Carbon Sequestration In Agricultural Soils Research Articles

Comparative analysis of biochar production methods and their impacts on biochar physico-chemical properties and adsorption of heavy metals

Rapid industrialization, urbanization, and population growth result in vast amounts of organic waste being produced, including agricultural waste, animal waste, industrial waste, sewage sludge, and municipal solid waste. Biochar production from solid waste has become a popular waste management method. However, in rural areas of developing nations, biomass is typically used for cooking without being charred. Urban biowaste-derived biochar may enhance soil fertility and overall soil health. However, large-scale biochar production from an electronic muffle furnace could be very expensive, and there is little information on the conversion of biowastes to biochar using traditional kilns or its effects on biochar characteristics, and farmers' biochar production methods are yet underdeveloped. Hence, this study provides biochar production from biowastes using two production methods: 1) a traditional kiln (a tin kiln) intended for use by small farmers and gardeners, and 2) a laboratory muffle furnace, with the aim of evaluating biochar characteristics. Biochar produced in a muffle furnace and tin kiln has found similar physicochemical and adsorption properties at the same pyrolysis conditions. They include high pH, EC, CEC, Pava, Ca, Mg, K, and carbon content. We expect these biochars to have larger long-term effects on agricultural characteristics and soil carbon sequestration. However, the present results might be utilized to drive cleaner biochar production for agricultural use in developing nations, which may multiply local producer benefits.

Study on the Effects of Reducing Nitrogen Fertilizer: Stabilizing Yield and Carbon Sequestration by Synergistic Utilization of Chinese Milk Vetch and Rice Straw in Double-Cropping Rice Area

The excessive application of chemical fertilizers in rice fields exacerbates soil degradation and poses a threat to food security. Achieving an increase in rice production and minimizing environmental costs are inevitable requirements for achieving sustainable rice production. The synergistic utilization of rice straw (RS) and Chinese milk vetch (MV) is a sustainable measure to improve soil quality in Southern China. How this management strategy impacts agricultural productivity and soil carbon (C) sequestration under different fertilization conditions is unclear. Several treatments, including only chemical fertilizer (F), F + MV (FM), F + RS (FS), and F + MV + RS (FMS) under a standard rate of nitrogen (N100) and 40% reduced nitrogen (N60) levels were designed to explore changes in rice yields and soil organic carbon (SOC) concentrations, stocks, and soil labile organic C fractions (permanganate oxidizable C) during 2018–2020 in a double-rice-cropping system. The results show that the FMS treatment reduced soil bulk density to alleviate soil compaction and improved the soil carbon management index. The synergistic utilization of MV and RS replacing 40% of the chemical N fertilizer could still maintain the rice yield. Compared to the F treatment, the average annual grain yield was significantly increased by 9.82% and 5.84% in the FMS treatment; SOC concentration was increased by 16.05% and 19.98% on average (p < 0.05), and SOC stock was increased by 1.78 Mg C ha−1 and 2.37 Mg C ha−1 under the N60 and N100 levels, respectively. The random forest regression model and correlation analysis demonstrated that the inputs of chemical N, organic N and C, and appropriate C/N ratio promoted soil C accumulation. Furthermore, the structural equation model analysis exhibited that the C input affects the highly labile organic carbon (HLOC) and total labile organic carbon (LOC); the HLOC had a positive effect on SOC (p < 0.05). N input had a significant effect on LOC and yield. Our results suggest that the synergistic utilization of MV and RS plays an important role in ensuring stable grain production, improving soil C sequestration capacity, and maintaining soil environmental health in Southern China.

Microbial regulation of aggregate stability and carbon sequestration under long-term conservation tillage and nitrogen application

