A drip irrigation emitter includes a housing containing an inlet opening for receiving water from a supply tube and an outlet opening for emitting water at a pressureless drip rate. A labyrinth inside the emitter receives water from the supply tube through the inlet opening, reducing its pressure and emitting the water at a drip rate. A flexible pressure-compensating diaphragm inside the housing flexes elastically under pressure changes of water entering in the opening from the supply tube. A raised structured surface positioned between the inlet opening and the diaphragm prevents the diaphragm from sealing off water entry to the emitter housing through the inlet opening when water pressure in the supply tube is shut off. The raised structured surface is configured to allow air contained in the soil to be drawn backwards through the emitter at a very slow rate, thereby inhibiting emitter blockage caused by soil ingestion.