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Partial Root-zone Drying (PRD) is a new irrigation technique in which half a plant root system is exposed to drying soil, while the other half is kept in wet soil. Field experiments were conducted on olive trees (Olea europaea) grown under arid conditions in southern Morocco and subjected to four irrigation treatments using a localized irrigation system: Control (irrigated with 100% of crop evapotranspiration (ETc) on both sides of the root system); PRD1 (50% of ETc applied to one side of the root system, alternating every two weeks); PRD2 (50% of ETc applied to one side of the root system, alternating every two irrigations [every four weeks]); and PRD3 (100% of ETc applied to one side of the root system, and alternating every two weeks). The PRD treatments significantly affected olive tree-water relations, starting with an increase in stomatal resistance and, subsequently, leaf water potential. The hypothesis of a PRD-induced chemical signal was supported by the observation that stomatal closure was similar in all PRD treatments, including PRD3, which had exactly the same level and evolution of leaf as did the control. The PRD1 and PRD2 treatments induced a slight reduction in the average shoot length and fruit yield. Olive yield was significantly higher for the control and PRD3 treatments compared to PRD1 and PRD2. The oil percentage in olive fruit and oil acidity did not show any significant differences between PRD treatments and the control. The PRD-induced yield reduction (15-20%), as compared to the control, was achieved with a 50% reduction in the total amount of water applied, a water-use efficiency increase of 70% under PRD treatments. Values of the photosynthetic parameters Amax, Jmax, Vcmax, Rd and Jmax/Vcmax ratio were not significantly influenced by the irrigation treatments.
crop quality, crop yield, evapotranspiration, fruits,irrigation, leaf water potential, leaves, olive oil, olives,photosynthesis, plant water relations, roots, shoots, stomata, stomatalmovement, water use, water use efficiency, Morocco, Olea europaea,Maghreb, North Africa, Africa, Mediterranean Region, DevelopingCountries, Francophone Africa, Olea, Oleaceae, Scrophulariales,dicotyledons, angiosperms, Spermatophyta, plants, eukaryotes, carbonassimilation, carbon dioxide fixation, Oleales, watering, HorticulturalCrops (FF003) (New March 2000), Plant Water Relations (FF062), PlantProduction (FF100), Soil Water Management (Irrigation and Drainage)(JJ800) (Revised June 2002) [formerly Soil Water Management], CropProduce (QQ050), Food Composition and Quality (QQ500)