A device for irrigating soil has a chassis having wheels or tracks for motion, the chassis having one or more water sprinklers with streams directed at the soil, a water storage tank or supply hose, a control valve, a water flow sensor, boundary sensor and surface moisture probes, wherein, under the control of an electronic circuit, the robotic irrigator can make even passes over the irrigated area so that water is distributed evenly and efficiently and without the use of sprinklers. A method has the steps of navigating within an irrigation area using surface moisture to determine the location of prior irrigation passes, following the profile of prior irrigation passes based on surface moisture, and utilizing the perimeter where available such that the device is always positioned for accurate and even irrigation.
