained and one drained and rewetted 20 years ago. Years of deep drainage have resulted in a layer of strongly decomposed peat which lacks recognizable macro-remains. We could associate micro-remains with macro-remains, and thus still characterise the peat and the plants that once formed it. We show that the strongly decomposed peat is of the same origin as the slightly decomposed peat below, and that is was ploughed. We present descriptions of eight types of the main constituent of sedge peat: plant roots, including Carex rostrata type, C. lasiocarpa/rostrata type, C. limosa type, C. acutiformis type, C. echinata type, Phragmites australis type, Cladium type, Equisetum type. We describe three new non-pollen palynomorph types (microscopic remains) and five new subtypes. The rewetted fen provides insights into plant succession after rewetting and the formation of peat that predominantly consists of roots. Results indicate that leaf sheaths may be a consistent component of the peat. Full article
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Open AccessArticle
Phosphorus Speciation in Long-Term Drained and Rewetted Peatlands of Northern Germany
Soil Syst. 2020, 4(1), 11; https://doi.org/10.3390/soilsystems4010011 - 10 Feb 2020
Viewed by 460
Abstract
Previous studies, conducted at the inception of rewetting degraded peatlands, reported that rewetting increased phosphorus (P) mobilization but long-term effects of rewetting on the soil P status are unknown. The objectives of this study were to (i) characterize P in the surface and [...] Read more.
Previous studies, conducted at the inception of rewetting degraded peatlands, reported that rewetting increased phosphorus (P) mobilization but long-term effects of rewetting on the soil P status are unknown. The objectives of this study were to (i) characterize P in the surface and subsurface horizons of long-term drained and rewetted percolation mires, forest, and coastal peatlands and (ii) examine the influence of drainage and rewetting on P speciation and distributions using wet-chemical and advanced spectroscopic analyses. The total P was significantly (p < 0.05) different at the surface horizons. The total concentration of P ranged from 1022 to 2320 mg kg−1 in the surface horizons and decreased by a factor of two to five to the deepest horizons. Results of the chemical, solution 31P nuclear magnetic resonance (NMR), and P K-edge X-ray absorption near-edge structure (XANES) indicated that the major proportions of total P were organic P (Po). In the same peatland types, the relative proportions of Po and stable P fractions were lower in the drained than in the rewetted peatland. The results indicate that long-term rewetting not only locks P in organic matter but also transforms labile P to stable P fractions at the surface horizons of the different peatland types. Full article
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Open AccessArticle
Rapid Recent Recovery from Acidic Deposition in Central Ontario Lakes
Soil Syst. 2020, 4(1), 10; https://doi.org/10.3390/soilsystems4010010 - 07 Feb 2020
Viewed by 499
Abstract
In many regions, chemical recovery in lakes from acidic deposition has been generally slower than expected due to a variety of factors, including continued soil acidification, climate-induced sulphate (SO4) loading to lakes and increases in organic acidity. In central Ontario, Canada, [...] Read more.
In many regions, chemical recovery in lakes from acidic deposition has been generally slower than expected due to a variety of factors, including continued soil acidification, climate-induced sulphate (SO4) loading to lakes and increases in organic acidity. In central Ontario, Canada, atmospheric sulphur (S) deposition decreased by approximately two-thirds between 1982 and 2015, with half of this reduction occurring between 2005 and 2015. Chemical recovery in the seven lakes was limited prior to 2005, with only small increases in pH, Gran alkalinity and charge-balance ANC (acid-neutralizing capacity). This was because lake SO4 concentrations closely followed changes in S deposition, and decreases in base cation concentration closely matched declines in SO4. However, decreases in S deposition and lake SO4 were more pronounced post-2005, and much smaller decreases in lake base cation concentrations relative to SO4 resulted in large and rapid increases in pH, alkalinity and ANC. Dissolved organic carbon concentrations in lakes increased over the study period, but had a limited effect on lake recovery. Clear chemical recovery of these lakes only occurred after 2005, coinciding with a period of dramatic declines in S deposition. Full article
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Open AccessArticle
The 3R Principles for Applying Biochar to Improve Soil Health
Soil Syst. 2020, 4(1), 9; https://doi.org/10.3390/soilsystems4010009 - 04 Feb 2020
Cited by 1 | Viewed by 529
Abstract
Amending soil with biochar is a promising approach to persistently improve soil health and promote crop growth. The efficacy of soil biochar amendment, however, is soil specific, biochar dependent, and influenced by the biochar application programs. To maximize the benefits of biochar application, [...] Read more.
