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Cocoa production is a leading driver of deforestation in the humid-tropics of West Africa. Reconciling climate change mitigation with livelihoods of farmers requires identification of production strategies to concurrently improve yield and profit while curtailing emissions of greenhouse gases (GHG). Using a 2021 plot-survey conducted in Ghana's Eastern region, we evaluated yields, GHG emissions, and value of production (VOP) (a profit indicator) across a typology representing the diversity of systems at plot-level. The typology was constructed by first stratifying plots according to shade levels and variety (hybrid vs. Amazonia) which resulted in three systems: Hybrid sun , hybrid variety under full-sun (little to no shade); Hybrid shade , hybrid and moderate shade (13–25 shade trees ha−1); and Amazonia, Amazonia under predominantly moderate shade. Next, factor analysis and clustering were used to group plots within each system according to cocoa yield, vegetation, management, and (local) climate conditions. Cluster analysis showed that fertiliser, weeding, pruning, hand pollination, cocoa tree density, and shade tree densities of differing heights were most influential for determination across systems. Hybrid shade had the highest net GHG removal rate at −6.8 ± 1.7 (± 95% CI) Mg CO 2 eq ha−1 yr−1: 48% and 127% higher (emissions more negative) respectively over Amazonia and Hybrid sun. Hybrid shade additionally had the highest average and least variable VOP among production systems at 669 ± 564 USD ha−1 yr−1, compared to Hybrid sun and Amazonia at 404 ± 442 and 213 ± 280 USD ha−1 yr−1 respectively. These results point to hybrid cocoa grown under moderate shade of 13–25 shade trees ha−1 as optimal for reconciling climate change mitigation with development in West African cocoa. • Study concurrently evaluates financial profits and GHG balances (N 2 O & CH 4 emissions, CO 2 removals) in West African cocoa. • Plot-level indicators are evaluated across a typology obtained from sample-stratification and clustering. • Hybrid cocoa under moderate shade (13-25 shade trees ha-1) had GHG removal increment of 127% over same variety without shade. • This system too had higher mean profits, thus best reconciling GHG mitigation and economic development for the region. [ABSTRACT FROM AUTHOR]

Enhancing biomass yield simultaneously with soil carbon (C) sequestration is a key aim of climate-smart cropping systems. Perennialization is believed to be a suitable mitigation strategy for climate change with the potential for enhancing soil C stocks. Based on a nine-year field experiment in Denmark, we measured the changes in soil C and nitrogen (N) stocks, biomass yield, and yield stability of three perennial (low-fertilized miscanthus, high-fertilized festulolium, and no N-fertilized grass-legume mixture) and two annual (continuous triticale and maize) cropping systems. We found that the changes in topsoil (0–20 cm) and 0–100 cm soil C stocks and topsoil N stocks varied significantly between cropping systems. Over nine years, topsoil C stocks increased by an average of 1.4 Mg C ha−1 in the three perennial cropping systems, while they decreased by 3.4 Mg C ha−1 in the two annual cropping systems. The 0–100 cm soil C stocks increased by 6.8 Mg C ha−1 in the three perennial cropping systems and increased by 2.3 Mg C ha−1 in the triticale system, but decreased by 2.5 Mg C ha−1 in the maize system. Topsoil N stocks increased by 0.18 Mg N ha−1 in three perennial systems while they decreased by 0.08 Mg N ha−1 in the two annual cropping systems. Changes in 0–100 cm soil N stocks did not differ significantly between cropping systems. Miscanthus, festulolium, and maize showed the highest biomass yield (17.1, 16.7, and 16.4 Mg ha−1 year−1, respectively). There were no significant differences among cropping systems in yield stability. This study demonstrated the potential of perennial cropping systems in obtaining higher soil C stocks compared with annual cropping systems while maintaining high biomass yield, supporting perennialization as a promising option for climate-smart agriculture. • Changes in soil carbon (C) and nitrogen (N) stocks under annual and perennial cropping systems were studied over nine years. • Perennial cropping systems significantly increased topsoil C and N stocks compared to annual cropping systems. • Changes in subsoil C and N stocks did not differ significantly between annual and perennial cropping systems. • There was no significant difference in biomass yield and yield stability between annual and perennial cropping systems. [ABSTRACT FROM AUTHOR]

Policy and market incentives are rapidly expanding to promote soil organic carbon (SOC) sequestration in global croplands. Evidence suggests that long-term increases in SOC can influence both crop yield and nitrogen (N) fertilizer requirements, with the potential to help address two important sustainability challenges. However, increases in SOC may also trigger higher soil nitrous oxide (N 2 O) emissions, which would represent an important tradeoff for climate change mitigation. We tested the hypothesis that long-term increases in SOC are associated with higher crop yields and fertilizer N use efficiency (NUE), but at the cost of higher N 2 O emissions. Wheat was grown in two soils (SOC low and SOC high) under three N fertilizer rates (0, 100, and 200 kg N ha−1) in a mesocosm experiment. Soils were obtained (0–25 cm) from a 22-yr field experiment on no-till and cover cropping in California. Results indicate that total biomass and grain yield were higher for SOC low than SOC high at 100 kg N ha−1 but not the other N levels. Crop N uptake was also 28% greater for SOC low at 200 kg N ha−1, resulting in higher overall NUE. Soil N 2 O emissions increased for SOC high by 25–112% compared to SOC low , likely due to long-term changes in labile C and N pools, microbial activity, and soil structure influencing porosity and gas diffusion. While there are well-documented crop and environmental benefits from enhancing SOC in agricultural soils, results from this study suggest that changes in soil N 2 O emissions should be considered to accurately determine net GHG emission reductions. • Soil N 2 O emissions increased 25–112% with long-term soil carbon sequestration • Crop yields were not higher with increased SOC • Crop nitrogen uptake and nitrogen use efficiency decreased with increased SOC • Elevated N 2 O emissions presented a tradeoff for net GHG emission reductions [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilisation is critical for sugarcane crop production. Consequently, overuse of N fertiliser in sugarcane is widespread and it is most prevalent in China. Yet, a comprehensive analysis of sugarcane N balance accounting for different reactive N (Nr) loss pathways, crop N use and soil N retention using 15N labelled fertilisers under commercial high-input cropping conditions is lacking. A two-year field experiment with 5 N levels (0–560 kg N ha−1; N0, N210, N300, N390, N560) was conducted to quantify the effect of N rate on sugarcane yield, Nr loss through different loss pathways, crop N use and soil N retention, and to identify an optimal N rate that sustain high yield whilst reducing Nr loss in Southern China. The results showed that optimal N rate (N300) had similar yield compared with farmer practice (N560) for the plant crop and the ratoon crop. Nitrogen leaching and ammonia loss were increased significantly with increase in N rate, with farmer practice recording the highest Nr loss. Compared with farmer practice, under optimal N application, N leaching was reduced from 211 kg ha−1 to 107 kg ha−1 and from 244 kg ha−1 to 165 kg ha−1 for the plant and ratoon crops, respectively. The ammonia volatilization from the plant crop and the ratoon crop in the optimal N treatment was 24.8 kg ha−1 and 27.0 kg ha−1, respectively, which are considerably less compared with the emission from the farmer practice. There was no significant difference in nitrous oxide emission between optimal N rate and farmer practice. 15N labelling studies showed that crop N recovery, soil N residue and fertiliser N lost at the optimal N rate were 20.9%, 24.9% and 54.2%, respectively, as opposed to 12.5%, 14.8% and 72.7%. respectively, under farmer practice. To the best of our knowledge, this study forms the first comprehensive evaluation of sugarcane N balance accounting Nr loss, N use and native N soil stock covering a wide range of N supply simultaneously in the plant and ratoon crops under commercial crop production condition. This study thus provides very valuable new knowledge not only for crop N supply optimisation in high-input sugarcane production systems as in China but also for sugarcane greenhouse gas accounting studies particularly from climate change mitigation and bioenergy production context. [Display omitted] • First detailed sugarcane crop N balance (Nr loss, N use, soil N stock) estimated. • Current average sugarcane crop N input in China (560 kg N ha−1) very excessive. • Large reduction in N input and Nr loss without yield loss in multi-year field trials. • Leaching, the single largest N loss pathway in sugarcane crop. • Large crop N recovery, fertiliser N loss reduction with optimal N use (300 kg N ha−1). [ABSTRACT FROM AUTHOR]

This study investigates the impact of alternative fertilization practices on the yield-scaled global warming potential (YS-GWP) in almond orchards. Almond production is a contributor to greenhouse gas emissions, primarily due to nitrogen-based mineral fertilizers. This research aims to identify strategies that reduce the environmental footprint of almond cultivation while maintaining yield. Field experiments were conducted in an almond orchard using three alternative fertigation practices: Advance Grower Practice (AGP), Pump and Fertilize (P&F), and High Frequency Low Concentration (HFLC). AGP is the current practice used by producers to meet annual N demand for almond tree growth; P&F is a reduction in applied N rate in response to measured N concentrations in the groundwater so that the added N and groundwater N reach the same total N applied; HFLC is a practice of applying smaller N rates per individual event. HFLC uses a greater number of fertigation events to reach similar total annual N load as other treatments. Cumulative N 2 O and CH 4 emissions were used to determine GWP by converting the emissions to carbon dioxide equivalents (CO 2 eq) within a 100-year horizon. Nitrous oxide emissions were multiplied by a radiative forcing potential CO 2 eq of 298 and CH 4 by 25 (UNFCCC, 2007). The results revealed that both P&F and HFLC reduced the YS-GWP compared to AGP. HFLC demonstrated 52–78% decrease in GWP per unit of almond yield compared to AGP, while P&F showed 48–58% decrease over AGP. These reductions were attributed to the reduced nitrous oxide emissions associated with P&F and HFLC. Further, P&F and HFLC tended to have higher N use efficiency than AGP. We demonstrate that adopting alternative fertilization practices can effectively mitigate the environmental footprint of almond orchards while maintaining crop yields. These practices offer viable options for almond growers to reduce greenhouse gas emissions, enhance sustainability, and contribute to climate change mitigation. • Applying nitrogen fertilizer at a lower amount and higher frequency reduces nitrous oxide emissions. • This practice tends to have higher nitrogen use efficiency than standard practice. • It maintains commercial yields at the same level as the standard practice. • It lowers Yield Scaled Global Warming Potential more than the standard practice. [ABSTRACT FROM AUTHOR]

