A method for preparing ductile cast iron, comprising the steps of: a) melting a base iron to obtain a molten iron, the base iron having a carbon content from 3.00 wt. % to 4.00 wt. %, a silicon content from 1.50 wt.% to 4.5 wt. % and a sulphur content less than or equal to 0.025 wt. %, wherein the wt.% is based on the total weight of base iron; b) treating the molten iron with a nodulazing composition comprising a source of magnesium and, optionally, a source of rare earth elements to obtain a nodulized molten iron; c) introducing the nodulized molten iron into a pouring unit, wherein the pouring unit comprises an inlet channel, a pressurized pouring vessel, a pouring basin, a stopper/nozzle mechanism, and, optionally, a heating inductor; wherein the nodulized molten iron is introduced into the pouring unit through the inlet channel into the pressurized pouring vessel; d) holding the molten iron in the pressurized pouring vessel resulting in a molten iron having a sulphur content from 0.002 wt. % to 0.006 wt. %; e) pushing the molten iron from the pressurized pouring vessel to the pouring basin; f) pouring a stream of the molten iron from the pouring basin into a mould through the stopper/nozzle mechanism; and g) allowing the molten iron to solidify in said mould; wherein the molten iron is treated, after step d) and prior to step g), either simultaneously with an additive composition and with an inoculating composition, or sequentially, either first with the additive composition, and subsequently with the inoculating composition, or vice versa; wherein the additive composition comprises a source of sulphur, a source of selenium and, optionally, a source of tellurium and/or a source of rare earth elements, and comprises a carrier selected from ferrosilicon, iron powder, and iron oxide; and wherein the additive composition comprises from 2 wt. % to 60 wt. % of sulphur based on the total weight of the additive composition, and from 0.5 wt. % to 20 wt. % of selenium based on the total weight of the additive composition; and wherein the total content of sulphur, selenium, and optionally, tellurium and/or rare earth elements, in the resulting molten iron is increased by a total amount from 0.002 to 0.012 wt.% respect to the weight of the molten iron. a) melting a base iron to obtain a molten iron, the base iron having a carbon content from 3.00 wt. % to 4.00 wt. %, a silicon content from 1.50 wt.% to 4.5 wt. % and a sulphur content less than or equal to 0.025 wt. %, wherein the wt.% is based on the total weight of base iron; b) treating the molten iron with a nodulazing composition comprising a source of magnesium and, optionally, a source of rare earth elements to obtain a nodulized molten iron; c) introducing the nodulized molten iron into a pouring unit, wherein the pouring unit comprises an inlet channel, a pressurized pouring vessel, a pouring basin, a stopper/nozzle mechanism, and, optionally, a heating inductor; wherein the nodulized molten iron is introduced into the pouring unit through the inlet channel into the pressurized pouring vessel; d) holding the molten iron in the pressurized pouring vessel resulting in a molten iron having a sulphur content from 0.002 wt. % to 0.006 wt. %; e) pushing the molten iron from the pressurized pouring vessel to the pouring basin; f) pouring a stream of the molten iron from the pouring basin into a mould through the stopper/nozzle mechanism; and g) allowing the molten iron to solidify in said mould; wherein the molten iron is treated, after step d) and prior to step g), either simultaneously with an additive composition and with an inoculating composition, or sequentially, either first with the additive composition, and subsequently with the inoculating composition, or vice versa; wherein the additive composition comprises a source of sulphur, a source of selenium and, optionally, a source of tellurium and/or a source of rare earth elements, and comprises a carrier selected from ferrosilicon, iron powder, and iron oxide; and wherein the additive composition comprises from 2 wt. % to 60 wt. % of sulphur based on the total weight of the additive composition, and from 0.5 wt. % to 20 wt. % of selenium based on the total weight of the additive composition; and wherein the total content of sulphur, selenium, and optionally, tellurium and/or rare earth elements, in the resulting molten iron is increased by a total amount from 0.002 to 0.012 wt.% respect to the weight of the molten iron.