Physical Fractionation Research Articles

Synergistic Promotion of Particulate and Mineral-Associated Organic Carbon Within Soil Aggregates After 10 Years of Organic Fertilization in Wheat-Maize Systems

How different fertilization practices modify soil organic carbon (SOC) sequestration is still unclear. Our study aimed to evaluate the changes in SOC stocks and their physical fractions after 10 years of organic and inorganic fertilization. Five treatments were established under a wheat-maize system in Northern China: control (CK), chemical fertilizer (F), straw plus chemical fertilizer (SF), manure plus chemical fertilizer (MF), and straw and manure plus chemical fertilizer (SMF). The results showed that the SOC sequestration rate at 0–20 cm depth decreased in the following order: SMF (1.36 Mg C/ha/yr) > MF (1.13 Mg C/ha/yr) > SF (0.72 C/ha/yr) > F (0.15 Mg C/ha/yr) > CK (−0.25 Mg C/ha/yr). The values indicated that straw returning and manure application were important measures to achieve the “4 per 1000” target, and the application of manure was a more effective strategy. The high input of chemical fertilizer only maintained the initial SOC level and was not a powerful C-farming practice. A minimum input of 4.93 Mg C/ha/yr was required to keep the initial SOC storage. The SOC associated with small macroaggregate (0.25–2 mm) was the most sensitive indicator for the changes of bulk SOC. In addition, the accumulation of SOC under SMF, MF, and SF treatments mainly occurred in the occluded particulate organic C (oPOC) in small macroaggregates, indicating that the physical protection of macroaggregates played a predominant role in SOC sequestration. The SMF, MF, and SF treatments also displayed higher mineral organic C (mSOC) in soil aggregates than the CK and F treatments. A transformation of oPOC towards the mSOC fraction indicated that exogenous C further shifted into stable C pools under the physical protection of soil aggregates. In conclusion, these findings confirmed the important role of straw returning and manure application in SOC accumulation and stabilization, highlighting that a combination strategy of straw + manure + chemical fertilizer had the best effect.

Changes in Physical Fractions within Soil Aggregates Under Nitrogen Reduction and Film Mulching Measures in Dryland Wheat Field

We studied the changes in various physical fractions within aggregates in the arid plateau of southern Shanxi Province, which has great significance for synergistically improving soil fertility and crop productivity in this region. Bulk soil samples were collected from 0-20 cm layers during a 7-year long-term experiment in Hongtong County, Shanxi Province. Wheat grain yields, SOC concentrations, proportions, and OC contents within soil aggregates were analyzed. OC contents included： unprotected coarse particulate organic carbon within macroaggregate （M-cPOC） and fine particulate organic carbon within macroaggregate （M-fPOC）, physically protected intra-aggregate particulate organic carbon within macroaggregate （M-iPOC）, chemically/biochemically protected mineral organic carbon within macroaggregate （M-MOC）, unprotected fine particulate organic carbon within microaggregate （m-fPOC）, physically protected intra-aggregate particulate organic carbon within microaggregate （m-iPOC）, and chemically/biochemically protected mineral organic carbon within microaggregate （m-MOC）. The treatments were ① farmer fertilization （FP）, ② nitrogen reduction monitoring and control fertilization （MF）, ③ nitrogen reduction monitoring and control fertilization plus ridge film and furrow sowing （RF）, and ④ nitrogen reduction monitoring and control fertilization plus flat film hole sowing （RF）. The results showed that compared with that in the FP treatment, MF reduced SOC concentration while maintaining wheat grain yield, RF and FH synergistically improved soil fertility and crop yield, especially for the FH with SOC concentration, and wheat grain yield increased by 8.44% and 48.86%, respectively. MF significantly reduced the content of M-cPOC, RF significantly increased the content of M-iPOC, and FH significantly increased the contents of M-fPOC, M-iPOC, M-MOC, and m-iPOC by 64.00%, 98.39%, 6.16%, and 17.48%, respectively. In addition, combined with redundancy analysis, we found that the M-iPOC fraction played a major role in increasing SOC concentration and wheat grain yield, with a contribution rate of 61.5%. Therefore, the contribution of macroaggregates to soil fertility and crop productivity was higher than that of microaggregates in the arid plateau area of southern Shanxi, and flat film hole sowing could increase the content of M-iPOC, thereby synergistically increasing SOC sequestration and wheat grain yield, which could promote this cultivation technology in the region and even in the country's arid agricultural areas.

