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Abstract

We present new and synthesize published results from long-term field studies exploring management options for carbon sequestration in cropland and grassland. Agricultural practices were evaluated within the framework set by global food demand and limited area available for agricultural production. Among options for higher C sequestration, we found minimizing the time with bare soil, improving recycling of organic materials and increasing yields through N fertilization to be efficient. Indeed, our results suggest that C stocks can increase with 1–2 kg C for each kg of mineral N fertilizer applied. Possibilities to decrease C emissions by reduced tillage were found to be limited under Nordic conditions. Options for reducing C emissions from drained cultivated organic soils are limited when used as cropland. Extensive production leads to lower soil C stocks and requires more land. Increasing photosynthesis at the global scale by intensification of crop production was found to be the most effective mitigation option and is a prerequisite for preventing further areal expansion of agriculture.

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... SOC stocks are in equilibrium when the C inputs are equal to the outputs. Carbon is being sequestered in soils only when the C inputs are greater than the outputs (negative CO 2 emissions), and the net removal of CO 2 from the atmosphere through photosynthesis left in the field is transformed into soil organic matter pools with long turnover times (long-lived SOC) (Kätterer et al. 2012;Powlson et al. 2011b). The magnitude of the plant C inputs from aboveground post-harvest residues and rhizodeposition (i.e., root-derived material) that remain in the field are driven by NPP, which is therefore a crucial factor with respect to potential C sequestration in soils (Bolinder et al. 2007). ...
... High background levels of SOC stocks, already present in soils, is making it difficult assessing short (1-5 years) to medium-term (˃ 5-10 years) changes. The treatment effects of different management practices on SOC are more easily measurable when they have been accumulating over periods longer than 10 years (Smith 2004;Kätterer et al. 2012). Continuous soil monitoring initiatives such as LUCAS (Land Use and Coverage Area Frame Survey), modeling approaches (e.g., RothC, Century) and long-term (˃ 10 years) field experiments (LTEs) are among the most common tools studying changes in SOC stocks in agroecosystems. ...
... Similar to the effects for cover crops, the effect of N fertilization was also more consistent among studies, in particular for RR but with the exception regarding a high SCR value from the study by Aguilera et al. (2013). The role of major nutrients in SOC dynamics is complex because of the simultaneous effects on NPP and in the rate of heterotrophic respiration through N mining and mineralization of organic matter (Poeplau et al. 2016b), but it remains well recognized that there is a positive effect of N fertilization on SOC in agroecosystems (Kätterer et al. 2012). This is mainly an input-driven effect, where the increase in NPP (and yields) results in higher amounts of annual C inputs to soil from aboveground post-harvest crop residues and rhizodeposition (e.g., Christopher and Lal 2007). ...
Article
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International initiatives are emphasizing the capture of atmospheric CO2 in soil organic C (SOC) to reduce the climatic footprint from agroecosystems. One approach to quantify the contribution of management practices towards that goal is through analysis of long-term experiments (LTEs). Our objectives were to analyze knowledge gained in literature reviews on SOC changes in LTEs, to evaluate the results regarding interactions with pedo-climatological factors, and to discuss disparities among reviews in data selection criteria. We summarized mean response ratios (RRs) and stock change rate (SCR) effect size indices from twenty reviews using paired comparisons (N). The highest RRs were found with manure applications (30%, N = 418), followed by aboveground crop residue retention and the use of cover crops (9–10%, N = 995 and 129), while the effect of nitrogen fertilization was lowest (6%, N = 846). SCR for nitrogen fertilization exceeded that for aboveground crop residue retention (233 versus 117 kg C ha−1 year−1, N = 183 and 279) and was highest for manure applications and cover crops (409 and 331 kg C ha−1 year−1, N = 217 and 176). When data allows, we recommend calculating both RR and SCR because it improves the interpretation. Our synthesis shows that results are not always consistent among reviews and that interaction with texture and climate remain inconclusive. Selection criteria for study durations are highly variable, resulting in irregular conclusions for the effect of time on changes in SOC. We also discuss the relationships of SOC changes with yield and cropping systems, as well as conceptual problems when scaling-up results obtained from field studies to regional levels.
... All ecosystems like forests, grasslands, croplands take up atmospheric carbon dioxide (CO 2 ), mineral nutrients and transform them into organic products. The potential of sequestering atmospheric carbon in soils of all these ecosystems is different which depends on the type of the system, species composition, age of component species, geographic location, various environmental factors, and of course on management practices (Kätterer et al. 2012). Equally, the amount of natural SOC varies depending on the type and texture of soil, waterlogging conditions and the degree of soil cultivation (Tripolskaja et al. 2010). ...
... In 2015 as in 1995 it remained 28 cm thick and it confirms the fact that humus accumulation in the loamy sand soil of arable land is hardly possible as the major part of biomass is brought out, and the remainder does not counter balance organic matter consumption and the extent of mineralisation. Humus accumulation is stimulated by such agrotechnical measures as incorporation of non-organic and organic fertilisers, plant residues and other biomass as well as zero tillage (Kätterer et al. 2012, Lal 2013, Jin et al. 2014). During the 21 year period organic carbon stocks in the Ap horizon decreased by 11.31 Mg ha -1 organic carbon and its concentration -from 9.5 to 6.8 mg kg -1 . ...
... Application of mineral fertilisers increases both aboveground and belowground biomass of herbaceous plants and creates preconditions for faster soil carbon sequestration in soil (Kätterer et al. 2012, Lal 2013. In our experiment fertilised grassland SOC stock increased by 13.4% over 21 years in Ap horizon. ...
Article
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Conversion of arable soils into other land uses can stabilize and increase accumulation of soil organic carbon (SOC) and in addition prevent deterioration in its properties. The data has shown changes in SOC sequestration in Ap horizon after arable land conversion (1995-2015) into managed grassland, abandoned and pine afforested. SOC in Arenosol topsoil was positively affected by long term fallow and conversion into grassland. Abandoned land and fertilised managed grassland accumulated significantly more SOC, 48% and 38% respectively compared with arable land. In unfertilised managed grassland SOC stocks decreased 2.3% during 21 years, but losses were lower than in fertilised arable land. Pine afforestation of loamy sand helped to reduce the intensity of SOM mineralization compared to arable land. The Ap horizon thickness in pine forest soil increased from 28 to 31 cm during 21 years period. However, SOC stock decreased by 1% due to reduction in carbon concentration.
... Further, the nutrient supply affects SOC dynamics in a complex manner through its simultaneous effects on NPP and on the rate of heterotrophic respiration through nitrogen mining and mineralization of organic matter (Poeplau et al., 2016). Nonetheless, it is generally recognized for agroecosystems that the effect of nitrogen fertilization on SOC is positive because of increasing NPP (and yields), resulting in higher carbon inputs to the soil from aboveground and belowground post-harvest crop residues (Christopher and Lal, 2007;Kätterer et al., 2012). The review by Alvarez (2005) demonstrated this by establishing a relationship indicating that SOC storage increased by 2 kg C ha −1 for each additional 1 kg N ha −1 applied. ...
... The review by Alvarez (2005) demonstrated this by establishing a relationship indicating that SOC storage increased by 2 kg C ha −1 for each additional 1 kg N ha −1 applied. On analyzing LTEs under Nordic conditions, Kätterer et al. (2012) obtained similar results, with SOC in the topsoil (0-20 cm) increasing by 1-2 kg C ha −1 year −1 for each extra kg of nitrogen applied. According to VandenByggart et al. (2003), using an unfertilized treatment as the reference may overestimate the effect of nitrogen fertilization, since both SOC and yield responses are lower at higher nitrogen application rates. ...
Chapter
Increasing carbon storage in soils is one way of mitigating climate change. Carbon sequestration in agricultural soils through improved management is particularly interesting, because of low costs and technical readiness. In this chapter, we synthesize current knowledge on the impact of management practices that promote carbon accumulation in upland mineral soils. Following a brief overview of the principles, we summarize results from meta-analyses quantifying these effects in long-term field experiments and discuss problems with upscaling field-derived data to regional or global scale. In a case study, we highlight the gain in soil fertility from increased carbon stocks. Despite uncertainties, there is strong evidence that management practices such as crop rotations, manures, residue retention, and cover crops can promote carbon storage. The most effective practices are those that increase net primary production through fertilization and those that reduce the time without plant cover by introducing cover crops and using perennial crops in rotations.
... Numerous studies reported the effects of N fertilization on SOC in croplands, but the results are inconsistent. Increased (Jagadamma et al., 2007;Katterer et al., 2012;Tong et al., 2014), decreased (Khan et al., 2007), or no change in SOC with N fertilization (Brown et al., 2014) have all been reported. An increase in SOC may be related to reducing lignin-oxidizing enzymes resulting in lowering C decomposition (Chen et al., 2018a) or stimulating net primary production and crop derived-C input to soil (Katterer et al., 2012) under N fertilization. ...
... Increased (Jagadamma et al., 2007;Katterer et al., 2012;Tong et al., 2014), decreased (Khan et al., 2007), or no change in SOC with N fertilization (Brown et al., 2014) have all been reported. An increase in SOC may be related to reducing lignin-oxidizing enzymes resulting in lowering C decomposition (Chen et al., 2018a) or stimulating net primary production and crop derived-C input to soil (Katterer et al., 2012) under N fertilization. Whereas, a decrease in SOC may be associated with an increasing rate of SOC decomposition, as a result of increasing activities of heterotrophic microorganisms and enzymes with N addition (Khan et al., 2007;Liang et al., 2014). ...
Article
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Nitrogen (N) fertilization and plastic film mulching (PFM) are two widely applied management practices for crop production. Both of them impact soil organic matter individually, but their interactive effects as well as the underlying mechanisms are unknown. Soils from a 28-year field experiment with maize monoculture under three levels of N fertilization (0, 135, and 270 kg N ha⁻¹ yr⁻¹) and with or without PFM were analyzed for soil organic C (SOC) content, total soil nitrogen (N), root biomass, enzyme activities, and SOC mineralization rates. After 28 years, N fertilization increased root biomass and consequently, SOC by 26% (averaged across the two fertilizer application rates) and total soil N by 25%. These increases, however, were only in soil with PFM, as PFM reduced N loss through leaching, as a result of a diurnal internal water cycle under the mulch. The SOC mineralization was slower with N fertilization, regardless of the PFM treatment. This trend was attributed to the 43% decrease of β-glucosidase activity (C cycle enzyme) and 51% drop of leucine aminopeptidase (N cycle) with N fertilization, as a result of a strong decrease in soil pH. In conclusion, root biomass acting as the main source of soil C, resulted in an increase of soil organic matter after 28 year of N fertilization only with PFM.
... Another regulating ecosystem service is the sequestration of soil organic carbon (SOC) in soils. By selecting appropriate crops and cultivation practices, agriculture can act as a carbon sink [14,15]. Large carbon stocks in arable soils are also beneficial from a food and feed sustainability perspective, as they increase soil fertility [16]. ...
... Sequestration of SOC is a reversible and highly complex process. Its rate is dependent on a large number of factors, such as initial SOC stocks (i.e., earlier land use), crops cultivated, soil texture, temperature, precipitation, nitrogen fertilisation, farming practices, and tillage, etc. [14][15][16]. The process may have a non-linear pattern over time and is finite and long-term, as it may take 100 years to reach equilibrium [14]. ...
Article
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Small arable fields are beneficial with regard to ecosystem services, e.g., concerning biodiversity. By selecting appropriate crops and cultivation practices, arable fields can also be used as carbon sinks. The objectives of this study were to investigate what impact field conditions (e.g., field size and shape) and payments (subsidies) for environmental benefits have on profitability. A dynamic simulation model was used to simulate machine operations in fields of two different shapes and five different sizes (from 0.75 to 12.00 ha). A wide range of crops cultivated in Sweden were investigated (fallow land and plantation of Norway spruce were also included). A perimeter-based subsidy was suggested in order to conserve and promote biodiversity, and an area- and crop-based subsidy was suggested in order to promote sequestration of soil organic carbon (SOC). The results showed that, without financial support and from a purely economic point of view, most field types investigated should be planted with Norway spruce. With currently available subsidies, e.g., EU Common Agricultural Policy (CAP) direct payments, hybrid aspen, poplar, fallow, and extensive ley cultivation are the most profitable crops. Perimeter-based subsidies favoured the net gain for small fields. As expected, a subsidy for sequestration of SOC favoured cultivation of specific SOC-sequestering crops such as ley, willow, and poplar. Our recommendation for future studies is to investigate a well-balanced combination of perimeter-based support and SOC sequestration support that benefits biodiversity and climate under different cultivation conditions.
... The pH of the soil used in the present study is above 8, while that of the previous studies was less than 5. Zhang et al. [25] documented that N enrichment lowered the pH of the acidic soil, which hindered microbial activities and production. Soils with low pH suppress the growth and activity of microbes, especially bacteria [22,37], thereby reducing amino sugar accumulation in N-fertilized soils [25,38]. In the present study, N enrichment reduced soil pH close to the neutral range (Table 2), which might have facilitated microbial growth and activity; consequently, this stimulated microbial residues and amino sugar accumulation. ...
... Moreover, Fontaine et al. [76] observed that high N enrichment stores more carbon in the soil due to the prime effect. Our results are in agreement with previous studies where increasing N enrichment significantly increased SOC [37,70,74]. Total N content in the soil increased with an increasing N rate and could probably be attributed to N accumulation from the chronic N enrichment, as crop N depletion was less than N inputs over time. ...
Article
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Amino sugars are key microbial biomarkers for determining the contribution of microbial residues in soil organic matter (SOM). However, it remains largely unclear as to what extent inorganic nitrogen (N) fertilization can lead to the significant degradation of SOM in alkaline agricultural soils. A six-year field experiment was conducted from 2013 to 2018 to evaluate the effects of chronic N enrichment on microbial residues, amino sugars, and soil biochemical properties under four nitrogen (urea, 46% N) fertilization scenarios: 0 (no-N, control), 75 (low-N), 225 (medium-N), and 375 (high-N) kg N ha −1. The results showed that chronic N enrichment stimulated microbial residues and amino sugar accumulation over time. The medium-N treatment increased the concentration of muramic acid (15.77%), glucosamine (13.55%), galactosamine (18.84%), bacterial residues (16.88%), fungal residues (11.31%), and total microbial residues (12.57%) compared to the control in 2018; however, these concentrations were comparable to the high-N treatment concentrations. The ratio of glucosamine to galactosamine and of glucosamine to muramic acid decreased over time due to a larger increase in bacterial residues as compared to fungal residues. Microbial biomass, soil organic carbon, and aboveground plant biomass positively correlated with microbial residues and amino sugar components. Chronic N enrichment improved the soil biochemical properties and aboveground plant biomass, which stimulated microbial residues and amino sugar accumulation over time.
