Scheduling regulated deficit irrigation in a hedgerow olive orchard from leaf turgor pressure related measurements

Regulated deficit irrigation (RDI) has been proposed as one of the most promising irrigation strategies for hedgerow fruit orchards with high plant densities. Scheduling a RDI strategy, however, is highly demanding, since the targeted water savings must be achieved at the same time that episodes of excessive water stress are avoided when the crop is most sensitive to drought. Here we tested an approach to schedule a RDI strategy supplying 45% of the crop irrigation needs, specially designed for hedgerow olive orchards. Our approach is based on the use of a water stress indicator derived from the shape of the daily curves recorded with ZIM sensors, which are related to the leaf turgor pressure. We worked in a mature, fully productive ‘Arbequina’ olive orchard with 1667 trees ha−1, under both a daily irrigated (FI) treatment and the mentioned RDI strategy. We found that the relation between the shape of the curves and the tree water stress levels holds for olive trees of different age under a wide range of growing conditions. We were able to schedule irrigation just from the visual analysis of the curves derived from the ZIM outputs, without any further data processing. A comparison with the crop coefficient approach showed that, with our approach, we achieved greater water savings without affecting neither the trees water status nor the crop performance. Still, further studies are required to confirm whether empirical aspects of our approach are limiting and, if so, to derive suitable alternatives.