Soil organic carbon sequestration potential of conservation agriculture in arid and semi-arid regions: A review

Soil organic carbon sequestration potential and constraints in arid farmland under climate change: Evaluation based on an optimized process-based model.

Minesoils are drastically influenced by anthropogenic activities. They are characterized by low soil organic matter (SOM) content, low fertility, and poor physicochemical and biological properties, limiting their quality, capability, and functions. Reclamation of these soils has potential for resequestering some of the C lost and mitigating CO2 emissions. Soil organic carbon (SOC) sequestration rates in minesoils are high in the first 20 to 30 years after reclamation in the top 15 cm soil depth. In general, higher rates of SOC sequestration are observed for minesoils under pasture and grassland management than under forest land use. Observed rates of SOC sequestration are 0.3 to 1.85 Mg C ha− 1 yr− 1 for pastures and rangelands, and 0.2 to 1.64 Mg C ha− 1 yr− 1 for forest land use. Proper reclamation and postreclamation management may enhance SOC sequestration and add to the economic value of the mined sites. Management practices that may enhance SOC sequestration include increasing vegetative cover by deep-rooted perennial vegetation and afforestation, improving soil fertility, and alleviation of physical, chemical and biological limitations by fertilizers and soil amendments such as biosolids, manure, coal combustion by-products, and mulches. Soil and water conservation are important to SOC sequestration. The potential of SOC sequestration in minesoils of the US is estimated to be 1.28 Tg C yr−1, compared to the emissions from coal combustion of 506 Tg C yr− 1.

The present research was aimed to estimate the spatial variability of soil organic carbon and their sequestration potential in the part of Bishwanaath, Chariali district of Assam. The sample was collected from marked sample points representing variability of soil type and crops grown. The collected samples were analysed for Soil Organic Carbon (SOC) and further SOC sequestration potential was derived based on this analysed SOC and CSP interpolation method deriving data in unsampled point. Geostatistical method viz., ordinary Kriging was employed for the detailed spatial distribution of SOC, CSP and interpolation map of SOC and CSP were generated. From the generated map it was revealed that SOC was lowest at the western part of study sites whereas the CSP is lowest at two spot where intensive cultivation of rice were practised since long time resulting comparatively less SOC build-up in the soil system. The remaining part of domain district were of medium to higher CSP potential. This difference in spatial variability in SOC and CSP might be due to the variation in soil physical properties specially bulk density of the respective soil sites. The Nugget to Sill ratio was quite high in CSP that indicating the management factor plays a very important role in soil carbon sequestration potential.

Soil organic carbon sequestration in temperate agroforestry systems – A meta-analysis

Some general notions on soil organic carbon (SOC) sequestration and the difficulties to evaluate this process globally are presented. Problems of time- and space- scales are emphasized. SOC erosion, which is generally difficult to evaluate in relation to land use changes, is discussed in detail. Different aspects of SOC sequestration on the Lesser Antilles are presented for a wide range of soil types. Comparisons between soils revealed that the SOC stocks in the Lesser Antilles are highly dependent upon the mineralogy: higher stocks for allophanic (ALL) soils than for low activity clay (LAC) and high activity clay (HAC) soils. But in terms of potential of SOC sequestration (pSeq-SOC, differences between permanent vegetation and continuous cultivation situations), there are no differences between ALL and LAC soils (22.9 and 23.3 tC. ha−1, respectively). On the other hand, the potentials of SOC sequestration were higher for HAC soils (30.8 – 59.4 tC. ha−1, with the higher levels in the less Mg- and Na-affected Vertisol). Sheet erosion is a serious problem for Vertisol with high Mg and Na on exchange complex, causing high dispersability of fine elements. Thus, the lower SOC levels in these soils may be partly due to erosion losses. Laboratory incubations have shown that 37 – 53% of the protected SOC in these soils was located in aggregates larger than 0.2 mm. The effect of agricultural practices on SOC sequestration was studied for the Vertisols. Intensification of pastures led to higher plant productivity and higher organic matter restitutions and SOC sequestration. The gain was 53.5 and 25.4 tC. ha−1 for the low and high-Mg Vertisol, respectively (0–20 cm layer). SOC sequestration with pastures also depends upon the plot history with lower mean annual increase in SOC for the initially eroded (1.0 gC . kg−1 soil . yr−1) than for the non-degraded (1.5 gC . kg−1 soil . yr−1) Vertisol. Loss of SOC in a pasture-market gardening rotation was 22.2 tC . ha−1 with deep (30–40 cm) and 10.7 tC . ha−1 with surface (10–15 cm) tillage. It was unclear whether the differences in SOC losses were due to mineralization and/or to erosion.

