Low Organic Carbon Content Research Articles

Air Bubbling Assisted Soil Washing to Treat PFAS in High Organic Content Soils

The soil-washing technique has been successfully utilized for the remediation of PFAS-contaminated soils. Prior studies have shown that the organic carbon (OC) content and grain size of soil determined the efficiency of PFAS removal during washing. However, most of the past studies have focused on soils with a low OC content, typically ranging from 0–3%. In this study, we explored the use of a novel process where soil washing was combined with air bubbling (or foam fractionation) to aid in the removal of PFAS from high OC-content soils (~4–20%). Treatment with air bubbling of high OC soil (~20%) with perfluorobutane sulfonate (PFBS) and perfluorooctanoate (PFOA) did not enhance their removal, as they featured low surface activity. However, we observed an improvement in the extraction of perfluorooctane sulfonate (PFOS) from 27% to 42% with bubbling, consistent with the higher surface activity of PFOS compared to PFOA and PFBS. Perfluorodecanoic acid (PFDA) was irreversibly adsorbed to the high OC soil and was not removed efficiently by both bubbling and soil washing. A slight improvement in PFDA removal (6–13%) was observed when a co-surfactant (cetyltrimethylammonium chloride) was added and when the OC content was reduced to ~4% by the addition of nonorganic sand to the contaminated soil prior to soil washing. This suggested that the interaction of PFDA with OC was the dominant factor determining its extraction from soil. In conclusion, our results indicated that soil washing alone was sufficient for the removal of short-chain PFAS from soil. Although bubbling had a mild effect on the removal of some long-chain PFAS from the solution, it did not help in the overall removal of PFAS from high OC soils, highlighting the difficulty in the treatment of high OC-content soils and that immobilization of PFAS would be an ideal approach in managing such contaminated sites.

Influence of degree of cultivation of sod-podzolic soil on dynamics of content of soil organic carbon

In 1999–2001 on the fields of the Falenky Breeding Station (Kirov region), the dynamics of the content of soil organic carbon (Corg) and its labile part (Clab) in sod-podzolic arable soil of varying degrees of cultivation were studied. The arable layer of weakly cultivated variant of the soil was characterized by high acidity (pHKCl – 3.88) and low organic carbon content (Corg – 0.91 %). The well cultivated variant had an acidity close to neutral in the arable horizon (pHKCl – 6.14) and a total carbon content at the average level for sod-podzolic loamy soils of the region (Corg – 1.10 %). Soil samples were taken during the growing season once a month in a sixfold repetition from the arable horizon and in a threefold repetition for horizons A2B and B. It was revealed that during all years of observation in the arable horizon of the soil of the cultivated variant, the Corg content was significantly higher (by 16–76 %). In the underlying horizons of soils of both variants, the carbon content was sharply reduced to 0.2–0.6 %. The content of labile part of organic carbon did not differ by variants and varied from 0.05 to 0.19 % depending on the horizon and observation period. However, in the arable horizon of weakly cultivated soil, the proportion of labile carbon in the composition of total organic carbon was significantly higher, which indicated less stability of the soil organic matter system. The content of both forms of soil organic matter varied significantly over the years and during the growing season. Maximum values of Corg content were noted at the beginning and at the end of the observation season. Minimum values were noted in July. Content of Clab was decreasing from the beginning to the end of the season.

Artisanal and small-scale limestone mining affects soil parameters in Sohra (Meghalaya), India.

In this study, we assessed the changes in the physical and chemical characteristics of the soil samples collected from the artisanal and small-scale limestone mining site in Sohra (Cherrapunjee), Meghalaya, by comparing them with the non-mining site. Eleven distinct soil parameters, namely pH, electrical conductivity (EC), texture (ST), moisture content (MC), bulk density (BD), total porosity (TP), water holding capacity (WHC), organic carbon (OC), total nitrogen (TN), available phosphorus (AP), and exchangeable potassium (EK), were evaluated seasonally (winter, pre-monsoon, and post-monsoon) for 2years. The results showed that limestone mining has significantly affected the soil quality. The effect is evident by the substantial increases in EC values, sand content, and alkaline soils coupled with noticeably low concentrations of OC and TN. In addition, prominent changes were perceived in the soil MC and EK content, as well as in WHC, BD, and TP percent. Results from ANOVA revealed significant differences (p < 0.05) in mean values at different sampling seasons and sites. The multivariate statistical analysis results showed that the computed correlation coefficient (r) matrix data ranged from - 1.00 to 0.974. A strong positive correlation was highest between OC and TN (0.974), followed by OC with EK (0.828). Principal component (PC) analysis revealed two major components, PC 1 and PC 2, having eigenvalues of 6.276 and 1.747, respectively. Cumulatively, these two components explained 80.23% of the total variance. The loading factor in PC 1 is high and is attributed to OC (.974), TN (.970), and EK (.903). However, in PC 2, the loading factor is positively pooled by MC (0.894) and TP (0.765). The present study concludes that artisanal and small-scale limestone mining altered the soil's physical and chemical properties, and these changes are likely to have a subsequent deteriorating impact on the area's biodiversity, landscape, and natural ecosystem. Therefore, to minimize the impact and ensure sustainable soil management in the area, approaches for effective mitigation and remediation measures, including formulating steps for the conservation and enhancement of the soil's environmental quality, are recommended.

