Response of young bearing olive trees to irrigation-induced salinity

Abstract

Expansion of irrigated olives, combined with prevalence of water containing dissolved salts, leads to irrigation-induced exposure of olive trees to salinity. Root zone salinity can rise either as a function of increasing input irrigation water salinity (ECi) or relative reductions in water for leaching. We investigated five ECi levels from 0.5 to 11.0 dS m−1 with a constant leaching fraction (LF) of 0.29 and five leaching levels from 0.05 to 0.44 (drainage: irrigation ratio) with water of ECi = 5.0 dS m−1 on young bearing Olea europaea cv Barnea olive trees grown in 2.5 m3 weighing-drainage lysimeters over three years. Tree-scale response to increased salinity did not demonstrate any sign of a threshold value and was not differentiated by the cause of salinity, be it changes in input irrigation water salt concentrations or changes in LF. Soil salinity, measured as electrical conductivity of saturated soil paste extract (ECe) and maintained at stable levels over time, decreased tree water consumption and tree size measured as trunk area or above-ground biomass by 40–60 % as it increased from 1.2 to around 3.5–4.0 dS m−1. Further increases in ECe to as high as 7.5 dS m−1 brought these parameters to 20–30 % of the treatment with low salinity. Fruit yield also decreased with increasing salinity, albeit with less drastic relative effects. An analytical model calculating water and salt balance and subsequent evapotranspiration or biomass as a function of irrigation water quantity and salinity successfully predicted the measured results.