Soil Carbon Management Research Articles

Soil Carbon Regulating Ecosystem Services in the State of South Carolina, USA

Sustainable management of soil carbon (C) at the state level requires valuation of soil C regulating ecosystem services (ES) and disservices (ED). The objective of this study was to assess the value of regulating ES from soil organic carbon (SOC), soil inorganic carbon (SIC), and total soil carbon (TSC) stocks, based on the concept of the avoided social cost of carbon dioxide (CO2) emissions for the state of South Carolina (SC) in the United States of America (U.S.A.) by soil order, soil depth (0–200 cm), region and county using information from the State Soil Geographic (STATSGO) database. The total estimated monetary mid-point value for TSC in the state of South Carolina was $124.36B (i.e., $124.36 billion U.S. dollars, where B = billion = 109), $107.14B for SOC, and $17.22B for SIC. Soil orders with the highest midpoint value for SOC were: Ultisols ($64.35B), Histosols ($11.22B), and Inceptisols ($10.31B). Soil orders with the highest midpoint value for SIC were: Inceptisols ($5.91B), Entisols ($5.53B), and Alfisols ($5.0B). Soil orders with the highest midpoint value for TSC were: Ultisols ($64.35B), Inceptisols ($16.22B), and Entisols ($14.65B). The regions with the highest midpoint SOC values were: Pee Dee ($34.24B), Low Country ($32.17B), and Midlands ($29.24B). The regions with the highest midpoint SIC values were: Low Country ($5.69B), Midlands ($5.55B), and Pee Dee ($4.67B). The regions with the highest midpoint TSC values were: Low Country ($37.86B), Pee Dee ($36.91B), and Midlands ($34.79B). The counties with the highest midpoint SOC values were Colleton ($5.44B), Horry ($5.37B), and Berkeley ($4.12B). The counties with the highest midpoint SIC values were Charleston ($1.46B), Georgetown ($852.81M, where M = million = 106), and Horry ($843.18M). The counties with the highest midpoint TSC values were Horry ($6.22B), Colleton ($6.02B), and Georgetown ($4.87B). Administrative areas (e.g., counties, regions) combined with pedodiversity concepts can provide useful information to design cost-efficient policies to manage soil carbon regulating ES at the state level.

Field scale estimates of soil carbon stocks on ten heavy textured farms across Ireland

The world's soils store vast amounts (≈2,500 GT) of Carbon which acts as a vital sink to counterbalance the effects of increasing atmospheric carbon dioxide. There have been fruitful efforts to quantify soil Carbon stocks at national scales, which are required for policy level decisions but lack the high resolution required to support farm specific decisions. It is hypothesised that farm scale evaluations of soils can provide insight that is masked in national scale studies and can allow for spatially explicit management approaches to optimise soil Carbon storage and sequestration, such that it can be prioritized within profitable production systems. The objective of the present study was to estimate Carbon stocks on a range of heavy textured soils at field and farm scale and to quantify Carbon storage relative to national scale estimates. Ten grassland dairy farms (mean area of 52.2 Ha) were surveyed, sampled and classified to determine soil types and quantify soil Carbon stores. The level of Carbon present (mean: 346.0 T/Ha) at these sites was greater than previous averages on such soils quantified at national scale (by a factor of 1.1–3.9 depending on soil type). Furthermore, if Carbon saturation potential was realised, the amount of Carbon stored could be increased by an average of 792.1 T/Ha in each profile (from 346.0 to 1138.1 T/Ha). Current management has fostered the retention of large stores of soil Carbon on such soils/farms which co-exist within highly productive farm systems. As there is a societal demand to retain and enhance soil carbon stores to mitigate climate change, high Carbon soils should be identified and, under appropriate policies, commodified to offer a direct incentive to retain soil Carbon. The value of this resource should be recognised and polices to ensure a spatially explicit approach for soil Carbon management should be adopted.

