Importance Of Soil Organic Matter Research Articles

Correlation of contamination/pollution from microplastics with physical properties of inceptisols

Microplastic contamination of soil is increasingly impacting soil performance in agriculture. This research studied the relationship between microplastic contamination with the physical properties of Inceptisols at different slopes in the horticultural production center of Banuhampu, Agam, West Sumatra. The determination of soil samples was carried out by purposive random sampling with a quantitative survey method. Sample testing using randomized completely block design (RCBD) with five treatments and three replications: 25-45% in forests and 0-8%, 8-15%, 15-25%, and 25-45% in fields at a depth of 0-20 cm. Characteristics of physical properties of Inceptisols contaminated with microplastics have a moisture content of 31.69%, a bulk density of 0.78 g cm−3, a total pore space of 70.67% (without considering the importance of soil organic matter), and a soil texture class of sandy loam (68.19% sand, 19.55% silt, and 12.26% clay). The value of microplastic concentration in Inceptisols was 438.33 particles kg−1. The slope does not significantly affect the physical properties of Inceptisols contaminated with microplastics. The effect of microplastic contamination has a significant relationship with the physical properties of Inceptisols, namely clay with a value of r = 0.650** and a linear equation: Microplastic = 15.474 (Clay) + 248.57; R2 = 0.4228.

Using Remote and Proximal Sensing in Organic Agriculture to Assess Yield and Environmental Performance

Satellite and sensor-based systems of site-specific fertilization have been developed almost exclusively in conventional farming. Agronomic and ecological advantages can also be expected from these digital methods in organic farming. However, it has not yet been investigated whether the algorithms and models are also applicable under organic farming conditions. In this study, the digital data and systems tested in the years 2021 and 2022 in southern Germany were (a) reflectance measurements with a tractor-mounted multispectral sensor, calculation of the vegetation index REIP, and application of algorithms; (b) satellite data in combination with the plant growth model PROMET; and (c) determination of the vegetation index NDVI based on satellite data. They were used to determine plant parameters (crop yield, biomass potential) and to calculate nitrogen balances at a high spatial resolution (10 × 10 m). The digital systems were tested at two sites with different organic farming systems (arable farming and dairy farming). Validation of the digital methods was carried out with ground-truth data from manual biomass sampling and combine harvester yield measurement. The nitrate leaching risk from the crop rotations of the farms was analyzed via site-specific N balancing using multi-year satellite data. The N balances were validated by measuring nitrate concentrations in leakage water. Additionally, soil properties, such as soil organic carbon (SOC) and total nitrogen (TN), were measured at the sub-field level. Using geostatistics, plant data, soil properties, and nitrate measurements were transferred into grids of the same resolution to enable correlation analyses. The correlations between yield determined with digital systems and the validation data were up to r = 0.77. Site-specific N balancing showed moderately positive correlations with nitrate concentrations in leakage water (r = 0.50–0.66). The strongly positive influence of the soil properties SOC and TN on crop yields underlines the importance of soil organic matter on soil fertility and site-specific yield potentials. The results show that digital methods allow the spatially high-resolution determination of yields and nitrogen balances in organic farming. This can be the basis for new management strategies in organic farming, e.g., the targeted use of limited nutrients to increase yields. Further validations under differentiated soil, climate, and management conditions are required to develop remote and proximal sensing applications in organic farming.

Using olive mill waste compost with sprinkler irrigation as a strategy to achieve sustainable rice cropping under Mediterranean conditions

