A drip irrigation system valve for placement directly onto soil, including a valve chamber defining an interior space and having an open bottom in fluid communication with the soil onto which it is placed； a water inlet in fluid communication with said interior space and having a valve seat disposed on an interior end； a base stake connected to said valve chamber for insertion into soil； a platform for supporting an expandable member； an expandable member disposed on said platform within said interior space； a valve membrane disposed within said interior space above said expandable member and having an upper side and a lower side and which defines a water reservoir within said interior space above said upper side and which prevents water entering into said valve chamber and from directly contacting said expandable membrane； and a valve seal disposed on said upper side of said valve membrane immediately above said expandable member for sealing engagement with said valve seat when said expandable member is wetted and in an expanded state.
