The phenological stages of early-maturing peach trees were described using the traditional nomenclature of Baggiolini and according to the BBCH General Scale. The heat requirement of each stage was calculated as growing degree hours (GDH) and growing degree days (GDD). The annual growth pattern of trunk, shoot, and fruit was also studied. After dormancy breaking involving 225 chilling units, this early peach cultivar required ≈6244 GDH to reach full bloom and 27106 GDH before the fruit could be harvested. In the case of GDD, the heat requirements were 329 and 1246 for full bloom and fruit harvest, respectively. According to plant growth measurements, shoot growth lasted ≈7 months with a significant increase in the growth rate after fruit harvest reaching a maximum value in July. Trunk growth followed a similar annual pattern as that of the shoots but with its maximum rate occurring ≈30 days latter. Fruit growth, which lasted an average of 89 days from full bloom to harvesting, took place under mild climatic conditions (10 Feb. to 10 May) coinciding with only 30% of the total annual shoot length. This pattern of reproductive and vegetative growth pointed to the interest of redirecting regulated deficit irrigation practices in early-maturing cultivars toward postharvest water-saving strategies, but only to the extent that any limitation of shoot and trunk growth does not adversely affect the productivity of the following year.

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Root and soil water distribution was studied in a mature drip-irrigated apricot (Prunus armeniaca L. cv. Bu´lida) orchard with different soil tillage practices, in a loamy textured soil with a 7% slope, located in Murcia (SE Spain). Three treatments were applied between tree rows: control (no-tillage), whereby, following the common practice in the area, weeds were cut back to ground level by a blade attached to a tractor; perforated treatment, where the soil surface was mechanically perforated with an adaptedplough; and mini-catchment treatment, consisting of mini-catchments with low banks manually raised perpendicular to the line of emitters. Almost all of the apricot root system was located in the first 0.75 m of soil depth, with 91% in the first 0.50 m. More than 75% of the roots corresponded to thin roots, with a diameter less than 0.2 mm. Both tillage treatments decreased runoff compared with the control treatment, while the mini-catchment treatment showed the highest change in soil water content after rainfall events. The mini-catchment treatment was performed in an attempt to reduce the rainwater running down the slope, leaving the accumulated water near plant roots, an effect which was responsible for the higher root length density (RLD) values found in this treatment. In addition, roots were distributed over a wider area, providing higher RLD values up to 1 m from the emitter, meaning that a higher soil volume was explored. For these reasons, the mini-catchment treatment was seen to be the most beneficial soil tillage treatment for optimising water use in semiarid conditions.

The effect of different irrigation strategies in water relations, vegetative growth and yield of early maturing peach trees, growing in Murcia, (Spain) was studied during two years. Treatments consisted on: a control T1, full irrigated (150% of ETc); T2, continuous deficit irrigation at 50% of ETc; T3, regulated deficit irrigation (RDI), irrigated at 100% of ETc only during stage III of fruit growth and 25% the rest of the growing season; and T4, with automatic control of irrigation based on capacitance FDR-type probe data, varying threshold values. The results indicated that irrigation deficits in T2 and T3 treatments induced the lowest soil water content and stem water potential (Ψ stem ) values during the postharvest period (e.g. ψ stem up to -1.8 MPa in T3 during summer 2008); thus, a reduction in trunk growth and pruning weight, respect to control treatment values, was noted in both years. Also, peach yield was significantly reduced in both deficit irrigated treatments. The greatest irrigation water saving in T3 treatment (≈60%) caused the higher water use efficiency values in this treatment. For these reasons, water deficit during the postharvest periods (extended in the early maturing varieties) must be limited if fruit yield is not to be reduced. Irrigation scheduling based on capacitance probes have become a useful tool in the control of soil water content. When threshold values were precisely defined, the slight water deficits limited only vegetative growth while maintaining similar peach yield to that of well irrigated trees.Additional key words: automatic irrigation; capacitance probes; neutron probe; soil water content; stem water potential; vegetative growth; yield. Resumen Respuesta del melocotonero extra-temprano al riego deficitarioSe estudió el efecto de distintas estrategias de riego deficitario en las relaciones hídricas, crecimiento vegetativo y producción de melocotoneros extratempranos 'Flordastar' en Murcia (España) durante dos años. Los tratamientos fueron: T1, control, riego diario al 150% ETc; T2, riego deficitario continuo (50% ETc); T3, riego deficitario controlado (100% ETc sólo durante la fase III de crecimiento del fruto y 25% ETc el resto del ciclo) y T4, control automáti-co del riego basado diferentes umbrales de contenido hídrico del suelo con sondas de capacitancia. El déficit hídrico en los tratamientos T2 y T3 indujo los valores más bajos de contenido de agua del suelo y de potencial hídrico de tallo (Ψ tallo ) durante la poscosecha (Ψ tallo = -1,8 MPa en T3, verano 2008); lo que provocó una reducción del crecimiento del tronco y peso de poda, respecto a los valores del tratamiento control, en los dos años. Además, la producción se redujo significativamente en ambos tratamientos. El tratamiento T3 resultó ser el más eficiente en el uso del agua debido al mayor ahorro de agua de riego (≈60%). Por estas razones, los déficits hídricos en poscosecha (muy larga en variedades tempranas) deben ser limitados si no se quiere afectar la producción. Las sondas de capacitancia s...