Regulated deficit irrigation effects on yield, fruit quality and vegetative growth of ‘Navelina’ citrus trees

Abstract

An experiment on regulated deficit irrigation (RDI) was performed during two growing seasons (2007 and 2008) in a drip-irrigated orchard of Navelina/Cleopatra in Senyera (Valencia, Spain). Two RDI treatments, where water application was reduced to 40% and 60% of the «irrigation dose» (ID), were carried out during the initial fruit enlargement phase (Stage II, 17 th July to 2 nd September). The rest of the year they were irrigated at 110% ID. These treatments were compared with a control, where irrigation was applied without restriction during the whole year at 110% ID. The ID was obtained from the evapotranspiration data, as well as from the characteristic variables of drip irrigation for the specific experimental orchard. The effects of the treatments on yield, fruit quality, and vegetative growth are discussed in relation to tree water status (midday stem water potential, Ψ st ). Minimal Ψ st values reached in the treatment with the highest stress intensity were -1.71 and -1.60 MPa in 2007 and 2008 respectively. These Ψ st values reached as a consequence of the water reduction in the RDI summer treatments applied in this study did not affect yield or fruit quality, allowing water savings between 16% and 23%. In conclusion, water restriction during summer, and once «June drop» has finished, favours the better use of water resources by Navelina citrus trees, achieving an increase of water use efficiency (between 14% and 27% in this case), provided that an appropriate irrigation in autumn allows for tree recovery.Additional key words: citrus trees; drip irrigation; Navelina; stem water potential; water relations; water use efficiency. ResumenEfectos del riego deficitario controlado sobre el crecimiento, producción y calidad de la fruta en cítricos de la variedad Navelina Se ha realizado un experimento de riego deficitario controlado (RDC) durante 2007 y 2008 en una parcela de Navelina/Cleopatra regada por goteo en Senyera (Valencia, España). Se aplicaron dos tratamientos RDC al 40 y 60% de la dosis de riego (ID) durante el periodo de crecimiento inicial del fruto (Fase II, 17/07 al 02/09). El resto del año se regaron al 110% de la ID. Estos tratamientos se compararon con un control, regado todo el año al 110% de la Dr, determinada a partir de la evapotranspiración, así como de los parámetros característicos del riego por goteo de la parcela de ensayo. Los efectos de los tratamientos sobre la producción y calidad de la cosecha, así como sobre el crecimiento vegetativo, se discuten en relación al estrés hídrico producido (potencial del tallo al mediodía solar, Ψ st ). Los valores mínimos de Ψ st alcanzados por el tratamiento más estresado fueron de -1.71 y -1.60 MPa en 2007 y 2008 respectivamente. Estos valores de Ψ st alcanzados como consecuencia de la reducción del riego en los tratamientos RDC en verano aplicados en este trabajo, no produjeron mermas en la producción ni en la calidad de la cosecha, permitiendo ahorros de agua entre el 16 y el 23%. Se concluye que la reducción del riego en verano, tra...

Monitoring water stress and fruit quality in an orange orchard under regulated deficit irrigation using narrow-band structural and physiological remote sensing indices

“…The relationship found between the photochemical reflectance indices and fruit quality in September can be explained by the fact that this period is not only the time of the most severe water stress levels, but also is a critical time in terms of the physiological stage of fruit growth in citrus. Previous experiments on 'Clementina de Nules' and 'Navelina' citrus trees (Gasque et al, 2010;Castel, 1999, 2000) have shown that the effects of RDI treatments depend on the phenological period in which the water restriction is applied. During period II, summer (initial fruit enlargement), the application of RDI did not affect yield or fruit quality, whereas during period III (end of summer-autumn) it resulted in a decrease in yield, fruit size and fruit quality parameters due to a slower growth rate in the final stages of crop development.…”

Assessment of Agricultural Options Available for Saving Orange Cultivation in Ribera Baixa (Valencia, Spain)

“…In contrast, in Ribera Alta, groundwater and/or well water is pumped to irrigate the fields. The practice of deficit irrigation (Gasque et al, 2010;Ruiz Sanchez et al, 2010) is being promoted as a good water conservation practice. The last potential under-utilized water supply is recycling treated wastewater at least for irrigation purposes (Alcon et al, 2010).…”

Machine learning applied to the prediction of citrus production

“…This can be deduced from the value of the corresponding coefficient in regression tree and from the fact that 76% of orchards in this group are irrigated. On the other hand, L1 and L2 orchards (< 25%) indicated that this practice is necessary and improves yield, according to Agustí (2000Agustí ( , 2003, González-Altozano & Castel (2003), García Petello & Castel (2004), and Gasque et al (2010).…”

“…When lower values or dry seasons occur, complementary irrigation is needed (Agustí, 2000(Agustí, , 2003. Irrigation absence mainly affects the fruit size, although the effect of this absence also depends on the phenological state (González-Altozano & Castel, 2003;García Petello & Castel, 2004;Gasque et al, 2010).…”