Soil Carbon Changes Research Articles

Changes of soil bacterial community, network structure, and carbon, nitrogen and sulfur functional genes under different land use types

Soil microorganisms participate in almost all soil ecological processes and are essential in maintaining ecosystem functions and terrestrial carbon, nitrogen, and sulfur cycles. Soil bacterial communities, networks, biogeochemical cycles, and land use types influence it. However, there are few studies on the changes in these indicators and their influencing factors under different land use types. Taking Dongting Lake watershed as an example, high-throughput sequencing technology combined with FAPROTAX were used to analyze the characteristics and influencing factors of soil bacterial community, network structure, and C, N, and S cycle function genes under different land use conditions. Land use types include paddy fields (PF), garden plots (GP), woodland (WL), and sloped arable land (SAL). PLS-PM model and redundancy analysis method were used to study the mechanism of soil bacterial community, network structure, functional genes, and environmental variables. The results showed that the relative abundance of dominant phylum and dominant fungi changed significantly in different land use types. The first three dominant gates in WL had the most considerable abundance and the most extensive diversity index of PF. The symbiotic network of PF has the most effective connectivity and average degree, the minor network diameter, the most complex network structure, and fierce competition among species within the same ecological niche. The results of functional genes showed that different land use types significantly changed the abundance of soil C, N, and S cycle functional genes, and soil bacteria predicted the highest abundance of functional genes in GP. C, N, and S circulating function genes were significantly correlated with pH, soil nutrients, and soil texture (P < 0.05). PLS-PM model and redundancy analysis showed that soil pH was the main factor affecting the bacterial community, network structure, and functional genes, followed by soil nutrients.

Effects of nitrogen addition on greenhouse gas fluxes during continuous freeze-thaw cycles in a cold temperate forest.

Both nitrogen (N) deposition and soil freeze-thaw cycles (FTCs) induce pulses of greenhouse gas (GHG) emissions in cold temperate zones due to changes in soil carbon (C) and nitrogen (N) turnover. However, the combined effects of N addition and FTCs on GHG fluxes have received little research attention, particularly in boreal forests. We conducted a laboratory incubation experiment using intact soil cores from Rhododendron dauricum-Larix dahurica plots to investigate the GHG flux response to these combined effects. We separated the soil samples into seven groups (no, low, medium, and high sodium nitrate addition and low, medium, and high ammonium chloride addition) and exposed each group to continuous FTC conditions. The N2O and CO2 emissions were eventually stimulated by the FTCs, while CH4 uptake was inhibited by FTCs but responded differently under different N addition treatments. All the treatments had substantially increased N2O emissions compared to the control. However, the soil respiration rate significantly increased only with medium sodium nitrate addition, and high levels of N addition (regardless of form) inhibited CH4 uptake. These findings demonstrate that FTCs and N addition (in various forms and levels) have considerable effects on GHG emissions in temperate forest ecosystems. Moreover, dissolved organic carbon (DOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and inorganic nitrogen in soil are potential factors that drive GHG emissions and are necessary considerations in predicting future feedback effects of GHG emissions on climate change.

Fire effects on soil carbon cycling pools in forest ecosystems: A global meta-analysis

