Irrigation scheduling — knowing how much water to put on and when — has a direct impact on tree health and fruit yield, size and quality.
Correct irrigation scheduling requires an understanding of how much water:
can be held in the crop root zone
is required by the crop each day
is applied by the irrigation system.
Shallow root systems
Citrus trees have shallow root systems. Dig under the canopy of a tree in an area watered by your irrigation system and you will see a mass of fine roots. Dig a little deeper and these fine roots are replaced by larger, structural roots. It is the mass of fine roots — the effective root zone — that takes up most of the water and nutrients.
Irrigation must be aimed at the effective root zone, minimising the amount of water wasted. For citrus, the effective root zone is usually the top 30 to 40cm, depending on soil type.