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Scientific publications

Reviewed journals 2015

Management of agricultural soils for greenhouse gas mitigation: Learning from a case study in NE Spain / Sánchez B, Iglesias A, McVittie A, Alvaro-Fuentes J, Ingram J, Mills J, Lesschen JP, Kuikman P 

Abstract

A portfolio of agricultural practices is now available that can contribute to reaching European mitigation targets. Among them, the management of agricultural soils has a large potential for reducing GHG emissions or sequestering carbon. Many of the practices are based on well tested agronomic and technical know-how, with proven benefits for farmers and the environment. A suite of practices has to be used since none of the practices can provide a unique solution. However, there are limitations in the process of policy development: (a) agricultural activities are based on biological processes and thus, these practices are location specific and climate, soils and crops determine their agronomic potential; (b) since agriculture sustains rural communities, the costs and potential for implementation have also to be regionally evaluated and (c) the aggregated regional potential of the combination of practices has to be defined in order to inform abatement targets. We believe that, when implementing mitigation practices, three questions are important: Are they cost-effective for farmers? Do they reduce GHG emissions? What policies favour their implementation? This study addressed these questions in three sequential steps. First, mapping the use of representative soil management practices in the European regions to provide a spatial context to upscale the local results. Second, using a Marginal Abatement Cost Curve (MACC) in a Mediterranean case study (NE Spain) for ranking soil management practices in terms of their cost-effectiveness. Finally, using a wedge approach of the practices as a complementary tool to link science to mitigation policy. A set of soil management practices was found to be financially attractive for Mediterranean farmers, which in turn could achieve significant abatements (e.g., 1.34 MtCO2e in the case study region). The quantitative analysis was completed by a discussion of potential farming and policy choices to shape realistic mitigation policy at European regional level.

Published in: Journal of Environmental Management, (2016) 170, 37-49.

doi: 10.1016/j.jenvman.2016.01.003


Endospores, prokaryotes, and microbial indicators in arable  soils from three long-term experiments / Paulina Tamez-Hidalgo, Bent T. Christensen, Mark A. Lever, Lars Elsgaard, Bente Aa. Lomstein

Abstract

Management impacts on microbial communities in arable soil may influence soil quality and fertility. We exam- ined the composition of the prokaryotic community in soils maintained under specific treatments for 24–118 years at Askov Experimental Station, Denmark. The experiments in- volved nutrient addition (unfertilized, mineral fertilizer, cattle manure), straw disposal (no straw, 8 t straw ha−1 year−1), and soil texture (5–18 % clay). Domain- and phylum-assigned cells were quantified by 16S ribosomal RNA (rRNA) gene analysis and endospores by analysis of dipicolinic acid (DPA). Amino sugars (glucosamine, galactosamine, and muramic acid) were assayed as microbial source indicators. Severe nutrient depletion reduced cell numbers and increased endospore abundance; straw disposal slightly increased both prokaryote and endospore numbers. Nutrient source (animal manure or mineral fertilizer) and soil texture had a little effect on cell and endospore numbers. With the notable exception of unfertilized soil, the ratio of endospores to total cells was similar across all treatments. The 16S rRNA gene analysis showed dominance of Bacteria over Archaea, the latter ac- counting for 0.2–8.4 % of total genes. Archaeal abundance differed a little among treatments. Firmicutes made up 0.2–1.2 % of the bacterial 16S rRNA genes. The numbers of Firmicutes were lower in unfertilized than in fertilized soil and decreased with decreasing soil clay content; straw treat- ment and nutrient source had a little effect. Amino sugar ratios suggested a dominance of fungi over bacteria, but the concen- trations of microbial indicators and soil organic C were closely correlated, indicating that the amino sugar ratios represented a historical fingerprint (legacy effect) of the impact of manage- ment on the microbial community. Our results show that it takes extreme management to distort the general structure of prokaryotic communities in temperate arable soils.

Published in Biol Fertil Soils

doi: 10.1007/s00374-015-1057-5


Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long‑term bare fallow experiments / Lorenzo Menichetti, Sabine Houot, Folkert van Oort,
Thomas Kätterer, Bent T. Christensen, Claire Chenu, Pierre Barré,  Nadezda A. Vasilyeva & Alf Ekblad

Abstract

Changes in the 12C/13C ratio (expressed as δ13C) of soil organic C (SOC) has been observed over long time scales and with depth in soil profiles. The changes are ascribed to the different reaction kinetics of 12C and 13C isotopes and the different isotopic composition of various SOC pool components. However, experimental verification of the subtle isotopic shifts associated with SOC turnover under field conditions is scarce. We determined δ13C and SOC in soil sampled during 1929–2009 in the Ap-horizon of five European long-term bare fallow experiments kept without C inputs for 27–80 years and covering a latitudinal range of 11°. The bare fallow soils lost 33–65 % of
their initial SOC content and showed a mean annual δ13C increase of 0.008–0.024 ‰. The 13C enrichment could be related empirically to SOC losses by a Rayleigh distillation equation. A more complex mechanistic relationship was also examined. The overall estimate of the fractionation
coefficient (ε) was −1.2 ± 0.3 ‰. This coefficient represents an important input to studies of long-term SOC dynamics in agricultural soils that are based on variations in 13C natural abundance. The variance of ε may be ascribed to site characteristics not disclosed in our study, but the very similar kinetics measured across our five experimental sites suggest that overall site-specific factors (including climate) had a marginal influence and that it may be possible to isolate a general mechanism causing the enrichment, although pre-fallow land use may have some impact on isotope
abundance and fractionation.