Land use types and topographic position affect soil aggregation and carbon management in the mountain agro‐ecosystems of the Indian Himalayas

AbstractThe impacts of land use and topographic position can be evaluated through the carbon management index (CMI) that conceptualizes the carbon lability and soil aggregation. Soil aggregation patterns, carbon pools, and carbon management of the soil system not only affect the distribution of the mineral fraction of the soil but also the organic components. This study was conducted with the objectives of investigating soil carbon pools, soil aggregation, and CMI under seven land use types (dense forest, mixed forest, scrub forest, horticulture, agri‐horticulture, irrigated, and rainfed cropping systems) under three topographic positions (summit, slope, and gully) in the mountain agro‐ecosystem, of the Indian Himalayas. A total of 405 composite soil samples [7 land use types and 3 topographic positions and 21, 18, 33, 9, 12, 24, and 18 replications for the dense forest, mixed forest, scrub forest, horticulture, agri‐horticulture, irrigated, and rainfed cropping systems, respectively] were collected for laboratory analyses. It was observed that the dense forest land use type has the highest Walkley–Black carbon (WBC), soil aggregation, total carbon (TC), and CMI values, while significantly (p < .05) lowest amount was observed with rainfed land use system. Land use type had minimum effect on nonlabile carbon (NLC), lability of carbon (LC), lability index (LI), and carbon pool index (CPI) of the agro‐ecosystem. We conclude that the CMI value was in the range of ~31 to 88%, 24 to 82%, and 23 to 74% for summit, slope, and gully topographic positions of land use types, respectively. An average CMI was significantly (p < .05) the highest in the dense forest (~48%) followed by scrub forest and mixed forest (~43 and 40%, respectively). Meanwhile, irrigated land use had significant (p < .05) lowest CMI (~25%). Overall, results indicated that land use types and topographic positions significantly influenced with lability of the carbon. These results suggest that restoration of degraded rainfed and irrigated agriculture lands to agri‐horticulture, dense, mixed, and scrub forest lands decrease in intensity of land use could increase carbon and soil aggregation sustainability in the study area as well as other similar mountainous agro‐ecosystems.

Impact of Joint Multiple Agricultural Technology Production of Beans on Household Nutrition Outcome in East Africa

This study analyzes the impact of beans produced under joint multiple agricultural technologies (Improved beans variety, soil carbon management, integrated pest control, and use of compost manure) on nutrition outcome of stunting, underweight, and wasting in Kenya, Uganda, and Tanzania. Adoption of technologies in East Africa has been in isolation only focusing on single technologies. However, farmers typically adopt joint multiple agricultural technologies as complements or substitutes thus technologies to be adopted dependent on early technology choices. The objective of the study was to analyze the impact of the nutrition outcome variables in terms of stunting, wasting, and underweight for the best joint multiple agricultural technology combinations as a set of explanatory variables (z). This study adopts the multinomial endogenous switching regression model to correct for the selection bias and endogeneity. Results indicate that joint multiple agricultural technologies had a significant impact on the overall nutrition outcome in East Africa households. It is concluded that households in East Africa rarely use a single agricultural technology but rather a combination of different joint technologies in order to improve their nutrition outcome. The findings recommend that households should adopt joint multiple agricultural technologies rather than focusing on single technologies.

Predicted Maps for Soil Organic Matter Evaluation: The Case of Abruzzo Region (Italy)

Organic matter, an important component of healthy soils, may be used as an indicator in sustainability assessments. Managing soil carbon storage can foster agricultural productivity and environmental quality, reducing the severity and costs of natural phenomena. Thus, accurately estimating the spatial variability of soil organic matter (SOM) is crucial for sustainable soil management when planning agro-environmental measures at the regional level. SOM variability is very large in Italy, and soil organic carbon (SOC) surveys considering such variability are difficult and onerous. The study concerns the Abruzzo Region (about 10,800 km2), in Central Italy, where data from 1753 soil profiles were available, together with a Digital Elevation Model (DEM) and Landsat images. Some morphometric parameters and spectral indices with a significant degree of correlation with measured data were used as predictors for regression-kriging (RK) application. Estimated map of SOC stocks, and of SOM related to USDA (United States Department of Agriculture) texture—an additional indicator of soil quality—were produced with a satisfactory level of accuracy. Results showed that SOC stocks and SOM concentrations in relation to texture were lower in the hilly area along the shoreline, pointing out the need to improve soil management to guarantee agricultural land sustainability.

