The object of the present invention is constituted by an improved self-compensating dropper, for underground irrigation, which is provided at its out-put mouth (1) with a spherical valve (2), of irreversible unidirectional flow in the out-put direction, though it prevents the entrance to its interior, of earth or gravel which might obstruct it or make it unusable. The sphere (2) is retained by a central stop (6) joined to the body of the dropper by attachment lugs (5), among which there are orifices (4) in the shape of circular crown segments through which the irrigation water may flow.