Crop yield response to water - Cra

Suggested Deficit Irrigation StrategiesThe suggested deficit irrigation strategy may greatly vary depending on the final marketproduct, dried fruit or fresh fruit, and on specific phenological aspects of each varietyaffecting bloom intensity and fruit set levels and particularly, earliness. The general strategyused to impose the water deficits for French prune was to limit water deficits during earlystages of tree and crop development, imposing more severe stress during mid and late season.In this sense, in a clay loam soil in California, allowing a progressive decline in midday SWPto approximately -1.5 MPa by harvest, e.g. irrigating at about 50-60 percent ET c from spring,resulted in an effective way to reduce irrigation and maintain an economic return over a3-year period (Lampinen et al., 2001a).For early season fresh market varieties it can be concluded that water stress after harvest thatlimits the decline in SWP below -2.0 MPa, despite some possible slight detrimental effect in thelong term, should be considered in commercial orchards not only for water scarcity, but alsoas a tool to control vegetative growth. In young orchards, postharvest deficit irrigation maybe combined with closer tree spacing, a feature very common in modern fruit tree plantationswhere new cultivars and orchards have a short life.For fresh market varieties water stress, if applied during fruit growth, should be concentratedduring pit hardening. The length of this phase depends on the harvest date. Hence, in earlyand even midseason maturing cultivars there is a risk of extending the water stress into thefinal fruit growth stage with detrimental effects on fruit size. Recent results (Intrigliolo andCastel, 2010) suggest that some degree of water stress can be applied during the early stageof fruit growth, providing that plant-water stress is mild (SWP > -1.4 MPa) and trees returnto optimum water status at least one month before harvest. The convenience of water stressapplied during fruit growth would indeed depend upon price market values of differentfruit size categories and fruit quality effects of water restrictions. In this sense it should beconsidered that deficit irrigation during fruit growth advances maturity, increases total solublesolids content and firmness, and may improve fruit colour. The effects of water restrictions onvolatile aroma compounds and particularly fibre and other fruit quality components relatedwith human health have not been extensively studied and could be of great importance forplum growers if the consumption of plums is promoted.354crop yield response to water