Crop yield response to water - Cra

Lead AuthorSCristos Xiloyannis(Università degli studi dellaBasilicata, Potenza, Italy),Bartolomeo Dichio(Università degli studi dellaBasilicata, Potenza, Italy)Contributing AuthorsElias Fereres(University of Cordoba andIAS-CSIC, Cordoba, Spain),Giuseppe Montanaro(Università degli studi dellaBasilicata, Potenza, Italy)ApricotIntroduction and BackgroundThroughout the world, 90 percent of commercially grown apricots arederived from the Prunus armeniaca (L.) specie, a few cultivars arefrom P. mume or P. sibirica, or more recently, originate from apricot× plum (and vice versa) hybrids. Apricots are small-to-medium sized treeswith spreading canopies (usually kept under 3.5 m), cultivated for freshor processed fruit (dried, jam, juice), and for their oil extracted from thekernel. Apricot grows well in temperate regions; however, it is also able totolerate very low temperatures during winter. Particularly, P. sibirica cantolerate air temperatures of about -35 °C, and soil temperatures down to-13 °C at the 40 cm depth did not damage its roots (Kramarenko, 2010).Total global production in 2009 was 3.73 million tonne on 504 000 ha(FAO, 2011). Figure 1 presents the evolution of production since 1985.Turkey is the main producer, followed by Iran; Italy is the first producer inthe European Union. Most cultivars mature between the end of April andend of June (Northern Hemisphere). Over the last five years, new cultivarswith a much later maturity date (August-September) have been bred andintroduced in some areas.Normal plantation density is about 400-500 tree/ha, using some trainingsystems (e.g. transverse Y) density could reach 1 200–1 500 tree/ha. In thiscase careful canopy management (e.g. summer pruning) is required tominimize excessive shading that reduces water-use efficiency at the leaflevel (Figure 2), the size, sugar content and colour of the fruit, bud inductionand flower quality for next year yield and the level of carbohydrate stored inthe buds, flowers and shoots (Nuzzo et al., 1999 and Xiloyannis et al., 2000).Stages of Development in relationto Yield DeterminationFloral bud induction begins in late spring or summer. The chilling requirementsfor flowering (No.of hours < 7 °C), range from 300 to 1 200, dependingon the cultivar. The minimum bloom temperature (namely the GDH heatunits required after rest (Ruiz et al., 2007)) is relatively low, causing apricotsto bloom (and leaf out) early in most locations, thus apricot flowers andnew shoots tend to suffer frost injury in early spring. Apricot trees breakdormancy and begin to bloom in the Northern Hemisphere by mid-February,depending on the environmental conditions and cultivar. Usually, flowering432crop yield response to water