The stability of aggregates plays a significant role in soil organic carbon (SOC) sequestration in conservation agriculture soils. However, the regulation of microorganisms within aggregates on aggregate stability and SOC sequestration remains elusive. By dividing the soil into three aggregate size classes [mega-aggregates (>2000 μm), macro-aggregates (250–2000 μm), and micro-aggregates (<250 μm)], we evaluated the response of aggregate stability, SOC and microbial communities within aggregates to long-term conservation tillage, which consisted of two tillage methods (conventional tillage and no-tillage) and three nitrogen application rates (105, 180, and 210 kg N ha−1). Under no-tillage treatment, high nitrogen application rate increased SOC by 2.1–3.7 g·kg−1 within mega- and macro-aggregates but reduced the total amount of phospholipid fatty acids (PLFAs) within all aggregates. Under conventional tillage, high N application rate increased mean weight diameter (MWD) and reduced total PLFAs within all aggregates only in 0–10 cm. With the same nitrogen application rate, no-tillage increased MWD by 8.7 %–42.7 %, SOC content within mega-aggregates by 7.3 %–27.8 % and within macro-aggregates by 13.2 %–28.3 % when compared with conventional tillage. Actinobacteria were recruited by straw under no-tillage and their biomass increased 1.5–7.8 times in all aggregates compared with conventional tillage, where they might participate in aggregate formation via degradation of straw and increasing SOC within mega- and macro-aggregates. Conversely, desulfovibrio biomass within all aggregates was diminished under no-tillage compared with conventional tillage, while desulfovibrio possibly directly inhibited soil aggregate formation and decreased SOC within mega- and macro-aggregates under conventional tillage. Moreover, under no-tillage, arbuscular mycorrhizal fungi biomass increased by 0.4–1.6 nmol g−1 within all aggregates compared with conventional tillage in 0–10 cm, potentially indirectly contributing to soil aggregate formation via co-metabolic processes and increasing SOC within mega- and macro-aggregates. Overall, high nitrogen application under long-term no-tillage protects SOC within mega-aggregates by altering aggregate formation through the microbial communities, providing information that may be useful in developing management strategies to enhance carbon sequestration in agricultural soils.

Impact of residual antibiotics on microbial decomposition of livestock manures in Eutric Regosol: Implications for sustainable nutrient recycling and soil carbon sequestration

The land application of livestock manure has been widely acknowledged as a beneficial approach for nutrient recycling and environmental protection. However, the impact of residual antibiotics, a common contaminant of manure, on the degradation of organic compounds and nutrient release in Eutric Regosol is not well understood. Here, we studied, how oxytetracycline (OTC) and ciprofloxacin (CIP) affect the decomposition, microbial community structure, extracellular enzyme activities and nutrient release from cattle and pig manure using litterbag incubation experiments. Results showed that OTC and CIP greatly inhibited livestock manure decomposition, causing a decreased rate of carbon (28%–87%), nitrogen (15%–44%) and phosphorus (26%–43%) release. The relative abundance of gram-negative (G-) bacteria was reduced by 4.0%–13% while fungi increased by 7.0%–71% during a 28-day incubation period. Co-occurrence network analysis showed that antibiotic exposure disrupted microbial interactions, particularly among G- bacteria, G+ bacteria, and actinomycetes. These changes in microbial community structure and function resulted in decreased activity of urease, β-1,4-N-acetyl-glucosaminidase, alkaline protease, chitinase, and catalase, causing reduced decomposition and nutrient release in cattle and pig manures. These findings advance our understanding of decomposition and nutrient recycling from manure-contaminated antibiotics, which will help facilitate sustainable agricultural production and soil carbon sequestration.

Short-Term PE Generation Processes in the Soils of a Farmer Plots Network in the Madagascar Highlands: Actors and Drivers

Carbon sequestration in agricultural soils, through the accumulation of high-quality organic matter, represents great potential to mitigate climate change and simultaneously improve soil fertility. Such a challenge is particularly important and relevant in developing tropical countries like Madagascar, where soil carbon storage is vulnerable to climatic variations and where fertilization is generally applied through amendments in organic matter of various origins. The priming effect (PE) is considered here as the stimulation of the mineralization of soil organic matter (SOM) by a supply of fresh organic matter (FOM). PE results from different microbial processes driven by specific biotic and abiotic parameters. Depending on the processes involved, it has been suggested that PE could either counteract SOM accumulation or promote it. The objective of the present study was to explore the relationships between certain agricultural practices (type of crop, quality of fertilization, association with trees), the potential intensity of PE, as well as several abiotic (texture, quantity and quality SOM, nutrient enrichment) a1nd biotic (biomass and phylogenetic composition of microbial communities) factors which have been proposed in the literature as specific determinants of the different PE generation mechanisms. The soils for this study come from a network of farms in a commune in the Highlands of Madagascar. The PE, generated by a supply of 13C-enriched wheat straw, could not directly correlate with agricultural treatments. However, several indirect correlations could be found via several specific abiotic and microbial determinants that are discussed in terms of soil fertility restoration.