... Added nitrogen can form nitrous oxide (N2O), a powerful greenhouse gas, or nitrate (NO3 -), ammonia (NH3), ammonium (NH4 + ) and nitrogen oxides (NOx), which can subsequently form N2O or cause eutrophication in water bodies. The yield increase following fertilisation also has a substantial effect on soil organic carbon (SOC) accumulation in soil and the amount of land required to produce a certain amount of crop (Kätterer et al., 2012;Balmford et al., 2005). Fertiliser use in agriculture thus has many effects on the agricultural system and its environmental impacts, and adequate tools are needed to evaluate this environmental impact. ...
... Many agricultural soils located across different continents and areas with different economic levels have a negative nitrogen balance, i.e. the removal by crops and losses exceed the input (Liu et al., 2010). The direct consequence of low nitrogen availability is lower crop yields, which leads to lower organic matter input to the soil (Kätterer et al., 2012). Nitrogen depletion is therefore a threat to soil quality. ...
Thesis
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[The thesis is available for download here: https://pub.epsilon.slu.se/16426/ ] Use of mineral nitrogen fertilisers in crop cultivation has enabled substantial yield increases, strengthening global food security. High yields also allow better resource efficiency and result in higher organic matter inputs to soil, increasing the potential for soil carbon sequestration. However, nitrogen fertilisers cause substantial greenhouse gas emissions and nutrient losses to water bodies when the excess nitrogen leaves the field in reactive form. Thus nitrogen fertiliser can either increase or decrease the environmental impact of crop cultivation, depending on soil management, site characteristics and the aspects considered. Life cycle assessment (LCA) is a commonly used tool to assess the environmental impact of crop cultivation. In LCA, the impacts of all or part of the life cycle of a product, process or service are compiled. For crop cultivation, this generally includes production of inputs, machinery use and soil emissions. However, reactive nitrogen emissions, yield response and soil organic carbon dynamics are highly dependent on site conditions, relationships often poorly depicted in LCAs. This thesis examined the influence of nitrogen fertiliser rate and site on the climate impact and marine eutrophication of crop cultivation as determined by LCA. Methods for quantifying nitrogen emissions from crop cultivation and their impacts were compared, and new methods for assessing marine eutrophication impacts in Sweden and including soil fertility effects of yield increase were developed. The results showed that nitrogen fertiliser rate influenced the climate impact and marine eutrophication of crop cultivation, but that the effect of site was generally stronger. Site affected the two impact categories differently and also affected the nitrogen rate that gave the lowest impact. The level of impact and the effect of nitrogen rate and site also varied considerably with methodological choices, including: emissions models for soil nitrous oxide and nitrogen leaching, marine eutrophication characterisation model and accounting for the symbiotic relationship between yield and soil organic matter dynamics. These findings highlight the importance of careful model selection and interpretation of results when using LCA to assess the environmental impact of crop cultivation.
... Last but not least, plants with improved photosynthetic capabilities would also contribute to more carbon dioxide sequestration. Recent studies bring up the potential of enhancing crop-root relations to reduce greenhouse gas levels [183][184][185]. ...
Article
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One of the most important challenges facing current and future generations is how climate change and continuous population growth adversely affect food security. To address this, the food system needs a complete transformation where more is produced in non-optimal and space-limited areas while reducing negative environmental impacts. Fruits and vegetables, essential for human health, are high-value-added crops, which are grown in both greenhouses and open field environments. Here, we review potential practices to reduce the impact of climate variation and ecosystem damages on fruit and vegetable crop yield, as well as highlight current bottlenecks for indoor and outdoor agrosystems. To obtain sustainability, high-tech greenhouses are increasingly important and biotechnological means are becoming instrumental in designing the crops of tomorrow. We discuss key traits that need to be studied to improve agrosystem sustainability and fruit yield.
... Therefore, objectives to achieve, and sustain soil carbon sequestration will require tailoring to local conditions (c.f. Kätterer et al., 2012). ...
Preprint
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Soils have the potential to sequester and store significant amounts of carbon, contributing towards climate change mitigation. Soil carbon markets are now emerging to pay farmers for changes in land use or management that absorb carbon from the atmosphere, governed by codes that ensure additionality, permanence and non-leakage whilst protecting against unintentional reversals. This paper represents the first global comparative analysis of agricultural soil carbon codes, providing new insights into the wide range of approaches currently used to govern these emerging markets internationally. To do this, the paper first develops an analytical framework for the systematic comparison of codes, which could be applied to the analysis of codes in other land uses and habitats. This framework was then used to identify commonalities and differences in methods, projects, administration and commercialisation and associated code documents for 12 publicly available codes from the UK, France, Australia, USA and international bodies. Codes used a range of mechanisms to manage: additionality (including legal, adoption, financial viability and investment tests); uncertainty and risks around soil carbon sequestration (including minimum permanence periods, carbon buffers, contractual arrangements and/or insurance policies); leakage (including restriction of eligible practices and monitoring to subtract leakage from verified sequestration); baselines (including multi-year and variable buffers based on empirical data or models); measurement, reporting and verification methods (stipulating time intervals, methods, data sources and assessments of uncertainty); auditing; resale of carbon units; stakeholder engagement; and approaches to ensure market integrity (such as buyer checks). The paper concludes by discussing existing MRV methods and codes that could be adapted for use in the UK and evaluates the need for an over-arching standard for soil carbon codes in the UK, to which existing codes and other schemes already generating soil carbon credits could be assessed and benchmarked.
... In Northern Europe, dairy cow rations are typically based on grass silage due to the climatic conditions which favour grass production (Huhtanen et al. 2013, Virkajärvi et al. 2015. Forage-based feeding of dairy cows has many benefits as grass is natural, locally produced, does not compete directly with human edible foods and promotes carbon sequestration in low carbon content soils (Kätterer et al. 2013) so that grass dominated feeding has benefits both from ethical and environmental points of view. However, grass silage has typically been supplemented with substantial amounts of cereal-based concentrate feeds. ...
Article
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Two experiments were conducted under Northern European conditions to quantify dairy cow responses to variable grass silage quality and concentrate feed supplementation. Experiment 1 included 3 primary growth grass silages (early, intermediate and late maturity stage) supplemented with three concentrate levels (9, 12 and 15 kg d-1). Experiment 2 included three consecutive harvests (first, second and third harvest from the same sward within the growing season) and three levels of concentrate supplementation (9, 11 and 13 kg d-1). Dairy cows responded clearly to changes in the harvesting time of silage in primary growth (quadratic effect) and amount of concentrate (linear effect) in the diet in Experiment 1. Milk yield was the lowest with third harvest silage in Experiment 2, and responses to increasing concentrate allowance were linear. Interactions between silage quality and concentrate supplementation were detected in Experiment 1, where milk production responses to additional concentrate decreased with increasing silage digestibility. No interactions were found in Experiment 2, probably due to the small range of differences in nutritional quality between the silages prepared from different harvests. The results demonstrated that it is difficult to compensate for low silage digestibility by increasing the amount of concentrate. The variable ECM response (from –0.01 to 0.85 kg ECM per kg DM incremental concentrate in the diet) is explained by the concomitant decrease in silage intake and negative effect on diet neutral detergent fibre digestibility.
... The large amount of straw applied to the subsoil in treatment LS resulted in a significant increase (P < 0.05) in SOC content in spring and autumn 2017 and 2018 relative to the control and treatment L. This confirms previous findings that addition of straw increases SOC status in arable soil (Kätterer et al., 2012;Schjønning et al., 1994;Singh et al., 1998;Thomsen and Christensen, 2004). Total soil N accumulation followed a similar trend to SOC. ...
Article
Subsoil management needs to be integrated into the current tillage regimes in order to access additional resources of water and nutrients and sustain crop production. However, arable subsoil is often deficient in nutrients and carbon, and it is compacted, affecting root growth and yield. In this study, crop yield and soil responses to loosening of the upper subsoil, without and with straw injection below the plough layer (25–34 cm), were studied during three crop cycles (2016–2018) in a field experiment near Uppsala, Sweden. Responses to straw injection after loosening were studied after single and triple consecutive applications of 24–30 Mg ha⁻¹ during 2015–2017 to spring-sown barley and oats. Subsoil loosening combined with one-time or repeated straw addition (LS treatments) significantly reduced soil bulk density (BD) and increased porosity, soil organic carbon (SOC) and total nitrogen (N) compared with loosening (L) alone (one-time or repeated annually) and the control. In treatment L, the soil re-compacted over time to a similar level as in the control. Field inspections indicated higher abundance of earthworms and biopores in and close to straw incorporation strips. Aggregates readily crumbled/fragmented by hand and casts (fine crumbs) were frequently observed in earthworm burrows. The treatment LS improved soil properties (SOC and porosity) and water holding capacity, but had no significant influence on crop yield compared with the control. Crop yield in all treatments was 6.5–6.8 Mg ha⁻¹ in 2017 and 3.8–4.0 Mg ha⁻¹ in 2018, and differences were non-significant. Absence of yield effect due to treatments could be possibly due to other confounding factors buffering expression of treatment effects on yield. Lower relative chlorophyll content in leaves in the loosening with straw treatment during early growth stages, did not affect final crop yield. Subsoil loosening performed three times gave no further improvement in soil properties and grain yield compared with one-time loosening. There was no difference in yield between repeated subsoil loosening + straw and one-time treatment. It will be interesting to study the long-term effects of deep straw injection and evaluate its impact under other soil and weather conditions.
... The content and stock of SOC is driven by abiotic site factors such as climate and mineralogy (Doetterl et al., 2015), but also by carbon inputs (Kätterer et al., 2012). While climatic drivers are mostly relevant on larger scales, such as continents or regions with strong gradients (Hobley et al., 2015;Wiesmeier et al., 2013), geological, pedological, geomorphological or hydrological drivers can be of major importance at field to landscape scale (Doetterl et al., 2016;Hook & Burke, 2000). ...
Article
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Detecting changes in soil organic carbon (SOC) stock requires systematic and random sampling errors to be kept to a minimum. Especially in soil monitoring schemes based on soil profiles pits, it is important to understand if a minimum spatial shift of that profile pit during resampling could render resampling errors caused by spatial variability negligible. We aimed at (1) quantifying the random SOC stock error caused by a minimum shift in sampling location of one profile and (2) assessing whether an increase in the number of profile pits to three could significantly decrease the resampling error caused by spatial variability of the relevant parameters. Eight croplands and grasslands in northeast Germany were sampled. Three sampling designs were compared: one profile resampled (1) by one, (2) by three profiles or (3) three profiles resampled by three. In addition, 16 soil cores were taken per site to characterise overall plot‐scale heterogeneity and assess general patterns of spatial dependence of relevant parameters. Spatial dependence of all assessed parameters was weak. Accordingly, the resampling of one profile by one induced a high mean absolute error of 5.1 and 7.6 Mg C ha–1 at a 0–30 cm depth for croplands and grasslands (7.5% and 8.5%). This error was reduced by approximately 50% when three profiles were resampled by three profiles. Even with the smallest spatial shifts possible, monitoring of SOC stocks relies on replicated resampling to detect management or climate change‐induced trends in reasonable and relevant timescales.
... Particularly because they have an important and deep root system, and compared to aboveground biomass, root-derived C is about twice as efficient in the C input conversion into stable SOC. However, changes in the SOC occur slowly and become measurable only after longer periods (>5 to 10 years) [110,111]. ...
Article
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Soil compaction (SC) is a major threat for agriculture in Europe that affects many ecosystem functions, such as water and air circulation in soils, root growth, and crop production. Our objective was to present the results from five short-term (<5 years) case studies located along the north–south and east–west gradients and conducted within the SoilCare project using soil-improving cropping systems (SICSs) for mitigating topsoil and subsoil SC. Two study sites (SSs) focused on natural subsoil (˃25 cm) compaction using subsoiling tillage treatments to depths of 35 cm (Sweden) and 60 cm (Romania). The other SSs addressed both topsoil and subsoil SC (˃25 cm, Norway and United Kingdom; ˃30 cm, Italy) using deep-rooted bio-drilling crops and different tillage types or a combination of both. Each SS evaluated the effectiveness of the SICSs by measuring the soil physical properties, and we calculated SC indices. The SICSs showed promising results—for example, alfalfa in Norway showed good potential for alleviating SC (the subsoil density decreased from 1.69 to 1.45 g cm−1) and subsoiling at the Swedish SS improved root penetration into the subsoil by about 10 cm—but the effects of SICSs on yields were generally small. These case studies also reflected difficulties in implementing SICSs, some of which are under development, and we discuss methodological issues for measuring their effectiveness. There is a need for refining these SICSs and for evaluating their longer-term effect under a wider range of pedoclimatic conditions.
... Minasny et al. [5] surveyed farmland soil organic carbon (SOC) stock and sequestration potential in 20 regions across the world (e.g., Russia, Canada, China, America, and Australia) and reported that 4 per mille or even higher sequestration rates can be achieved under best management practices. Carbon sequestration in farmland soil improves soil fertility, thus increasing crop yield and ensuring food security [6][7][8][9]. It also affects regional and global carbon cycles by reducing greenhouse gas concentration, thus achieving the target of the Paris Climate Agreement to limit global warming to less than 2 • C [10][11][12]. ...
Article
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Farmland is one of the most important and active components of the soil carbon pool. Exploring the controlling factors of farmland soil organic carbon density (SOCD) and its sequestration rate (SOCDSR) is vital for improving carbon sequestration and addressing climate change. Present studies provide considerable attention to the impacts of natural factors and agricultural management on SOCD and SOCDSR. However, few of them focus on the interaction effects of environmental variables on SOCD and SOCDSR. Therefore, using 64 samples collected from 19 agricultural stations in China, this study explored the effects of natural factors, human activities, and their interactions on farmland SOCD and SOCDSR by using geographical detector methods. Results of geographical detectors showed that SOCD was associated with natural factors, including groundwater depth, soil type, clay content, mean annual temperature (MAT), and mean annual precipitation. SOCDSR was related to natural factors and agricultural management, including MAT, groundwater depth, fertilization, and their interactions. Interaction effects existed in all environmental variable pairs, and the explanatory power of interaction effects was often greater than that of the sum of two single variables. Specifically, the interaction effect of soil type and MAT explained 74.8% of the variation in SOCD, and further investigation revealed that SOCD was highest in Luvisols and was under a low MAT (
... Hal ini memperkuat dugaan adanya pengaruh aktivitas manusia yang berdampak pada peningkatan kandungan Corganik di kawasan ini. Kätterer et al. (2012) mengungkapkan bahwa limbah organik yang berasal dari aktivitas manusia dan peternakan berpengaruh signifikan meningkatkan kandungan C-organik dalam tanah/sedimen di suatu kawasan. ...