Greater variation of soil organic carbon in limestone- than shale-based soil along soil depth in a subtropical coniferous forest within a karst faulted basin of China

Lithology strongly influences soil microbial traits and edaphic factors and in turn soil organic carbon (SOC) dynamics. However, the effect of lithology on microbial traits, edaphic factors and resulting SOC physical fractions variation along soil depth remains inadequately understood in karst faulted basin of China. This understanding is critical for improving SOC stability. By separating SOC into labile particulate organic carbon (POC) and stable mineral-associated organic carbon (MAOC) over karst limestone and non-karst shale soil in a subtropical coniferous forest, we aimed to assess potential regulatory mechanisms underlying lithology-associated SOC stability variations across soil depth by integrating soil nutrients, mineralogical characteristics, and microbial traits. We found that SOC and its fractions were higher in limestone than in shale soil, which implying vegetation restoration effects on SOC and its fractions partly depending on lithology. Additionally, we found that the effects of soil depth on SOC and its fractions were greater in limestone soils than shale soils, and the ratios of MAOC to SOC (MAOC:SOC) and MAOC to POC (MAOC:POC) show a opposite trend in response to soil depth between two the lithologies. Variation partitioning and random forest analyses revealed that among multiple factors, the variation of SOC stability assessed via MAOC:SOC was mainly explained by microbial traits than soil nutrients and mineral properties. Contrast to soil depth, structural equation modeling analyses showed that lithology was the primary factor controlling the SOC stability when microbial traits, soil nutrients and mineralogical characteristics were controlled as conditional variables. Overall, these results highlight the crucial role of lithology in regulating the SOC stability along soil depth, which improve our understanding and management of soil carbon (C) pool in karst faulted basin of southwest China.

The effect of methane addition on reacting hydrogen jets in crossflow

The combustion characteristics in a jet in crossflow configuration are numerically investigated using Large Eddy Simulation (LES) with subgrid scale modelling for partially premixed combustion. The time-averaged statistics are compared with the experimental measurements. Both the temperature and velocity comparisons show good agreement with measurements. The distribution of reaction regions of nitrogen-diluted hydrogen fuel jet is then examined in both physical and mixture fraction space. The results demonstrate that the fuel consumption in potential core, near-field and far-field regions occurs at various mixture fraction ranges. In the potential core region, reactions predominantly occur between the lean and stoichiometric mixture fraction range. This range broadens to include fuel-rich conditions in the near-field region and narrows again to fuel-lean combustion in the far-field region. With these changes in the mixture fraction range, the fractional contribution from different combustion modes also changes. A closer study of these changes reveals that the fractional contribution from the non-premixed mode is highest at the end of the potential core region. The dependency of these combustion modes on the fuel composition is studied by increasing the volume fraction of methane in the jet. This resulted in altered chemical kinetics and thereby increased the fractional contribution of the non-premixed mode, particularly in the potential core region.

Long-term different fertilization practices restructured the functional carbon pools in a paddy soil through distinct mechanisms

