The first results of studies with hedgerow or superhigh-density orchards (714 to 1975 olive/ha) were reported in Italy by Morettini (1972). However, it was not until the 1990s that this production system was commercially adopted. Since then, it has spread rapidly worldwide, currently accounting for an area of ≈40,000 ha with a growth rate of 10,000 ha per year. The objective of this system is to obtain high yields from the early years of establishment and an orchard structure suited to mechanical pruning and harvesting. In these orchards, trees are usually pruned to a central leader and fruits are harvested with modified grape harvesters.
Early high yield is achieved by reducing the unproductive period that is determined by cultivar, edaphoclimatic conditions, and orchard management practices. However, shoots need time both to occupy the entire hedgerow and to adequately develop reproductive (flower) buds. These two aspects are inversely related because vegetative vigor is inimical to reproductive development. Irrigation management impacts these components of the unproductive period in different ways. Water stress is well known to reduce vegetative growth and to stimulate flowering in various woody plants (Meilan, 1997). Although water stress closes stomates, reducing photosynthesis and growth, its effect on flowering is less certain. It may be the result of a direct effect of hormone production on flower initiation or increased nutrient concentration in growing buds. Abscisic acid (ABA), an antigiberelic acid, has been reported (Davies et al., 1986) as the most important water stress hormone in plants. In olive, Kitsaki and Drossopoulos (2005) reported increased ABA in leaves of stressed plants, which was negatively related to leaf water potential, whereas Baktir et al. (2004) found that high ABA concentrations and low gibberellic acid favor olive bud initiation. This could explain the increase in the number of inflorescences per shoot observed in water stressed olives by Gucci et al. (2007).
Cv. Arbequina is mainly used in hedgerow olive orchards because of its short unproductive period, but it is less resistant to frost than ‘Cornicabra’, the most important cultivar in the Center Region of Spain (269,000 ha) (Barranco, 2008). In this study, the effect of different irrigation treatments on a young olive orchard during the unproductive period was evaluated in the Center Region of Spain, characterized by low fall and winter temperatures. A 2-year-old hedgerow orchard of ‘Cornicabra’ was subjected to four irrigation regimes during the second and third years after planting to determine if water stress could be useful for enhancing early olive fruit production. Stem water potential and leaf conductance were measured and their effect on vegetative growth, canopy development, and flowering was evaluated. Additional data of the third growth period have been published previously (Gómez-del-Campo et al., 2008). The relationships among stem water potential, vegetative growth, and soil water status were also studied.
Allen, R.G., Pereira, L.S., Raes, D. & Smith, M. 1998 Crop evapotranspiration. Guidelines for computing crop water requirements Irrigation and drainage paper 56 FAO, Rome, Italy
Baktir, I., Ulger, S., Kaynak, L. & Himelrick, D.G. 2004 Relationship of seasonal changes in endogenous plant hormones and alternate bearing of olive trees HortScience 39 987 990
Barranco, D. 2008 Variedades y patrones 65 92 Barranco D., Fernández-Escobar R. & Rallo L. El cultivo del olivo Mundi-Prensa Madrid, Spain
Davies, W.J., Metcalfe, J., Lodge, T.A. & da Costa, A.R. 1986 Plant growth substances and the regulation of growth under drought Aust. J. Plant Physiol. 13 105 125
Gomez-del-Campo, M., Leal, A. & Pezuela, C. 2008 Relationship of stem water potential and leaf conductance to vegetative growth of young olive trees in a hedgerow orchard Aust. J. Agr. Res. 59 270 279
Grattan, S.R., Berenguer, M.J., Connell, J.H., Polito, V.S. & Vossen, P.M. 2006 Olive oil production as influenced by different quantities of applied water Agr. Water Mgt. 85 133 140
Gucci, R., Lodolini, E. & Rapoport, H.F. 2007 Productivity of olive trees with different water status and crop load J. Hort. Sci. Biotechnol. 82 648 656
Kitsaki, C.K. & Drossopoulos, J.B. 2005 Environmental effect on ABA concentration and water potential in olive leaves (Olea europaea L. cv ‘Koroneiki’) under non-irrigated field conditions Environ. Exp. Bot. 54 77 89
McCutchan, H. & Shackel, K.A. 1992 Stem-water potential as a sensitive indicator of water stress in Prune trees (Prunus domestica L. cv. ‘French’) J. Amer. Soc. Hort. Sci. 117 607 611
Pérez-López, D., Moriana, A., Rapoport, H., Olmedilla, N. & Ribas, F. 2008 New approach for using trunk growth rate and endocarp development in the irrigation scheduling of young olive orchards Scientia Hort. 115 244 251
Testi, L., Villalobos, F.J. & Orgaz, F. 2004 Evapotranspiration of a young irrigated olive orchard in southern Spain Agr. For. Meteorol. 121 1 18