What is ET₀? Evapotranspiration explained

If you track one number to schedule irrigation, make it ET₀. It tells you, every day, how thirsty the atmosphere is — and therefore how much water your crops are losing.

ET₀ in one sentence

ET₀ (reference evapotranspiration) is the water, in millimetres, that a reference grass surface loses to evaporation and transpiration in a day, given the temperature, humidity, wind and sunshine.

From ET₀ to how much you irrigate

Multiply ET₀ by a crop coefficient (Kc): ETc = ET₀ × Kc. Subtract effective rainfall and what’s already in the soil, then replace the balance. On a 6 mm ET₀ day with Kc 0.7, your crop used ~4.2 mm — that’s your target.

Watering by ET₀ beats the calendar: it saves water on mild days and protects yield on extreme ones. Rooted’s Agri-Climate Insight tracks it for your farm and RootBot pushes the 7-day ET₀ forecast to WhatsApp.