Changes in soil carbon (C) pools driven by fire in forest ecosystems remain equivocal, especially at a global scale. In this study we analyzed data from 232 studies consisting of 1702 observations to investigate whether ecosystem type, climate zone, stand age, soil depth, slope, elevation, and the time since fire in influence of forest soil carbon pools to fire regime (fire type, fire season, fire intensity). Additionally, we explored the potential mechanisms of the relationships between multiple response variables to the fire using linear regression and random forest models. On aggregate, fires significantly increased the mean effect sizes of several key soil carbon cycling components-including microbial biomass carbon (MBC), dissolved organic carbon (DOC), total carbon (TC), pyrogenic carbon (PyC), soil organic matter (SOM), soil organic carbon (SOC) by 0.77, 0.89, 0.87, 1.22, 0.97 and 0.93, respectively, compared to unburned forests ecosystems. However, the fire effects on soil C pools vary widely between environmental factors and duration, and are mediated by factors such as tree species, fire type, and soil layer. A correlation analysis displayed the effects of fire on MBC and DOC were significantly and negatively correlated with elevation. Fire effects on the forest floor and mineral soil indicated significantly increased PyC. SOC and TC in coniferous tree species are the most sensitive to fires, thereby altering important feedback relationships with the fire-vegetatale-climate system. Interestingly, latitude has a stronger influence on SOC than mean annual precipitation or elevation, indicating that variations in latitude play a significant role in regulating the amount of SOC in forest ecosystems. Overall, the results illustrated geographic variation in fire effects on soil C cycling underscores the need for region-specific fire management plans, and help us understand the responses of soil C cycling to fire in forest ecosystems, and facilitate decision-making to forest fire management.

The spatial variation and driving factors of soil total carbon and nitrogen in the Heihe River source region

Soil carbon and nitrogen levels are key indicators of soil fertility and are used to assess ecological value and safeguard the environment. Previous studies have focused on the contributions of vegetation, topography, physical and chemical qualities, and meteorology to soil carbon and nitrogen change, but there has been little consideration of landscape and ecological environment types as potential driving forces. The study investigated the horizontal and vertical distribution and influencing factors of total carbon and total nitrogen in soil at 0–20 and 20–50 cm depths in the source region of the Heihe River. A total of 16 influencing factors related to soil, vegetation, landscape, and ecological environment were selected, and their individual and synergistic effects on the distributions of total carbon and total nitrogen in soil were assessed. The results show gradually decreasing average values of soil total carbon and total nitrogen from the surface layer to the bottom layer, with larger values in the southeast part of the sampling region and smaller values in the northwest. Larger values of soil total carbon and total nitrogen at sampling points are distributed in areas with higher clay and silt and lower soil bulk density, pH, and sand. For environmental factors, larger values of soil total carbon and total nitrogen are distributed in areas with higher annual rainfall, net primary productivity, vegetation index, and urban building index, and lower surface moisture, maximum patch index, boundary density, and bare soil index. Among soil factors, soil bulk density and silt are most closely associated with soil total carbon and total nitrogen. Among surface factors, vegetation index, soil erosion, and urban building index have the greatest influence on vertical distribution, and maximum patch index, surface moisture, and net primary productivity have the greatest influence on horizontal distribution. In conclusion, vegetation, landscape, and soil physical properties all have a significant impact on the distribution of soil carbon and nitrogen, suggesting better strategies to improve soil fertility.

Implication of soil carbon changes on the greenhouse gas emissions of pickled ginger: a case study of crop rotation cultivation in Northern Thailand

Implication of soil carbon changes on the greenhouse gas emissions of pickled ginger: a case study of crop rotation cultivation in Northern Thailand

Estimating biomass and soil carbon change at the level of forest stands using repeated forest surveys assisted by airborne laser scanner data

