Crop yield response to water - Cra

Lead AuthorSRiccardo Gucci,(University of Pisa, Pisa, Italy),Elias Fereres(University of Cordoba andIAS-CSIC, Cordoba, Spain)Contributing AuthorDavid A. Goldhamer(formerly University of California,Davis, USA; currentlyCooperative Extension Emeritus)OliveGeneral descriptionOlive (Olea europaea L.) is an evergreen tree grown primarilybetween 30 and 45° latitude in both hemispheres. In 2008 totalharvested area was over 10 500 000 ha, 95.5 percent of which wasconcentrated in ten countries surrounding the Mediterranean Sea (FAO,2011). Spain, Italy and Greece are the main producers of virgin oil followedby Tunisia, Syria, Turkey and Morocco (years 2002-2008). About 90 percentof the world production of olive fruit is for oil extraction, the remaining10 percent for table olives. The world cultivated area of olives in 2009was over 9.2 million ha with an average yield of 2.1 tonne/ha (FAO, 2011).Figure 1 shows the evolution of olive production over the last decades inthe principal countries. European Union countries produce 78 percent andconsume 68 percent of the world's olive oil.Olive trees have been sparsely planted for centuries, without irrigation, onmarginal lands in Mediterranean climate conditions because of their highresistance to drought, lime and salinity. Typical densities of traditionalgroves are between 50 and 100 tree/ha with trees severely pruned tostimulate vegetative growth and renewal of the fruiting surface, andthe soil periodically tilled. Fruit yields are low, ranging from less than 1up to 5 tonne/ha of olives. Although traditional groves vary in cultivarcomposition, tree density, training system, degree of mechanization andchemical inputs, they are still the most widespread production systemand a landmark of Mediterranean landscapes. Intensive orchards have adensity of between 200 and 550 tree/ha, which translates into a higherfraction of intercepted radiation that leads to higher productivity per unitland area than traditional systems, particularly during the first 10 years ofproduction. Trees are trained to a single trunk for mechanical harvestingand the soil is often managed by temporary or permanent grass coverto reduce erosion and ease traffic in wet periods. In areas of annualrainfall higher than 600 mm, production can be maintained under rainfedconditions in soils with good water-holding capacity. However, irrigationplays an important role in the drier areas, and/or for soils with limitedwater storage. Elsewhere, irrigation plays an important role to stabilizingyields in the years of low rainfall. Irrigation is becoming common in theintensive orchards as it allows early onset of production (from the secondto forth year after planting), high yields (averages up to 10-15 tonne/ha)under optimal conditions and less variability because of alternate bearing.300crop yield response to water