Amount Of Soil Organic Carbon Research Articles

Organic substitutions enhanced soil carbon stabilization and reduced carbon footprint in a vegetable farm

The strategies of substituting inorganic fertilizers with organic fertilizers have been shown to significantly impact the dynamics of soil organic carbon (SOC) combating soil degradation and climate changes in intensive vegetable production. However, the underlying mechanisms and comprehensive assessment of environmental consequences are not fully understood. We conducted a five-year field experiment in the Yangtze River Delta Alluvial Plain, China, four fertilization treatments were established at equal nitrogen (N) levels: sole mineral fertilizers (SN); organic substituting 20 % (M1N4), 50 % (M1N1), and 100 % (SM) of mineral N fertilizer with organic fertilizer. Soil carbon (C) pools, physical and chemical composition of SOC, and C footprint were measured based on soil aggregates, 13C nuclear magnetic resonance spectroscopy, and life cycle assessment to investigate the effects of organic substitution on SOC quantity, quality, and environmental implications. Our results showed a significant increase in SOC content, particularly in the M1N1 treatment. This increase was attributed to changes in soil properties, an elevation in dissolved organic C content, and improved SOC stability. Specifically, organic substitution increased the proportion of macroaggregates, content of lignin phenols, and enrichment of alkyl C groups. Based on life cycle assessment incorporating field measurements, the average C footprint ranged from 1.82 to 2.58 CO2 kg eq kg−1 vegetable in the five-year experiment, primarily influenced by transportation and fertilizer manufacturing. Partial organic substitution reduced the C footprint by 6.2–10.1 %, while the SM treatment increased it by 0.54 CO2 eq kg−1 vegetable, and the M1N1 had the lowest C footprint at 1.82 CO2 eq kg−1 vegetable. As a whole, this approach of substituting 50 % of mineral N with organic fertilizers serves as a viable strategy to bolster soil C stabilization, promote C accumulation, and mitigate the C footprint linked to intensive vegetable production in subtropical regions.

Global dataset of soil organic carbon in tidal marshes

Tidal marshes store large amounts of organic carbon in their soils. Field data quantifying soil organic carbon (SOC) stocks provide an important resource for researchers, natural resource managers, and policy-makers working towards the protection, restoration, and valuation of these ecosystems. We collated a global dataset of tidal marsh soil organic carbon (MarSOC) from 99 studies that includes location, soil depth, site name, dry bulk density, SOC, and/or soil organic matter (SOM). The MarSOC dataset includes 17,454 data points from 2,329 unique locations, and 29 countries. We generated a general transfer function for the conversion of SOM to SOC. Using this data we estimated a median (± median absolute deviation) value of 79.2 ± 38.1 Mg SOC ha−1 in the top 30 cm and 231 ± 134 Mg SOC ha−1 in the top 1 m of tidal marsh soils globally. This data can serve as a basis for future work, and may contribute to incorporation of tidal marsh ecosystems into climate change mitigation and adaptation strategies and policies.

Sequestering carbon in the subsoil benefits crop transpiration at the onset of drought

Abstract. Increasing soil organic carbon is promoted as a negative emission technology for the agricultural sector with a potential co-benefit for climate adaptation due to increased soil water retention. Field-scale hydrological models are powerful tools for evaluating how the agricultural systems would respond to the changing climate in upcoming years and decades, for predicting impacts, and for looking for measures that would help decrease drought-driven crop stress under current and future climatic conditions. We quantified how different levels of soil organic carbon (SOC) additions at varied soil depths are expected to influence drought-induced transpiration reduction (Treddry) in maize cultivated in Switzerland. Parameterization of the model based on a pedotransfer function (PTF) was validated against soil moisture data from a long-term lysimeter experiment with a typical Swiss soil, and the model was subsequently applied under climate forcing between 1981 until 2099, representative of three distinct climatic sites of Switzerland. We used the same PTF to indirectly assess the effects of SOC additions at different depths on soil hydraulic properties. We found a threshold in both the added amount of SOC (2 % added) and the depth of sequestering that SOC (top 65 cm), beyond which any additional benefit appears to be substantially reduced. However, adding at least 2 % SOC down to at least 65 cm depth can reduce Treddry in maize, i.e. increase transpiration annually but mostly at the onset of summer drought, by almost 40 mm. We argue that SOC increases in subsoils can play a supporting role in mitigating drought impacts in rain-fed cropping in Switzerland.

