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International audience; Within the United Nations Framework Convention on Climate Change, articles 3.3 and 3.4 stipulate that some voluntary activities leading to an additional carbon (C) sequestration in soils could be accounted as C sinks in national greenhouse gas inventories. These additional C stocks should be verifiable. In this work, we assess the feasibility of verifying the effects of changes in land use or management practice on soil organic carbon (SOC), by comparing minimum detectable changes in SOC concentration for existing European networks suitable for soil monitoring. Among the tested scenarios, the minimum detectable changes differed considerably among the soil-monitoring networks (SMNs). Considerable effort would be necessary for some member states to reach acceptable levels of minimum detectable change for C sequestration accounting. For SOC, a time interval of about 10 years would enable the detection of some simulated large changes in most European countries. In almost all cases, the minimum detectable change in SOC stocks remains greater than annual greenhouse gases emissions. Therefore, it is unlikely that SMNs could be used for annual national C accounting. However, the importance of organic C in soil functions, and as an indicator of soil condition and trends, underlines the importance of establishing effective national SMNs.

Background Publication of the First Soil Action Plan for England in 2004 has drawn attention to the value that can be derived from the protection and appropriate management of the country’s soil resources. This principle applies all soils equally including those in built environments which are the subject of this report. Soil is valuable because it underpins both quality of life and biodiversity conservation. It does this by providing a range of services or functions which meet human needs and sustain natural systems. The principal of these are environmental regulation and environmental maintenance, food and fibre production, above and below ground habitat maintenance as support for biodiversity, protection of cultural services and provision of a platform for the built environment. Soil is, in practical terms, a non-renewable resource which can be destroyed by construction. To help protect soils in the built environment, the services they can and do provide to both society and the environment need to be documented and explained. This report proposes a framework to help explain soil’s services and functions within built environments and provides a literature-based review of those services, their current perceived value, and a risk assessment of the threats that may degrade them.

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Agriculture in Ireland is the main source of ammonia (NH3) and contributes 30% of greenhouse gas emissions (GHG), with the majority of these emissions associated with livestock production. As a result, strategies promoting reductions in NH3 and GHG emissions are required. The aim of this work was: (i) to assess the impact of various NH3 abatement techniques on GHG release from a grassland soil; (ii) to investigate the consequences of organic nitrogen (N) applications in terms of carbon (C) sequestration in soils. The effects of slurry dry-matter content, application technique and timing of application were studied in a fifteen month field-plot experiment where gaseous emissions (CO2, N2O, CH4 and NH3) post-application were monitored. The natural abundance 13C tracer technique was also used to investigate the short-term dynamic of slurry-derived C and its consequences on soil CO2 efflux. Finally, 15N labelled slurries, supplemented or not with an additional C substrate, were used in a lysimeter study, under controlled conditions, to characterise the interactions between soil C and N processes post-organic fertilisation. Trailing-shoe application technique was shown to be and efficient way to lower NH3 volatilisation from land spread slurry. However, such benefice could be easily offset by an increase in direct N2O emissions and ecosystem respiration. Conversely, adjusting the timing of slurry spreading to get favourable soil and weather conditions, and to better meet herbage N requirements, had a positive effect on field N balance through a simultaneous reduction of both NH3 and N2O emissions. Emission factors (EF) calculated for slurry-induced N2O emissions were significantly lower than those calculated for mineral fertiliser and were greatly affected by weather and soil conditions. Such results support the widely spread idea of an inappropriate use of a single default EF value of 1% for both fertiliser types, under the IPCC Tier 1 methodology for national GHG inventories, and calls for the development of region-specific emission factors based on local soil types and climatic conditions.About 60% of slurry-derived C was shown to remain in the soil, even after 6 months, thus contributing to an increase of SOC pools. However, such incorporation of slurry-derived C may be offset by a positive priming effect of slurry on the degradation of the SOM. Such short-term priming of soil CO2 efflux may be, under certain conditions, compensated by a subsequent negative PE, thus minimising the impact of such phenomenon on the long-term sequestration of added slurry C. The long-term impact of these priming effects on nutrient and GHG balances remains to be further investigated, as these phenomena may occur on a regular basis in grassland ecosystems.

Soil organic carbon (SOC) is increasingly recognised as an important component in the global carbon cycle and as a potential C sequestration pool for mitigation of the enhanced greenhouse effect. Recent appeals have prompted research into the potential of storing C in arable fields and the concomitant impact for on-farm economics. This project was instigated to answer the question “Does soil organic matter (SOM), or its management, provide arable on-farm benefit, in England and Wales?”. A methodological design was developed which integrates social science with soil science. From the National Soil inventory (NSI) database, attainable SOC ranges were estimated for different SOC physiotopes, i.e. landscape units for which the environmental factors governing SOC contents are similar. Significant differences were found, e.g for a dry-sandy physiotope and a wet-clayey physiotope, the ranges were estimated at 0.5-1.6% and 2.0-5.4% SOC (w/w), respectively. A list of qualified ‘SOM benefit’ indicators was developed using an iterative process involving the scientific literature and interviews with ‘expert farmers’. Perceptions of the indicators were investigated within a stratified random sample of commercial farmers. On balance, farmers perceived that benefits of SOM outweighed the disbenefits (i.e. lodging, weeds, and slugs). N fertiliser reduction, increased yield quantity, and enhanced ease of tillage were recognised as the most valuable benefits. However, the values were low to moderate, and perceived to be influenced substantially by physiotope, crop type, and SOM management type. Farmers’ perceptions and valuations were investigated for 101 fields on commercial farms, selected from the NSI database to represent the attainable SOC content ranges. No correlations were found between SOC and any performance indicator. The full range of reported performances was found for fields with similar SOC contents. This implied that SOC contents and SOM management may have little importance to on-farm economics when compared to the quality of overall farm management. These results expose the marginal extent of on-farm benefits from increased SOC contents and SOM management. Implications for future research and policy are discussed.