The cultivation of deep-rooted vegetation greatly alters the tradeoffs between water and carbon dynamics, yet their impact on microbial carbon sequestration (MCS) remains inadequately documented, particularly in thick vadose zones. This information is crucial for global climate mitigation and ecosystem service enhancement. As such, we collected triplicate samples for each land use type, exploring the abundance and structure of cbbL -harboring microbial communities within 10-m deep profiles under cultivated farmland and two apple orchards of varying ages (n = 72). Our findings indicated a shift from water-dominated (improved water retention at the expense of reduced carbon sequestration) to carbon-dominated benefits (enhanced carbon sequestration at the expense of decreased water retention) in deep soil layers (2–10 m) after the transformation from farmland to apple orchards. Despite the lack of significant differences among the three land use types, the gene abundances and microbial diversity indices reduced with soil depths because of variations in substrates, resources, and microenvironments. The cbbL -harboring microorganisms consisted of 5 phyla, 7 classes, 19 orders, 30 families, and 55 genera, with Proteobacteria as the predominant bacterial phylum. The relative contributions of different genera varied with soil depths, reflecting their distinct survival strategies. The microbial network was positively connected in various soil layers under farmland and apple orchards. Furthermore, the results of correlation, redundancy analysis, and structural equation modeling jointly indicated that plant roots and soil properties, including total nitrogen and organic carbon, governed MCS processes in deep unsaturated zones. Specifically, the low microbial variation between farmland and apple orchards can be attributed to the predominant effects of climatic and pedogenic factors on soil properties, the restricted contribution of plant roots to soil nutrient levels per unit depth, and the adverse effects of plant-induced ecohydrological consequences on root systems and microbial populations. This study offers new insights within thick vadose zones containing deep-rooted plants, thereby contributing to a better understanding of global terrestrial carbon cycle processes. [Display omitted] • Microbial carbon sequestration processes were explored in 10-m deep profiles. • The farmland-to-apple orchards conversion led to water-carbon tradeoffs. • Microbial carbon sequestration differed with depths rather than land use types. • Depth-dependent plant roots and soil nutrients affects carbon sequestration. [ABSTRACT FROM AUTHOR]

Southeast Asia (SEA) is a key producer and exporter of rice, accounting for around 28% of rice produced globally. To effectively mitigate greenhouse gas (GHG) emissions in SEA rice systems, field methane (CH 4) and nitrous oxide (N 2 O) emissions have been intensively studied. However, an integrated assessment of system-level GHG emissions which includes other carbon (C) balance components, such as soil organic carbon (SOC) or energy use, that can positively or negatively influence the net capacity for climate change mitigation is lacking. We conducted a systematic review of published research in SEA rice systems to synthesize findings across four main components of net system emissions: (1) field GHG emissions, (2) energy inputs, (3) residue utilization beyond the field, and (4) SOC change. The objectives were to highlight effective mitigation opportunities and explore cross-component effects to identify tradeoffs and key knowledge gaps. Field GHG emissions were the largest contributor to net system emissions in agreement with existing scientific consensus, with results showing that practices such as floodwater drainage and residue removal are sound options for CH 4 mitigation. On the other hand, increasing SOC potentially provides a large GHG mitigation opportunity, with long-term continuous rice cropping and practices such as residue incorporation and biochar application promoting SOC increase. A reduction in energy inputs was mainly achieved by optimizing agrochemical use, especially N fertilizers. For residue utilization beyond the field, GHG emission mitigation mainly came from preventing open field burning through residue removal. Removed residue can subsequently be used for producing energy that offsets GHG emissions associated with conventional fuel sources (e.g. fossil fuel-based electricity generation) or substituting material used in other production systems. Integrating all four components of net system emissions into one analysis underscores the following two main takeaways. First, the components of field GHG emissions and SOC change are the biggest opportunities for reducing net system emissions and need to be considered for effective climate change mitigation. Second, the reduction of C inputs through residue removal and increased soil aeration through multiple drainage will lower CH 4 emissions but may also potentially decrease SOC stocks over time. Hence, we argue that future research needs to consider cross-component effects to optimize net system emissions, specifically the "stacking" of best management practices for mitigation related to field GHG emissions or SOC change in long-term experiments. • Net system emissions include field CH 4 /N 2 O emissions, energy inputs, residue utilization, and SOC change. • Integrated review highlights cross-component effects of management including tradeoffs. • Field GHG emissions and SOC change are the largest opportunities for mitigation. • Reduced C inputs and drainage decrease CH 4 emissions, but may negatively affect SOC. • "Stacking" of best management practices is a key knowledge gap that warrants research. [ABSTRACT FROM AUTHOR]

Green manure is a widely applied to increase grain yield, while it also attributes to greenhouse gas (GHG) emissions in agriculture ecosystems. Combining green manure with inorganic fertilizer inputs is a common practice that can influence soil GHG emissions and grain yield, however, its impacts on grain yield and global warming potential (GWP) under different initial soil conditions before rotating experiments and agronomic management in paddy fields remain unclear. We synthesized 508 data pairs to evaluate the responses of CO 2 emissions, CH 4 emissions, N 2 O emissions, and grain yield to combined inputs of green manure plus inorganic fertilizer compared with only inorganic fertilizer application. Our findings indicate that both inorganic fertilizer plus extra green manure (GM-E) and green manure substitutes for inorganic fertilizer (GM-S) could increase CO 2 emissions (22.5 %−76.8 %), CH 4 emissions (100 %−103 %), N 2 O emissions (29.8 %−50.9 %), and yield (2.21 %−19.6 %). Except for GM-E, which showed a non-significant increase in grain yield. The initial soil properties before rotating experiments, the types and timing of green manure application were key drivers of GHG emissions and yield, and extra green manure applied in areas with low initial soil pH and high C:N can increase GWP and yield. Overall, the mixed green manure application had greater impact than leguminous or non-leguminous green manure applied alone. The responses of GHG emissions and yield to GM-S were modulated by mean annual precipitation and initial soil properties before rotating experiments, and green manure substitutes for inorganic fertilizer in areas with high initial soil pH and low C:N can increase GWP and yield. Meanwhile, excessive precipitation caused a reduction in yield and a significant increase in GWP intensity. Our results showed that extra green manure applications of less than 68.1 kg N ha−1 would not significantly increase GWP. Therefore, an effective green manure strategy can achieve a win-win situation for the dual challenge of agricultural production and climate change mitigation. • Green manure inputs significantly increased GHG emissions from paddy fields. • Green manure combined inorganic fertilizer may not increase the yield significantly. • Mixed green manure had greater impact than single-type green manure application. • Green manure substitutes for inorganic fertilizer may not increase the GWPI. • Extra green manure (<68.1 kg N ha-1) is recommended to achieve a win-win situation. [ABSTRACT FROM AUTHOR]

Cover crops are widely advocated for increasing soil organic carbon (SOC) levels, thereby benefiting soil health improvement and climate change mitigation. Few regional-scale studies have robustly explored SOC stocks under cover cropping, due to limited long-term experiments. We used the unique experimental data from the North American Project to Evaluate Soil Health Measurements conducted in 2019 to address this issue. This study included 19 agricultural research sites with 36 pairs of cover cropping established between 1896 and 2014. Explanatory variables related to site-specific environmental conditions and management practices were collected to identify and prioritize contributing factors that affect SOC stocks with cover crops, by coupling the Boruta algorithm and structural equation modeling. Overall, cover crops significantly (P < 0.05) improved several indicators of soil health, including greater SOC (concentration: +8%; stock: +7%), total nitrogen (+8%), water-stable aggregates (+15%), and potential carbon mineralization (+34%), on average, compared to no cover crop control. Likewise, on average, cover crops sequestered SOC 3.55 Mg C ha-1 (0–15 cm depth), with a sequestration rate of 0.24 Mg C ha-1 yr-1. In addition, we found climate (Hargreaves climatic moisture deficit) was important in explaining the variation of SOC stocks with cover crops, followed by soil properties (e.g., soil clay content). In terms of management practices, cover crop type had a significant positive (0.36) effect on SOC stocks, with non-legumes showing a greater impact, compared to legumes and mixtures. Crop rotational diversity also had a positive (0.28) effect on SOC accumulation. Our findings suggested that integrating non-legume cover crops into diverse crop rotation is likely to be a promising strategy to maximize SOC stocks with cover crops across North America. • Prioritized factors affecting soil organic carbon stocks under cover cropping. • Investigated 19 long-term experiments with cover crops in North America. • Used models coupling the Boruta algorithm and structural equation modeling. • Descending from climate > cover crop type > soil clay content > rotation > tillage. • Cover crops sequestrated carbon 3.55 Mg C ha-1, at a rate of 0.24 Mg C ha-1yr-1. [ABSTRACT FROM AUTHOR]

Cover crops may improve soil health and increase soil carbon sequestration, thus contributing to both the adaptation to and mitigation of climate change. Despite these potential benefits, there currently lacks a global synthesis of the impacts of cover crops on soil organic carbon (SOC) fractions. We conducted a global meta-analysis of 93 peer-reviewed studies to quantify the effect of cover crops on changes in SOC fractions and the influence of environmental and management factors. Compared to bare soil management, cover crops increased SOC by 12% and increased seven SOC fractions, including microbial biomass carbon (MBC) by 33%, dissolved organic carbon (DOC) by 18%, particulate organic carbon (POC) by 15%, light-fraction organic carbon (LFOC) by 14%, permanganate oxidizable carbon (POXC) by 13%, short-term mineralizable carbon (SMC) by 10%, and mineral-associated organic carbon (MAOC) by 7%. The effect size of SOC was positively correlated with the effect sizes of MBC, POC, LFOC, and MAOC, but negatively correlated with the effect size of DOC. Soil taxonomic order and experimental duration were key factors affecting the beneficial effect of cover crops on the SOC fractions. Greater increases in SOC fractions due to cover crops were found in Entisols and Ultisols in comparison with other soil orders. The effect size of MAOC increased with experimental duration. Our study suggests that cover crops can significantly increase various SOC fractions, which likely serves as a building block for SOC sequestration and improvement of many aspects of soil health. [Display omitted] • Cover crops increased SOC fractions by 7–33%. • Mineral-associated organic carbon was least responsive to cover crops. • Microbial biomass carbon was most responsive to cover crops. • Soil order and time most strongly modulated SOC fraction responses to cover crops. • Mineral-associated organic carbon responds to cover crops over longer durations. [ABSTRACT FROM AUTHOR]

