The present invention is an irrigation method and system for providing a user-defined flow rate to a field using variable sized orifices. The irrigation method and system includes providing a source of irrigation water. A first discrete area to be irrigated is defined and the volume of irrigation water to be disbursed to the first discrete area is determined based on the type of crop. A length of continuous irrigation conduit is provided so that the irrigation conduit is in fluid communication between the source of irrigation water and the first discrete area. The required diameter of each orifice is calculated based on the user-defined flow rate. Each orifice is made in the irrigation conduit as the conduit is installed in the field so that the irrigation water is disbursed to the first discrete area in an amount approximate to the user defined flow rate.