Soil Carbon Dynamics and Greenhouse Gas Reduction Potential of Arundo donax-Based Sustainable Aviation Fuel in China’s Bohai Rim Region

Simulating the effects of erosion on organic carbon dynamics in agricultural soils

<p>Soil erosion in croplands has a strong impact on global carbon (C) cycle. Assessment of erosional effects on soil organic carbon (SOC) dynamics in agricultural soils suffers from the difficulty of distinguishing the erosional effects and complex interaction processes between erosion and C cycling. To simulate the effects of soil erosion, a plots experiment including six erosion levels (0, 5, 10, 20, 30, and 40 cm eroded) was conducted for seven years (2012-2018). The erosion levels were simulated using artificial soil profiles created by mixing soils from different layers in the original soil profile (never eroded) in a certain proportion. Subsequently, based on the field observations during 2012-2018, the SOC dynamics of each experimental plot were simulated by using a process-oriented C cycle model (denitrification-decomposition (DNDC)) to quantify the effects of erosion on SOC dynamics. The measurements at the beginning of the plots experiment showed that simulated erosion resulted in the depletion of SOC with an average reduction rate of 9.7% per 10 cm of soil loss; SOC in eroded soils recovered after seven years of cropping, the declining slope of the SOC measured in 2018 was 3.0% per 10 cm of soil loss, suggesting that dynamic replacement had occurred. Model simulation results indicated that soil erosion could reduce the C inputs from crop residue by lowering soil productivity; soil heterotrophic respiration in eroded soils was restricted due to the lower initial SOC content. As a result, the simulated overall SOC stock in eroded soils was restored after erosion stopped because of the lower C output. These results indicated that SOC loss at eroding sites was caused mainly by lateral transport rather than enhanced decomposition. The fate of the displaced SOC within catchments is key to assess the net impacts of soil erosion on SOC dynamics at a large scale.</p>

Carbon Sequestration in Soils of Latin America

Trade-off between soil organic carbon sequestration and plant nutrient uptake in arbuscular mycorrhizal symbiosis

<p>Soil carbon sequestration (SCS) has been identified by the IPCC as one of the most promising and cheap methodology to reduce atmospheric CO<sub>2</sub>. Moreover, an increase in soil organic carbon (SOC) levels improves soil quality by increasing soil structure (and, hence, resistance to erosion) and promoting soil ecosystems services like water retention, productivity, and biodiversity. Various agricultural techniques are available to increase SOC; among them, crop rotation can improve SOC through soil coverage, changes in water regimes, increase in both carbon inputs, and increase in soil aggregates formation.</p><p>SOC dynamic models, such as RothC, have been suggested by the IPCC as a way to evaluate the SCS potentials of different soils. Such models could also be used to evaluate the sequestration potential of different agricultural practices. Moreover RothC allows to estimate the time within which the SOC variation, due to a certain agronomic management, can be considered significant as measurable above a threshold value.</p><p>In this study, we evaluated the SOC changes for different crop rotations through direct measurements and RothC modelling, with the objective of: (a) estimating their SCS potential, and (b) propose a robust monitoring methodology for SCS practices. We performed the study in an agricultural field close to Ravenna (Italy) characterized by Cambisols and humid subtropical climate. Soil carbon content was assessed before the setup of the crop rotation, and after 3 years of rotation. A RothC model was calibrated with field data, and used to estimate SOC dynamics to 50 years, in order to assess long-term SCS. The model results were also used to assess the best methodology to estimate the SOC variation significance.</p><p>The measured SOC was similar to the equilibrium SOC predicted by the RothC model, on average, for the crop rotations. The measurements showed that the SOC, already low at the beginning of the experiment, further decreased due to the crop rotation practice. Of those tested, the best for SCS involves the following crops: corn, soybeans, wheat on tilled soil, and soybeans; while the worst is with corn, wheat on tilled soil, and wheat on untilled soil. However, the SOC variations predicted by RothC for the various rotations were too small to be observable in the field during experimentation. This could be due both to the uncertainty associated with SOC sampling and analysis, and to the short duration of the experiment. The moving average computations on the simulation values allowed us to assess the time required to measure the long-term trend of SOC variation as significant with respect to the environmental background, instrumental error, and SOC periodic fluctuations. That time was estimated to range from 8 to 50 years, changing depending on the rotation type. Periodic fluctuations in SOC should be carefully considered in a monitoring protocol to assess SCS.</p>

