The irrigation regime is determined by:

• • soil moisture,
• • the plant’s condition,
• • the most critical periods for water,
• • external changes or
• • internal physiological indicators.

When performing the irrigation of orchards the important question is the dosage of water. Optimal humidity in the soil can be achieved and maintained only if the water in the rhizosphere zone is used expertly. If the irrigation is carried out more often than necessary, it may come to a large dose of water and irrigation problems, poor aeration and root suffocation. If the irrigation is used less often and a smaller amount of water than necessary is added, high-quality fruit production can not be achieved.

For the professional dosage of the water it’s mandatory, in each irrigation operation, to properly determine:

- the irrigation norm

- the start moment of irrigation

The irrigation norm (mm) depends on the culture and cultivated land. The depth of soil that needs to be moistened depends on the depth of roots ie of the type of the culture and development stage of the plant.  The soil should be moistened by the irrigation norm to the field water capacity (FWC).  Soft (sandy) soil requires a lower irrigation norm than the hard (clay) soil. However, sandy soils need more frequent irrigation than clay ones, because plants need the same amount of water regardless of the land on which they are grown. The depth of moisture in irrigation (m) for plum, apple, peach, pear, apricot is 0.40-0.60 m.

When to start watering?

In practice the start moment is determined in several ways:

- by external morphological changes on fruit trees

- by a valuation of the soil dampness

- by critical periods of fruit trees for water

- by a determined schedule of irrigation

- by measuring soil dampness

- by the internal physiology changes of fruit trees.

The recommendation for determining the start moment of irrigation :

- by measuring soil dampness

- by the daily consumption of water

At the very location, measurement of humidity is made by tensiometer, neutrons and gamma rays, electrometry measuring, and hygrometer. Hygrometers in orchards represent a new way of measuring. A hygrometer measures humidity at every moment, in the growing of all cultures and all sorts of soils. Calculating the daily consumption of water is balancing the water in the soil, based on the inflow and the water consumption during the vegetation period.

Balancing of the water can be done in several ways, and one of them is using the coefficient of irrigation. The coefficient of irrigation is the amount of irrigation water in mm consumed per one degree of the daily air temperature (mm / 1 degree Co.).