The WEM works in conjunction with irrigation controllers to improve scheduling efficiency based on plant demand. The system will prevent irrigation cycles when the soil moisture is wetter than the adjustable set point. The device prevents valve operation by interrupting the common ground. This feature allows great flexibility in configuring the system for single valves, a group of valves (hydrozone), or the entire controller. The kit includes two Watermark soil moisture sensors. This allows for multiple placement locations, thereby averaging the soil moisture status over a larger area or deeper root depths. Eleven moisture set points allow for a wide range of variations in plant and soil type.