Article
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The blood clam, Tegillarca granosa (Linnaeus, 1758) is one of the economically important aquatic organisms. Therefore, information related to biometric conditions is crucial as preventive and responsive efforts to manage blood clams. This study aims to analyze the biometric condition of blood clams collected from the northern coast of Banda Aceh City. Blood-clam samples were collected from three locations, namely Alue Naga, Tibang, and Deah Raya. A total of 300 blood clams were observed. The biometric parameters included the distribution of length and weight classes, the relationship between length and weight, condition factors, ratios, and correlations between total weight, meat weight, and shell weight were measured. The results showed that the majority of blood clams found in Deah Raya were in the smaller length and weight classes (30-32 mm and 12,25-17,24 g) compared to those found in Alue Naga (33-35 mm and 17,25-22,24 g) and Tibang (42-44 mm and 22,25-27,24 g). Despite having identical growth patterns (negative allometric) and condition-factor values, the blood clams collected from Alue Naga had higher meat weight ratios than those collected from the other two locations. The correlation values between the weight of the meat and the total weight of the blood clams collected from Deah Raya tends to be lower than those of blood clams obtained from Alue Naga and Tibang, which are 0,55; 0,81; and 0,78, respectively. Keywords: biometric, environmental factor, Deah Raya
... We assumed a C concentration of 45% of the plant biomass [52]. Plant residue quality (biochemical composition), as one of the main drivers of decomposition, is represented in the RothC model by the DPM:RPM ratio (i.e., ratio of rapidly and slowly decomposing pools), which can be obtained by optimization to obtain the best fit according to different land use types. ...
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Temperate grassland soils store significant amounts of carbon (C). Estimating how much livestock grazing and manuring can influence grassland soil organic carbon (SOC) is key to improve greenhouse gas grassland budgets. The Rothamsted Carbon (RothC) model, although originally developed and parameterized to model the turnover of organic C in arable topsoil, has been widely used, with varied success, to estimate SOC changes in grassland under different climates, soils, and management conditions. In this paper, we hypothesise that RothC-based SOC predictions in managed grasslands under temperate moist climatic conditions can be improved by incorporating small modifications to the model based on existing field data from diverse experimental locations in Europe. For this, we described and evaluated changes at the level of: (1) the soil water function of RothC, (2) entry pools accounting for the degradability of the exogenous organic matter (EOM) applied (e.g., ruminant excreta), (3) the month-on-month change in the quality of C inputs coming from plant residues (i.e above-, below-ground plant residue and rhizodeposits), and (4) the livestock trampling effect (i.e., poaching damage) as a common problem in areas with higher annual precipitation. In order to evaluate the potential utility of these changes, we performed a simple sensitivity analysis and tested the model predictions against averaged data from four grassland experiments in Europe. Our evaluation showed that the default model’s performance was 78% and whereas some of the modifications seemed to improve RothC SOC predictions (model performance of 95% and 86% for soil water function and plant residues, respectively), others did not lead to any/or almost any improvement (model performance of 80 and 46% for the change in the C input quality and livestock trampling, respectively). We concluded that, whereas adding more complexity to the RothC model by adding the livestock trampling would actually not improve the model, adding the modified soil water function and plant residue components, and at a lesser extent residues quality, could improve predictability of the RothC in managed grasslands under temperate moist climatic conditions.
... In Europe, intensive agriculture using conventional approaches has led to severe land degradation, and more than 22% of European soils have been subject to soil erosion (Jones et al., 2012). Kätterer et al. (2012) indicated that extensive agriculture has affected the soil carbon balance and minimized the possibility of preserving soil carbon stocks in soils in northern Europe. Bongiorno et al. (2019) studied 10 long-term field experiments in different pedoclimatic conditions in Europe and concluded that soil organic carbon in the topsoil can be increased by minimizing agricultural activities (reducing tillage) associated with high OM inputs. ...
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en In Hungary, soil plays a fundamental role in agricultural production. The main aim of this research was to track the spatial–temporal variations in certain soil properties (soil organic carbon [So], pH, NO3⁻, P, K, Mn, Zn and Cu) between 2000 and 2010 in 55 different farms in the eastern part of Hungary (Hajdú-Bihar region). Soil data were collected from the Soil Conservation Information and Monitoring System. After 10 years of agricultural activities results reveal that the means of pH, So, NO3⁻, and Zn were higher in 2010 than in 2000. Indeed, of nine studied soil characteristics only two (So%, NO3⁻) showed a significant change according to the Wilcoxon T-test. The average pH_H2O increased by 0.13 and reached 7.31 ± 0.12 in 2010. The average NO3⁻ (ppm) increased by 4.75 ppm and reached 19.9 ppm in 2010. For other soil nutrients, available P, K and Mg decreased slightly, while Mn decreased from 269 ± 25 ppm to 236 ± 21 ppm in 2010. Interestingly, Zn and Cu showed no change between 2000 and 2010. However, the inverse distance weighting (IDW) showed that the central part of the study area is more prone to changes due to intensive agricultural activities. The output of this research could assist decision makers when making soil conservation plans within the study area. Résumé fr En Hongrie, le sol joue un rôle fondamental dans la production agricole. L'objectif principal de cette recherche était de suivre les variations spatio-temporelles de certaines propriétés du sol (carbone organique du sol [So], pH, NO3−, P, K, Mn, Zn et Cu) entre 2000 et 2010 dans 55 exploitations différentes dans la partie orientale de la Hongrie (région de Hajdú-Bihar). Les données sur les sols ont été collectées à partir du système d'information et de surveillance sur la conservation des sols. Après dix ans d'activités agricoles, les résultats révèlent que les moyennes de pH, So, NO3− et Zn étaient plus élevées en 2010 qu'en 2000. En effet, sur neuf caractéristiques du sol étudiées, deux seulement (So%, NO3−) ont montré un changement significatif au test Wilcoxon T. Le pH_H2O moyen a augmenté de 0.13 et a atteint 731 ± 0.12 en 2010. Le NO3− (ppm) moyen a augmenté de 4.75 ppm et atteint 19.9 ppm en 2010. Pour les autres éléments nutritifs du sol, P, K et Mg disponibles ont légèrement diminué, tandis que Mn a diminué de 269 ± 25 ppm à 236 ± 21 ppm en 2010. Fait intéressant, Zn et Cu n'ont montré aucun changement entre 2000 et 2010. Cependant, la pondération à distance inverse (IDW) a montré que la partie centrale de la zone d'étude est plus sujette aux changements dus à activités agricoles intensives. Les résultats de cette recherche pourraient aider les décideurs à élaborer des plans de conservation des sols dans la zone d'étude.
... In fact, inorganic fertilizers enhance soil humus formation. With increasing doses of nitrogen fertilizer, more roots and above-ground crop residues are produced, forming the raw material for creation of more soil organic matter (e.g., Kätterer et al., 2012;Poffenbarger et al., 2017;Powlson et al., 2011). Long-term field experiments have revealed that the level of soil organic matter is the result of the production level of an agroecosystem (Johnston et al., , 2017. ...
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This paper reviews the original reasons of the organic farming movement for excluding mineral (inorganic) fertilizers. In this paper, their theories and decision criteria for excluding use of inorganic fertilizers in crop production were revisited. Original reasons for banning inorganic fertilizers were subjected to scientific scrutiny, which was not possible when they were formulated 50–100 years ago due to limited knowledge of the soil-crop system. The original reasons were as follows: Rudolf Steiner, the founder of biodynamic farming, played down the physical role of plant nutrients and pointed out “flow of forces” as being most important for soils and crops. Eve Balfour and Albert Howard, founders of the Soil Association in England, claimed that inorganic fertilizer increases the breakdown of humus in soil, leading to a decline in soil fertility. Hans-Peter Rusch, the founder of biological organic farming, considered inorganic fertilizers to be imbalanced products not matching crop composition and not in synchrony with crop demand. When testing these historical statements as scientific hypotheses, older and modern scientific literature was used for validation. Steiner’s belief about the “flow of forces” has not be verified using current methodologies. The claim by Balfour and Howard that inorganic fertilizers accelerate soil organic matter decomposition is not substantiated by data from long-term field experiments on carbon and nitrogen cycling in soil-plant systems. The statement by Rusch that inorganic fertilizers supply crops inappropriately is difficult to uphold, as the composition, time, and rate of application and the placement of fertilizer in soil or on foliage can be fully adapted to crop requirements. In light of accumulated scientific evidence, the original arguments lack validity. The decision to ban inorganic fertilizers in organic farming is inconsistent with our current scientific understanding. Scientific stringency requires principles found to be erroneous to be abandoned.
... In long-term cropland fertilisation experiments, Kätterer et al. (2012) found that approximately 1 kg/ha of nitrogen fertiliser sequestered 1 kg/ha SOC within 4-5 decades, which they related to increased C inputs. Also Conant et al. (2001) found slightly positive fertilisation effects on grassland SOC, analysing results of 40 different studies. ...
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Grasslands are a major terrestrial ecosystem type and store large amounts of soil organic carbon (SOC) per unit area. Quantitative and mechanistic knowledge on the effects of management on SOC stocks in grasslands is limited. Also, climate change can be seen as an indirect anthropogenic threat to SOC stocks, with warming effects on grassland SOC being currently understudied. Here, several studies investigating the effects of management and warming on SOC stocks are summarised, with a central to northern European focus. SOC sequestration increased with management intensity, i.e. cutting frequency and mineral fertilisation, even without external C inputs. This was partly explicable by increased productivity in more intensively managed grasslands. In addition, the availability of nutrients was found to foster microbial anabolism, leading to a more efficient build‐up of SOC in fertilised as compared to unfertilised soils. Interestingly, the addition of 1 kg nitrogen as NPK fertiliser consistently led to approximately 1 kg of additional SOC. Sequestration of SOC might thus compensate for a major part of the increased greenhouse gas emissions associated with highly intensive grassland management. Including perennial grasses in agricultural crop rotations is multi‐beneficial and proved to be a very efficient measure to increase SOC stocks. At the same time, soil warming depleted SOC, both in natural subarctic as well as in managed temperate grasslands. Climate change can thus be expected to counterbalance efforts of SOC build‐up to some extent. Future research should focus on the interactive effects of climate change and management, which will be important for future management decisions.
... In soils with particularly high background levels of SOC, it is difficult to assess short (1-5 years) to medium-term (˃ 5-10 years) changes. It is therefore necessary to monitor changes in SOC due to different management practices over periods greater than 10 years (Kätterer and others 2012). This clearly demonstrates the importance of both long-term experiments and long-term monitoring networks. ...
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In this report, we review the scientific evidence base relating to carbon storage and sequestration by semi-natural habitats, in relation to their condition and/or management. This new report updates and expands previous work by Natural England on ‘Carbon storage by habitat’ published in 2012. We cover terrestrial, coastal and marine habitats, and the freshwater systems that connect them, in order to quantify their relative benefits for carbon management.
... It is widely acknowledged that farming practices can influence SOC levels to a certain extent (Freibauer et al. 2004). On field scale, SOC stocks are strongly correlated with the amount of C org input, which is the almost exclusive source of SOC (Kätterer et al. 2012). However, on a national scale, there are very few data available on the amount of C org input to agricultural soils. ...
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The quantity and quality of organic carbon (C org) input drive soil C org stocks and thus fertility and climate mitigation potential of soils. To estimate fluxes of C org as net primary production (NPP), exports, and inputs on German arable and grassland soils, we used field management data surveyed within the Agricultural Soil Inventory (n = 27.404 cases of sites multiplied by years). Further, we refined the concept of yield-based C org allocation coefficients and delivered a new regionalized method applicable for agricultural soils in Central Europe. Mean total NPP calculated for arable and grassland soils was 6.9 ± 2.3 and 5.9 ± 2.9 Mg C org ha-1 yr-1 , respectively, of which approximately half was exported. On average, total C org input calculated did not differ between arable (3.7 ± 1.8 Mg ha-1 yr-1) and grassland soils (3.7 ± 1.3 Mg ha-1 yr-1) but C org sources were different: Grasslands received 1.4 times more C org from root material than arable soils and we suggest that this difference in quality rather than quantity drives differences in soil C org stocks between land use systems. On arable soils, side products were exported in 43% of the site * years. Cover crops were cultivated in 11% of site * years and contributed on average 3% of the mean annual total NPP. Across arable crops, total NPP drove C org input (R 2 = 0.47) stronger than organic fertilization (R 2 = 0.11). Thus, maximizing plant growth enhances C org input to soil. Our results are reliable estimates of management related C org fluxes on agricultural soils in Germany.
... Agricultural soils are subject to diverse management interventions such as tillage, fertilization, liming, harvest, irrigation, drainage, and grazing, all of which have an impact on SOC stocks to some extent (Freibauer et al., 2004;Kä tterer et al., 2012;Paradelo et al., 2015). Furthermore, the global area of soils under agricultural production is huge and expected to increase (Ramankutty and Foley, 1999). ...
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Background: There is considerable uncertainty about the actual size of the global soil organic carbon (SOC) pool and its spatial distribution due to insufficient and heterogeneous data coverage. Aims: We aimed to assess the size of the German agricultural SOC stock and develop a stratification approach that could be used in national greenhouse gas reporting. Methods: Soils from a total of 3104 sites, comprising 2234 croplands, 820 permanent grasslands and 50 sites with permanent crops (vineyards, orchards) were sampled in a grid of 8 8 km to a depth of 100 cm in fixed depth increments. In addition, a decade of management data was recorded in a questionnaire completed by farmers. Two different approaches were used to stratify cropland and grassland mineral soils and derive homogeneous groups: stratification via soil type (pedogenesis) and via SOC-relevant soil properties. Results: A total of 146 soils were identified as organic soils, which stored by far the highest average SOC stock of 528 +/- 201 Mg ha-1 in 0-100 cm depth. Of the mineral soils, croplands and permanent crops stored on average 61 +/- 25 and 62 +/- 25 Mg ha-1 in 0-30 cm (topsoil) and 35 +/- 30 and 44 +/- 28 Mg ha-1 in 30-100 cm (subsoil), while permanent grasslands stored significantly more SOC (88 +/- 32 and 47 +/- 50 Mg ha-1 in topsoil and subsoil). Overall, topsoils stored 67 +/- 14% and subsoils 33 +/- 14% of total SOC stocks. Soil C:N ratio, clay content and groundwater level were major factors that explained the spatial variability of SOC stocks in mineral soils. Accordingly, Podzols, Gleysols and Vertisols were found to have the highest SOC stocks. Conclusions: Stratification via soil properties yielded the most comparable cropland and grassland strata and is thus preferable for estimating land-use change effects, e.g., for greenhouse gas inventories. In total, 2.5 Pg C are stored in the upper 100 cm of German agricultural soils, making them the largest organic carbon pool in terrestrial ecosystems of Germany. This bares a large responsibility for the agricultural sector and society as a whole to maintain and, if possible, enhance this pool.