Traditional rice (Oryza sativa L.) cropping systems under flooding irrigation combined with conventional tillage management are under increasing threat due to a loss of soil quality and a scarcity of water resources, especially in Mediterranean environments. Hence, the development of such management strategies as no-tillage, the application of organic amendments, and water-saving methods could be vital in enhancing the sustainability of rice crops. This work tests the combination of various management systems for growing rice under Mediterranean conditions. It assesses for the first time their influence on soil properties and rice yield components. A field experiment was carried out in southern Spain over 3 years (2015–2017) with six treatments: tillage and continuous flood irrigation either without or with application of two-phase olive mill waste compost; tillage and sprinkler irrigation either without or with application of mill waste compost; direct seeding (no tillage) and sprinkler irrigation either without or with application of mill waste compost. Applying mill waste compost in combination with sprinkler-rice systems improved significantly the soils’ properties. Sprinkler-rice yield was similar to that of rice under tillage and flooding, but it used less irrigation water. In 2017, the greatest rice yield occurred under tillage and sprinkler irrigation with application of mill waste compost (8581 kg ha-1), showing the importance of soil organic matter on yields. Additionnally, flooding increased significantly weed density because it lowered herbicide efficacy, making weed control a key issue for rice yields. Thus, the novelty of this communication is showing that the application of mill waste compost combined with sprinkler irrigation may be a sustainable alternative for rice crops under Mediterranean conditions, increasing the water efficiency and reducing weed pressure, while improving different soil properties.

Diseminasi Pembuatan Pupuk Organik Cair dari Akar Bambu di Desa Srigading, Lampung Timur

<p><em>Land degradation in the rice field is caused by the continuous use of synthetic agrochemicals and low input of organic fertilizers. Assistance and training for farmers are needed to utilize organic fertilizers as additional inputs in cultivation practices. Liquid organic fertilizer (LOB) can be a solution because the making process and application are easier. This dissemination aims to provide knowledge and practice of making LOB from local biological resources such as bamboo roots. The target of the activity are farmers in Srigading, Labuhan Maringgai, East Lampung. The activity was carried out using explanation method and the practice of making LOB from bamboo roots. This activity is carried out for 6 months covering surveys, preparation, delivering materials, practices, and monitoring. The activity was held on August 7, 2021 at the residence of Mr. Tugimin, with a total of 13 participants. The presentation of the material included the importance of soil organic matter for soil health, explanation about LOB, and continued the practice of making LOB. Based on the results of the pretest, the knowledge of farmers about negative impact of using synthetic agrochemicals and the importance of organic matter is still low, so that the explanation can increase farmers' knowledge as indicated by the posttest is increasing from 20% to 86%. Monitoring result showed that the LOB made has been successful with the characteristics like tape smell, but it is still not yet optimal. Farmers also expect follow-up activities for innovation on other organic fertilizers and biofertilizers.</em></p><p> </p>

Transformation of <i>n</i>-alkanes from plant to soil: a review

Abstract. Despite the importance of soil organic matter (SOM) in the global carbon cycle, there remain many open questions regarding its formation and preservation. The study of individual organic compound classes that make up SOM, such as lipid biomarkers including n-alkanes, can provide insight into the cycling of bulk SOM. While studies of lipid biomarkers, particularly n-alkanes, have increased in number in the past few decades, only a limited number have focused on the transformation of these compounds following deposition in soil archives. We performed a systematic review to consolidate the available information on plant-derived n-alkanes and their transformation from plant to soil. Our major findings were (1) a nearly ubiquitous trend of decreased total concentration of n-alkanes either with time in litterbag experiments or with depth in open plant–soil systems and (2) preferential degradation of odd-chain length and shorter chain length n-alkanes represented by a decrease in either carbon preference index (CPI) or odd-over-even predominance (OEP) with depth, indicating degradation of the n-alkane signal or a shift in vegetation composition over time. The review also highlighted a lack of data transparency and standardization across studies of lipid biomarkers, making analysis and synthesis of published data time-consuming and difficult. We recommend that the community move towards more uniform and systematic reporting of biomarker data. Furthermore, as the number of studies examining the complete leaf–litter–soil continuum is very limited as well as unevenly distributed over geographical regions, climate zones, and soil types, future data collection should focus on underrepresented areas as well as quantifying the transformation of n-alkanes through the complete continuum from plant to soil.

Fungal Community Composition and Diversity Vary With Soil Horizons in a Subtropical Forest.