Fertilization is a common management practice for improving soil organic matter (SOM), which is a crucial indicator of soil fertility. Nevertheless, how long-term fertilization affects functional SOM fractions and its mechanisms remain unclear. In this study, a 12-year field experiment, initiated in 2011, was conducted in Xinzhu village, Zhejiang province, China. Four different fertilizer treatments (without any fertilizers application, Control; sole application of inorganic fertilizers, NPK; combined application of NPK with cattle manure, NPKM; and combination of NPK fertilizers and return of rice straw, NPKS) were selected in this field trial. Functional carbon (C) pools, microbial community structure and SOM composition in both topsoil (0−15 cm) and subsoil (15−30 cm) were explored using the physical and chemical fractionation, phospholipid fatty acids (PLFA) analysis and solid-state 13C-Nuclear Magnetic Resonance Spectrometry (13C NMR) assays. Compared to the control, the NPK combined with organic amendments had significantly higher organic carbon contents of unprotected pools (cPOM and fPOM) in both topsoil (39−277 %) and subsoil (43.1−91.3 %), respectively. Organic carbon accumulated the most within iPOM (1.99 g kg−1 soil) and H-d(Silt+Clay) fractions (1.41 g kg−1 soil) under NPKM in the topsoil, suggesting that physical and chemical protection played the pivotal role after manure addition. Furthermore, NPKM increased the abundance of bacterial and fungal PLFAs in both topsoil (31.4 % and 24.5 %) and subsoil (173 % and 175 %), while NPKS elevated the alkyl/O-alkyl C ratio but reduced the aromaticity in topsoil, compared to inorganic fertilization alone. Partial least squares path modelling showed that fertilization had a direct impact on silt+clay associated C (0.6) in topsoil, POM-C (0.76) in subsoil, and microbial community structure (0.88 and 0.87) in both soil layers. Redundancy analysis revealed that in the NPKM treatment, the key factors affecting functional carbon pools were the total PLFA and the ratio of gram-positive to gram-negative bacterial PLFA, while for the NPKS treatment, it was the alkyl C/O-alkyl C ratio. In conclusion, long-term fertilization had a strong effect on functional carbon fractions through multiple mechanisms in different soil layers, involving changing microbial community and SOM composition.

A theoretical and experimental investigation of continuous oil–water gravity separation

In this study, we have developed a mathematical model for a three-phase separator. The model consists of two sections: the inlet section and the separation section, separated by a perforated calming baffle. In the inlet section, two dispersion layers undergo droplet size evolution due to turbulent breakage and coalescence, described by a spatially homogeneous PBE. In the separation section, the two dispersion layers flow alongside each other and interact at an interface. The volumetric flow and velocity profiles are influenced by interfacial coalescence, with considerations for plug and laminar flow assumptions. The model incorporates droplet gravity-driven transport using the Kumar and Hartland model, binary and interfacial coalescence employing a film drainage model, and an effective diffusion term to account for the formation of the dense packed layer which ensures a physical volume fraction range of 0–1. Steady-state and transient numerical solvers are developed to solve the resulting advection–diffusion equations. Additionally, a series of experiments were conducted using a lab-scale multi-parallel pipes separator to investigate the impact of varying volume fractions and flow rates on the separation efficiency of the equipment. The model results are compared with the experimental data which shows relatively good agreement.

A spectral mixture analysis based framework for estimating and charactering water use efficiency in heterogeneous drylands

Climate change and irrational land utilization have significantly disrupted the function and structure of the dryland ecosystems, leading to tremendously potential effects on the carbon and water cycles of the global terrestrial ecosystems. Ecosystem-scale water use efficiency (WUE) is a crucial metric that defines the ratio of gross primary productivity (GPP) to evapotranspiration (ET), revealing the coupling relationship between such two ecological processes and playing a significant role in water resource management decision-making. However, quantifying WUE in drylands remains a challenge because of their heterogeneous land surface challenging to characterize model parameters using traditional remote sensing techniques. Here, we developed a process-based framework to estimate GPP and ET, as well as WUE based on physical endmember fractions from spectral mixture analysis (SMA) model. And such framework is used to quantify the spatial and temporal evolution of WUE by optimizing the light use efficiency and assisting in the construction of a GV-Cws model for the separation of transpiration and evaporation processes during computation by utilizing the physically fractional vegetation and soil obtained from SMA in the Hexi Corridor of China, a typical dryland ecosystem. The results demonstrate that our framework can accurately estimate GPP and ET in the Hexi Corridor, as indicated by favorable performance in R2 (0.669, 0.705), RMSE (0.383,0.885) and NSE (0.534, 0.690) respectively. Such results surpass the accuracy of both two Moderate Resolution Imaging Spectroradiometer (MODIS) products and Penman-Monteith-Leuning Evapotranspiration V2 (PML_V2)’s ET product. These advantages highlight that our SMA-based framework can provide highly accurate and distinct characterization of surface carbon and water interaction processes. Meanwhile, the WUE of the Hexi Corridor ecosystem exhibited a positive trend from 2001 to 2017 (0.016 gC·m−2·mm−1·a-1), characterized by simultaneous increases in GPP and ET.

