Abstract: The present invention relates to a composition intended for culture substrates and/or culture solutions comprising the combination of—(a) at least one clay, siliceous or clay-siliceous mineral compound and—(b) at least one carbon compound comprising at least 5% by mass of total carbon and/or at least 1% by mass of organic carbon relative to the total mass of the carbon compound, said combination being obtainable by heat treating, in the presence of water, the mixture of compounds (a) and (b). It also relates to the method of manufacturing and using same as well as a fertilizer or soil conditioner comprising same and the use thereof.

Abstract: The invention relates to a method for preparing a fertilizing composition, comprising a step of treating a liquid composition having humic substances the weight-average hydrodynamic radius of the particles in solution of which, measured by dynamic light scattering (DLS), is the “Hraverage pre-treatment” with an appropriate amount of oxidizing agent to obtain a liquid composition having oxidized humic substances the weight-average hydrodynamic radius of the particles in solution (Hraverage post-treatment) of which, measured by DLS, is greater than the Hraverage pre-treatment; a composition that can be obtained by the method and the use thereof.