|Main authors:||Else K. Bünemann, Giulia Bongiorno, Zhanguo Bai, Rachel E. Creamer, Gerlinde De Deyn, Ron de Goede, Luuk Fleskens, Violette Geissen, Thom W. Kuyper, Paul Mäder, Mirjam Pulleman, Wijnand Sukkel, Jan Willem van Groenigen and Lijbert Brussaard|
|Source document:||Bünemann, E. K. et al. (2018) Soil quality - A critical review. Soil Biology and Biochemistry, Volume 120, May 2018, pp 105-125
Various requirements for soil quality indicators have been identified in some (but by far not all) approaches to assessing soil quality (Table 3). All publications that list such requirements mention at least one conceptual condition such as that a chosen indicator must be related to a given soil threat, function or ecosystem service and be relevant. However, this is not of great use if soil quality assessment is not targeting a specific soil threat, function or ecosystem service.
Table 3: Considerations and criteria for soil quality indicators mentioned in various publications.
|Criteria and consideration||Larson and Pierce (1994)||Doran and Parkin (1996)||Macdonald et al. (1998)||Burger & Kelting (1999)1||Southorn and Cattle (2000)||Nortcliff (2002)||Merrington (2006)||Idowu et al. (2008)||Ritz et al. (2009)||West et al. (2010)||Oberholzer et al. (2012)||Bone et al. (2014)|
|Related to soil function and/or ecosystem processes||X||X||X||X||X||X||X||X|
|Relevance, representation of key variables controlling soil quality, correlated to long-term response, allow evaluation of assessment criteria||X||X||X||X||X|
|Significance at the appropriate scale||X||X|
|Integrate soil physical, chemical, biological properties||X||X|
|Allow estimation of soil properties or functions which are more difficult to measure directly||X||X|
|Ease of sampling and measurement (simplicity, practicality, single or repeated sampling and measurement, provide information in short timeframe)||X||X||X||X||X||X||X||X||X||X||X|
|High throughput of analysis, wide applicability||X||X|
|Amount of soil needed||X|
|Sample storage before analysis||X|
|Reliability and reproducibility of measurement||X||X||X||X||X||X||X|
|Existence of a standard method of estimation (standard operating procedure)||X||X|
|Availability of reference material for quality control||X|
|Cost (sampling, hardware, analysis, labour)||X||X||X||X||X||X||X||X|
|Temporal variation (not influenced by short-term weather patterns)||X||X||X||X|
|Sensitivity to changes in management, or land use, response to perturbation as well as corrective measures||X||X||X||X||X||X||X||X||X||X|
|Comparability with routine sampling and monitoring programs (context data available); part of standard tests; baseline available||X||X||X||X||X||X||X|
|Ease of interpretation, interpretation criteria available||X||X||X||X||X||X|
|Archivability, capable of continuous assessmeNT||X||X|
|Mappable trend indicators||X|
|Generic or diagnostic value||X||X|
1 as cited in Bone et al. (2010)
Of the practical requirements, ease of sampling and measurement is almost always mentioned, and reliability and cost are also considered important. Practical considerations such as the disadvantage of indicators requiring undisturbed samples often play an important role in discarding otherwise suitable soil quality indicators (Idowu et al., 2008), which is a serious limitation from a scientific perspective. Where the measurement of a specific soil indicator is considered too expensive, too difficult or not possible (e.g. bulk density, due to the stoniness of the soil), pedotransfer functions may provide a proxy value through the measurement of other properties, for example carbon and texture for bulk density (Reidy et al., 2016). The application of pedotransfer functions was already considered useful in early soil quality publications (Doran and Parkin, 1996; Doran and Safley, 1997; Larson and Pierce, 1994) and has again been advocated more recently (Bone et al., 2010), especially for complex soil properties such as hydrologic characteristics (Saxton and Rawls, 2006; Toth et al., 2015). However, the inaccuracy of pedotransfer functions needs to be clearly stated.
Sensitivity to changes in management is mentioned frequently (Table 3), but there may be trade-offs with robustness to seasonal variation. Regarding the interpretation of the obtained values, comparability to data from other sampling campaigns is often desired. However, some indicators such as organic carbon (or soil organic matter) content and pH are often measured, whereas others such as bulk density or earthworm diversity are rarely assessed (Morvan et al., 2008). Moreover, the requirement to have clear (absolute) interpretation schemes for a given indicator is mentioned in only half of the publications (Table 3), even though assessment of soil quality cannot be put into practice without it.
Finally, indications to what extent soil quality indicators actually fulfill the requirements listed in Table 3 are often missing but would be needed to make informed choices in soil quality assessment programs.
Note: For full references to papers quoted in this article see