Organo Mineral Research Articles

Proportions of mineral and organomineral fertilizers in onion cultivation

Organomineral fertilizers is an innovation in agriculture, since it uses organic matter enriched with minerals. The combination of mineral phosphate and organomineral fertilization can contribute to the development of a more sustainable and economical fertilization program for the crop. So, organomineral fertilization can be an alternative or complement to mineral fertilization. However, the careful selection of fertilizer sources and doses is essential to increase productivity in the onion crop and finding proportions between different fertilizers can be a promising choice for sustainable agriculture. The aim of the present research was to evaluate the effect of different proportions of mineral and organomineral fertilizers on the development, production and post-harvest quality of onion bulbs, cv. Sublime F1, under Cerrado conditions. The experiment was carried out in the field, in Cristalina, GO, Brazil, in a randomized block design, with four replications. Six treatments were used: five proportions of mineral fertilizer (M) with organomineral (OM) and the control (without additional fertilization). It was evaluated: length, width and number of leaves; productivity; soluble solids content; titratable acidity; and loss of fresh mass. Data were submitted to analysis of variance (ANOVA), at 1% (p≤0.01) and 5% (p≤0.05) of significance, and means compared by Tukey and Dunnett tests (p≤0.01 and p≤0.05). The fertilization proportions were submitted to regression (p≤0.05). The proportion of 50%M50%OM promotes higher bulb average mass and class 4 onion productivity. The proportions of fertilizers did not alter the postharvest characteristics (total soluble solids and total acidity) of the onion, which were affected only by the time of storage. Cultivar Sublime F1 showed good development for the region, conditions and fertilizers used.

Organo-organic interactions dominantly drive soil organic carbon accrual.

Organo-mineral interactions have been regarded as the primary mechanism for the stabilization of soil organic carbon (SOC) over decadal to millennial timescales, and the capacity for soil carbon (C) storage has commonly been assessed based on soil mineralogical attributes, particularly mineral surface availability. However, it remains contentious whether soil C sequestration is exclusively governed by mineral vacancies, making it challenging to accurately predict SOC dynamics. Here, through a 400-day incubation experiment using 13 C-labeled organic materials in two contrasting soils (i.e., Mollisol and Ultisol), we show that despite the unsaturation of mineral surfaces in both soils, the newly incorporated C predominantly adheres to "dirty" mineral surfaces coated with native organic matter (OM), demonstrating the crucial role of organo-organic interactions in exogenous C sequestration. Such interactions lead to multilayered C accumulation that is not constrained by mineral vacancies, a process distinct from direct organo-mineral contacts. The coverage of native OM by new C, representing the degree of organo-organic interactions, is noticeably larger in Ultisol (~14.2%) than in Mollisol (~5.8%), amounting to the net retention of exogenous C in Ultisol by 0.2-1.3 g kg-1 and in Mollisol by 0.1-1.0 g kg-1 . Additionally, organo-organic interactions are primarily mediated by polysaccharide-rich microbial necromass. Further evidence indicates that iron oxides can selectively preserve polysaccharide compounds, thereby promoting the organo-organic interactions. Overall, our findings provide direct empirical evidence for an overlooked but critically important pathway of C accumulation, challenging the prevailing "C saturation" concept that emphasizes the overriding role of mineral vacancies. It is estimated that, through organo-organic interactions, global Mollisols and Ultisols might sequester ~0.1-1.0 and ~0.3-1.7 Pg C per year, respectively, corresponding to the neutralization of ca. 0.5%-3.0% of soil C emissions or 5%-30% of fossil fuel combustion globally.

Monitoring of Seasonal Under-Vine CO2 Effluxes in a Vineyard under Different Fertilization Practices