Measuring and modeling soil carbon sequestration under diverse cropping systems in the semiarid prairies of western Canada

Fertilization is a feasible approach to increase the soil organic carbon. To investigate the effect of fertilization on crop biomass carbon, dynamics of soil organic carbon and soil carbon sequestration rate in the (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system under the middle reach of the Yangtze River, central China, a thirty-three years (1981 − 2013) long-term fertilizer experiment was conducted with nine treatments, including no amendment addition treatment (control), nitrogen (N), phosphorus (P), potassium (K) fertilizer treatments (N, NP, NPK), manure (M) and manure combined with chemical fertilizer treatments (MN, MNP, MNPK, hMNPK). The results indicated that average crop biomass carbon was increased by 39.9 − 77.2% compared to unfertilized control (4.43 t ha−1 yr−1) due to fertilizer application, the highest crop biomass carbon was 7.85 t ha−1 yr−1 in the hMNPK treatment and the lowest crop biomass carbon was 5.21 t ha−1 yr−1 in the N alone treatment. The annual total organic carbon input were 4.14 t ha−1 yr−1 in the M treatment and 5.80 t ha−1 yr−1 in the hMNPK treatment, which was 1.95 − 2.74 times of those in the NPK treatments (2.12 t ha−1 yr−1). Total organic carbon input of soil were increased by 10.2 − 23.3 kg C ha−1 yr−1, and increment rate in the appended manure treatments were much higher than those in the control and inorganic fertilizer treatments. Soil organic carbon retention in the topsoil (0 − 20 cm) decreased by 0.11 − 0.14 t ha−1 yr−1 in the control, N and NP treatments; nevertheless, soil organic carbon sequestration rates varied from 0.03 to 0.20 t ha−1 yr−1 in the NPK and appended organic manure treatments. These results demonstrate that organic manure use or integrated organic manure with chemical fertilizer application can be important strategies for increasing soil organic carbon sequestration and maintaining soil quality in the rice-wheat cropping system of China.

Interactive impacts of climate change and agricultural management on soil organic carbon sequestration potential of cropland in China over the coming decades

PurposeTackling the global carbon deficit through soil organic carbon (SOC) sequestration in agricultural systems has been a focal point in recent years. However, we still lack a comprehensive understanding of actual on-farm SOC sequestration potentials in order to derive effective strategies.MethodsTherefore, we chose 21 study sites in North-Eastern Austria covering a wide range of relevant arable soil types and determined SOC pool sizes (0–35 cm soil depth) in pioneer versus conventional management systems in relation to permanently covered reference soils. We evaluated physico-chemical predictors of SOC stocks and SOC quality differences between systems using Fourier-transform infrared (FTIR) spectroscopy.ResultsCompared to conventional farming systems, SOC stocks were 14.3 Mg ha− 1 or 15.7% higher in pioneer farming systems, equaling a SOC sequestration rate of 0.56 Mg ha− 1 yr− 1. Reference soils however showed approximately 30 and 50% higher SOC stocks than pioneer and conventional farming systems, respectively. Nitrogen and dissolved organic carbon stocks showed similar patterns. While pioneer systems could close the SOC storage deficit in coarse-textured soils, SOC stocks in medium- and fine-textured soils were still 30–40% lower compared to the reference soils. SOC quality, as inferred by FTIR spectra, differed between land-use systems, yet to a lesser extent between cropping systems.ConclusionsInnovative pioneer management alleviates SOC storage. Actual realized on-farm storage potentials are rather similar to estimated SOC sequestration potentials derived from field experiments and models. The SOC sequestration potential is governed by soil physico-chemical parameters. More on-farm approaches are necessary to evaluate close-to-reality SOC sequestration potentials in pioneer agroecosystems.