Effects of long-term fertiliser regime on soil organic carbon and its labile fractions under double cropping rice system of southern China

ABSTRACT This study was designed to explore changes in soil bulk density, soil organic carbon content, soil organic carbon stock and soil labile organic carbon fractions under 34 years fertilizer regime in the double-cropping rice system of southern China. The experiment including five fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (LOM), 60% organic manure and 40% chemical fertilizer (HOM), and without fertilizer input as control (CK). The results showed that soil bulk density in the 0-20 cm soil layer with long-term fertilizer treatments were significantly decreased compared to CK treatment. The soil organic carbon content and stock with RF, LOM and HOM treatments were significantly higher than that of MF and CK treatments. These results confirmed by the soil carbon management index which were significantly increased with RF, LOM and HOM treatments. As a result, combined application of organic manure with chemical fertilizer is a benefit nutrient management for improving soil organic carbon content and stock, soil carbon management index in paddy field of southern China.

Soil organic matter fractions and carbon management index under integrated crop-livestock system

The objective of this work was to evaluate the carbon content of the physical, chemical and oxidizable fractions of soil organic matter (SOM) and to calculate the carbon management index (CMI) in an area managed under an integrated crop-livestock system (ICLS) in the western region of Paraná - Brazil. The experiment was carried out at the experimental farm, belonging to the Universidade Estadual do Oeste do Paraná. Seventeen areas, which are managed in different ways, fifteen in ICLS and two areas of controls (Forest and Haymaking), using the design divided with two nested controls, with three replications were evaluated. Deformed and undisturbed soil samples were collected from all the areas to determine the total organic carbon (TOC), carbon stock, the physical, chemical and oxidizable fractions of SOM and the CMI in the layers of 0-0.05, 0.05-0.1 and 0.1-0.2 m. Little significant changes in the fractions were found for the management of the ICLS area in relation to the Forest and the area of Haymaking, although the Forest presented the best values for most of the studied fractions. It is recommended to adopt sustainable practices, such as ICLS, even though the average fractions tend to take time to match reference areas.

Soil Organic Carbon Pools under <i>Terminalia chebula</i> Retz. based Agroforestry Systemin Himalayan Foothills, Indiax

Knowledge of carbon (C) pools in soils is helpful in devising practices for efficient carbon management in intensive cropping systems. Carbon fractions of soil organic carbon are used asan indicator for land-use induced change in soil quality. The present study evaluated carbon pools under Terminalia chebula(chebulic myrobalan) based agroforestry system supplied with different nutrient sources, viz. farmyard manure, poultry manure, vermicompost, wheat straw and inorganic fertilizer (NPK @ 100:80:60). Carbon fractions, viz. very labile (C 1 frac ), labile (C 2 frac ), less labile (C 3 frac ) and non-labile (C 4 frac ), were analysed at 0–15 and 15–30 cm soil depth. The higher value of C 1 frac (13.8%), C 2 frac (4.8%), C 3 frac (8.3%) and C 4 frac(11.1%) were recorded under agroforestry as compared to open system. Among the nutrient sources, all the carbon fractions were higher under 100% integrated nutrient sources as compared to controlled treatment. Microbial biomass carbon (MBC) was recorded higher (298.31 μg g –1 ) under agroforestry system compared to the open system (290.63 μg g –1 ) at 0–15 cm. Among the different nutrient sources, higher MBC (458.66 μg g –1 ) at 0–15 cm and lower (340.59 μg g –1 ) at 15–30 cm soil depth was recorded in 100% integrated treatment.Thus, agroforestry-based land-use types and integrated nutrient management are more efficient for soil health and carbon management in Himalayan foothills.