Digitally mapping soil carbon of the uThukela headwater catchment in the Maloti-Drakensberg, a remote Afromontane mountain region

ABSTRACT Although regional soil mapping is commended, site-specific studies are required for mapping and quantifying soil organic carbon (SOC) stocks at a landscape scale for management and rehabilitation purposes. Site-specific studies are especially important in remote mountainous areas where soil data are largely absent. The aim of this study was to quantify and map the SOCs of an alpine region in the Maloti-Drakensberg. The samples collected in-field along with digital soil mapping techniques were used to map the SOCs. The models were SoLIM’s rule based (RB) and sample based (SB), random forest (RF), least absolute shrinkage and selection operator (LASSO), regression kriging with cubist (RK-CB) and universal kriging. From the results, the mean SOC for the validation dataset of the study area was 12.44 kg organic carbon (OC) m−2. The best model was RK-CB (mean = 12.43 kg OC m−2), with R 2 and root mean square error (RMSE) of 0.61 and 4.01 kg OC m−2, respectively. The underperforming model was SoLIM-RB (mean = 13.27 kg OC m−2), with R 2 = 0.27 and RMSE = 5.75 kg OC m−2. The RK-CB model from this study significantly outperformed a region-scaled model, proving that site-specific studies in small catchments should be preferred to, especially if there are no soil data available for that area.

Study of soil organic carbon on current jhum and jhum fallows from Rawpuichhip, Mamit District

Jhum cultivation commonly known as shifting cultivation is the main form of agricultural practice in Mizoram. This gradually causes changes in the physico-chemical properties of soil. The study of soil organic carbon on current jhum and jhum fallows intends to find out the impact of jhum cultivation on soil organic carbon in relation to the period of jhum fallows. Soil samples were collected in triplicates from four different sites seasonally i.e. thrice in a year. The study was conducted within Rawpuichhip, Mamit i.e., Current Jhum, J and Jhum Fallows (which is categorized into two sites; Short fallow, SF - 2 to 5 years and Long fallow, LF - more than 8 years) and undisturbed area (adjacent forest) during the year 2022. Soil samples were collected in triplicates from three different depths 0-10 cm, 10-20cm, and 20-30cm with the help of a soil corer. It was found from the study that Soil Organic Carbon (SOC) value ranges from 1.21±0.17 % - 2.38±0.10 %. The results indicate that among the study area, short fallow has the least amount of SOC while current Jhum and the undisturbed area tend to have higher concentrations of SOC

Crop yields under no-till in Canada: implications for soil organic carbon change

Crop yields directly affect carbon (C) inputs into soils. Tillage management can influence crop performance, and as such should be considered when quantifying soil organic carbon (SOC) change, and thus net greenhouse gas emissions from croplands for national greenhouse gas inventory reporting. We conducted a meta-analysis of the effects of no-tillage (NT) and conventional tillage (CT) on crop yields for multiple crop species, soil types, and climatic regions of Canada. Yield response to NT varied between western and eastern Canada. Regardless of crop type, experiment duration, soil texture, and residue management, experiments in eastern Canada showed an average of 6% lower yields ( p ≤ 0.005) under NT compared to CT. In western Canada, crop type had an important effect on yields between NT and CT with wheat, canola, and legumes exhibiting 10% ( p ≤ 0.001), 7% ( p ≤ 0.05), and 9% ( p ≤ 0.05) higher yields on average under NT compared to CT, respectively. In western Canada, higher yields would be reflected in a similar scale of higher C inputs to NT systems. A recent meta-analysis of the effects of tillage management on SOC in Canada showed an 8% higher storage of SOC under NT systems compared to CT, a difference limited to western Canadian soils. Incorporating the effect of tillage on C inputs will lead to improvements in the accuracy of the effects of tillage management on SOC change in Canadian cropland. The activity data can be improved by applying weightings to the yield data by site-specific assessment of tillage practices across Canada.

