Soil Organic Carbon Sequestration Potential Research Articles

Modeling soil organic matter changes under crop diversification strategies and climate change scenarios in the Brazilian Cerrado

In Brazil, land conversion and agricultural management have historically accounted for the largest share of the country's greenhouse gas (GHG) emissions, with the Cerrado region being one of the most affected areas. Although cropping diversification has been proposed as a potential strategy to mitigate GHG emissions through soil organic carbon (SOC) sequestration, the long-term effects of these systems in the Cerrado are unknown. The DayCent model was used to simulate the impact of crop diversification and tillage on SOC dynamics until 2070 (∼50 years), including common crop succession systems and crop rotations associated with cover crops under climate change scenarios. First, we calibrated and evaluated the DayCent model using plant and soil observations from three sites in the region, where Pearson coefficients (r values) ranged from 0.50 to 0.94 (calibration sites) and 0.53–0.99 (validation site) for crop yields, SOC, and nitrogen. We then used the model to investigate how cropping systems and climate interact to control SOC levels. Results indicate that SOC stocks would decrease under the long-term (∼50 years) soybean-cotton succession, regardless of soil management (-0.04 to −0.17 Mg C ha−1 year−1). Crop diversification with crop rotation and cover crops (i.e., millet, ruzigrass, sunn hemp) had the highest SOC accrual potential (∼0.71 Mg C ha−1 year−1), resulting in SOC stocks of up to 130 Mg C ha−1 by 2070. Ruzigrass, either single or intercropped with maize on crop succession systems, showed substantial potential for SOC sequestration (∼0.55 Mg C ha−1 year−1) and could be a viable strategy if implementing more complex rotations is not feasible. The SSP2 – 4.5 and SSP5 – 8.5 climate change scenarios increased SOC stocks by 6.3 and 8.2 % in SOC across treatments by 2070, respectively. Results suggest that diversified cropping systems are a promising strategy for increasing SOC sequestration, and they offer valuable guidance for enhancing current management practices in the region.

Soil organic carbon and total nitrogen stocks related to land use and basic environmental properties − assessment of soil carbon sequestration potential in different ecosystems

Soil organic carbon (SOC) and total nitrogen (TN) stocks are crucial for the development of wild plants and crops. This paper examines the current SOC and TN stocks and their variability within land uses under different environments, assessing the relationships between SOC and TN stocks with basic environmental properties and quantifying the magnitude of SOC sequestration potential for a better land use management. We studied 991 soil profiles, from steppe to wet mountain-soils. The land use was essential in influencing soil organic C and total N stocking, with the forestland showing the significantly highest SOC stocks specifically in mountain soils, followed by grassland and cropland. Altitude, clay content, pH and plant available phosphorous and potassium were other influencers of SOC and TN stocks. The best predictive multiple linear regression model explained 68 % of the 0.5 m depth SOC stock variability for forest, 61 % for grassland and 37 % for cropland, while Random Forest model explained 70 %, 65 %, and 28 % for the same land uses. The obtained models rank factors contribution and may be useful in management. Lands having the highest C sequestration potential occurred within fine-textured soils, mainly in croplands. The most favorable soil depth for further C sequestration is below C-saturated topsoil and this could be achieved by deep-rooting crops and conservative technologies. Additionally, changing some low-fertile soils of cropland into forestland or grassland would improve SOC sequestration. These measures might contribute to sequester additional C amounts in soils, in order to bolster initiatives for climate-change mitigation and adaptation.

Triple impact: Biochar, no-tillage, and cover crops for soil carbon enhancement and climate resilience in soybean farming

With the dissemination of conservation agriculture, no-tillage (NT) and cover crops have widely been adopted globally. However, their effects on greenhouse gas (GHG) emissions are controversial. Biochar is posited to mitigate climate change by increasing carbon (C) sequestration and decreasing GHG emission in soil. To investigate the comprehensive effect of NT, cover crops, and biochar on soil organic carbon (SOC) sequestration and net global warming potential (GWP), a split-split-plot experiment was conducted. The experiment involved various combinations of two tillage methods (NT; Moldboard plowing, MP), two cover crop treatments (Fallow, FA; Rye, RY), and two biochar treatments (with biochar application, WB; no biochar application, NB). NT and RY demonstrated a trend of increasing N2O emission, while WB tended to reduce the N2O emission in NT plots. NT–RY–WB increased the SOC stock (0–30 cm) by 23.2% in 2020 and 30.2% in 2021 compared with MP–FA–NB, indicating that this combination promoted C sequestration. Due to the heightened SOC stock, the net carbon dioxide (CO2) retention effectively compensated the GWP arising from non-CO2 emissions. Consequently, the triple combination of NT, RY and WB positively contributed to a decreased net GWP in the soybean field (−1231 kg CO2 equivalent ha−1 year−1 in 2020 and −2767 kg CO2 equivalent ha−1 year−1 in 2021). These findings highlight the considerable potential of the combined NT–RY–WB for SOC sequestration and net GWP decrease, positioning it as an environmentally beneficial agricultural system for mitigating climate change in Asia’s long-term food production.

