As a prerequisite to establish trace metal phytoavailability, it is essential to determine trace metal speciation in the solution of the rhizosphere, where substantial alterations of physicalchemical properties (e.g. pH, Eh, organic matters) are induced by root activities. Investigations in the past decades were mainly dedicated to studying illustrative cases of how each individual rhizosphere process is able to influence trace metal speciation in solution. On a more integrative perspective, the present study aimed at investigating (i) the diversity of chemical modifications occurring in the solution of the rhizosphere of crop species cultivated on soils exhibiting a very wide range of physical-chemical properties and (ii) their consequent impact on copper (Cu) speciation in solution. Three plant species from three distinct botanical families, i.e. one graminaceous species, red fescue (Festuca rubra), two dicotyledonous species, tomato (Lycopersicon esculentum) and cabbage (Brassica oleracea), and 55 soils exhibiting a wide variety of physico-chemical properties (e.g. pH 4.4-8.2, 1-126 g Corg kg-1 , 6-1077 mg Cutotal kg-1 ) were selected for this study. Plants were grown using the RHIZOtest experimental design. This biotest consists in growing plants for two weeks in hydroponics, then for 8 days in contact with soil. Soils harvested from planted and unplanted devices are considered to be representative of rhizosphere and bulk soil, respectively. The solution of each rhizosphere and bulk soil was extracted with an unbuffered salt solution, and pH, concentrations of major ions and trace elements, dissolved organic matter (DOM), as well as the free Cu2+ activity were measured. The reactivity of DOM towards Cu was also estimated by modeling of Cu speciation, using the Humic Ion-Binding Model VII. Root activities induced variation in pH and in DOM concentration and its reactivity, thereby inducing substantial alterations of Cu speciation in solution. Fescue induced an ov