Soil fungal communities, which drive many ecosystem processes, vary across soil horizons. However, how fungal communities are influenced by soil horizon layers remains largely unstudied. In this study, soil samples were collected from the organic horizon (O horizon) and mineral matter horizon (M horizon) in two sites of Dabie Mountain, China, and the effects of the two horizons on the soil fungal community composition were assessed based on Illumina MiSeq sequencing. Our results showed that soil fungal community composition varied with soil horizons, and soil fungal species richness and diversity in the O horizon were significantly higher than that in the M horizon. Total organic carbon (TOC), total organic nitrogen (TON), alkali-hydrolyzable nitrogen (AHN), available potassium (AK), and available phosphorus (AP) significantly influenced fungal community composition, abundance, and diversity across the two horizons (P < 0.05). Furthermore, precipitation was found to have a significant effect on fungal community composition. Our results demonstrate changes in fungal communities across soil horizons and highlight the importance of soil organic matter on fungal communities and diversity.

Immobilization and stabilization of volcanic ash in soil aggregates in semiarid meadows of Northern Patagonia

Although volcanism may be perceived by the society as a phenomenon with mostly negative consequences, this is not always the case especially for natural systems. There is a limited knowledge on how the deposited pristine ash becomes immobilized and stabilized in the soil after the volcanic event. Here, we studied processes of soil aggregates formation in the buried ash layer in an early stage of the succession as well as the influence of the biological legacy (previous land management history) on these processes after the 2011 volcanic event of the Puyehue–Cordón Caulle Volcanic Complex. 5.5 years after the eruption we collected soil cores to a 10 cm depth in wet and mesic meadows with good and poor grassland conditions induced by light and heavy grazing intensity, respectively, in the East semiarid region of North Patagonia, Argentina. The ash layer was observed down to 5 cm from the soil surface, clearly differentiating a newly developed soil layer formed after the volcanic event. Accordingly, the top 5 cm were examined for the distribution of different size fractions of water-stable soil aggregates and their associated organic carbon (C) and total nitrogen (N) contents. We detected signs of physical and physicochemical changes in respect to the pristine ash collected at these sites in 2011. Soil neoformation processes were detected through the presence of large (4%) and small (21%) macroaggregates, although microaggregates (~45%) and silt + clay fractions (~29%) dominated the soil mass (ash-soil matrix: 0–5 cm depth). C and N contents decreased in a sequence: large macroaggregates ≥ small macroaggregates > microaggregates ≥ silt + clay, highlighting the importance of soil organic matter in the formation of larger-size aggregates and their quality (C and N contents). Biological legacy influenced soil aggregate formation and their quality, as reflected by a higher mass of small macroaggregates and a lower mass of microaggregates (only in mesic meadows) and by higher C and N contents under good grassland conditions. The seasonal hydrological conditions of meadow soils (i.e., soil water content, wetting and drying cycles) via effects on biological and physical processes likely resulted in a reduced aggregation in wet meadows. We noticed an incipient but present soil aggregation processes in these semiarid wetlands translated in the immobilization and stabilization of the buried ashes in the soil. The total C content in the new 0–5 cm soil layer increased at a rate of 1.0 Mg C ha−1 yr−1, on average. This indicates a functional recovery of the ecosystem along with a substantial CO2 mitigation potential in the ashes stabilized with soil organic matter, which might partially counterbalance CO2 emitted during the eruption.

