Kaolin foliar spray improves olive tree performance and yield under sustained deficit irrigation

Abstract Regarding the foreseeing climate change is reasonable to expect harmful consequences to olive tree (Olea europaea L.), an iconic species of Mediterranean basin. In large areas of the Region, the sustained deficit irrigation (SDI) accounts with a reduced amount of water that might not be enough to keep the plant functioning at desirable levels. In this study the use of a reflective clay, kaolin, was evaluated in order to alleviate the negative summer stress effects on olive trees (cv. Cobrancosa) under an SDI system. Kaolin reduced the stomatal and the non-stomatal limitations to photosynthesis at high light intensity, improved plant water status, and decreased the oxidative damages. The amelioration of physiological and metabolic functions and the lower allocation of resources to summer stress tolerance mechanisms, allowed the KL-sprayed trees to increase crop yield, the oil yield and its oxidative stability, with the reduction of peroxide index and K232. Thus, the application of kaolin had a positive synergistic effect with SDI, especially important for semi-arid areas where water available for irrigation do not cover all the necessities.