Nadler, A., Dept. of Soil Physical Chemistry, Soil and Water Institute, Volcani Center, Bet Dagan, 50250, Israel
Erner, Y., Dept. of Citriculture, Institute of Horticulture, Volcani Center, Bet Dagan, 50250, Israel

During a 6-year salinity experiment in a citrus (Shamouti) grove, 3 salinity levels of irrigation water (0.8, 1.3, and 1.7 dS/m) were used. Measured salinity levels depended on the monitoring technique, aqueous extract (Ext) v. electrical resistance (4 electrode method, 4P), and consistently differed by up to 50%. The main advantages of the resistivity method over sampling are: specific consideration of the actual water content at time of measurement, minimal disturbance of the natural soil structure and chemical composition, and a reduced spatial variability due to the possibility of repeated measurements at one spot. Despite massive salt inputs (12x103-36x103 mmol charge(+)/ha), the final salinity levels, even according to the higher estimating resistivity method, were moderate, and during the 6 years had no significant effect on yield. It could thus be categorised as being either below or above the yield-reducing threshold value, depending on the measuring technique.