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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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... Within the European Union (EU) alone, SOC sequestration potential is estimated to be between 9 (Frank et al., 2015) and 58 million ton CO 2 per year (Lugato et al., 2014). However, SOC sequestration rate is highly dependent on, for example, soil properties, climate, farming system and current soil C content (Bolinder et al., 2020;Kätterer et al., 2012). This makes it difficult to predict the soil C effect of various cropping systems. ...
... Another reason for SOC depletion in all rotations in the present study might be the initial SOC content in the soil (Kätterer et al., 2012). We do not have information about former land use, but it is plausible that the current management scheme includes e.g. ...
... Our results also indicated lower SOC depletion in High N compared with the Low N regime. This is in line with Kätterer et al. (2012), who concluded that there is a positive correlation between SOC storage and mineral N applied under Swedish conditions, due to increased biomass production at higher N application rates, which in turn increases the supply of organic matter to the soil. Moreover, Kirkby et al. (2014) showed that adequate availability of soil N is essential for the formation of stable soil organic matter. ...
Article
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Modern agriculture's dependence on the intensive use of inputs, such as chemical fertiliser and pesticides, leads to high environmental impacts and, possibly, vulnerability in food security, since most of these inputs are imported from other countries. This calls for more sustainable and resilient agricultural practices. Diversification of crop rotations, e.g. by including perennial leys, enhances provision of ecosystem services, leading to healthier crops and increased yields. Perennial crops also increase soil organic carbon (SOC) stocks, which is interesting from a global warming mitigation perspective. In addition, legume-rich leys can utilise atmospheric nitrogen (N) through symbiotic association with N 2-fixing bacteria. However, few studies have evaluated the effects of short-term perennial leys in rotation on cropping system performance over long periods and under different conditions. In this study, we used data from three sites in a long-term experiment in Sweden (initiated in the 1960 s), in combination with Life Cycle Assessment methodology, to assess the environmental and yield effect of including ley in crop rotations. Two N fertiliser regimes (High, Low) in combination with three six-year crop rotations, consisting of either i) two-year mixed grass-legume ley, ii) two-year pure grass ley or iii) annual crops without ley, were compared. Environmental impacts (climate impact, energy resource depletion, eutrophication potential) of the different combinations were quantified per kg harvested crop (expressed in cereal units, CU) and per hectare. The lowest environmental impact, at all sites, was found for the crop rotation with two-year mixed ley under the Low N regime. On average, this combination resulted in 329 g lower GHG emissions per kg CU than the crop rotation without ley and Low N, primarily due to lower input of chemical N fertiliser, which reduced the impact from fertiliser production and soil N 2 O emissions. Comparison of mean SOC change over the study period revealed reduced SOC stocks for all rotations and all sites, especially in the rotation without ley. Therefore, including short-term perennial leys, especially leys containing legume species, in crop rotations can be a useful tool in meeting policy targets on reducing the environmental impacts of agriculture, and in reducing the dependence on purchased agricultural commodities. However, despite the potential benefits of rotational leys, the market demand for the produced ley biomass may be insufficient. Hence, incentives to increase demand are necessary to promote large-scale adoption, for example, for use in bioenergy production and feed.
... where carbon inputs are equal to carbon outputs, an increase in carbon inputs will result in an increased soil carbon stock and soil carbon sequestration. The carbon stock will continue to increase until the soil reaches a new dynamic equilibrium, which can take a long time (Smith, 2008), especially in the cold climate in Sweden (Kätterer et al., 2012). The carbon stock level at which the soil reaches the new equilibrium depends on spatially differentiated properties such as soil characteristics, climate, type of crop and management. ...
... The carbon stock level at which the soil reaches the new equilibrium depends on spatially differentiated properties such as soil characteristics, climate, type of crop and management. This means that soil carbon sequestration will always have a finite climate mitigation capacity (Smith, 2014), and that the effect will vary both between different locations and between different points in time for a particular mitigating scheme (Kätterer et al., 2012). Furthermore, soil carbon sequestration is a reversible process, which means that sequestered carbon can be re-emitted to the atmosphere at any time, for example if the continuity in land management is broken. ...
... Moreover, Swedish national inventories of agricultural mineral soils have shown that carbon stocks have increased over the past three decades, which has been attributed to an increased area of grass cultivation to support an increasing Swedish horse population (Poeplau et al., 2015a). Other strategies to increase soil carbon involve recycling of organic material, use of cover crops and nitrogen fertilisation (Kätterer et al., 2012). ...