Mechanisms of soil respiration and its temperature sensitivity in black soil farmland

Soil respiration is the process of decomposition of organic matter in soil and microbial metabolism to produce carbon dioxide. In the context of climate warming and degradation of agricultural soil fertility, it becomes crucial to explore the mechanisms of soil respiration to increase carbon sequestration. In this paper, five biochar applications (0, 3.79, 7.58, 11.36, 15.15 t/ha) and two tillage methods (shallow ploughing, deep ploughing) were set up to explore the mechanism of soil respiration and its temperature sensitivity by studying the effects of tillage methods and different amounts of biochar application on soil properties, soil enzyme activities, soil respiration and its temperature sensitivity during the growing season of soybeans in the black soil area. The results showed that soil respiration rate increased with biochar application in the low biochar application range; the opposite trend was observed for high biochar application beyond the threshold (11.36 t/ha). The application of 11.36 t/ha of biochar amount had the strongest promotion effect on soil respiration, reaching 2.42 μmol m−2·s−1 in the shallow ploughing treatment and increasing 0.32 μmol m−2·s−1 in the deep ploughing compared to the shallow ploughing. The application of biochar significantly increased the activity of nitrogen and phosphorus enzymes and had an inhibitory effect on carbon cycle enzymes; the increased activity of nitrogen and phosphorus cycle enzymes provided sufficient substrate for microbial respiration and thus increased soil respiration, and the decrease in the enzymatic reaction of carbon cycle enzymes led to a decrease in temperature sensitivity. The temperature sensitivity of deep ploughing (2.18–2.59) got a more substantial reduction than that of shallow ploughing (2.34–3.53), which indicates that deep ploughing treatments can better reduce the mineralization of organic carbon than shallow tillage. Meanwhile, the temperature sensitivity of soil respiration reached a minimum with the application of 7.58 t/ha of biochar, which was reduced by 16% under deep ploughing treatment compared to the control, 33% under shallow ploughing treatment compared to the control, and also reduced by 27.27% under deep ploughing compared to shallow ploughing, which suggests that the addition of biochar reduces the loss of carbon to a certain extent. This study is important for assessing the effects of tillage practices and biochar combinations on carbon sequestration in agricultural soils in black soil areas.

Quantifying CO2 Emissions and Carbon Sequestration from Digestate-Amended Soil Using Natural 13C Abundance as a Tracer

The untapped potential for carbon sequestration in agricultural soils represents one of the most cost-effective tools for climate change mitigation. Increasing soil organic matter also brings other agronomic benefits such as improved soil structure, enhanced water-and-nutrient-retention capacity, and biological activity. Broadly, soil organic carbon storage is achieved by increasing carbon inputs (plant residues and organic amendments) and reducing carbon outputs (soil loss mechanisms, decomposition). With a focus on carbon inputs—more specifically, organic amendments—as leverage to increase soil organic carbon, we compared the respiration rates and carbon storage of incubated soil cores amended with maize straw, manure, two digestates and the solid fraction of digestate. Using the variation in the natural 13C abundance found in C4 and C3 plants as a tracer, we were able to partition the CO2 emissions between the exogenous organic matter materials elaborated from maize (C4) and native soil organic carbon (C3). The addition of digestate resulted in an additional 65 to 77% of remaining organic carbon after 92 days. The digestate-derived CO2 was fitted to a second-order kinetic carbon model that accounts for the substrate C that is assimilated into the microbial biomass. The model predicted a carbon sequestration potential of 56 to 73% of the total applied organic carbon after one to two years. For the solid fraction, the results were higher, with 89% of the applied organic carbon after 92 days and a sequestration potential of 86%. The soil priming ranged from −19% to +136% in relation to the unamended control soil, highlighting a surprisingly wide spectrum of results that warrants the need for further research on soil–digestate interactions.

