Soil Quality: A Critical Review

From plot to national scales, sampling, analysis, and visual inspection of soil are common methods used to evaluate its condition and potential for use. However, due to the complexity and site-specificity of soils, the legacy impacts of past land use, and trade-offs across ecosystem services, selecting relevant soil parameters and interpreting measurements are not simple tasks. Here, we go over the definition, methods of assessment, and choices and interpretations of indicators for soil quality and related concepts. Assessing soil condition and potential usage involves a range of methods, from small-scale sampling to nationwide analyses. Despite their prevalence, these approaches face challenges due to the intricate nature of soils, their site-specific characteristics, historical land use impacts, and the need to balance various ecosystem services. Selecting pertinent soil parameters and interpreting measurements becomes a complex task. In this context, we delve into the definition, assessment methods, and the choices and interpretations of indicators related to soil quality. Our focus is on widely used indicators within agricultural land use. Notably, explicit evaluations of soil quality for specific risks, functions, and ecosystem services remain limited. Furthermore, there is a scarcity of systems providing clear frameworks for interpreting measured indicator values, hampering their acceptance by both policymakers and land managers. We explore innovative indicators that shed light on often overlooked soil properties and processes. Biological/biochemical indicators are under-represented but show great potential. Soil quality assessment should specify targeted soil threats, functions and ecosystem services. Increasingly interactive assessment tools must be developed with target users.