Thesis
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One strategy to limit global warming is to phase out fossil products and replace them with bio-based alternatives. This is often referred to as transitioning from a fossil economy to a bioeconomy. In this transition, it is important to know the environmental impact of bio-based products, since it can be greater than that of the fossil products they replace. Life Cycle Assessment (LCA) is a suitable methodology for studying the impact of bio-based products, since it encompasses the whole life cycle of the product. However, LCA rarely considers spatial and temporal variations in impacts. It also rarely includes soil processes such as soil carbon balance and only roughly estimates nitrous oxide (N2O) emissions from soil. In this thesis, LCA was combined with the agro-ecosystem model DNDC to include these soil processes and their variations over time and space. The combined method was used to assess climate impact and eutrophication in grass production at five sites in central and southern Sweden and the climate impact and energy balance in grass-based biogas production in Uppsala municipality, Sweden. Analysis of grass cultivation with two fertilisation rates (140 and 200 kg N ha-1) at different Swedish sites revealed that the higher rate gave a lower climate impact per Mg harvested biomass, but that site properties were more important than fertilisation intensity in determining the climate impact. Analysis of grass for biogas production, which was assumed to be cultivated on fallow land, was conducted for more than 1000 regional sites with different properties in Uppsala municipality and the whole life cycle was included (cradle to grave). The results showed large variations in impact between different sites, depending on weather conditions, soil properties, transport distances etc. The greenhouse gas fluxes from grass cultivation with the greatest climate impact were soil N2O emissions and emissions from fertiliser manufacture, which contributed to global warming, and changes in soil carbon balance, which generally had a climate mitigating effect. Overall, grass cultivation increased soil carbon stocks, but this effect was highly site- and time-dependent. The grass-based biogas production system reduced the climate impact significantly compared with the reference fallow-diesel-mineral fertiliser system. The method developed in this thesis, where LCA was combined with agro-ecosystem modelling, could be used to assess the environmental impact of agricultural systems in other regions. The results could then also be used to assist policymakers in optimising agricultural land use planning for food, feed and fuel production.
... In order to build up soil organic carbon (SOC) stocks in agricultural soils or maintain them with a changing climate, increased organic carbon (OC) inputs are needed (Riggers et al. 2021). Various management strategies for SOC sequestration have been identified, such as minimising bare fallow periods, adjusting nitrogen (N) fertilisation, increasing the recycling of organic material, and non-harvesting of crop residues (Kätterer et al. 2012;Paustian et al. 2016). However, aboveground biomass is used in many ways, such as for food and fodder, but also as a renewable source of energy or fibre. ...
... Therefore, optimised genotype selection can increase root biomass C inputs to the soil by selecting genotypes that grow more root biomass. The C bound in this additional root biomass can in turn contribute to potentially increasing SOC stocks (Kätterer et al. 2012). Breeding efforts in recent decades have resulted in increasing yields (Fischer and Edmeades 2010) by focusing on the water and nutrient uptake of the root system, but not on the size of the root system (van Noordwijk and de Willigen 1987; Kell 2011; Lynch and Wojciechowski 2015). ...
Article
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Background and aims Soil carbon sequestration can play an important role in mitigating climate change. Higher organic C inputs to agricultural soils are needed in order to increase soil organic carbon (SOC) stocks. Genotype selection and breeding towards increased root biomass may enhance root C inputs to the soil and could therefore be a promising, easy-to-implement management option for potentially increasing C sequestration. However, an increase in root C inputs may compromise yield, which is not desirable in terms of food security. Methods Data from 13 global studies with field experiments were compiled in order to estimate the potential of optimised genotype selection for enhancing root biomass without compromising the yield of winter wheat, spring wheat, silage maize, winter rapeseed and sunflower. A lack of data on the effect of variety on rhizodeposition was identified which thus had to be excluded. Results Systematic genotype selection increased mean yields by 52% and mean root biomass by 22% across all crops and sites. A median root C increase of 6.7% for spring wheat, 6.8% for winter rapeseed, 12.2% for silage maize, 21.6% for winter wheat and 26.4% for sunflower would be possible without a yield reduction. Conclusion Overall, this review demonstrates that optimised genotype selection can be a win-win option for increasing root biomass C input to soil while maintaining or even enhancing yield.
... 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]. ...
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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.
... Soil disturbance generally reduces soil health and in organic soils it can accelerate the ongoing aerobic degradation of the organic matter (Gesch et al. 2007;Elder and Lal 2008). Solutions known to reduce the loss of organic matter include water table management, reducing tillage, amendments that inhibit microbial activity and the application of organic mulches (Morris et al. 2004;Gesch et al. 2007, Wright andSnyder 2009;Kätterer et al. 2012). However, if tillage results in very dry conditions that are unfavourable for microbial decomposition it can actually reduce carbon loss (see Kätterer et al. 2012). ...