Farmer perspectives on carbon markets incentivizing agricultural soil carbon sequestration

Climate change mitigation efforts to achieve net-zero emissions require not only decreasing current greenhouse gas emissions, but also the deployment of negative emissions technologies. Soil organic carbon sequestration in agricultural lands is one such negative emissions strategy, currently being incentivized predominantly through voluntary carbon offset markets. Through semi-structured interviews, we assess both conventional and organic farmer perspectives on soil carbon offset programs that have been created in the United States since 2017. The perspectives of farmers both participating and not participating in agricultural soil carbon markets were similar and consistent. Farmers in both groups expressed concerns about the convoluted, burdensome and unpredictable nature of receiving offset credits and emphasized that they were implementing practices for their own business interests and sustainability concerns, not the financial incentive of the generation of carbon credits. Based on our research, carbon offset credit payments for agricultural soil carbon sequestration are largely reaching farmers who were already implementing these beneficial practices or were already strongly interested in implementing these practices, and the payments for the offset credits are seen as a ‘gravy on top’, suggesting that these offset markets face strong challenges of ensuring true additionality essential to effective climate mitigation.

How does straw-incorporation rate reduce runoff and erosion on sloping cropland of black soil region?

Straw-incorporation has been widely utilized as an important practice for agricultural soil carbon sequestration, but few studies have been performed to investigate its impact on cropland runoff and erosion. In this study, the relationships between straw-incorporation rate and cropland runoff and erosion were quantified through field observations in the black soil region of Northeast China. Runoff and erosion were significantly influenced by straw-incorporation rate. Compared to the treatment without straw-incorporation, the mean runoff depth and soil erosion rate of seven observed rainfall events reduced by − 0.04–0.72 mm and − 3.34–15.34 t km−2. Under different straw-incorporation rates, the runoff reduction percentage (RRP) and erosion reduction percentage (ERP) varied from 7.3% to 90.3% and − 4.2–92.5%, with the means of 62.5% and 61.4%. RRP was mainly attributed to plant coverage, root mass density and the maximum 30-minute rainfall intensity, while plant coverage, leaf area index and the maximum rainfall intensity of ten minute were identified as the main factors influencing ERP. These parameters could explain 47%, 6%, 47% and 45%, 44%, 11% of total variations of soil erosion and runoff, respectively. Overall, straw-incorporation was effective in mitigating runoff and erosion under non-extreme rainfall event when straw-incorporation rate was greater than 4.5 t hm−2. Straw-incorporation rate of 9 t hm−2 had the best benefits to control runoff and erosion, followed by 13.5 t hm−2, while 1.125 t hm−2 had the least benefits. Our results highlight an importance of straw-incorporation in reducing cropland runoff and erosion and the implication for controlling soil erosion and associated environment problems by selecting best crop straw managements in semi-humid region of the world.

Modeling Climate Regulation of Arable Soils in Northern Saxony under the Influence of Climate Change and Management Practices

One approach to increasing the climate-regulating potential of the agricultural sector is carbon sequestration in agricultural soils. This involves storing atmospheric carbon dioxide in the soil in the form of soil organic carbon (SOC) through agricultural management practices (AMPs). Model simulations of area-specific current and future SOC stocks can be used to test appropriate AMPs. In this study, the CANDY Carbon Balance (CCB) model was used to determine how different AMPs could affect SOC stocks in a study area in northern Saxony, Germany. Specifically, we used scenarios with different intensities of sustainable AMPs to assess the potential effects of reduced tillage, crop cultivation, and fertilizer management, as well as the management of crop residues and by-products. The analysis was carried out for the simulation period 2020–2070, with and without consideration of climate change effects. The results showed an average carbon sequestration potential of 5.13–7.18 t C ha−1 for the whole study area, depending on the intensity of AMP implemented. While higher intensities of sustainable AMP implementation generally had a positive impact on carbon sequestration, the scenario with the highest implementation intensity only led to the second highest gains in SOC stocks. The most important factor in increasing SOC stocks was reduced tillage, which resulted in a carbon sequestration potential of 0.84 t C ha−1 by 2070. However, reduced application rates of fertilizers also proved to be critical, resulting in a reduction in carbon stocks of up to 2.2 t C ha−1 by 2070. Finally, the application of high-intensity sustainable AMPs was shown to be able to offset the negative impacts of an intermediate climate change scenario for most of the simulation period. Overall, the results not only confirmed existing knowledge on the effects of AMPs on carbon sequestration for a specific case study area, but also identified future management scenarios that stress the need for widespread adoption of sustainable management practices under changing climate conditions.

