Examination of Temporal Variation in the Physiological Parameters of Olive Trees in Various Deficit Irrigation Strategies

Abstract

Sensitive irrigation programming requires both a good knowledge of plant physiology regarding water use and the monitoring of the effect of water stress on plant physiology. In this study, the effect of different irrigation strategies on full-grown olive trees of the Memecik variety irrigated by the drip irrigation method was investigated over three crop seasons (2012–2013, 2013–2014, and 2014–2015), and the possibility of using these strategies in forming an irrigation program was examined. The experiment consisted of five irrigation treatments with three replications in a random block design. One significant finding after the three years of observation in the study was that it was possible to determine in a simple and sensitive way the temporal responses of olive trees under conditions of water stress with predawn plant water potential, stomatal conductance, and plant water stress index but not chlorophyll content (SPAD value). Statistically significant differences were found between the treatments in the measurements made. Taking into account the three-year averages of treatment values for water applications, acceptable threshold values for predawn plant water potential, stomatal conductance, and plant water stress index are −1.64 MPa, 330 mmol m−2 s−1, and 0.37, respectively. It is easy to put these measurements into practice, and doing so will enable very significant water savings in Mediterranean climate conditions.