Soil organic carbon (SOC) sequestration in cropland is not only instrumental in combating climate change, but it also significantly enhances soil fertility. It is imperative to precisely and accurately quantify the SOC sequestration potential and assess the relative significance of various multiple explanatory factors in a timely manner. We studied 555 soil samples from the cropland topsoil (0–15 cm) across the black soil region in Northeast China between the years 2021 and 2022, and we identified 16 significant impact factors using one-way ANOVA and Pearson correlation coefficient analysis. In addition, the Random Forest (RF) model outperformed the Cubist model in predicting the spatial distribution of SOC contents. The predicted ranges of SOC contents span from 5.24 to 43.93 g/kg, with the average SOC content using the RF model standing at 17.24 g/kg in Northeast China. Stepwise regression and structural equation modeling revealed climate and topography as key factors affecting SOC distribution. The SOC density in the study area varied from 0.51 to 9.11 kg/m2, averaging 3.30 kg/m2, with a total SOC stock of 1226.64 Tg. The SOC sequestration potential in the study area was estimated at 3057.65 Tg by the categorical maximum method, with a remaining sequestration capacity of 1831.01 Tg. The study area has great potential for SOC sequestration. We hope to transform the theoretical value of SOC sequestration potential into actual SOC sequestration capacity by promoting sustainable agriculture and additional strategies. Our findings provide insights into the global soil conditions, SOC storage capacities, and effective SOC management strategies.

Abstract:Revegetation is vital for enhancing soil carbon sequestration. However, the impacts of revegetation and terracing measures on soil organic carbon (SOC) and SOC sequestration (SOCS), and the differences in the effects of revegetation on SOC and SOCS when implemented on sloped fields versus terraced fields, are still unclear. Thus, we conducted a field survey on cropland (CL), grassland (GL), and forestland (FL) on both sloped fields and terraced fields in Wuqi county, China’s Loess Plateau. The results showed that SOC content in FL at 0–10 cm, 10–20 cm, 20–40 cm, 40–60 cm depths were 1.70, 1.28, 1.28, and 1.19 times respectively higher than in CL. Similarly, SOC content in GL at the same depths were 1.30, 1.13, 1.18, and 1.20 times higher than in CL. In terraced, SOC content at 40–60 cm, 60–80 cm, 80–100 cm depths were 1.22, 1.28, and 1.20 times respectively higher than on sloped fields. Revegetation primarily significantly affected SOC at 0–10 cm depth on sloped fields (GL: p = 0.04; FL: p < 0.01), and more deeply (0–100 cm) on terraced fields (GL at 40–80 cm: p < 0.05; FL: p < 0.01). Furthermore, revegetation on sloped fields generated the highest SOCS at 0–40 cm depth, with a subsequent decrease as depth increased to 40–100 cm depth. Conversely, on terraced, SOCS increased with soil depth within the 0–100 cm depth. These results indicated that revegetation primarily enhanced SOCS in the surface soil (0–40 cm), and terracing measures stabilized the SOCS in the surface soil and further enhanced them in deeper soil horizons (0–100 cm). Therefore, in the context of soil erosion control and ecological restoration, the combined implementation of vegetation restoration and engineering measures can effectively stabilize and enhance SOCS, thereby fully leveraging the role of soil in mitigation climate change.Keywords: Soil and water conservation measures; Carbon sequestration; Land use change；Vegetation restoration; Engineering measures; Deep soil organic carbon