Soil CO2 efflux is a pivotal component of agro-ecosystem C budgets. It is considered a proxy indicator of biological activity and a descriptor of soil quality that is strongly linked to agricultural soil management. We investigated the effects of soil fertilization practices (organo-mineral (OMN) versus chemical (C)) on soil under-vine CO2 efflux (TSR) in an Italian rainfed vineyard (cv Chardonnay). The TSR was measured using the chamber technique as follows: a close multi-chamber system (prototype) was placed under a vine. Data (CO2, temperature, and moisture) were acquired hourly during two consecutive years (2021 and 2022) from flowering to berry ripening. Physical–hydrological soil parameters were determined, and the seasonal trends of the TSR, soil temperature, and soil moisture were assessed. The TSR measurements fluctuated for the 2021 season, ranging from 1.03 to 1.97 µmol CO2∙m−2∙s−1 for the C treatment, while for the OMN treatment, the TSR measurements ranged from 1.24 to 1.71 µmol CO2∙m−2∙s−1. Extreme weather conditions (2022) highlighted the differences between the two agronomical practices, and a decoupling was found between the TSR and the soil water content, with the TSR being controlled primarily by the soil temperature. At the daily scale, the findings showed that the TSR reached its minimum in the early morning hours (5:00–8:00). The results promote organic–mineral nutrition as an improved practice for soil carbon storage (restoration of the organic fraction) by reducing the TSR, permitting the preservation of soil quality and stabilizing the hydrological traits by preserving the biotic activities.

Effects of Fertilization Types and Base Saturation on the Growth and Water Productivity in Panicum maximum cv. BRS Zuri

Fertilization management is essential for forage production. However, excessive use of synthetic fertilizers causes environmental imbalances. An alternative to reduce these effects is to seek alternative fertilizers, such as wood ash produced from agro-industrial waste, when integrated with appropriate base saturation management. This study aims to compare the effects of fertilization with wood ash (WA), organomineral (OM), and mineral (M) fertilizers associated with different levels of base saturation on the growth and water productivity of Panicum maximum cv. BRS Zuri. The experiment was conducted in a greenhouse, using a randomized block design in a 3 × 3 factorial arrangement. The treatments consisted of three types of fertilization (WA, OM and M) and three levels of base saturation (0, 25%, and 50%). Leaf area, chlorophyll index, shoot dry mass and root dry mass, water consumption, and water productivity of Zuri grass were evaluated. The results showed significant increases in leaf area, with values of up to 4564.5 cm2.pot−1 and a chlorophyll index of up to 36.2 units. In addition, the dry mass of the aerial part reached up to 46.7 g.pot−1, and the dry mass of the roots reached 21.7 g.pot−1 with the use of OM fertilizers. These values represent an increase of between 43.1% and 69.6% compared to the values of conventional fertilizers. In addition, water productivity reached 4.9 g.L−1 with WA-based fertilizers, an increase of around 39% compared to the values of mineral fertilizers.

The functional role of earthworm mucus during aggregation

AbstractBackgroundSoil organisms influence pedogenesis on a molecular level through the production of biopolymers which interact with soil minerals depending on their molecular properties. Specifically, biopolymers impact structure formation by inhibiting aggregation as a separation agent or promoting aggregation as a bridging agent. Mucus is a biopolymer excreted by earthworms that consists mainly of proteins, polysaccharides, and, to a lesser extent, lipids. However, despite earthworms’ fundamental contribution to soil quality and structuring via bioturbation, the role of mucus in aggregation still has to be unraveled.AimsOur study explores the role of cutaneous earthworm mucus (CEM) of Lumbricus terrestris L. for the formation of organo–mineral associations and aggregates, a sub‐process of pedogenesis.MethodsWe conducted batch experiments with goethite and CEM at different pH values and varying CEM concentrations to form mucus–goethite associations. Employing the newly formed mucus–goethite associations, we explored the (homo‐/hetero‐)aggregation with quartz particles as a function of the loading of surfaces with mucus‐C and CEM concentrations in solution.ResultsOur results suggest that the molecular structure of CEM constituents (especially proteins) is sensitive to pH. We found that the adsorption of CEM to goethite depends on pH and concentration. Polysaccharides of CEM adsorbed preferentially under acidic conditions (pH 3) and at low CEM concentration (6 mg mucus‐C L–1). In contrast, stronger adsorption of proteins was observed at higher CEM concentrations (30 mg mucus‐C L–1). In subsequent aggregation experiments, the hetero‐aggregation rate of organo–mineral associations and quartz decreased at low C‐loadings. Conversely, the rate increased at high loadings compared to the CEM‐free reference. Furthermore, electrostatic/steric repulsion (separation agent) inhibited the aggregation between goethite particles at high CEM concentrations in the solution (mineral/mucus ratio of 17). However, at a low CEM supply (mineral/mucus ratio of >83), CEM took the role of a bridging agent.ConclusionsThe composition, function, and (im‐)mobilization of CEM and corresponding organo–mineral associations in earthworm‐influenced soil structures are shaped by the structure/reactivity of CEM affected by environmental parameters. Formation and aggregation of mucus–mineral associations contribute to nutrient/carbon storage and are involved in the structure formation in soil.