... Solutions known to reduce the loss of organic matter include water table management, reducing tillage, amendments that inhibit microbial activity and the application of organic mulches (Morris et al. 2004;Gesch et al. 2007, Wright andSnyder 2009;Kätterer et al. 2012). However, if tillage results in very dry conditions that are unfavourable for microbial decomposition it can actually reduce carbon loss (see Kätterer et al. 2012). As cultivation did not significantly reduce the viable seedbank after three years, it should be used with parsimony to maintain soil health. ...
Article
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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.
... 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.
... It serves as an essential ecological index for evaluating plant health and its effects on crop yield and production (Agathokleous et al., 2019;Osaki et al., 1996). Understanding R:S and root mass allocation is vital for insights into carbon allocation and storage in ecosystems (Bolinder et al., 1997;Mokany et al., 2006), agricultural soils (Heinemann et al., 2023), soil carbon sequestration (Heinemann et al., 2023;Kätterer et al., 2012), crop production (Bolinder et al., 2007;Huck et al., 1986) and nutrient uptake (Bacher et al., 2022;Lynch et al., 2012). The R:S ratio fluctuates throughout the growing season (Bolinder et al., 2002(Bolinder et al., , 2007Lynch et al., 2012) and is influenced by environmental factors (water, nutrients, CO 2 ), agricultural indicate that more field experiments are needed to fully understand the impact of tillage methods on R:S across genotypes, environments and managements. ...
Article
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Conventional tillage (CT) is a widely used agricultural practice aimed at loosening soil to enhance water infiltration and root growth. However, it can lead to environmental issues such as increased soil erosion and loss of nutrients and carbon. To address these challenges, non-conventional tillage systems like no-tillage and minimum tillage (collectively referred to as NT) have gained popularity in recent decades. This review examines the effects of CT and NT on the root: shoot ratio (R:S) based on 28 studies covering common crops across various climates and managements. Most studies were primarily on maize, wheat, rapeseed and barley. Meta-analysis showed non-significant differences (p = .27) among these crops with respect to their response of R:S to the two tillage practices. Rapeseed and barley exhibited higher R:S in NT by 2% and 15%, while maize and wheat demonstrated higher R:S in CT by 2% and 6%, respectively, although the effects where not significant. In terms of soil texture classes, crops grown in sandy soils had a higher R:S under CT than NT, but no significant differences were found (p = .19). However, significant differences emerged among soil textures, with silty clay, sandy loam and clay loam showing the highest R:S (p < .05) while a cluster of sandy clay loam, clay and loam had lower R:S. Additionally, dicot crops displayed an 8% higher R:S under NT compared with CT, although this was not statistically significant (p = .24). Results indicated no significant differences (p = .22) in R:S between deep (>30 cm) and shallow (<30 cm) root sampling depths. The findings
... To estimate rhizodeposition, a ratio of 0.5 between net rhizodeposition and belowground biomass typical for grassland species was adopted, as used in Pausch and Kuzyakov (2018). Finally, a carbon concentration of 45% of the plant biomass was assumed (Kätterer et al. 2012). For the decomposability of the monthly grass input, decomposable plant material (DPM), and resistant plant material (RPM) (the DPM:RPM ratio) for the different residue components (i.e. ...
Article
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Purpose Agri-food systems across the globe are faced with the challenge of reducing their supply-chain emissions of greenhouse gases (GHGs) such as nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4). For instance, 10% of the UK’s GHG emissions are generated by agriculture, and ~ 56% of these are generated by livestock production. Numerous mitigation measures are being proposed to reduce GHG emissions from ruminants (representing 70 to 80% of total livestock emissions), particularly from beef cattle (presenting 30–40% of total livestock emissions). Methods To explore such potential, first, a business-as-usual (BAU) partial cradle-to-finishing farmgate scale modelling framework was developed. The BAU systems (i.e. steady-state productivity based on primary data from the North Wyke Farm Platform) were built using ensemble modelling wherein the RothC process-based soil organic carbon (SOC) model was integrated into the life cycle assessment (LCA) framework to conduct a trade-off analysis related to mitigation measures applicable to the study system. Potential mitigation measures were applied to the BAU scenario. The interventions assessed included: (i) extensification; (ii) adopting anaerobic digestion technology; and (iii) the use of the nitrification inhibitor DCD and substitution of fertiliser nitrogen with symbiotically fixed nitrogen from legumes. Results The partial carbon footprint for 1 kg of beef liveweight gain leaving the farmgate could be reduced by 7.5%, 12%, or 26% by adopting nitrification inhibitors, white clover introduction (pending establishment success), and anaerobic digestion for manure management, respectively. Conclusions The findings highlight the importance of including emissions beyond the farmgate level to analyse the carbon footprint of different management scenarios in order to assess the sustainability of agri-food production systems.
