Abstract: An automatic liquid delivery apparatus dispenses liquid from a liquid container or other liquid supply to a receiver or zone requiring liquid in response to a detector which is located in the zone and initiates discharge of the liquid. The liquid is retained against discharge from the container or supply by air pressure in a liquid passage and is discharged upon release of the air through the detector, when liquid is needed in the receiver or zone.The automatic liquid delivery apparatus in a liquid feeding system may be used to supply liquid to growing plants; a detector for each plant or group of plants initiates the dispensing of liquid by a delivery apparatus, each detector sensing the moisture requirements of a particular plant.