Effectiveness of modified nitrogen fertilizer on soil chemical properties and rice plant growth in the textile industrial area

The imbalance of nutrients and heavy metal contamination is a challenge in increasing plant growth surround the textile industry area. This study aimed to determine the effectiveness of the dosage of Biologically Agent N Organo Mineral Fertilizer (Biomix-N) as a fertilizer and an ameliorant in paddy soil contaminated with textile liquid waste. This study used a randomized block design of eight treatments with four replications. Parameters observed were soil chemical properties after application of Biomix-N (Na-ex, total N, EC, Cd, and pH), rice plant growth (plant height and tiller number), Cd concentration in the plant, and relative agronomic effectiveness (RAE). Data analysis used analysis of variance, Duncan's test at a 5% level, regression, and correlation analysis. The results showed that Biomix-N 500 kg ha-1 affected the value of EC and total N, while it did not affect Na-ex, Cd, pH and Cd uptake by the paddy plant. Biomix-N fertilization affects the height and number of tillers of rice plants at the age of 70 DAP. Biomix-N fertilization 500 kg ha-1 gave an RAE value of 126-176% compared to the control treatment. The total N content of the soil has a high value of coefficient determinant and correlation (R2= 0.76; R = 0.9) on the growth of rice plants. Applying Biomix-N 500 kg ha-1 equal to 300 kg ha-1 of urea was an effective dose for paddy soil surround the textile industrial area.Keywords: Cadmium, nutrient balance, soil amendment

Chemical and Structural Insights of the Nano Organo–Mineral Interfaces in Growing Abalone Nacre

Chemical and Structural Insights of the Nano Organo–Mineral Interfaces in Growing Abalone Nacre

Using organo–mineral complex material to prevent the migration of soil Cd and As into crops: An agricultural practice and chemical mechanism study

The migration and transformations of Cd and As in soil are different, so it is difficult to simultaneously control them. In this study, an organo–mineral complex (OMC) material was prepared using modified palygorskite and chicken manure, the Cd and As adsorption capacities and mechanism of the OMC were explored, and the response of the crop to the OMC was clarified. The results show that the maximum Cd and As adsorption capacities of the OMC under pH values of 6–8 are 12.19 mg·g−1 and 5.07 mg·g−1, respectively. In the OMC system, the modified palygorskite contributed more to the adsorption of the heavy metals than the organic matter. Cd2+ may form CdCO3 and CdFe2O4, and AsO2− may form FeAsO4, As2O3, and As2O5 on the surfaces of the modified palygorskite. Organic functional groups such as hydroxyl, imino, and benzaldehyde groups can participate in the adsorption of Cd and As. The Fe species and carbon vacancy in the OMC system promote the conversion of As3+ into As5+. A laboratory experiment was conducted to compare five commercial remediation agents with OMC. Planting Brassica campestris in the OMC remediated soil with excessive contamination increased the crop biomass and decreased the Cd and As accumulation sufficiently to meet the current national food safety standards. This study emphasizes the effectiveness of OMC in preventing the migration of Cd and As into crops while promoting crop growth, which can provide a feasible soil management strategy for CdAs co-contaminated farmland soil.

Experimental studies of the strength of fine-grained concrete with implementations of organomineral additives

