An approach for estimation of maximum pistachio rooting depth in saline condition

Main objective of this research was to introduce an approach for estimation of pistachio rooting depth (D_rz) in saline condition. This approach is based on the well-known root water uptake pattern of 40-30-20-10 for successive quarters of the root zone and incorporates a trial/error procedure through including soil water salinity (EC_sw), leaching fraction (LF), depth of irrigation water (D_iw) and pistachio evapotranspiration (ET_a) parameters. Moreover, based on the concept of leaching fraction (LF) in saline condition, a hypothetical control level (e.g., 120 cm below the soil surface) was considered for comparison of the predicted and measured LF and EC_sw values at this level. In the case of field experiment, measured EC_sw of the 120 cm soil profile was to around 23 dS m^‑1, which yielded an average LF of 0.53 at the control level. Also, total depth of applied water was measured to about 1655 mm. For this case, the introduced approach yielded D_rz of an old pistachio orchard to around 340 cm. Considering the model final result (D_rz=340 cm), good agreements were observed between measured and predicted EC_sw and also LF parameters, which show reliability of the proposed approach for the estimation of maximum pistachio rooting depth in saline condition. However, more research is suggested to be carried out in other climates, soil types, salinity levels, etc.