Forest harvesting affects soil organic carbon and total nitrogen transports by facilitating landslides

Landslides considerably affect soil organic carbon (SOC) and total nitrogen (TN) transports. However, the quantitative assessment of these effects remain limited. Furthermore, it is unresolved how forestry practices, especially clearcutting and subsequent planting, affect the SOC and TN transports by facilitating landslides. Therefore, we quantified the SOC and TN transports attributable to landslides from 1948 to 2012 in a steep mountainous area in Japan and examined the impacts of forest clearcutting on SOC and TN transports through landslides. We used 12 aerial photographs and two LiDAR DEMs to identify the landslide areas and to estimate their scar depths. In addition, we sampled soil at 17 points to examine the relationship between SOC and TN and soil depth. Subsequently, we estimated the temporal changes in SOC and TN transports due to landslides and examined the relationships between forest age and rates of SOC or TN transport due to landslides. During the 64 years, the average annual rate of landslide was 3.7 × 10−2 ha km−2 yr−1. Large temporal variability existed in rates of landslide, and the maximum rate of landslide was around 11.0 × 10−2 ha km−2 yr−1, while almost no landslide occurred in some periods. The average annual SOC and TN transport rates were 5.8–9.3 MgC km−2 yr−1 and 0.5–0.9 MgN km−2 yr−1, respectively. Many landslides occurred at places where trees were 15 years old or less in plated forests. The amount of SOC and TN transports in landslide areas with < 20 forest age accounted for 87% of the total amounts moved owing to landslides. That is, our results clearly showed that forest harvesting increased landslide frequency and SOC and TN transport rates. We expect our results to be useful for predicting carbon stock in forest ecosystems and optimizing forestry practices in steep mountainous regions.

Improvement of Active Organic Carbon Distribution and Soil Quality with the Combination of Deep Tillage and No-Tillage Straw Returning Mode

During the initial period of straw return, a suitable straw return technology can lay the foundation for long-term soil fertility improvement. This study focused on the issues of backward straw return technology and blind fertilizer application in the southern part of the maize-producing area in the Northeast Plain of China. In this study, two straw return modes (2-year no-tillage straw cover + 1-year deep loosening and burying straw returning mode, NPT; 3-year rotary tillage and burying straw returning mode, RT), with RT mode as a control, were combined with different N fertilizer application rates (0, 192, 240 kg/ha). The changes in soil organic carbon (SOC) and its active components (MBC, DOC, and LOC) in the 0–40 cm soil layer were analyzed, and the carbon stratification rate, carbon pool index (CPI), SOC storages of each component, and maize yield were calculated to evaluate the short-term (3-year) differences in soil organic carbon quantity and quality in order to find suitable straw return methods and nitrogen application rate combinations. The results showed that the NPT mode increased the SOC and MBC content in the 20–30 cm soil layer, with an increase of 16.2% to 37.8% and 23.0% to 50.3%, respectively, compared with the RT mode. Under the NPT mode, the carbon pool stability was higher after nitrogen fertilizer addition, with a CPI value of 10.2% to 37.8% higher in the 20–40 cm soil layer compared with the RT mode. The differences in maize yield were not significant (p &lt; 0.05) between the nitrogen application rates of 192 kg/ha and 240 kg/ha, but the SOC storages did not show significant changes. The MBC storage had the highest value under the nitrogen application rate of 192 kg/ha. Therefore, we thought that, in the early stage of straw return, the organic carbon priming effect caused by increased microbial activity was higher under the nitrogen application rate of 192 kg/ha. Considering the aspects of not affecting maize yield and improving SOC stability, it is recommended to use the NPT mode with the application of a 240 kg/ha nitrogen fertilizer rate for straw return.