Accumulation of soil microbial necromass carbon and its contribution to soil organic carbon after vegetation restoration in the Tibetan Plateau

Vegetation restoration has been proved as an effective strategy to increase soil organic carbon (SOC) sequestration in degraded ecosystems. However, due to different vegetation restoration practices and climate zones, changes of SOC content, dynamics, sources and their controlling mechanisms after vegetation restoration remain inadequately addressed. Taking the advantage of four-year vegetation restoration, we explored the effects of vegetation restoration on SOC through its fractions, soil aggregates, soil enzymes and microbial necromass contribution to SOC in a desertification region in the Tibetan Plateau (TP). Results showed that vegetation restoration increased SOC contents by 68% for 0 – 10cm, 29% for 10 – 30cm and 11% for 30 – 50cm compared to site without vegetation restoration. Vegetation restoration increased soil macroaggregates (> 0.25mm) and decreased soil microaggregates (0.53 – 0.25mm), but increased their associated SOC contents. Meanwhile, vegetation restoration enhanced microbial necromass and its contribution to SOC. Structural equation model revealed that increasing microbial necromass carbon, changing soil aggregates and their associated SOC were the main mechanisms of increasing SOC content after vegetation restoration. Our result further indicated a large potential of SOC sequestration through vegetation restoration in the TP. These findings have important implications for natural based solution for carbon neutrality for China.

Soil Organic Carbon Sequestration Potential and Its Sustainability Comparison Between Mango-based Agroforestry and Cropland Seeking Soil Fertility Parameters Under Climate Resilience

Soil Organic Carbon Sequestration Potential and Its Sustainability Comparison Between Mango-based Agroforestry and Cropland Seeking Soil Fertility Parameters Under Climate Resilience

Soil Vertical Distribution of Organic Carbon and Sequestration Potential in Ponte de Lima (Alto Minho Region, Northern Portugal)

ABSTRACT Understanding the vertical distributions of organic carbon (OC) is crucial for predicting and simulating the influences of soil units on the terrestrial carbon cycle. The OC in the fine earth fraction was calculated for the soil units Anthrosols, Cambisols, Fluvisols, Leptosols, and Regosols in the municipality of Ponte de Lima, Portugal, at depths of 0–30 cm, 0–100 cm, 0–200 cm, and 0–2590 cm. In the study area, over 40% of the OC is concentrated in the Regosol unit, followed by the Anthrosols with over 23% OC at all depths, and the Leptosols with over 22% OC at all depths. The soil units Cambisols and Fluvisols have a lower representation in the territory, with values below 1.5% and 6.5% respectively at all depths. The obtained results contribute to assessing the potential of the soil units present in the municipality to sequester CO2, promoting the development of carbon inventories and analyzing the distribution of OC through accurate and reliable estimates of current C reserves as an essential tool for analyzing and modeling the effects of different factors involved in the potential of soil OC sequestration.

Soil organic carbon sequestration potential explained by mineralogical and microbiological activity using spectral transfer functions

