Precision agriculture involves very accurate farm vehicle control along recorded paths. Such repetitive tasks could be handled using Automatic Guided Vehicles (AGV). In this paper, we address the problem of farm tractor control using a single CP-DGPS receiver. A non linear, velocity independent control law has been designed to perform both curved paths and straight lines following. It relies upon the kinematic model of the farm tractor. The control law has been implemented on a commercial farm tractor. Step response as well as curve following are presented and discussed.