Analytical model for contaminants transport in triple composite liners with depth-dependent adsorption process

Predictions of contaminant transport in landfill composite liners are essential to assess the risk of groundwater pollution. The amount of soil organic carbon is strongly depth-dependent, which plays a crucial role in the adsorption of organic contaminants and heavy metal ions. The one-dimensional analytical model of contaminant transport in the triple composite liner consisting of geomembrane, geosynthetic clay liner and attenuation liner is presented considering the influence of depth-dependent adsorption coefficients. A specific sigmodal function is introduced to describe the attenuation of adsorption coefficients along the depth. The solution is obtained by the Laplace transformation. The analytical model was validated by experimental and numerical results. The results of the sensitivity analysis show that depth-dependent adsorption coefficients are critical for the risk assessment of groundwater pollution. The breakthrough time of composite liners can be overestimated by a folder of 2.5 with constant adsorption coefficients. The effects of parameters related to the depth-dependent adsorption process on the long-term transport of contaminants are critical for the design of a stable and effective composite liner system The proposed solution can capture the field observed data well and is consistent with the field observation. In addition, the proposed analytical solution may serve as a benchmark for various numerical models.

Assessment of above ground biomass and soil organic carbon in the forests of Nepal under climate change scenario

IntroductionMany factors, such as climate, topography, forest management, or tree/forest attributes, influence soil organic carbon (SOC) and above-ground tree biomass (AGTB). This study focuses on assessing relationship between various predictor variables and response variables (SOC and AGTB) in the perspective of climate change scenario. The study was conducted throughout in Nepal using forest resource assessment data (2010–2014).MethodsOur study applied a random forest model to assess the status of SOC and AGTB under future climate change scenarios using 19 bioclimatic variables accompanied by other variables such as altitude, aspect, basal area, crown cover development status, distance to settlement forest types, number of trees, macro-topography, management regime, physiographic zones, slope, and soil depth. The study used 737 (70%) samples as a training data for model development while 312 (30%) samples as a testing data for model validation.Results and discussionThe respective RMSE, RMSE% and adjusted R2 of the Random Forest Model for SOC estimation were found to be 9.53 ton/ha, 15% and 0.746 while same for the AGTB were 37.55 ton/ha, 21.74% and 0.743. Particularly, changes in temperature and precipitation showed an effect on the amount of SOC and AGTB in the projected scenario i.e., CMIP6, SSP2 4.5 for 2040–2060. The study found the amount of SOC decreased by 3.85%, while AGTB increased by 2.96% in the projected scenario. The proposed approach which incorporates the effect of bioclimatic variables can be a better option for understanding the dynamics of SOC and AGTB in the future using climatic variables.

Impact of Land Use Types on Soil Organic Carbon and Nitrogen Stocks: A Study from the Lal Bakaiya Watershed in Central Nepal

Understanding the role of soil carbon (C) dynamics and quantitative changes as affected by various land use patterns is very critical given the significance of carbon sequestration. In this context, the current study was conducted in the Lal Bakaiya watershed in Makawanpur District, Nepal, to assess the variation of soil organic carbon (SOC) and nitrogen (N) stocks in three different land use types, namely, natural forest, grassland, and cultivated land. Incremental soil depths method (i.e., 0–15 cm, 16–30 cm, and 31–45 cm) was applied to collect soil samples in bulk from each of the land use under the study to estimate SOC and N stocks in laboratory. A total of 90 soil samples were collected from three soil layers down the soil profile up to 45 cm for each land uses. The results show that both SOC and N contents decreased with soil depths; however, substantial amount of SOC and N stocks were reported in lower soil depths under land use with natural forest. Both SOC and N contents were found relatively higher at 0–15 cm depth in natural forest soil (1.40 ± 0.20% and 0.26 ± 0.04%) than those in grassland and cultivated land, respectively. The mean total SOC stock and N stock ranged from 46.3 ± 4.24 t ha−1 and 7.11 ± 1.86 t ha−1 in cultivated land to 62.05 ± 9.17 t ha−1 and 11.40 ± 1.92 t ha−1 in the land use with natural forest, respectively. Furthermore, the mean total carbon and nitrogen ratio (C/N ratio) of the soil was found to be higher in cultivated land (7.07 ± 1.93) than that in natural forest (5.75 ± 1.47) and grassland (5.62 ± 1.49), respectively. Two-way analysis of variance results showed that both land use type and soil depth have significantly ( p &lt; 0.05 ) affected the SOC and N stocks in the study. From the results, it is suggested that well-managed land use can contribute significantly in offsetting global carbon emission.