... The quality of C input differs between sources, e.g., root C input and straw. It is known that root C has a residence time in soils two to three times longer than that of other crop residues or manure-derived C inputs (Kätterer et al. 2012;Menichetti et al. 2015) and is therefore more effective at maintaining and building up SOC. This interpretation is underlined by the fact that the C-storage efficiency in Kiel was similar high even though this site stored more initial C in the fine silt and clay fraction (Fig. 4). ...
Article
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Background and aims According to the carbon (C) saturation concept, the capacity of soils to accumulate stabilized organic C is limited by the number of binding sites on mineral surfaces. The concept and its application are highly debated. Therefore, we aimed at testing this theory using field experimental data. Methods Soils were sampled from four long-term field experiments with different amounts of organic fertilisation going up to extreme high C inputs (20 Mg C ha⁻¹ yr⁻¹) five times higher than in common agricultural practice. Soils were fractionated by particle size to obtain sand-sized, coarse silt and fine silt plus clay fractions. Results We found a linear relation between C input and soil organic carbon stocks (SOC) even with vast amounts of organic C inputs to the soil at three experimental sites. Across all experiments, C stocks in the sand-sized fraction increased on average by 146%, whereas C stocks in the fine silt plus clay fraction (< 20 µm) increased by just 17% without distinct saturation behaviour. The C sequestration efficiency (amount of C retained as SOC per amount of C input) tended to increase with initial SOC content which is not in line with the saturation theory. Conclusion The experiments were subject to C inputs via organic fertilisation that would and should rarely be reached in agricultural practice due to negative side effects. Even under these artificial conditions experiments did not show a distinct saturation behaviour. Initial SOC stocks or SOC in the mineral-associated fraction did not appear to limit the potential of soils to sequester additional SOC. It can be concluded that C sequestration is mainly limited by the availability of C inputs from biomass.
... It is estimated that the top 30cm of soil store 700 Pg soil organic carbon (SOC) globally -this is almost equivalent to the quantity of carbon stored in the atmosphere (870 Pg C in 2018) (Kopittke et al., 2019). As a result, changes in SOC stock can affect atmospheric CO 2 concentration (Kätterer et al., 2012). Increasing SOC stocks in agricultural land is considered an attractive negative emission technology which yields benefits for soil quality and fertility and does not require further land-use conversions (Paustian et al., 2019). ...
Preprint
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This Deliverable provides a roadmap to expansion of BESTMAP towards a operational pan-European modelling platform, as well as explore via pilot analyses several areas for improvement and future research. Considering new case studies, we analyse the locations where models parameterized in those regions can transfer to cover the most area. We conclude that in future case studies, they should be located in northern Spain, north-west Italy, central Italy, Montenegro/Albania, and Bulgaria. Testing if one can model water quality at the European scale, our modelling shows the NDR model (used in BESTMAP CS work) has generally good performance at EU scale, despite it being a rather simple process-based model. There is an overestimation of Nitrogen at low N, and underestimation of Phosphate at high P, which need to be considered in future work.
... Enhancing management practices can be achieved by reducing the duration of exposed soil, increasing the recycling of organic substances, and promoting crop yields through nitrogen supplementation. The optimal approach is to enhance photosynthesis, since minimizing tillage and increasing crop yield might lead to a reduction in soil carbon storage (Kätterer et al, 2012). ...
Article
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Climate change, a long-term alteration in weather patterns, is reshaping ecosystems and industries worldwide, with profound implications for agriculture, biodiversity, and human health. This review paper explores the multifaceted impacts of climate change, emphasizing its effects on global agriculture, forest ecosystems, and marine environments. Rising temperatures, increased carbon dioxide levels, and changing precipitation patterns are leading to decreased crop yields, increased pest populations, and altered ecosystem dynamics. The study highlights the need for global and local adaptation strategies, including improved crop management, sustainable forestry practices, and enhanced carbon sequestration methods. In particular, developing nations like India are facing severe challenges, necessitating robust and immediate adaptation measures to mitigate the adverse effects on food security and economic stability. The review underscores the urgency of interdisciplinary approaches and innovative policies to address the complex and evolving challenges posed by climate change.
... [32]. In northern Europe [33], the application of nitrogen fertilizers is used as a strategy to increase carbon stocks in agricultural soils, indicating that carbon reserves can increase from 1 to 2 kg of C per kg of applied mineral N fertilizer. In [34], it is shown how the application of organic manure, such as cow dung in alfalfa and grasslands, enhances soil quality and carbon sequestration due to increased organic biomass. ...