How Soil Pore Distribution Could Help in Soil Quality Studies as an Appropriate Indicator

The present study is aimed at examining the impacts of land use and slope gradient on pore space distribution as well as some soil physicochemical properties. Three land uses were considered in this research: natural forest lands, degraded forest lands, and cultivated lands as dry farming. The study area was divided into four slope classes. Furthermore, two types of soil surface (0–10 cm) sampling were performed: a) soil samples for physicochemical analysis and b) intact samples for thin section preparation and image analysis to extract pore equivalent diameter distribution. Pore diameters were divided into three classes, including macropores, mesopores, and micropores. One hundred and eight soil surface samples were collected from the study area. The results revealed that macropores and mesopores are predominant in the natural forest soils, while micropores are dominant in the cultivated soils. Moreover, the highest contents of soil organic matter (SOM) and cation exchangeable capacity and the lowest value of bulk density are observed in the natural forest soils. Regression analysis revealed a positive regression between SOM and macropores and mesopores and a negative regression between organic matter and micropores. These results indicated the importance of SOM in the formation of macropores and mesopores. It appears that plowing cultivated lands has led to the exposure and decay of SOM. In addition, agricultural machinery traffic affects soil compaction, both resulting in the formation of micropores. Overall, soil pore distribution has the essential sensitivity to detect changes in soil quality due to land use changes or other operations.

Transport and retention of perfluorooctanoic acid (PFOA) in natural soils: Importance of soil organic matter and mineral contents, and solution ionic strength

Effects of soil organic matter and mineral contents, and solution ionic strength on the transport of perfluorooctanoic acid (PFOA) in different types of soils (i.e., desert soil, black soil, and red soil) were systematically investigated with a set of laboratory column experiments. The retention of PFOA in the soils under two solution ionic strengths conditions (1.0 mM and 10.0 mM CaCl2) followed an order of red soil > black soil > desert soil (expect red soil in 10 mM CaCl2). PFOA retention in the black soil (soil organic carbon content: 2.57%) was higher than that in the desert soil (soil organic carbon content: 0.05%). In addition, PFOA also showed higher mobility in treated black soils with lower organic carbon contents. These results suggest that the hydrophobic interaction is a key mechanism governing PFOA retention and transport in soils. Besides, more PFOA retention in the red soil (zeta potential: 7.25 ± 0.10 mV and 14.80 ± 0.20 mV) than the desert soil (−15.70 ± 0.10 mV and − 9.11 ± 0.10 mV) was observed, suggesting that electrostatic interaction may be another important mechanism for PFOA retention and transport in soils. Increasing ionic strength slightly increased the retention of PFOA in negatively charged desert and black soils, but significantly decreased the retention of PFOA in the positively charged red soil. Findings of this study point to the importance of soil physiochemical properties to the fate and transport of PFOA in natural soils.

Role of Biochar and Fungi on PAH Sorption to Soil Rich in Organic Matter

The use of biochar (BC) has been suggested for remediation of contaminated soils. This study aims to investigate the role of microorganisms in sorption of PAH to BC-amended soils. Fungi, especially the wood and litter-degrading fungi, have shown the ability for humification and to degrade recalcitrant molecules, and are thus suitable model organisms. Haplic Arenosol with high organic matter content was chosen to highlight the importance of soil organic matter (SOM) in PAH sorption, possibly to form non-extractable residue. Basidiomycetous fungi Agrocybe praecox and Phanerochaete velutina grown on pine bark were inoculated in organic matter (OM)-rich Haplic Arenosol and OM-poor sandy loam with either BC or chemically activated BC (ABC) and 14C-labelled pyrene for 60 days. Fungi did not mineralize pyrene, but increased sorption up to 47–56% in BC-amended Haplic Arenosol in comparison with controls (13–25%) without a fungus irrespective of the presence of an adsorbent. In OM-poor sandy loam, only 9–12% of pyrene was sorbed to amended soil in the presence of fungus and adsorbent. The results suggest that BC and fungal amendment increased sorption of pyrene, especially to Haplic Arenosol more than by either BC or fungi alone.

Nanoscale Titanium Dioxide (nTiO2) Transport in Natural Sediments: Importance of Soil Organic Matter and Fe/Al Oxyhydroxides.