Effects of fertilizer application strategies on soil organic carbon and total nitrogen storage under different agronomic practices: A meta‐analysis

AbstractFertilizer application strategies can impact soil health, mainly soil organic carbon (SOC) and total nitrogen (TN) sequestration, which are essential in mitigating climate change. Many studies have been conducted on the influence of fertilizer use on SOC and TN storage. Results can, however, be variable in different sites because of various management practices and environmental conditions; therefore, we conducted a global meta‐analysis of 953 observations from 143 papers on the impact of different fertilizers (mineral N (NF), manure (Mn) and mixed fertilizers (MNF: combination of mineral and organic fertilizer)) on SOC and TN storage under various cropping systems and environmental conditions in agricultural land. The results showed that MNF led to the greatest SOC and TN stocks. Noticeably, animal Mn sequestered higher amounts of SOC and TN compared to green Mn. In addition, MNF increases SOC in the medium term (10–20 years, 43.71%) and TN in the short term (0–10 years, 40.85%), which could be related to their nutrient's cycles and residence time in the soil. The higher effectiveness of SOC and TN sequestration (12.84% and 27.42%, respectively) under NF was observed at high rates &gt;250 kg N/ha in comparison to low rates of 0–250 kg N/ha. A significant SOC increment was observed with MNF (37.76%) and Mn (19.45%) under continuous cropping (monoculture) than crop rotations. In contrast, TN was higher with MNF (58.31%) and Mn (18.23%) with crop rotations. The subhumid and semi‐arid zones had greater increase in SOC (28.24%) and TN (74.54%) stock in comparison to other climatic conditions. Overall, this study emphasized that MNF could optimize SOC and TN storage in agricultural soils depending upon edaphic and regional climatic conditions.

Sesbania - A Green Manure for Soil Productivity and Crop Enhancement

In order to determine how growing the green manure crop Dhaincha (Sesbania sesban) in acidic soil conditions affected the soil characteristics, nutrient availability, and rice productivity, among other things, a field study was conducted in the crop cafeteria at Galgotias University's School of Agriculture in Greater Noida, Uttar Pradesh from July 2019 to July 2022. As per the study, the green manure performed patch considerably increased the change in the soil physical qualities and availability of nutrients. In comparison to plots where Sesbania sesban was not grown-up as a green manure crop in the introduction of Sesbania sesban increased paddy output. The field investigation, which was carried out in the university's cafeteria in 2018, discovered that the soil's pH was 8.75, slowly and steadily improving to 8.0. The amount of soil organic carbon was low in 2018 at 0.27, 0.35 in 2019, 0.39 in 2020, and 0.45% in 2021, respectively. The application of green manure, vermi-compost, cow dung manure, gypsum, and Sesbania (Sesbania sesban) as part of an approved scientific method led to an improvement in soil quality. This also led to an increase in the production of agricultural crops.

Biochar‐based nutrient management as a futuristic scalable strategy for C‐sequestration in semiarid tropics

AbstractClimate and agriculture experts emphasize the need to develop a carbon sink in the soil to help alleviate the effects of climate change. A 2‐year field experiment in semiarid tropical drylands tested sustainable nutrient management approaches to sequester carbon in the soil. We analyzed nine different treatments, including chemical fertilizers (as blanket and soil test‐based [STB] recommendations), sole organic (biochar and compost), and their combinations (with 75% and 50% STB recommendation) as integrated applications (integrated nutrient management [INM]) in the maize–chickpea cropping sequence. We report that biochar treatments show higher (24%–30%) organic carbon stock in the top layer of soil than the respective compost treatments. Furthermore, the biochar‐based INM showed the maximum residual effect in chickpea (Cicer arietinum L.) crops. The system equivalent yield showed the best results (8 Mg ha−1) for 50% need‐based fertilizer and 50% biochar. Although we observed that sole‐biochar sequestered the highest amount of soil organic carbon (0.69%) in the topsoil compared to the other treatments, it was not scalable due to the lower yield for maize crops. Similarly, composts showed more labile carbon concentrations as microbial biomass but lagged behind biochar treatments for organic carbon storage. The system performance expressed as net returns and benefits–cost ratio also showed better results for biochar‐based INM. The findings show that drylands facing widespread land degradation in terms of nutrient imbalances and low C levels will benefit from an integrated approach of need‐based fertilizer with biochar application. Therefore, this might be a long‐term sustainable strategy for C‐sequestration and food security for semiarid tropical drylands.

