This tractor comprises: a hydraulic vertically driving unit 17 for vertically driving a tiller and a mechanical coordination unit 18 for automatic vertical motion, which, during tilling, converts the amount of change in a towed load into the amount of vertical operation and transmits the amount of vertical operation to the vertically driving unit 17. The mechanical coordination unit 18 is provided with: a load detection member 36 which rocks forward and backward in response to a towed load a biasing mechanism 49 for rocking and biasing the load detection member 36 in the direction in which a towed load decreases a rocking member 38 supported in a rockable manner by the load detection member 36 a restriction mechanism 52 for restricting the rocking of the rocking member 38 relative to the load detection member 36 and a link mechanism 34 for connecting the rocking member 38 and the vertically driving unit 17 in a coordinated manner. The restriction mechanism 52 is provided with: a catch 57 which rocks with the load detection member 36 and a biasing unit 58 for rocking and biasing the rocking member 38 in the direction in which the rocking member 38 is pressed against the catch 57.La présente invention concerne un tracteur comprenant : une unité hydraulique dentraînement verticalement (17) pour entraîner verticalement un cultivateur et une unité de coordination mécanique (18) pour le mouvement vertical automatique, qui, durant la culture, convertit le niveau de changement dune charge remorquée en la quantité de fonctionnement vertical et transmet la quantité de fonctionnement vertical à lunité dentraînement verticalement (17). Lunité de coordination mécanique (18) est pourvue : dun élément de détection de charge (36) qui oscille vers lavant et larrière en réponse à une charge remorquée dun mécanisme de sollicitation (49) pour faire basculer et solliciter lélément de détection de charge (36) dans le sens dans lequel baisse une charge remorquée dun élément basculant (38)