The ability of soil to sequester carbon and reduce atmospheric CO2 concentrations is limited and depends on the soil minerals and their interaction with the microbiota. Microbial activities are closely associated with the types and amounts of soil organic matter (SOM) and clay minerals that have functional groups that interact with energy in Vis NIR-SWIR and Mid-IR wavelengths. The main objective of this research was to determine, based on these spectral ranges, the relation between mineralogical and organic compounds, as their sequestration and specialization in soils from Brazil. It was possible to map microbiological activity by spectral transfer functions and digital soil mapping reaching R2 from 0.77 to 0.85. Multiple regression equations were constructed to quantify enzymatic activity, microbial biomass carbon (MBC), particulate organic matter (POM), and resistant forms of carbon, and SOM associated with the mineral fraction (MAOM). All these properties were detected by specific bands obtained with the recursive feature elimination (RFE) algorithm, reaching correlations from 0.64 to 0.98 in specific ranges. The prediction model of the carbon sequestration potential was adjusted with microbiological and mineralogical variables from Vis-NIR-SWIR and the Mid-IR spectral range. A SARAR double autoregressive model was adjusted with r 0.61 and to a spatial error model (SEM) with r 0.7. The explanatory variables were associated with kaolinite, hematite, goethite, gibbsite, and the abundance of fungi, actinomycetes, vesico-arbuscular mycorrhizal fungi, enzymatic activity of beta-glucosidase, urease and phosphatase, and POM. Among the microbiological variables, the general abundance of fungi was the most important, in contrast to enzymatic activity that was the least important. The interaction between the different maps constructed and historical land use allowed the identification of areas that contribute to sequestering new carbon and could be the key to climate change mitigation strategies.

Carbon sequestration potential and its main drivers in soils under alfalfa (Medicago sativa L.)

As a perennial forage crop, alfalfa (Medicago sativa L.) has been extensively utilized for the vegetation restoration of degraded soil and provides feedstock for forage. Its high usage can be attributed to its high yield potential and the increasing soil organic carbon (SOC) sequestration of alfalfa cultivation. However, the impact of land conversion to alfalfa on SOC content and its underlying drivers remain unclear. We performed a meta-analysis at the global scale to explore the quantified effects of alfalfa cultivation on SOC content and identify its controlling factors. We employed 1699 pairwise data points from 90 publications based on cropland/abandoned land conversion to alfalfa. Globally, cropland (cropland-alfalfa) and abandoned land (abandoned land-alfalfa) conversion to alfalfa enhanced SOC content by 12.1 % and 13.7 %, respectively. Alfalfa exhibited greater SOC content benefits in the surface soils (0–20 cm) with a lower level of initial SOC (<16 g kg−1), regardless of the land conversion type. Cropland-alfalfa was observed to increase SOC content with fertilization, irrigation, and conventional tillage in the long term (>5 years). Furthermore, abandoned land-alfalfa enhanced SOC content in the absence of alfalfa biomass removal and for longer cultivation durations (>5 years). Boosted regression tree analyses indicated variations in soil properties (75 % for cropland-alfalfa and 65 % for abandoned land-alfalfa) as the primary factors driving changes in SOC content. The dominant drivers were determined as the soil layer (51.6 %), cultivation duration (13.1 %), and initial SOC (12.9 %) for cropland-alfalfa, and initial SOC (43.7 %), soil layer (24.6 %) and cultivation duration (17.1 %) for abandoned land-alfalfa. Land conversion to alfalfa has great potential for SOC sequestration, particularly in low-fertility soils. Therefore, alfalfa cultivation is highly recommended for degraded lands due to its SOC sequestration benefits in vegetation restoration.

Maps of Soil Organic Carbon Sequestration Potential in the Russian Croplands

Adoption of the farming systems that aim to sequester carbon in agricultural soils is one of the ways to mitigate global climate change. This study focuses on the estimation of organic carbon sequestration potential of the Russian croplands in the upper (0–30 cm) soil layer by creating a set of maps using the data from global and national databases as the input data. The maps are generated within the FAO Global Soil Organic Carbon Sequestration Potential Map (GSOCseq) project according to the unified methodology using the RothC model to predict the rate of carbon sequestration in 2020–2040 under a business as usual scenario (BAU), as well as under sustainable soil management scenarios with additional different C input (+5, +10, and +20%) resulting from the use of sustainable soil management (SSM) scenarios. The total potential sequestration rate by the croplands of the Russian Federation in the 0–30-cm layer under a BAU scenario is assessed at 8.5 Mt/year and the estimate under SSM scenarios, up to 25.5 Mt/year. The carbon sequestration by the cropland of each soil ecological zone (except for the light chestnut (Eutric Cambisols (Protocalcic)) and brown semidesert (Luvic Calcisols) soils, where it is around zero) and on a national scale is positive. The Altai krai, Omsk oblast, Novosibirsk oblast, and Krasnoyarsk krai have the greatest potential for sequestration. Several subjects of the Russian Federation—Krasnodar krai, Republic of Crimea, Rostov oblast, Primorskii krai, Republic of Adygea, and Kaliningrad oblast—demand the adoption of sustainable management of soil resources.