Factors governing crusting formation in soils in Southern Mali, West Africa: Evaluation of susceptibility indices

In Southern Mali and neighboring semi-arid Sahel regions, soil crusting and sealing are common and significant phenomena for people who depend on agriculture for their livelihoods. These processes form hard, impermeable layers on the soil surface, reducing water infiltration, increasing runoff and erosion, and hindering germination, seedling emergence, and productivity. Factors such as rainfall intensity, topography, soil attributes, and poor management practices contribute to these phenomena. Here, we aimed to analyze soil attributes affecting crust formation and evaluate them using indicators like the structural stability index (StI), particle separability index (PSI), and crusting susceptibility index (CSI). Soils samples from agricultural and native areas in Southern Mali were analyzed for physical, chemical, mineralogical, and micromorphological attributes. Results revealed that the soils in these regions have high silt and fine sand content and low organic carbon content. Poor soil management, leading to prolonged periods of bare soils, significantly contributes to crusting. Kaolinitic clays, Ca2+ and Mg2+ contents did not appear to affect crusting. The PSI revealed a high risk of aggregate disruption in both agricultural and native lands, demonstrating soil vulnerability to degradation. The StI showed limited risk of structural degradation in native lands, while agricultural soils were more susceptible to crusting. The CSI indicated moderate crusting susceptibility across the regions. By examining the three indices related to texture attributes and organic carbon, this study provides insights into estimating susceptibility to crusting through the evaluation of the risk of soil structural degradation, particle separation, and overall soil susceptibility to surface crusting, all of which underscore the need for improved soil attributes. It emphasizes the importance of implementing effective soil management strategies, particularly the adoption of cover crops, to enhance organic carbon content and increase vegetation cover. These measures are essential for improving soil health and minimizing the risk of crusting.

Field versus laboratory measurements of PFAS sorption by soils and sediments

Sorption by soils and sediments is an important process that influences the distribution, transport, and fate of per and polyfluoroalkyl substances (PFAS) in the environment. Many laboratory studies have been conducted to quantify magnitudes of PFAS sorption as a function of the properties of the PFAS, solutions, and porous media. A critical question is how representative are laboratory-measured sorption magnitudes for field applications. To address this question, log Koc data were compiled from the literature for a range of PFAS of different chain lengths and functional groups. The aggregated field-based data consisted of two types, in-situ measurements comprising paired soil/sediment and water samples and ex-situ measurements obtained from laboratory desorption experiments employing field-contaminated media. These two sets of field-based measurements were compared to a comprehensive data set of standard laboratory batch-type measurements. The compiled data sets represent an extremely wide range of soil and sediment properties. One important novel outcome is the observation that the enhanced sorption of short-chain PFAS observed in several prior laboratory studies is also observed for the field data. This differential enhanced sorption should be accounted for in site investigations and modeling studies. Another relevant outcome is the observation of consistency between measurements obtained with standard batch adsorption experiments and those from desorption studies employing either field-contaminated or artificially-contaminated media. The mean log Koc values determined for the in-situ measured field data were generally larger than the mean laboratory-determined values, particularly for the short-chain PFAS. Notably, however, values for subsets of the laboratory data representing measurements for lower aqueous concentrations or for soils with low organic-carbon contents (<1 %) compared well to the in-situ field data. Measurements compiled for anionic-polyfluoroalkyl, neutral, and cationic PFAS compared well to those for PFCAs and PFSAs. Overall, the results indicate that the laboratory measurements of PFAS sorption were generally representative of the field-derived magnitudes when compared on a consistent basis.