Multitemporal Analysis of Soil Sealing and Land Use Changes Linked to Urban Expansion of Salamanca (Spain) Using Landsat Images and Soil Carbon Management as a Mitigating Tool for Climate Change

The lack of urban sustainability is a widespread deficiency in urban agglomerations. To achieve adequate land use, we present a methodology that allows for: 1) the identification of the impacts caused by urban expansion since 1956 to the present in Salamanca (Spain); and 2) the promotion of a more sustainable future in urban development. A multi-temporal assessment of land use was made by remote sensing, while sustainability criteria were analyzed using the multicriteria analysis (MCA) with Geographical Information Systems (GIS). In addition, we established recommendations for soil carbon management in semi-arid ecosystem soils that contribute to climate change mitigation. The results show an increase of the urbanized area from 3.8% to 22.3% in the studied period, identifying up to 15% of buildings in zones with some type of restriction. In 71% of the cases, urbanization caused the sealing of productive agricultural soils (2519 Ha), almost 20% of which were of the highest quality. In last few decades, an excessive increase of built-up areas in comparison to population dynamics was identified, which causes unnecessary soil sealing that affects the food production and the capacity to mitigate climate change by managing the carbon cycle in the soil.

Short-term responses of soil organic carbon and its labile fractions to different manure Nitrogen input in a double-cropping rice field

AbstractChanges in soil bulk density (BD), soil organic carbon (SOC) content, SOC stocks and soil labile organic C fractions (mineralizable C (Cmin), microbial biomass C (MBC), dissolved organic C (DOC), particulate organic C (POC), light fraction organic C (LFOC) and permanganate oxidizable C (KMnO4-C)) were explored over 3 years in a double-cropping rice system of southern China. Five organic and inorganic nitrogen (N) inputs were used: (1) 100% from chemical fertilizer (M0), (2) 30% from organic manure, 70% from chemical fertilizer (M30), (3) 50% from organic manure, 50% from chemical fertilizer (M50), (4) 100% from organic manure (M100) and (5) without N fertilizer input, as control (CK). All organic manure treatments decreased BD significantly in the 0–20 cm soil layer compared with CK. The SOC content and stocks with organic manure were significantly higher than in M0 or CK; also, the cumulative amount of SOC stocks in M30 and M50 increased at the plough layer, compared with CK. The non-labile C content increased significantly and the percentage of labile C were significantly higher with organic manure application than in M0 or CK. The soil carbon management index (CMI) also increased significantly under the application of organic manure. Therefore, application of organic manure can increase the pool of stable C in surface layers, and increase content and percentage of labile C. Based on soil carbon storage and CMI, the combined application of 30 or 50% N of organic manure with chemical fertilizer improves carbon cycling services and soil quality in southern China paddy soil.

Soil carbon sequestration in grazing systems: managing expectations

Grazing systems emit greenhouse gases, which can, under specific agro-ecological conditions, be partly or entirely offset by soil carbon sequestration. However, any sequestration is time-limited, reversible, and at a global level outweighed by emissions from grazing systems. Thus, grazing systems are globally a net contributor to climate change and the time scale of key processes needs to be factored into any mitigation efforts. Failing to do so leads to unrealistic expectations of soil carbon management in grazing systems as a mitigation strategy. Protecting the large carbon stocks in grazing lands is also essential in order to avoid further climate change from additional CO2 release. Despite the time-limited and reversible nature of soil carbon sequestration in grazing lands, sequestration should be promoted in cases where it delivers environmental and agronomic benefits as well as for its potential, particularly on degraded land, to increase the feasibility of limiting global warming to less than 2 or preferably 1.5 °C. Some peer-reviewed sequestration estimates are of a similar order of magnitude to other food systems mitigation options over a 10–20 years period, such as reducing food loss and waste by 15% or aligning diets with current health related dietary-recommendations. However, caution should be applied to such comparisons since mitigation estimates are associated with large uncertainties and will ultimately depend on the economic cost-benefit relation, feasibility of implementation and time frame considered.