Estimating soil organic carbon sequestration potential in the Chinese Mollisols region

AbstractMollisols region of China is a ballast stone of Chinese food security. In this study, 484 soil organic carbon (SOC) data points from the documented soil surface (0–20 cm) samples in the typical Chinese Mollisols region were selected. The regional soil fertility was divided into high, medium, and low levels based on the SOC content from the long‐term positioning fertilization stations in Shenyang, Harbin, and Hailun of Northeast China. Furthermore, the regional SOC balance point (SOCb) model was built driven by the factors of annual mean temperature, annual precipitation, annual effective accumulative temperature, the ratio of precipitation and temperature, soil clay content, and pH. Using geographic information systems (GIS) interpolation method, the regional mean SOCb and SOC sequestration potential (SOCsp) at the SOCb's status were simulated to be 40.10 g kg−1 and 10.71 kg m−2, respectively. Moreover, the SOC content increased (SOCc) and the SOC sequestration capacity increased of medium‐ or low‐fertility soil were evaluated by GIS subtraction. Consequently, the means of SOCc in medium‐ and low‐fertility soils could be 16.88 g kg−1 and 26.79 g kg−1, respectively. Furthermore, the means of SOCsp in medium‐ and low‐fertility soils could be 4.30 kg m−2 and 7.43 kg m−2, respectively. The sensitivity analysis of this model showed that the high SOCb area was distributed in study region with low temperature, dry, high clay content, and low pH. The results provide an actual perspective on estimating regional SOCsp and soil fertility promotion target induced by the different soil fertility levels.

The Effect of Long-Term Crop Rotations for the Soil Carbon Sequestration Rate Potential and Cereal Yield

Depending on the type of agricultural use and applied crop rotation, soil organic carbon accumulation may depend, which can lead to less CO2 fixation in the global carbon cycle. Less is known about organic carbon emissions in different crop production systems (cereals, grasses) using different agrotechnologies. There is a lack of more detailed studies on the influence of carbon content in the soil on plant productivity, as well as the links between the physical properties of the soil and the absorption, viability, and emission of greenhouse gases (GHG) from mineral fertilizers. The aim of this study is to estimate the long-term effect of soil organic carbon sequestration potential in different crop rotations. The greatest potential for organic carbon sequestration is Norfolk-type crop rotation, where crops that reduce soil fertility are replaced by crops that increase soil fertility every year. Soil carbon sequestration potential was significantly higher (46.72%) compared with continuous black fallow and significantly higher from 27.70 to 14.19% compared with field with row crops and cereal crop rotations, respectively, intensive crop rotation saturated with intermediate crops. In terms of carbon sequestration, it is most effective to keep perennial grasses for one year while the soil is still full of undecomposed cereal straw from the previous crop. Black fallow without manure fertilization, compared to crop rotation, reduces the amount of organic carbon in the soil up to two times, the carbon management index by 2–5 times, and poses the greatest risk to the potential of carbon sequestration in agriculture.

Assessment of carbon sequestration potential of mining areas under ecological restoration in China

Mining activities aggravate the ecological degradation and emission of greenhouse gases throughout the world, thereby affecting the global climate and posing a serious threat to the ecological safety. Vegetation restoration is considered to be an effective and sustainable strategy to improve the post-mining soil quality and functions. However, we still have a limited knowledge of the impact of vegetation restoration on carbon sequestration potential in mining areas. In this pursuit, the present study was envisaged to integrate the findings from studies on soil organic carbon (SOC) sequestration in mining areas under vegetation restoration with field monitoring data. The carbon sequestration potential under vegetation restoration in China's mining areas was estimated by using a machine learning model. The results showed that (1) Vegetation restoration exhibited a consistently positive impact on the changes in the SOC reserves. The carbon sequestration potential was the highest in mixed forests, followed by broad-leaved forests, coniferous forests, grassland, shrubland, and farmland; (2) The number of years of vegetation restoration and mean annual precipitation were found to be the important moderating variables affecting the SOC reserves in reclaimed soils in mining areas; (3) There were significant differences in the SOC sequestration potential under different vegetation restoration scenarios in mining areas in China. The SOC sequestration potential reached up to 9.86 million t C a−1, when the soil was restored to the initial state. Based on the meta-analysis, the maximal attainable SOC sequestration potential was found to be 4.26 million t C a−1. The SOC sequestration potential reached the highest level of 12.86 million t C a−1, when the optimal vegetation type in a given climate was restored. The results indicated the importance of vegetation restoration for improving the soil sequestration potential in mining areas. The time lag in carbon sequestration potential for different vegetation types in mining areas was also revealed. Our findings can assist the development of ecological restoration regimens in mining areas to mitigate the global climate change.

