The invention relates to a direct-injection spraying device for a vehicle, in particular an agricultural vehicle, including: a main tank (C)； at least one spray boom (R)； a circuit connecting said tank (C) to said boom (R), said circuit comprising a main pump (PP) and a bypass (d) for controlling the flow rate in said boom (R) in accordance with the traveling speed of said vehicle； at least one active material store (m1, m2, m3) connected to said circuit by a metering pump (P1, P2, P3). Said device includes a mixer (M) capable of receiving, at the inlet (E1) thereof, the liquid from said main tank (C), as well as the pressurized liquids from said bypass (d) and said active material store (m1, m2, m3), and capable of supplying, at the outlet thereof, the mixed liquids to said main pump (PP), which thus sucks in the mixture of said liquids.