Scattered trees in wood-pastures represent outstanding conservation value by providing microhabitats for a variety of organisms. They also diversify ecosystem services by creating shade for livestock, and capturing and storing carbon. However, trees in wood-pastures are declining Europe-wide and an appropriate legal environment to maintain them is mostly lacking. Here we looked beyond the well-documented beneficial effects of trees and assessed potential ecosystem disservices, which may drive the controversial appreciation of trees. In a grazing exclusion experiment, we assessed the effect of trees on herbage production in wood-pastures from semi-arid continental to humid montane areas in the temperate deciduous forest ecoregion, and found that trees have a suppressive effect throughout the year, although herbage nutritive value, as indicated by herbage nitrogen content, seems to be improved in spring. When we up-scaled the local ecosystem disservice on herbage yield to entire wood-pastures, the loss remained below 3%, which is lower than reported gains in livestock production due to free access to shade. Thus, the motivation for the under-appreciation of trees by land managers and decision makers may lie in that trees suppress herbage production, but the importance of this effects is offset by the magnitude of the beneficial services of trees. We recommend current wood-pasture stakeholders to revisit their attitude towards scattered trees and encourage tree planting campaigns and tree-based climate mitigation strategies to consider the protection of trees in wood-pastures and the establishment of young ones in currently open pastures up to traditionally low tree cover proportions, as livestock production is unlikely to be compromised by this action. • Wood-pastures are widespread, high nature and cultural value landscapes. • Scattered trees in wood-pastures boost biodiversity and diversify ecosystem services. • In temperate deciduous forest ecoregions, they reduce sub-canopy biomass production. • When scaled up to the whole wood-pasture, the loss of biomass remains negligible. • Climate strategies are encouraged to involve scattered trees on pastureland. [ABSTRACT FROM AUTHOR]

Highlights • No-till could reduce GHGs emissions and increase crop yields in dry climates. • No-till substantially decreased the global warming potential (GWP) of acid soils. • No-till enhanced barley yield by approximately 49%. • No-till reduced GWP in rice fields by suppressing CO 2 (22%) and CH 4 (22%) emissions. Abstract No-tillage (NT) has been touted as one of several climate-smart agriculture (CSA) management practices that improve food security and enhance agroecosystem resilience to climate change. However, the sustainable effectiveness of NT greatly depends on trade-offs between NT-induced changes in crop yield and greenhouse gas (GHG, i.e. CH 4 , CO 2 , and N 2 O) emissions. Such trade-offs are regulated by climate fluctuations and heterogeneous soil conditions and have not been well addressed. Supporting CSA management decisions requires advancing our understanding of how NT affects crop yield and GHG emissions in different agroecological regions. In this study, a meta-analysis was conducted using 740 paired measurements from 90 peer-reviewed articles to assess the effects of NT on crop yield, GHG emissions, and the global warming potential (GWP) of major cereal cropping systems. Compared to conventional tillage (CT), NT reduced in GHG emissions and increased crop yield in dry, but not humid, climates, and reduced in the GWP at sites with acidic soils. Across different cropping systems, NT enhanced barley yield by 49%, particularly in dry climates, and it decreased the GWP of rice fields through a 22% reduction in both CO 2 and CH 4 emissions. Our synthesis suggests that NT is an effective CSA management practice because of its potential for climate change mitigation and crop yield improvement. However, the net effect of NT (relative to CT) was influenced by several environmental and agronomic factors (climatic conditions, tillage duration, soil texture, pH, crop species). Therefore, agroecological setting must be taken into consideration when conducting a comparative evaluation of different tillage practices. [ABSTRACT FROM AUTHOR]

Highlights • Thirty years of conservation management resulted in large SOC storage in the soil profile (0–100 cm). • Greatest increase in SOC was with no-till combined with legume cover crops and N fertilization. • Rate of SOC storage was high in surface (0–30 cm) layers but decreased over time. • Subsoil (30–100 cm) contributed to half of the additional SOC storage. • Management-induced changes in SOC stocks were largely explained by plant C input. Abstract The effect of no-tillage (NT) on soil organic carbon (SOC) storage may help Brazil meet its 37% greenhouse gas emissions reduction target by 2025. When combined with legume cover crops, NT could result in even greater SOC storage than NT alone. The objective of this study was to evaluate the SOC storage potential of NT and the contribution of legume cover crops and nitrogen (N) fertilization to this potential in both the surface and subsurface soil layers of a previously degraded subtropical Acrisol of Southern Brazil. Using a split-plot design, the long-term field experiment compared the effect of NT and conventional tillage (CT), with or without legume cover crops, and with or without mineral N fertilization. Thirty years of contrasting management systems resulted in large differences (up to 35 Mg ha−1) in SOC stocks in the whole soil profile (0–100 cm). The combination that provided the greatest increase in SOC was NT combined with two legume cover crops and N fertilization (1.15 Mg ha−1 year−1 compared to CT, with no N fertilization or legume cover crop). Legume cover crops were twice as efficient in storing SOC as N fertilization, with 1 kg of residue input being converted to 0.15 kg of SOC. Overall, the variation in SOC stocks was explained largely by plant carbon input (R2 = 80%) which varied with N fertilization and cropping system. About half of the SOC storage that occurred in this 30-year-old NT system was attributable to the increase in SOC stocks in the subsurface layer (30–100 cm), which was confirmed by the contribution of C 3 cover crop residues using carbon isotope signature (from 14.8 to ∼17.5‰ in the 75–100 cm layer). Thus, the legume cover crop made a strong contribution to the potential of SOC storage in NT, and high rates of C storage occurred over a longer period in subsurface soil layers than previously believed. [ABSTRACT FROM AUTHOR]

Increasing demand for food and the shortage of arable land call for sustainable intensification of farming, especially in Sub-Saharan Africa where food insecurity is still a major concern. Kenya needs to intensify its dairy production to meet the increasing demand for milk. At the same time, the country has set national climate mitigation targets and has to implement land use practices that reduce greenhouse gas (GHG) emissions from both agriculture and forests. This study analysed for the first time the drivers of forest disturbance and their relationship with dairy intensification across the largest montane forest of Kenya. To achieve this, a forest disturbance detection approach was applied by using Landsat time series and empirical data from forest disturbance surveys. Farm indicators and farm types derived from a household survey were used to test the effects of dairy intensification on forest disturbance for different farm neighbourhood sizes (r = 2–5 km). About 18% of the forest area was disturbed over the period 2010–2016. Livestock grazing and firewood extraction were the dominant drivers of forest disturbance at 75% of the forest disturbance spots sampled. Higher on-farm cattle stocking rates and firewood collection were associated with 1–10% increased risk of forest disturbance across farm neighbourhood sizes. In contrast, higher milk yields, increased supplementation with concentrated feeds and more farm area allocated to fodder production were associated with 1–7 % reduced risk of forest disturbance across farm neighbourhood sizes. More intensified farms had a significantly lower impact on forest disturbance than small and resource-poor farms, and large and inefficient farms. Our results show that intensification of smallholder dairy farming leads to both farm efficiency gains and reduced forest disturbance. These results can inform agriculture and forest mitigation policies which target options to reduce GHG emission intensities and the risk of carbon leakage. [ABSTRACT FROM AUTHOR]

The ongoing introduction of the exotic Grevillea robusta tree species into agroforestry systems (AFS) of the Indian Western Ghats could become a threat to both climate change mitigation and tree diversity conservation. Here, we quantified carbon (C) storage and shade tree diversity in native forests and coffee AFS under contrasted management (native versus exotic shade trees, Robusta versus Arabica systems) at 67 plots along a 3500 mm precipitation gradient in the Cauvery watershed, India. Despite a substantial reduction of shade tree cover in native AFS compared to forest (from 90% to 32% in the high precipitation area), native AFS and forests displayed high and comparable C stocks (max. 228 MgC ha −1 and 234 MgC ha -1, respectively) and tree diversity (max. 44 and 45 species, respectively). Both variables were negatively impacted by the introduction of G. robusta , especially in Robusta coffee systems (max. 158 MgC ha −1 , 12 species). The current trend toward the introduction of G. robusta in coffee AFS of the study area (exotic agroforestry) negatively affects C storage and tree diversity, especially in Robusta coffee systems. Policy makers should take advantage of the carbon-tree diversity positive correlation found in the agroforestry landscape of the Western Ghats of India to promote conservation and climate change mitigation. [ABSTRACT FROM AUTHOR]

Policymakers and businesses in Southeast Asia are increasingly interested in using carbon markets to encourage adoption of regenerative agriculture practices by farmers. These practices are thought to mitigate climate change by reducing soil carbon loss and enhancing soil carbon sequestration. However, there is uncertainty in the ability of regenerative agriculture practices to increase soil organic carbon (SOC) stocks of croplands. We reviewed 92 empirical studies that investigated the effects of 17 regenerative farming practices across 11 broad categories of crops on SOC stock or content in Southeast Asia. Our synthesis found supporting evidence for the use of organic amendments like biochar, compost, and manure, as well as cover cropping, crop rotation, and conservation tillage to increase SOC. However, studies for practices like addition of compost and manure reported increases in greenhouse gas emissions like methane (CH 4) and nitrous oxide (N 2 O), demonstrating that increases in SOC may be offset by increases in greenhouse gas emissions. Only a few studies measured both the changes in SOC stocks and greenhouse gas emissions and none of the studies completed full greenhouse gas inventories. Estimating the net impact of SOC gains and increase of greenhouse gas emissions will be necessary to understand the overall effect of practices like compost, manure and crop residue incorporation on net atmospheric greenhouse gas concentrations. If these practices are implemented for soil carbon projects, practitioners should anticipate increases in greenhouse gas emissions from soils and implement additional practices, such as alternate wetting and drying, to optimize the climate change mitigation effects of regenerative agriculture. We encourage future research on practices, such as agroforestry and changes in crop residue management, where there are few studies and little variation in experimental design and environmental conditions. Given the interest in scaling up regenerative agriculture through voluntary carbon markets to boost SOC stocks in croplands, policymakers and businesses can support research in this area by making field-collected data from their projects accessible to researchers to further the study of the impact of these practices across different abiotic conditions and soil managements. This data sharing would alleviate the paucity and improve the quality of empirical data on regenerative agricultural practices in Southeast Asian croplands, facilitate practice-specific meta-analyses, and help to optimize climate change mitigation effects of regenerative agriculture. • Regenerative agriculture practices can increase soil carbon in Southeast Asia. • These practices can also increase cropland greenhouse gas emissions like methane. • More empirical data is needed to quantify the practices' effects on soil carbon [ABSTRACT FROM AUTHOR]