Experimental studies of the strength of fine-grained concrete with implementations of organo mineral additives were carried out. The organo mineral additive in the amount of 5-15% by weight of cement has a significant effect on the strength characteristics. Zeolite-containing rock with a specific surface area of 4000 cm2/g was used in the studied compositions. The amount of water added to the mixture also increases with an increase in the amount of organo mineral additive in the concrete mixture. The introduction of an organo mineral additive as a mineral additive instead of a part of the cement promotes the pozzolanic process, in which amorphous silica (SiO2) is bound to the lime formed during cement hydration as a result of the transition to down-basic hydro silicates. The addition of zeolite-containing rocks in an amount of 5-15% by weight of cement has a significant effect on the strength characteristics. The greatest increase in compressive and flexural strength is achieved by replacing 10% cement with TPP ash (heat from a power plant). It was established that a 10% dosage of TPP ash is optimal and is used for a further selection of the composition of fine-grained concrete. The resulting mixture has increased workability and plasticity. The most optimal dosage of additives is 1-1.5%. As the second mineral additive, we used an additive of technogenic origin - microsilica, i.e. ash from burning rice husks. After studying the literature, it was concluded that the addition of microsilica in an amount of 10-12% by weight of cement most contributes to increasing the strength of concrete. The research work is aimed at improving the properties of cellular concrete, developing their composition and production technology by introducing minerals and modifying additives. The results of the research work provide an increase in manufacturability, strength, water and frost resistance, and operational reliability of the obtained materials. The joint implementation of ash and a chemical mixture into fine-grained concrete allows concluding that the strength indicators increase, and the water-cement ratio and porosity decrease.

Qualitative and Quantitative Changes in Soil Organic Compounds in Central European Oak Forests with Different Annual Average Precipitation

The various climate scenarios consistently predict warming and drying of forests in Hungary. Soils play a significant role in the long-term sequestration of atmospheric CO2, while in other cases they can also become net carbon emitters. Therefore, it is important to know what can be expected regarding future changes in the carbon storage capacity of soils in forests. We used precipitation gradient studies to solve this problem, using a type of “space–time” substitution. In this research, we primarily examined the quality parameters of soil organic matter (SOM) to investigate how climate change transforms the ratio of the main SOM compound groups in soils. For our studies, we applied elemental and 13C and 15N isotopic ratio analysis, NMR analysis, FT-IR spectra analysis, thermogravimetric and differential thermal analyses to measure SOM chemistry in samples from different oak forests with contrasting mean annual precipitation from Central Europe. Our results showed that soil organic carbon (SOC) was lower in soils of humid forests due to the enhanced decomposition processes and the leaching of Ca, which stabilizes SOM; however, in particular, the amount of easily degradable SOM compounds (e.g., thermolabile SOM, O-alkyl carbon, carboxylic and carbonyl carbon) decreased. In dry forest soils, the amount of recalcitrant SOM (e.g., thermostable SOM, alkyl carbon, aromatic and phenolic carbon and organo–mineral complexes stabilized by Ca increased, but the amount of easily degradable SOM increased further. The main conclusion of our study is that SOC can increase in forests that become drier, compensating somewhat for the decrease in forest plant biomass.

Elucidation of aniline adsorption-desorption mechanism on various organo-mineral complexes.

Complexes formed by organic matter and clay minerals, which are active components of soil systems, play an important role in the migration and transformation of pollutants in nature. In this study, humic-acid-montmorillonite (HA-MT) and humic-acid-kaolin (HA-KL) complexes were prepared, and their structures before and after the adsorption of aniline were analyzed. The aniline adsorption-desorption characteristics of complexes with different clay minerals and varying HA contents were explored using the static adsorption-desorption equilibrium method. Compared with the pristine clay minerals, the flaky and porous structure of the complexes and the aromaticity were enhanced. The adsorption of aniline on the different clay mineral complexes was nonlinear, and the adsorption capacity increased with increasing HA content. Additionally, the adsorption capacity of HA-MT was higher than that of HA-KL. After adsorption, the specific surface area of the complexes decreased, the surfaces became more complicated, and the aromaticity decreased because aniline is primarily adsorption onto the complexes via aromatic rings. Aniline was adsorbed onto the complexes via spontaneous exothermic physical adsorption. The amount of aniline desorbed from the complexes increased with increasing HA content, and a lag in desorption was observed, with a greater lag for HA-KL than for HA-MT.

