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The Hybrid Soil Moisture Deficit (HSMD) model has been used for a wide range of applications, including modelling of grassland productivity and utilisation, assessment of agricultural management opportunities such as slurry spreading, predicting nutrient emissions to the environment and risks of pathogen transfer to water. In the decade since its publication, various ad hoc modifications have been developed and the recent publication of the Irish Soil Information System has facilitated improved assessment of the spatial soil moisture dynamics. In this short note, we formally present a new version of the model (HSMD2.0), which includes two new soil drainage classes, as well as an optional module to account for the topographic wetness index at any location. In addition, we present a new Indicative Soil Drainage Map for Ireland, based on the Irish Soil Classification system, developed as part of the Irish Soil Information System. Keywords Areas of natural constraint • drainage • model • soil moisture • trafficability IntroductionIn temperate maritime climates, soil moisture dynamics are drivers of the evolution of agricultural systems. The number of days when soil has excess moisture, known as field capacity (FC) days, determines the type of agricultural system used, with specific influence on herbage growth, herbage utilisation, farm operations and environmental sustainability (Schulte et al., 2012). The European Commission now recognises FC days as a bio-physical criterion that defines a natural constraint for agriculture in Europe (Jones et al., 2013). FC days can be either measured in situ at the field/soil profile scale or modelled as a function of the temporal pattern of soil moisture deficit (SMD), which in turn can be computed from meteorological variables and soil properties. Schulte et al. (2005) combined existing Teagasc and MetÉireann SMD models into the 'hybrid soil moisture deficit' or HSMD model, which is a simple mass-balance calculation to predict SMD from precipitation, evapotranspiration and drainage. Precipitation and evapotranspiration were taken and computed, respectively, from observed weather data or numerical weather prediction (NWP) model output using the Penman-Monteith equation (Allen et al., 1998) and drainage was modelled as a function of one of the three drainage classes calibrated using empirical experimental data. These calibrations showed that poorly drained soils are those that remain wetter than FC for multiple days following winter rainfall events, moderately drained soils carry water in excess of FC during winter rainfall events, but return to FC on the first dry day, whilst well-drained soils never carry soil water in excess of FC. This calibration of drainage is described in detail by Schulte et al. (2005). In recent evaluations of the HSDM model to test its suitability for operational deployment, demonstrated strong relationships between HSMD output and field observations of topsoil (to 30 cm depth) volumetric water content, whilst Doody et al. (2010) concluded that...

Soil plays a key role in the global carbon (C) cycle. Most current assessments of SOC stocks and the guidelines given by Intergovernmental Panel on Climate Change (IPCC) focus on the top 30 cm of soil. Our research shows that, when considering only total quantities, most of the SOC stocks are found in this top layer. However, not all forms of SOC are equally valuable as long-term stable stores of carbon: the majority of SOC is available for mineralisation and can potentially be re-emitted to the atmosphere. SOC associated with micro-aggregates and silt plus clay fractions is more stable and therefore represents a long-term carbon store. Our research shows that most of this stable carbon is located at depths below 30 cm (42% of subsoil SOC is located in microaggregates and silt and clay, compared to 16% in the topsoil), specifically in soils that are subject to clay illuviation. This has implications for land management decisions in temperate grassland regions, defining the trade-offs between primary productivity and C emissions in clay-illuviated soils, as a result of drainage. Therefore, climate smart land management should consider the balance between SOC stabilisation in topsoils for productivity versus sequestration in subsoils for climate mitigation.

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The upper reaches of the Segre river, flowing through the Pyrenees, offers a variety of geomorphic surfaces that allow us to study soil chronosequences. The objective of this work is to widen the knowledge about the main characteristics and formation processes of some benchmark soils developed on fluvio-glacial, alluvial-fan and terrace materials of Pleistocene and Holocene age related to the Segre river, either siliceous or carbonatic. This knowledge will allow us to identify soil forming processes, commonly found in Mediterranean environments such as carbonate redistribution, clay formation and mobilization and rubefaction, all as functions of parent material and age. Five profiles, ranging from the Lower Pleistocene to the Holocene were classified according to Soil Taxonomy/WRB. The Montferrer profile (Calcic Palexeralf /Calcic Cutanic Luvisol (Chromic) is a deep, partly decarbonated soil, with calcium carbonate accumulation in depth covering glacial features. The Torre del Remei profile (Typic Paleustalf /Cutanic Luvisol) developed on silicic moraines and shows an extreme clay formation and illuviation. The Alp (Typic Haplustalf /Cutanic Luvisol) and Tartera (Petric Calciustept /Petric Calcisol) soils are developed on alluvial fans with calcium carbonate sources. The former is partly decarbonated, whilst the latter is rubefacted on top and shows speleothem-like carbonate pendants with superposition of clay illuviation. The youngest profile, Abellerols, (Typic Calciustept /Typic Calcisol) shows only a partial decarbonation and calcite accumulation at depth. The results show that soil development is determined by the age of the surface and the source of calcite, either in the parent rock or brought by subsurface flow: clay illuviation is extreme in absence of it. Special morphologies of carbonate pendants are indicators of environmental conditions. The coexistence of clay coatings and secondary calcite can be explained by recarbonatation or by spatial differentiation of soil environments in the profile. One of the implications of this research is the inconsistence of using soil development indices based on morphological indicators when soils are formed on different parent materials and are subjected to different geomorphic dynamics.