Amending soil with biochar is a promising approach to persistently improve soil health and promote crop growth. The efficacy of soil biochar amendment, however, is soil specific, biochar dependent, and influenced by the biochar application programs. To maximize the benefits of biochar application, this paper proposes the 3R principles for applying biochar to soils: right biochar source, right application rate, and right placement in soil. The quality of biochar as a soil amendment varies significantly with the feedstock and the production conditions. Biochar products capable of everlastingly sustaining soil health are those with high stable organic carbon (OC) content and high water- and nutrient-holding capacities that are manufactured from uncontaminated biomass materials. Acidic, coarse-textured, highly leached soils respond remarkably more to biochar amendment than other types of soils. Soil amendment with particular biochars at as low as 0.1 mass% (equivalent to 2 Mg ha−1) may enhance the seasonal crop productivity. To achieve the evident, long-term soil health improvement effects, wood- and crop residue-derived biochars should be applied to soil at one time or cumulatively 2–5 mass% and manure-derived biochars at 1–3 mass% soil. Optimal amendment rates of particular biochar soil systems should be prescreened to ensure the pH of newly treated soils is less than 7.5 and the electrical conductivity (EC) below 2.7 dS m−1 (in 1:1 soil/water slurry). To maximize the soil health benefits while minimizing the erosion risk, biochar amendment should be implemented through broadcasting granular biochar in moistened conditions or in compost mixtures to cropland under low-wind weather followed by thorough and uniform incorporation into the 0–15 cm soil layer. Biochars are generally low in plant macronutrients and cannot serve as a major nutrient source (especially N) to plants. Combined chemical fertilization is necessary to realize the synergic beneficial effects of biochar amendment. Full article
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Open AccessArticle
The Influences of Magnesium upon Calcium Phosphate Mineral Formation and Structure as Monitored by X-ray and Vibrational Spectroscopy
Soil Syst. 2020, 4(1), 8; https://doi.org/10.3390/soilsystems4010008 - 29 Jan 2020
Viewed by 507
Abstract
Calcium phosphate minerals are typically the solubility-limiting phase for phosphate in calcareous soils. Magnesium (Mg), despite being present in high concentrations in calcareous soils, has been largely neglected in the study of formation and stabilization of soil phosphate minerals due to the high [...] Read more.
Calcium phosphate minerals are typically the solubility-limiting phase for phosphate in calcareous soils. Magnesium (Mg), despite being present in high concentrations in calcareous soils, has been largely neglected in the study of formation and stabilization of soil phosphate minerals due to the high solubility of pure Mg phosphate phases. In this study, a series of four common calcium and magnesium phosphate minerals, hydroxyapatite/bobierrite and brushite/newberyite were synthesized in the presence of widely varying Mg concentrations to examine the effects of Mg substitution upon the local bonding environment and overall structure of the precipitates. Phosphorus K-edge X-Ray absorption near edge structure (XANES) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) provide insight into the local coordination environment, whereas synchrotron powder X-Ray diffraction (SP-XRD) and transmission electron microscopy (TEM) were used for structural analysis. In acidic to neutral pH, Mg-bearing brushite phases formed over a wide range of Ca:Mg ratios. In neutral to high pH systems, a short-range order amorphous calcium phosphate (ACP) with a local structure analogous with hydroxyapatite precipitated for a wide range of Ca to Mg ratios. It can be inferred that the presence of Mg in soils leads to stabilization of metastable phases: via cation substitution in brushite and via poisoning of crystal growth propagation for hydroxyapatite. Full article
(This article belongs to the Special Issue Using Synchrotron Radiation to Perform Phosphate Speciation in Soils)
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Open AccessEditorial
Acknowledgement to Reviewers of Soil Systems in 2019
Soil Syst. 2020, 4(1), 7; https://doi.org/10.3390/soilsystems4010007 - 21 Jan 2020
Viewed by 462
Abstract
The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not. [...] Full article
Open AccessArticle
Effect of Cover Crop on Carbon Distribution in Size and Density Separated Soil Aggregates
Soil Syst. 2020, 4(1), 6; https://doi.org/10.3390/soilsystems4010006 - 15 Jan 2020
Viewed by 640
Abstract
Increasing soil organic carbon (SOC) stocks in agricultural soils can contribute to stabilizing or even lowering atmospheric greenhouse gas (GHG) concentrations. Cover crop rotation has been shown to increase SOC and provide productivity benefits for agriculture. Here we used a split field design [...] Read more.