Warming-dominated climate change impacts on soil organic carbon fractions and aggregate stability in Mollisols

Mollisols contain high amounts of soil organic carbon (SOC), which is highly susceptible to climate change; thus, climate change could indirectly influence soil aggregate stability, but the dominant factor affecting aggregate stability remains controversial. Here, a soil transplanting test from high-latitude to low-latitude locations was initiated in 2004 to investigate the influences of warming-dominated climate change (approximately 3–4.7 ℃) on the quantity and molecular composition of OC fractions in surface (0–20 cm) soils, aggregate stability changes and underlying mechanisms. Different initial soil organic matter (SOM) contents of 50.6 g kg−1 (SOM5), 58.8 g kg−1 (SOM6), and 108.9 g kg−1 (SOM11) were established in situ soils and in transplanted soils to simulate warming. The 15-year warming-dominated climate change presented no noticeable change in the SOC content in the lower SOM Mollisols (SOM5 and SOM6) but increased the SOC content by 13.3% in the higher SOM Mollisol (SOM11). In terms of labile OC fractions, warming-dominated climate change significantly increased the dissolved organic carbon (DOC) content by 20.1%–47.7% but reduced the easily oxidizable organic carbon (EOC) and microbial biomass carbon (MBC) contents by 22.1%–33.6%. Irrespective of any treatment, warming-dominated climate change decreased soil aggregate stability, as evidenced by the reduction in mean weight diameter (MWD) and geometric mean diameter (GMD) of 41.7%–79.3% and an increase in fractal dimension (D) of 28.6%–58.5%. For hierarchically organized soil aggregates, warming-dominated climate change increased the proportion and OC content of particulate organic matter inside free microaggregates (Fm-POM) as well as nonaggregated silt + clay-sized organic matter (nA-MOM). However, climate change decreased the proportion and OC content of silt + clay-sized fractions inside microaggregates within macroaggregates (mM-MOM). Of importance, warming-dominated climate change increased the amount of carbohydrates and decreased the amount of lignin in the mM-MOM, Fm-POM, and nA-MOM fractions. Therefore, we speculated that chemical protection by mineral association within macroaggregates and nA-MOM fractions and physical protection by the occlusion of POM within free microaggregates might be the primary mechanisms for SOC stabilization under long-term climate change in Mollisols. The long-term warming-dominated climate change results demonstrated a positive effect on SOC content in higher SOM Mollisols, DOC, carbohydrate C, free microaggregate-associated C and nonaggregated silt + clay-sized associated C but exhibited a negative effect on EOC, MBC, lignin C, silt + clay-sized inside microaggregates within macroaggregates C and aggregate stability. These variables all contributed to the reduction in soil aggregate stability and might act as sensitive indicators of warming-dominated climate change in Mollisols, which in turn affect farmland ecosystem C fluxes in response to further climate change.

Temporal dynamics of density separated soil organic carbon pools as revealed by δ13C changes under 17 years of straw return

