Abstract: Irrigation sprinkling apparatus according to the present invention may include structural means for supporting at least a portion of a mobile sprinkling apparatus that is adapted in use for rotation about a fixed point for irrigating a generally circular ground area. Each of the mobile base structures for the irrigation apparatus will include ground contacting elements such as wheels, tracks or other devices that serve to propel the respective mobile base over the land area during irrigation operations. Each of the ground contacting elements is supported for rotation relative to the respective portion of the mobile base to which it is connected and is positionable in an operating position that substantially establishes an arcuate track about said fixed point during irrigation operations and is rotatable substantially 90.degree. from said operating position for allowing substantially linear movement of said irrigation sprinkling apparatus.