Impact of gas adsorption of nitrogen, argon, methane, and CO2 on gas permeability in nanoporous rocks

Gas adsorption on the surface of nanoporous rocks is an important process that occurs in many applied scenarios such as shale gas production or CO2 enhanced gas recovery or storage. While there are few theoretical considerations on the effect of gas adsorption on permeability, a systematic laboratory investigation of the impact of gas adsorption on gas flow and permeability is still lacking. In this paper, permeability of four adsorptive gases, i.e., nitrogen, argon, methane, and carbon dioxide, was measured, along with helium permeability, for two nanoporous rock samples that have high and low total organic carbon (TOC) content, respectively. The measurements were conducted at a range of pore pressures from 150 to 1500 psi (1.03–10.34 MPa). Gas adsorption isotherms were also measured at the same conditions. A mathematical model that considers adsorption with specific boundary conditions for the experimental setup was used for data analysis. The results show that gas adsorption causes larger drop in pressure decay and greater retardation in pressure equilibrium. However, the reduction of permeability relative to helium (25%–46%) is similar for gases with different levels of adsorption, indicating the occurrence of single-layer adsorption for these gases. Comparison between the two samples further supports the concept of single-layer adsorption and signifies the impact of pore size on the permeability reduction due to adsorption. These new findings deepen the fundamental understanding and provide important clarification on the effect of gas adsorption on gas flow and permeability in nanoporous rocks.

A multi-proxy approach to explore paleoenvironmental oscillations and chronostratigraphy of Thanetian carbonates in Eastern Tethys, Pakistan

This study is the first to incorporate geochemical analyses alongside traditional micropaleontological and sedimentological methods to redefine the chronostratigraphy, paleoenvironmental history and regional correlation of the Late Paleocene Lockhart Limestone from four distinct sections covering the entire Upper Indus Basin. Based on the age diagnostic foraminiferal species, we report SBZ3 to SBZ4 (Thanetian age) for the Lockhart Limestone in contrast to previous studies restricting it to SBZ3. The interpretation of eight distinct microfacies reveals a progressively shallowing upward sequence, indicating a dynamic depositional environment with varying energy levels and water depths ranging from inner, middle, to outer ramp settings. Mineralogically, the formation is predominantly composed of calcite, with quartz being the next significant component. Geochemical analyses, specifically the major oxide results, highlight that CaO is the primary constituent, while notable amounts of SiO2, Fe2O3, Al2O3, and MgO are present. The low proportions of SiO2 and Al2O3, combined with their negative correlation with CaO, and high Mg/Ca ratio suggest limited siliciclastic input during the precipitation of limestone that supports the shallow marine depositional environment inferred from the facies analysis. Trace elemental ratios, indicating predominantly oxic conditions, also align with the well-oxygenated waters of a shallow marine setting. Paleosalinity and paleotemperature indicators suggest normal marine and moderate paleotemperature conditions for limestone facies, with lagoonal conditions for shale facies, which is consistent with the interpreted shallow marine environment. The low Total Organic Carbon (TOC) content indicates the presence of type-III and IV organic matter, derived from recycling or continental sources, suggesting limited organic matter preservation in the depositional setting. The clay mineralogy suggests mainly humid conditions with occasional warm climates and alternating humid and arid periods. The deposition of the marine facies of Lockhart Limestone marks the transgression of the Eastern Tethys following a regressive episode that deposited the continental facies of the Hangu Formation, influenced by evolving paleoclimate and geomorphology under Paleo-Tethys tectonism.

Shift of bacterial and fungal communities upon soil amelioration is driven by carbon degradability of organic amendments

The structural response of bacterial and fungal soil communities to four carbon-rich organic amendments of increasing recalcitrance was investigated. Wheat straw, green compost, a mixed product based on biogas residues, and a fermented biochar were applied to a sandy agricultural soil of low organic carbon content. After laboratory incubation for 6 months, the community structure was investigated via DNA sequencing. All amendments caused changes in the communities of bacteria and fungi, but to different extents, with the communities exposed to more recalcitrant amendments showing the least variation compared to the non-amended soil. Changes in species composition as well as their relative abundances were observed. While the straw had a pronounced effect on bacteria (e.g., the highest number of indicator species), effects of the composted, fermented, or pyrolyzed materials were minor. Hierarchical clustering showed that the fungal communities were more different from each other than the bacterial ones with the straw-soil being most different and the biochar-soil least different from the non-amended soil. While the abundant fungal species in biochar-soil and non-amended soil were very alike, especially rare fungal species shifted upon addition of biochar. An indicator species analysis identified specific taxonomic groups which were triggered by the different organic materials. We conclude that bacterial and fungal communities strongly change upon input of degradable carbon (straw), while fungi in particular respond to the application of processed organic materials. With this study, we report the consequences of applying organic materials for the microbial community in one soil. We provide these data for meta-analyses that are required to unravel all relevant interactions across different soils, organic materials, and time. This will allow to better understand and predict the effects of organic soil amelioration measures on soil microorganisms.