Soil carbon stabilization of mining-degraded, reforested lands in southern Ontario

We took advantage of the northern forest near Sudbury, Ontario, Canada where logging and metal-mining pollution had degraded the landscape prior to it being restored and reforested to investigate how soil organic matter is stabilized with stand age in highly ‘eroded’ sites with minimal residual soil and in ‘stable’ sites with residual soil. Soil organic matter in sandy, acidic soils of the northern forest is thought to be stabilized in organo-mineral particles (<20 μm in size); however, forest disturbance and soil erosion might help to promote less-decomposed plant detritus being stabilized within aggregate structures (53 μm in size). We use a combination of physical fractionation (size) and chemical analysis (carbon to nitrogen ratio, natural abundance of stable isotopes of carbon and nitrogen) of the fractions. The composition of bulk soils with young trees (15-yr old) was 25% microaggregates (53 to 250 μm in size) and 47% in a smaller silt + clay fraction (<53-μm in size). Bulk soil with older trees (28- and 30- to 32-yr old) had equal proportions of macroaggregates (>250 μm in size), microaggregates, and silt + clay fraction. The C density was much greater and less decomposed for macroaggregates than for the silt + clay fraction. Untreated sites, with trees but not restored with added lime, had a smaller proportion of macroaggregates in bulk soil. Even though aggregate structures typically are not associated with sandy, acidic forest soils, the results for these Regosols in the northern forest of the Greater Sudbury region show that stabilized soil C involves formation of macroaggregates along with microaggregates, both of which help to stabilize particulate organic matter.

The role of flexural particles in the shear flow of pine residue biomass: An experiment-informed DEM simulation study

An experiment-informed discrete particle simulation study was performed to investigate the role of flexural particles in the shear flow of milled pine residues. Physical pine anatomical fraction samples were tested in an FT4 powder rheometer. A chip model for bark/stem chips and a fiber model for needles were proposed for DEM. The FT4 simulations show mixed fibers/chips require higher force and torque to drive shear flow than pure chips or fibers. The mass fraction and flexibility of fibers reveal nonlinear inter-dependency on impacting the shear flow of mixed fibers/chips. Polydisperse fibers well match the needle-rich samples on the flow attributes, while polydisperse mixed fibers/chips agree reasonably with the bark/stem-rich samples. The DEM study indicates that the flowability of pine residue biomass is determined collectively by various material attributes of the anatomical fractions, which must be considered when developing preprocessing methods for conversion-ready biomass with adequate material handling performance.

Effect of addition of wheat bran hydrolysate on bread properties.

Although the addition of bran to bread makes it healthier and more functional, it brings with it some technological problems. One way to eliminate these problems is hydrothermal pretreatment of wheat bran. In this study, five different ratios (10%, 20%, 30%, 50%, and 100%) of hydrolysates from hydrothermal pretreatment of wheat bran (150°C, 30min) were substituted with dough-kneading water during dough kneading for bread making. The physical, chemical, functional, textural and important starch fractions of the bread produced were determined. The addition of hydrolysate in different amounts to the dough-kneading water resulted in similar physical properties (height, specific volume, and crust color) as the control bread. While the addition of hydrolysate decreased the hardness of the breads, it positively improved important starch fractions (increasing the amount of slowly digestible starch and decreasing the amount of rapidly digestible starch). It also increased antioxidant capacity (iron (III) reducing antioxidant power, ABTS, and DPPH (2,2-diphenyl-1-picrylhydrazyl) and reduced the starch hydrolysis index of the bread. It was shown that the hydrolysate obtained after the hydrothermal treatment of bran could be used in bread making to satisfy the demand for products preferred by consumers from both health and sensory points of view.