Sustainable aviation fuels (SAF) produced from lipid feedstocks are an increasingly mature and low-cost option for aviation sector decarbonization. Ethiopian mustard (Brassica carinata) is a non-food oilseed crop that can be grown on winter fallow land in the southeastern US and used as a feedstock for SAF, with a high-protein livestock feed co-product. Integrating carinata into existing annual crop rotations produces an additional revenue stream for landowners, with potential co-benefits for soil carbon and other ecosystem services. The Southeast Partnership for Advanced Renewables from Carinata (SPARC) is a USDA-funded research consortium to advance carinata production and associated SAF and bioproduct supply chains in the region. A SPARC research team used the DayCent ecosystem model to estimate the potential production of carinata across the tri-state region of Alabama, Florida, and Georgia, and assess associated changes in soil carbon storage and emissions of nitrous oxide (N2O), the main biogenic greenhouse gas (GHG) emissions from agriculture. First, we calibrated DayCent to reproduce the phenology, harvest index, productivity response to nitrogen application, root-to-shoot biomass ratio, and tissue nitrogen content data observed for a set of carinata field trials in the region. Next, we simulated the integration of carinata into a typical cotton/peanut rotation across the 2.3 million hectares of annual cropland within the climate suitability range for this crop, grown once every third winter. We show an annual production potential of greater than 1 billion liters of SAF from this feedstock in the region. Our base carinata management case is approximately neutral in biogenic GHG emissions, with modest soil carbon sequestration that offsets the associated small increase in N2O emissions. However, adopting conservation management practices such as no-till establishment or poultry litter soil amendments results in a more substantial net soil carbon sink, reducing the GHG footprint of carinata-derived SAF by up to 20 grams of CO2-equivalent per megajoule of fuel. This work supports SPARC’s ongoing efforts to develop improved crop varieties and management practices that simultaneously improve the economics and ecosystem service value of carinata production.

Management practices can have significant implications for both soil quality and carbon (C) sequestration potential in agricultural soils. Data from two long‐term trials (one at field scale and the other at lysimeter scale), underway in north‐eastern Italy, were used to evaluate the dynamics of soil organic carbon (SOC) and estimate the impact of recommended management practices (RMPs) on soil carbon sequestration. Potential SOC sequestration was calculated as the differences between the change in SOC of treatments differing only for the specified RMP for a period of at least 25 years. The trials compared the following situations: (a) improved crop rotations versus monoculture; (b) grass versus improved crop rotations; (c) residue incorporation versus residue removal; (d) high versus low rates of inorganic fertilizers; (e) integrated nutrient management/organic manures versus inorganic fertilizers. At the lysimeter scale, some of these treatments were evaluated in different soils. A general decrease in SOC (1.1 t C ha −1 year −1 ) was observed after the introduction of intensive soil tillage, evidencing both the worsening of soil quality and the contribution towards global CO 2 emissions. Initial SOC content was maintained only in permanent grassland, complex rotations and/or with the use of large quantities of livestock manure. SOC sequestration reached a maximum rate of 0.4 t C ha −1 year −1 comparing permanent grassland with an improved crop rotation. Crop residue incorporation and rates of inorganic fertilizer had less effect on SOC sequestration (0.10 and 0.038 t C ha −1 year −1 , respectively). The lysimeter experiment highlighted also the interaction between RMPs and soil type. Peaty soil tended to be a source of C independent of the amount and quality of C input, whereas a proper choice of tillage practices and organic manures enhanced SOC sequestration in a sandy soil. The most promising RMPs in the Veneto region are, therefore, conversion to grassland and use of organic manures. Although some of these RMPs are already supported by the Veneto Region Rural Development Plan, their more intensive and widespread implementation requires additional incentives to become economically feasible.