Preprint
Carbon sequestration is a key strategy to mitigate greenhouse gas emissions, especially carbon dioxide (CO2). This literature review analyzes various agricultural practices and remote monitoring models applied to carbon sequestration in Latin America. It evaluates the impact of practices such as irrigation, organic agriculture, the use of fertilizers and amendments in grasslands, on increasing carbon in the region's soils. Additionally, it studies the application of remote monitoring models such as NDVI, MODIS, RothC and SPOT to collect data through satellite imagery. The results reveal that these agricultural practices and monitoring models are poorly implemented in Latin America. This highlights the importance of promoting their adoption to optimize carbon sequestration in different areas of the region. Greater carbon capture in soils would contribute significantly to mitigating climate change and achieving emission reduction goals. Therefore, it is essential to promote policies and incentives that drive these sustainable practices in the Latin American agricultural sector.
... Litter decomposition is a complex biogeochemical process controlled by several biotic and abiotic factors, where the biological activity of decomposers varies with soil properties and is driven largely by climatic conditions (Daebeler et al., 2022;Bradford et al., 2016;Cleveland et al., 2014;Gholz et al., 2000). Decomposition and SOC stabilization are long-term processes; therefore, long-term field experiments (LTEs) are among the most useful resources for quantifying the impact of management practices on litter decomposition, SOC changes and soil functioning Kätterer et al., 2012;Bergkvist and Öborn, 2011). Within LTEs, in situ experiments determining litter mass loss over time are important for understanding SOC dynamics, nutrient cycling and colonization by soil biota under field conditions. ...
Article
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Litter decomposition is an important factor affecting local and global C cycles. It is known that decomposition through soil microbial activity in ecosystems is mainly influenced by soil type and climatic conditions. However, for agroecosystems, there remains a need for a better understanding of how management practices influence litter decomposition. This study examined the effect of different management practices on decomposition at 29 sites with long-term (mean duration of 38 years) field experiments (LTEs) using the Tea Bag Index (TBI) protocol with standard litter (rooibos and green tea) developed by Keuskamp et al. (2013). The objective was to determine if the TBI decomposition rate (k) and stabilization factor (S) are sensitive enough to detect differences in litter decomposition between management practices as well as how they interact with edaphic factors, crop type and local climatic conditions. Tea bags were buried and collected after ∼90 d at 16 Austrian and 13 Swedish sites. The treatments in the Austrian LTEs focused on mineral and organic fertilizer application, tillage systems and crop residue management, whereas those in Sweden addressed cropping systems, mineral fertilizer application and tillage systems. The results for Austria showed that the incorporation of crop residue and high-N fertilizer application increased k, compared with crop residue removal and low or no N application, respectively. Minimum tillage had significantly higher k compared with reduced and conventional tillage. In Sweden, fertilized plots showed higher S than non-fertilized plots and high-N fertilizer had the highest k. Growing spring cereal led to higher k than forage crops. Random forest regressions for Austria and Sweden jointly showed that k and S were mainly governed by climatic conditions, which explained more than 70 % of their variation. However, under similar climatic conditions, management practices strongly influenced decomposition dynamics. It would be appropriate to apply the TBI approach to a more large-scale network using LTEs for agroecosystems, in order to improve the index's usefulness as an indicator of the effect of management practices on litter decomposition dynamics, particularly linking it with the potential for C storage.
... The results of these trials suggest that reduced tillage on its own appears to have very limited potential for increasing carbon sequestration in soil, and this measure does not fulfil expectations for a management practice that increases soil carbon pools at depth. This conclusion accords with that of Kätterer et al. (2012), with respect to the role of reduced tillage for carbon storage under Nordic conditions. Reduced tillage in combination with the use of cover crops may have some potential, as this may increase the amount of carbon returned to the soil. ...
Article
Carbon content is a key property of soils with importance for all ecosystem functions. Measures to increase soil carbon storage are suggested with the aim to compensate for agricultural emissions. In Norway, where soils have relatively high carbon content because of the cold climate, adapting management practices that prevent the loss of carbon to the atmosphere in response to climate change is also important. This work presents an overview of the potential for carbon sequestration in Norway from a wide range of agricultural management practices and provides recommendations based on certainty in the reported potential, availability of the technology, and likelihood for implementation by farmers. In light of the high priority assigned to increased food production and degree of self‐sufficiency in Norway, the following measures were considered: (1) utilization of organic resources, (2) use of biochar, (3) crop diversification and the use of cover crops, (4) use of plants with larger and deeper root systems, (5) improved management of meadows, (6) adaptive grazing of productive grasslands (7) managing grazing in extensive grasslands, (8) altered tillage practices, and (9) inversion of cultivated peat with mineral soil. From the options assessed, the use of cover crops scored well on all criteria evaluated, with a higher sequestration potential than previously estimated (0.2 Mt CO 2 ‐equivalents annually). Biochar has the largest potential in Norway (0.9 Mt CO 2 ‐equivalents annually, corresponding to 20% of Norwegian agricultural emissions and 2% of total national emissions), but its readiness level is not yet achieved despite interest from industry to apply this technology at large scale. Extensive grazing and the use of deep‐rooted plants also have the potential for increasing carbon storage, but there is uncertainty regarding their implementation and the quantification of effects from adapting these measures. Based on the complexities of implementation and the expected impacts within a Norwegian context, promising options with substantial payoff are few. This work sheds light on the knowledge gaps remaining before the presented measures can be implemented.