Numerical Investigation of Partially Premixed Flames Under Transcritical Conditions

Understanding the characteristics of partially premixed flames (PPFs) under transcritical conditions is of critical importance for the development of fuel-rich staged rocket engines. While substantial progress has been achieved for transcritical non-premixed flames (NPFs), comparatively little effort has been made to investigate transcritical PPFs. To this end, a series of transcritical counterflow gaseous hydrogen/liquid oxygen (GH2/LOX) PPFs is simulated to investigate the thermodynamic structure of PPF and to examine the effects of molecular diffusion modeling, strain rate, and the equivalence ratio at the fuel-rich side on PPFs in physical space and mixture fraction space, as well as reduced temperature/reduced pressure space. The comparisons between the NPF and PPF demonstrate that the PPF exhibits a bimodal structure in physical space: a premixed reaction zone at the fuel inlet side and a non-premixed reaction zone at the oxidizer side. In mixture fraction space, the C-shaped structure of PPF is observed owing to the differential diffusion of species. It is found that the choice of molecular diffusion model has a significant impact on PPF structure. The presence of a loop at subcritical pressures in a reduced temperature/reduced pressure space is caused by the differential diffusion of species and the formation of [Formula: see text] in the non-premixed reaction zone. Furthermore, the results indicate that the premixed reaction zones in the PPFs are very sensitive to the change in strain rate and/or equivalence ratio of the premixed mixture at the fuel inlet side. For a given equivalence ratio, increasing strain rate can suppress the differential diffusion effect and the C-shaped structure, while it has a negligible impact on the non-premixed reaction and hence on loop formation.

Elevated atmospheric CO2 drives decreases in stable soil organic carbon in arid ecosystems: Evidence from a physical fractionation and organic compound analysis.

The increasing concentration of CO2 in the atmosphere is perturbing the global carbon (C) cycle, altering stocks of organic C, including soil organic matter (SOM). The effect of this disturbance on soils in arid ecosystems may differ from other ecosystems due to water limitation. In this study, we conducted a density fractionation on soils previously harvested from the Nevada Desert FACE Facility (NDFF) to understand how elevated atmospheric CO2 (eCO2 ) affects SOM stability. Soils from beneath the perennial shrub, Larrea tridentata, and from unvegetated interspace were subjected to a sodium polytungstate density fractionation to separate light, particulate organic matter (POM, <1.85 g/cm3 ) from heavier, mineral associated organic matter (MAOM, >1.85 g/cm3 ). These fractions were analyzed for organic C, total N, δ13 C and δ15 N, to understand the mechanisms behind changes. The heavy fraction was further analyzed by pyrolysis GC/MS to assess changes in organic compound composition. Elevated CO2 decreased POM-C and MAOM-C in soils beneath L. tridentata while interspace soils exhibited only a small increase in MAOM-N. Analysis of δ13 C revealed incorporation of new C into both POM and MAOM pools indicating eCO2 stimulated rapid turnover of both POM and MAOM. The largest losses of POM-C and MAOM-C observed under eCO2 occurred in soils 20-40 cm in depth, highlighting that belowground C inputs may be a significant driver of SOM decomposition in this ecosystem. Pyrolysis GC/MS analysis revealed a decrease in organic compound diversity in the MAOM fraction of L. tridentata soils, becoming more similar to interspace soils under eCO2 . These results provide further evidence that MAOM stability may be compromised under disturbance and that SOC stocks in arid ecosystems are vulnerable under continued climate change.

Changes in soil organic carbon stocks and its physical fractions along an elevation in a subtropical mountain forest

Soil microorganisms are the drivers of soil organic carbon (SOC) mineralization, and the activities of these microorganisms are considered to play a key role in SOC dynamics. However, studies of the relationship between soil microbial carbon metabolism and SOC stocks are rare, especially in different physical fractions (e.g., particulate organic carbon (POC) fraction and mineral-associated organic carbon (MAOC) fraction). In this study, we investigated the changing patterns of SOC stocks, POC stocks, MAOC stocks and microbial carbon metabolism (e.g., microbial growth, carbon use efficiency and biomass turnover time) at 0–20 cm along an elevational gradient in a subtropical mountain forest ecosystem. Our results showed that SOC and POC stocks increased but MAOC stocks remained stable along the elevational gradient. Soil microbial growth increased while microbial turnover time decreased with elevation. Using structural equation modeling, we found that heightened microbial growth is associated with elevated POC stocks. Moreover, MAOC stocks positively correlate with microbial growth but show negative associations with both POC stocks and soil pH. Overall, the increase in SOC stocks along the elevational gradient is primarily driven by changes in POC stocks rather than MAOC stocks. These findings underscore the importance of considering diverse soil carbon fractions and microbial activities in predicting SOC responses to elevation, offering insights into potential climate change feedbacks.