Straw return is widely recommended as an effective measure to increase the amount of soil organic carbon (SOC) and improve soil fertility in agroecosystems. However, the temporal dynamics of the original and newly derived SOC during long-term straw return remain uncertain. This study aimed to (i) determine the temporal dynamics of original and newly derived SOC in various soil organic matter (SOM) fractions during cultivation and (ii) evaluate the effect of continuous straw return on the contents of original and newly derived SOC. These aims were achieved by analyzing topsoil samples (0–20 cm) in a 17-year field experiment using a continuous maize (Zea mays L.) cropping system. Three fertilizer treatments were tested: no fertilizer (NF), mineral fertilizer (NPK), and mineral fertilizer with straw return (NPKS). The SOC was physically separated into three density fractions: the free light fraction (fLFOC), occluded light fraction (oLFOC), and heavy fraction (HFOC), and their δ13C values were determined. The original and newly derived SOC of each fraction and the rate of conversion of exogenous C inputs were evaluated. The SOC content in the bulk soil and C fractions generally increased continually with cultivation time in the NPKS, indicating that the soil had not reached maximum C sequestration. NPKS significantly increased the C contents of fLFOC, oLFOC, and HFOC by 38.6%, 43.0%, and 11.6%, respectively, relative to the initial soil after the 17-year experiment. The newly derived SOC content was significantly higher in NPKS than in NF and NPK, and the rate of conversion of exogenous C inputs to SOC was the lowest in NPKS. The annual rate of loss of original SOC in NPKS was lowest for the light fractions (fLFOC and oLFOC) and highest for HFOC, implying that the return of straw moderated the mineralization of original SOC in the light fractions but increased the decomposition of original SOC in the heavy fraction via the priming effect (PE). The average rate of conversion of exogenous C inputs remained the highest in HFOC (23.5%), lowest in oLFOC (0.6%), and intermediate in fLFOC (4.1%) throughout the study. Thus, the stable HFOC pool retained more straw C, despite the stronger PE. Our results demonstrated that long-term straw return continuously increased the proportion of new SOC in the bulk soil and density fractions and increased the decomposition of the original SOC in the stable SOC fractions. These findings provide further detailed insights into the mechanisms of SOC stabilization in agricultural soils.

Quantifying soil organic carbon (SOC) density and stock in the Urmodi River watershed of Maharashtra, India: implications for sustainable land management

Soil Organic Carbon (SOC) plays a vital role in the global carbon cycle, affecting soil fertility and agricultural sustainability. Our study focused on areas with low SOC, where increasing its levels could enhance soil health and carbon management. We used an earth science approach to analyze SOC density and stock in different land classes of the Urmodi River watershed in Maharashtra, India. Using GIS, we estimated SOC from soil samples collected up to 20 cm depth, and produced maps of SOC, SOC density (SOCD), and SOC stock. Our results showed that natural vegetation areas, such as closed and open forests, had a higher nutritional status of SOC and SOC stock, indicating the importance of land cover history on soil health. We found the average SOC to be 1.4 g/kg−1, SOCD to be 57.36 kg/m−2, SOC stock to be 3.46 ton/ha−1. We also depicted the relationship between elevation and SOCD using a scatterplot, revealing the distribution of SOC across different elevations. Our study demonstrates the use of modern geoscientific analysis tools to understand the physical and chemical properties of soil, which can be useful in assessing soil health. Overall, our results provide valuable insights into the distribution of SOC and its relationship with other geo-chemical aspects at a regional scale.

Characteristics and utilization of black soils in Indonesia

Black soils store a high amount of soil organic carbon (SOC) and play a crucial role in climate change, food security, and land degradation neutrality. However, data and information regarding black soils in tropical regions, including Indonesia, are limited. This study aimed to characterize and identify the utilization of black soils in Indonesia based on legacy soil survey data. We collated 142 soil pedon samples of Mollisols from articles, technical reports, and existing datasets. The site information (site position, elevation, land use type, parent material) and selected physicochemical properties were stored in a spreadsheet, from which exploratory data analysis was conducted. The result showed that the median SOC content was 1.53%, ranging from 0.6 to 8.2 %; cation exchange capacity was 30 cmol kg&lt;sup&gt;-1&lt;/sup&gt;, ranging from 9 to 95 cmol kg&lt;sup&gt;-1&lt;/sup&gt;; base saturation was 87%, ranging from 11 to 100 %; and bulk density was 1.21 g cm&lt;sup&gt;-3&lt;/sup&gt;, ranging from 1.13 to 1.36 g cm&lt;sup&gt;-3&lt;/sup&gt;. Other soil characteristics (particle size distribution, exchangeable bases, pH, pore, and water retention) varied with horizon type and land use/land cover. The black soils have been used for paddy fields, dryland farming, and gardens with low management intensity. Main cultivated crops include rice (&lt;em&gt;Oryza sativa&lt;/em&gt;), corn (&lt;em&gt;Zea mays&lt;/em&gt;), cassava (&lt;em&gt;Manihot esculenta&lt;/em&gt;), sweet potato (&lt;em&gt;Ipomoea batatas&lt;/em&gt;), and nutmeg (&lt;em&gt;Myristica fragrans&lt;/em&gt;), clove (&lt;em&gt;Syzygium aromaticum&lt;/em&gt;), coconut (&lt;em&gt;Cocos nucifera&lt;/em&gt;), and cocoa (&lt;em&gt;Theobroma cocoa)&lt;/em&gt;. Threats to black soil functions include soil erosion, carbon loss, and nutrient imbalance. Soil and water conservation measures, integrated soil nutrient management, and agroforestry are among the best land management practices for black soils.

