Influences of treated waste water on citrus sap flow, water relations and growth in two soils

Declining orchard yield and soil properties following long term irrigation with treated waste water (TWW) in clay soils have been reported in the last decade. We examined citrus orchard recovery after replacement of TWW with fresh water (FW) in clay and sandy soil lysimeters. An additional treatment in sandy soil was TWW enriched with NaCl (TWW+Na) to increase the SAR. FW irrigation decreased soil salinity and Na and Cl in leaves and roots. Leaf chloride exceeded the threshold value for Cl toxicity only in the clay soil irrigated with TWW and in the sandy soil irrigated with TWW+Na. Sap flow and mid-day stem water potential were reduced by poor quality water in both soils, and relative differences increased with time into the irrigation season in both years. Sap flow and water potential were higher in sandy than clay soil. TWW reduced fruit yield in the clay soil, whereas in the sandy soil only TWW+Na caused such a reduction.