Cover crops can contribute to climate change mitigation through enhanced sequestration of atmospheric carbon dioxide into soil organic carbon. Few studies, however, have estimated the total carbon (C) input to soil, i.e. derived both from plant material (shoot and root) and phyllo- and rhizodeposition. Selection of cover crop species should account for multiple objectives, such as C inputs to soil, nitrate leaching reduction and positive residual effects on the following main crop. However, trade-offs between these objectives may occur. The aim of this study was to investigate the performance of the cover crop species winter rye, hairy vetch and oilseed radish, and to assess the ability of mixtures to overcome potential trade-offs. A randomized split-plot field trial was conducted to compare cover crop treatments and a weeded control under high and low soil nitrogen (N) availability. Multiple-pulse labeling with 14C-CO 2 was carried out to trace net cover crop-derived rhizodeposition C. Soil mineral N was measured to 1.5 m depth in autumn, as well as grain and N yield in the subsequent spring barley. Cover crop species accumulated between 1250 and 2580 kg C ha−1, with significantly higher total C input (in shoot, root and phyllo- and rhizodeposits) for the mixtures compared with pure stands of either vetch or radish, while the results for rye were in between. The quantity of C lost via phyllo- and rhizodeposition (qClvPR) showed a significant positive correlation with root C and was highest for the mixtures and rye. The relative ClvPR ranged between 7% and 14% of total cover crop-derived C and tended to decrease under higher soil N availability. All cover crop treatments were able to decrease soil mineral N (0–1.5 m), with radish displaying the highest N leaching reduction potential. Despite substantial differences in cover crop total N uptake and C:N ratios, no significant differences were observed in the subsequent main crop grain or N yields. The mixtures showed the highest total C input and generally a higher or similar mineral N depletion potential than the average of the pure stands, suggesting that cover crop mixtures offer a realistic means for overcoming trade-offs among ecosystem functions. • Winter rye and cover crop (CC) mixtures produced highest total and rhizodeposition C. • Root C was the strongest predictor of rhizodeposition C. • Oilseed radish depleted soil mineral N better than winter rye and hairy vetch. • CC mixtures depleted soil mineral N as well or better than the pure stand average. • Despite dissimilar CC quantity and quality, no crop yield effect of CCs was observed. [ABSTRACT FROM AUTHOR]

Agriculture is a global contributor to greenhouse gas emissions, causing climate change. Soil organic carbon (SOC) sequestration is seen as a pathway to climate change mitigation. But, long-term data on the actual contribution of tropical soils to SOC sequestration are largely absent. To contribute to filling this knowledge gap, we measured SOC in the top 15 cm over 12 years in two agronomic long-term trials in Western Kenya. These trials include various levels – from absence to full adoption – of two widely promoted sustainable agricultural management practices: Integrated Soil Fertility Management (ISFM; i.e. improved varieties, mineral fertilizer and organic matter/manure incorporation) and Conservation Agriculture (CA; improved varieties, mineral fertilizer, zero-tillage and crop residues retention). None of the tested ISFM and CA treatments turned out successful in sequestering SOC long-term. Instead, SOC decreased significantly over time in the vast majority of treatments. Expressed as annual averages, losses ranged between 0.11 and 0.37 t C ha −1 yr −1 in the CA long-term trial and 0.21 and 0.96 t C ha −1 yr −1 in the ISFM long-term trial. Long-term application of mineral N and P fertilizer did not mitigate SOC losses in both trials. Adopting zero-tillage and residue retention alone (as part of CA) could avoid SOC losses of on average 0.13 t C ha −1 yr −1 , while this was 0.26 t C ha −1 yr −1 in response to mere inclusion of manure as part of ISFM. However, cross-site comparison disclosed that initial SOC levels of the two trials were different, probably as a result of varying land use history. Such initial soil status was responsible for the bulk of the SOC losses and less so the various tested agronomic management practices. This means, while ISFM and CA in the humid tropical agro-ecosystem of Western Kenya contribute to climate change mitigation by reducing SOC losses, they do not help offsetting anthropogenic greenhouse gas emissions elsewhere. [ABSTRACT FROM AUTHOR]

The concept of Climate-Smart Agriculture (CSA) has consistently been positioned between science and policy. CSA has given rise to a lively debate in both the scientific community and civil society although it addresses the pressing need for an efficient strategy to manage agriculture and food systems facing climate change (CC). CSA formally targets the simultaneous fulfilment of three criteria: (i) CC mitigation, (ii) adaptation to CC and (iii) food security. Yet, the review of scientific literature on CSA displays a clear discrepancy between these three objectives, underlining the fact that CSA is regularly perceived as addressing only adaptation, and not mitigation and food security. On the other hand, research on agroecology (AE) reveals an extensive knowledge about food security and adaptation, often at scales which can be considered complementary to those of CSA. A better use by CSA of AE research results may help CSA focus on two currently overlooked dimensions, i.e. (i) mitigation and (ii) trade-offs and synergies between the three criteria. CSA does not have a specific blueprint for climate-smart practices and has rather a strong focus on policies, institutions and financing. Hence AE actually responds to the needs of CSA in terms of site-specificity and potential for adoption by farmers because it is strongly based on local practices. We argue that an eco- and socio-logical approach to CSA represents a sine qua non condition if CSA is to promote inclusive development and participate to collective efforts to manage agriculture and food systems under climate change. [ABSTRACT FROM AUTHOR]

Switchgrass ( Panicum virgatum L.) is widely selected as a model feedstock for sustainable replacement of fossil fuels and climate change mitigation. However, how climate changes, such as altered precipitation (PPT), will influence switchgrass growth and soil carbon storage potential have not been well investigated. We conducted a two-year PPT manipulation experiment with five treatments: −50%, −33%, +0%, +33%, and +50% of ambient PPT, in an “Alamo” switchgrass field in Nashville, TN. Switchgrass aboveground net primary production (ANPP), leaf gas exchange, and soil respiration (SR) were determined each growing season. Data collected from this study was then used to test whether switchgrass ANPP responds to PPT changes in a double asymmetry pattern as framed by Knapp et al. (2017), and whether it is held true for other ecosystem processes such as SR. Results showed that the wet (+33%, and +50%) treatments had little effects on ANPP and leaf gas exchange compared to the ambient precipitation treatment, regardless of fertilization or not. The −33% treatment did not change ANPP and leaf photosynthesis, but significantly decreased transpiration and enhanced water use efficiency (WUE). Only the −50% treatment significantly decreased ANPP and LAI, without changing leaf photosynthesis. SR generally decreased under the drought treatments and increased under the wet treatments, while there was no significant difference between the two drought treatments or between the two wet treatments. Our results demonstrate that switchgrass ANPP responded in a single negative asymmetry model to PPT changes probably due to relative high PPT in the region. However, even in such a mesic ecosystem, SR responded strongly to PPT changes in an “S” curve model, suggesting that future climate changes may have greater but more complex effects on switchgrass belowground than aboveground processes. The contrasting models for switchgrass ANPP and SR in response to PPT indicate that extreme wet or dry PPT conditions may shift ecosystem from carbon accumulation toward debt, and in turn provide government and policy makers with useful information for sustainable management of switchgrass. [ABSTRACT FROM AUTHOR]

Improved soil management in rainfed Mediterranean agroecosystems can be a powerful strategy to mitigate the current atmospheric CO 2 increase, through soil carbon sequestration and stabilization. In this work, we assess the effects of different soil management practices (conventional tillage, CT, reduced tillage, RT, reduced tillage plus green manure, RTG, and no tillage, NT) on soil CO 2 flux dynamics and carbon sequestration in two organic rainfed almond ( Prunus dulcis Mill.) orchards under semiarid conditions. Soil CO 2 flux, temperature, and moisture were measured monthly over two-three years, and shortly after tillage operations. The soil aggregation distribution (including micro-aggregates occluded within macro-aggregates) and associated organic carbon content were measured after four years of implementation. No significant differences in CO 2 emissions among the soils subjected to the distinct management practices were observed at either site. On the one hand, shifting from CT to RT or RTG increased the OC content by 56% on average in all aggregate sizes. On the other hand, suppressing tillage only increased the OC content (by 24%) in the macro-aggregates. Moreover, improved soil management practices modulated the response of soil CO 2 flux to temperature and moisture in these semiarid Mediterranean agroecosystems. According to our results, soil CO 2 flux under the conventional tillage treatment was more sensitive to temperature increments than with the reduced tillage treatments, indicating that bare soils will be more vulnerable to organic carbon mineralization with ongoing global warming. On the contrary, the incorporation of plant residues under the reduced tillage treatments promoted soil aggregation and organic carbon preservation, making soils more resilient to abrupt changes in temperature and moisture under these treatments. [ABSTRACT FROM AUTHOR]

Pastoral farming systems have always adapted to the seasonal availability of forage resources and climate variability by moving animals. However, the role of animal mobility as a possible mitigating strategy in response to climate change has not been clearly documented. To understand this role, we investigated (i) the major methodological challenges linked to the diversity of grazing areas and other forage resources exploited by these systems and enteric emissions of methane; (ii) the impacts of grazing practices (carbon sequestration/emission) on soil and biomass carbon fluxes. We developed an approach based on two existing models (OSTRAL: Outil de Simulation du TRoupeau ovin ALlaitant and CASA: Carnegie Ames Stanford Approach) that we adapted and used in combination. This approach was applied to three French Mediterranean sheep and crop farming systems with different degrees of flock mobility (sedentary, single transhumance and double transhumance). The preliminary results produced by the whole farm model OSTRAL showed that two systems (sedentary and double transhumance) causing low carbon emissions. In the sedentary system, higher animal productivity offsets the increase in GHG emissions (in CO 2 eq) caused by feed production. In the pastoral system, grazing reduced total GHG emissions (in CO 2 eq). The CASA model proved to be useful to simulate the carbon balance under dynamic land cover in natural environments, whether used for grazing or not. This model can help assess the impact of grazing practices and carbon fluxes in systems linked to natural environments. The results of the first application showed that seasonal mobility of livestock increases the contribution of rangeland to feeding systems and improves the non-renewable energy balance of the system. It is thus extremely important to include the specificities of animals grazing in rangelands outside the structural limits of the farm when evaluating GHG emissions. [ABSTRACT FROM AUTHOR]

