The invention relates to the technical field of slow-release organic fertilizers, and particularly discloses a preparation method of a slow-release organic chelated iron
fertilizer. Comprising the following steps: 1, completely dissolving a
titanium dioxide byproduct
ferrous sulfate heptahydrate in pure water in an
inert atmosphere, adding
iron powder, and filtering to obtain a
ferrous salt solution; 2, under the stirring condition, lignosulfonate is added into pure water to be completely dissolved, and an organic
salt solution is prepared; step 3, adding the ferrite solution obtained in the step 1 into an organic
salt solution in an
inert atmosphere to obtain a pre-complexation solution; step 4, dropwise adding dilute alkali liquor into the pre-complexing solution under stirring to adjust the pH value, and keeping stirring for 20-30 minutes to obtain a
ferrous lignosulfonate solution; and step 5, putting the carrier with the adsorption gaps and the cavity inside into a ferrous lignosulfonate solution, vacuumizing to fully infiltrate the inside of the carrier, taking out, filtering, and
drying to obtain the slow-release organic chelated iron
fertilizer. The technology fills the technical blank that chelated iron
fertilizer prepared in the prior art can only be sprayed and is not suitable for being used as base fertilizer.