... This feature is interesting from a global warming mitigation perspective Minx et al. 2018) and soil C sequestration through grass cultivation has been suggested as a negative emission technology with large potential (Tidåker et al. 2014;Yang et al. 2018). However, grass-ley systems have been reported to act differently depending on climate and soil properties (Soussana et al. 2010;Kätterer et al. 2012;Jackson et al. 2017). ...
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In this study, Life Cycle Assessment (LCA) methodology was combined with the agro-ecosystem model DNDC to assess the climate and eutrophication impacts of perennial grass cultivation at five different sites in Sweden. The system was evaluated for two fertilisation rates, 140 and 200 kg N ha −1. The climate impact showed large variation between the investigated sites. The largest contribution to the climate impact was through soil N 2 O emissions and emissions associated with mineral fertiliser manufacturing. The highest climate impact was predicted for the site with the highest clay and initial organic carbon content, while lower impacts were predicted for the sandy loam soils, due to low N 2 O emissions, and for the silty clay loam, due to high carbon sequestration rate. The highest eutrophication potential was estimated for the sandy loam soils, while the sites with finer soil texture had lower eutrophication potential. According to the results, soil properties and weather conditions were more important than fertilisation rate for the climate impact of the system assessed. It was concluded that agro-ecosystem models can add a spatial and temporal dimension to environmental impact assessment in agricultural LCA studies. The results could be used to assist policymakers in optimising use of agricultural land. ARTICLE HISTORY
... In spite of an increase in A horizon thickness, the stocks of C org in the soil of the unfertilised grassland decreased only by 0.87 t ha -1 , while in the soil of the fertilised grassland they increased by 5.40 t ha -1 , or 257 kg ha -1 yr -1 (Fig. 1B). This difference was determined by a better-developed root system and a larger aboveground mass in the soil fertilised with NPK fertilisers (Katterer et al., 2012;Lal, 2013). Fornara and Tilman (2008) suggest that C org accumulation in a grassland phytocenosis depends on the biomass of the root system, and the combination of the main grasses and legumes (C 4 -type plants) facilitates its accumulation increase in the soil. ...
... By virtue of the huge amount of soil C and N stock (Lal, 2004), agroecosystems represent important potential leverage points to manage global climate change (Davis et al., 2016;Kätterer et al., 2012;Myers et al., 2017). Even small reductions in soil C stock can significantly increase atmospheric CO 2 concentration and hasten climate change (Schmidt et al., 2011), which could directly or indirectly threaten the sustainability of agroecosystems (Müller et al., 2011;Schlenker and Roberts, 2009). ...
Article
To meet the growing challenges for food security, renewable resource production and climate change adaptation, optimized crop rotations (OCRs) should aim to maximize biomass production and export from the field while minimizing carbon (C) and nitrogen (N) footprints. However, the effects of OCRs on aboveground biomass production and soil C and N stock as well as the potential links between them remain poorly understood. In this study in Denmark, we harvested all aboveground biomass and simultaneously investigated soil C and N content and stock in two continuous monocultures (CMs) as well as in four OCRs. Across five-year continuous observations, OCRs significantly increased cumulative aboveground biomass production by 23% compared to CMs. There was no significant difference between OCRs and CMs in soil C and N content in any of the soil layers (0–20, 20–50, and 50–100 cm) after the five years. Moreover, OCRs had no effect on top layer soil C and N stock compared to CMs, even when examined by equivalent soil mass. Slight reductions in soil C and N stock after five years in both OCRs and CMs did not relate to the changes in aboveground biomass production. Our results highlight that it is feasible to produce more biomass for biorefineries in OCRs than in CMs and the reductions in soil C and N stock over time seem similar for the two systems. Longer-term continuous observations are called for to underpin these results.
... Additionally, adaptations of region-specific management practices to help SOC-sequestration and mitigate GHGs emissions with prevention of land-use change could be helpful. Lay-arable cropping system (a practice of leaving the land as fallow or grassed for live-stock production in between 10 and 15 years of crop rotation) than mono-cropping system and application of organic amendments including household compost with application of a small amount of nitrogen could help increase the SF and C stock (Kätterer et al. 2012). ...
Article
Forage and grazing (FG) systems can store a substantial amount of soil organic carbon (SOC) under appropriate land use management and reduce atmospheric CO2 concentrations. Increasing SOC levels along with many interlinked ecosystem services are essential for increased productivity and sustainability of FG lands (FGLs). Although adoption of improved management practices (MPs) that support SOC sequestration (SOCq) is necessary, clear understandings of challenges and opportunities which are sometimes unique to individual FGLs, are also important for implementation of MPs. The objective of this forum paper is to explore the latest scientific knowledge on opportunities to address major challenges for increasing SOCq in FGLs. In intensively managed FGLs where the goal is often to maximize yields, lands are heavily fertilized and thus, usually drive towards SOC loss. Diversifications of both forage and grazing species along with strategic grazing plans have been proven as effective MPs for increasing SOCq. However, challenge of maintaining productivity levels still remains. Implementing improved grazing for nutrient cycling and integrating forage diversification for increased biodiversity are found to improve soil health attributes, which are critical for SOCq. However, to achieve this, we also need to consider site- and soil- specific factors. Extreme climatic events which often lead to decline in soil fertility status, SOCq and overall productivity of FGL systems. To address these challenges, uses of models to simulate the FGL systems and have definite choices of suitable MPs are helpful. However, we must be able to have access of wide range of datasets to develop system-level adaption-strategies which are effective to mitigate these adverse effects. Ultimately, participatory researches with novel views and improved perceptions based on the value of SOCq and long-term benefits of implementation of best MPs, developing education and outreach materials to enrich the producers’ knowledge gaps are helpful for climate resilient FGL systems.
... For example, on sandy soils in Denmark, Eriksen and Jensen (2001) measured C losses from cultivated swards (up to 2.6 t C ha -1 for the first 3 months after cultivation) about twice the emissions from the untilled pasture in the same period. Over the long term, higher SOM contents are seen under ley-arable rotations compared with continuous arable cropping (Haynes, 1999;Soussana et al., 2004;Kätterer et al., 2012;Christensen et al., 2009;Johnston et al., 2017). Due to the impact of periodic cultivation, the SOM accumulation in ley-arable soils is less than in permanent grasslands (Recous et al., 1997;Johnston et al., 2009). ...
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The short scoping project (September 2018-March 2019) took an integrated multidisciplinary approach including literature review, interviews and a stakeholder workshop to describe the likely economic, social and environment impacts of the integration of livestock into arable production systems in predominantly arable areas of the UK. • There is no single model for the integration of livestock into arable systems; the most appropriate model will depend on the need/driver within the arable system and the system context (e.g. soil type, climate, proximity of other livestock enterprises). • The main challenge for implementation by farm businesses is the potential negative impact on short-term profitability for the arable farm and uncertainty for livestock producers, coupled with the need for capital investment. • Three further challenges for on-farm adoption were also identified: o lack of skills / knowledge for livestock husbandry, in arable areas; o need to develop new trusting relationships (and formal agreements) between livestock and arable producers; o limited evidence of the most effective route to deliver the greatest benefit over cost for both arable and livestock producers and also in the delivery of public goods. • The study suggests that the integration of leys into all-arable rotations will support sustained/improved productivity and also delivery of a number of key Government policies through reduced GHG emissions, improved soil health, reduced risk of diffuse pollution and improved landscape biodiversity in the short-medium term. • Integration of leys into arable rotations extends the rotation and consequently increases land use diversity with potential benefits for biodiversity. • Soil organic matter and soil structure are improved in ley-arable rotations with a consequent reduction in diffuse pollution risk and C sequestration over a 20-30 year timescale. However, the benefit for GHG balance may be more than offset by an increase in methane emissions from ruminant livestock used for grazing. • There is no expected increase in market for livestock products and hence any increase in livestock production in predominantly arable areas will result in changes in livestock numbers and possibly the structure of livestock production in the west and the uplands. • We recommend a focussed desk study to determine whether integration of ley into all-arable systems leads to an overall reduction in GHG, ammonia, nitrate and sediment losses for the same level of production (thus improving resource use efficiency) or whether part of the load simply shifts from livestock farms to arable farms. • Building on the SIP and other networking approaches already in place, there is an opportunity to implement an integrated study of N (and P) use efficiency at rotational scale to inform discussions about the role of agriculture within the circular economy by combining focussed site-specific data collection and research experiments with a wider network of on-farm monitoring. • In collaboration with the industry, more work is needed to support the development of mechanisms to identify the most effective potential collaborations and then to overcome any tension between the interests of the grazier and the land owner, and between these and societal benefits that might arise from integrating grazed leys into arable rotations.
... Crop residues can either be completely removed from fields or they can be returned to the field directly or indirectly. The removal of crop residues would result in loss of carbon (Kätterer et al. 2012) therefore the utilization of crop residues will determine the extent of carbon sequestration due to the primary source of carbon constituting 40% of the total dry biomass therefore having the highest carbon sequestration potential (1.2-1.9 t C/ha/year) (Freibauer et al. 2004) hence, crop residue addition is related to its C input ability and soil retention time (Lugato et al. 2006). Kätterer et al. (2011) examined the stability of various soil amendments and, found that only 17% of crop residues retained in the soil after 50 years while farmyard manure (32%) and sewage sludge (54%) was present in the soil. ...
... The processes of carbon sequestration, carbon storage as soil organic matter, and fluxes of greenhouse gases in grasslands are intimately linked to each other. It is well established that carbon sequestration increases when grassland management is intensified by increased nutrient inputs, especially nitrogen (e.g., K€ atterer et al. 2012K€ atterer et al. , He et al. 2013). However, the climate mitigation effect of intensified management may be offset by increased emissions of greenhouse gases other than CO 2 (see below). ...
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Extensively managed grasslands are recognized globally for their high biodiversity and their social and cultural values. However, their capacity to deliver multiple ecosystem services (ES) as parts of agricultural systems is surprisingly understudied compared to other production systems. We undertook a comprehensive overview of ES provided by natural and semi‐natural grasslands, using southern Africa (SA) and northwest Europe as case studies, respectively. We show that these grasslands can supply additional non‐agricultural services, such as water supply and flow regulation, carbon storage, erosion control, climate mitigation, pollination, and cultural ES. While demand for ecosystems services seems to balance supply in natural grasslands of SA, the smaller areas of semi‐natural grasslands in Europe appear to not meet the demand for many services. We identified three bundles of related ES from grasslands: water ES including fodder production, cultural ES connected to livestock production, and population‐based regulating services (e.g., pollination and biological control), which also linked to biodiversity. Greenhouse gas emission mitigation seemed unrelated to the three bundles. The similarities among the bundles in SA and northwestern Europe suggest that there are generalities in ES relations among natural and semi‐natural grassland areas. We assessed trade‐offs and synergies among services in relation to management practices and found that although some trade‐offs are inevitable, appropriate management may create synergies and avoid trade‐offs among many services. We argue that ecosystem service and food security research and policy should give higher priority to how grasslands can be managed for fodder and meat production alongside other ES. By integrating grasslands into agricultural production systems and land‐use decisions locally and regionally, their potential to contribute to functional landscapes and to food security and sustainable livelihoods can be greatly enhanced.
... Increased plant biomass following fertilisation tends to result in greater carbon inputs to the soil, with associated positive effects on SOC stocks (Kätterer et al., 2012). Furthermore, organic fertilizer application is an additional source of carbon input, leading to increased SOC stocks. ...
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These guidelines aim to give a harmonised, international approach for estimating soil organic carbon (SOC) stock and stock changes in livestock production systems. Despite the attention given to SOC, current knowledge remains limited regarding SOC baselines and changes, the detection of vulnerable hot spots for SOC losses and opportunities for SOC gains under both climate and land management changes. Accurate baselines are still missing for many countries and estimates of carbon uxes due to changes in SOC stocks in the global carbon cycle are associated with large uncertainties. Global SOC stocks estimates do exist, but there is high variability in reported values among authors, caused by the diversity of data sources and methodologies.
... A more detailed understanding of ecosystem responses to shifts in nutrient regime is necessary in order to include key nutrient-triggered mechanisms in soil C models (Poeplau, 2016). Across ecosystems, the increase in N availability is often associated with an increase in SOC stocks (Kätterer et al., 2012), while the opposite has also been reported (Waldrop et al., 2004;Khan et al., 2007), stoking the ongoing scientific debate about the role of N in C cycling (Neff et al., 2002;Craine et al., 2007). Plant growth is generally N limited (Vitousek and Farrington, 1997). ...
Article
Ecosystem responses to nitrogen (N) additions are manifold and complex, and also affect the carbon (C) cycle. It has been suggested that increased microbial carbon use efficiency (CUE), i.e. growth per C uptake, due to higher N availability potentially increases the stabilization rates of organic inputs to the soil. However, evidence for a direct link between altered microbial anabolism and soil organic C (SOC) stocks is lacking. In this study, unfertilized (control) and NPK-fertilized (NPK) treatments of seven temperate grassland experiments were used to test the hypothesis that fertilizer-induced differences in SOC stocks (ΔSOC) cannot be explained by differences in C input alone, but that microbial anabolism plays an important role in C sequestration. At two experimental sites, microbial CUE and related metabolic parameters was determined using an ¹⁸O labeling approach at two different incubation temperatures (10 °C and 20 °C). Fertilization effects on the abundance of Bacteria, Archaea and Fungi were also determined using quantitative PCR targeting the respective rRNA genes. Due to the availability of yield and belowground biomass data, the introductory carbon balance model (ICBM) could be used for all seven sites to estimate the contribution of C input to ΔSOC. A significantly higher microbial growth (+102 ± 6%), lower specific respiration (−16 ± 7%) and thus significantly higher CUE (+53 ± 21%) was found for the NPK treatments, which was consistent across experiments and incubation temperatures and correlated with measured root C:N ratios. Growth (+49 ± 5%) and respiration (+70 ± 9%) were increased by a higher incubation temperature, but this was not the case for CUE. The fungi to bacteria ratio changed significantly from 0.18 ± 0.02 (control) to 0.09 ± 0.02 (NPK). On average, only 77% (51% when excluding one extreme site) of observed ΔSOC was explained by C inputs. The optimized humification coefficient h of the model used to fit the observed ΔSOC was strongly correlated to differences in the root C:N ratio between the control and NPK treatments (R² = 0.71), thus confirming a link between microbial anabolism and substrate C:N ratio. Furthermore, varying h directly by observed differences in CUE improved the model fit at the two sites investigated. This study provides direct evidence that CUE of soil microbial communities is relevant for SOC sequestration, and its dependency on soil N availability or substrate C:N ratio might allow for its inclusion in models without explicit microbial C pools.
