Soil fertility, evolving concepts and assessments

Many authors have discussed the concept of soil fertility. Despite some disagreement on the exact terminology, soil fertility retrospectively appeared to focus generally on the use of soil for agriculture. It was defined some 150 years ago, while agricultural sciences mostly focused on soil physical and chemical properties. More recently, with the increasing awareness of environmental issues related to agricultural land use and the development of new knowledge on ecosystems, more comprehensive approaches to soil quality were developed. Since the 1980s, growing knowledge on the roles of soil organic matter and living organisms has emphasised the importance of understanding and assessing the biological components of the soil and their functions alongside the physical and chemical components. Soil is described as a living system that fulfils several functions, such as primary production, environmental filter and climate regulation. Following the metaphor of a complex living 'organism', the term 'soil health' is thus used by some authors instead of soil quality. Soil quality is hence defined as the soil fitness for use, which cannot be measured directly. It must be assessed in a sensitive and holistic way that accounts for both inherent properties and dynamic responses to management and resistance to environmental stress. Several sets of indicators and more integrated methods have been developed. However, further research is still needed to consolidate assessment guidelines that would help to model better the impact of agricultural practices on soil quality and to define strategies for a sustainable management of soil quality. (Résumé d'auteur