Earthworms facilitate stabilization of both more-available maize biomass and more-recalcitrant maize biochar on mineral particles in an agricultural soil

Agricultural soils have lost enormous amounts of soil organic matter (SOM) as the result of conventional agriculture. Nowadays, returning plant biomass in the form of crop residues is used as an efficient strategy to increase the amount of SOM. In addition, earthworms help increase the SOM content by transforming OM into stable forms. There is, however, limited information on how earthworms transform and stabilize various forms of crop residues and what the potential feedbacks on soil quality are. In a five-month laboratory manipulation experiment, we added maize biomass and/or biochar to a temperate agricultural soil both in the presence and absence of earthworms and carried out physical fractionation to analyse the stabilization of OM either as aggregate-occluded particulate OM (oPOM) or mineral-associated OM (MAOM).We show that the combination of maize biomass, maize biochar and earthworms proved to be highly efficient in increasing the OM content in agricultural soils and that earthworms can simultaneously enhance both OM decomposition and stabilization. In the absence of earthworms, the OM was stabilized more in the oPOM fraction, suggesting that both maize substrates acted as aggregation agents. In the presence of earthworms, however, maize substrates were stabilized more in the MAOM fraction, either through direct sorption as plant-derived substrates or as microbial necromass, suggesting that earthworms facilitate stabilization of both more-available maize biomass and more-recalcitrant maize biochar on mineral particles. We provide evidence that plant-derived rather than microbial-derived MAOM is present in the earthworm-affected agricultural soil and is thus important in increasing the SOM content and stability.

Spatially Fractionated Radiation Therapy in Sarcomas: A Large Single-Institution Experience

ObjectiveSpatially fractionated radiation therapy (SFRT) is a recognized technique for enhancing tumor response in radioresistant and bulky tumors. We analyzed clinical and treatment outcomes in patients with bone and soft tissue sarcomas treated with modern SFRT techniques. MethodsPatients with metastatic and/or unresectable sarcoma treated with brass collimator, volumetric modulated arc therapy (VMAT) lattice, or proton SFRT from December 2019-June 2022 were retrospectively reviewed. Consolidative external beam radiation therapy (EBRT) was delivered at the physician's discretion. Patient and treatment characteristics, treatment response (symptom improvement, local control, and imaging response), and toxicity data were collected. ResultsThe cohort consisted of 53 patients treated with 61 SFRT treatments. Median age at treatment was 60.0 years. The primary location was soft tissue in 46 courses (75%) and bone in 15 (25%). Fifty-three courses (87%) were treated for symptom relief. The most utilized SFRT technique was VMAT lattice (n=52, 85%) to a dose of 20 Gy (n=48, 79%, range: 16-20 Gy). EBRT was delivered post-SFRT in 55 (90%) treatment courses with a median time interval from SFRT to EBRT of 5 days (range: 0-14 days). Median physical EBRT dose and fractionation was 40 Gy (range: 9-73.5 Gy) and 10 fractions (range: 3-33 fractions). Median follow up was 7.4 months (range: 0.2-30 months). One-year overall survival and local control rates were 53% and 82%. Symptom relief was documented with 32 treatment courses (60%). Stable or partial response was observed with 47 treatment courses (90%). Four grade 3-4 acute and subacute toxicities were attributable to SFRT (8%). ConclusionsThe current series is the largest to date documenting outcomes for SFRT in sarcomas. Our results suggest combined SFRT with EBRT is associated with a favorable toxicity profile and high rates of symptomatic and radiographic responses for metastatic and/or unresectable sarcomas.

What is environmental DNA?