BackgroundUnder the growing pressure to implement mitigation actions, the focus of forest management is shifting from a traditional resource centric view to incorporate more forest ecosystem services objectives such as carbon sequestration. Estimating the above-ground biomass in forests using airborne laser scanning (ALS) is now an operational practice in Northern Europe and is being adopted in many parts of the world. In the boreal forests, however, most of the carbon (85%) is stored in the soil organic (SO) matter. While this very important carbon pool is “invisible” to ALS, it is closely connected and feeds from the growing forest stocks. We propose an integrated methodology to estimate the changes in forest carbon pools at the level of forest stands by combining field measurements and ALS data.ResultsALS-based models of dominant height, mean diameter, and biomass were fitted using the field observations and were used to predict mean tree biophysical properties across the entire study area (50 km2) which was in turn used to estimate the biomass carbon stocks and the litter production that feeds into the soil. For the soil carbon pool estimation, we used the Yasso15 model. The methodology was based on (1) approximating the initial soil carbon stocks using simulations; (2) predicting the annual litter input based on the predicted growing stocks in each cell; (3) predicting the soil carbon dynamics of the annual litter using the Yasso15 soil carbon model. The estimated total carbon change (standard errors in parenthesis) for the entire area was 0.741 (0.14) Mg ha−1 yr−1. The biomass carbon change was 0.405 (0.13) Mg ha−1 yr−1, the litter carbon change (e.g., deadwood and leaves) was 0.346 (0.027) Mg ha−1 yr−1, and the change in SO carbon was − 0.01 (0.003) Mg ha−1 yr−1.ConclusionsOur results show that ALS data can be used indirectly through a chain of models to estimate soil carbon changes in addition to changes in biomass at the primary level of forest management, namely the forest stands. Having control of the errors contributed by each model, the stand-level uncertainty can be estimated under a model-based inferential approach.

Environmental consequences of pig production scenarios using biomass from rotational grass-clover leys as feed

Production of pork based on monoculture cereal-based cropping systems causes substantial environmental pressures and feed-food competition. This study evaluated the environmental consequences of five different scenarios involving inclusion of rotational grass-clover leys and incorporation of grass-clover biomass in pig diets: (1) a conventional reference scenario without grass-clover biomass; (2) a conventional scenario with replacement of feed with grass-clover silage in a total mixed ration, i.e., with grass-clover biomass replacing other feed; (3) an organic scenario using grass-clover silage for enrichment purposes only; (4) an organic scenario using grass-clover silage for enrichment purposes and additional grass-clover leys for green manuring; and (5) an organic scenario using grass-clover silage and pasture to replace feed. The functional unit was 1 kg of pork slaughter weight and the system boundary was from cradle to farm gate. We used life cycle assessment, the introductory carbon balance method and human edible feed conversion efficiency to assess the performance of the pig production system. Introducing grass-clover biomass as a total mixed ration in conventional pig diets, reduced the climate impact (-17%), eutrophication (-7.1%), marine eutrophication (-15%), energy use (-13%), and feed-food competition (-20%) per kg of pork meat, while acidification (+2.7%) and land use (+1.5%) were slightly increased compared with the reference. The lower climate impact (without considering soil carbon change) was attributable to reduced fertilizer and diesel needs due to pre-crop effects. Overall, feeding grass-clover biomass decreased several environmental impact categories, feed-food competition and improved cereal-based cropping systems by the introduction of grass-clover leys.

Patterns and drivers of soil carbon change (1980s-2010s) in the northeastern Qinghai-Tibet Plateau

Rapid climate warming, permafrost degradation and widespread vegetation improvement on the Qinghai-Tibet Plateau (QTP) have caused carbon input via photosynthesis and carbon output through soil respiration to significantly increase in recent decades; thus, its role as a carbon sink/source is unclear and highly disputed, especially at different soil depths. In this study, we took the Qinghai Plateau (northeastern QTP), with an area of 7.2 × 105 km2 (permafrost accounts for 52% of the land) and an elevation ranging from 1669 m to 6548 m, as the study region and estimated its spatial pattern of soil organic carbon (SOC) stock changes at different soil depths from the 1980s to 2010s. The paired site observations of the SOC stocks in the 1980s from the second national soil survey and in the 2010s from a field survey and the literature were compiled and then combined with 77 related environmental factors to drive multiple machine learning models (random forest, gradient-boosting machine, and Cubist), from which the spatial patterns of SOC stock changes at different soil depths (0–30, 30–50, and 50–100 cm) were revealed. The results indicated that the SOC stock increased in the soil at 0–100 cm over the past three decades, with a mean net accumulation rate of 7.36 g C m−2 yr−1 or a total of 0.153 Pg C. Compared with seasonally frozen soil, more significant increases in the SOC stock were observed in permafrost at the 0–100 cm depth (9.71 vs. 4.81 g C m−2 yr−1). However, the SOC stock changes in different soil layers showed significant differences. Specifically, the SOC stock substantially increased in the topsoil layer (0–30 cm), with a carbon increase of 7.82 g C m−2 yr−1; the SOC stock in the middle layer (30–50 cm) had a slight increase, with a carbon increase of 1.69 g C m−2 yr−1; and the SOC stock decreased in the bottom layer (50–100 cm), with a net carbon loss rate of 2.15 g C m−2 yr−1. We found that vegetation change was the key driver of SOC stock change in the topsoil layer. With the increase in soil depth, the importance of climate change on SOC stock change increased. We concluded that climate-driven carbon losses in the deep soil layer were offset by an increase in vegetation-driven carbon inputs at the top and middle soil layers, triggering plant-dominated negative soil carbon feedback to climate warming. With the temperature continuing to increase, however, we must pay more attention to the risk of carbon release in the middle and bottom soil layers.