Many engineered nanoparticle (ENP) transport experiments use quartz sand as the transport media; however, sediments are complex in nature, with heterogeneous compositions that may influence transport. Nanoscale titanium dioxide (nTiO2) transport in water-saturated columns of quartz sand and variations of a natural sediment was studied, with the objective of understanding the influence of soil organic matter (SOM) and Fe/Al-oxyhydroxides and identifying the underlying mechanisms. Results indicated nTiO2 transport was strongly influenced by pH and sediment composition. When influent pH was 5, nTiO2 transport was low because positively charged nTiO2 was attracted to negatively charged minerals and SOM. nTiO2 transport was slightly enhanced in sediments with sufficient SOM concentrations due to leached dissolved organic matter (DOM), which adsorbed onto the nTiO2 surface, reversing the zeta potential to negative. When influent pH was 9, nTiO2 transport was generally high because negatively charged medium repelled negatively charged nTiO2. However, in sediments with SOM or amorphous Fe/Al oxyhydroxides depleted, transport was low due to pH buffering by the sediments, causing attraction between nTiO2 and crystalline Fe oxyhydroxides. This was counteracted by DOM adsorbing to nTiO2, stabilizing it in suspension. Our research demonstrates the importance of SOM and Fe/Al oxyhydroxides in governing ENP transport in natural sediments.

Temperature-dependent oxide removal from manganese- and iron oxide-coated soil redox bars

Soil temperature is a fundamental parameter affecting not only microbial activity but also manganese (MnIII,IV) and iron (FeIII) oxide reduction rates. The relationship between MnIII,IV oxide removal from oxide-coated redox bars is missing at present. This study investigated the effect of variable soil temperatures on oxide removal by MnIII,IV and FeIII oxide-coated redox bars in water-saturated soil columns in the laboratory. The Mn coatings contained the mineral birnessite, whereas the Fe coatings contained a mixture of ferrihydrite and goethite. Additionally, platinum (Pt) electrodes designed to measure the redox potential (EH) were installed in the soil columns, which were filled with either a humic topsoil with an organic carbon (Corg) content of 85 g kg−1 (pH 5.8) or a subsoil containing 2 g Corg kg−1 (pH 7.5). Experiments were performed at 5, 15, and 25 °C. Although elevated soil temperatures accelerated the decrease in EH after water saturation in the topsoil, no EH decreases regardless of soil temperature occurred in the subsoil. Besides soil temperature, the importance of soil organic matter as an electron donor is highlighted in this case. Complete removal of the MnIII,IV oxide coating was observed after 28, 14, and 7 days in the soil columns filled with topsoil at 5, 15, and 25 °C, respectively. Along the Fe redox bars, FeIII reducing conditions first appeared at 15 °C and oxide removal was enhanced at 25 °C because of lower EH, with the preferential dissolution of ferrihydrite over goethite as revealed by visual differences in the FeIII oxide coating. Oxide removal along redox bars followed the thermodynamics of the applied minerals in the order birnessite > ferrihydrite > goethite. In line with Van’t Hoff’s rule, turnover rates of MnIII,IV and FeIII oxide reduction increased as a result of increased soil temperatures. Taking into account the stability lines of the designated minerals, EH-pH conditions were in accordance with oxide removal. Soil temperature must therefore be considered a master variable when evaluating the oxide removal of redox bars employed for the monitoring of soil redox status.