... The difference in the response of the two tested soils to copper is consistent with the literature. Indeed, some studies reported little or no inhibition of peat decomposition following copper application Kätterer et al., 2012;Minnich and McBride, 1986;Mathur and Rayment, 1977), while others reported marked inhibition Mathur and Sanderson, 1978;Mathur and Rayment, 1977). Conflicting results have also been reported for mineral soils contaminated with heavy metals, including copper (Giller et al., 2009). ...
Article
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Drained agricultural peatlands are subject to degradation through decomposition, compaction, and erosion. This study aimed to (1) revisit an existing recommendation to systematically apply copper at a rate exceeding crop needs to slow the decomposition of agricultural peatlands, and (2) explore lignosulfonate, a polyphenol, as an alternative method to copper. Two peat soils with contrasting levels of humification (sapric and hemic) and differing Al and Fe contents were studied under controlled conditions. CO2 emissions cumulated in the two unamended soils differed importantly, representing 0.7 and 7.3 t C-CO2 ha-1 yr-1 (0-25 cm) in the sapric and hemic soil, respectively. In the sapric soil, copper did not affect CO2 emissions, N and P parameters, or the activity of most of the measured enzymes. In the same soil, lignosulfonate increased CO2 emissions and phenol oxidase activity, suggesting that the product acted as a microbial substrate. In the hemic soil, copper and lignosulfonate reduced cumulated CO2 emissions by 37% and 61%, respectively, as well as N parameters and phosphatase activity. The influence of both treatments on CO2 emissions was, however, temporary. This study suggests limited efficiency of copper and lignosulfonate when applied to soils where underlying mechanisms, such as organic matter recalcitrance and Al and Fe stabilization effect, already regulate decomposition rates. The divergent and temporary effects of copper found in this study and in the literature suggest that routine applications of copper at a rate exceeding crop needs is not consistently effective in slowing decomposition in agricultural peatlands. Lignosulfonate appears to be a promising alternative to copper. The inhibitory effect of polyphenol applications has been demonstrated in natural peatlands but, to our knowledge, this is the first time it has been reported for drained agricultural peatlands. Evaluating the influence of lignosulfonate on other drained agricultural peat soils and under field conditions is necessary to determine the potential of this approach.
... These results match the meta-analysis of Geisseler and Scow (2014), in which SOC content increased by 8.5% on average upon adding mineral N fertilizer. Kätterer et al. (2012) also reported an annual increase in SOC by 1-2 kg ha − 1 for each kg of mineral N fertilizer applied in Swedish long-term cropland fertilization experiments. ...
Article
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Most agroecosystems receive inputs of anthropogenically derived nutrients, which impact soil organic carbon (SOC). However, the impact of the combination of different fertilizer types, as well as of various amounts of nitrogen (N), phosphorus (P), and potassium (K) fertilization, on SOC remains to be determined. Here, we reviewed 212 published studies to identify the consequences of different types and levels of N, P, and K fertilization on SOC across northern hemisphere cropland soils. The average effect size of fertilization on SOC was 0.2707 ± 0.0086 (95% confidence interval: 0.2539–0.2875, p < 0.0001). Categorical variable analysis revealed that the fertilization type significantly influenced the effect size in mineral plus organic fertilization > pure organic fertilization > pure mineral fertilization. The increased available nutrients led to the retention of organic C from farmyard manure or crop straw and limited nutrient loss, increasing C sequestration. Intermediate N (100–300 kg ha−1 year−1) and K (50–150 kg ha−1 year−1) application with high P (>60 kg ha−1 year−1) fertilization produced the most significant effect on the SOC stocks. Heterogeneity analysis revealed that the annual average precipitation, annual average temperature, water conditions, and tillage type significantly affected the average effect size. Overall, the meta-analysis revealed that multi-nutrient fertilization, with intermediate N and K levels and a high P level, decreased the dependency of the organisms released from SOM decomposition and had strong positive effects on increasing SOC in agroecosystems.