Refining life cycle nutrient modeling in organic pig production. An analysis focusing on feeding strategies in organic Danish pig farming

Organic pig farming systems are associated with considerable ammonia losses, nitrate leaching in sow pasture concepts, and dependency on imported protein feed components, such as soybean cake. Furthermore, in environmental nutrient modeling approaches, there is a lack of data on emission factors and models that account for nutrient balances concerning organic production systems. Therefore, the present study aimed to analyze feeding strategies in organic pig farming by using refined nutrient modeling approaches.A cradle-to-farm-gate life cycle approach was used to analyze six feeding scenarios: reduced crude protein content in feed rations for sows (S1) and sows and fattening pigs (S3), alternative protein sources and reduced protein in feed rations for sows (S2) and sows and fattening pigs (S4), and reduced compound feed intake for sows (S5) and sows and fattening pigs (S6). Danish average production data were collected and specific data regarding organic production (N content in manure, emission factors for ammonia for the paddock and housing) were identified. Six sub-systems (paddocks with sows and piglets on grass-clover, weaners, fattening pigs, feed, manure, and manufacturing of inputs) were considered and balanced out. Five environmental impact categories, climate change (including soil carbon changes), eutrophication potential, acidification potential, abiotic depletion of fossil fuels, and land occupation, were assessed.It was found that the feeding strategies had considerably higher effects when including both sows and fattening pigs compared to only including sows. The highest reductions for most of the analyzed environmental impacts (13% for eutrophication and acidification, 11% for climate change, and 8% for land occupation) were estimated due to reduced amount of compound feed to both sows and fattening pigs (S6). For abiotic depletion of fossil fuels, a decrease of 33% was determined by the use of locally grown protein sources (S4), which decreased the contribution of transportation. In terms of methodological refinements, an approach for nutrient modeling at the paddock level, where crop rotation and associated effects were also considered, was identified. Furthermore, adapted emission factors for indoor housing with access to outdoor runs were suggested.

Sustainability assessment on paddy-upland crop rotations by carbon, nitrogen and water footprint integrated analysis: A field scale investigation

