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1 2 Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the Mediterranean 3 basin. The objective of this work was to quantify soil salinity through electromagnetic induction (EMI) 4 techniques and relate it to the physical characteristics and irrigation management of four Mediterranean 5 irrigation districts located in Morocco, Spain, Tunisia and Turkey. The volume and salinity of the main water 6 inputs (irrigation and precipitation) and outputs (crop evapotranspiration and drainage) were measured or 7 estimated in each district. Soil salinity (EC e ) maps were obtained through electromagnetic induction surveys 8 (EC a readings) and district-specific EC a -EC e calibrations. Gravimetric soil water content (WC) and soil 9 saturation percentage (SP) were also measured in the soil calibration samples. The EC a -EC e calibration 10 equations were highly significant (P < 0.001) in all districts. EC a was not significantly correlated (P > 0.1) with 11 WC, and was only significantly correlated (P < 0.1) with soil texture (estimated by SP) in Spain. Hence, EC a 12 mainly depended upon EC e , so that the maps developed could be used effectively to assess soil salinity and 13 its spatial variability. The surface-weighted average EC e values were low to moderate, and ranked the 14 districts in the order: Tunisia (3.4 dS m

Field experiments were conducted for 3 years from 2000 to 2002 to assess proportional crop yield differences obtained under conventional deficit irrigation (CDI) and partial root zone irrigation (PRI) practices, compared with full irrigation (FULL) where plant water requirements were fully met. The experimental crops included vegetables (tomato and pepper), field crops (maize and cotton) and citrus. The fruit yield of greenhouse-grown tomato with FULL irrigation was higher than with PRI (7-22% lower) but was not significantly different. The PRI treatments had 7-10% additional tomato yield over CDI receiving the same amount of water. The yield of pepper, however, decreased in proportion to the level of irrigation deficit with no increase of irrigation water use efficiency (IWUE). No seed yield decrease was evident for cotton with the deficit treatments (PRI and CDI) compared with FULL irrigation. Similarly, the PRI treatment did not give any yield benefit for maize compared with CDI. The ranking of fruit yields of mandarin, FULL > PRI > CDI, was the same as that of other crops; however, the differences were not significant. Although the deficit treatments (PRI and CDI) had as high as 39% increase in IWUE, compared with FULL treatment, some adverse effects on fruit quality were evident such as smaller size of fruits under the deficit treatments.