OLIVE TREE STEM DIAMETER VARIATIONS UNDER IRRIGATION BASED ON PLANT AND SOIL PARAMETERS

Under adequate Soil Water Availability (SWA) conditions, the general trend of the DSDG and the Daily Stem Diameter Contraction (DSDC) was mainly influenced by the atmosphere water demand and less by the level of SWA. The DSDG course for both P_ir and S_ir irrigation treatments was generally low during winter months, while it increased progressively from spring to summer and then decreased till winter. The daily rate of the DSDG per month did not present notable differences among the P_ir and the S_ir treatments, showing that P_ir provided an equivalent growth potential as the S_ir treatment. The daily rate of the DSDC per month followed an opposite to the DSDG trend, but it presented a marked difference among treatments being notably higher in the S_ir than in P_ir.

In the morning hours the Hourly Stem Diameter Contractions (HSDC), were correlated with Leaf Water Potential (₁) with two different linear equations for both the W and S regimes. In the afternoon hours, on the contrary, the HSDC was correlated with ₁ with polynomial equations. The Stomatal Resistance (Rs) was higher in the S than in the W level due to the ability of the trees to close the stomata and reduce transpiration under water stress conditions.

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