Nutrients of carbon, nitrogen and water of farmland ecosystem are essential foundation to guarantee crop production, but also environmental flows associated greenhouse gas (GHG), reactive nitrogen (Nr) releases, and water consumption. Their flow characteristics serve as a crucial starting point for creating efficient management practices and mitigation measures. Therefore, the objectives of this study are to quantify the carbon footprint (CF), nitrogen footprint (NF), water footprint (WF), and comprehensive environmental footprint (ComF) of six paddy-upland rotation systems, including fallow-paddy rice (FA-PR), Chinese milk vetch-paddy rice (CMV-PR), wheat-paddy rice (WH-PR), rapeseed-paddy rice (RA-PR), green forage wheat-paddy rice (WF-PR), and vicia faba bean-paddy rice (FB-PR), as well as to analysis their relationships and define driving factors. Results showed that the lowest area-scaled CF of 3.74 t CO2-eq ha−1 were observed in the CMV-PR rotation, which were 41% lower than that for WH-PR (the highest CF, 9.13 t CO2-eq ha−1) when soil carbon change was taken into account. It is of importance that soil carbon sequestration in CMV-PR rotation could offset up to around 57% of its CF, while the WH-PR rotation only offset 25%. The RA-PR rotation had the highest area-scaled NF and WF, which was 1.8 and 1.9 times greater than those of the lowest rotation in FA-PR. In terms of comprehensive environmental effects, the six rotation systems showed the order of FA-PR < CMV-PR < FB-PR < RA-PR < WF-PR < WH-PR, with NH3 volatilization accounting 60.7%–66.7% and blue-green WF for 17.5%–26.6% of the total. Therefore, priority should be given to optimizing N fertilizer application and water consumption for paddy-upland rotation systems. The study also suggested that appropriate inter-annual adjustment of rotation system could contribute to achieving GHG mitigations and Nr losses.

Urbanization associated changes in biogeochemical cycles.

Urbanization associated changes in biogeochemical cycles.

Changes in soil carbon, nitrogen, and phosphorus in Pinus massoniana forest along altitudinal gradients of subtropical karst mountains.

Changes in altitude have a long-term and profound impact on mountain forest ecosystems. However, there have been few reports on changes in soil carbon, nitrogen, and phosphorus contents (SCNPC) along altitudinal gradients in subtropical karst mountain forests, as well as on the factors influencing such changes. We selected five Pinus massoniana forests with an altitudinal gradient in the karst mountain area of Southwest China as research objects and analyzed the changes in SCNPC along the altitudinal gradient, as well as the influencing factors behind these changes. Soil organic carbon, total nitrogen, and available nitrogen contents first increased and then decreased with increasing altitude, whereas the contents of total phosphorus and available phosphorus showed no obvious trend. In the karst mountain P. massoniana forest, SCNPC in the topsoil is most significantly affected by total glomalin-related soil protein (TG) and soil moisture content (SMC) (cumulative explanatory rate was 45.28-77.33%), indicating that TG and SMC are important factors that affect SCNPC in the karst mountain P. massoniana forest. In addition, the main environmental factors that affect SCNPC in the subsoil showed significant differences. These results may provide a better scientific reference for the sustainable management of the subtropical mountain P. massoniana forest.

Effects of Agricultural Waste Application on Soil Carbon Emission in Newly Cultivated Land

Cultivated land is an important resource to ensure food production and food security. However, the low degree of soil ripening, poor soil and lack of organic matter are common problems in newly cultivated land. Fertilization can effectively improve the physical properties of soil, improve soil nutrients and fertility, but long-term application of inorganic fertilizer will cause soil compaction or even degradation. Returning agricultural waste to the field can not only increase soil fertility and effectively improve soil structure, but also change soil carbon emissions. In this paper, the benefits of straw returning and livestock manure composting and their potential effects on soil carbon emissions were summarized to provide ideas for improving the fertility of new cultivated land.

Change in soil carbon, nitrogen, and phosphorus after timber harvesting in northern hardwood forests

AbstractQuantifying changes in soil carbon (C) and nutrient stocks after timber harvesting is needed to inform C management and to ensure that forest productivity is sustained over time. Our objective was to assess changes in soil C, nitrogen (N), and phosphorus (P) 1 year after timber harvesting in temperate northern hardwood forests. We established permanent plots in forest stands for measuring forest attributes before and after harvesting. We collected soils from quantitative soil pits, which were associated with permanent plots, to determine total C, total N, and extractable P stocks and concentrations. Mean post‐harvest fine fraction organic (O) horizon C was less than the pre‐harvest stock, but we did not detect a statistically significant change in total O horizon or mineral soil C stocks. For the fine fractions of the O horizon and mineral soil from the 0–5 and 5–30 cm depth increments of the B horizon, total N and extractable P stocks were positively correlated with total C stocks. For all of these soil components, extractable P stocks and concentrations declined over time, which could be related to post‐harvest stand conditions that favored microbial activity and immobilization of available P. These findings indicate that P availability could be a concern in these forests and that long‐term monitoring is needed to consider potential management actions for ensuring that forest productivity is sustained.

