Abstract: An irrigation system controller that operationally ties the dispensing of water to the soil directly to the need thereof without requiring continuous monitoring by the irrigation manager. If a preselected water supply period is not sufficient to attain a desired moisture content in the soil due either to an insufficient estimate on the part of the manager or a power or equipment failure or unforeseen change in weather, a warning device or other electrically-operated signal calls attention to the need for the selection of a new longer water supply period or a correction of the power or equipment failure. A pushbutton switch resets the warning system. If the preselected water supply period is sufficient to maintain the desired moisture content, a feed-back loop automatically controls the dispensation of water to maintain the desired moisture content of the soil.