Barriers to and opportunities for the uptake of soil carbon management practices in European sustainable agricultural production

ABSTRACT Soil carbon management practices are those that add and maintain organic carbon in the soil. These agricultural practices can potentially both contribute to climate change mitigation and increase the soil’s resilience to physical and biological stresses. The paper draws on research findings from five regions across Europe to identify regionally-specific barriers to and opportunities for the adoption of soil carbon management practices. Data were derived from 50 interviews with policy-makers and advisers and 5 stakeholder workshops in Denmark, Italy, Hungary, Poland and Spain. Several barriers to the uptake of soil carbon management practices were common across all regions, however, regional variations were also identified highlighting the importance of understanding the context into which these practices are introduced. Key barriers related to existing biophysical conditions, lack of financial support, farmer knowledge and experience, and the quality of the advisory service. Opportunities included providing economic incentives, harmonizing regulation, supporting long term thinking and planning for resilience and providing good quality advice. We conclude that in addition to persuasive mechanisms for encouraging the adoption of these practices, what is required is a more process-oriented approach that focuses on a series of experiential changes and fosters farmer learning through interactive models of communicative intervention.

Soil, Striga, or subsidies? Determinants of maize productivity in northern Ghana

AbstractHigh yield gaps persist in sub‐Saharan Africa and increased fertilizer use is considered among the crucial measures to increase productivity. Despite high government investments, particularly in fertilizer subsidy programs (FSPs), overwhelming evidence has revealed their inefficiency. This study employs a multidisciplinary approach to identify the determinants of low maize yields in the Guinea savanna zone of Ghana. We conducted a socioeconomic household survey and analyzed plot‐specific soil samples. Econometric models were estimated based on both socioeconomic and soil variables. The results show that a common parasitic weed, Striga, and labile soil structure have significant effects on yield in the study region. Plot sizes were recorded both from farmers’ direct elicitation and using GPS devices. Considerable discrepancies were detected between self‐reported and GPS‐measured plot sizes. Fertilizer samples from randomly selected agro‐input shops were analyzed to control for adulterated or fake inputs. The measured nutrient contents of the samples reflected the composition indicated on the package labels. Findings underline the need of site‐specific data collection, supported by laboratory‐based soil test results, to efficiently address low productivity. Although there are no signs of fertilizer adulteration, governance challenges persist in targeting, timing, and elite capture in the distribution system of the subsidy program. The study shows that the FSP has not been an effective standalone measure. Rather, the government needs to invest in capacity building and extension services to address the site‐specific problems through comprehensive soil fertility management techniques and weed control. Promoting soil carbon management, minimum mechanical stress, crop rotation, and permanent soil cover should be further investigated as options for the region.

Agricultural Productivity and Soil Carbon Dynamics: A Bioeconomic Model

AbstractWe examine the dynamic management of a soil resource—the issue at the core of both environmental and development challenges in developing countries. Our theoretical framework extends the traditional bioeconomic model of renewable resources to soil carbon management and investigates the effects of changes in agricultural practices on farmers' natural resource base and livelihoods. We parameterize the model using an eight‐year panel data set from an agronomic experiment and data from household and market surveys in the western Kenyan highlands. The optimal maize yields and soil carbon stocks are higher than those observed in the region. This divergence is partly explained by farmers' heterogeneous time preferences (with the implied discount rates of 5% to 25%), information barriers, and market imperfections. The steady‐state shadow price for soil carbon ranges from $95/Mg to $168/Mg, indicating a significant opportunity cost for soil mismanagement.

