Irrigation scheduling is a planning and decision- making process, the primary decision being: how much water to apply and when to apply it. How much water to apply depends on (1) the soil’s available moisture storage capacity and (2) the amount of available water depleted from the soil profile by crop water use. (Soil moisture storage capacity, as ex- plained later, is determined by available-water holding capacity of the soil and crop rooting depth.) When to apply irrigation water depends on rate of water use by the crop and the total available soil moisture. This publication deals with the why’s and how’s of corn irrigation scheduling. Discussed are the potential benefits of proper scheduling; the crop, soil, and climatic factors involved and their relationships; methods of determining irrigation timing; and schedul- ing considerations unique to different climatic regions.