Responses of SOC, labile SOC fractions, and amino sugars to different organic amendments in a coastal saline-alkali soil

Organic amendment combined with mineral fertilizer is known as an effective management practice to improve soil carbon (C) sequestration in cropland. We evaluated the effects of three organic amendments combined with mineral fertilizer on soil organic carbon (SOC), labile SOC fractions, amino sugars, C mineralization, and C-cycle enzyme activities in a coastal saline-alkali soil. The three amendments, including straw (C/N of 75.5:1), straw biochar (C/N of 43:1), and soybean cake (C/N of 7.4:1), were continuously added into the soil at an equal C amount of 2250 kg C ha−1 for four years. Compared to mineral fertilizer alone, the contents of SOC in plots receiving straw, straw biochar, and soybean cake were increased by 7.6%, 17.3%, and 12.7%, respectively. The amendment of straw biochar mainly increased easily oxidizable carbon (EOC), particulate organic carbon (POC), and fungal-derived glucosamine, whereas straw and soybean cake mainly increased dissolved organic carbon (DOC), microbial biomass carbon (MBC), and bacteria-derived muramic acid. Meanwhile, the activities of C-cycle enzymes and C mineralization were higher in straw and soybean cake treatments than in straw biochar treatment. EOC and POC, but not DOC and MBC, were strongly positively correlated with fungal-derived glucosamine and SOC, suggesting that EOC or POC could be used as appropriate indicators to predict SOC sequestration potential. In addition, the C/N ratio of organic material did not affect SOC and its components. In conclusion, straw biochar promotes the maximum accumulation of SOC through increasing EOC, POC, and fungal necromass.

Soil taxonomical classification and organic carbon sequestration potential of coastal acid sulfate soils: Kari and Kayal ecosystems of Kerala, India

Soil taxonomical classification and organic carbon sequestration potential of coastal acid sulfate soils: Kari and Kayal ecosystems of Kerala, India

Effects of land use/cover changes on soil organic carbon stocks in Qinghai-Tibet plateau: A comparative analysis of different ecological functional areas based on machine learning methods and soil carbon pool data

Understanding the process of land use/cover changes (LUCC) can provide experience on the enhancement of soil organic carbon (SOC) stocks and carbon sequestration potential for different areas. This study is uniquely to divide different ecological functional areas, and originally combine the machine learning method and soil carbon pool dataset for regional comparative analysis, to compare and quantitatively analyze the drivers of LUCC and the changes in SOC stocks effected by LUCC over 30 years. The results show that topography and climate changes are the main drivers affecting LUCC in four natural areas, while soil factors and population changes do not cause significant effects. The total SOC stocks in Qinghai was increased by 71.18 Tg C and 107.19 Tg C in 0–30 cm and 0–300 cm layers, respectively, and the highest SOC stocks within 0–300 cm were in Pastoral area. Desert and Gobi area had the lowest SOC stocks in both 0–30 cm and 0–300 cm layers. SOC stocks increased in both 0–30 cm and 0–300 cm layers only in Sanjiangyuan Natural Reserve, while the Desert and Gobi area showed a decrease in both over 30 years. This study emphasizes the significant impact of grassland changes on SOC stocks, indicating the importance of considering these changes in land management and ecological protection policies. The initial and original SOC stocks of pre-LUCC may influence the SOC stocks in post-LUCC. The response of SOC stocks changes to LUCC was varies in different areas. The heterogeneity of different ecological functional areas is affected by multiple factors and SOC stocks will become more complex among these areas in the future. These findings contribute to the development of ecological protection policies and the enhancement of regional land management strategies.