David Stewart Jenkinson. 25 February 1928 — 16 February 2011

David Jenkinson was one of the most influential soil scientists of his generation, bringing new insights into the transformations of organic matter and nitrogen in soil. He spent the majority of his career at Rothamsted Research, Harpenden, UK. His studies were influential regarding the role of soil carbon stocks in the context of climate change and the role of nitrogen fertilizer in delivering adequate supplies of food for a growing world population. His research encompassed both fundamental studies on soil processes and immensely practical applications of this knowledge, often utilizing the Rothamsted long-term experiments that have run for over 170 years. He is particularly well known for his development of a method for determining the quantity of organic carbon held in the cells of living micro-organisms in soil, termed the ‘soil microbial biomass’. This breakthrough opened the way for a new wave of soil biological research. David developed one of the earliest computer models for the turnover of organic carbon in soil, known as the Rothamsted Carbon Model, RothC. This model, conceptually very simple, has proved highly successful in simulating and predicting changes in soil organic carbon (SOC) content under different management practices worldwide, being used by over 2600 people in 115 countries. His research using the stable isotope of nitrogen, 15 N, in large-scale field experiments drew attention to the factors leading to inefficiencies in the use of nitrogen fertilizer but also demonstrated that it is possible to achieve high efficiency if good agricultural management practices are followed. It also demonstrated, more clearly than previously, the great importance of soil organic matter as a source of nitrogen for crops and the role of the soil microbial biomass both in immobilizing a proportion of applied fertilizer nitrogen and also in causing confusion in the interpretation of such experiments. By calculating nitrogen budgets for the Rothamsted long-term experiments he quantified the deposition of nitrogen compounds from atmosphere to land, laying foundations for later studies concerning the ecological and agricultural impacts of this significant input of nitrogen.

Studying the importance of soil organic matter: An educational proposal for secondary education

Although the importance of including in the curriculum of all educational levels issues related to soil science has been strongly highlighted, the fact is that the importance that the quality and availability of organic matter in the quality of soil have received very little attention when it comes to considering educational practices in classrooms. This paper brings an educational proposal for teaching the transcendence of organic matter in soil at secondary level. The learning unit presented is based on essential chromatography techniques and allows the qualitative study of soil organic matter. The ultimate purpose is to offer basic educational tools for reflection on the implication that soil has in order to maintain biodiversity and food production.

중적외선분광분석법을 이용한 토양 유기 탄소 분획 분석

기후변화 문제와 관련하여 탄소 격리와 토양 유기물의 중요성에 대한 관심이 증가하고 있다. 토양 탄소 격리를 산정하기 위해서는 물 추출 토양 유기탄소(WESOC)와 토양 호흡에 의해 이산화탄소로 배출되는 탄소량과 같은 토양 유기탄소를 분석하는 것이 중요하다. 이러한 성분의 분석에는 시간이 많이 소요된다. 따라서 본 연구에서는 분석시간이 짧게 소요되는 중적외선분광분석법으로 물 추출 유기탄소와 토양 호흡에 의한 이산화탄소량을 분석할 수 있는 가능성을 알아보았다. 토양을 <TEX>$100^{\circ}C$</TEX>와 <TEX>$350^{\circ}C$</TEX> 건조오븐에서 처리하고 중적외선분광계로 분석하여 WESOC와 30일, 60일, 90일, 120일 간 토양호흡에 의해 발생하는 이산화탄소량과의 상관을 분석하였다. 물 추출 토양 유기탄소에 대한 예측 모델에서는 표준 일반 변수화(SNV) 전처리를 통해 0.6937의 결정 계수를 보였고 30일간의 토양 호흡 발생 이산화탄소 예측 모델에서는 <TEX>$350^{\circ}C$</TEX> 건조 토양에 대해 1차 도함수 전처리를 통해 0.8933의 결정 계수를 보여 중적외선분광분석법을 사용하여 토양 중 유기탄소의 분획별 정량에 사용할 수 있는 가능성을 보였다. For concerning the climate change issues, the carbon sequestration and importance of soil organic matter are receiving high attention. To evaluate carbon sequestration in soil is important to determine the soil organic carbon (SOC) fractions such as WESOC (Water extractable soil organic carbon), and <TEX>$CO_2$</TEX> emission by soil microbial respiration. However, the analyses for those contents are time-consuming procedure. There were studied the feasibility of MIRS (Mid-Infrared Spectroscopy), which has short analysis time for determining the WESOC and an incubated carbon in this study. Oven-dried soils at <TEX>$100^{\circ}C$</TEX> and <TEX>$350^{\circ}C$</TEX> were scanned with MIRS and compared with the chemically analyzed WESOC and cumulative carbon dioxide generated during 30, 60, 90, and 120 days of incubation periods, respectively. It was observed that an optimized determination coefficient was 0.6937 between WESOC and untreated soil processed by spectrum vector normalization (SNV) and 0.8933 between cumulative <TEX>$CO_2$</TEX> from 30 days incubation and soil dried at <TEX>$350^{\circ}C$</TEX> after subtracting air-dried soil processed by 1st derivatives. Therefore, it was shown that Quantification of soil organic carbon fractions was possibility to be analyzed by using MIRS.

