The subject matter of the invention is a substituted hydroxyapatite carrier, responding to the formula: Ca(10-x)Mx(PO4)(6-y)(CO3)y(OH)2 in which: M is chosen from Cu, Mg, Zn, Pb, Cd, Ba, K, Mn, Mo, Fe, Ag, B, Se or a combination of at least two of such elements; —x is comprised between 0 and 2, preferably between 0 and 1, more preferably between 0 and 0.8, even more preferably between 0.02 and 0.05; —y is comprised between 0 and 2, preferably between 0 and 1, more preferably between 0.002 and 0.030, with the proviso that x and y are never equal to 0 at the same time. The substituted hydroxyapatite is a carrier of a bioactive substance chosen among a metal ion selected from Mn, Mg, K, Fe, B, Mo, Se and/or an extract of vegetal origin. The invention relates also to the use of the carrier for the delivery of such a bioactive substance to plants in order to achieve the phytosanitary and/or nutritional treatment of the plant.