Livestock is both threatened by and contributing to climate change. The contribution of livestock to climate change and greenhouse gas (GHG) emission greatly vary under different management regimes. A number of mitigation options comprise livestock management, although there are a lot of uncertainties as to which management regime to use for a given pedoclimatic and farming system. Therefore, we 1) tested if an extensive cattle livestock farm is a net sink or a net source for GHG (carbon–dioxide, CO 2 ; methane, CH 4 ; nitrous oxide N 2 O) in Central–Eastern Europe, 2) compared the annual GHG balances between the grazed and mowed treatments of the farm 3) and investigated the role of climate variability in shaping these balances. Net ecosystem exchange of CO 2 ( NEE ) was measured with eddy covariance technique in both the grazed and mowed treatments. Estimations of lateral C fluxes were based on management data. Other GHG fluxes (CH 4 , N 2 O) were determined by chamber gas flux measurements technique (in case of soil) and IPCC guidelines (in case of manure decomposition and animal fermentation). Net greenhouse gas balance ( NGHG ) for the grazed treatment was 228 ± 283 g CO 2 equivalent m −2 year −1 (net sink) and −475 ± 144 g CO 2 equiv. m −2 year −1 (net source) for the mowed treatment. Net source activity at the mowed treatment was due to its higher herbage use intensity compared to the grazed treatment. At the farm scale the system was estimated to be a net sink for NGHG in a year with wet (135 g CO 2 equiv. m −2 year −1 ), while a net source in years with dry soil moisture conditions (−267 ± 214 g CO 2 equiv. m −2 year −1 ). We conclude that under a temperate continental climate extended extensive grazing could serve as a potential mitigation of GHG in contrast to mowing. Our study highlights the fact that livestock farming could create a net sink for GHG under proper management regimes. [ABSTRACT FROM AUTHOR]

Cattle production is characterized by high land requirements, and greenhouse gas (GHG) emissions associated with the resulting land use change (LUC) and cradle to farm gate processes. Intensification of cattle production systems is considered an important strategy for mitigating anthropogenic GHG emissions. When categorizing production practices into three systems, i.e. pasture-based, mixed and industrial systems, intensification can either take place within one system or through the transition to another more productive system. This study investigates the impacts of these two pathways on farm gate emissions and LUC-related emissions (expressed in kg CO 2 -eq per kg of milk or beef) in nine world regions. First, a review is conducted of bottom-up studies on farm gate emissions (without LUC) from dairy production in Europe and beef production in North America and Brazil. Then, a global data set on GHG emissions from cattle production is used to discuss the GHG emission impacts of the two development pathways in other regions. Finally, the GLOBIOM model is applied to perform a global assessment of land occupation and LUC-related emissions. For dairy in Europe, farm gate emission reductions of 1%–14% are found for intensification within one system and 2%–26% for system transitions. In Europe as well as other developed regions, the comparative influence of both pathways on the GHG balance largely depends on the specific design of the initial and final production systems. In developing countries especially, there is a greater potential for emission reductions through intensification within the pasture-based system. The additional reduction potential of moving from pasture-based to mixed and industrial production is limited. Also, emission reductions of intensification within the mixed system are smaller compared to the pasture-based system. For beef production in Brazil, intensification within pasture-based systems can attain significant farm gate emission reductions (>50%). The same is true for pasture-based systems in other developing regions and also some developed regions. Furthermore, the additional GHG reduction potentials of moving from pasture-based to mixed systems, and of intensification within mixed systems are larger for beef than for dairy. Although both the dairy and beef sector can often attain significant farm gate emission reductions through intensification within pasture-based systems, the transition to mixed systems is important to reduce land occupation and LUC-related emissions. LUC mitigation is considered to be the most important GHG mitigation strategy for cattle production in Sub-Saharan Africa and Latin America. Important, but technically and economically constrained strategies to reduce both farm gate and LUC-related emissions include increasing the productivity of grassland and cropland, and increasing the animal productivity through improved feed quality. [ABSTRACT FROM AUTHOR]

Agriculture is a major source of greenhouse gas (GHG) emissions globally. The growing global population is putting pressure on agricultural production systems that aim to secure food production while minimising GHG emissions. In this study, the GHG emissions associated with the production of major food commodities in India are calculated using the Cool Farm Tool. GHG emissions, based on farm management for major crops (including cereals like wheat and rice, pulses, potatoes, fruits and vegetables) and livestock-based products (milk, eggs, chicken and mutton meat), are quantified and compared. Livestock and rice production were found to be the main sources of GHG emissions in Indian agriculture with a country average of 5.65 kg CO 2 eq kg −1 rice, 45.54 kg CO 2 eq kg −1 mutton meat and 2.4 kg CO 2 eq kg −1 milk. Production of cereals (except rice), fruits and vegetables in India emits comparatively less GHGs with <1 kg CO 2 eq kg −1 product. These findings suggest that a shift towards dietary patterns with greater consumption of animal source foods could greatly increase GHG emissions from Indian agriculture. A range of mitigation options are available that could reduce emissions from current levels and may be compatible with increased future food production and consumption demands in India. [ABSTRACT FROM AUTHOR]

No-till (NT) has been widely regarded as a potential option to enhance soil organic carbon (SOC) sequestration and thus mitigate climate change. However, recent studies have shown that previous estimates of SOC storage under NT seem to be overestimated due to shallow sampling and improper SOC accounting. In China, the overall trend and magnitude of changes in SOC storage in response to NT adoption remain inconclusive. Here we use a meta-analysis to assess the relative change in SOC storage (profiles ≥20 cm) based on 95 comparisons between NT and conventional tillage (CT) from 57 experimental sites (≥3 years) covering various cropping systems, soil types, and climatic regions of China. The results revealed that compared to CT, adopting NT led to SOC accumulation in the upper 20 cm layer and SOC depletion in the 30–40 cm layer. On average, NT improved SOC stocks over CT by 3.8% [95% confidence interval (CI): 1.4%–6.3%; P = 0.005] and 5.1% (95%CI: 2.5%–7.7%; P < 0.001) as represented by the equivalent soil mass (ESM) and fixed-depth (FD) approaches, respectively. The relative change in SOC storage rate under NT over tilled soil for the top 30 cm layer was therefore significantly higher ( Mean : 0.300 Mg ha −1 yr −1 , 95%CI: 0.054–0.547; P < 0.001) calculated by FD approach than that by ESM ( Mean : 0.141 Mg ha −1 yr −1 , 95%CI: −0.102–0.384; P = 0.100). Further analysis suggested that the effect of NT on SOC storage was significant with residue retained‎, double cropping systems, and in the coarse textured soils. We conclude that although NT was an effective agronomy option for soil conservation in China, the potential for mitigation climate change through increased SOC sequestration by NT should not be amplified. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) volatilization is a major pathway of nitrogen (N) loss in agricultural systems worldwide, and is conducive to low fertilizer N use efficiency, environmental and health issues, and indirect nitrous oxide emission. While mitigating NH 3 volatilization is urgently needed, a quantitative synthesis is lacking to evaluate the effectiveness of mitigation strategies for NH 3 volatilization from synthetic fertilizers applied in agricultural systems. To fill this knowledge gap, we conducted a meta-analysis of 824 observations on impacts on NH 3 volatilization of ⿿4R Nutrient Stewardship⿿ (right source, rate, place and time), farming practices (irrigation, residue retention, amendments), and enhanced efficiency fertilizers (fertilizers with urease inhibitors, nitrification inhibitors or controlled release coatings). We found that, globally, up to 64% (an average of 18%) of applied N was lost as NH 3 . The use of non-urea based fertilizers, deep placement of fertilizers, irrigation, and mixing with amendments (pyrite, zeolite and organic acids) significantly decreased NH 3 volatilization by 75, 55, 35 and 35%, respectively. In contrast, NH 3 volatilization was not affected by split application, but significantly increased with N application rate and residue retention. Among the enhanced efficiency fertilizers, urease inhibitors and controlled release fertilizers decreased NH 3 volatilization by 54 and 68% respectively whereas nitrification inhibitors increased NH 3 volatilization by 38%. These results confirm that NH 3 volatilization represents a substantial loss of N from agricultural systems, and that this N loss can be mitigated through adaption of appropriate fertilizer products and/or improved management practices. [ABSTRACT FROM AUTHOR]

Afforestation of agricultural land is increasing, partly because it is an important biological method for reducing the concentration of atmospheric CO 2 and potentially mitigating climate change. Rainfall patterns are changing and prolonged dry periods are predicted for many regions of the world, including southern Australia. To accurately predict land-use change potential for mitigating climate change, we need to have a better understanding of how changes in land-use (i.e. afforestation of pastures) may change the soils response to prolonged dry periods. We present results of an incubation study characterising C and N dynamics and the microbial community composition in soil collected from two tree plantings and their adjacent pastures under a baseline and reduced frequency. While the concentration of soil C was similar in pasture and tree planting soils, heterotrophic respiration was significantly lower in soil from pastures than tree plantings. Although there was little difference in the composition of the soil microbial community among any of the soils or treatments, differences in N cycling could indicate a difference in microbial activity, which may explain the differences in heterotrophic respiration between pastures and tree plantings. Soils from pastures and tree plantings responded similarly to a reduction in wetting frequency, with a decrease in microbial biomass (measured as total PLFA), and a similar reduction in heterotrophic respiration from the soil. This suggests that the responses to changes in future wetting cycles may be less dependent on land-use type than expected. [ABSTRACT FROM AUTHOR]