Leaching of copper and nickel in soil-water systems contaminated by bauxite residue (red mud) from Ajka, Hungary: the importance of soil organic matter.

Red mud is a highly alkaline (pH >12) waste product from bauxite ore processing. The red mud spill at Ajka, Hungary, in 2010 released 1 million m3 of caustic red mud into the surrounding area with devastating results. Aerobic and anaerobic batch experiments and solid phase extraction techniques were used to assess the impact of red mud addition on the mobility of Cu and Ni in soils from near the Ajka spill site. Red mud addition increases aqueous dissolved organic carbon (DOC) concentrations due to soil alkalisation, and this led to increased mobility of Cu and Ni complexed to organic matter. With Ajka soils, more Cu was mobilised by contact with red mud than Ni, despite a higher overall Ni concentration in the solid phase. This is most probably because Cu has a higher affinity to form complexes with organic matter than Ni. In aerobic experiments, contact with the atmosphere reduced soil pH via carbonation reactions, and this reduced organic matter dissolution and thereby lowered Cu/Ni mobility. These data show that the mixing of red mud into organic rich soils is an area of concern, as there is a potential to mobilise Cu and Ni as organically bound complexes, via soil alkalisation. This could be especially problematic in locations where anaerobic conditions can prevail, such as wetland areas contaminated by the spill.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-015-4282-4) contains supplementary material, which is available to authorized users.

Analytical pyrolysis as a tool to probe soil organic matter

The environmental importance of soil organic matter (SOM) in the ecosystems and in the C biogeochemical cycle is well established. Indeed, it represents the main terrestrial carbon pool and due to its vulnerability, it plays a key role in the global carbon cycle. However, as SOM is mainly composed of products resulting from microbial and physicochemical transformations of vegetal, microbial and animal biomass, it results in a heterogeneous mixture. This complexity, along with organo-mineral interactions, makes challenging the characterization of SOM composition at the molecular scale. Nevertheless, its precise characterization is essential to determine its fate in the environment and eventually to provide recommendations on sustainable practices. Among the available techniques to analyse SOM, thermal degradations appear as especially efficient as they are less selective than some chemical ones, leading to a larger view of the SOM chemical structure. Analytical pyrolysis was thus used in a wide range of soil science fields including studies on pedogenesis and anthropic effects. It allows to characterize SOM at the molecular level, including identification of biomarkers, and to compare different soils and/or different horizons in a given soil profile under various impacts (land use, evolution, etc.). The review of recent developments in data acquisition and/or processing leads us to provide guidelines to select the most appropriate method and to avoid possible pitfalls. Examples will illustrate the wide range of soil science applications and show the potential and limitations of this approach.

Importance of soil organic matter for the diversity of microorganisms involved in the degradation of organic pollutants