Published in: Oecologia (2015) 177:811–821

doi: 10.1007/s00442-014-3114-4


Relationship between C:N/C:O Stoichiometry and Ecosystem Services in Managed Production Systems / Bhim B. Ghaley, Harpinder S. Sandhu & John R. Porter

Abstract

Land use and management intensity can influence provision of ecosystem services (ES). We argue that forest/agroforestry production systems are characterized by relatively higher C:O/C:N and ES value compared to arable production systems. Field investigations on C:N/ C:O and 15 ES were determined in three diverse production systems: wheat monoculture (Cwheat), a combined food and energy system (CFE) and a beech forest in Denmark. The C: N/C:O ratios were 194.1/1.68, 94.1/1.57 and 59.5/1.45 for beech forest, CFE and Cwheat, respectively. The economic value of the non-marketed ES was also highest in beech forest (US$ 1089 ha-1 yr-1) followed by CFE (US$ 800 ha-1 yr-1) and Cwheat (US$ 339 ha-1 yr-1). The combined economic value was highest in the CFE (US$ 3143 ha-1 yr-1) as compared to the Cwheat (US$ 2767 ha-1 yr-1) and beech forest (US$ 2365 ha-1 yr-1). We argue that C:N/C: O can be used as a proxy of ES, particularly for the non-marketed ES, such as regulating, supporting and cultural services. These ES play a vital role in the sustainable production of food and energy. Therefore, they should be considered in decision making and developing appropriate policy responses for land use management.

Published in: PLOS ONE | April 20, 2015

doi:10.1371/journal.pone.0123869 


Do soil organic carbon levels affect potential yields and nitrogen use efficiency? An analysis of winter wheat and spring barley field trials / Myles Oelofse, Bo Markussen, Leif Knudsen, Kirsten Schelde, Jørgen E. Olesen,Lars Stoumann Jensen, Sander Bruun

Abstract

Soil organic carbon (SOC) is broadly recognised as an important parameter affecting soil quality, and can therefore contribute to improving a number of soil properties that influence crop yield. Previous research generally indicates that soil organic carbon has positive effects on crop yields, but in many studies it is difficult to separate the effect of nutrients from the effect of SOC in itself. The aim of this study was to analyze whether the SOC content, in itself, has a significant effect on potential yields of commonly grown cereals across a wider range of soil types in Denmark. The study draws on historical data sets from the Danish national field trials consisting of 560 winter wheat (Triticum aestivum L.) trials and 309 spring barley (Hordeum vulgare L.) trials conducted over the past 20 and 17 years, respectively. We hypothesised that for these two crops, the potential grain yield, the yield with no fertiliser N application and the N use efficiency would be positively affected by SOC level. A statistical model was developed to explore relationships between SOC and potential yield, yields at zero N application and N use efficiency (NUE). The model included a variety of variables and aimed to elucidate the sole effect of SOC by controlling for potential confounding variables. No significant effect of SOC on potential winter wheat was found,whilst for spring barley, only for the course sandy loam soil type was a borderline significantly positive effect of SOC on potential yields found. The relationship between unfertilized plot yields and SOC was positive for winter wheat, although not significant, whilst for spring barley a significant positive effect of SOC was found only for the coarse sandy soil type, and a borderline significant positive effect of SOC was found for the coarse sandy loam soil type. A significant negative relationship was found between SOC and NUE for both winter wheat and spring barley. Based on the large data set analyzed, we cautiously challenge the importance of SOC in contributing to crop productivity in contexts with similar soils and climate, and we speculate that in situations where nutrient limitation does not occur, SOC levels above 1% may be sufficient to sustain yields. In light of the findings presented in this study, further work should be conducted which can further elucidate the effect of SOC on yields.

Published in: Europ. J. Agronomy 66 (2015) 62–73

doi: 10.1016/j.eja.2015.02.009


Estimating the Costs and Benefits of Adapting Agriculture to Climate Change / Anita Wreford, Dominic Moran, Andrew Moxey, K. Andy Evans, Noami Fox, Klaus Glenk, Mike Hutchings, Davy I. McCracken, Alistair McVittie, Malcolm Mitchell, Cairistiona F.E. Topp, Eileen Wall

Abstract

A changing climate will inevitably impact on the natural environment, including agriculture. Anticipatory adaptation is necessary to minimise the negative impacts of climate change, to take advantage of opportunities, and to ensure that food and fibre production is maintained. More detailed information is required as to which adaptation measures will yield relatively greater social rates of return. Such information would help define an efficient adaptation agenda in the agricultural sector. This article identifies key adaptation strategies across England's agricultural sector, and applies cost–benefit analysis to these to determine their net present values, highlighting where the greatest returns can be made, and the role for policy. The results span a wide range, with some soil management activities indicating a negative NPV of £122 million over the course of this century, to a positive NPV of £3,279 million in the case of some livestock adaptations to heat stress. Animal disease surveillance and peatland restoration also generated high NPVs of £1,850 million and £1,840 million, respectively. Adaptations addressing crop disease, water storage measures and managed coastal realignment generated more modest values ranging from £1 million to £61 million. Direct comparison of the numbers is misleading however as some refer to the national level while others are site-specific. The analysis provides a basis for a discussion on priorities and planning for adaptation in the agricultural sector.

