A control and command system for agricultural machines, wherein the agricultural machine has a supporting frame (14) and a series of tools (10) adapted for shredding the ground in depth, which are connected to a roller (11), said roller (11) being smooth or provided with spikes (16). The system comprises a sensor (S2), which measures, in a first initial condition according to which said agricultural machine rests on a fixed horizontal reference plane (T), a height difference (LM), with respect to the fixed reference plane (T), between a first horizontal level (L1) of a first support (17) fixed to the frame (14) of the agricultural machine and a second horizontal level (L2) of a second support (18) fixed to the roller (11). The sensor (S2) is also configured to measure instantaneous height differences (L) in working conditions and the control system stores the height difference (LM) and is able to measure the instantaneous height differences (L), taking into account a predefined value relative to a sinking measure (S) of the roller (11) beyond the fixed reference plane (T), so as to obtain an instantaneous depth measurement (P) of the tools (10) beyond said fixed reference plane (T).