Guiding carbon farming using interdisciplinary mixed methods mapping

Abstract In recognition of the need to address complex environmental problems, some ecological studies have adopted social research methods to better understand the complexity of social‐ecological systems management. The overwhelming majority of these studies stop short of fully embracing qualitative methodologies. The lack of integrative social and natural science data for a topic such as soil carbon farming is problematic as theoretical carbon sequestration opportunities identified through soil mapping and process‐based models can fail to deliver the sequestration levels promised when introduced on‐the‐ground. Such mapping needs to account for the human factors involved in delivering increased soil carbon on‐farm. Here, we develop a mixed methods mapping approach to explore the potential for increasing soil carbon stocks on upland farms in the UK. Our approach considers ecological and social complexity through application of soil science, ecology, participant observation, interviews and a focus group. Our maps revealed landscapes that are full of carbon farming opportunity, but contain previously hidden barriers to the delivery of increased soil carbon. For example, they revealed that carbon farming can be considered by farmers to work in opposition to perceived ‘good farming’ practices and be correlated with increased incidents of livestock disease. We also discovered that the use of maps in research can be problematic as they can close down discussion and exclude local representation of an area. Trialling an interdisciplinary mixed methods approach produced new, deeper and more richly‐textured understandings about how soil carbon management is produced socially as well as ecologically on upland livestock farms. Our findings have potential to improve the success of future carbon farming initiatives by incorporating farmer knowledge and social drivers of implementation. A plain language summary is available for this article.

Effects of winter cropping mode on soil organic carbon and carbon management index of double rice paddy

To explore the effects of winter crops recycling into paddy field on soil carbon pool, we cultivated rape, Chinese milk vetch, ryegrass and potato in winter season after harvesting double-season rice, with fallow as control (CK). The contents of soil organic carbon (SOC) and labile organic carbon (LOC) in the harvest of early and late rice were measured, and the stable carbon, activity of carbon pool, carbon pool index, carbon pool activity index and carbon pool management index (CMI) were calculated. Results showed that winter cover crops returning increased SOC content by 1%-8% and 3%-18% after harvest of early rice and late rice, respectively in comparison with CK. Cultivating rape, Chinese milk vetch and ryegrass all increased the LOC content, with enhancement of 16.2%-84.2% and 24.4%-28.1% after harvest of early rice and late rice, respectively. The CMI of all winter crop treatments presented a growth ratio of 1.4%-41.8% compared to CK. In conclusion, the cultivation of winter crop and recycling to field promoted soil carbon fixation and soil quality, among which the ryegrass and Chinese milk vetch showed better comprehensive effect.

Assessing the terrestrial capacity for Negative Emission Technologies in Ireland

Negative emissions technologies (NETs) and their potential role in meeting emission targets is a rapidly growing and contentious area of climate change mitigation research. The literature ranges in scope from general reviews of NETs options to research and development through applied case studies. Within this field, a gap exists in the application of this growing body of research to the unique limitations and opportunities of a specific nation. Ireland is a small developed island nation in the EU with a unique emissions profile, as 32% of the total comes from agriculture due to the high number of cattle. In this study we aim to assess the potential capacity of terrestrial NETs options for Ireland and review the nation-specific context for their deployment. Despite the proportionally high representation of biochar and carbon capture and storage in the international NETs research, in an Irish context afforestation and bioenergy crops are much more established practices and could readily be considered in possible emission pathways that use NETs. Higher capacities were found for NETs options that are currently unavailable (direct air carbon capture and storage and bioenergy with carbon capture and storage), while options available to deploy at scale (afforestation, soil carbon management and biochar) have capacities limited by saturation of soil carbon stock and have higher risk of reversibility due to impermanence. Hence, while we estimate a reasonable technical capacity for NETs in Ireland, emission reduction remains the highest priority for feasibly meeting a Paris-aligned carbon quota for Ireland.

Effects of Different Soil Tillage Systems on Soil Carbon Management Index Under Double‐Cropping Rice Field in Southern China

