Crop yield response to water - Cra

equirements per unit land area for orchard establishment, but smaller orchards can beeconomically sustainable if they are adequately designed for intensive production. Anotherdrawback is the higher water requirements associated with greater radiation interception,especially during the first years of the orchards (Box 1).Methods of irrigationIrrigation has both scientific and technological components and recent improvements oftree and vine crops have involved primarily the latter; the adoption of improved irrigationsystems. The traditional method used in the past was surface irrigation, primarily with furrowsor small basins, as is still practised today in many areas (Figures 2 and 3). The introduction ofsprinkler irrigation in the 1950s had limited impact on tree crops, although it was useful todevelop new plantations on steep land that was not amenable to surface irrigation (Figure 4).In the mid-1960s, drip and other forms of microirrigation were invented, which portended adrastic change in tree and vine irrigation. For the first time, growers had not only control ofhow much water was applied but could fully overcome the limitations of harsh topography.Furthermore, it was possible to apply water only to the areas near trees planted on unevenland, thus avoiding conveyance and evaporation losses from the zones not explored by treeroots. This was particularly important in the first years of the orchard when significant watersavings could be achieved by using microirrigation. This benefit diminishes with time and asorchards approach maturity, and more ground area is shaded, evaporation losses become onlya small component of consumptive water use. Nevertheless, if trees are widely spaced and thewetted soil areas are extensive and sunlit, surface evaporation can still be a significant part oforchard water use, as in the photograph in Figure 5.Another significant advantage of microirrigation is its adaptability to large and small growers,and the simplicity of its management. The success of the drip method for orchard irrigationBox 1 Investment costs (US$/ha) of conventional and intensive irrigated orchards: an example.Conventional Tree Spacing: 8 x 6 m equivalent to 208 tree/haIntensive Tree Spacing: 5 x 2 m, equivalent to 1 000 tree/ha208 tree/haCosts (US$/ha)1 000 tree/haCosts (US$/ha)Trees 505 2 438Tutoring 169 810Holes 1 685 8 100Microirrigation system 3 650 13 740Total 6 009 25 078Costs (determined in Spain in 2010) are around four times higher for the intensive orchard in this case;however, benefits will also differ and it is possible that, in certain situations, the greater production inthe first years and the higher productivity of intensive orchards may outweigh the costs.Yield Response to Water of Fruit Trees and Vines 249