The present invention relates to a spray device with direct injection for agricultural machine intended to be sprayed, the phytosanitary products on the pieces of vegetables. The device comprises a main tank (10), containing water, connected to at least a spray boom (r) by means of a circuit. At least one reservoir (p1, p2, p3) of active substance is connected to said circuit by means of a metering pump. The spraying device further comprises a vessel of the assembly (30) containing a mixture of water - the active product to be sprayed. This mixture is carried out by introducing, by means of said metering pump, a predetermined amount of at least one active product coming from said at least one reservoir (p1, p2, p3), in a volume of water which is kept constant at a reference value within the said pot assembly (30) by injection of water from said main tank (10).