Increasing soil organic carbon (SOC) stocks in agricultural soils can contribute to stabilizing or even lowering atmospheric greenhouse gas (GHG) concentrations. Cover crop rotation has been shown to increase SOC and provide productivity benefits for agriculture. Here we used a split field design to evaluate the short-term effect of cover crop on SOC distribution and chemistry using a combination of bulk, isotopic, and spectroscopic analyses of size-and density-separated soil aggregates. Macroaggregates (>250 µm) incorporated additional plant material with cover crop as evidenced by more negative δ13C values (−25.4‰ with cover crop compared to −25.1‰ without cover crop) and increased phenolic (plant-like) resonance in carbon NEXAFS spectra. Iron EXAFS data showed that the Fe pool was composed of 17–21% Fe oxide with the remainder a mix of primary and secondary minerals. Comparison of oxalate and dithionite extractions suggests that cover crop may also increase Fe oxide crystallinity, especially in the dense (>2.4 g cm−3) soil fraction. Cover crop δ13C values were more negative across density fractions of bulk soil, indicating the presence of less processed organic carbon. Although no significant difference was observed in bulk SOC on a mass per mass basis between cover and no cover crop fields after one season, isotopic and spectroscopic data reveal enhanced carbon movement between aggregates in cover crop soil. Full article
(This article belongs to the Special Issue Soil Organic Matter Dynamics)
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Open AccessArticle
Molecular Scale Studies of Phosphorus Speciation and Transformation in Manure Amended and Microdose Fertilized Indigenous Vegetable Production Systems of Nigeria and Republic of Benin
Soil Syst. 2020, 4(1), 5; https://doi.org/10.3390/soilsystems4010005 - 08 Jan 2020
Cited by 1 | Viewed by 806
Abstract
This study investigated the speciation, transformation, and availability of P during indigenous vegetable production by employing a combination of chemical and spectroscopic techniques. The study focused on sites in two ecozones of SSA, the dry savanna (lna, Republic of Benin) and rainforest (Ilesha, [...] Read more.