Published in: EuroChoices (14) Issue 2; 16-23

doi: 10.1111/1746-692X.12086


The economics of soil C sequestration and agricultural emissions abatement /P. Alexander, K. Paustian, P. Smith, D. Moran

Abstract

Carbon is a critical component of soil vitality and is crucial to our ability to produce food. Carbon sequestered in soils also provides a further regulating ecosystem service, valued as the avoided damage from global climate change. We consider the demand and supply attributes that underpin and constrain the emergence of a market value for this vital global ecosystem service: markets being what economists regard as the most efficient institutions for allocating scarce resources to the supply and consumption of valuable goods. This paper considers how a potentially large global supply of soil carbon sequestration is reduced by economic and behavioural constraints that impinge on the emergence of markets, and alternative public policies that can efficiently transact demand for the service from private and public sector agents. In essence, this is a case of significant market failure. In the design of alternative policy options, we consider whether soil carbon mitigation is actually cost-effective relative to other measures in agriculture and elsewhere in the economy, and the nature of behavioural incentives that hinder policy options. We suggest that reducing the cost and uncertainties of mitigation through soil-based measures is crucial for improving uptake. Monitoring and auditing processes will also be required to eventually facilitate wide-scale adoption of these measures.

Published in: SOIL 1, 331-339

doi: 10.5194/soil-1-331-2015


Greenhouse gas intensity of three main crops and implications for low-carbon agriculture in China / Wen Wang, Liping Guo, Yingchun Li, Man Su, Yuebin Lin, Christian de Perthuis, Xiaotang Ju, Erda Lin, Dominic Moran

Abstract

China faces significant challenges in reconciling food security goals with the objective of becoming a low-carbon economy. Agriculture accounts for approximately 11 % of China’s national greenhouse gas (GHG) emissions with cereal production representing a large proportion (about 32 %) of agricultural emissions. Minimizing emissions per unit of product is a policy objective and we estimated the GHG intensities (GHGI) of rice, wheat and maize production in China from 1985 to 2010. Results show significant variations of GHGIs among Chinese provinces and regions. Relative to wheat and maize, GHGI of rice production is much higher owing to CH4 emissions, and is more closely related to yield levels. In general, the south and central has been the most carbon intensive region in rice production while the GHGI of wheat production is highest in north and northwest provinces. The southwest has been characterized by the highest maize GHGI but the lowest rice GHGI. Compared to the baseline scenario, a 2 % annual reduction in N inputs, combined with improved water management in rice paddies, would mitigate 17 % of total GHG emissions from cereal production in 2020 while sustaining the required yield increase to ensure food security. Better management practices will entail additional gains in soil organic carbon further decreasing GHGI. To realize the full mitigation potential while maximizing agriculture development, the design of appropriate policies should accommodate local conditions.

Published in: Climatic Change (128) Issue 1, 57-70

doi: 10.1007/s10584-014-1289-7


Global change pressures on soils from land use and management / Smith, P., House, J.I., Bustamante, M., Sobocká, J., Harper, R., Pan, G., West, P.C., Clark, J.M., Adhya, T., Rumpel, C., Paustian, K., Kuikman, P., Cotrufo, M.F., Elliott, J.A., McDowell, R., Griffiths, R.I., Asakawa, S., Bondeau, A., Jain, A.K, Meersmans, J. & Pugh, T.A.M.

Abstract

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land use change, land management, and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state-of-the-art understanding of these global change pressures on soils, identify knowledge gaps and research challenges, and highlight actions and policies to minimise adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development. This article is protected by copyright. All rights reserved.

Published in: Global Change Biology

doi: 10.1111/gcb.13068


Biogeochemical cycles and biodiversity as key drivers of ecosystem services provided by soils / Smith, P., Cotrufo, M.F., Rumpel, C., Paustian, K., Kuikman, P.J., Elliott, J. A., McDowell, R., Griffiths, R.I., Asakawa, S., Bustamante, M., House, J.I., Sobocká, J., Harper, R., Pan, G., West, P.C., Gerber. J.S., Clark, J.M., Adhya, T., Scholes, R.J. & Scholes, M.C. 

Abstract

Soils play a pivotal role in major global biogeochemical cycles (carbon, nutrient and water), while hosting the largest diversity of organisms on land. Because of this, soils deliver fundamental ecosystem services, and management to change a soil process in support of one ecosystem service can either provide co-benefits to other services or can result in trade-offs. In this critical review, we report the state-of-the-art understanding concerning the biogeochemical cycles and biodiversity in soil, and relate these to the provisioning, regulating, supporting and cultural ecosystem services which they underpin. We then outline key knowledge gaps and research challenges, before providing recommendations for management activities to support the continued delivery of ecosystem services from soils. 
We conclude that although there are knowledge gaps that require further research, enough is known to start improving soils globally. The main challenge is in finding ways to share knowledge with soil managers and policy-makers, so that best-practice management can be implemented. A key element of this knowledge sharing must be in raising awareness of the multiple ecosystem services underpinned by soils, and the natural capital they provide. The International Year of Soils in 2015 presents the perfect opportunity to begin a step-change in how we harness scientific knowledge to bring about more sustainable use of soils for a secure global society.