Effects of temperature, relative humidity and soil organic carbon content on soil-air partitioning coefficients of volatile PFAS

Soil-air partitioning coefficient (KSA) values are often used to assess the environmental fate of organic contaminants in soil. Till now, sufficient KSA values have not yet been measured for many compounds of interest, including some emerging pollutants such as volatile PFAS. Moreover, the effects of environmental factors such as temperature, relative humidity and soil organic carbon content on KSA of volatile PFAS are also unclear. In this study, the KSA values of target volatile PFAS were measured under various temperature (20–40 °C), relative humidity (30–100 %) and soil organic carbon content (2.1 %–8.0 %) using a modified solid-phase fugacity meter. The results showed that higher temperatures, higher relative humidity and lower organic carbon content in soil may accelerate the diffusion of target volatile PFAS. Furthermore, the KSA measurements were used to derive a multiple linear regression model to depict the relationship between logKSA and temperature, relative humidity, soil organic carbon content and PFAS-specific logKOA. When compared with the predictions obtained from semi-empirical model, we argued that the multiple linear regression model is more robust and easier to implement for target volatile PFAS or other emerging volatile PFAS than the semi-empirical approach to help depict the diffusion process at target volatile PFAS contaminated sites.

Devastation of the cerrado of mato grosso do sul and the advance of arenization in the pardo river watershed

Despite the significant biodiversity in the Cerrado, the process of occupation, subsequent economic cycles, and intensification of agriculture in a predatory manner have caused profound alterations in this biome. This study analyzed changes in land use and land cover in the Cerrado of Mato Grosso do Sul between 1985 and 2022 by mapping and also investigating the formation and dynamics of sand dunes in the Bauru sedimentary basin, focusing on the Pardo River watershed. MapBiomas Network data, collection 8, were used for land use and land cover analysis. Arenization foci cartography was conducted using brightness index 2 based on Sentinel-2 satellite images in Sentinel Application Platform software. The historical analysis of land use and cover in the Cerrado of Mato Grosso do Sul revealed a rapid transformation of the landscape, with a drastic reduction of native vegetation and an intensification of large-scale monocultures. Between 1985 and 2022, the Cerrado of Mato Grosso Sul lost 4.6 million hectares of native vegetation (forest formations, savannahs, grasslands, and wetlands), representing 24.54% of this territory. Recent changes in land use include pasture-soybean and pasture-eucalyptus. In the Pardo River watershed, arenization foci cover an area of 17,834.34 hectares, with varying dimensions ranging from less than 1 hectare to 376.41 hectares. The arenization process occurs in different slope compartments, such as the base, slope, and interfluves. The physical and chemical characteristics of Quartzipsamments, such as low organic carbon content in soil, are associated with high rates of surface exposure and weakened load-dependent structures, leading to degradation. Arenization occurs where natural vegetation has been suppressed and soil has been depleted by poorly managed production processes.

Carbonaceous aerosol emissions from secondary lighting sources: Emission factors and optical properties

India is shifting towards cleaner residential fuels, but this transition does not fully address household lighting challenges. Power disruptions, especially in rural areas, lead to the use of secondary lighting sources such as kerosene lamps, edible oil lamps, and candles. Our previous work identified kerosene wick and hurricane lamps as major secondary lighting sources in Indian households. This study presents the emission factors (EF) and optical properties of carbonaceous aerosols from five major secondary lighting devices in India, measured using a laboratory extractor hood system. Dominant secondary lighting devices, such as simple wick lamps (61.4 ± 9.8 g kg⁻1) and hurricane lamps (17.2 ± 4.8 g kg⁻1), exhibit higher elemental carbon (EC) EFs than typical residential biomass burning. Sesame oil lamps, primarily used in India during the Diwali festival, also have significant EC emission potential, with an EC EF of 71.6 ± 16.9 g kg⁻1. The low absorption Angstrom exponent (AAE) of ∼1 at near-UV wavelengths indicates a dominance of black carbon (BC) and negligible brown carbon absorption, corroborated by very low organic carbon concentrations. India-wide EC emissions (12.5 Gg year⁻1) from residential kerosene lighting show a higher (∼50%) contribution from eastern India. Additionally, the use of oil lamps during the Diwali festival could emit ∼3 Gg of EC in two days, with a potential reduction of ∼90% if wax-based lamps replace oil lamps. These measured EFs, aerosol optical properties, and estimated emissions will help future studies derive more accurate climate and health impacts from these otherwise overlooked lighting devices.