Sequestering atmospheric carbon in soils is considered a key climate change mitigation strategy and including cover crops into cropping systems is commonly promoted as a management change that can increase soil organic carbon (SOC). Projecting SOC changes under climate change when cover crops are integrated into a cropping system is important because climate is a key driver of SOC dynamics and projected changes in climate are uncertain. Further, projecting SOC changes can provide landholders with information on the risk associated with the use of cover crops to generate carbon credits considering the inherent uncertainty in SOC changes under a changing climate. The Agricultural Production SIMulator was used to simulate SOC and yields of a typical crop rotation, with and without a cow pea cover crop, at 204 sites in the Riverina region of Southern Australia. Sowing cover crops reduced crop yields and increased SOC relative to the crop rotation without cover crops. GHG emissions associated with indirect land use change due to reduced crop yields and N 2 O emissions from the cover crop meant that sowing cover crops was unlikely to provide climate change mitigation. The number of carbon credits generated by participating in the soil carbon method of the Australian government's emissions reduction program varied greatly across the region with some sites not generating any credits. The implications of these results are discussed with respect to climate change mitigation and the risk of entering a SOC trading program when costs of compliance are high and the ability to generate carbon credits is uncertain. • Cover crops replace traditional fallow periods in dryland cropping systems. • Cowpea cover crops reduced the yield of cereal, oilseed and legume crops. • Total GHG emissions were generally greater than SOC sequestration. • Replacing fallows with cowpeas unlikely to reduce GHG emissions. • Climate change mitigation was variable across the region of interest. [ABSTRACT FROM AUTHOR]

Reducing greenhouse gas emissions associated with ruminant livestock production is important for climate change mitigation. Regenerative Agriculture (RA) practices are increasingly promoted to improve forage production and livestock performance in temperate livestock systems. These practices include i) rotational grazing (RG) of livestock around multiple subunits of pasture to achieve ungrazed periods of 'rest', and ii) herbal leys (HL), where perennial forbs such as chicory, lucerne and trefoils are included as components in multi-species swards. While there are plausible mechanisms for adoption of these practices to improve agricultural productivity, quantitative syntheses of their impacts are required. Here, we conduct a systematic review and meta-analysis of the effects of RG and HL practices on herbage dry matter (DM) production, animal daily liveweight gain (DLWG), and sheep wool growth in temperate oceanic regions. We use quantitative predictors in our Bayesian hierarchical models to investigate the role of rest period and stocking density in RG systems, and specific plant traits and sward diversity in HL. We found that herbage DM increased by 0.31 t.ha−1 over a growing season as the proportion of rest in an RG grazing system increased from 0 to 1. Stocking density significantly moderated the effect of rest period on sheep and cattle DLWG; at higher stocking densities, longer rest periods were required to maintain livestock growth rates. In HL studies, herbage DM yielded 1.63 t.ha−1 more per metre of increased sward root depth and a sward entirely comprised of legumes yielded 2.20 t.ha−1 more than when no legumes were present. Sheep DLWG increased by 3.50 g.day−1 per unit increase in leaf nitrogen concentration (mg.g−1), but we could not determine an effect of leaf condensed tannin content on animal performance. Although there remain differences between the RG and HL study treatments meta-analysed here and RA in practice, our results provide empirical support for some of the mechanisms attributed to increased pasture and livestock productivity following adoption of selected RA grazing practices. • Regenerative Agriculture (RA) could increase sheep and cattle productivity. • Systematic review and meta-analysis of rotational grazing (RG) and herbal ley (HL) practices. • Longer RG pasture rest period increased forage production and livestock growth. • Root depth, legumes, and species evenness increased dry matter production in HL. • We provide empirical support for mechanisms of increased productivity under RA. [ABSTRACT FROM AUTHOR]

Agroforestry has been proposed as a way to reconcile biodiversity conservation, food production and the delivery of other ecosystem services in tropical landscapes. One such a key ecosystem service, especially in the light of climate change mitigation, is carbon storage. Increasing human disturbance and management intensification, however, are known to affect the carbon storage potential of forests. Here we assessed how the above- and belowground carbon stocks in Ethiopian moist evergreen Afromontane forest co-varied with their biodiversity, and with increasing agroforestry management intensity for the production of Arabica coffee ( Coffea arabica L.). We assessed above- and belowground carbon storage in 60 plots across a gradient of agricultural intensification ranging from natural forest, over two different coffee agroforestry systems, to intensified shade plantations. We quantified the diversity of ground beetles and woody plants in the same plots. Carbon stocks in natural forests (413 ± 55.6 S.E. Mg ha −1 ) and in the most extensively managed agroforestry systems (387 ± 50.0 Mg ha −1 ) were significantly higher than those in the more intensified agroforest system (258 ± 39.4 Mg ha −1 ) and in shade plantations (219 ± 22.8 Mg ha −1 ). Diversity of woody plants, but not of ground beetles, declined with increasing management intensity and decreasing carbon stocks. Overall, this study demonstrates that extensive coffee farming in Ethiopian moist Afromontane forests is able to deliver important co-benefits in terms of woody plant species conservation and carbon storage. Given the associated coffee yield cost, it is most likely, however, that supporting payments from certification or policy mechanisms such as REDD+ are required to keep these extensive coffee agroforestry systems economically viable, which is required to avoid management intensification and associated carbon and biodiversity losses. [ABSTRACT FROM AUTHOR]

Conservation agriculture (CA), comprising minimum soil disturbance, retention of crop residues and crop diversification, is widely promoted for reducing soil degradation and improving agricultural sustainability. It is also claimed to mitigate climate change through soil carbon sequestration: we conducted a meta-analysis of soil organic carbon (SOC) stock changes under CA practices in two tropical regions, the Indo-Gangetic Plains (IGP) and Sub-Saharan Africa (SSA), to quantify this. In IGP annual increases in SOC stock compared to conventional practice were between 0.16 and 0.49 Mg C ha −1 yr −1 . In SSA increases were between 0.28 and 0.96 Mg C ha −1 yr −1 , but with much greater variation and a significant number of cases with no measurable increase. Most reported SOC stock increases under CA are overestimates because of errors introduced by inappropriate soil sampling methodology. SOC increases require careful interpretation to assess whether or not they represent genuine climate change mitigation as opposed to redistribution of organic C within the landscape or soil profile. In smallholder farming in tropical regions social and economic barriers can greatly limit adoption of CA, further decreasing realistic mitigation potential. Comparison with the decreases in greenhouse gas emissions possible through improved management of nitrogen (N) fertilizer in regions such as IGP where N use is already high, suggests that this is a more effective and sustainable means of mitigating climate change. However the mitigation potential, and other benefits, from crop diversification are frequently overlooked when considering CA and warrant greater attention. Increases in SOC concentration (as opposed to stock) in near-surface soil from CA cause improvements in soil physical conditions; these are expected to contribute to increased sustainability and climate change adaptation, though not necessarily leading to consistently increased crop yields. CA should be promoted on the basis of these factors and any climate change mitigation regarded as an additional benefit, not a major policy driver for its adoption. [ABSTRACT FROM AUTHOR]

Coffee agroforestry systems (CAS) are considered as a climate change mitigation option through carbon sequestration. However, most studies on CAS have concentrated on management and productivity of the coffee plants with little known about the soil organic carbon (SOC) stocks. We conducted a study to quantify and compare the SOC stocks among Coffea arabica L. (Arabica coffee), Coffee canephora Pierre ex Froehn (Robusta coffee) agroforestry systems and Coffee monoculture (coffee monocrops) in Uganda. Soil samples were collected at 0–15 cm and 15–30 cm and tested using routine soil testing procedures. We found that there was higher SOC under CAS than coffee monocrops. When intercropped with non- fruit tree species, Robusta CAS produced higher SOC (57.564 tC/ha) compared to the Arabica CAS (54.543 tC/ha). In contrast, Arabica CAS stored more SOC (54.01 tC/ha) compared to Robusta CAS (49.635 tC/Kg) when intercropped with fruit trees like Artocarpus heterophyllus Lam. and Mangifera indica L. Under the coffee monocrop systems, Robusta coffee sequestered 4.86 tC/ha more SOC than Arabica coffee. The study showed that a farmer growing Robusta coffee intercropped with non-fruit trees is likely to benefit more from soil carbon credits than a farmer growing Arabica coffee with the same trees. Farmers growing Arabica coffee would sequester more carbon if intercropped with fruit trees. There is need for policy incentives that encourage the planting and maintenance of shade trees in coffee plantations for the benefit of carbon sequestration. [ABSTRACT FROM AUTHOR]

The importance of increasing crop production while reducing resource inputs and land-use change cannot be overstated especially in light of climate change and a human population growth projected to reach nine billion this century. Mutualistic plant–microbe interactions offer a novel approach to enhance agricultural productivity while reducing environmental costs. In concert with other novel agronomic technologies and management, plant-microbial mutualisms could help increase crop production and reduce yield losses by improving resistance and/or resilience to edaphic, biologic, and climatic variability from both bottom-up and top-down perspectives. [ABSTRACT FROM AUTHOR]

The fifth assessment report of the intergovernmental panel on climate change (IPCC) estimated that by 2040 agroforestry would offer high potential of carbon (C) sequestration in developing countries. However, the role of tropical agroforestry in C sequestration and in climate change mitigation has only recently been recognized by United Nations Framework Convention on Climate Change (UNFCCC). This is partly due to the lack of reliable estimates on the sequestration potential in biomass and soil carbon pools over time. The aim of this study was to analyze the changes in the biomass and soil carbon pools of three indigenous agroforestry systems in south-eastern Rift Valley escrapment of Ethiopia using CO2FIX (v. 3.2) model. The agroforestry systems studied were Enset ( Ensete ventricosum )-tree, Enset-coffee-tree, and Tree-coffee systems. To run the model, empirical data collected from 60 farms (20 farms for each agroforestry system) and literature were used as inputs to parameterize the model. Simulations were run over a period of 50 years. Average simulated total biomass C stocks was the highest for Tree-coffee system (122 Mg C ha −1 ), followed by the Enset-coffee-tree (114 Mg C ha −1 ) and Enset-tree system (76 Mg C ha −1 ). The tree cohort accounted for 89–97% of the total biomass C stocks in all the studied systems, and the reminder was shared by Enset and coffee cohorts. The total average simulated total C stocks (biomass and soil) were 209, 286 and 301 Mg C ha −1 for Enset-tree, Enset-coffee-tree and Tree-coffee systems, respectively. The soil organic carbon (SOC) stocks accounted for 60–64% of the total carbon in the studied systems. Model validation results showed that long-term (10–40 years) simulated biomass C stocks were within the range of measured biomass C stocks for Enset-tree and Enset-coffee-tree systems, but significantly differed for the Tree-coffee system. The simulated soil and total C stocks were within the range of measured values for all the three systems. The CO2FIX model accurately predicted the SOC and total C stocks in the studied indigenous agroforestry systems, but the prediction of the biomass C stocks could be improved by acquiring more accurate input parameter values for running the model. [ABSTRACT FROM AUTHOR]

