Abstract: Described herein is a complex between humic substances and iron denominated "iron humate" characterized in that it has a structure of the type: ##STR1## where the metal is protected from the pyrophosphate and from the humic substances (SU), obtained through a method comprising the following phases:a) dosage of the humic extractsb) purification of said humic extracts through centrifuging or filter pressing to eliminate any suspended particlesc) transfer of the floating product into a mixerd) preparation of a solution of K.sub.4 P.sub.2 O.sub.7 10H.sub.2 Oe) mixing solution d) with an aqueous solution of FeSO.sub.4 7H.sub.2 O containing a minimum quantity of H.sub.2 SO.sub.4 operating slowly and keeping the humic extract under vigorous agitationf) after agitation for a few minutes, rapid drying at 60-90.degree. C.