This document discusses soil-plant-water relations and irrigation scheduling. It explains that the effective root zone depth and a plant's rooting characteristics must be understood to design an efficient irrigation system. Different soil properties like hardpans can influence root development. Irrigation scheduling aims to determine how much and how often to irrigate to minimize water stress on crops. Methods of scheduling include soil indicators, climatological data, plant indices, and water balancing approaches. The document also discusses concepts like full irrigation, deficit irrigation, and critical growth stages.