Comparison of Soil Physical Quality Indicators Using Direct and Indirect Data Inputs Derived from a Combination of In‐Situ and Ex‐Situ Methods

Abstract

Core Ideas Soil quality indicators such as S and PAWC are considered as static indicators with low sensitivity. The soil quality indicator AWr is considered a dynamic indicator with high sensitivity. Indirect pedotransfer function based SWRCs are appropriate for static baseline indicators. Soil monitoring programs should use AWr as a sensitive and reliable soil quality indicator. The quality of a soil is its ability to deliver functions providing ecosystem services, human health and well‐being. Soil physical quality (SPQ) values use different parts of the soil water retention curve (SWRC) to calculate SPQ. For example, the plant available water capacity (PAWC) method is the difference in water content between permanent wilting point and field capacity. The S‐index uses the slope of the SWRC at its inflection point and the relative air‐water energy (AWr) is the integral of “dry” divided by the “wet” area of the SWRC. Increasing demand for soil monitoring policies calls for reliable and sensitive soil quality indicators (SQIs). The objectives of the study were to assess the sensitivity and applicability of SPQ indicators using direct and indirect data inputs. The indirect approach provided sufficient data complexity for the PAWC and S‐index values, but the more complex AWr required the direct approach. PAWC and S‐index values were identified as static SPQ indicators. The values obtained from these approaches should be used to form baseline static datasets and therefore have an indicative role only. The AWr value was identified as a dynamic SPQ indicator and provided required sensitivity to pick up temporal changes in SPQ. This indicator could be used at multiple scales and could even guide grassland management in terms of SPQ. Higher SWRC data resolution will require more complex hydraulic models to fit and will ultimately improve the accuracy of soil hydraulic data and improve the sensitivity of AWr as a SPQ indicator.

Contrasting physical controls on phosphorus transport to shallow groundwater at the hillslope scale

“…The undisturbed cores were transferred to the laboratory for the continuous hydraulic measurement of a SWRC in terms of volumetric water content θ v using an evaporation method. The Hyprop apparatus (UMS GmbH, Munich, Germany) (Bezerra-Coelho et al, 2018) was used for this purpose and a detailed procedure has been described in Bacher et al (2019). In summary, the raw Hyprop data from the direct SWRC approach were then fitted to the bimodal van Genuchten model of Durner (Durner, 1994) with the Mualem-constraint (Mualem, 1976) to obtain the hydraulic parameters needed for the modelling phase.…”

“…Combined field and laboratory techniques have used undisturbed (Bacher et al, 2019) or disturbed (Pang et al, 2016) soil, subsoil and bedrock that develop datasets to run model scenarios that best explain the transport of P to GW (Schoumans and Groenendijk, 2000;Schoumans et al, 2009). Different levels of data complexity (from simple to complex) affect transport model outcomes and it is therefore preferable where possible to collect undisturbed soil cores and develop soil physical and hydraulic parameters (Bünemann et al, 2018).…”

Detection of physical hazards in soil profiles using quantitative soil physical quality assessment in the Pannonian basin, Eastern Austria

“…Cumulated PAWC (mm) the study site, the broad validity of the thresholds given in literature have been questioned sporadically (Bacher et al, 2019;Castellini et al, 2019). Nevertheless, the extent and uniformity of the threshold excess in BD, RFC, and partly saturated hydraulic conductivity (K s ) endorsed the assessment of a critical SPQ state for the studied soils.…”

Effects of innovative long-term soil and crop management on topsoil properties of a Mediterranean soil based on detailed water retention curves

“…The S value for the two study treatments reflected good soil physical quality (0.035 < S ≤ 0.050) for the van Genuchten equation (Table 2) and very good (≥ 0.050) for the sigmoidal equation (Table 3) (Bacher et al, 2019;Dexter, 2004b;Reynolds et al, 2009).…”