Published in: SOIL Discuss., 2, 537-586

doi: 10.5194/soild-2-537-2015

Reviewed journals 2014

Changes in carbon stocks of Danish agricultural mineral soils between 1986 and 2009 Arezoo Taghizadeh-Toosi, J. E. Olesen, K. Kristensen, L. Elsgaard, H. S. Østergaard, M. Lægdsmand,,M.H.Greve & B. T. Christensen.

Abstract

To establish a national inventory of soil organic carbon (SOC) stocks and their change over time, soil was sampled in 1986, 1997 and 2009 in a Danish nation-wide 7-km grid and analysed for SOC content. The average SOC stock in 0–100-cm depth soil was 142 t C ha−1, with 63, 41 and 38 t C ha−1 in the 0–25, 25–50 and 50–100 cm depths, respectively. Changes at 0–25 cm were small. During 1986–97, SOC in the 25–50-cm layer increased in sandy soils while SOC decreased in loam soils. In the subsequent period (1997–2009), most soils showed significant losses of SOC. From 1986 to 2009, SOC at 0–100 cm decreased in loam soils and tended to increase in sandy soils. This trend is ascribed to dairy farms with grass leys being abundant on sandy soils while cereal cropping dominates on loamy soils. A statistical model including soil type, land use and management was applied separately to 0–25, 25–50 and 50–100 cm depths to pinpoint drivers for SOC change. In the 0–25 cm layer, grass leys added 0.95 t C ha−1 year−1 and autumn-sown crops with straw incorporation added 0.40 t C ha−1 year−1. Cattle manure added 0.21 t C ha−1 year−1. Most interestingly, grass leys contributed 0.58 t C ha−1 year−1 at 25–50 cm, confirming that inventories based only on top-soils are incomplete. We found no significant effects in 50–100 cm. Our study indicates a small annual loss of 0.2 t C ha−1 from the 0–100 cm soil layer between 1986 and 2009.

Published in: European Journal of Soil Science September (2014), 65, 730–7.

doi: 10.1111/ejss.12169

C-TOOL: A simple model for simulating whole-profile carbon storage in temperate agricultural soils /Arezoo Taghizadeh-Toosi, Bent T. Christensen, Nicholas J. Hutchings, Jonas Vejlin,Thomas Kätterer, Margaret Glendining, Jørgen E. Olesen.

Abstract

Soil organic carbon (SOC) is a significant component of the global carbon (C) cycle. Changes in SOC storage affect atmospheric CO2 concentrations on decadal to centennial timescales. The C-TOOL model was developed to simulate farm- and regional-scale effects of management on medium- to long-term SOC storage in the profile of well-drained agricultural mineral soils. C-TOOL uses three SOC pools for both the topsoil (0–25 cm) and the subsoil (25–100 cm), and applies temperature-dependent first order kinetics to regulate C turnover. C-TOOL also enables the simulation of14C turnover. The simple model structure facilitates calibration and requires few inputs (mean monthly air temperature, soil clay content, soil C/N ratio and C in organic inputs). The model was parameterised using data from 19 treatments drawn from seven long-term field experiments in the United Kingdom, Sweden and Denmark. It was found that the initial SOC content had to be optimised for each experiment, but also that one set of values for other model parameters could be applied at all sites. With this set of parameters, C-TOOL can be applied more widely to evaluate effects of management options on SOC storage in temperate agricultural soils. C-TOOL simulates observed losses of SOC in soils under intensive agricultural use and the gain in SOC derived from large inputs of animal manure and inclusion of perennial grassland. The model simulates changes in SOC for the entire profile, but lack of data on subsoil SOC storage hampers a proper model evaluation.Experimental verification of management effects on subsoil C storage, subsoil C inputs from roots, and vertical transport of C in the soil profile remains prioritised research areas.

Published in: Ecological Modelling 292 (2014) 11–25

doi: 10.1016/j.ecolmodel.2014.08.016


Towards mitigation of greenhouse gases by small changes in farming practices: understanding local barriers in Spain. / Berta Sánchez, Jorge Álvaro-Fuentes, Ruth Cunningham, Ana Iglesias

Abstract

Small changes in agricultural practices have a large potential for reducing greenhouse gas emissions. However, the implementation of such practices at the local level is often limited by a range of barriers. Understanding the barriers is essential for defining effective measures, the actual mitigation potential of the measures, and the policy needs to ensure implementation. Here we evaluate behavioural, cultural, and policy barriers for implementation of mitigation practices at the local level that imply small changes to farmers. The choice of potential mitigation practices relevant to the case study is based on a literature review of previous empirical studies. Two methods that include the stakeholders’ involvement (experts and farmers) are undertaken for the prioritization of these potential practices: (a) Multi-criteria analysis (MCA) of the choices of an expert panel and (b) Analysis of barriers to implementation based on a survey of farmers. The MCA considers two future climate scenarios – current climate and a drier and warmer climate scenario. Results suggest that all potential selected practices are suitable for mitigation considering multiple criteria in both scenarios. Nevertheless, if all the barriers for implementation had the same influence, the preferred mitigation practices in the case study would be changes in fertilization management and use of cover crops. The identification of barriers for the implementation of the practices is based on the econometric analysis of surveys given to farmers. Results show that farmers’ environmental concerns, financial incentives and access to technical advice are the main factors that define their barriers to implementation. These results may contribute to develop effective mitigation policy to be included in the 2020 review of the European Union Common Agricultural Policy.