This study investigated the speciation, transformation, and availability of P during indigenous vegetable production by employing a combination of chemical and spectroscopic techniques. The study focused on sites in two ecozones of SSA, the dry savanna (lna, Republic of Benin) and rainforest (Ilesha, Nigeria). Both sites were cultivated with two indigenous vegetable species: local amaranth (Amaranthus cruentus (AC)) and African eggplant (Solanum macrocarpon (SM)). The soils were treated with 5 t/ha poultry manure and urea fertilizer at the rates of 0, 20, 40, 60, and 80 kg N/ha. Soil samples were collected before planting and after harvest. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to determine P speciation in these soils. Quantitative analysis showed that adsorbed and organic P were the two dominant P species in the manure amended dry savanna (DS) soils before planting and after harvest in soils cultivated with both AC and SM, with the addition of urea (40 kg N/ha) causing an increase in the organic P form in dry savanna soils cultivated with AC. Soils of the rainforest (RF) cultivated with AC initially had large amounts of apatite P in the manure amended soils prior to planting, which was transformed to adsorbed and organic P after harvest. Urea addition to the rainforest soils shifted the dominant P species from organic P to adsorbed and apatite P, which was likely to limit P availability. Soils cultivated with SM had similar proportions of both organic and adsorbed P forms, with 40 kg N/ha addition slightly increasing the proportion of adsorbed P. Full article
(This article belongs to the Special Issue Using Synchrotron Radiation to Perform Phosphate Speciation in Soils)
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Open AccessArticle
Organo-Mineral Interactions Are More Important for Organic Matter Retention in Subsoil Than Topsoil
Soil Syst. 2020, 4(1), 4; https://doi.org/10.3390/soilsystems4010004 - 07 Jan 2020
Cited by 1 | Viewed by 604
Abstract
Decomposing crop residues contribute to soil organic matter (SOM) accrual; however, the factors driving the fate of carbon (C) and nitrogen (N) in soil fractions are still largely unknown, especially the influence of soil mineralogy and autochthonous organic matter concentration. The objectives of [...] Read more.
Decomposing crop residues contribute to soil organic matter (SOM) accrual; however, the factors driving the fate of carbon (C) and nitrogen (N) in soil fractions are still largely unknown, especially the influence of soil mineralogy and autochthonous organic matter concentration. The objectives of this work were (1) to evaluate the retention of C and N from crop residue in the form of occluded and mineral-associated SOM in topsoil (0–20 cm) and subsoil (30–70 cm) previously incubated for 51 days with 13C-15N-labelled corn residues, and (2) to explore if specific minerals preferentially control the retention of residue-derived C and N in topsoil and subsoil. We used topsoil and subsoil having similar texture and mineralogy as proxies for soils being rich (i.e., topsoil) and poor (i.e., subsoil) in autochthonous organic matter. We performed a sequential density fractionation procedure and measured residue-derived C and N in occluded and mineral-associated SOM fractions, and used X-ray diffraction analysis of soil density fractions to investigate their mineralogy. In accordance with our hypothesis, the retention of C and N from crop residue through organo-mineral interactions was greater in subsoil than topsoil. The same minerals were involved in the retention of residue-derived organic matter in topsoil and subsoil, but the residue-derived organic matter was associated with a denser fraction in the subsoil (i.e., 2.5–2.6 g cm−3) than in the topsoil (i.e., 2.3–2.5 g cm−3). In soils and soil horizons with high clay content and reactive minerals, we find that a low SOM concentration leads to the rapid stabilization of C and N from newly added crop residues. Full article
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Open AccessArticle
High-Throughput Isolation of Nucleic Acids from Soil
Soil Syst. 2020, 4(1), 3; https://doi.org/10.3390/soilsystems4010003 - 28 Dec 2019
Viewed by 463
Abstract
DNA-based technologies have become widespread tools for soil microbiological analyses in recent years. DNA extraction from the soil is a key step for these approaches: it is a challenge for researchers as it is still both expensive and time-consuming when large surveys are [...] Read more.
DNA-based technologies have become widespread tools for soil microbiological analyses in recent years. DNA extraction from the soil is a key step for these approaches: it is a challenge for researchers as it is still both expensive and time-consuming when large surveys are planned. The aim of this study was to develop a high-throughput automated protocol for DNA extraction and purification from soil. The protocol was based on the BioSprint 96 platform and compared for validation with another automated procedure and two commercial column-based kits. To evaluate the performances of the protocols, we considered quality, quantity, and amplifiability of the isolated DNA. The material isolated by means of the four protocols showed appropriate yield and quality and positive amplification. The isolation protocol presented here provided similar results to those of the commercial kits but with two essential differences: cost and time for DNA extraction were drastically reduced. This rapid and efficient protocol is envisaged as ideal to standardize soil studies and treat large numbers of samples, representing a workable alternative to low-throughput and expensive manual extraction methods. Full article
Open AccessArticle
Water Table Dynamics Control Carbon Losses from the Destabilization of Soil Organic Matter in a Small, Lowland Agricultural Catchment
Soil Syst. 2020, 4(1), 2; https://doi.org/10.3390/soilsystems4010002 - 20 Dec 2019
Viewed by 435
Abstract
The biogeochemistry of soil organic matter (SOM) is driven by a combination of stabilization and destabilization mechanisms. Among the various ways in which SOM is lost, soil moisture controls the leaching of dissolved organic and inorganic carbon (DOC and DIC) and CO2 [...] Read more.