Mineralogical control on physically protected soil organic matter in a neotropical moist forest

Context Minerals and organic matter physically associate in many soils, yet the precise nature, either via a hierarchy of aggregate particles or by build-up of organo–mineral associations, remains obscure, especially in tropical forest environments. Aims We investigated physically protected organic matter by comparing soils with contrasting parent material, topography, and pedogenesis, but with similar tropical moist forest on Barro Colorado Island in the lowlands of Panama. Methods Bulk soil from 10 sites was separated by size into free-floating particles, macroaggregates (>250 μm), microaggregates (53–250 μm), and <53-μm particles. A subsample of macroaggregates was disintegrated and separated into coarse particles (>250 μm), occluded microaggregates, and occluded <53-μm particles. Concentrations and natural abundance of stable isotopes for carbon (C) and nitrogen (N) were determined for each fraction, and ratios (C:N, stable isotopes) were used to characterise organic matter for each fraction. Key results Macroaggregates were the largest fraction of bulk soil (71%) and were 15% greater in kaolinite- than smectite-dominated soils. Macroaggregates were composed of coarse particles (14%), occluded microaggregates (62%), and occluded <53-μm particles (24%). Concentrations of C and N widely varied among fractions but the variation was not related to clay mineralogy. The C:N ratio and stable N isotope ratio indicated more decomposed organic matter in kaolinite- than smectite-dominated soils. Conclusions and implications Macroaggregates composed of plant detritus and microaggregates in the Barro Colorado Island soils imply that the aggregate hierarchy route ultimately protects soil organic matter in this tropical forest environment.

Effects of organo-mineral fertilization on plant growth and grain yield of an upland rice variety (NERICA 14) in lower Casamance (South-West Senegal)

In Casamance, upland rice is generally practiced on sandy soils very low in organic matter with low yields (1 to 2 tons/ha). The objective of this experiment is to evaluate the effects of different doses of organic and mineral fertilizers on the growth and yield of upland rice. The test was conducted at the ISRA Djibélor station following a Fisher block design with 4 replications. The study factor is organo mineral fertilization with 9 treatments (T1 Unfertilized control; T2 = 0 kg/ha Compost (C) + 100 kg/ha NPK + 75 kg/ha Urea; T3 = 0 kg/ha C + 200 kg/ha NPK + 150 kg/ha Urea; T4 = 2.5 t/ha; T5 = 2.5 t/ha C + 100 kg/ha NPK + 75 kg/ha Urea; T6 = 2.5 t/ha C + 200 kg/ha NPK + 100 kg/ha Urea; T7 = 5 t/ha C; T8 = 5 t/ha C + 100 kg/ha NPK + 75 kg/ha Urea; T9 = 5 t/ha C + 200 kg/ha NPK + 150 kg/ha Urea). The results showed that the tillering is more important with T8 (107 ± 11.49 tillers/m²) and T5 (96.5 ± 24.35 t tiller/m²). The height of the plants is greater with T6 (42.3 ± 2.6 cm) and T9 (62.9 ± 6.0 cm) at booting and with T9 at flowering (92.6 ± 4.3 cm) and maturity stage (98.4 ± 1.5 cm). Paddy grain yield (2,087 ± 1,229 kg/ha) and paddy grain size (28.3 ± 2.9 g/1000 grains) are more influenced by T8. For a sustainable improvement the productivity of upland rice, it is recommended to adopt T8 combination (5 t/ha Compost + 100 kg/ha NPK + 75 kg/ha Urea) for upland rice variety in Southwestern Senegal.

Experimental Precipitation Reduction Slows Down Litter Decomposition but Exhibits Weak to No Effect on Soil Organic Carbon and Nitrogen Stocks in Three Mediterranean Forests of Southern France

Forest ecosystems are some of the largest carbon (C) reservoirs on earth. Pinus halepensis Mill., Quercus ilex L. and Quercus pubescens Willd. represent the dominant tree cover in the Mediterranean forests of southern France. However, their contributions to the French and global forest C and nitrogen (N) stocks are frequently overlooked and inaccurately quantified and little is known about to what extent the ongoing climate change can alter these stocks. We quantified the soil organic C (SOC) and N (SN) stocks in Mediterranean forests dominated by these tree species and evaluated to what extent an experimental precipitation reduction (about −30% yearly) affects these stocks and the litter decomposition efficiency. Litter mass losses were 55.7, 49.8 and 45.7% after 24 months of decomposition in Q. ilex, Q. pubescens and P. halepensis forests, respectively, and were 19% lower under drier climatic conditions. The SOC stocks were 14.0, 16.7 and 18.5 Mg ha−1 and the SN stocks were 0.70, 0.93 and 0.88 Mg ha−1 in Q. ilex, Q. pubescens and P. halepensis forests, respectively. The shallowness and stoniness of these Mediterranean forests could explain these limited stocks. By distinguishing the organic from the organo–mineral layer, we showed 74% less SOC in the organic layer of the P. halepensis forest under drier conditions, while no difference was detected in the organo–mineral layer or in the two oak forests. This last finding deserves further investigation and points out the necessity to distinguish the organic from the organo–mineral layer to detect the first impacts of climate change on SOC stocks.

