Leaching is required to wash out accumulated salts from the soil. The total amount of leaching (as a percentage of annual NIR) depends on the type of crop and the salinity class of the irrigation water (soil type is not considered in the irrigation module at all).
For later balancing, the shape (monthly distribution) of the irrigation demand hydrograph is of importance). If the water distribution system permits, it is advisable to perform leaching not along with irrigation but during the winter months, when demand is lowest and availability usually the highest.
The months, during which leaching should take place, can be interactively selected by the user. In "Form0 - Selected Irrigation Centers", on the right side there is a button to modify the leaching calendar.
Pressing this button will cause a form to pop-up, which permits to select the leaching months. This selection will stay until it is changed again.
Note: leaching months can be only selected from this form and not later (e.g. under the scenarios).