Landscape and soil cover diversity in Polissia and Forest-Steppe of Ukraine

Recent research has revealed the patterns of spatial and temporal variability of crop yields for the Polissia and the Forest-Steppe regions of Ukraine. In addition, the approaches to differentiating agroeconomic and agroecological components in the variability of the productive potential of the territories were developed. Approaches have been developed to quantify the spatial and temporal variability of soil erosion for individual areas of the region. The issue of assessing the impact of erosion processes on crop yields at the regional level remains unresolved. The diversity of landscapes and soil cover in Polissia and the Forest-Steppe of Ukraine was assessed in this article. The research covered 10 administrative regions of the north and northwest of Ukraine, which are located mainly within mixed forests (Polissia) and the eastern European forest steppe (Forest-Steppe). Part of the territory is tangential to the Carpathian mountain forests and the Pontic steppe. Within the study area, 30 WRB soils were identified. The largest area is occupied by Phaeozems Albic (21.7% of the total area of the region). These soils are located mainly in the southern and central parts of the region. In the north of the region, Phaeozems Albic form an almost continuous cover, and to the north, the areas of these soils become island-like. Phaeozems Luvic cover 12.1% of the region's territory. The Phaeozems group also includes Phaeozems Gleyic (0.93%), Phaeozems Haplic (0.13%), and Phaeozems Sodic (1.78%). Albeluvisols Umbric (17.1%) occupy a significant part of the region's territory. These soils occupy the north of the region and extend south along the Dnipro River floodplain. Spatially close to these soils are Albeluvisols Gleyic (12.8%). In the western part of the region, in Prykarpattia, there are Albeluvisols Stagnic (0.82%). The organic carbon content in the soils of the administrative districts of the region in the 0-5 cm layer was 5.2±3.3% and ranged 0.5% to 23.9%. In the layers of 5–15 and 15–30 cm, this figure decreased to 1.9 ± 1.1% and 1.9 ± 1.0%, respectively. In the 30–60 cm layer, the organic carbon content was 1.4 ± 0.8% and ranged 0.1% to 6.1%. The lowest organic carbon content was observed in the north central part of the region, and the highest content was observed in the north-east and north-west of the region. In the south of the region, there was found a strip of soils with moderate organic carbon content. The lowest content of organic carbon is characteristic of Albeluvisols and Podzols, which are located in the north of the region. In turn, the highest content of organic carbon is characteristic of organogenic Histosols, which, together with Albeluvisols and Podzols, form the basis of the soil cover structure of the territories in the northeast and northwest of the region. It should be noted that the agronomic role of these soils is insignificant, and their organic carbon content cannot be considered as a traditional indicator of fertility. Nevertheless, organic carbon is a reliable indicator of the anti-erosion properties of both natural and agricultural soils. The organic carbon content of Chernozems is quite high, which is a factor in the high fertility of these soils and their importance in agricultural production. The organic carbon content of Fluvisols and Gleysols is naturally high. The importance of these hydromorphic soils is due to their high productive potential, which ensures their use in agriculture. It is also worth noting their high seed protection potential. Phaeozems cover a large area of the region and contain a high level of organic carbon. These soils form the basis of agricultural production and forestry in the region. The silt content in the region's soils measured 45.6 ± 8.5%, ranging 19.1% to 57.6%. The north of the region is represented by soils with the lowest silt content (19–41%). In the center, in the west of the region, there is a zone with the highest silt content (53–58%). In other parts of the region, there are transitional levels of silt content in the soil. The clay content in the soils was 30.7 ± 13.8% and ranged 7.4% to 36.0%. The zone with the lowest clay content in soils has been formed in the north. The highest clay content in soils is typical for the southern part in the center of the region. The sand content in soils is highest in the northern part of the region, and the lowest in the southwestern and southern parts of the region.