Optical assessment of the spatial variation in total soil carbon using laser-induced breakdown spectroscopy

Soil carbon storage is a substantial factor in the global carbon cycle. Carbon sequestration in agricultural soils, and the assessment and validation of soil carbon storage, are crucial for the mitigation of agricultural greenhouse gas emissions and for steering towards sustainable farming practices. Enforcement and verification of carbon sequestration policies, methods, and models require extensive soil carbon monitoring capability. However, current conventional laboratory-based methods for soil carbon estimation are laborious, expensive, and time-consuming. In this work, we have developed a compact, robust, and field-capable experimental device based on laser-induced breakdown spectroscopy (LIBS) for the rapid assessment of total soil carbon content and its spatial distribution in mineral soils. The carbon content quantification was performed using a spectral line of carbon at a wavelength of 193.1 nm emitted from the laser-induced plasma plume. The LIBS measurements were performed on soil samples collected from 28 different locations and various depths (up to 1 m) of a test field cultivated with a forage legume (red clover - Trifolium pratense, L.) and grass (Timothy - Phleum pratense, L.) mixture in eastern Finland. A calibration model was established based on a limited and randomly chosen sample set and validated by comparing soil carbon estimates obtained from various locations in the test field using the dry combustion (LECO) method. Further, we demonstrate here the usefulness of LIBS methodology for mapping three-dimensional carbon distribution at the test field. We emphasize here that the calibration model can be generalized to other sample areas under similar soil type with a relative error of less than 10 % and possesses potential for fast on-site determination of spatial variation in total soil carbon, reducing substantially the need of time-consuming sample processing in laboratory. Therefore, LIBS enables frequent and extensive spatial and temporal soil carbon mapping and has the potential to become part of the future carbon monitoring network.

Priming effects of nZVI on carbon sequestration and iron uptake are positively mediated by AM fungus in semiarid agricultural soils

We investigated the priming effect of nanoscale zero-valent iron (nZVI) on carbon sink and iron uptake, and the possible mediation by AMF (arbuscular mycorrhizal fungi, Funneliformis mosseae) in semiarid agricultural soils. Maize seed dressings comprised of three nZVI concentrations of 0, 1, 2 g·kg−1 and was tested with and without AMF inoculation under high and low soil moistures, respectively. The ICP-OES observations indicated that both low dose of nZVI (1 g·kg−1) and high dose of nZVI (2 g·kg−1) significantly increased the iron concentrations in roots (L: 54.5–109.8 %; H: 119.1–245.4 %) and shoots (L: 40.8–78.9 %; H: 81.1–99.4 %). Importantly, the absorption and translocation rate of iron were substantially improved by AMF inoculation under the low-dose nZVI. Yet, the excess nanoparticles as a stress were efficiently relieved by rhizosphere hyphae, and the iron concentration in leaves and stems can maintain as high as about 300 mg·kg−1 while the iron translocation efficiency was reduced. Moreover, next-generation sequencing confirmed that appropriate amount of nZVI clearly improved the rhizosphere colonization of Funneliformis mosseae (p < 0.001) and the development of soil fungal community. Soil observations further showed that the hyphae development and GRSP (glomalin-related soil protein) secretion were significantly promoted (p < 0.05), with the increased R0.25 (< 0.25 mm) by 35.97–41.16 %. As a return, AMF and host plant turned to input more organic matter into soils for microbial growth and Fe uptake, and such interactions became more pronounced under drought stress. In contrast, high dose of nZVI (2 g·kg−1) tended to agglomerate on the surface of hyphae and spores, causing severe deformation and inactivation of AMF symbionts. Therefore, the priming effects of nZVI on carbon sequestration and Fe uptake in agricultural soils were positively mediated by AMF via the feedback loop of the plant-soil-microbe system for enhanced adaptation to global climate change.