Published in: J Mitigation and Adaptation Strategies for Global Change, April 2014

doi: 10.1007/s11027-014-9562-7


Managing Soil Organic Carbon: A Farm Perspective.  / Ingram, J., Mills, J., Frelih-Larsen, A., Davis, M., Merante, P., Ringrose, S., Molnar, A., Sánchez, B., Ghaley, B. B., Karaczun, Z.

Abstract

Farming practices that lead to declining returns and inputs of carbon to soils pose a threat to key soil functions. The EU FP7 interdisciplinary project SmartSOIL is using scientific testing and modeling to identify management practices that can optimise soil carbon storage and crop productivity. A consultation with advisors and policymakers in six European case study regions seeks to identify barriers to, and incentives for, uptake of such practices. Results from preliminary interviews are reported. Overall advisor and farmer awareness of management practices specifically directed towards soil carbon is low. Most production-related decisions are taken in the short term, but managing soil carbon needs a long-term approach. Key barriers to uptake of practices include: perceived scientific uncertainty about the efficacy of practices; lack of real life ‘best practice’ examples to show farmers; difficulty in demonstrating the positive effects of soil carbon management practices and economic benefits over a long time scale; and advisors being unable to provide suitable advice due to inadequate information or training. Most farmers are unconvinced of the economic benefits of practices for managing soil carbon. Incentives are therefore needed, either as subsidies or as evidence of the cost effectiveness of practices. All new measures and advice should be integrated into existing programmes to avoid a fragmented policy approach.

Published in: EuroChoices, 13: 12–19, 2014,

doi: 10.1111/1746-692X.12057


UK peatland restoration: Some economic arithmetic / A. Moxey and D. Moran

Abstract

Restoration of UK peatlands is currently being promoted as a means of both helping to mitigate climate change and adapting to it. However, formal economic analysis of the relative costs and benefits of restoration is hampered by scientific uncertainty and a lack of data on biophysical conditions as well as the impacts and costs of restoration. Consequently, there is a risk that the overall level of funding and/or targeting of restoration activities may be inappropriate. By presenting results of some simple economic arithmetic, this paper illustrates how the merits of restoration vary with different assumed circumstances. Specifically, generating a ‘ready reckoner’ of possible net economic benefits allows exploration of a range of ‘what if?’ combinations of parameter values. The ready reckoner results suggest that in many, but not all, cases the circumstances under which restoration appears to be merited do lie within the bounds of plausibility suggested by current scientific understanding and available data. This can hold even for a narrow focus on carbon benefits alone over a relatively short time-period, with the inclusion of non-carbon and longer-term benefits reinforcing the case. However, the results are sensitive to assumptions and better data for, in particular, restoration costs associated with modest emission savings from lightly degraded sites would be helpful. Some other areas for further research are also identified.

Published in: Science of the Total Environment, 484, 114-120, 2014.

doi: 10.1016/j.scitotenv.2014.03.033


Enabling food security by verifying agricultural carbon. / H. Kahiluoto, P. Smith, D. Moran and J. E. Olesen.

Rewarding smallholders for sequestering carbon in agricultural land can improve food security whilemitigating climate change. Verification of carbon offsets in food-insecure regions is possible and achievable through rigorously controlled monitoring.

Published in: Nature Climate Change, Vol 4, 309-311, 2014.

doi:10.1038/nclimate2209


Higher temperature sensitivity for stable than for labile soil organic carbon - Evidence from incubations of long-term bare fallow soils

Lefèvre, R., P. Barré, F.E. Moyano, B.T. Christensen, G. Bardoux, T. Eglin, C. Girardin, S. Houot, T. Kätterer, F. v. Oort and C. Chenu

Abstract

In most mathematical models simulating SOC turnover and carbon exchange with the atmosphere, SOC is usually divided into pools to which are ascribed different mineralization rates that reflect different chemical qualities. The various rate constants are modified by soil temperature, reflecting that biological activity relates to temperature. Until now, a lack of consensus regarding the temperature sensitivity of SOC decay has refrained modelers from adopting different temperature modifying functions for SOC pools with different turnover rates. This incubation study compared the temperature sensitivity of SOC in soils from four differently sited, long-term bare fallow experiments. Soil was sampled at the start and after several decades of bare fallow, allowing us to quantify SOC temperature sensitivity in soils that differ only in their inherent content of labile organic matter. The results of the incubation implied that SOC with a slower turnover rate is more temperature sensitive than SOC with a faster turnover rate. The results our study and an earlier incubation study suggest that the relationship between SOC mineralization and temperature sensitivity is valid not only for different soils with SOC of different origin and contrasting lability but also for SOC with different lability within a given soil. Since compartmental models delineate pools of SOC with different lability for a given soil, a universal relationship between activation energy and SOC mineralization facilitates the incorporation of separate temperature sensitivities for different SOC pools. The consistency between our data and the earlier study strongly suggests that a consistent relationship exists between mean residence time and temperature sensitivity.