Massive grasslands on the Qinghai-Tibetan Plateau(QTP) provide vital ecosystems services, which have been decreased by land degradation associated with global change. Effective efforts and actions of restoration and management are required to promote the sustainable development of these grassland ecosystems with global importance. This special issue collected numerous papers to address share the innovative theoretical foundations and practical approaches for restoring and protecting QTP's grassland ecosystems in the era of global change. The findings from the collected papers of this special issue stated that the ecosystems services of the QTP's grasslands are declining due to weakened interfaces among soil, plant and grazing animals in the QTP's grassland ecosystems by climate and land use changes. Applicable actions such as climate change mitigation and adaptation, close-to-nature restoration, rotational grazing regime with moderate grazing intensity should be taken to enhance the ecosystem services through rebuilding rational soil-plant-animal interfaces. • Both climate change and human activities led to grassland degradation. • Grassland degradation have weakened the ecosystem services. • Restoration and rational grazing can enhance sustainability of grasslands. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) sequestration by improved agricultural practices is an acclaimed strategy to combat climate change. Nevertheless, the aim of increasing of SOC encounters limitations, e.g. with regards to permanence of carbon storage or leakage effects in food production. Agroforestry systems (AFS) are a promising land use option that is able to sequester substantial amounts of SOC while addressing these challenges. With a focus on temperate climate zones worldwide, available information on SOC in AFS was reviewed to determine their SOC sequestration potential and respective controlling factors. From a total of 61 observations, SOC sequestration rates in soils of AFS were derived for alley cropping systems (n = 25), hedgerows (n = 26) and silvopastoral systems (n = 10). The results showed that AFS have a potential for substantial SOC sequestration in temperate climates. SOC stocks were higher in the topsoil (0–20 cm) than in the control in more than 70% of the observations, and higher within the subsoil (20–40 cm) for 81% of all observations, albeit large variation in the data. The mean SOC sequestration rates were slightly higher at 0–20 cm (0.21 ± 0.79 t ha-1 yr-1) compared to 20–40 cm soil depth (0.15 ± 0.26 t ha-1 yr-1). Hedgerows revealed highest SOC sequestration rates in topsoils and subsoils (0.32 ± 0.26 and 0.28 ± 0.15 t ha-1 yr-1, respectively), followed by alley cropping systems (0.26 ± 1.15 and 0.23 ± 0.25 t ha-1 yr-1) and silvopastoral systems showing a slight mean SOC loss (−0.17 ± 0.50 and −0.03 ± 0.26 t ha-1 yr-1). Moreover, SOC sequestration rates tended to be higher for AFS with broadleaf tree species compared to coniferous species. We conclude that temperate AFS sequester significant amounts of SOC in topsoils and subsoils and represent one of the most promising agricultural measures for climate change mitigation and adaption. • Agroforestry has a highly significant and positive effect on SOC sequestration in the temperate zone. • SOC stocks in temperate AFS are generally higher than in treeless agricultural sites. • The amount of sequestered SOC was slightly higher at 0–20 cm compared to 20–40 cm soil depth. • Hedgerows revealed higher SOC sequestration rates than alley cropping and silvopastoral systems. • SOC sequestration rates were higher for AFS with broadleaf tree species compared to coniferous species. [ABSTRACT FROM AUTHOR]

Highlights: [•] Straw incorporation in paddy fields enhanced CH4 emissions. [•] Biochar amendment in paddy fields reduced CH4 emissions. [•] N2O emissions increased by biochar, but decreased by straw incorporation. [•] Biochar amendment is a candidate practice to mitigate GHG emissions in paddy fields. [ABSTRACT FROM AUTHOR]

Rice paddies are a major anthropogenic source of greenhouse gas (GHG) emissions due to the flooding management. Water saving practices often reduce the GHG emissions from rice paddies, yet increase the risk of rice yields loss due to drought stress. Water-saving and drought-resistance rice (WDR) has high drought-tolerant, suggesting that WDR with water-saving management could reduce GHG emissions while maintaining rice yields. However, the effect of WDR on GHG emissions is still unclear. Therefore, we conducted a 2-yr field experiment to assess the effect of WDR on rice yields and GHG emissions under continuous flooding (F), alternate wetting and drying (AWD), and dry cultivation (D) conditions, using a WDR variety and a common variety. Compared to the common variety, the WDR did not affect the rice yields under F and AWD treatments, but increased rice yields by 24% under D treatment. The methane (CH 4) emissions and nitrous oxide (N 2 O) emissions of the two rice varieties were similar. Compared to the F treatment, AWD treatment reduced CH 4 emissions by 7%−64% and area-scaled global warming potential (GWP) by 9%−39% and D treatment reduced CH 4 emissions by 70%−90% and area-scaled GWP by 65%−74%. The WDR with dry cultivation (D -WDR mode) had the lowest area- and yield-scaled GWP. Our findings indicate that it is possible to produce optimal rice yields with low GHG emissions in the D -WDR mode, and suggest that drought-resistance rice variety breeding may benefit climate change mitigation and adaptation efforts. • Interannual greenhouse gases mitigation varied from AWD. • WDR did not affect the rice yields under F and AWD, but increased yields by 24% under D. • D -WDR mode cut methane emissions dramatically with comparable rice yields. • Breeding drought-resistance rice benefits climate change mitigation and adaptation. [ABSTRACT FROM AUTHOR]

Household biogas production from livestock manure is popular in Vietnam. Effluent from the biogas production can be effectively used as organic fertilizer for rice cultivation. However, there is concern about enhanced methane (CH 4) emission from the flooded soil under reductive conditions because the effluent contains labile organic carbon, the substrate for microbial CH 4 production. We therefore combined multiple drainage with "cattle biogas effluent" (BE) application to mitigate CH 4 emission by ameliorating the reductive soil conditions while obtaining grain yields comparable to the conventional practice, a combination of synthetic fertilizers (SY) application and continuous flooding (CF). We performed a 1-year experiment on a lowland (0 m a.s.l.) paddy field in the Mekong Delta, Vietnam, under a triple cropping system. We examined the effects of fertilizer type (SY and BE) and water management (CF, alternate wetting and drying [AWD], and midseason drainage followed by intermittent irrigation [MiDi]) on rice growth and yield and on CH 4 and nitrous oxide (N 2 O) emissions. For AWD, a surface water level of −15 cm was used as the threshold for re-irrigation after natural drainage, whereas MiDi used a fixed irrigation schedule with one-time forced drainage during the midseason drainage period. Surface water level did not drop sufficiently in either AWD or MiDi due to the lowland conditions, and both practices caused similar seasonal changes in water level except for the forced drainage in MiDi. A significant (P = 0.05) interaction between fertilizer type and water management on grain yield was found only in dry season (winter–spring) with the highest yield level. Despite the poorly drained conditions, CH 4 emission was significantly reduced by AWD and MiDi (by 27–30%), and both practices offset the significant CH 4 emission enhancement by BE application. N 2 O emission was significantly reduced by BE application, whereas it was not affected by water management because flooded conditions were maintained during every nitrogen fertilizer application. Our results indicate that the combination of BE application and multiple drainage can mitigate CH 4 and N 2 O emissions from a lowland rice paddy in the Mekong Delta without yield loss. [Display omitted] • Less soil CH 4 and N 2 O emissions from combination of cattle biogas effluent and multiple drainage without grain yield loss. • The effluent achieved grain yield comparable to synthetic fertilizers. • Multiple drainage did not change grain yield relative to continuous flooding. • Multiple drainage offset soil CH 4 emission enhancement by the effluent. • Soil N 2 O emission was not increased by the effluent or multiple drainage. [ABSTRACT FROM AUTHOR]

Highlights: [•] The carbon assimilation of representative citrus plantations in Eastern Spain was estimated. [•] Our plantation was responsible for a net carbon fixation rate of higher than 10MgCha−1 yr−1. [•] Leaf assimilatory processes mainly determined the annual pattern of C sequestration. [•] Under typical culture conditions, soil respiration rates accounted for low C losses. [•] The results of this study are relevant to climate change mitigation. [Copyright &y& Elsevier]

Abstract: Global agriculture lies in intersection of two inescapable issues of the present times, viz. keeping pace with growing food demand and participating in climate change mitigation efforts. Rice cultivation is a major emitter of greenhouse gases (GHGs) and no tillage of soil is becoming popular due to low economic investments with improved soil conditions. However, how these arrangements will affect GHG emissions need to be quantified. Therefore, monitoring over diverse agricultural practices is essential for optimum utilization of cultivable land and resources, while identifying the chances of emission reductions. We assessed the impacts of four tillage practices in rice–wheat cultivation system on fluxes of GHGs (CH4, N2O and CO2) and yield of rice. The tillage practices were tilling of soil before sowing of every crop (RCT-WCT), tillage before sowing of rice but no tillage before sowing of wheat (RCT-WNT), tillage before sowing of wheat but no tillage before sowing of rice (RNT-WCT), and no tillage before sowing of rice as well as wheat (RNT-WNT). Reduction in tillage frequency led to significant reductions in fluxes of CH4 and N2O, but increased CO2 while permutations of tillage and no tillage influenced grain yield. RNT-WCT produced next to or comparable to the most yielding RCT-WCT. Although it is difficult to select the best performer since no single tillage permutation showed consistent increment in yield with accompanied emission reductions, RNT-WCT, however may be considered as better agricultural practice for the study region. Long term and extensive spatio-temporal monitoring is still required before making any recommendation. It is also essential for understanding the factors that cause declination in yields under no tillage. [Copyright &y& Elsevier]

