Determination of Leaching Fraction in Ardakan Pistachio Orchards through Integration of Wetting Front Detector and Electromagnetic Induction Devices

Accurate measurement and mapping of leaching fraction (LF), as a key parameter in saline irrigation management, is a time consuming and expensive process. This research was carried out in 62 ha of Ardakan pistachio orchards of Yazd province in 2012 for measuring and mapping of LF through integration of the data obtained from Wetting Front Detector (WFD) and Electromagnetic induction (EM₃₈) devices. For this purpose, 24 WFDs were installed in the region to extract root zone leachate waters and to measure their electrical conductivities (EC_dw) as well as chemical constituents (Cl, Na, K, Ca and Mg). Soil samples were also collected in these points for EC_e measurements. Additionally, EC_e in 90 points were measured with the aid of EM₃₈ and used for mapping of soil EC_e. After calculation of LF as EC_iw/EC_dw, relationships between LF and soil EC_e was modeled as LF=f(EC_e). After statistical evaluation of the equation, it was applied to the EC_e map to generate final LF map. Drainage water analysis showed that Na and Cl were the dominant ions in leachate waters (71.6% and 74.6%, respectively), as well as in irrigation water. Also, good agreement was found between LF and soil EC_e values with R²=0.67 and RMSE=0.054, which led to generation of final LF map. This map, as a demonstration of irrigation management, can be used for planning of irrigation and also improvement of existing management strategies in the studied area.