Core Ideas SOC and AOC were higher in CT and RT treatments than RTO at 0 to 5, 5 to 10, and 10 to 20 cm. Lability, LI, and CMI in the CT treatment were higher than NT treatment at 0 to 5 and 10 to 20 cm. SOC stocks were significantly higher in NT at 0 to 5 cm than under the RTO treatment. SOC stocks were significantly higher in CT and RT at 5 to 10 and 10 to 20 cm than under RTO. Interactions between tillage and soil organic carbon (SOC) impact soil structure, soil quality, and the calculated soil carbon management index (CMI). However, the effects of different tillage and residue management systems on the dynamics of SOC remain unclear under double‐cropping rice (Oryza sativa L.). Therefore, the effects of soil tillage and incorporated residues on soil bulk density, SOC, soil active organic carbon (AOC), and the CMI were studied in a southern China double‐cropped rice system. The experiment included four tillage treatments: conventional tillage with residue incorporation (CT), rotary tillage with residue incorporation (RT), no tillage with residue retention (NT), and rotary tillage with residue removed as a control (RTO). The results indicated that soil bulk density increased under NT in the 0‐ to 20‐cm layer, SOC was higher under NT than that of other treatments, and SOC in the 5‐ to 20‐cm layer was higher under CT and RT than under NT and RTO. The greatest SOC and AOC contents were observed under CT at the 5‐ to 10‐cm and 10‐ to 20‐cm layers. The CMI was used to assess the soil quality change with different soil tillage practices. The application of residue combined with conventional tillage or rotary tillage was more effective for increasing soil carbon pool index (CPI) and CMI than was rotary tillage with the residue was removed. The CMI for the 0‐ to 10‐cm depth under RT and CT were higher (P < 0.05) than the NT treatment. Meanwhile, RT significantly enhanced the SOC stocks over the RTO treatment at three different depths. As a result, based on soil CMI and C storage, double‐cropping rice using a no‐tillage system where crop residues are not removed could increase SOC in the surface 5 cm.

Conceptual basis of managing soil carbon: Inspired by nature and driven by science

The anthropogenically induced increase of 146% in atmospheric concentration of carbon dioxide (CO2), from 278 ppm in the preindustrial era (circa 1750) to 405.5 ppm in 2017, is presently increasing at the rate of 2.24 ppm y−1 (0.55%) (WMO 2018). This increase, along with those of methane (CH4; from 722 ppb to 1,859 ppb by 257% and increasing at the rate of 0.38% or 6.9 ppb y−1) and nitrous oxide (N2O; from 270 ppb to 330 ppb at the rate of 0.27% or 0.93 ppb y−1) has already caused ~1°C (1.8°F) increase in global temperature since the Industrial Revolution (IPCC 2018) with dire consequences as exemplified by the increase in frequency of extreme events throughout the world. However, there is still a chance to implement the Paris Climate Agreement proposed at the Paris Climate Conference (COP21) in 2015 and limit the global warming to 1.5°C (2.7°F). To achieve this limit, however, the world must identify noncarbon (C) fuel sources and simultaneously adopt techniques of removing CO2 from the atmosphere or implement negative emission technologies (NET). Carbon sequestration in soil is an important NET option with numerous cobenefits of enhancing agricultural production, improving water resources, and strengthening biodiversity (Lal 2010).

More than Serendipity: The Potential to Manage Soil Carbon and Emissions While Promoting Low-Input Agriculture with Serendipitoid Mycorrhizae

Organic matter (OM) has a tremendous influence on the biological, chemical, and physical properties of soils, making it a vital component of healthy agricultural systems. Release of the nutrients locked within soil OM requires the activity of soil microorganisms, primarily decomposers, to transform it into nutritive forms that can be used by other microbes and plants. OM turnover is a good thing, as it liberates the locked up nutrients. However, when this liberation is accomplished by free-living decomposer communities, i.e., those not typically forming relationships with plants, the carbon may be used mostly to form microbial biomass and the rest respired as CO2, thereby aggravating greenhouse gas emission. Serendipitoid fungi (e.g., Serendipita spp.) are soil-dwelling basidiomycetes, known for decades to form mycorrhizal associations with wide variety of plant species. We hypothesize that serendipitoid fungi are capable of decomposing OM in a manner akin to free-living decomposer communities. However, serendipitoid fungi are capable of colonizing the root systems of plant community members, potentially restricting access to nutritional stores in the soil, thus imparting efficiency to the system and limiting unnecessary losses. From our perspective, this is a more rational, resilient, and ultimately more sustainable strategy than the annual addition of inorganic forms of micro- and macronutrients. Using microbes like Serendipita spp. in this manner could ultimately make the system less susceptible to nutritional fluxes that may influence productivity and stress tolerance in our crop plants.