Invisible drivers of fertility: soil microorganisms as sustainers of primary productions

Sustainable development has been defined as a development that meets the needs of the present without compromising the ability of future generations to meet their needs. Agricultural sustainability must take into account the quality and functionality of soils, and proper indicators to assess and monitor this quality must be developed. This chapter focuses on the roles played by microorganisms in soils, and how these roles are fundamental to sustain all primary productions in soils. General definitions of diversity and activity of microorganisms in soils are given, together with a glance of the challenges soil microbiologists must face in order to study one of the most complex biological environments on Earth. Examples are also given of practical applications of advanced techniques in monitoring the impact of human interventions on the sustainability of agricultural practices in terms of possible impacts on soil microorganisms