Soil Carbon Dioxide Emission along a Permafrost Hillslope inLarix gmeliniiForest in China

AbstractQuantification of regional soil carbon changes in boreal forests in China is difficult for high spatial heterogeneity, especially considering soil CH4 fluxes in permafrost regions. This study attempted to quantify the variation of soil CO2 emission and its relationship with other soil properties along a permafrost hillslope in Larix gmelinii Kuzen. forest. Using a closed-chamber method, the soil CO2 emission was measured at four slope positions in the Greater Xing’an Range of China in two growing seasons. The results showed that soil CO2 changes have high spatial variability in Larix gmelinii forest along the slope, and average soil CO2 emission at the upper part of the slope was 64% higher than at the bottom. Soil CO2 fluxes showed high positive correlation with soil temperature at 10 cm depth and fungi numbers and negative correlation with soil CH4 change. This study showed the complexity of CO2 emission and could provide data support for forest carbon measurement caused by hillslope in the boreal forest of China.Study Implications: The forest area of Larix gmelinii Kuzen. in the Greater Xing’an Range accounts for 13.2% of the total forest area China. Therefore, the accurate calculation of carbon sequestration of Larix gmelinii forest is significant to the forest carbon measurement of China. However, due to the topographical complexity of the Greater Xing’an Range, the measurement of soil carbon has always been a problem. This study explored the soil carbon dioxide emissions at different slope positions along a hillslope and provided some methods and data support to solve measurement problems caused by hillslope in boreal forest in China.

Soil carbon and nitrogen sequestration and associated influencing factors in a sustainable cultivation system of fruit trees intercropped with cover crops

We comprehensively quantified the influence of cover crops on soil carbon and nitrogen storage in Chinese orchards by a meta-analysis based on the literature published during 1990 to 2020. The factors influencing soil carbon and nitrogen storage were also analyzed. The results showed that compared with clean tillage, soil carbon and nitrogen storage under the cultivation of cover crops considerably increased by 31.1% and 22.8%, respectively. Intercropping legumes enhanced soil organic carbon storage by 4.0% and total nitrogen storage by 3.0% compared with non-legumes. The effect of mulching duration was most prominent at 5-10 years, with 58.5% and 32.8% increases in soil carbon and nitrogen storage, respectively. The largest increase in soil carbon and nitrogen storage (32.3% and 34.1%, respectively) occurred in areas with low initial organic carbon (<10 g·kg-1) and total nitrogen (<1.0 g·kg-1). In addition, suitable mean annual temperature (10-13 ℃) and precipitation (400-800 mm) markedly contributed to soil carbon and nitrogen storage in the middle and lower reaches of the Yellow River. The findings indicated that multiple factors influence the synergistic changes in soil carbon and nitrogen storage in orchards, while intercropping with cover crops is an effective strategy for enhancing soil carbon and nitrogen sequestration.

Uncertain effectiveness of Miscanthus bioenergy expansion for climate change mitigation explored using land surface, agronomic and integrated assessment models