Physical and physicochemical characteristics of tomato fruits grown under different irrigation water levels and phosphorus sources and rates

Phosphorus (P) is one of the most limiting nutrients for growth and development of crops, and is important for soil fertility managements, since it affects the quality of fruits. With the hypothesis that different levels of irrigation and phosphorus fertilization interfere in the physical and physicochemical properties of tomatoes, the objective of this experiment was to verify this hypothesis and analyze the behavior of the fruits’ responses. The experiment was conducted in a greenhouse at the Hydraulic and Irrigation Laboratory of the Federal Institute of Education, Science, and Technology of the State of Goiás, in Rio Verde, Goiás, Brazil. A randomized block design was used, with a 4×2×4 split-plot arrangement and three replications, totaling 96 experimental plots. The treatments consisted of four P2O5 rates: 25%, 50%, 100%, and 200% of the recommended rate; two P sources: monoammonium phosphate (MAP) and organo-mineral (OM); and four IWL: 50%, 75%, 100%, and 125% of the field capacity. The fruits were evaluated for longitudinal (FLD) and transversal (FTD) diameters, potential hydrogen (pH), titratable acidity (TA), total soluble solid (TSS) contents, and TSS to TA ratio (TSS/TA). The effect of the interactions between the factors IWL and P rate, IWL and P source, and P rate and source were significant for FLD and FTD, TSS, TA, and TSS/TA. The effects of the interactions between IWL and P rate, and IWL and P source were significant for pH. The MAP source combined with the rate of 25% and IWL of 125% resulted in tomato fruits with larger FLD and FTD. The rate of 25% combined with IWL of 77% and 100% resulted in tomato fruits with higher TSS and pH. The OM source resulted in tomato fruits with higher TA when combined with IWL of 50%, and larger FLD when combined with IWL of 105% and 125%.
 (This article belongs to the Special Issue: Agricultural Water Management in Arid and Semi-arid Regions)

Effect of coppice conversion into high forest on soil organic C and nutrients stock in a Turkey oak (Quercus cerris L.) forest in Italy

In forest ecosystems, a variety of abiotic and biotic soil forming factors drives soil organic matter (SOM) and nutrients cycling with a profitable outcome on climate change mitigation. As a consequence, type and intensity of forest management, through its impact on carbon (C) and nutrient soil stocks, can be considered as an additional soil forming force. In this study, we investigated the influence of the coppice conversion into high forest on pedogenesis and on soil C and nutrient (N, P, Ca, Mg, and K) stocks, fifty years later the beginning of the conversion-cycle. The trial was established in a Turkey oak forest historically managed under the coppice system in central Italy. Specifically, we considered tree population density (natural evolution – control, moderate thinning, heavy thinning) where soil samples were collected according to genetic horizon to estimate C, N, and P stocks both in the forest floor and at fixed depth intervals (0–30, 30–50 and 50–75 cm). Further, the stocks of exchangeable Ca, Mg, and K were also assessed for the mineral layers. The results showed that litter and the upper layer of mineral soil (0–30 cm) contained a similar quantity of C (about 74–83 Mg ha-1), independently of the trials and no differences were observed also in the whole soil stocks (about 192–213 Mg ha−1). The comparison of the mean stocks calculated per 1-cm of thickness of organic (O), organo-mineral (OM), and mineral (M) layers, although it did not display any difference among trials (excepted for P and Mg), showed a similar capability of the organo-mineral horizons to store C and nutrients compared with the organic ones (e.g., about 6–12 Mg ha−1, 0.3–0.5 Mg ha−1 and 0.5–1.5 kg ha−1 for C, N and P, respectively). Our findings showed that thinning operated on Turkey oak coppice did not affect soil capacity to store C and nutrients. These results suggested that the forest ecosystem itself is the main soil forming force and this is consistent with the target of adopting forest management able to control the global C cycle through the storage of SOM in the mineral soil rather than in forest floor, where SOM turnover is faster.