... Indeed, Li et al. (2021) Plant Soil found that the amount of oxalic acid was significantly increased with N addition and this acid is acknowledged to destabilise C via ligand weathering and exchange. At first glance, the observation that N addition stimulated C mineralisation in the present study might be a contradiction to the often-reported positive effect of N fertilisation on SOC stocks (Alvarez 2005;Kätterer et al. 2012;Tang et al. n.d.). However, as discussed above, the effects of N fertilisation on the soil C balance, considering inputs and outputs, are manifold. ...
Article
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Background and aims Understanding the fate and residence time of organic matter added to soils, and its effect on native soil organic carbon (SOC) mineralisation is key for developing efficient SOC sequestration strategies. Here, the effect of litter quality, particularly the carbon-to-nitrogen (C:N) ratio, on the dynamics of particulate (POC) and mineral-associated organic carbon (MAOC) were studied. Methods In a two-year incubation experiment, root litter samples of the C4-grass Miscanthus with four different C:N ratios ranging from 50 to 124 were added to a loamy agricultural topsoil. In an additional treatment, ammonium nitrate was added to the C:N 124 litter to match the C:N 50 litter input ratio. Soils were size-fractionated after 6, 12 and 24 months and δ¹³C was measured to determine the proportion of new and native POC and MAOC. Litter quality was further assessed by mid-infrared spectroscopy and compound peak analysis. Results Litter quality strongly affected SOC dynamics, with total SOC losses of 42.5 ± 3.0% in the C:N 50 treatment and 48.9 ± 3.0% in the C:N 124 treatment after 24 months. Largest treatment effects occurred in mineralisation of native MAOC, which was strongly primed by litter addition. The N amendment in the C:N 124 treatment did not alleviate this potential N mining flux. Conclusion Litter quality plays a major role in overall SOC dynamics, and priming for N mining from the MAOC pool could be a dominant mechanism. However, adding N did not compensate for poor litter quality, highlighting the role of litter quality beyond stoichiometric imbalances.
... SOC stocks rose with increasing mineral N fertilisation (Fig. 3). While Kätterer et al. (2012) report a 1/1 OC sequestration rate, meaning that every mass unit of N applied results in the same amount of OC increase in the topsoil, the present results suggested a lower sequestration rate of 1/0.6 in the topsoil and of 1/0.2 in the subsoil. The average duration of the experiments at the sites included was close to 60 years in both studies. ...
Article
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Agricultural management can influence soil organic carbon (SOC) stocks and thus may contribute to carbon sequestration and climate change mitigation. The soil depth to which agricultural management practices affect SOC is uncertain. Soil depth may have an important bearing on soil carbon dynamics, so it is important to consider depth effects to capture fully changes in SOC stocks. This applies in particular to the evaluation of carbon farming measures, which are becoming increasingly important due to climate change. We sampled and analysed the upper metre of mineral cropland soils from ten long-term experiments (LTEs) in Germany to quantify depth-specific effects on SOC stocks of common agricultural management practices: mineral nitrogen (N) fertilisation, a combination of N, phosphorus (P) and potassium (K) fertilisation, irrigation, a crop rotation with preceding crops (pre-crops), straw incorporation, application of farmyard manure (FYM), liming, and reduced tillage. In addition, the effects of soil compaction on SOC stocks were examined as a negative side effect of agricultural management. Results showed that 19 ± 3 % of total management effects on SOC stocks were found in the upper subsoil (30-50 cm) and 3 ± 4 % in the lower subsoil (50-100 cm), including all agricultural management practices with significant topsoil SOC effects, while 79 ± 7 % of management effects were in the topsoil (0-30 cm). Nitrogen and NPK fertilisation were the treatments that had the greatest effect on subsoil organic carbon (OC) stocks, followed by irrigation, FYM application and straw incorporation. Sampling down to a depth of 50 cm resulted in significantly higher SOC effects than when considering topsoil only. A crop rotation with pre-crops, liming, reduced tillage and soil compaction did not significantly affect SOC stocks at any depth increment. Since approximately 20 % of the impact of agricultural management on SOC stocks occurs in the subsoil, we recommend soil monitoring programs and carbon farming schemes extend their standard soil sampling down to 50 cm depth to capture fully agricultural management effects on SOC.
... In general, carbon sequestration increases when grassland management is intensified including an increase of nutrient inputs especially nitrogen (Kätterer et al. 2012). Therefore, low input grasslands and set-aside areas usually have a lower carbon sequestration potential. ...
Technical Report
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Soils play a central role in climate mitigation. They are both as a carbon sink and a source of greenhouse gas emissions (GHG). This report outlines the mitigation potential for GHG emissions of climate friendly soil management options at global, EU and German level. It also discusses different types of climate-friendly soil management measures and key considerations for their implementation.