Fire effects on soil carbon cycling pools in forest ecosystems: A global meta-analysis

Changes in soil carbon (C) pools driven by fire in forest ecosystems remain equivocal, especially at a global scale. In this study we analyzed data from 232 studies consisting of 1702 observations to investigate whether ecosystem type, climate zone, stand age, soil depth, slope, elevation, and the time since fire in influence of forest soil carbon pools to fire regime (fire type, fire season, fire intensity). Additionally, we explored the potential mechanisms of the relationships between multiple response variables to the fire using linear regression and random forest models. On aggregate, fires significantly increased the mean effect sizes of several key soil carbon cycling components-including microbial biomass carbon (MBC), dissolved organic carbon (DOC), total carbon (TC), pyrogenic carbon (PyC), soil organic matter (SOM), soil organic carbon (SOC) by 0.77, 0.89, 0.87, 1.22, 0.97 and 0.93, respectively, compared to unburned forests ecosystems. However, the fire effects on soil C pools vary widely between environmental factors and duration, and are mediated by factors such as tree species, fire type, and soil layer. A correlation analysis displayed the effects of fire on MBC and DOC were significantly and negatively correlated with elevation. Fire effects on the forest floor and mineral soil indicated significantly increased PyC. SOC and TC in coniferous tree species are the most sensitive to fires, thereby altering important feedback relationships with the fire-vegetatale-climate system. Interestingly, latitude has a stronger influence on SOC than mean annual precipitation or elevation, indicating that variations in latitude play a significant role in regulating the amount of SOC in forest ecosystems. Overall, the results illustrated geographic variation in fire effects on soil C cycling underscores the need for region-specific fire management plans, and help us understand the responses of soil C cycling to fire in forest ecosystems, and facilitate decision-making to forest fire management.

Changes in soil organic carbon and nutrient pools in aggregate‐sized fractions along a chronosequence of wolfberry (Lycium barbarum L.) plantations in arid areas of Northwest China

AbstractDifferent land use and management actions can affect soil aggregates (SAs) and nutrient stocks, which are crucial for sustainable agriculture. The impacts of various chrono‐sequences on the soil aggregate structure, soil organic carbon (SOC) and nutrients associated with aggregate fractions in wolfberry (Lycium barbarum L.) plantations are still not fully understood. This study examined the composition and stability of SAs, SOC, total nitrogen (TN), available phosphorus (AP) and exchangeable cations (K+, Na+, Ca2+ and Mg2+) in bulk soil and various aggregate‐size fractions from five wolfberry plantations with varying ages (1, 4, 6, 10 and 13 years) and a corn field (0 years) in the arid region of northwest Ningxia in China. The results indicated that silt–clay (&lt;53 μm) fractions were dominant in the soil, accounting for 51%–66%, under different plantation ages. The proportion of the macro‐aggregates (&gt;250 μm) increased significantly, by 40%–47%, over the 4 years of wolfberry plantation. Likewise, the soil aggregate stability was improved, and total exchangeable bases (TEB) along with numerous cations concentrations (K+, Na+, Ca2+ and Mg2+) in SAs were significantly reduced as the wolfberry plantings became older. Both concentrations of SOC and TN in the soil aggregates peaked in the 13th year. The silt–clay fractions stored a considerable amount of SOC and nutrients. However, short‐term (under 6 years) cultivation of wolfberry reduced the stocks of SOC, TN and AP in the soil, while long‐term (over 10 years) cultivation increased them, particularly in macro‐aggregates. These findings indicated that long‐term wolfberry farming had several advantages, such as enhancing soil structure, accumulating SOC and nutrients and ameliorating alkaline soils, especially after 10 years, in the arid northwest of China.