Many organic pollutants are readily degradable by microorganisms in soil, but the importance of soil organic matter for their transformation by specific microbial taxa is unknown. In this study, sorption and microbial degradation of phenol and 2,4-dichlorophenol (DCP) were characterized in three soil variants, generated by different long-term fertilization regimes. Compared with a non-fertilized control (NIL), a mineral-fertilized NPK variant showed 19% and a farmyard manure treated FYM variant 46% more soil organic carbon (SOC). Phenol sorption declined with overall increasing SOC because of altered affinities to the clay fraction (soil particles <2 mm in diameter). In contrast, DCP sorption correlated positively with particulate soil organic matter (present in the soil particle fractions of 63-2000 μm). Stable isotope probing identified Rhodococcus, Arthrobacter (both Actinobacteria) and Cryptococcus (Basidiomycota) as the main degraders of phenol. Rhodococcus and Cryptococcus were not affected by SOC, but the participation of Arthrobacter declined in NPK and even more in FYM. (14)C-DCP was hardly metabolized in the NIL variant, more efficiently in FYM and most in NPK. In NPK, Burkholderia was the main degrader and in FYM Variovorax. This study demonstrates a strong effect of SOC on the partitioning of organic pollutants to soil particle size fractions and indicates the profound consequences that this process could have for the diversity of bacteria involved in their degradation.

Insights and Lessons Learned From the Long-term Rehabilitation of an Iron ore Mine

A long-term study was conducted between 1985 and 2003 on rehabilitation trials at Sishen IronOre Mine, South Africa, to identify grass species that would survive in the artificial growth medium appliedto the sites, and to determine the most suitable medium for sustainable vegetation growth. Vegetationestablishment was tested at slopes of 18° and 34° and with five different cover materials. After 17 years ofrehabilitation, investigations showed that weathered limestone sloped at 18° produced the highest percentage of plant cover and least erosion. Sixteen grass species were introduced and identified in the survey, with Eragrostis sp. and Cenchrus ciliaris as the dominant species. In 2004, new trials were initiated at the same mine to evaluate the effectiveness of different seeding methods and supplementation of the growth medium with organic material. After 4 years, hydro seeding was found to be the best method to distribute seeds evenly and to ensure uniform vegetation growth. Different engineering designs, such as changing the contour length and slope, had little influence on the measured parameters. A total of 28 grass species were identified in the sampling plots, with Enneapogon cenchroides and Cenchrus ciliaris as the dominant ones. Dehydrogenase activity was used as a proxy for microbial activity, and a positive association was observed between microbial activity and percentage organic carbon, emphasising the importance of soil organic matter in the soil development process.

Propriedades de solos sob vegetação nativa em Minas Gerais: distribuição por fitofisionomia, hidrografia e variabilidade espacial

A distribuição das formações vegetais nativas depende dos fatores de formação do solo, entre outros aspectos. Dessa forma, solos sob vegetação nativa podem informar muito sobre uma região e sua fertilidade natural, constituindo um testemunho das condições encontradas antes da ocupação agrossilvopastoril. O objetivo deste estudo foi avaliar propriedades químicas e textura dos solos sob fragmentos de Cerrado e florestas nativas amostrados durante o Inventário Florestal de Minas Gerais, por meio de análises de fertilidade do solo, textura e estatística espacial. Em geral, houve grande variabilidade em todas as propriedades analisadas, exceto em Al trocável. Os solos sob Campo Cerrado apresentaram maiores teores de matéria orgânica, comparados aos sob Cerradão e Cerrado stricto sensu. As Florestas Estacionais ocorreram, em geral, em solos de melhor fertilidade natural do que aqueles sob Cerrado, enquanto as florestas sob clima chuvoso ocorreram nos solos mais ácidos e com maiores teores de matéria orgânica, entre todas as fitofisionomias. Análises de regressão linear indicaram que a importância da matéria orgânica na CTC a pH 7,0 variou entre as diferentes fitofisionomias, sendo não significativa para as Florestas Deciduais. A estratificação por bacias hidrográficas, interpretada em conjunto com a fitofisionomia, permitiu também concluir sobre um provável efeito dos materiais de origem nas propriedades do solo, especialmente a textura. Por meio de análise geoestatística, foi possível construir, por krigagem ordinária, mapas do Estado com a distribuição de teores de carbono orgânico do solo, argila e pH, mas não para CTC a pH 7,0. A análise de solos sob fragmentos de vegetação nativa oferece potencial para uso como referência do padrão de fertilidade natural dos solos e é uma iniciativa que poderia ser empreendida em outras unidades da federação.