Abstract: The present invention relates to a fertilizing composition comprising a glass matrix, wherein said glass matrix comprises: at least three forming oxides, wherein said at least three forming oxides are SiO2, P2O5 and B2O3, and have a ratio by weight between SiO2/P2O5 comprised from 1 to 5 and a ratio by weight between SiO2/B2O3 comprised from 5 to 25;—at least one microelement; said fertilizing composition optionally also comprising citric acid and/or at least one humic substance. The subject matter of the present invention further relates to an aggregate comprising said fertilizing composition, at least one thickening agent and optionally at least one further microelement that is identical to or different from the at least one microelement present within the glass matrix of the fertilizing composition. The present invention also relates to a method for fertilizing herbaceous and/or arboreal crops which comprises administering said composition or said aggregate to the crops.