Published in: Global Change Biology, 20, 633-640, 2014.

doi: 10.1111/gcb.12402


Valuing water quality improvements from peatland restoration: Evidence and challenges / J. Martin Ortega, E. H. Allott, K. Glenk, M. Schaafsma

Abstract

There is evidence that damaged peatlands can negatively affect the delivery of water related ecosystem services. There is interest in peatland restoration to meet different regulatory targets, including the Water Framework Directive (WFD). A comprehensive assessment of the economic benefits of restoration is missing. This paper synthesises hydrological and bio-geochemical knowledge on peatland restoration, as well as insights in the monetary valuation of water quality improvements in freshwater systems. This is used to identify challenges in valuing water quality related benefits from peatland restoration. The paper concludes that there is strong evidence for rapid ecological responses to peatland restoration related to reduced suspended sediment loads, and sufficient evidence that re-wetting will prevent further decline in water quality. Two main challenges arise for valuation: (1) incomplete evidence of effects of restoration on final ecosystem services and benefits, and (2) the spatial and temporal differences in peatlands’ responses. We suggest developing valuation scenarios on a case-by-case basis, using best available evidence of the changes associated with restoration described by a categorization of peatland status similar to the ecological status ladders developed for the WFD. These would need to be tested with the public and should include an element of uncertainty in services provision.

Published in: Ecosystem Services (9), 34-43

doi: 10.1016/j.ecoser.2014.06.007


Temperatures and the growth and development of maize and rice: a review / B. Sánchez, A. Rasmussen, J.R. Porter

Abstract

Because of global land surface warming, extreme temperature events are expected to occur more often and more intensely, affecting the growth and development of the major cereal crops in several ways, thus affecting the production component of food security. In this study, we have identified rice and maize crop responses to temperature in different, but consistent, phenological phases and development stages. A literature review and data compilation of around 140 scientific articles have determined the key temperature thresholds and response to extreme temperature effects for rice and maize, complementing an earlier study on wheat. Lethal temperatures and cardinal temperatures, together with error estimates, have been identified for phenological phases and development stages. Following the methodology of previous work, we have collected and statistically analysed temperature thresholds of the three crops for the key physiological processes such as leaf initiation, shoot growth and root growth and for the most susceptible phenological phases such as sowing to emergence, anthesis and grain filling. Our summary shows that cardinal temperatures are conservative between studies and are seemingly well defined in all three crops. Anthesis and ripening are the most sensitive temperature stages in rice as well as in wheat and maize. We call for further experimental studies of the effects of transgressing threshold temperatures so such responses can be included into crop impact and adaptation models.

Published in: Global Change Biology (20) 2; 408-417

doi: 10.1111/gcb.12389


Managing Soil Organic Carbon: A Farm Perspective / Julie Ingram, Jane Mills, Ana Frelih-Larsen, McKenna Davis, Paulo Merante, Sian Ringrose, Andras Molnar, Berte Sánchez, Bhim Bahadur Ghaley, Zbigniew Karaczun

Abstract

Farming practices that lead to declining returns and inputs of carbon to soils pose a threat to key soil functions. The EU FP7 interdisciplinary project SmartSOIL is using scientific testing and modeling to identify management practices that can optimise soil carbon storage and crop productivity. A consultation with advisors and policymakers in six European case study regions seeks to identify barriers to, and incentives for, uptake of such practices. Results from preliminary interviews are reported. Overall advisor and farmer awareness of management practices specifically directed towards soil carbon is low. Most production-related decisions are taken in the short term, but managing soil carbon needs a long-term approach. Key barriers to uptake of practices include: perceived scientific uncertainty about the efficacy of practices; lack of real life ‘best practice’ examples to show farmers; difficulty in demonstrating the positive effects of soil carbon management practices and economic benefits over a long time scale; and advisors being unable to provide suitable advice due to inadequate information or training. Most farmers are unconvinced of the economic benefits of practices for managing soil carbon. Incentives are therefore needed, either as subsidies or as evidence of the cost effectiveness of practices. All new measures and advice should be integrated into existing programmes to avoid a fragmented policy approach.

Published in: EuroChoices (13) 2, 12-19

doi: 10.1111/1746-692X.12057


Ecosystem function and service quantification and valuation in a conventional winter wheat production system with DAISY model in Denmark / BB Ghaley, JR Porter

Abstract

With inevitable link between ecosystem function (EF), ecosystem services (ES) and agricultural productivity, there is a need for quantification and valuation of EF and ES in agro-ecosystems. Management practices have significant effects on soil organic matter (SOM), affecting productivity, EF and ES provision. The objective was to quantify two EF: soil water storage and nitrogen mineralization and three ES: food and fodder production and carbon sequestration, in a conventional winter wheat production system at 2.6% SOM compared to 50% lower (1.3%) and 50% higher (3.9%) SOM in Denmark by DAISY model. At 2.6% SOM, the food and fodder production was 6.49 and 6.86 t ha−1 year−1 respectively whereas carbon sequestration and soil water storage was 9.73 t ha−1 year−1 and 684 mm ha−1 year−1 respectively and nitrogen mineralisation was 83.58 kg ha−1 year−1. At 2.6% SOM, the two EF and three ES values were US$ 177 and US$ 2542 ha−1 year−1 respectively equivalent to US$ 96 and US$1370 million year−1 respectively in Denmark. The EF and ES quantities and values were positively correlated with SOM content. Hence, the quantification and valuation of EF and ES provides an empirical tool for optimising the EF and ES provision for agricultural productivity.