Conservation Tillage: A Sustainable Approach for Carbon Sequestration and Soil Preservation. A Review

Minimum tillage is a soil conservation tillage aimed at minimizing soil disturbance required for productive crop production. Unlike intense tillage, which uses ploughs to alter the soil's structure, this tillage technique does not turn the soil over. Only secondary tillage is used sparingly in minimum tillage, with primary tillage being totally avoided. Practices like minimum furrowing, using organic fertilizer, using biological pest control techniques, and using less pesticides are all included in minimum tillage. Soil erosion and soil degradation have been increased by the use of conventional agricultural techniques, such as extensive tillage centered on the removal of crop residue. Global interest in finding various sustainable ways to lower the concentration of greenhouse gases in the atmosphere has grown in recent years as a result of the gradual increase in their concentration. The amount of carbon stored in soil is 2-4 times greater than that in the atmosphere and four times greater than that in vegetation. In order to prevent or, carbon sequestration (CS) delay dangerous climate change entails storing other forms of carbon or transferring CO2 from the atmosphere into the soil. The potential of soils to store carbon and reduce the accelerated greenhouse effects by implementing various agricultural management strategies is covered in the current review. Conservation tillage techniques improve carbon sequestration in agricultural soils. Conservation tillage can be a practical way to store carbon in the soil and minimize the effects of climate change. Conservation tillage reduced the green house gas. Zero tillage has been identified as the most environmentally friendly tillage practice for the mitigation and adaptation to climate change processes. No-till farming is thought to make it possible to increase crop production sustainably in order to fulfill future agricultural demands

Root biomass and cumulative yield increase with mowing height in Festuca pratensis irrespective of Epichloë symbiosis

Increasing agricultural soil carbon sequestration without compromising the productivity of the land is a key challenge in global climate change mitigation. The carbon mitigation potential of grass-based agriculture is particularly high because grasslands represent 70% of the world’s agricultural area. The root systems of grasses transfer large amounts of carbon to below-ground storage, and the carbon allocation to the roots is dependent on the grasses’ photosynthesizing shoot biomass. In a common-garden experiment, Festuca pratensis was used as a model species to study how mowing and weed control practices of perennial cool-season fodder grasses affect total yield and root biomass. Additionally, grass-associated Epichloë endophytes and soil residual glyphosate were tested for their effect on the total yield and root biomass alone or in interaction with mowing. The results demonstrate that elevating the cutting height increases both cumulative yield and root biomass in F. pratensis. Endophyte symbiosis increased the total yield, while glyphosate-based herbicide residues in the soil decreased the root biomass, which indicates a reduction of soil bound carbon sequestration. The findings demonstrate that carbon sequestration and yield quantities on farmed grasslands may significantly be improved by optimizing strategies for the use of plant protection products and adjustment of mowing intensity.

An Overview of Carbon Sequestration in Agricultural Soils of Latin America and the Caribbean

A major challenge in Latin America and the Caribbean (LAC) is to determine how to meet the ever-growing global needs for food while preserving natural ecosystems and contributing to climate change mitigation. In the region, continuing land use is occurring and has caused a significant soil organic carbon (SOC) loss. We estimated the SOC reduction in three representative ecosystems of the region: forests (4.21 petagrams of carbon, Pg C, over 30 years), grasslands (1.86−7.32 Pg C, over different periods) and mangroves (0.36 Pg C over 25 years). Increasing SOC stocks in agricultural lands can help to mitigate the SOC loss due to land use change, but multiple factors influence the dynamics and response of the agricultural production and carbon sequestration. Farmers are pivotal actors that contribute to food production and could maintain SOC stocks; however, incentives or fair compensation must be considered to enable this. Moreover, national, and continental policies are needed for land restoration and sustainable management of soil health as a living entity through adoption of nature-positive practices which enhance soil organic matter (SOM) stocks, increase use-efficiency of inputs, and lead to nutrition-sensitive agriculture.

Effects of biochar and ligneous soil amendments on greenhouse gas exchange during extremely dry growing season in a Finnish cropland

Organic soil amendments such as manure, biochar and compost are among the most efficient and widely used methods to increase soil carbon sequestration in agricultural soils. Even though their benefits are well known, many wood-derived materials are not yet utilized in Nordic agriculture due to a lack of incentives and knowledge of their effects in the local climate. We studied greenhouse gas exchange, plant growth and soil properties of a clay soil cultivated with oat in southern Finland in an extremely dry year. Two years earlier, the field was treated with three ligneous soil amendments—lime-stabilized fiber from the pulp industry, willow biochar and spruce biochar—which we compared against fertilized and non-fertilized controls. We found that the soil amendments increased porosity and the mean soil water holding capacity, which was most noticeable in plots amended with spruce biochar. There was a trend indicating that the mean yield and overall biomass production were larger in plots with soil amendments; however, the difference to unamended control was seldom significant due to the high variance among replicates. Manual chamber measurements revealed that carbon dioxide and methane exchange rates were reduced most probably by the exceptionally hot and dry weather conditions, but no differences could be found between the amended and unamended treatments. The nitrous oxide emissions were significantly smaller from the vegetated soil amended with willow biochar compared with the unamended control. Emissions from non-vegetated soil, representing heterotrophic respiration, were similar but without significant differences between treatments. Overall, the studied soil amendments indicated positive climatic impact two years after their application, but further research is needed to conclusively characterize the specific effects of organic soil amendments on processes affecting greenhouse gas exchange and plant growth.