AbstractLarge‐scale bioenergy plays a key role in climate change mitigation scenarios, but its efficacy is uncertain. This study aims to quantify that uncertainty by contrasting the results of three different types of models under the same mitigation scenario (RCP2.6‐SSP2), consistent with a 2°C temperature target. This analysis focuses on a single bioenergy feedstock, Miscanthus × giganteus, and contrasts projections for its yields and environmental effects from an integrated assessment model (IMAGE), a land surface and dynamic global vegetation model tailored to Miscanthus bioenergy (JULES) and a bioenergy crop model (MiscanFor). Under the present climate, JULES, IMAGE and MiscanFor capture the observed magnitude and variability in Miscanthus yields across Europe; yet in the tropics JULES and IMAGE predict high yields, whereas MiscanFor predicts widespread drought‐related diebacks. 2040–2049 projections show there is a rapid scale up of over 200 Mha bioenergy cropping area in the tropics. Resulting biomass yield ranges from 12 (MiscanFor) to 39 (JULES) Gt dry matter over that decade. Change in soil carbon ranges from +0.7 Pg C (MiscanFor) to −2.8 Pg C (JULES), depending on preceding land cover and soil carbon.2090–99 projections show large‐scale biomass energy with carbon capture and storage (BECCS) is projected in Europe. The models agree that &lt;2°C global warming will increase yields in the higher latitudes, but drought stress in the Mediterranean region could produce low yields (MiscanFor), and significant losses of soil carbon (JULES and IMAGE). These results highlight the uncertainty in rapidly scaling‐up biomass energy supply, especially in dry tropical climates and in regions where future climate change could result in drier conditions. This has important policy implications—because prominently used scenarios to limit warming to ‘well below 2°C’ (including the one explored here) depend upon its effectiveness.

Methodological aspects of assessing conservation agriculture efficency

The current research is aimed at working out methodological basis of assessing conservation agriculture efficiency based on the practical experience. The traditional system of land use is now to be totally reconsidered due to its negative environmental effects with new practices to be implemented that can increase productivity, protect soil from degradation and deal with the current climatic crisis, i.e. help adapt to the climate change, decrease greenhouse gas emissions and increase soil carbon sequestration. Conservation agriculture (CA) is the technology that can help overcome all the above mentioned challenges being defined as the approach of managing agricultural ecosystems that provides for the sustainable agricultural production, lower energetic and labor expenses and higher efficiency of utilizing soil and water resources. Given its major goal of preserving soil health conservation agriculture is to be evaluated based on the combination of ecological and economic effects, rather than on the economic effect separately. The current methods of evaluating eco-economic efficiency of the technology based on estimating soil carbon changes and methods of its recovery with adding organic fertilizers cannot be applied in practice now due to the lack of organic fertilizers and high costs of chemical analyses to measure soil carbon changes. The current study presents a new methodology to assess eco-economic effect of conservation agriculture practice based on assessing already adopted economic indicators and soil carbon changes dynamics (t CO2/ha/year) from specific agricultural practices with the subsequent estimation of carbon credit units that farmers can sell at a carbon market.

The Biofuel Course Correction: Refineries that convert biomass to energy are expanding. Attention must be paid to how feedstock crops change soil carbon.

The Biofuel Course Correction: Refineries that convert biomass to energy are expanding. Attention must be paid to how feedstock crops change soil carbon.

Changes in cropland soil carbon through improved management practices in China: A meta-analysis

Recommended management practices (RMPs, e.g., manuring, no-tillage, crop residue return) can increase soil organic carbon (SOC), reduce greenhouse gas emissions, and maintain soil health in croplands. However, there is no consensus on how RMPs affect the SOC storage potential of cropland soils for climate change mitigation. Here, based on 2301 comparisons from 158 peer-reviewed papers, a meta-analysis was conducted to explore management-induced SOC stock changes and their variations under different conditions. The results show that SOC stocks in the 0–20 cm layer were increased by 31.8% when chemical fertilization combined with manure application was compared with no fertilizer; 9.98% when no-tillage was compared with plow tillage; and 10.84% when straw return was compared with removal. The RMPs favorably increased SOC stock in arid areas, and in alkaline and fine-textured soils. Initial SOC, carbon-nitrogen ratio, and experimental duration could also affect SOC storage. Compared with the initial SOC stock, RMPs increased the SOC sequestration potential by 2.6–4.5% in the 0–20 cm soil depth, indicating that these practices can help China achieve targets to increase SOC by 4.0‰. Hence, it is essential to implement RMPs for climate change mitigation and soil fertility improvement.