Vegetative growth response of young olive trees (Olea europaea L., cv. Arbequina) to soil salinity and waterlogging

High-density olive orchards are increasing around the world, many of which may be potentially affected by salinity and waterlogging (hypoxia), two important stresses common in irrigated fields in arid and semi-arid climates. However, the response of olive to these stresses under field conditions is not well established. Therefore, our objective was to evaluate the vegetative growth response of young olive trees (Olea europaea L., cv. Arbequina) grown in a spatially variable waterlogged, saline-sodic field. We monitored the growth in trunk diameter of 341, 3-year-old olives between September 1999 and September 2000. Field contour maps were developed delineating soil salinity (ECa), relative ground elevation (RGE) and water table depth (WTD). Soil samples were also collected and analyzed for ECe and SARe in order to characterize the salinity and sodicity profiles and develop the ECa-ECe calibration equation. The infiltration rate (IR) of the crusted and uncrusted soil and the penetration resistance (PR) were also measured. The field was characterized by spatially variable ECe (2–15 dS m^–1), SARe (3–40), RGE (–4 to +4 cm) and WTD (0.5–1.9 m, with corresponding ground water EC values between 12 and 6 dS m^–1). Steady-state IR of crusted soil was only 7% of the uncrusted soil. Since the field was heavily irrigated by flooding, waterlogging conditions were related to low RGE values. Soil salinity was negatively correlated (R ² = 0.83, P<0.001) with RGE (ponded water) and WTD (upward flux), due to the evapo-concentration of water and salts at the soil surface. Thus, inverted salinity profiles developed in high salinity areas. Fifty-five percent of the olives were dead 3.5 years after planted, and most of them were located in areas of high ECe (> 10 dS m^–1), low RGE (< – 1.5 cm) and low WTD (< 1.2 m). The surviving trees had vegetative salinity tolerance values of ECe threshold = 4 dS m^–1 and slope = –12% (i.e., percent decline per unit increase in ECe above the treshold), indicating that the Arbequina olive is moderately tolerant to salinity. The RGE and WTD thresholds for olive's survival were > 0.1 cm and > 1.6 m, respectively. Thus, very small changes in ground elevation had a significant effect on olive's survival or death. The coupled effects of salinity and waterlogging (hypoxia) stresses were most detrimental for olive's growth.