Soil organic matter pools response to perennial grain cropping and nitrogen fertilizer

Carbon sequestration in agricultural soils can play a pivotal role in the mitigation of accelerating climate change. Our research evaluated a continuum of agricultural cropping systems, including innovative perennial grain cropping, to assess which systems promote increases in and stabilization of soil organic matter (SOM). In comparison with conventional annual cropping systems, perennial grain cropping may be conducive to increased C accrual resulting from no-tillage management, longer growing seasons, and extensive root growth associated with these novel systems. Furthermore, the effects of N fertilizer addition on SOM dynamics under contrasting cropping systems were examined. We conducted physical SOM fractionation into particulate (POM) and mineral-associated organic matter (MAOM) in samples taken over two years from two experimental sites in Central Alberta, Canada. Five contrasting cropping systems (perennial-forage, perennial-grain, fall-grain, spring-grain and fallow) both with and without N fertilizer were tested. Our findings demonstrate that perennial-grain cropping was consistently superior in sequestering SOM-C compared to annual-grain crops at the surface soil layer (0–15 cm depth, Ps< 0.05). Over the duration of this experiment, perennial-grain cropping considerably boosted C accumulation in the recalcitrant SOM pools as represented by increasing MAOM, particularly at the Edmonton site, which is characterized by a clay-rich, Black Chernozemic soil (MAOM: 41.5 and 45.3 g C kg−1 in annual and perennial crops, respectively, P < 0.05). However, recurrent N fertilizer additions diminished C sequestration by perennial-grain cropping in both POM and MAOM fractions (Ps< 0.05). Correlation analysis indicated that accrual and allocation of C within the soil profile was more closely related to aboveground crop biomass productivity as opposed to root growth, particularly for generating more intermediate-labile POM. Our results shed light on how to achieve greater soil C sequestration as a function of cropping system options, N fertilizer addition and underlying soil texture.

Crediting agricultural soil carbon sequestration.

Regional consistency is necessary for carbon credit integrity.

Potential of no-till agriculture as a nature-based solution for climate-change mitigation in Brazil

Despite increasing efforts to combat climate change, greenhouse gas (GHG) emissions continued to grow. In this context, conservationist agricultural systems such as no-till (NT) can play an important role. However, the potential of this system to mitigate GHG emissions has been questioned more recently. Brazil is the second country with the largest NT area, representing around 18% of the global area under NT. Here, we examined the effects of the adoption of NT from the conversion of native vegetation, conventional tillage (CT), and pasture in layers 0–30 and 0–50 cm of the soil. We used a total of 124 comparison pairs to analyze changes in soil organic carbon (SOC) using two approaches (deriving SOC change factors and the adjustment of empirical equations on SOC temporal dynamics). Our results showed that the adoption of NT in NV areas reduces SOC stocks by between 4% and 8%. However, in areas previously managed by CT systems or pasture, NT is a potential alternative for promoting carbon sequestration in agricultural soils in Brazil's different regions. The results showed that the SOC accumulation is not restricted to superficial layers of the soil (0–30 cm) but was also effective up to 50 cm in depth, with gains varying between 9% and 25%. Thus, our results consistently demonstrate that for Brazilian conditions, NT when compared to CT systems or pastures, predominantly result in SOC gains, and represent an alternative to promote sustainable agriculture, which can contribute to the mitigation of GHG emissions and food security.

Soil Carbon Dynamics, Sequestration and Productivity of Predominant Cropping Systems under Long Term (9 years) Inorganic and Organic Fertilization in Semi-Arid Deccan Plateau, India

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).