Hierarchical responses of soil organic and inorganic carbon dynamics to soil acidification in a dryland agroecosystem, China

Soil carbon efflux and sequestration as a function of relative availability of inorganic N pools in dry tropical agroecosystem

Climate change may significantly impact crop yields and soil. In this study the DNDC model, together with climatic outputs from Hadley Centre’s general circulation model (HadCM3), was used to investigate the influence of projected climate change and management practices on soil organic carbon (SOC) dynamics and crop yield of the Chinese Loess Plateau. The results identify management practices with the greatest potential to mitigate climate change and to increase SOC in this area. Field experiments on winter-wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation included a control and four types of fertilization treatments: T1 (control), T2 (inorganic fertilizer), T3 (NPK inorganic fertilization combined with wheat or maize residue return), T4 (NPK inorganic fertilization combined with low amount of manure) and T5 (NPK inorganic fertilization combined with high amount of manure). DNDC model was calibrated using the field data from 1991 to 2000 and validated from 2001 to 2010. Furthermore, a baseline climate and three future climate scenarios (A1B, A2 and B1) were considered. DNDC model effectively simulated the SOC and crop yields. The findings showed that in 1991–2010, T1 maintained its initial SOC level but reduced crop yields, while T2 promoted crop production with less effect on soil carbon storage. However, T3, T4 and T5 enhanced both crop yield and soil carbon, and the best results were observed under T5. The investigated climate scenarios substantially affect SOC content and crop yields. In terms of SOC content, B1 had great effects on T1, T4 and T5, while A1B on T2 and T3. Considering crop yields, in all treatments, the trends are B1 > A1B > A2 for winter-wheat and A2 > A1B > B1 for summer maize, respectively. The impacts of climate changes on SOC dynamics and crop yields were different depending on the management applied. Thus, the adoption of certain management practices in the Chinese Loess Plateau agroecosystems could be critical in maximizing SOC sequestration and reducing CO2 in the atmosphere. Reasonably low temperature and high precipitation can enhance winter-wheat yields, while maize yields need medium temperature and precipitation. We recommended the combined application of inorganic and organic fertilizers to achieve a balance between food security and soil carbon sequestration objectives.

Soil aggregation and structural stability play a crucial role in soil organic carbon (SOC) sequestration. However, the underlying mechanisms of arbuscular mycorrhizal fungi (AMF) and glomalin‐related soil protein (GRSP) responses to N addition and their impacts on soil aggregation and organic carbon stability remain unclear. Hence, a 16‐year field N addition experiment on winter wheat (Triticum aestivumL.) was conducted to investigate the effects on the stability of soil structure and SOC fractions via AMF and GRSP. Overall, N addition increased the soil aggregate mean weight diameter (MWD), which exhibited an increase in the proportion of large macroaggregates and a decrease in the proportion of silt‐clay fractions. Appropriate N (180 kg N ha−1) input increased SOC stability and total SOC stock, while excessive N (360 kg N ha−1) input increased labile organic carbon fractions, and active C index and decreased the C stock. The concentrations of SOC, total GRSP (T‐GRSP), and easily extractable GRSP (EE‐GRSP) showed the largest increases in small macroaggregates, and GRSP was significantly correlated with SOC, recalcitrant organic carbon, and MWD (p < 0.05). These results indicated that appropriate N addition promoted AMF to secrete GRSP, which in turn favoured large macroaggregation and enhanced the physical protection of SOC. Meanwhile, the increased GRSP stimulated the accumulation of recalcitrant C, thus improving soil organic carbon stability and carbon sequestration capacity. The study suggested that appropriate N addition (180 kg N ha−1) should be used to improve the carbon sequestration potential of farmland on the Loess Plateau.