... SOC stocks rose with increasing mineral N fertilisation (Fig. 3). While Kätterer et al. (2012) report a 1/1 OC sequestration rate, meaning that every mass unit of N applied results in the same amount of OC increase in the topsoil, the present results suggested a lower sequestration rate of 1/0.6 in the topsoil and of 1/0.2 in the subsoil. The average duration of the experiments at the sites included was close to 60 years in both studies. ...
Article
Full-text available
Agricultural management can influence soil organic carbon (SOC) stocks and thus may contribute to carbon sequestration and climate change mitigation. The soil depth to which agricultural management practices affect SOC is uncertain. Soil depth may have an important bearing on soil carbon dynamics, so it is important to consider depth effects to capture fully changes in SOC stocks. This applies in particular to the evaluation of carbon farming measures, which are becoming increasingly important due to climate change. We sampled and analysed the upper metre of mineral cropland soils from ten long-term experiments (LTEs) in Germany to quantify depth-specific effects on SOC stocks of common agricultural management practices: mineral nitrogen (N) fertilisation, a combination of N, phosphorus (P) and potassium (K) fertilisation, irrigation, a crop rotation with preceding crops (pre-crops), straw incorporation, application of farmyard manure (FYM), liming, and reduced tillage. In addition, the effects of soil compaction on SOC stocks were examined as a negative side effect of agricultural management. Results showed that 19 ± 3 % of total management effects on SOC stocks were found in the upper subsoil (30–50 cm) and 3 ± 4 % in the lower subsoil (50–100 cm), including all agricultural management practices with significant topsoil SOC effects, while 79 ± 7 % of management effects were in the topsoil (0–30 cm). Nitrogen and NPK fertilisation were the treatments that had the greatest effect on subsoil organic carbon (OC) stocks, followed by irrigation, FYM application and straw incorporation. Sampling down to a depth of 50 cm resulted in significantly higher SOC effects than when considering topsoil only. A crop rotation with pre-crops, liming, reduced tillage and soil compaction did not significantly affect SOC stocks at any depth increment. Since approximately 20 % of the impact of agricultural management on SOC stocks occurs in the subsoil, we recommend soil monitoring programs and carbon farming schemes extend their standard soil sampling down to 50 cm depth to capture fully agricultural management effects on SOC.
... There was still an increase from 2008 to 2019. The lack of effects of mineral fertilizer N on the SOC in soil contradicts to some extent earlier findings (e.g., Kätterer et al., 2012;Poffenbarger et al., 2017;Powlson et al., 2011). This is probably related to the net mineralization of organic matter, which is indicated by a higher N offtake than N supply (Table 3). ...
Article
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Background Fertilization with organic waste compost can close the nutrient cycles between urban and rural environments. However, its effect on yield and soil fertility must be investigated. Aim This study investigated the long‐term effect of compost on soil nutrient and potentially toxic elements (PTEs) concentration, nutrient budgets, and nitrogen (N) mineralization and efficiency. Methods After 21 years of annual compost application (100/400 kg N ha –1 year –1 [100BC/400BC]) alone and combined with mineral fertilization, soil was analyzed for pH, organic carbon (SOC), nutrient (total N and P, N min , extractable CAL‐P, CAL‐K, and Mg), and PTE (Cu, Ni, Zn) concentrations. Yields were recorded and nutrient/PTE budgets and apparent net mineralization (ANM, only 2019) were calculated. Results N efficiency was the highest in maize and for mineral fertilization. Compost application led to lower N efficiencies, but increased ANM, SOC, pH, and soil N, and surpluses of N, P, and all PTEs. Higher PTE concentrations were only found in 400BC for Cu. Nutrient budgets correlated with soil nutrient concentration. A surplus of 16.1 kg P ha –1 year –1 and 19.5 kg K ha –1 year –1 resulted in 1 mg kg –1 increase in CAL‐P and CAL‐K over 21 years. Conclusion Compost application supplies nutrients to crops with a minor risk of soil‐accumulation of PTEs. However, the nutrient stoichiometry provided by compost does not match crop offtakes causing imbalances. Synchronization of compost N mineralization and plant N demand does not match and limits the yield effect. In winter wheat only 65–70% of N mineralization occurred during the growth period.
... For a given crop production, C returns to soils increase with NPP (Basile-Doelsch et al. 2020). Thus, increasing NPP per unit area is probably the most effective option to enhance SOC sequestration (Kätterer et al. 2012). Maximizing agroecosystem NPP can be realized by large-scale irrigation, increase in the availability of soluble nutrient sources (fertilizers), agricultural mechanization, improved varieties and application of agrochemicals for pest control (Whalen and Sampedro 2009). ...
Chapter
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.
... 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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Background 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. Aims 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. Methods 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. Results 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. Conclusions 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. ...
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... 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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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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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.
Thesis
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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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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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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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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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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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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.
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As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on >2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers. Plant functional types significantly affected the v...