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Soils have the potential to sequester and store significant amounts of carbon, contributing towards climate change mitigation. Soil carbon markets are emerging to pay farmers for management changes that absorb atmospheric carbon, governed by codes that ensure eligibility, additionality and permanence whilst protecting against leakage and reversals. This paper presents the first global comparative analysis of farmland soil carbon codes, providing new insights into the range of approaches governing this global marketplace. To do this, the paper developed an analytical framework for the systematic comparison of codes which was used to identify commonalities and differences in approaches, methods, administration, commercialisation and operations for 12 publicly available codes from around the world. Codes used a range of mechanisms to manage additionality, uncertainty and risks, baselines, measurement, reporting and verification, auditing, resale of carbon units, bundling and stacking, stakeholder engagement and market integrity. The paper concludes by discussing existing approaches and codes that could be adapted for use in the UK and evaluates the need for an over-arching standard for soil carbon codes in the UK and internationally, to which existing codes and other schemes already generating soil carbon credits could be assessed and benchmarked.
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Soil organic matter (SOM) is important in maintaining soil fertility and other ecosystem functions. Yet, land management in intensive agriculture has caused SOM level to decrease, with knock-on effects for soil fertility and quality. Therefore, land management options that ensure that SOM is not depleted and that soil functions are better sustained are of increasing interest. However, there is limited knowledge on how different land managements affect the composition of SOM and associated microbial functional profiles. Twelve long-term field experiments, covering a wide range of climatic zones and soil types, were selected in Sweden. They focused on the role of combining ley in crop rotations with the manure application (livestock farm), as opposed to the management without ley and receiving only inorganic fertilizer (arable farm). In ten out of the 12 study sites, livestock farm management tended to have higher proportions of aliphatic and double bonded C groups, as estimated by mid-infrared spectroscopy. This was further confirmed by 13C NMR analysis, which found greater proportions of O-alkyl and di-O-alkyl groups and less aromatic C in livestock farm than arable farm management in five of the eight sites analyzed. The changes in SOM composition were reflected in microbial functional profiles across many sites: soils from livestock farm management utilized more carbohydrates and amino acids, while polymer and aromatic compounds were associated with arable farm management. Overall, shifts in both microbial functional profiles and SOM composition showed great consistency across geographical and climatic zones. Livestock farm management maintained higher levels of microbial functional diversity and were associated with higher proportions of “reactive” C functional groups. Our investigation demonstrates that livestock farm management could maintain soil fertility over the long-term via the changes in SOM composition and the regulation of microbial functional profiles.
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The soil carbon (C) stock is comprised of the soil inorganic carbon (SIC) and the soil organic carbon (SOC) stock. A site-specific steady state equilibrium soil C stock evolves under natural conditions depending on the balance between soil C inputs (plant residues) and losses (decomposition, erosion, leaching). The SIC stock is perceived as being less dynamic than the SOC stock with uncertain effects of organic agriculture (OA) on SIC sequestration rate, and not the focus of agricultural soil and land-use management. In contrast, the SOC stock receives increasing attention due to its importance for the global climate and soil health. However, increases in the SOC stock may also alter the greenhouse gas (GHG) balance and this must be addressed in the assessment of soil C sequestration practices to mitigate climate change. The historical loss of SOC due to the conversion of natural ecosystems to agroecosystems provides an opportunity to use soil and land-use management practices to partially replenish lost SOC stocks. Topsoil (0–15 cm depth) SOC stocks have been shown to increase under OA management by 1.98–3.50 Mg C ha−1 compared to nonorganic management. But the addition of exogenous C (e.g., with manure) for this improvement and SOC sequestration for climate change adaptation and mitigation may be important. Compared to nonorganic management, topsoil SOC sequestration rates did either not differ or were 0.29–0.45 Mg C ha−1 year−1 higher under OA, respectively. However, assessments of SOC sequestration and stocks for the entire rooted soil profile are scanty but needed to fully address long-term effects of agricultural management on SOC. Lower primary soil C inputs due to lower OA yields and higher losses by tillage compared to conventional no-tillage (NT) system may result in lower steady state equilibrium SOC stocks in OA systems. There is some evidence that root C allocation is higher under OA than that under nonorganic management. More agricultural soils will be managed in the future by OA driven by increasing consumer demand. The net effects of increased soil and land-use management for OA on the global soil C stocks must be critically assessed also in relation to long-term field experiments to support the design of climate-smart and climate resilient agroecosystems. Therefore, the objectives of this chapter are to describe in detail what processes and practices result in changes in SIC and SOC stocks and sequestration in soils under OA management.
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In nature, carbon plays an important role in the circulation of organic matter in the soil-plant-atmosphere system. To understand the full picture of the farming system impact on carbon dioxide emissions, long-term stationary experiments are needed, which will reduce the influence of weather conditions on changes in organic carbon stocks in soils and develop an optimal model of the crop cultivation system considering the positive balance of organic carbon in soils. The research was carried out from 1995 to 2020 in the grain crop rotation at the station of the Department of Soil Science and Agrochemistry of the SAU of the Northern Trans-Urals, near vil. Utyashevo in the Tyumen region. Purpose. The purpose of the research was to establish the effect of increasing doses of mineral fertilizers on the intake and fixation of organic carbon with plant residues in the grain agrophytocenosis in the conditions of the forest-steppe zone of the Trans-Urals. The refusal to use mineral fertilizers leads to annual losses of organic carbon in the form of CO 2 up to 0.6 t/ha. The use of high doses of mineral fertilizers for the planned yield of 5.0 and 6.0 t/ha of grain annually increases the emission of CO 2 by 0.4-0.6 t/ha per year. In these variants, the carbon received from plant residues is not fixed in the soil. A positive balance of organic carbon is provided only by the use of doses of mineral fertilizers for the planned yield of 3.0 and 4.0 t/ha of grain, which annually increases the carbon stock in the soil by 0.4-0.6 t/ha, and up to 14-21% is fixed from the incoming organic carbon in the form of plant residues in the soil.
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The use of 4R practices to manage nutrients is critical to support crop photosynthesis and make soil carbon storage an effective proposition for greenhouse gas mitigation. What is required is a delicate balancing act. Increasing primary productivity, reducing wastes, selecting climate‐smart sources, and using inhibitors of N2O emissions are all critical. The strong role of N in the multiple mechanisms of soil C storage underscores the need for integrated consideration of 4R nutrient management in programs that address both the emissions and sinks associated with cropping systems while keeping them productive. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.
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Predicting the regional net greenhouse gas emissions (Net GHG) of grasslands is increasingly important, as these are one of the most globally widespread vegetation types, providing several ecosystem services. In this study, we assessed the regional soil organic carbon (SOC) change over a 30-year period (1981–2010), and the annual GHG balance for 405,000 ha of moist temperate Spanish grassland associated with dairy cow production. To do this we used the following: (i) an integrated modelling framework comprising geographic information systems (GIS); (ii) the RothC model to simulate SOC changes in managed grasslands under moist temperate conditions; and (iii) Tier 2 recent IPCC methods to estimate emissions. The results showed an average regional SOC change rate of 0.16 Mg C ha⁻¹ year⁻¹, associated with the initial SOC and livestock density. The annual GHG balance was positive, contributing to global warming by 5.6 Mg CO2-e ha⁻¹ year⁻¹. Livestock density was the main factor affecting net GHG emissions in the grasslands associated with dairy production in northern Spain. We determined a livestock density threshold of 0.95 LU ha⁻¹, below which there is no SOC accumulation, and a threshold of approximately 0.4 LU ha⁻¹, above which net GHG per livestock unit (LU) are reduced. In conclusion, our study confirms the importance of dairy cow grazing systems in preserving and/or enhancing SOC stocks in the grasslands of northern Spain. It is therefore crucial to optimise the livestock density considering large variety of feed intake and alternative manure management mitigation options to reduce the net GHG emissions.
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Frequent cultivation is often used to control weeds in crops such as lettuce. The efficacy of this technique on weed populations has been evaluated, but the effect on weed emergence and seedbanks is less documented. Studies in mineral soil indicate that soil disturbance can increase both weed emergence and seed persistence depending on where seeds are redistributed in the soil profile. Evaluations done in muck soil are scarce. This study evaluated the effect of two and four repetitive shallow (3.4 to 7.1 cm deep) cultivations on weed emergence and the weed seedbank in muck soil. Cultivation treatments (0, 2 and 4 cultivations using a inter-row rototiller) were done in lettuce plots from 2017 to 2019. Weed density was evaluated by species before each cultivation date and after crop harvest. Viable seedbanks were evaluated by collecting soil samples before and after each growing season and placing them in greenhouse flats. Statistical analyses were based on mixed models. Results showed that shallow cultivation modified the emergence patterns of weeds but did not reduce total emergence during the subsequent years or viable seedbanks. After two seasons without seed inputs, total emergence was reduced by 46.6% and the seedbank was reduced by 31.7% regardless of the cultivation treatment. However, the seedbank of the very abundant common purslane ( Portulaca oleracea ) remained high.
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Organischer Bodenkohlenstoff (SOC) ist der größte terrestrische Kohlenstoff (C)-Pool, welcher ein Vielfaches des gesamten atmosphären C speichert. Landwirtschaftliche Nutzung von Böden hat einen starken Einfluß auf diesen Speicher und so auch auf C-Flüsse zwischen Atmosphäre und Biosphäre. Historsich haben Landnutzungsänderungen zu starken CO2-Emissionen aus Böden geführt, was auch einen signifikanten Einfluß auf die globale Erwärmung hatte. Diese kumulative Habilitationsschrift fokusiert auf zwei Haupteinflüsse des Menschen auf SOC: Landnutzung und globale Erwärmung durch Treibhausgasemisionen. Beide sind mit der globalen Ausbreitung des Menschen und der sprunghaften Entwicklung dessen Aktivität auf Erden stark angestiegen und werden somit als spezifisch für das „Anthropozän“ erachtet, welches hier als Synonym für jene Periode in der Weltgeschichte benutzt wird, in der menschliche Aktivität irreversible Spuren hinterlassen hat.. Durch die große Bedeutung von SOC und dessen Management für den Klimawandel, aber auch für Bodenfruchtbarkeit und Resilienz von Ökosystemen, ist es wichtig zu verstehen, i) welche Management-Optionen SOC erhalten und vermehren können ii) welche Mechanismen zu dessen Verlust und Stabilisierung führen, iii) wie die globale Nettoprimärproduktion auf möglichst nachhaltige und klimafreundliche Weise genutzt werden kann und iv) wie die globale Erwärmung C-Vorräte im Boden beeinflussen wird. Zusammen mit einigen methodischen Aspekten, welche zu einer verbesserten Messung, Berechnung und Modellierung von SOC beitragen sollen, bilden jene Themenomplexe den wissenschaftlichen Fokus dieser Arbeit.
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The objectives of this study across the highlands of Ethiopia were: (i) to characterize the association between soil organic carbon (SOC) stocks and biophysical variables and (ii) to model and map attainable SOC sequestration associated with five improved land management practices. The spatial distribution of the SOC stock was studied using a multiple linear regression model driven by eight biophysical predictors. A widely used SOC model (RothC) was then used to model changes in SOC over the next 20–50 years of improved land management. Simulations were driven by the derived SOC stocks, pH and clay contents that are available in the ISRIC soils database at 250 m resolution and climate data from the “Enhancing National Climate Services Initiative” database. Organic carbon inputs to the model were estimated from the “Improved Crop Varieties Yield Register” of the Ministry of Agriculture and Livestock Resource and the Central Statistics Authority. After 50 years of conservation tillage with 80% of available manure applied to cultivated land, the total SOC stock increased by 169,182,174 t, which is 2.8 times higher than the stock increase with only 50% of available manure applied. Introduction of improved pasture species and measures to control soil erosion was an important source of net carbon sequestration in grasslands. Afforestation and reforestation of degraded landscapes and protection of natural ecosystems further increased soil carbon. This highlights the importance of improved land management practices to SOC sequestration, which in turn could enhance agricultural productivity, food security and sustainable development.
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Understanding interactions between complex human and natural systems involved in urban carbon cycling is important when balancing the dual goals of urban development to accommodate a growing population, while also achieving urban carbon neutrality. This study develops a systems breakdown accounting method to assess the urban carbon cycle. The method facilitates greater understanding of the complex interactions within and between systems involved in this cycle, in order to identify ways in which humans can adapt their interactions to reduce net greenhouse gas emissions from urban regions. Testing the systems breakdown accounting method in Stockholm County, Sweden, we find that it provides new insights into the carbon interactions with urban green-blue areas in the region. Results show how Stockholm County can reduce its emissions and achieve its goal of local carbon net-neutrality, if the green areas protect its carbon sequestration potential and maintain it to offset projected remaining active emissions. Results also show that the inland surface waters and inner archipelago waters within Stockholm County are a considerable source of greenhouse gases to the atmosphere. A better understanding of these water emissions is necessary to formulate effective planning and policy measures that can reduce urban emissions. The insights gained from this study can also be applied in other regions. In particular, water bodies could play a significant role in the urban carbon cycle and using this knowledge for more complete carbon accounting, and a better understanding of green-blue interactions could help to reduce net urban emissions in many places.
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Long-term field trials are essential for monitoring the effects of sustainable land management strategies for adaptation and mitigation to climate change. The influence of more than thirty years of different management is analyzed on extensive crops under three tillage systems, conventional tillage (CT), minimum tillage (MT), and no-tillage (NT), and with two crop rotations, monoculture winter-wheat (Triticum aestivum L.) and wheat-vetch (Triticum aestivum L.-Vicia sativa L.), widely present in the center of Spain. The soil under NT experienced the largest change in organic carbon (SOC) sequestration, macroaggregate stability, and bulk density. In the MT and NT treatments, SOC content was still increasing after 32 years, being 26.5 and 32.2 Mg ha−1, respectively, compared to 20.8 Mg ha−1 in CT. The SOC stratification (ratio of SOC at the topsoil/SOC at the layer underneath), an indicator of soil conservation, increased with decreasing tillage intensity (2.32, 1.36, and 1.01 for NT, MT, and CT respectively). Tillage intensity affected the majority of soil parameters, except the water stable aggregates, infiltration, and porosity. The NT treatment increased available water, but only in monocropping. More water was retained at the permanent wilting point in NT treatments, which can be a disadvantage in dry periods of these edaphoclimatic conditions.