Although conservation agriculture practices evidently facilitate the build-up of soil organic carbon (SOC), the sequestration potential of arable soils is strongly mediated by edaphic attributes; so far, their interplay is not well understood. Deciphering these drivers is however important to correctly estimate SOC storage potentials in arable soils and to derive effective strategies for the implementation of successful measures. By using an on-farm approach, we conducted a pairwise comparison of 21 conventional and highly innovative ‘pioneer’ farms across a wide range of arable soil types and evaluated the leverage of site attributes and management practices such as crop diversity, reduced tillage, organic fertilization, cover cropping and inter cropping on the SOC sequestration potential.While most pioneer management practices proved beneficial for the sequestration of SOC – particularly cover cropping and crop diversity – our results clearly show that soil texture was the most significant shaping factor. Coarse-textured soils had a significantly higher potential for SOC accrual compared to medium- and fine-textured soils. The initial SOC content also had a significant effect on prevalent sequestration potentials. Based on the fact of a clear predominance of natural site conditions over management impacts in enhancing SOC storage of arable soils, we call for a critical discussion of carbon farming schemes. As similar efforts and costs of implementing carbon farming measures will have distinctive carbon gains, dependent on environmental constraints beyond farmers’ influence, we advocate for strategies harmonizing both activity- and results-based approaches to maximize the ecological effectiveness and the spatial dissemination of soil health innovations. Carbon farming schemes thus need reconsideration within the state-of-the-art scientific framework of carbon saturation behaviour in order to properly account for biophysical constraints when formulating soil-related climate change mitigation policies.

Soil organic carbon fractions and sequestration across a 150-yr secondary forest chronosequence on the Loess Plateau, China

Grasslands occupy almost half of the world's land area. Soil organic carbon (SOC) is a key indicator of soil fertility and grassland productivity. Increasing SOC stocks (so‐called SOC sequestration) improves soil fertility and contributes to climate change mitigation by binding atmospheric carbon dioxide (CO2). Grasslands constitute about 70% of all agricultural land, but their potential for SOC sequestration is largely unknown. This review paper quantitatively summarizes observation‐based studies on the SOC sequestration potential of grasslands in six East African countries (Burundi, Ethiopia, Kenya, Rwanda, Tanzania and Uganda) and seeks to identify knowledge gaps related to SOC sequestration potential in the region. In the studies reviewed, SOC stocks in grasslands range from 3 to 93 Mg C/ha in the upper 0.3 m of the soil profile, while SOC sequestration rate ranges from 0.1 to 3.1 Mg C ha‐1 year‐1 under different management strategies. Grazing management is reported to have a considerable impact on SOC sequestration rates, and grassland regeneration and protection are recommended as options to stimulate SOC sequestration. However, a very limited number of relevant studies are available (n = 23) and there is a need for fundamental information on SOC sequestration potential in the region. The effectiveness of potential incentive mechanisms, such as payments for environmental services, to foster uptake of SOC‐enhancing practices should also be assessed.

Upscaling the results from process-based soil-plant models to assess regional soil organic carbon (SOC) change and sequestration potential is a great challenge due to the lack of detailed spatial information, particularly soil properties. Meta-modeling can be used to simplify and summarize process-based models and significantly reduce the demand for input data and thus could be easily applied on regional scales. We used the pre-validated Agricultural Production Systems sIMulator (APSIM) to simulate the impact of climate, soil, and management on SOC at 613 reference sites across Australia's cereal-growing regions under a continuous wheat system. We then developed a simple meta-model to link the APSIM-modeled SOC change to primary drivers, i.e., the amount of recalcitrant SOC, plant available water capacity of soil, soil pH, and solar radiation, temperature, and rainfall in the growing season. Based on high-resolution soil texture data and 8165 climate data points across the study area, we used the meta-model to assess SOC sequestration potential and the uncertainty associated with the variability of soil characteristics. The meta-model explained 74% of the variation of final SOC content as simulated by APSIM. Applying the meta-model to Australia's cereal-growing regions reveals regional patterns in SOC, with higher SOC stock in cool, wet regions. Overall, the potential SOC stock ranged from 21.14 to 152.71 Mg/ha with a mean of 52.18 Mg/ha. Variation of soil properties induced uncertainty ranging from 12% to 117% with higher uncertainty in warm, wet regions. In general, soils in Australia's cereal-growing regions under continuous wheat production were simulated as a sink of atmospheric carbon dioxide with a mean sequestration potential of 8.17 Mg/ha.