This study investigated Soil Organic Carbon (SOC) pools and Soil Microbial Biomass Carbon (SMBC) across three forest types in Mizoram, India: Secondary Moist Bamboo Brakes (SMBB), East Himalayan Moist Mixed Deciduous Forest (EHMMDF), and Cachar Tropical Semi-Evergreen Forest (CTSEF). SOC is crucial for global biogeochemical cycles, influencing nutrient availability and ecosystem resilience. The study highlights the impact of forest type on SOC dynamics and microbial activity. The SMBB exhibited an Active Pool (Very Labile Carbon [VLC] + Labile Carbon [LC]) of 1.21% and a Passive Pool (Less Labile Carbon [LLC] + Non-Labile Carbon [NLC]) of 0.78%, resulting in overall TOC of 1.99%, of which SOC (Walkley–Black C) was 1.58% and SMBC of 340.72 mg/kg, indicating a balanced microbial presence. The EHMMDF had relatively higher SOC (2.49%) and SMBC (352.31 mg/kg), suggesting increased microbial activity and faster carbon turnover. The CTSEF recorded the highest SOC (2.51%) and significant SMBC (348.73 mg/kg), with the highest VLC at 1.06%. Additionally, Dehydrogenase Activity (DHA), a key indicator of microbial metabolic activity, was highest in the EHMMDF (6.42 µg TPF/g/h) and lowest in the SMBB (5.62 µg TPF/g/h). Correlations between SMBC and SOC pools were weak, with VLC and LC showing significant positive relationships with Total Organic Carbon (TOC) (r = 0.636 and 0.693). These findings underscore the importance of forest type in shaping SOC and microbial dynamics, with implications for sustainable land management and carbon sequestration strategies in tropical forests.

Dynamics of soil carbon and nitrogen stocks after afforestation in arid and semi-arid regions: A meta-analysis

<p>The role of soil organic carbon (SOC) in avoidance, mitigation and control land degradation in forest ecosystems is largely recognized. For these reasons, a satisfactory SOC monitoring aimed to drive sustainable SOC management is necessary to avoid soil forest degradation. In this work we thus aimed to a) compare the soil organic carbon stock (OC stock) obtained by pedogentic horizons (PED) and fixed depth layer (FIX) in different forest ecosystems; b) discuss the differences in SOC data provided by the two soil sampling approaches, clarifying their major advantages and drawbacks; and c) to assess the ability of PED and FIX sampling approaches to keep information about horizontal and vertical SOC distribution. On the Apennine chain (North Italy), uneven–aged sweet chestnut, European beech and Norway spruce forests were selected. In each site, a representative area (18 m × 18 m) has been selected and, in the centre of the area, a soil profile has been investigated. Further, within the representative areas 8 additional sampling points were identified. Both for soil profiles and the additional sampling points, soil collection was performed both by PED and FIX (0–15 and 15–30 cm). For each forest stand, no difference of OC stock in 0–30 cm soil depth was found between PED and FIX sampling approaches, however SOC distribution along 0-30 cm provided by PED sampling was more informative on SOC dynamics. The findings obtained through the sampling by FIX would indicate a positive effect of conifers on SOC storage, the PED sampling allowed to assess that SOC under spruce forest was greatly stored in the organic horizons (Oe and Oa) because of the recalcitrant nature of the spruce litter, that does not allow the organic carbon stabilization through the association with mineral particles. Therefore, the spruce forest soil would not lead structural stability and resilience to soil degradation. Sampling by PED also preserved the information about the spatial variability within each study site. In fact, we noted higher coefficient of variation when soil horizons were considered compared to FIX (from 19.2 to 72.8% and from 16.5 to 25.7%, respectively). Overall, in a view of SOC monitoring, our findings demonstrated that the sampling by PED draws a better picture of SOC distribution along depth and its potential susceptibility to external factors leading to degradation. Further, the loss of information about SOC stabilization process and spatial variability would indicate the inability of FIX sampling to support decision–making plans addressed for sustainable use of soil resource.</p>

Soil organic carbon (SOC) sequestration in agricultural soils is one of major agricultural strategies to mitigate the greenhouse gas (GHG) emissions as it is a potential sink for atmosphere carbon. Cropping systems and management practices adopted will affect the SOC sequestration. Dynamics of SOC is very important for understanding the pathways of C stabilization into different SOC pools. An attempt was made to assess the importance of different cropping systems on C sequestration and its stabilization in a 9 year old experiment at PJTSAU, Hyderabad, India. In comparison to initial TOC, cropping system perennial super napier fodder showed greater C build up (46.5%) followed by maize intercropped with pigeonpea followed by sunhemp (23.1%). In fact, all the cropping systems there were net increases in TOC. There was only 6.86% of C applied through various sources was stabilized as SOC. A minimal input of 1.24 Mg C ha-1 yr-1 is needed to maintain SOC level. Cropping system perennial super napier fodder showed a higher carbon management index (145.9), sustainable yield index (64.1), BC ratio (16.99) and least amount is required to sequester the kg of carbon to soil (Rs. 59).