A note on the Hybrid Soil Moisture Deficit Model v2.0

Abstract

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 protection for a sustainable future: options for a soil monitoring network for Ireland

“…Soil Subgroups relate to soil management of the top 40 cm and can be categorized into simplified diagnostic categories based on soil drainage status, soil organic carbon, etc (Creamer et al ., ; Simo et al ., ). As soil moisture is considered a key driver of soil quality in Ireland, it has been presented as a relevant classifier for Irish soils (Schulte et al ., ). This paper recognizes that soil drainage status is most relevant to N.W.…”

“…Figure shows the main drainage classes as described by Schulte et al . () based upon the 3rd Edition National Soils Map by Creamer et al . ().…”

“…The stratified approach used a combination of shapefile overlays that utilized soil drainage categories (Schulte et al ., ) and land use data (O'Sullivan et al ., ). We applied a stratified selection based upon a published review of the main drivers that govern soil quality in Ireland: drainage class and land use class.…”

Application of Dexter’s soil physical quality index: an Irish case study

“…For Irish soils, Simo et al (2014) and Schulte et al (2015) have established indicative soil drainage classes using diagnostic features identified as part of the Irish soil classification. Poorly draining soils were defined as those showing mottling within 40 cm of the surface.…”

“…Such heterogeneity influences paddock management decisions directly (Humphreys et al, 2008;Huebsch et al, 2013). Soil quality (Wilson and Maliszewska-Kordybach, 2000) is concerned with physical (the focus of the current study), chemical and biological aspects of soil across soilscapes and, therefore, defines the capacity of agricultural soil to deliver multiple functions, such as primary productivity, nutrient cycling, water filtration (Fenton et al, 2011;Jahangir et al, 2013), habitat for biodiversity and carbon sequestration (Karlen et al, 1997;Wiebe 2003;Schulte et al, 2015). This capacity can be overextended, resulting in degradation of the system by compaction (Soane and van Ouwerkerk, 1998;Robertson, 2007) or impedance of other soil functions (Creamer et al, 2010).…”