Predicting soil salinity in response to different irrigation practices, soil types and rainfall scenarios

A model was developed to predict rootzone salinity under different irrigation practices on different soil types, with similar rainfall but different monthly distributions. A rootzone daily water and salt balance was performed using eight scenarios: two soil types (coarse textured vs. fine textured), two multi-year series of actual rainfall data and two irrigation practices (surface with fixed number of irrigations and ET-based sprinkler irrigation). All factors influenced the mean electrical conductivity (EC) of the rootzone in the growing season (ECeS): (i) Surface irrigation led to lower ECeS than sprinkler irrigation; (ii) Winter-concentrated rainfall caused lower ECeS than rainfall distributed uniformly throughout the year; and (iii) Coarser-textured soil usually resulted in lower ECeS than the finer textured. The ECeS was related to the total precipitation of the hydrologic year and to the annual leaching fraction (LF) but surprisingly not to the seasonal LF. In most cases, the model predicted lower ECeS than the FAO steady-state approach. Therefore, considering these site-specific features could lead to lower leaching requirements and the safe use of higher salinity water.