Abstract: The mixing device for liquid fertilizer with a flow of irrigation water, comprises a mixing head (1) provided with an internal mixing chamber (2) into which opens an internal water supply channel (3), adapted to be connected to a source (4) for the distribution of water under pressure, an internal liquid fertilizer supply channel (5a) connected by a supply circuit (5) to a remote reservoir (7), and an internal channel (8) for distribution of water with liquid fertilizer added, can be connected to a distribution element (9). The chamber (2) is arranged as a Venturi device such that the flow of water through the chamber (2), from the water supply channel (3) toward the distribution channel (8), causes an effect of sucking liquid fertilizer into the chamber (2) to mix it in this latter with the flow of water.