AbstractDNA collected from the environment (eDNA) can provide valuable understanding of ecological patterns and processes. eDNA is highly physically heterogeneous, but this has not been well‐characterized, so most eDNA sampling strategies do not target any particular physical fraction. Consequently, we have limited evidence to understand and interpret the physical behavior of eDNA, to improve the efficiency of sampling, nor to target components of the eDNA spectrum for taxonomic and molecular attributes. We perform the first detailed characterization of the components of a marine eDNA sample using serial filtering from an 80 to &lt;0.22 μm particle size gradient, a tree of life metabarcoding approach using taxon‐specific and universal assays, coupled with scanning electron microscopy and fluorescent confocal microscopy. We confirm that eDNA is manifest in a broad spectrum of physical states, ranging from extracellular DNA fragments to whole cells, tissue fragments, and whole organisms. The largest of these fractions of eDNA were embedded in microbial biofilms, rather than particulate. We show that the choice of filter size and types can target components of this spectrum, can affect the detectable species richness, and notably, also enrich samples for specific taxonomic groups. Our results imply that there is considerable scope to improve the efficiency of eDNA collection from aquatic environments, and its informativeness.

Unexpected high alkyl carbon contents in organic matter-rich sandy agricultural soils of Northwest Central Europe

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

Novel nutrient dense quinoa fractions: physical, functional, thermal and rheological characterisation for potential industry application

SummaryQuinoa is known for its unique nutritional characteristics and contains good quality protein and fat along with appreciable amount of starch, dietary fibre and micronutrients. The fractionation facilitated the separation of the botanical components of the grain which were found to be rich in specific nutrients. The protein‐ and fat‐rich fraction (PFRF) projected 2.15 times protein and 2.74 times fat, while fibre‐rich fraction (FRF) showed 2.35 times fibre content as compared to quinoa whole grain. Starch‐rich fraction (SRF) with 82.41% starch was lower in protein content. FRF showed higher water holding capacity compared with other quinoa samples where bulk density was reported highest in PFRF fraction (670 kg per m3). These fractions showed variation in their gelatinisation enthalpy for the thermal properties. Foaming and emulsion properties were significantly impacted by the composition of the fractions and varied at different pH. The apparent viscosity was recorded highest for FRF, where SRF was lowest. At varied temperatures tested, the exhibited behaviour of all samples was found to be non‐Newtonian in nature. Present study concludes that quinoa physical fractionation produced novel nutrient dense fractions with unique techno‐functional features and has potential to be explored for food product development as independent functional ingredient.

Soil organic carbon stabilization based on physical fractionation method in tree based riparian and adjacent agricultural systems in southern Ontario, Canada

Soil organic carbon stabilization based on physical fractionation method in tree based riparian and adjacent agricultural systems in southern Ontario, Canada

Accumulated Carbon Fractions in Tropical Sandy Soils and Their Effects on Fertility and Grain Yield in an Integrated Crop–Livestock System

Food production in sandy soils has evolved significantly, most notably through the advent of integrated crop–livestock systems (ICLSs). ICLSs increase soil cover, which maintains soil moisture and sequesters carbon (C). Here we investigate the influence of ICLSs on soil physical, chemical, and biochemical properties, and grain yield (GY) in tropical sandy soils in short-time. We compared seven ICLSs in two consecutive crops seasons (with soybean or maize as cash crops) in southeastern Brazil. These were (1) corn + Urochloa brizantha cv. BRS Paiaguás—soybean (ICL-Paiaguás); (2) corn + U. brizantha cv. BRS Piatã—soybean; (3) corn + U. ruziziensis—soybean; (4) corn–soybean under conventional tillage (CT) as a negative control; (5) corn–soybean under no-tillage (NT) as a positive control; (6) Paiaguás grass—continuous grazing (Perennial Paiaguás); (7) and Piatã grass—continuous grazing (Perennial Piatã). Soybean and corn GY data, soil physical and chemical attributes, and soil enzymatic activity were subjected to descriptive statistics and multivariate analysis. CT and NT shared high loadings of H + Al, Al, and soil temperature and low loadings of soil pH, SOM physical and chemical fractions, cationic exchange capacity, and arylsulfatase activity. ICL-Paiaguás and Perennial Piatã had a similarly high loading of total N, humin, total organic carbon, and mineral-associated carbon stocks. The fulvic acid fraction was the most sensitive to C accumulation in the sandy soil under ICLSs. Soil water and thermal regimes were limiting in both CT and NT. The study not only confirms the capacity of conservation mechanisms to enhance soil-based ecosystem functions, but it also highlights the potential of ICLSs to aid sustainable food production even in the context of tropical sandy soils, which frequently receive limited attention in intensive agricultural practices.