The seeder (1) has a sowing bar (4) connected to a reference body (3) using a connection structure (5) comprising an upper rod (10) provided with two joints (18, 19) and a lower rod (11) provided with two joints (20, 21). The joints respectively form a deformable quadrangle. A sowing depth adjusting device (8) and a depth control adjusting device (9) act on the connection structure that pivots around a transverse joint (6) by a shifting arm (7). The sowing depth adjusting device, the depth control adjusting device and the arm are provided in a manner to extend in size of the structure. An independent claim is also included for a combined tilling and sowing agricultural machine comprising a tilling machine.