Deconstructing the microbial necromass continuum to inform soil carbon sequestration

Abstract Microbial necromass is a large, dynamic and persistent component of soil organic carbon, the dominant terrestrial carbon pool. Quantification of necromass carbon stocks and its susceptibility to global change is becoming standard practice in soil carbon research. However, the typical proxies used for necromass carbon do not reveal the dynamic nature of necromass carbon flows and transformations within soil that ultimately determine necromass persistence. In this review, we define and deconstruct four stages of the necromass continuum: production, recycling, stabilization and destabilization. Current understanding of necromass dynamics is described for each continuum stage. We highlight recent advances, methodological limitations and knowledge gaps which need to be addressed to determine necromass pool sizes and transformations. We discuss the dominant controls on necromass process rates and aspects of soil microscale structure including biofilms and food web interactions. The relative importance of each stage of the continuum is then compared in contrasting ecosystems and for climate change drivers. From the perspective of the continuum, we draw three conclusions to inform future research. First, controls on necromass persistence are more clearly defined when viewed through the lens of the continuum; second, destabilization is the least understood stage of the continuum with recycling also poorly evidenced outside of a few ecosystems; and third, the response of necromass process rates to climate change is unresolved for most continuum stages and ecosystems. Future mechanistic research focused on the role of biotic and abiotic soil microscale structure in determining necromass process rates and the relative importance of organo–mineral and organo–organo interactions can inform necromass persistence in different climate change scenarios. Our review demonstrates that deconstructing the necromass continuum is key to predicting the vulnerability and persistence of necromass carbon in a changing world. Read the free Plain Language Summary for this article on the Journal blog.

Nano-scale investigation of organic C sequestration and distribution on Fe oxides during ferrihydrite transformation: effect of Al-substitution

Al-substitution in Fe oxides increased the sorption of aromatic C, which was dominantly bound to the outer layer of the organo–mineral interfaces as the carboxyl C was preferentially sorbed onto the surfaces of Fe oxides.

On the Adsorption Mechanism of Humic Substances on Kaolinite and Their Microscopic Structure

Soil organic matter (SOM) and various inorganic minerals represent key components of soils. During pedogenesis and due to biological activity these species interact, having a crucial impact on the formation of an aggregated soil structure with a hierarchical arrangement from nano to macro scale. In this process, the formation of organo–mineral microaggregates represents a dominant factor affecting soil functions and properties. This study focuses on the interactions between humic substances (HSs) and the mineral kaolinite as typical representatives of SOM and soil minerals. By performing classical molecular dynamics (MD) simulations on models of HSs and kaolinite, we demonstrate how two dominant but chemically different kaolinite surfaces affect the stability of HSs microaggregates. By analyzing volumetric, structural, and energetic properties of SOM–kaolinite models, we explain possible mechanisms of the formation of stable SOM–clay aggregates and show how a polarized environment affects the electrostatic interactions, stabilizing the microscopic structure of SOM–mineral aggregates. Our results showed that when stable aggregates of HSs are confined in kaolinite nanopores, their interactions with kaolinite surfaces disintegrate them into smaller subaggregates. These subaggregates are adsorbed more strongly on the polar aluminol surface of kaolinite compared to less the active hydrophobic siloxane surface.

Carbon Polygons and Carbon Offsets: Current State, Key Challenges and Pedological Aspects

Russia holds the largest store of carbon in soils, forests and permafrost grounds. Carbon, stored in a stabilized form, plays an important role in the balance of the global biogeochemical cycle and greenhouse gases. Thus, recalcitrance of soil organic matter to mineralization results in a decrease in current emissions of carbon dioxide into the atmosphere. At the same time, stabilization of organic matter in the form of humus due to organo–mineral interactions leads to the sequestration of carbon from the atmosphere into soils and biosediments. Thus, global carbon balance is essentially determined by soil cover state and stability. Currently, Russia is faced with a set of problems regarding carbon offsets and the carbon economy. One of the methods used to evaluate carbon stocks in ecosystems and verify offsets rates is carbon polygons, which are currently being organized, or are under organization, in various regions of Russia. This discussion addresses the current issues surrounding the methods and methodology of carbon polygons and their pedological organization and function.