Effects of farmyard manure and chemical fertilizer application rates on soil biology, cotton and fiber yield

Organic and inorganic fertilizers have significant effect on plant physiology, yield per unit area, available plant nutrient contents and extracellular enzyme activities of soils. This study was carried out in field conditions in arid and semi-arid regions between 2020-2021 years, May 01. The effects of farmyard manure (FM) (20, 40, 60 Mg ha-1) and chemical (CF) (350 kg urea ha-1, 100, 200, 300 kg DAP ha-1) fertilizers applied at different rates on plant nutrient (N, P, K, Ca, Mg, Fe, Cu, Zn and Mn) contents, SPAD value and NDVI of cotton plants, seed cotton yield and soil enzymes (urease, catalase, dehydrogenase, alkaline phosphatase) were investigated. The results showed that FM applications significantly (p&lt;0.01) increased the plant macro and micronutrients compared to CF applications, except for N (200 + 150 kg urea ha-1), Zn and Cu (300 kg DAP + 200 + 150 kg urea ha-1) in the 2021 cotton growing season. Mineralization of FM is slow under natural conditions; therefore, the use of FM alone is not sufficient to meet the nutrient needs of high yielding varieties. Urease and dehydrogenase activities increased significantly in FM treated soils compared to CF, while no significant (p&lt;0.01) increase was recorded in alkaline phosphatase and catalase activities. Farmyard manure is a useful management practice for increasing soil biological activity. Physiological parameters of NDVI, SPAD and seed cotton yield significantly increased in FM treated soils compared to CF applications. The increase in cotton yield was 29.15%, in NDVI value was 22.38% and in SPAD value was 121.7%. The main issues with cotton in the area are the low organic carbon content of the soils, high clay content, arid and semi-arid soils, and their detrimental impact on the uptake of particular nutrients (N, P and B).

Vineyard cover crop management strategies and their effect on soil properties across Europe

AbstractVineyard soils are often of inherently poor quality with low organic carbon content. Management can improve soil properties and thus soil fertility. In European wine‐growing regions, a broad range of inter‐row management strategies evolved based on specific local site conditions and the varying effects of management intensities on soil, water balance, yield and grape quality. Accordingly, there is a need to investigate the effects of locally common cover crop management strategies and tillage intensity on soil organic carbon content and soil physical parameters. In this study, we investigated the impact of the most common inter‐row management practices in Austria, France, Romania and Spain. In all countries, we compared paired sites. Each site with cover crops and inter‐row management of low intensity was compared with one site with (temporarily) bare soil and high management intensity. All studied sites with cover crops and low management intensity, except those in Spain, had higher organic carbon contents than the paired more intensively managed vineyards. However, the highly water‐limited Spanish vineyards with temporary cover crops had lower organic carbon contents than the paired sites with bare soil. Sites with more organic carbon had better results for bulk density, percolation stability (PS), hydraulic conductivity and available soil water, with soil hydraulic parameters being less pronounced than others. Country comparison of inter‐row weed control systems showed that PS was particularly low in sampled vineyards in Romania and Spain, where weed control is based on intensive mechanical tillage. Alternating management systems with tillage every second inter‐row showed a decrease in soil structure compared with permanent green cover. Thus, inter‐row management with cover crops and reduced tillage increases soil organic carbon content and improves soil structure compared with bare soil management. If local constraints, such as water scarcity, do not allow year‐round planting, alternating inter‐row management with several years of alternating periods may be an option to mitigate those adverse effects. However, negative impact on the soil structure occurs with the very first tillage operation, whereas negative effects on the carbon balance only appear after long‐term use of tillage.

Partitioning denitrification pathways in N2O emissions from re-flooded dry paddy soils

In flooded paddy fields, peak greenhouse gas nitrous oxide (N2O) emission after rewetting the dry soils is widely recognised. However, the relative contribution of biotic and abiotic factors to this emission remains uncertain. In this study, we used the isotope technique (δ18O and δ15NSP) and molecular-based microbial analysis in an anoxic incubation experiment to evaluate the contributions of bacterial, fungal, and chemical denitrification to N2O emissions. We collected eight representative paddy soils across southern China for an incubation experiment. Results show that during the 10-day incubation period, the net N2O emissions were mainly produced by fungal denitrification, which accounted for 58–77% in six of the eight investigated flooded paddy soils. In contrast, bacterial denitrification contributed 6–15% of the net N2O emissions. Moreover, around 11–35% of the total N2O emissions were derived from chemical denitrification in all soil types. Variation partitioning analysis (VPA) and principal component analysis (PCA) demonstrated that initial soil organic carbon (OC) concentrations were the primary regulator of N2O source patterns. Soils with relatively lower OC concentration (7–15 mg g−1) tend to be dominated by fungal denitrification, which accounted for the net N2O production at the end of the incubation period. Overall, these findings highlight the dominance of the fungal denitrification pathway for N2O production in flooded paddy soils, which predominates in soils with relatively lower OC content. This suggests that fungal contribution should be considered when optimizing agricultural management system timing to control N2O emissions in flooded paddy soil ecosystems, and for the relevant establishment of predictive numerical models in the future.

Efficacy of nitrogen and Azolla spp. on growth and yield of black rice (Oryza sativa L.)