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Temperate grasslands are of paramount importance in terms of soil organic carbon (SOC) dynamics. Globally, research on SOC dynamics has largely focused on forests, croplands and natural grasslands, while intensively managed grasslands has received much less attention. In this regard, we aimed to improve the prediction of SOC dynamics in managed grasslands under humid temperate regions. In order to do so, we modified and recalibrated the SOC model RothC, originally developed to model the turnover of SOC in arable topsoils, which requires limited amount of readily available input data. The modifications proposed for the RothC are: (1) water content up to saturation conditions in the soil water function of RothC to fit the humid temperate climatic conditions, (2) entry pools that account for particularity of exogenous organic matter (EOM) applied (e.g., ruminant excreta), (3) annual variation in the carbon inputs derived from plant residues considering both above- and below-ground plant residue and rhizodeposits components as well as their quality, and (4) the livestock treading effect (i.e., poaching damage) as a common problem in humid areas with higher annual precipitation. In the paper, we describe the basis of these modifications, carry out a simple sensitivity analysis and validate predictions against data from existing field experiments from four sites in Europe. Model performance showed that modified RothC reasonably captures well the different modifications. However, the model seems to be more sensitive to soil moisture and plant residues modifications than to the other modifications. The applied changes in RothC model could be appropriate to simulate both farm and regional SOC dynamics from managed grassland-based systems under humid temperate conditions.
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Anthropogenic activities and atmospheric deposition have increased the nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which can significantly alter ecosystem carbon cycling. To better understand the mechanisms of soil organic carbon (SOC) responding to nutrient fertilization, we measured physical fractions (by particle-size fractionation) and chemical composition (by solid-state ¹³C NMR spectroscopy) of SOC, plant biomass and nutrient concentration, soil chemistry, microbial biomass and community composition after 10 years of N and P addition in an alpine meadow on the Tibetan Plateau. Our results showed that total SOC and mineral-associated organic carbon (MAOC) contents were not affected by N and P addition. However, P addition promoted particulate organic carbon (POC), which was likely attributed to hampered decomposition by lower microbial biomass (particularly fungi). In contrast, N addition did not change POC, probably because more plant biomass inputs were offset by faster decomposition of higher-quality plant litter (lower C:N ratio). Moreover, N addition rather than P addition decreased the percentage of labile functional group of O-alkyl C, whereas slightly increased alkyl-aromatic C:O-alkyl C ratio. These changes in SOC chemical composition with N inputs were likely caused by enhanced labile OM decomposition and rhizodeposit inputs. Overall, our results suggest that long-term exogenous N input could potentially accelerate SOM decomposition indicated by the chemical composition, but P input could result in inhibition of SOM decomposition and accumulation of POC stock in the alpine meadow ecosystem.
Technical Report
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This climate roadmap was made by Natural Resources Institute Finland (Luke) for the Central union of agricultural producers and forest owners (MTK; www.mtk.fi) and the Central union Swedish speaking agricultural producers in Finland (SLC; www.slc.fi). Finnish agriculture produced a total of about 16 Mt CO2 eq. greenhouse gas emissions (GHG emissions) 2018. The road to a significant reduction in greenhouse gas emissions requires large-scale measures to reduce emissions from peatlands, increase carbon sequestration in mineral land, and changes in the use and production of energy in agriculture. These changes require new guidance and incentives for farmers, whose main task will continue to be to produce domestic food that meets consumer needs and preferences to about the same extent as in recent years. Efforts are being made to improve the sustainability of agricultural production in all respects, including profitability. The potential of agriculture to reduce greenhouse gas emissions varies widely. The implementation of significant reductions must therefore be carefully planned and implemented in different ways, so that all farmers can apply appropriate measures in cooperation with other farmers and operators. According to producer organizations, domestic demand for food and agricultural products will not change significantly until 2035. Consumption of red meat, i.e. beef and pork, however, will decrease by about 20% and at the same time the domestic consumption of poultry meat will increase by 20%. Total demand for milk and various dairy products will decrease by about 10-15% by 2035. Domestic production will change at almost the same rate as these changes in demand, although favorable export trends may keep domestic consumption production at a higher level than domestic consumption. Demand for domestically produced legumes for feed and food is growing, as is demand for oats. In the base scenario (WEM scenario; current policy instruments and trends in agriculture), greenhouse gas emissions will be reduced by only 5% by 2035 (6% by 2050). This means less than 1 Mt CO2 eq. The base scenario assumes minor changes to the current situation in the agricultural markets and no changes in agricultural land use from 2018, or controls that affect it. Five percent reduction in emissions until 2035 is due to a slow reduction in the number of cattle, with agricultural production and land use largely unchanged. The WAM scenarios (WAM1 and WAM2) are more ambitious and contain more measures to reduce GHG emissions than the baseline scenario. The WAM scenarios seek further reductions in greenhouse gas emissions from cultivated peatlands, increased carbon sequestration in mineral land and more biogas and solar energy in agriculture. These involve many measures in peatlands, such as less cultivation of annual plants, controlled underground drainage (higher water level than normal, e.g. 30 cm), restoration of peatlands with high water level (0-10 cm) and cultivation of wetlands. High water levels effectively reduce greenhouse gas emissions. In the WAM scenarios, the harvested crop yields will increase by 10% by 2035 and by more than 15% by 2050, especially through new plant varieties and their appropriate cultivation and precise use of production inputs. Higher yields can also be achieved by improving agricultural conditions through more diversified crop rotation and increased soil organic matter. The use of arable land will change significantly in a more diversified direction, as areas under cereals and the low-yielding part of forage grass production will decrease and free up arable land, especially for legumes and oilseeds, grasses used for biogas production, and green manure grasses. As a whole, carbon sequestration in mineral soils is clearly improved. Mineral land will change from the source of greenhouse gas emissions to their sinks in 2035. This will be improved by increasing the cultivation of collection plants and with multi-species grass in both fodder production and trees. Biogas and solar energy will be promoted through new controls and additional subsidies related to the utilization of the energy produced and improved the nutrient cycle in collaboration with various actors. In the WAM1 scenario, greenhouse gas emissions will decrease by 29% from 2018 to 2035 and by 38% by 2050. This means about 6 Mt CO2 eq. emission reductions in 2050. Of this approximately 1.9 Mt CO2eq. is achieved through peatland measures and approximately 2.2 Mt CO2 eq. is achieved through change in land use and targeted carbon sequestration of mineral land. The change in energy use and production in agriculture also results in a small reduction in greenhouse gas emissions (0.2 Mt CO2 eq.), As well as a reduction in the number of cattle, which is at the same level in the WAM scenarios as in the WEM scenario. In the WAM2 scenario, greenhouse gas emissions from agriculture decrease by 42% by 2035 (77% by 2050) from 2018. This would mean approximately 12 Mt CO2 eq. emission reductions in 2050 (6.8 Mt CO2 eq. in 2035). Of this approximately 3.1 Mt CO2 eq. would result from the application of various measures in larger scale on peatlands, in particular the restoration of peatlands, adjustable drainage and the afforestation of thin peatlands. In mineral soils, the target in this scenario is a large carbon sink up to 5 Mt CO2 eq. year 2050 (2 Mt CO2 eq. year 2035). This has been considered a highly targeted and ambitious scenario. At present, the high carbon sequestration target in the WAM2 scenario for mineral lands cannot be calculated using data and methods applied in the official greenhouse gas inventory, used by the Natural Resources Institute Finland (Luke). Assessing the achievement of the goal would require new materials and methods. The goal is challenging. It requires long-term work and improved and new solutions in carbon sequestration, where a special issue is not only to increase the carbon supply to soils, but also the duration of carbon in the soil, which entails great uncertainties, e.g. due to global warming. However, producer organizations have a strong will to achieve this goal. Instead, the WAM1 scenario can already be considered achievable in terms of current knowledge, even realistic, if the challenges associated with incentives and control measures are addressed. In particular, this applies to the improved conditions for a farmer to be fully compensated for the loss of income as a result of the loss of agricultural subsidies on peatlands that have been restored, abandoned or afforested. In addition, peatlands need separate support and incentives to keep the water level high and to verify this. All this requires new resources of 300-500 million euros to be used in Finland for the period 2020-2050. In addition, resources are needed for technical development and application of methods such as precision cultivation, new, more productive and climate-resistant plant varieties, successful carbon sequestration and its verification on mineral soils, and successful restoration in peatlands. The use of these resources would be relatively low in the initial phase but would increase significantly by the 2030s, at the latest. This is because the development of new incentives, controls and their conditions, as well as technology and verification, take time. In addition, additional subsidies and marketing are needed to increase the production of bioenergy and nutrient recycling. A significant part of the additional resources should come from market-based activities. As a whole, agriculture in WAM1-scenario changes in a much more sustainable direction with several different sustainability indicators, so the use of public resources for change is also justified. The design of policy instruments over previous agricultural policy instruments is challenging and may require changes to certain conditions of existing instruments, such as special conditions of agricultural support, in order for the instruments to have the desired effect, for example to abandon low-yielding agriculture to achieve reductions in GHG emissions with low costs. The above-mentioned reductions in greenhouse gas emissions can already be considered quite significant for the WAM1 scenario and already require extensive work at many levels to be achieved. Much also depends on whether progress is made with sustainable intensification in agriculture, which is behind both WAM scenarios. This means above all raising the crop yield levels and making a more accurate use of fertilizers and other inputs. This also means improving the growing condition of the fields, significantly diversifying the crop rotations and thereby improving the conditions for carbon sequestration in mineral land. All this is not easy but it is possible and already now it is the reality on many individual farms. There are many significant uncertainties and unresolved problems regarding both large-scale application of peatland measures, in particular rewetting peatlands (ie the raising of the water surface) and the effective carbon sequestration of minerals. Targeted solutions must be sought both at farm level and in research and development. The measures leading to the development of emissions in the WAM scenarios require an environment in which the farmer benefits financially from the reduction of greenhouse gas emissions and related measures. If such an arrangement is not achieved, but the farmer has income losses, such as negative effects on agricultural production or losses of agricultural subsidies without corresponding benefits or compensation for losses, it will not be possible to achieve the greenhouse gas emission reductions presented in the WAM scenarios. At the same time, effective and well-targeted policy instruments and controls enable the development of sustainable nutrient cycles and further reduced emissions. Biogas production creates solutions to the regional challenges of concentrated livestock production in the use of fertilizer nutrients and to improve the nutrient self-sufficiency in agriculture, i.e. replacement of mineral fertilizers. An integral part of the development to reduce greenhouse gas emissions is the promotion of agricultural energy production and the associated nutrient cycle (nitrogen, phosphorus, potassium). In the WAM1 scenario, biogas production and the associated nutrient cycle would be supported and promoted in many ways. Incentives would lead to a strong development of the market for both transport and industrial biogas and recycled fertilizer products, which would increase the diversion of agricultural materials to biogas production. In that case, more than a third of animal manure would be directed to biogas production. In 2050, the energy content of livestock manure -based biogas would increase to approximately 38% of the total energy potential of livestock manure as biogas. In addition, energy would be obtained in the WAM1 scenario from grasslands, especially in southern Finland with an area of 50,000 ha. A significant part of the animal manure would end up in large biogas plants, larger than farm size, which enables regional redistribution of nutrients. In the WAM2 scenario, incentives and support measures for biogas production and nutrient cycles should be further improved. In that case, the production of biogas from agricultural biomass would increase further, especially the use of biogas in grasslands would clearly increase. The share of transport biogas and industrial biogas in the energy produced would increase significantly. The proportion of plants larger than the agricultural farm size of biogas plants would increase to increase the efficiency and control of transport’s biogas production, especially in the direction of liquefied biogas for heavy transport. The amount of energy produced from biogas in the WAM2 scenario would increase by 2050 to about 48% of the total energy potential for animal manure as biogas. In addition, energy would be obtained in the WAM2 scenario from 150,000 hectares of grassland, most of them in southern Finland. In this case, the proportion of grass for biogas would be higher than manure. By replacing fossil energy, emission reductions will be achieved on farms and in the surrounding areas, although the total impact on greenhouse gas emissions will remain relatively small, less than 0.5 Mt CO2 eq. However, biogas energy produced from agricultural materials remains not only for agriculture, but cooperation between sectors in the production, processing and use of raw materials is essential. In the WAM1 scenario, it is estimated that at least 8 million kg of nitrogen fertilizer will be released from biogas plants to plant production farms. In the WAM2 scenario, it can be estimated that approximately 19 million kg of nitrogen fertilizer from biogas plants will be released to plant production farms. Approximately 150 million kg of inorganically industrially produced nitrogen fertilizer was spent in Finland in 2018. In addition, this figure could be 20% lower, 120 million kg in 2050 through sustainable intensification in the WAM scenarios. Biogas can therefore produce a significant part of the need for nitrogen fertilizer. In addition to climate change, biogas can contribute to other positive environmental consequences, such as air quality (less ammonia) and water status (less nutrient leaching). All this can be achieved through the sustainable utilization of digested residues from biogas plants in efficient nutrient cycles. The large roof area of the agricultural production building and also the available land areas make the farms very suitable for the construction of solar power plants. Production growth is particularly limited by the fact that 90% of production is generated in March-September and that only solar energy produced for own use is eligible for investment support. Extending investment support to power plants and batteries planned for sale, temporary compensation of sales, facilitating the formation of energy communities, realization of virtual batteries and incentive tax treatment of outgoing electricity would accelerate the realization of solar power investments on farms. It would be possible to cover about 8% of the electricity consumption for farms with solar cell oil by 2035 and about 14% by 2050. During the summer months, solar energy in combination with a battery can make individual farms completely self-sufficient. The climate measures and policy instruments to promote them on a large scale also have significant social and cultural consequences. Changes in the operating environment and society’s expectations affect both the competence requirements and the farmers’ professional image, especially in the WAM1 and WAM2 scenarios. In the WAM1 and WAM2 scenarios, food production is increasingly integrated into climate measures. Large farms in grain and animal husbandry have better economic opportunities for the introduction of new technology and production methods required by climate measures. The network-based strategy takes over the sector, which in the WAM2 scenario enables large-scale biogas production that successfully combines decentralized and centralized solutions. Involving small and remote farms in this development based on efficient division of labor and cooperation, as well as technical change, is challenging, but can be solved through networks. If farmers do not know the changing goals or culture of agriculture and consider them as their own, it can lead to ambiguities or conflicts about their own professional image. In the scenarios, measures and development costs are not targeted at all farmers in the same way. Individual farmers are in a different position depending on the characteristics of the farm and the climate measures that have already been taken before. Therefore, when planning climate action, the encounter with different social and cultural effects must also be determined in advance. The development described in the WAM2 scenario can only work if policy guidelines for climate action are implemented in such a way that all farmers consider that they have common goals. The measures to reduce greenhouse gas emissions were considered both to reduce and increase water pollution and biodiversity in the field. The reduction of active agricultural activity and the replacement of traditional field use with new agricultural methods and partly also with land use changes will create more different field environments and provide more space for wild species. The same changes will also reduce nutrient effluent to watercourses in the long term. On the other hand, changing land use may put a significant strain on local waterways in the short term. In addition, the rural landscape will change and the area suitable for fields will decrease. It is not self-evident that society largely understands and appreciates the change in the agricultural landscape and field use that would result from a sharp reduction in greenhouse gas emissions.