Published in: Ecosystem Services 10, 79-83

doi: 10.1016/j.ecoser.2014.09.010


Quantification and valuation of ecosystem services in diverse production systems for informed decision-making / Ghaley, BB; Vesterdal, L; Porter, JR 

Abstract

The empirical evidence of decline in ecosystem services (ES) over the last century has reinforced the call for ES quantification, monitoring and valuation. Usually, only provisioning ES are marketable and accounted for, whereas regulating, supporting and cultural ES are typically non-marketable and overlooked in connection with land-use or management decisions. The objective of this study was to quantify and value total ES (marketable and non-marketable) of diverse production systems and management intensities in Denmark to provide a basis for decisions based on economic values. The production systems were conventional wheat (Cwheat), a combined food and energy (CFE) production system and beech forest. Marketable (provisioning ES) and non-marketable ES (supporting, regulating and cultural) ES were quantified by dedicated on-site field measurements supplemented by literature data. The value of total ES was highest in CFE (US$ 3142 ha−1 yr−1) followed by Cwheat (US$ 2767 ha−1 yr−1) and beech forest (US$ 2328 ha−1 yr−1). As the production system shifted from Cwheat - CFE–beech, the marketable ES share decreased from 88% to 75% in CFE and 55% in beech whereas the non-marketable ES share increased to 12%, 25% and 45% of total ES in Cwheat, CFE and beech respectively, demonstrating production system and management effects on ES values. Total ES valuation, disintegrated into marketable and non-marketable share is a potential way forward to value ES and ‘tune’ our production systems for enhanced ES provision. Such monetary valuation can be used by policy makers and land managers as a tool to assess ES value and monitor the sustained flow of ES. The application of ES-based valuation for land management can enhance ES provision for maintaining the productive capacity of the land without depending on the external fossil-based fertilizer and chemical input.

Published in: Environmental Science & Policy (39); 139-149

doi: 10.1016/j.envsci.2013.08.004


Soil-based ecosystem services: A synthesis of nutrient cycling and carbon sequestration assessment methods / Ghaley, BB; Porter, JR; Sandhu, HS

Abstract

ve direct influence on the biogeochemical cycles and greenhouse gas emissions affecting provision of other ES that support human existence. We reviewed methods to assess the two key ES by identifying their strengths and weaknesses and have made suggestions for using appropriate methods for better understanding of the ecosystem functions for the provision of ES. Relevant papers for the review were chosen on the basis of (i) diversity of studies on the two key ES in different ecosystems, (ii) methodologies applied and (iii) detailed descriptions of the trial locations in terms of vegetation, soil type, location and climatic information. We concluded that (i) elemental stoichiometrical ratios could be a potential approach to assess the health of ecosystems in terms of provision of the two ES discussed, (ii) stoichiometric imbalances need to be avoided between the supply and the demand of the nutrients to maintain the ES provision in terrestrial ecosystems and (iii) stoichiometric ratios can act as a management tool at a field, farm and at landscape level, to complement other compositional biodiversity and functional diversity approaches to ensure sustainable provision of ES.

Published in: International Journal of Biodiversity Science, Ecosystem Services & Management (10) 3; 177-186

doi: 10.1080/21513732.2014.926990


Towards mitigation of greenhouse gases by small changes in farming practices: understanding local barriers in Spain / Sánchez B, Álvaro-Fuentes J, Cunningham R, Iglesias A.

Abstract

Small changes in agricultural practices have a large potential for reducing greenhouse gas emissions. However, the implementation of such practices at the local level is often limited by a range of barriers. Understanding the barriers is essential for defining effective measures, the actual mitigation potential of the measures, and the policy needs to ensure implementation. Here we evaluate behavioural, cultural, and policy barriers for implementation of mitigation practices at the local level that imply small changes to farmers. The choice of potential mitigation practices relevant to the case study is based on a literature review of previous empirical studies. Two methods that include the stakeholders’ involvement (experts and farmers) are undertaken for the prioritization of these potential practices: (a) Multi-criteria analysis (MCA) of the choices of an expert panel and (b) Analysis of barriers to implementation based on a survey of farmers. The MCA considers two future climate scenarios – current climate and a drier and warmer climate scenario. Results suggest that all potential selected practices are suitable for mitigation considering multiple criteria in both scenarios. Nevertheless, if all the barriers for implementation had the same influence, the preferred mitigation practices in the case study would be changes in fertilization management and use of cover crops. The identification of barriers for the implementation of the practices is based on the econometric analysis of surveys given to farmers. Results show that farmers’ environmental concerns, financial incentives and access to technical advice are the main factors that define their barriers to implementation. These results may contribute to develop effective mitigation policy to be included in the 2020 review of the European Union Common Agricultural Policy.

Published in: Mitigation and Adaptation Strategies for Global Change

doi: 10.1007/s11027-014-9562-7

Reviewed journals 2013

Sources of Nitrogen for Winter Wheat in Organic Cropping Systems

Petersen, S.O., Schjønning, P., Olesen, J.E., Christensen, S. & Christensen, B.T.

Abstract

Inputs of organic matter have a shorter-term direct and a longer-term indirect effect on the capacity of a soil to deliver plant-available N. During the initial decomposition phase, organic inputs increase microbial activity, which can be associated with net N mineralization or immobilization depending on the C/N ratio and other characteristics of the input. Subsequently, the N residing in residues of the initial decomposition phase adds to the main soil organic N pools, from where N is mineralized at a comparatively slow rate. The cumulative indirect effect of organic inputs thus reflects the duration of the specific management, while the direct effect depends on the quantity, as well as the quality, of recent inputs. To better synchronize soil N mineralization with crop demand, the relative importance of short- and long-term effects of organic inputs needs to be known in greater detail.