Temporal and vertical dynamics of carbon accumulation potential under grazing-excluded grasslands in China: The role of soil bulk density

Despite the progress made in understanding relevant carbon dynamics under grazing exclusion, previous studies have underestimated the role of soil bulk density (BD), and its implications for potential accumulation of soil organic carbon (SOC), especially at regional scale over long term. In this study, we first constructed a database covering a vast majority of the grasslands in northwestern China based on 131 published literatures. A synthesis was then conducted by analyzing the experimental data to comprehensively investigate the mechanisms of vegetation recovery, carbon-nitrogen coupling, and the importance of changed soil BD in evaluating SOC sequestration potential. The results showed that although the recovery of vegetation height and cover were both critical for improving vegetation biomass, vegetation height required a longer recovery period. While the SOC accumulation was found to be greater in surface layers than deeper ones, it exhibited a reduced capacity for carbon sequestration and an increased risk of SOC loss. Grazing exclusion significantly reduced soil BD across different soil profiles, with the rate of change influenced by soil depth, time, geographical and climatic conditions. The potential for SOC accumulation in the top 30 cm of soil based on data of 2003–2022 was 0.78 Mg ha−1 yr−1 without considering BD effects, which was significantly underestimated compared to that of 1.16 Mg ha−1 yr−1 when BD changes were considered properly. This suggests that the efficiency of grazing exclusion in carbon sequestration and climate mitigation may have been previously underreported. Furthermore, mean annual precipitation represented the most relevant environmental factor that positively correlated to SOC accumulation, and a wetter climate may offer greater potential for carbon accumulation. Overall, this study implies grazing exclusion may play an even more critical role in carbon sequestration and climate change mitigation over long-term than previously recognized, which provides essential scientific evidence for implementing stepwise ecological restoration in grasslands.

Crop yield increments will enhance soil carbon sequestration in coastal arable lands by 2100

Coastal lands are crucial arable land reserves that play a vital role in ensuring future global food security. In arable coastal lands, low soil quality often results in limited crop yield and soil organic carbon (SOC), making them promising sites for enhancing both soil carbon sequestration and agricultural production. However, a scarcity of long-term site experiments has led to a research gap regarding SOC sequestration in coastal arable lands, leaving potential uncertainties due to variations in planting systems, crop yields, and the influence of climate change. In this study, we focused on the Yellow River Delta (YRD) in China, which is a typical coastal agricultural area. We verified the adaptability of the Denitrifcation-Decomposition (DNDC) model in coastal farmlands based on an 11-year long-term observation experiment and continuous sampling survey data. We further explored the spatiotemporal changes of regional SOC stocks under two Shared Socio-Economic Pathways (SSPs) scenarios based on five Global Climate Models (GCMs) derived from the Coupled Model Intercomparison Project Phase 6 (CMIP6), along with three yield increase scenarios from 2020 to 2100. The results indicated that promoting single-cotton cultivation in coastal saline–alkali lands would result in at least 88.2% of farmland being converted into carbon sinks. In contrast, promoting the cultivation of a wheat–maize rotation system can promote regional SOC sequestration as a whole, with a maximum increase of 31.90 Mg C ha−1. By 2100, the SOC stocks decreased in cotton and wheat–maize rotation farmland by 3.9% and 11.6%, respectively, in the SSP585 scenario compared with that in the SSP126 scenario. Except for farmlands with wheat-maize rotation cropping system under the SSP126 scenario, the SOC stocks in all other scenarios are projected to reach their theoretical maximum values before 2050. Additionally, when reaching the North China Plain (S1) and national (S2) high-yield levels of farmland, the SOC stocks in cotton farmland by 2100 increased by 16.7% and 21.6%, respectively, whereas the SOC stocks in wheat-maize farmland increased by 1.8% and 4.8%, respectively. Our study revealed the mutually beneficial relationship between yield increment and SOC sequestration in coastal farmlands under climate change, as well as the potential for future SOC sequestration. We provided scientific support for land management and climate change mitigation strategic decision-making in coastal saline–alkali farmlands.