Chapter
The causes of global warming have been subject of controversy, especially in the last 50–100 years. There has been a remarkable effort by the international scientific community to reduce the amounts of CO2 emitted into the atmosphere. It is well known that the CO2 capture step accounts for around 60–70% of the whole cost of the carbon capture and storage (CCS) chain. Although some CO2 capture technologies have been proposed, chemical absorption and adsorption are currently the most suitable ones for post-combustion capture in power plants.
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Healthy soils ensure food security through sustainable agricultural production and also support in mitigating the climate change hazardous like global warming and greenhouse gases emission. However, the anthropogenic distresses of global carbon cycle cause serious risks of global warming due to the rise in the atmospheric concentration of carbon dioxide and other greenhouse gases. Alkaline soils occupy around one-third of the land but contain only a small quantity of soil organic carbon which is crucial in sustaining soil health and productivity. The mismanagement and misuse of alkaline soils result in soil erosion, poor soil productivity, lower water retention, weak soil biodiversity, and desertification which ultimately cause a substantial loss of soil organic carbon. These soils have pronounced capacity of carbon sequestration which requires proper management and land use practices. The adoption of conservation tillage, crop rotation, cover crops, and organic amendments can minimize soil erosion and enhance soil quality. Additionally, these practices compared with conventional operations can enhance soil quality and water retention and reduce the emission of greenhouse gases. The fallowing of lands must be discouraged because appropriate vegetative cover promotes carbon storage in alkaline soils.
Article
Changes in soil organic carbon (SOC) content depending on different factors are extensively investigated when the soil is in steady-state equilibrium between formation and decomposition of soil organic matter. However, studies of SOC formation and dynamics in initally organic matter free soil are rare. Evolution of soil organic carbon was studied in a field experiment established in 1964 on a carbonaceous glacial till soil with very low initial SOC content (1.28 g kg⁻¹). The effects on SOC content changes of bare fallow, barley and different perennial fodder crops such as grasses, clover-grass mixture, galega, hybrid lucerne and a turfgrass mixture, with or without mineral N and PK fertilisation and manure, were studied. There were 19 treatments in total and most had unchanged plant cover composition throughout the experiment. During 1964–2014, SOC stock increased in all treatments, by 0.11 Mg ha⁻¹ y⁻¹ in bare fallow and by at most 0.50 Mg ha⁻¹ y⁻¹ in the treatment with hybrid lucerne and manure. Average SOC sequestration rate was 0.35 ± 0.11 Mg ha⁻¹ y⁻¹. SOC changes were highly correlated with estimated C inputs and were therefore higher in treatments with perennials than with an annual barley crop. C retention efficiency for total crop-derived C inputs and for organic amendments was 6.1% and 22%, respectively. Water-soluble C measured in 2014 increased linearly with SOC, indicating that the quality of recently formed SOC was not strongly affected by the treatments. However, water-soluble C as a fraction of SOC was significantly lower in treatments with legumes than in treatments with bare fallow or a barley or grass crop. These results demonstrate that the quantity and quality of C inputs were both main drivers for observed changes in SOC. However, C retention efficiency of C inputs was relatively low. This may be related to soil texture with high sand proportion, suggesting that SOC sequestration rates in light-textured soils may be lower than expected even in case of low initial SOC content.
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RothC is an established model for predicting soil organic carbon (SOC) changes in response to environmental conditions and management. The model lacks algorithms for carbon input estimation and a differentiated consideration of carbon input sequestration from organic amendments commonly used in agriculture. Moreover, it does not consider the higher stability of below-ground crop residues in relation to above-ground crop residues. RothC was combined with two empirical approaches for quantifying carbon inputs from above- and below-ground crop residues and tested on 439 SOC data series from 36 arable long-term field experiments in Central and Northern Europe. Effects of carbon input quality on model fit were quantified with linear mixed models based on the analytical solution of RothC. Model parameters that describe the stability of incoming carbon were calibrated using a multi-site approach and Bayesian calibration. A second calibration study combined the determination of partitioning of incoming carbon into pools with different turnover rates and model responses to temperature and soil water content. With this calibration we showed that the contribution of above-ground residues to SOC is lower than when estimated with default RothC paramerization. We also show that the relative contribution from roots to SOC is higher than that from above-ground residues. Moreover, the degradability of organic amendments was highly variable between amendment categories and increased for all model configurations in the following order: farmyard manure < farmyard compost < sawdust < sewage sludge < peat. The proposed RothC partition coefficients for above-ground residues, roots and several commonly used organic amendments as estimated for this large data set should be useful for other studies in temperate climates. We also show that the analytical solution of RothC is closely related to the much simpler empirical humus balancing approaches used by farm advisory services. This provides opportunities to build bridges between the more process-oriented SOC models used in research and the well established instruments used by the farming community to assess the effects of agricultural management practices on SOC changes.
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Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.
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A simple model to predict soil water components and the CO2 release for peat soils is presented. It can be used to determine plant water uptake and the CO2 release as a result of peat mineralization for different types of peat soils, various climate conditions, and groundwater levels. The model considers the thickness of the root zone, its hydraulic characteristics (pF, Ku), the groundwater depth and a soil-specific function to predict the CO2 release as a result of peat mineralization. The latter is a mathematical function considering soil temperature and soil matric potential. It is based on measurements from soil cores at varying temperatures and soil water contents using a respiricond equipment. Data was analyzed using nonlinear multiple regression analysis. As a result, CO2 release equations were gained and incorporated into a soil water simulation model. Groundwater lysimeter measurements were used for model calibration of soil water components, CO2 release was adapted according long-term lysimeter data of Mundel (1976). Peat soils have a negative water balance for groundwater depth conditions up to 80—100 cm below surface. Results demonstrate the necessity of a high soil water content i.e. shallow groundwater to avoid peat mineralization and soil degradation. CO2 losses increase with the thickness of the rooted soil zone and decreases with the degree of soil degradation. Especially the combination of deep groundwater level and high water balance deficits during the vegetation period leads to tremendous CO2 losses.
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An extended water regime model was used for calculating the evapotranspiration, groundwater recharge, and peat mineralization (CO2 and N release) for various fen locations with grassland utilization in dependence on the groundwater level. The results show that an increasing groundwater level leads to a strong decline of the actual evapotranspiration Et. For example, increasing the groundwater level from 30 to 120 cm diminishes the Et by up to 230 mm a—1. A positive groundwater recharge only takes place at groundwater levels of 90 cm and more. At smaller distances the capillary rise into the rooting zone during the summer months is greater than the water seepage during the winter months, so that a negative groundwater recharge-balance is reached in the course of a year. The CO2- and the N-release, as well as the annual decline in peat thickness, increase significantly with rising groundwater levels. The results show, that varying the groundwater level can influence the water regime and the peat mineralization significantly. The lower the groundwater level the less is the peat decomposition. The demand for a groundwater level as small as possible is, however, limited by an agricultural utilization of the fens. Choosing the optimum groundwater level should consider the aims (1) peat mineralization, (2) gas emission (CO2, CH4, N2O), and (3) crop production. If a grassland utilization is supposed to be made possible and all three aims above are given equal importance, the groundwater level should be maintained at 30 cm. At this distance, about 90 % of the optimum plant output can be reached. The peat mineralization can be reduced to 30 to 40 % of the maximum peat mineralization. The gas emission amounts to 50—60 % of the maximum value.
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Current interest in carbon (C) exchange processes between terrestrial ecosystems and the atmosphere have identified a need to assess soil C stocks or inventories for specific soil types and climates. In this study, the mean store of C and nitrogen (N) was determined in the soil profile of several Gleysolic, Podzolic, Luvisolic, and Brunisolic soils under different agricultural management systems, in the cool, humid region of eastern Canada. Based on a total of 69 management treatments from 16 agroecosystem sites, mean soil C and N densities (to a soil depth of 60 cm) ranged from 3.1 to 13.1 kg C m ⁻² and from 0.36 to 1.05 kg N m ⁻² The C:N ratio ranged from 8.3 to 17.1. Distribution of C and N down the soil profile showed a relatively regular pattern of C and N decrease with depth. Estimated C stocks or storage for the 1-m soil depth ranged from 8.3 to 13.3 kg C m ⁻² for the Gleysolic soils, and 5.4 to 10.5 kg C m ⁻² for the Podzolic soils, with an overall range and mean for all soils of 3 to 16 kg C m ⁻² and 9.8 kg C m ⁻² ± 2.8 This indicates that some agricultural soils in eastern Canada possess a relatively high potential for organic matter storage. Key words: Organic carbon and nitrogen storage, agroecosystem, Gleysol, Podzol, Luvisol, Brunisol, cool-humid climate
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Legume-based cropping systems could help to increase crop productivity and soil organic matter levels, thereby enhancing soil quality, as well as having the additional benefit of sequestering atmospheric C. To evaluate the effects of 35 yr of maize monoculture and legume-based cropping on soil C levels and residue retention, we measured organic C and 13C natural abundance in soils under: fertilized and unfertilized maize (Zea mays L.), both in monoculture and legume-based [maize-oat (Avena sativa L.)-alfalfa (Medicago sativa L.)-alfalfa] rotations; fertilized and unfertilized systems of continuous grass (Poa pratensis L.); and under forest. Solid state 13C nuclear magnetic resonance (NMR) was used to chemically characterize the organic matter in plant residues and soils. Soils (70-cm depth) under maize cropping had about 30-40% less C, and those under continuous grass had about 16% less C, than those under adjacent forest. Qualitative differences in crop residues were important in these systems, because quantitative differences in net primary productivity and C inputs in the different agroecosystems did not account for observed differences in total soil C. Cropping sequence (i.e., rotation or monoculture) had a greater effect on soil C levels than application of fertilizer. The difference in soil C levels between rotation and monoculture maize systems was about 20 Mg C ha-1. The effects of fertilization on soil C were small (∼6 Mg C ha-1), and differences were observed only in the monoculture system. The NMR results suggest that the chemical composition of organic matter was little affected by the nature of crop residues returned to the soil. The total quantity of maize-derived soil C was different in each system, because the quantity of maize residue returned to the soil was different; hence the maize-derived soil C ranged from 23 Mg ha-1 in the fertilized and 14 Mg ha-1 in the unfertilized monoculture soils (i.e., after 35 maize crops) to 6-7 Mg ha-1 in both the fertilized and unfertilized legume-based rotation soils (i.e., after eight maize crops). The proportion of maize residue C returned to the soil and retained as soil organic C (i.e., Mg maize-derived soil C/Mg maize residue) was about 14% for all maize cropping systems. The quantity of C3-C below the plow layer in legume-based rotation was 40% greater than that in monoculture and about the same as that under either continuous grass or forest. The soil organic matter below the plow layer in soil under the legume-based rotation appeared to be in a more biologically resistant form (i.e., higher aromatic C content) compared with that under monoculture. The retention of maize residue C as soil organic matter was four to five times greater below the plow layer than that within the plow layer. We conclude that residue quality plays a key role in increasing the retention of soil C in agroecosystems and that soils under legume-based rotation tend to be more "preservative" of residue C inputs, particularly from root inputs, than soils under monoculture.
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Soil C sequestration research has historically focused on the top 0 to 30 cm of the soil profile, ignoring deeper portions that might also respond to management. In this study we sampled soils along a 10-treatment management intensity gradient to a 1-m depth to test the hypothesis that C gains in surface soils are off set by losses lower in the profile. Treatments included four annual cropping systems in a corn (Zea mays)-soybean (Glycine max)-wheat (Triticum aestivum) rotation, perennial alfalfa (Medicago sativa) and poplar (Populus x euramericana), and four unmanaged successional systems. The annual grain systems included conventionally tilled, no-tillage, reduced-input, and organic systems. Unmanaged treatments included a 12-yr-old early successional community, two 50-yr-old mid-successional communities, and a mature forest never cleared for agriculture. All treatments were replicated three to six times and all cropping systems were 12 yr post-establishment when sampled. Surface soil C concentrations and total C pools were significantly greater under no-till, organic, early successional, never-tilled mid-successional, and deciduous forest systems than in the conventionally managed cropping system (p <= 0.05, n = 3-6 replicate sites). We found no consistent differences in soil C at depth, despite intensive sampling (30-60 deep soil cores per treatment). Carbon concentrations in the B/Bt and Bt2/C horizons were lower and two and three times more variable, respectively, than in surface soils. We found no evidence for C gains in the surface soils of no-till and other treatments to be either off set or magnified by carbon change at depth.
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The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases. A discrepancy of approximately 350 × 1015 g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo-referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a 1/2° latitude by 1/2° longitude version of the corrected and digitized 1:5 M FAO–UNESCO Soil Map of the World. Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100 cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30 cm, 1462–1548 Pg of C in the upper 100 cm, and 2376–2456 Pg of C in the upper 200 cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate-C is held in the upper 100 cm of the world's soils. Mean C: N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100 cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO2 and the predicted associated rise in temperature are discussed.
