Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering. The goal is to apply enough water to fully wet the plant's root zone while minimizing overwatering and ensuring high water use efficiency (WUE).

Modern scheduling has evolved from simple calendar-based timers to "smart" systems that adapt dynamically to weather conditions and soil moisture levels.

Irrigation scheduling can be grouped into three primary methodologies, ranging from observation to advanced data analytics.

The most basic form of scheduling relies on visual cues or physical inspection.

This method uses sensors placed directly in the root zone to measure the volumetric water content or soil water tension.

These sensors can act as a "thermostat" for irrigation, triggering the system only when moisture drops below a specific Management Allowed Depletion (MAD) threshold.

Also known as the "Checkbook Method," this approach calculates the water balance of the soil. It treats the soil reservoir like a bank account:

The daily soil water balance equation is often expressed as: