Effect of the Super Absorbent Polymer Stockosorb® on leaf turgor pressure, tree performance and oil quality of olive trees cv. Chemlali grown under field conditions in an arid region of Tunisia

Abstract

The effects of soil amendment with the hydrophilic polymer Stockosorb® on the physical properties of the soil as well as on physiological parameters (turgor pressure, stomatal conductance, chlorophyll fluorescence) and yield (vegetative growth, fruit characteristics, oil yield and quality) of an established olive crop cultivated under rainfed conditions, were investigated in Tunisia during the 2014 growing season.Stockosorb® hydrogel was applied by injection in the soil around olive trees (TS) and compared to a control plot (TC) without hydrogel application. The results showed that water content was generally higher in hydrogel amended soils compared to the control soil. The seasonal leaf patch output pressure (Pp) readings revealed that trees with Stockosorb® treatment had the highest water status and were moderately stressed in comparison to control trees which were severely stressed due to the poor water status during the vegetative growth and fruiting period. The application of Stockosorb® in the root zone of olive trees significantly increased midday stomatal conductance (gs) and the maximal quantum efficiency (Fv/Fm). Shoot growth, oil yield and rainwater use efficiency were strongly improved by the Stockosorb® amendment to the soil, however oil quality still within the threshold limits set for an ‘Extra virgin' classified olive oil.