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Long-term effects of fertilization, crop rotation and weather factors [temperature, precipitation, net radiation, maximum (potential) evapotranspiration (ET) and corn heat units (CHU)] on the sustainability of corn grain yields were investigated over 35 yr. Treatments included fertilized and unfertilized continuous com and rotation corn-oats-alfalfa-alfalfa. The fertilized rotation corn treatment produced the greatest corn grain yields (15% moisture content) with an average of 7.75 t ha⁻¹ followed by the fertilized continuous corn treatment with 6.02 t ha⁻¹. Fertilization increased grain yield for continuous corn treatments by 279% and increased grain yields in the rotational corn treatments by 70%. Corn grain yields increased with time with the fertilized rotation treatment, remained relatively constant with the fertilized continuous corn and decreased with the unfertilized treatments. Growing season precipitation was the only weather variable tested which was significantly related to corn grain yield. Precipitation in July was proportional to corn grain yield for all fertilized treatments. Weather variation played little role for unfertilized corn. Continuous corn production was sustained (yields did not decrease with time) when fertilizer was added. There was a considerable yield advantage with fertilized corn when grown in a rotation compared with fertilized continuous corn. Fertilization and crop rotation practices increased and buffered corn yields. Key words: Long-term, corn, yield, fertilization, rotation, weather
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Background and aims In agroecosystems, carbon (C) inputs come from plant roots, retained shoot residues and in some cases from applied manures. Manure and shoot derived C inputs are relatively easy to determine. Conversely, high costs associated with root measurements have caused knowledge on root C input to remain scant. This study aimed at determining macro-root C input and topsoil root related respiration in response to nutrient management and soil fertility building measures. Methods We sampled roots and shoots of cereals and catch crops in inorganic and organic fertilizer-based arable cropping systems in a long-term experiment in 2 years, 2008 and 2010. Sampled shoots and macro-roots of catch crop mixtures and cereals were characterized for dry matter (DM) biomass (C was estimated as 45 % of DM biomass). We also measured topsoil root-related soil respiration throughout the growing season of winter wheat by subtracting soil respiration from soil with and without exclusion of roots. Results Catch crop roots accounted for more than 40 % of total plant C. For spring barley in 2008 and spring wheat in 2010, root C was higher in the organic than in the inorganic fertilizer-based systems. However, for winter wheat in 2008 and spring barley in 2010, there were similar amounts of root C across systems. The measurements of topsoil root-derived respiration also showed no difference across systems, despite large differences in harvested cereal yields. Cereal biomass shoot-to-root (S/R) ratio was higher (31–131 %) in inorganic than in organic fertilizer-based systems. Conclusions Our findings show that macro-roots of both cereal crops and catch crops play a relatively larger role in organically managed systems than in mineral fertilizer based systems; and that the use of fixed biomass S/R ratios to estimate root biomass leads to erroneous estimates of root C input.
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Climate records of air temperature (AT) and total precipitation (TP) are standard inputs for soil carbon dynamic models, i.e., for calculating temperature and moisture effects on soil biological activity. In this study our objective was to determine both spatial and temporal differences in soil biological activity in the Province of Québec, Canada. Soil biological activity was here calculated on a daily basis with the ICBM re_clim parameter using data from weather stations. When keeping soil and crop properties constant, re_clim (unitless) allows us to assess relative differences in soil biological activity. The magnitude of the temporal changes in re_clim, AT and TP were analyzed using Sen’s slope, which is a nonparametric method used to determine the presence of a trend component. The re_clim varied across Québec from 0.50 (58 °N) to a high of 1.66 (45 °N). Considering only the area with significant agricultural production, re_clim varied from 0.99 at Gaspé (48 °N) to 1.66 at Philipsburg (45 °N), i.e., soil organic carbon (SOC) decomposition rate is 68 % higher at the latter site (1.66/0.99) and correspondingly more C input is needed to maintain SOC. Soil biological activity increased from 1960 to 2009, with a mean slope variation in re_clim of about +10 %. The temporal variation in AT had more influence than that of TP. For 1980–2009 the mean annual slope of re_clim was significantly different from zero for 29 out of 49 climate records (mean = +14 %; N = 29). We also emphasize that analysis of seasonal changes in AT is an issue that needs further attention, as well as modeling climate-induced changes in SOC dynamics based on future climate scenarios.
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Bolinder, M. A., Katerer, T., Andren, O. and Parent, L. E. 2012. Estimating carbon inputs to soil in forage-based crop rotations and modeling the effects on soil carbon dynamics in a Swedish long-term field experiment. Can. J. Soil Sci. 92: 821-833. There is a need to improve the understanding of soil organic C (SOC) dynamics for forage-based rotations. A key requisite is accurate estimates of the below-ground (BG) C inputs to soil. We used the Introductory Carbon Balance Model (ICBM) to investigate the effects of C input assumptions on C balances with data from a 52-yr field experiment in northern Sweden. The main objective was to validate an approach for estimating annual crop residue C inputs to soil using the data from a continuous forage-based rotation (A). A rotation with only annual crops and more frequent tillage events (D) was used to obtain a rough estimate of the effect of tillage on SOC dynamics. The methodology used to estimate annual crop residue C inputs to soil gave a good fit to data from four out of the six large plots for rotation A. The approximate effects of more frequent tillage in rotation D increased SOC decomposition rate by about 20%. These results allow us to have more confidence in predicting SOC balances for forage-based crop rotations. Root biomass measurements used for calculating BG C inputs were also reviewed, and we show that they have not changed significantly during the past 150 yr.
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Soil organic matter is important in relation to soil fertility, sustainable agricultural systems, and crop productivity, and there is concern about the level of organic matter in many soils, particularly with respect to global warming. Long-term experiments since 1843 at Rothamsted provide the longest data sets on the effect of soil, crop, manuring, and management on changes in soil organic matter under temperate climatic conditions. The amount of organic matter in soil depends on the input of organic material, its rate of decomposition, the rate at which existing soil organic matter is mineralized, soil texture, and climate. All four factors interact so that the amount of soil organic matter changes, often slowly, toward an equilibrium value specific to the soil type and farming system. For any one cropping system, the equilibrium level of soil organic matter in a clay soil will be larger than that in a sandy soil, and for any one soil type the value will be larger with permanent grass than with continuous arable cropping. Trends in long-term crop yields show that as yield potential has increased, yields are often larger on soils with more organic matter compared to those on soils with less. The effects of nitrogen, improvements in soil phosphorus availability, and other factors are discussed. Benefits from building up soil organic matter are bought at a cost with large losses of both carbon and nitrogen from added organic material. Models for the buildup and decline of soil organic matter, the source and sink of carbon dioxide in soil, are presented.
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While the adoption of no-till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number Of Studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full-inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under,NT than FIT in the surface soil layers. At the 21- to 25-cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26-35 cm). On average, there was 4.9 Mg ha(-1) more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R(2) = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT Could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
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Abstract The present study quantifies changes in soil organic carbon (SOC) stocks in Belgium between 1960, 1990 and 2000 for 289 spatially explicit land units with unique soil association and land-use type, termed landscape units (LSU). The SOC stocks are derived from multiple nonstandardized sets of field measurements up to a depth of 30 cm.Approximately half of the LSU show an increase in SOC between 1960 and 2000. The significant increases occur mainly in soils of grassland LSU in northern Belgium. Significant decreases are observed on loamy cropland soils. Although the largest SOC gains are observed for LSU under forest (22 t C ha−1 for coniferous and 29 t C ha−1 for broadleaf and mixed forest in the upper 30 cm of soil), significant changes are rare because of large variability. Because the number of available measurements is very high for agricultural land, most significant changes occur under cropland and grassland, but the corresponding average SOC change is smaller than for forests (9 t C ha−1 increase for grassland and 1 t C ha−1 decrease for cropland). The 1990 data for agricultural LSU show that the SOC changes between 1960 and 2000 are not linear. Most agricultural LSU show a higher SOC stock in 1990 than in 2000, especially in northern Belgium. The observed temporal and spatial patterns can be explained by a change in manure application intensity.SOC stock changes caused by land-use change are estimated. The SOC change over time is derived from observed differences between SOC stocks in space. Because SOC stocks are continuously influenced by a number of external factors, mainly land-use history and current land management and climate, this approach gives only an approximate estimate whose validity is limited to these conditions.
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The effects of long-term fertilizer use on soil pH and accumulation of soil organic matter are assessed under permanent grassland. Ammonium nitrate, 75 and 120 kg N ha−1, and 120 kg N ha−1 each of ammonium sulphate and calcium nitrate were applied annually for 43 years in an experiment on permanent grassland established on a drained andic gleysol. Ammonium nitrate had little effect on soil pH, whereas ammonium sulphate decreased the pH from about 6.4 to 3.8 in the top 5 cm of the soil, and the pH to 60 cm depth was less than in other plots. Calcium nitrate caused a slight increase in pH to 6.9 in the top 5 cm and to >7 at greater depths. The fertilizers increased organic matter in the top 5 cm of the soil from 6.9–8.8% C in 1973 to 12–21% C in 1996. The accumulation is confined mainly to the top 10 cm, and in this layer, the annual increase in organic C is 0.6–1.0 t ha−1. With a C/N ratio of 12–15, this means a yearly increase in N of 45–65 kg ha−1. Organic C increased in the order ammonium nitrate>calcium nitrate>ammonium sulphate, whereas the increase in N followed the order ammonium nitrate>ammonium sulphate>calcium nitrate. The difference in accumulation of C and N leads to diverging C/N ratios, suggesting that the most favourable humus with a narrow C/N ratio occurs where calcium nitrate is used, and the most unfavourable humus occurs where ammonium sulphate is applied over a prolonged period.
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Cultivation of C 3 plants after turning under a native prairie of grasses possessing C 4 metabolism allows partitioning of soil organic matter as to origin. Contrasting natural 13C abundance for the two different contributing kinds of plant residues provides an in situ labeling of the soil organic matter. -from Authors
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Management regimes of varying types and intensities can have profound impacts on grassland soil quality. Plus, there has recently been increased interest in finding soil quality indicators that are reflective of historical and current land management. We surveyed soil quality of privately owned grasslands in northeastern Kansas differing in their cultivation histories and current land-use (cool-season hay and grazed, warm-season native hay and grazed, and Conservation Reserve Program). We found significant differences in individual soil characteristics among management regimes when using both chemical and physical soil quality indicators. Principal components analysis showed that cultivation history and current land-use of these fields could be reflected by overall soil quality. Also, within cultivated fields, overall soil quality significantly increased with time since last cultivation. Our results suggest that using soil quality indicators such as nitrogen, carbon and organic matter are reflective of historical land use, but are not as useful when trying to determine current land use.
Article
The overall objective of this study was to discover the most limiting soil properties for crop production at two fertility sites. The Vreta Kloster soil, classified as a very fine, mixed, semiactive Oxyaquic Haplocryoll, according to the Soil Taxonomy and as a Haplic Phaeozem according to the World Reference Base for Soil Resources (WRB), consisted of very dark greyish brown silty clay overlying a subsoil of heavy clay (70-80%). Porosity increased with depth due to a greater micro- but not macro-pore volume. Stocks of C and N amounted to 76.4 t C ha(-1) and 8.7 t N ha(-1) in the Ap-horizon and 24.8 t C ha(-1) and 3.25 t N ha(-1) in the subsoil to 1 m depth. Soil pH increased with depth, 6.6 to 7.4, and CEC values ranged 25 to 31 cmol(c) kg(-1) soil. The main clay minerals were illite/mica (45%) followed by vermiculite (9-20%). Chlorite and kaolinite amounted to 2% throughout the profile. In dry years, crop production at the Vreta Kloster site was greatly reduced, which can be attributed to the absence of macro-pores and high portion of micro- pores and in the subsoil reducing the amount of water available to crops. The Hogasa profile, classified as a sandy mixed Humic Dystrocryept according to the Soil Taxonomy and as Arenic Umbrisol according WRB, consisted of loamy very fine and fine sand. Soil pH and bulk density increased with depth from 5.7 to 6.5 and 1.3 to 1.6 kg dm(-3), respectively. Carbon and N stocks amounted to 72.3 t C ha(-1) and 5.9 t N ha(-1) in the Ap- horizon and were low in the subsoil, 13.5 t C ha(-1) and 1.1 t N ha(-1). Clay mineralogy was dominated by illite/mica (26-50%) with vermiculite being formed in the Ap-horizon. Chlorite amounted to 3-6% and kaolinite to 2-3% in the profile. Crop yields were less affected by rainfall conditions and leys were more productive at Hogasa than Vreta Kloster. A high mechanical resistance reducing root penetration of the subsoil and a low nutrient content limited crop production at Hogasa.
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Sensitive methods are essential to resolve small changes in soil C storage, such as those attained in sequestration projects, against much larger quantities of C already present. To measure temporal changes in C storage we proposed a high-resolution method based on collecting volumetric soil cores from a microsite (4 by 7 m), marking core locations to intersperse multiple cores collected initially and in a subsequent sampling year, rigorous analytical quality control, and calculating soil C pool sizes with proper corrections for unequal soil masses. To evaluate the method, we measured the recovery of 3.64 Mg C ha-1 added as coal dust to microsites. We calculated C stored in successive soil layers of both fixed volume and equivalent mass. We inferred coal C recovery from spatial comparisons between coalamended and unamended plots, and from temporal comparisons between soil samples collected before and after coal addition. The comparisons among C storage showed effective recovery of added coal C, but only for paired temporal differences based on calculations of organic C storage in an equivalent soil mass. With spatial comparisons, coal C became undetectable when soil thickness exceeded 35 cm. With temporal comparisons, coal C recovery ranged from 91 to 106%, provided differences were calculated for successively thicker layers of equivalent soil mass. In contrast, recovery was only 64 to 82% when temporal differences were calculated for layers of fixed soil volume. The method is useful to quantify small temporal changes in soil organic C storage within microsites, and possibly over more extensive areas with sufficient samples to characterize spatial variability.
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Disturbance of carbon storage in organic soil-wetlands of the temperate zone has been analysed for the last 200 yr and considered in relation to other sources of atmospheric CO2 from the biopsphere. Storage before recent disturbance is estimated at 57-83 Mt C yr-1, >9M of this in boreal peatlands. The total storage rate, lower than previous estimates, reflects accumulation rates of carbon of only 0.20 t ha-1 yr-1 and less in the boreal zone where 90% of temperate organic soils are found. Widespread drainage of organic soil-wetlands for agriculture has significantly altered the carbon balance. A computer model was used to track the consequent changes in the carbon balance of nine wetland regions. Drainage reduced or eliminated net carbon sinks, converting some wetlands into net carbon sources. Different regions thus can function as smaller carbon sinks, or as sources, depending on the extent of drainage. In either case a shift in carbon balance can be quantified. Regional differences are noted. The aggregate shift in the carbon balance of temperate zone wetlands, when added to a far smaller shift from tropical wetlands, equalled 150-185 Mt of carbon in 1980 and 5711-6480 Mt since 1795. Despite occupying an area equivalent to only 2% of the world's tropical forest, the wetlands have experienced an annual shift in carbon balance 15-18% as great.-from Authors