An experimental field study was carried out in the Kharif season of 2023 at the Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj (U.P.). The experimental replications were conducted using a Randomized Block Design, with three levels of Nitrogen (0, 60, 90kg N/ha) and Azolla spp. (2, 4, 6t/ha), and one Control (NPK 120:60:60 kg/ha). In all, there were a total of ten treatments, each reproduced three times. The tested field had sandy loam soil texture with a neutral soil pH of 7.6, low organic carbon content of 0.372%, nitrogen content of 278.4 kg/ha, phosphorous content of 29.5 kg/ha, and potassium level of 217.3 kg/ha. The experimental results showed that treatment T₉ obtained significantly higher plant height (107.77 cm), dry weight (66.05 g), crop growth rate (57.27 g/m2/day), relative growth rate (0.0279 g/g/day), highest number of tillers per hill (22.07), panicles per m2 (282), test weight (15.23 g), grain yield (3.67 t/ha), stover yield (6.7 t/ha), and harvest index (35.74%). Transplanted Black Rice of variety BPT-2841 exhibited significantly greater maximum gross return (1,80,551.40 INR/ha), net return (1,05,496.30 INR/ha), and B:C ratio (1.41) in treatment T9. The investigation concludes that Nitrogen, being easily transportable in soil and plants, is a constituent of amino acids, nucleic acids, chlorophyll, enzymes, and hormones. These factors are essential in plant physiology and are associated with increased tillering, biomass production, protein synthesis, grain filling, yield, and quality. The availability, absorption, and utilization of nitrogen have a significant impact on these processes. Therefore, in the present experiment, the nitrogen requirements are met by applying 90kg of nitrogen through urea combined with 6t/ha of Azolla spp. This approach revealed superior performance in terms of both crop yield and economic returns .

TEKNOLOGI REKLAMASI LAHAN BEKAS TAMBANG TIMAH MELALUI PEMBERIAN BAHAN AMELIORAN DAN PEMILIHAN JENIS TANAMAN: STUDI KASUS KEPULAUAN BANGKA BELITUNG

Indonesia, besides being the country with the largest nickel reserves in the world, also holds the largest tin reserves globally in 2023. Meanwhile, in terms of production, Indonesia ranks second after China. Tin mining in Indonesia has led to serious environmental damage, illustrated by the numerous open pits and inadequately restored tin mining sites. The characteristics of soil in these post-mining lands generally include sandy texture, low pH, nutrient deficiencies, low organic carbon content, and low water holding capacity. This study aims to improve the soil chemical properties in post-mining lands by utilizing the KOMFABA technology, which consists of a mixture of compost and fly ash-bottom ash with appropriate dosages tailored to the type of crops to be planted, along with revegetation strategies involving suitable plant selections. The research methodology consists of field experiments to test the application of KOMFABA with various dosages and crop types, as well as a literature review to identify suitable revegetation strategies. The research result show that Indonesia holds tin reserves of 800,000 tons, making it the largest in the world, with a production of 74,000 tons, placing it second after China. Additionally, the results of KOMFABA testing demonstrate its effectiveness in improving soil chemical properties such as soil pH, organic carbon content, cation exchange capacity (CEC), nutrient content, and soil base saturation. The success of reclaiming post-mining lands also dependent on proper fertilization dosages and suitable plants selection.

Alfalfa-livestock system promotes the accumulation of soil organic carbon in a semi-arid marginal land

Developing cropland in marginal lands presents a potential solution to address food security challenges. However, the low organic carbon (C) content in these soils severely constrains crop productivity, and developing cropland aggravates the loss of soil organic carbon (SOC). Therefore, it is essential to elevate the SOC content via a profitable solution for food production. In this study, we examine the impacts of land use changes (fallow, cropland, and Alfalfa-livestock system [AL]) over 12 years on SOC content, composition, and mineralization rate in a semiarid marginal land. SOC was categorized into three components: plant necromass C, microbial necromass C, and "other C." We utilized lignin and amino sugars as biomarkers to assess plant and microbial necromass C content, respectively, and the remaining component was other C. We found that AL increased SOC contents in 0–15 cm by 142 % and 123 % compared to fallow and cropland. Other C was the main factor driving SOC accumulation in AL compared to fallow and cropland, which contributed 2 times more than microbial necromass C (63 % VS 31 %), while plant necromass contributed less than 7 %. Furthermore, AL decreased C mineralization per unit of SOC than fallow and cropland due to increased soil available N contents. In conclusion, AL facilitated a rapid increase in SOC contents on marginal lands by fostering the accumulation of microbial necromass C and other C while inhibiting SOC mineralization. This finding helps improve the productivity and sustainability of marginal croplands.

