in particular it may consist of a water miscible fertilizer the mixer 10 includes a suction lance 18 which extends from a suction tip 20 adapted to suck the product 12 up to a discharge tip 22 of the sucked product the suction tip 20 of the lance 18 is mounted at the end of a manipulating arm 24 which is adapted to be manipulated by the operator to suck the product 12 contained in the bag 13 to this end the suction tip 20 has a flared shape enlarged at its free end so as to promote the suction of the product 12 in addition as shown in fig1 the suction tip 20 has a free end with a generally rectangular section which is delimited by a first linear edge forming a scraper 26 for scraping the bottom of the bag 13 advantageously the suction tip 20 has a second linear edge 28 which delimits notches 30 aiming to inhibit the flexible bag 13 from sticking to the suction tip 20 by the suction effect the discharge tip 22 of the lance 18 is linked on a mixing basin 32 via a flexible conduit 34 which links the manipulating arm 24 of the lance 18 in one form of the present disclosure the inner wall of the arm 24 and that of the associated conduit 34 are smooth and devoid of asperities so as to promote the suction and the non clogging of the product 12 when these walls are wet the mixing basin 32 presents a truncated cone shape of revolution about a vertical axis a of revolution referring to fig1 the basin 32 is delimited by a truncated cone shaped lateral wall 36 flared upwardly the basin 32 extending axially from an.