Abstract: For climate mitigation it is important to identify and protect landscape units that have disproportionally large carbon storage (CS). Here we report on CS of the upper 30 and 60cm of soil in transects of vegetation types in stream valleys in the Brazilian Cerrado savanna, including Pasture, nearly native Cerrado vegetation, Vereda wetlands, and Gallery Forests. We chose three areas with varying types of human impacts in each of which three degraded and reference transects were compared. For the 60cm CS in undisturbed sites, maximum and average values per area were highest for Gallery Forest (360.0 and 206.5MgCha−1) and Vereda wetland (201.9 and 142.4MgCha−1), while those of Cerrado (57.7 and 52.7) and Pasture (62.3 and 52.7MgCha−1) were considerably lower. Variation between the three areas was high. In an area degraded by cattle trampling, losses in the upper 60cm compared to reference sites were highest in the carbon-rich vegetation types Vereda (72%) and Gallery Forest (71%) and lower in the carbon-poorer Pasture (33%) and Cerrado (7%). In areas degraded by fire or by erosion, results were less conclusive. Our data appeal to an improved conservation of riparian ecosystems of the Cerrado biome. [Copyright &y& Elsevier]

Abstract: Results from the UK were reviewed to quantify the impact on climate change mitigation of soil organic carbon (SOC) stocks as a result of (1) a change from conventional to less intensive tillage and (2) addition of organic materials including farm manures, digested biosolids, cereal straw, green manure and paper crumble. The average annual increase in SOC deriving from reduced tillage was 310kg C±180kgCha−1 yr−1. Even this accumulation of C is unlikely to be achieved in the UK and northwest Europe because farmers practice rotational tillage. N2O emissions may increase under reduced tillage, counteracting increases in SOC. Addition of biosolids increased SOC (inkgCha−1 yr−1 t−1 dry solids added) by on average 60±20 (farm manures), 180±24 (digested biosolids), 50±15 (cereal straw), 60±10 (green compost) and an estimated 60 (paper crumble). SOC accumulation declines in long-term experiments (>50 yr) with farm manure applications as a new equilibrium is approached. Biosolids are typically already applied to soil, so increases in SOC cannot be regarded as mitigation. Large increases in SOC were deduced for paper crumble (>6tCha−1 yr−1) but outweighed by N2O emissions deriving from additional fertiliser. Compost offers genuine potential for mitigation because application replaces disposal to landfill; it also decreases N2O emission. [Copyright &y& Elsevier]

Abstract: Characterizing the carbon footprint (CF) of agricultural production offers key information for pursuing low carbon agriculture and food consumption. While China has long strived for increasing food production capacity for its large and still growing population, the high emissions cost, especially from the over use of agro-chemicals, has been widely debated for the last decade. However, the CF of China''s crop production has not yet been assessed. This paper reports a basic estimate of CF of crop production using national statistical data available for the period of 1993–2007. The dataset includes the amount of individual agricultural inputs (fertilizer, pesticide, diesel, plastic film, etc.), cultivation area and total of production whole crops. Using the emission factors estimated for China''s agricultural features and available abroad, the mean overall CF of China''s crop production was estimated to be 0.78±0.08tCEha−1 yr−1 and 0.11±0.01tCEt−1 yr−1, for land use and bulk production respectively. For the duration the data covered, the carbon intensity under cultivation land use was seen to increase since 1993. Among the total, fertilizer induced emissions exerted the largest contribution of ∼60%, being 0.45±0.04tCE per ha and 0.07±0.01tCE per ton of production, on average. Compared to the UK, the estimated overall CF of China''s crop production was higher in terms of cultivation land use. While there was a significant positive correlation of carbon intensity with total production, carbon efficiency was shown in a decreasing trend during 2003-2007. Therefore, low carbon agriculture should be pursued, and the priority should be given to reducing fertilizer application in agriculture of China. However, for developing best management practices for climate change mitigation in crop production of China, further studies of crop and regional specific CFs and the variation with climate conditions and agricultural managements are needed. [Copyright &y& Elsevier]

Abstract: Biochar addition to agricultural soil has been suggested to mitigate climate change through increased biogenic carbon storage and reduction of greenhouse gas emissions. We measured the fluxes of N2O, CO2, and CH4 after adding 9tha−1 biochar on an agricultural soil in Southern Finland in May 2009. We conducted these measurements twice a week for 1.5 months, between sowing and canopy closure, to capture the period of highest N2O emissions, where the potential for mitigation would also be highest. Biochar addition increased CH4 uptake (96% increase in the average cumulative CH4 uptake), but no statistically significant differences were observed in the CO2 and N2O emissions between the biochar amended and control plots. Added biochar increased soil water holding capacity by 11%. Further studies are needed to clarify whether this may help balance fluctuations in water availability to plants in the future climate with more frequent drought periods. [Copyright &y& Elsevier]

Abstract: Soil C sequestration in cropland could play an important role in mitigating the rapidly increasing CO2 emissions in China. Many efforts had been dedicated to estimating the potential for C sequestration in croplands. Potential increases in SOC in China''s croplands had been recently evaluated using inventory-up-scaling simulation and crop-soil C process-based modeling. In this study, data of SOC change at monitoring sites from croplands across mainland China were collected from publications available from 1985 to 2006 to perform a statistical analysis. The data set comprises 1081 observations (404 from rice paddies, RPs and 677 from dry croplands, DCs). Frequency analysis indicates that over 70% of observations show an increase in SOC, which is higher among RPs than DCs. To quantify SOC dynamics, a Relative Annual Change Index in gkg−1 year−1 (RAC, gkg−1 year−1) is defined and calculated using the initial and final SOC values for the duration of monitored observations. RAC values ranged from −0.806 to 0.963gkg−1 year−1 for DCs and from −0.597 to 0.959gkg−1 year−1 for RPs, respectively. From this data, the average is estimated to be 0.056±0.200gkg−1 year−1 for DCs, and 0.110±0.244gkg−1 year−1 for RPs, with an overall estimate for China''s croplands, with RPs and DCs combined, of 0.076±0.219gkg−1 year−1. A mean increase in topsoil C (0–20cm) stock of China''s croplands was estimated to be 25.5TgCyear−1 (8TgCyear−1 in RPs and 17.5TgCyear−1 in DCs) between 1985 and 2006, with a total topsoil C stock increase of 0.64 Pg C over the whole period. The annual stock increase may offset ∼20%, on average, of the total CO2 emissions of China for 1994. This study suggests an important role of China''s croplands, especially rice paddies, for C sequestration to mitigate climate change. [Copyright &y& Elsevier]

Abstract: For thousands of years, the Huang-Hai Plain in northeast China has been one of the most productive agricultural regions of the country. The future of this region will be determined in large part by how global climatic changes impact regional conditions and by actions taken to mitigate or adapt to climate change impacts. One potential mitigation strategy is to promote management practices that have the potential to sequester carbon in the soils. The IPCC estimates that 40Pg of C could be sequestered in cropland soils worldwide over the next several decades; however, changes in global climate may impact this potential. Here, we assess the potential for soil C sequestration with conversion of a conventional till (CT) continuous wheat system to a wheat–corn double cropping system and by implementing no till (NT) management for both continuous wheat and wheat–corn systems. To assess the influence of these management practices under a changing climate, we use two climate change scenarios (A2 and B2) at two time periods in the EPIC agro-ecosystem simulation model. The applied climate change scenarios are from the HadCM3 global climate model for the periods 2015–2045 and 2070–2099 which projects consistent increases in temperature and precipitation of greater than 5°C and up to 300mm by 2099. An increase in the variability of temperature is also projected and is, accordingly, applied in the simulations. The EPIC model indicates that winter wheat yields would increase on average by 0.2Mgha−1 in the earlier period and by 0.8Mgha−1 in the later period due to warmer nighttime temperatures and higher precipitation. Simulated yields were not significantly affected by imposed changes in crop management. Simulated soil organic C content was higher under both NT management and double cropping than under CT continuous wheat. The simulated changes in management were a more important factor in SOC changes than the scenario of climate change. Soil C sequestration rates for continuous wheat systems were increased by an average of 0.4Mgha−1 year−1 by NT in the earlier period and by 0.2Mgha−1 year−1 in the later period. With wheat–corn double cropping, NT increased sequestration rates by 0.8 and 0.4Mgha−1 year−1 for the earlier and later periods, respectively. The total C offset due to a shift from CT to NT under continuous wheat over 16 million hectares in the Huang-Hai Plain is projected to reach 240TgC in the earlier period and 180TgC in the later period. Corresponding C offsets for wheat–corn cropping are 675–495TgC. [Copyright &y& Elsevier]

• The overall N surplus hazard decreased significantly during the period of study. • The groundwater status related to NO 3 − is not improving, but aggravating instead. • In 2016, 33 and 66 % of the area showed respectively high and moderate pollution risks. • GRI complements N surplus in assessing the impact of measures on groundwater quality. • Scenario analysis confirms that targeted measures are more effective than global ones. In the Nitrate Vulnerable Zones farmers are required to implement measures to reduce the nitrogen (N) surplus. Nevertheless, in some cases the status of the water bodies show that the effect of these measures remains insufficient despite the global decrease in N surpluses. The present work aims to contribute with a method that produces an appropriate indicator for the N mitigation measures effectiveness for reducing groundwater nitrate pollution. The Global Risk Index (GRI) results from overlaying the agricultural N surplus hazard and aquifer vulnerability. It includes both irrigation activity and precipitation contribution to water recharge calculated at the municipality level. It integrates a range of regional datasets combined with monitored nitrate (NO 3 −) concentrations in groundwater under a GIS framework. Results show that the pollution status of the Tagus Vulnerable Zone (TVZ) aquifers has been aggravating in spite of the overall reduction in the N surpluses that resulted from the implementation of the Nitrates Directive measures. Twelve years after the TVZ designation, the GRI indicates high and moderate NO 3 - pollution risk, respectively in 33 % and 66 % of the territory. Scenario analysis indicates the potential of targeted measures for ending high risk areas and reducing moderate risk areas to 13 %. This supports that N mitigation measures must be reformulated and spatially targeted according to site specific hazards and vulnerabilities. [ABSTRACT FROM AUTHOR]