The response of crop yield, carbon sequestration, and global warming potential to straw and biochar applications: A meta-analysis

Organic materials play an important role in improving crop yield. However, due to variations in natural and field management practices, the impact of straw incorporation (NS) and biochar addition (NB) on soil organic carbon (SOC) sequestration and global warming potential (GWP) remains uncertain. This meta-analysis synthesizes the findings from 112 published studies, encompassing 897 samples, to assess the effects of NS and NB on crop yield, SOC, and GWP. The results reveal that Northeast China has the highest SOC stocks (40.80 Mg ha−1) and annual SOC sequestration (4.27 Mg ha−1 yr−1) compared to other regions. Notably, the NS and NB differ in their effect sizes on improving crop yield (7.68 % and 8.23 %, respectively) and SOC (6.92 % and 30.72 %, respectively), with opposing effects on GWP (increasing by 37.69 % in NS and decreasing by 23.94 % in NB). Following organic material application, climatic conditions, crop and field type, and soil properties affected SOC content and GWP. The main factors influencing variations in crop yield, SOC, and GWP were mean annual temperature and precipitation, initial SOC content, and soil pH, accounting for 57.46 %–60.29 %, 54.75 %–58.52 %, and 61.81 %–65.11 %, respectively. Considering the need to balance food demand, soil fertility and environmental benefits, biochar emerges as a recommended strategy for advancing future agriculture goals. In summary, this study quantitatively assessed the impact of organic material on crop yield, SOC, and greenhouse gas emissions, offering a scientific foundation for optimizing these factors under diverse regional conditions.

Soil carbon sequestration potential of cultivated lands and its controlling factors in China

Understanding soil organic carbon (SOC) stocks and carbon sequestration potential in cultivated lands can have significant benefit for mitigating climate change and emission reduction. However, there is currently a lack of spatially explicit information on this topic in China, and our understanding of the factors that influence both saturated SOC level (SOCS) and soil organic carbon density (SOCD) remains limited. This study predicted SOCS and SOCD of cultivated lands across mainland China based on point SOC measurements, and mapped its spatial distribution using environmental variables as predictors. Based on the differentiation between SOCS and SOCD, the soil organic carbon sequestration potentials (SOCP) of cultivated land were calculated. Boosted regression trees (BRT), random forest (RF), and support vector machine (SVM) were evaluated as prediction models, and the RF model presented the best performance in predicting SOCS and SOCD based on 10-fold cross-validation. A total of 991 topsoil (0–20 cm) SOC measurements and 12 environmental variables explaining topography, climate, organism, soil properties, and human activity were used as predictors in the model. Both SOCS and SOCD suggested higher SOC levels in northeast China and lower levels in central China. The cultivated lands in China had the potential to sequester about 2.13 ± 0.96 kg m−2 (3.25 Pg) SOC in the top 20 cm soil depth. Northeastern China had the largest SOCP followed by Northern China, and Southwestern China had the lowest SOCP. The primary environmental variables that affected the spatial variation of SOCS were mean annual temperature, followed by clay content and normalized difference vegetation index (NDVI). The assessment and mapping of SOCP in China's cultivated lands holds significance importance as it can provide valuable insights to policymakers and researchers about SOCP, and aid in formulating climate change mitigation strategies.

Unleashing the sequestration potential of soil organic carbon under climate and land use change scenarios in Danish agroecosystems

Future global climate changes are expected to increase soil organic carbon (SOC) decomposition. However, the combined effect of C inputs, land use changes, and climate on SOC turnover is still unclear. Exploring this SOC-climate-land use interaction allows us to understand the SOC stabilization mechanisms and examine whether the soil can act as a source or a sink for CO2. The current study estimates the SOC sequestration potential in the topsoil layer of Danish agricultural lands by 2038, considering the effect of land use change and future climate scenarios using the Rothamsted Carbon (RothC) model. Additionally, we quantified the loss vulnerability of existing and projected SOC based on the soil capacity to stabilize OC. We used the quantile random forest model to estimate the initial SOC stock by 2018, and we simulated the SOC sequestration potential with RothC for a business-as-usual (BAU) scenario and a crop rotation change (LUC) scenario under climate change conditions by 2038. We compared the projected SOC stocks with the carbon saturation deficit. The initial SOC stock ranged from 10 to 181 Mg C ha−1 in different parts of the country. The projections showed a SOC loss of 8.1 Mg C ha−1 for the BAU scenario and 6 Mg C ha−1 after the LUC adoption. This SOC loss was strongly influenced by warmer temperatures and clay content. The proposed crop rotation became a mitigation measure against the negative effect of climate change on SOC accumulation, especially in sandy soils with a high livestock density. A high C accumulation in C-saturated soils suggests an increase in non-complexed SOC, which is vulnerable to being lost into the atmosphere as CO2. With these results, we provide information to prioritize areas where different soil management practices can be adopted to enhance SOC sequestration in stable forms and preserve the labile-existing SOC stocks.