and automatically regulates the irrigation time so as to attain an optimum soil moisture cycle all that the user needs to set as a function of the plants to be irrigated are the two limit values gwdry and gwmoist the system can be fashioned such that a table presented by the system can be used to select sensible values that are then taken over as constants the determination of the measurement cycles can be performed in a way similar to the timers currently available the latter mostly permit the setting of the start time and the duration of an irrigation it also being possible by installing a photodiode to record the day night cycle and correspondingly to determine the beginning of an irrigation by day or at night moreover the minimum duration between two irrigations can be defined in the limit case problems can arise owing to the inflexible stipulation of the minimum duration between for example three irrigations for example three day cycles that is to say irrigation every third night by way of example specifically this means when supply of water stored in the ground is insufficient in a phase of high temperature or given crops with a very high water requirement in order to meet the requirement of this time the result being that drought stress occurs for the plants the regulation described here can however recognize.