This study examined soil N stocks and pools of labile N in soil under winter wheat grown in three different organic cropping systems and one conventionally managed system without organic inputs as reference. Soil sampling took place in two successive years within the four experimental cropping systems at three (2007) and two (2008) sites with different soil types. We hypothesized that residue inputs from legumes and cover crops, and animal manure, would have similar long-term effects on N availability at all sites and that soil N availability and uptake by winter wheat would depend on the specific cropping system. It was found that inherent soil properties and past and current management all contributed to winter wheat N yields.

Published in: Soil Science Society of America Journal 77, 155-165, 2013.

doi: 10.2136/sssaj2012.0147


Carbon dynamics and retention in soil after anaerobic digestion of dairy cattle feed and faeces

Thomsen, I.K., Olesen, J.E., Møller, H.B., Sørensen, P. & Christensen, B.T.

Abstract

Adequate inputs of organic matter to the soil are vital for maintaining the fertility of arable soil and for retaining atmospheric CO2 in the soil organic matter pools. Arable land under intensive management tends to lose C and a systematic removal of manure and crop residues for energy purposes may enhance this negative trend. The return of the digested residues to arable land may alleviate prospected soil C losses, but the overall impact on soil C storage of using manure and crop residues for biogas production before land application remains unclear. The objective of this study was to compare the decomposition in soil of C added with primary plant biomass (feed) before and after being consumed by cattle, and before and after being subjected to anaerobic digestion for biogas production.

It was found that soil C sequestration is probably not influenced by the choice of energy utilization of the C held in the plant biomass. However, the exploitation of the easily decomposable C in the ruminants and/or in anaerobic biogas reactors most likely affects the short-term soil fertility as the microbial activity is reduced when substrates are deprived of the most labile fractions before being applied to soil.

Published in: Soil Biology & Biochemistry 58, 82-87, 2013

doi: 10.1016/j.soilbio.2012.11.006

Reviewed journals 2012

Clay Dispersibility and Soil Friability—Testing the Soil Clay-to-Carbon Saturation Concept

P. Schjønning *a, L.W. de Jongea, L.J. Munkholma, P. Moldrupb, B.T. Christensena and J.E. Olesena

Abstract

Soil organic carbon (OC) influences clay dispersibility, which affects soil tilth conditions and the risk of vertical migration of clay colloids. No universal lower threshold of OC has been identified for satisfactory stabilization of soil structure. We tested the concept of clay saturation with OC as a predictor of clay dispersibility and soil friability. Soil was sampled 3 yr in a field varying in clay content (∼100 to ∼220 g kg−1 soil) and grown with different crop rotations. Clay dispersibility was measured after end-over-end shaking of field-moist soil and 1- to 2-mm sized aggregates either air-dried or rewetted to −100 hPa matric potential. Tensile strength of 1- to 2-, 2- to 4-, 4- to 8-, and 8- to 16-mm air-dried aggregates was calculated from their compressive strength, and soil friability estimated from the strength–volume relation. Crop rotation characteristics gave only minor effects on clay dispersibility and no detectable effects on soil friability. Dispersed clay correlated to soil content of clay, but the correlation increased if subtracting a fraction assumed protected by OC. This trend was less convincing for soil tensile strength and friability. Increased clay dispersibility and reduced soil friability for 1 yr of measurements could be ascribed to wet conditions for potato (Solanum tuberosum L.) harvest and tillage the preceding year. Literature data indicate soils’ content of clay and silt (Fines20) to be a better predictor of specific surface area than clay. We conclude that a clay/OC ratio of 10 and a Fines20/OC ratio of 20 may serve as corresponding thresholds for clay dispersibility, the latter probably best reflecting organo-mineral interactions of importance to the soil physical properties.

Published in: Vadose Zone Journal, Vol. 11 No. 1, 2012,

doi: 10.2136/vzj2011.0067


Soils and climate change

Pete Smith

Abstract

Soils contain vast reserves (~1500 Pg C) of carbon, about twice that found as carbon dioxide in the atmosphere. Historically, soils in managed ecosystems have lost a portion of this carbon (40–90 Pg C) through land use change, some of which has remained in the atmosphere. In terms of climate change, most projections suggest that soils carbon changes driven by future climate change will range from small losses to moderate gains, but these global trends show considerable regional variation. The response of soil C in future will be determined by a delicate balance between the impacts of increased temperature and decreased soil moisture on decomposition rates, and the balance between changes in C losses from decomposition and C gains through increased productivity. In terms of using soils to mitigate climate change, soil C sequestration globally has a large, cost-competitive mitigation potential. Nevertheless, limitations of soil C sequestration include time-limitation, non-permanence, displacement and difficulties in verification. Despite these limitations, soil C sequestration can be useful to meet short-term to medium-term targets, and confers a number of co-benefits on soils, making it a viable option for reducing the short term atmospheric CO2 concentration, thus buying time to develop longer term emission reduction solutions across all sectors of the economy.

Published in: Current Opinion in Environmental Sustainability, 2012, 4:1–6,

doi: 10.1016/j.cosust.2012.06.005

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Revised 17.11.2016