Response of tomato to innovative organo-mineral fertilizers

Organo-mineral fertilizers (OMFs) with low organic carbon (Corg) content have been associated with higher mineral fraction nutrient use efficiency. However, the extraction of peat, which is typically used in these OMFs, from endangered ecosystems causes long-time stored Corg to mineralize and to be released back into the atmosphere as carbon dioxide (CO2). This study analyzes the replacement of peat in OMFs with biowaste materials. These materials, considered organic byproducts that microorganisms and other living things can decompose through composting and aerobic or anaerobic digestion, offer a viable opportunity. This study investigated three stabilized biowastes—green compost (GC) from pruning residues, municipal solid waste compost (MSWC), and manure-based vermicompost (VC)—as the organic matrices for granular OMFs. These matrices were impregnated with dissolved ammonium sulfate and urea and used to coat diammonium phosphate granules. Each biowaste OMF contained 7.5% Corg, 20% mineral N, and 10% mineral P2O5 (OMF20 − 10). Fertilizers with high nutrient concentrations have the advantage of requiring low application volumes, facilitating their application in the field. Biowaste OMFs were compared with peat OMFs with the same Corg-N-P2O5 concentration. Peat and MSWC were also used to create OMFs containing 7.5% Corg, 10% mineral N, and 5% mineral P2O5 (OMF10 − 5). A 75-day tunnel trial was conducted under semi-controlled conditions using tomato plants (Solanum lycopersicum L.) fertilized to an equivalent of 81 mg N kg−1 soil and 18 mg P kg−1 soil. Controls included no fertilization (N0P0) and mineral N and P fertilization (MFNP). The Soil Plant Analysis Development (SPAD) chlorophyll meter and the BBCH (from German Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie) scale as well as the number of shoots were measured over time, as berry and total aboveground yield, N and P uptakes, and N and P use efficiencies (NUE and PUE, respectively) were calculated at harvest. All treatments outperformed the control N0P0 in most indicators. Peat20 − 10 did not have more berry yield than other OMF20 − 10; however, the higher number of shoots indicated a higher potential yield in the event of prolonging the experiment. At the end of 75 days, VC20 − 10 and MSWC20 − 10 showed similar PUE to peat, suggesting that those materials can be used as replacements. In the case of OMF10 − 5, MSWC10 − 5 had yield and N and P uptakes like peat OMFs, confirming the potential use of MSWC as peat replacement even at different nutrient concentrations. This research provides reassuring evidence of the effectiveness of biowaste OMFs, offering a positive outlook for sustainable agriculture. However, their use is not recommendable for short growing seasons.

Estimating the uncertainties of satellite derived soil moisture at global scale

This study attempts to derive the uncertainty of the soil moisture estimation from passive microwave satellite mission at global scale. To do so, the approach is based on the sensitivity of the Soil Moisture and Ocean Salinity (SMOS) soil moisture retrieval quality to the land surface characteristics within its footprint (presence of forest, topography, open water bodies, sand, clay, bulk density and soil organic carbon content). First, we performed a global assessment of SMOS using in situ measurements from the International Soil Moisture Network (ISMN) as reference, with more than 1900 ISMN stations and 10 years of SMOS data. This assessment shows that the ubRMSD scores vary greatly between locations (with a mean of 0.074 m3m−3 and an interquartile range of 0.030 m3m−3). Second, the scores are analyzed for different surface conditions within the satellite footprint. The best agreement between the ground measurement and SMOS time series are obtained for low forest cover, low topographic complexity, and marginal presence of open water bodies within the SMOS footprint. Soil parameters also have an impact, with better scores for sandier soils with a high bulk-density and low soil organic carbon content. Finally, we propose to extrapolate the obtained relationships, using a multiple linear regression, in order to derive a global map of SMOS uncertainties based on surface conditions. This map of predicted uncertainties show a diverse range of ubRMSD values across the globe (with a mean of 0.076 m3m−3 and an interquartile range of 0.031 m3m−3) depending on the surface characteristics. At the ISMN site location, the predicted ubRMSD shows similar results than the comparison between SMOS and the in situ measurements. The map of predicted SMOS ubRMSD represents an upper bound estimate of the SMOS uncertainty, as it includes the uncertainties of the in situ sensor measurements and the scale mismatch. Further investigations will focus on the different components of this uncertainty budget to obtain a better assessment of the absolute uncertainties of SMOS soil moisture retrievals across the globe.