The biogeochemistry of soil organic matter (SOM) is driven by a combination of stabilization and destabilization mechanisms. Among the various ways in which SOM is lost, soil moisture controls the leaching of dissolved organic and inorganic carbon (DOC and DIC) and CO2 fluxes (FCO2). The aim of this study was to investigate the impact of naturally occurring water table dynamics on the couplings between these three types of C losses. The DIC and DOC concentrations in the soil solutions and the FCO2 values at the soil surface were collected fortnightly over a nine-month period at four sampling points located along two topographic transects characterized by different water table dynamics. The water table depth, soil temperature and water-filled pore space (WFPS) were monitored at each site. Linear and nonlinear regressions were used to explore the couplings between C losses, WFPS and soil temperature. The dynamics of the water table seem to drive DOC solubilization, diffusion, and export mechanisms in addition to microbial processes and the equilibrium between DIC and CO2. The main descriptors of this water table dynamic were the residence time, return time and number of oscillations of the water table. Considering both transects, FCO2 was positively correlated with DOC, which highlights the importance of substrate accessibility for SOM mineralization. This paper emphasizes the importance of the water table dynamic for the coupling between SOM carbon losses. Full article
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Open AccessArticle
Terrain Effects on the Spatial Variability of Soil Physical and Chemical Properties
Soil Syst. 2020, 4(1), 1; https://doi.org/10.3390/soilsystems4010001 - 20 Dec 2019
Viewed by 560
Abstract
Understanding topography effects on soil properties is vital to modelling landscape hydrology and establishing sustainable on-field management practices. This research focuses on an arable area (117 km2) in Southwestern Ethiopia where agricultural fields and bush cover are the dominant land uses. [...] Read more.
Understanding topography effects on soil properties is vital to modelling landscape hydrology and establishing sustainable on-field management practices. This research focuses on an arable area (117 km2) in Southwestern Ethiopia where agricultural fields and bush cover are the dominant land uses. We postulate that adapting either of the soil data resources, coarse resolution FAO-UNESCO (Food and Agriculture Organization of the United Nations Educational, Scientific and Cultural Organization) soil data or pedo-transfer functions (PTFs) is not reliable to indicate future watershed management directions. The FAO-UNESCO data does not account for scale issues and assigns the same soil property at different landscape gradients. The PTFs, on the other hand, do not account for environmental effects and fail to provide all the required data. In this regard, mapping soil property spatial dynamics can help understand landscape physicochemical processes and corresponding land use changes. For this purpose, soil samples were collected across the watershed following a gridded sampling scheme. In areas with heterogeneous topography, soil is spatially variable as influenced by land use and slope. To understand the spatial variation, this research develops indicators, such as topographic index, soil topographic wetness index, elevation, aspect, and slope. Pearson correlation (r), among others, was used to investigate terrain effects on selected soil properties: organic matter (OM), available water content (AWC), sand content (%), clay content (%), silt content (%), electrical conductivity (EC), moist bulk density (MBD), and saturated hydraulic conductivity (Ksat). The results show that there were statistically significant correlations between elevation-based variables and soil physical properties. Among the variables considered, the ‘r’ value between topographic index and soil attributes (i.e., OM, EC, AWC, sand, clay, silt, and Ksat) were 0.66, 0.5, 0.7, 0.55, 0.62, 0.4, and 0.66, respectively. In conclusion, while understanding topography effects on soil properties is vital, implementing either FAO-UNESCO or PTFs soil data do not provide appropriate information pertaining to scale issues. Full article
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