Browsing by Author "Silva, Jorge R."
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- Effects of partial root-zone drying irrigation on cluster microclimate and fruit composition of field-grown Castelão grapevinesPublication . Santos, Tiago P.; Lopes, Carlos Manuel Antunes; Rodrigues, M. Lucília; Souza, Cláudia R. de; Silva, Jorge R.; Maroco, João; Pereira, João Santos; Chaves, Maria ManuelaThe partial root-zone drying (PRD) irrigation technique has been proposed for viticulture as a possible way to save water without compromising yield. Half of the plant root system is slowly dehydrating whereas the other half is irrigated; after about two weeks the opposite side of vines is irrigated. A PRD irrigation system (50 % of the crop evapotranspiration - ETc) was installed in a vineyard (Vitis vinifera L. cv. Castelão) in Southern Portugal and compared with two other irrigation systems, deficit irrigation, DI (50 % ETc) and full irrigation, FI (100 % ETc), as well as with non-irrigated vines (NI). Water was applied twice a week, from fruit set (mid-June) until one week before harvest (September 3). While FI vines remained well watered during the ripening period, a severe water stress developed in NI plants. PRD and DI vines exhibited mild water deficits during the same period. A significant decrease in vegetative growth (shoot weight, pruning weight, leaf layer number and percentage of water shoots) was observed in NI and PRD vines when compared to DI and FI. In denser canopies (FI and DI) berry temperature was always lower than that of the more open ones (NI and PRD). The higher degree of cluster exposition in PRD and NI had a positive influence on berry composition due to temperature and incident radiation, leading to higher concentrations of anthocyanins and total phenols in the berry skin compared to DI and FI vines. Irrigation did not significantly affect berry sugar accumulation and pH in berries. Compared to FI, PRD and DI treatments water use efficiency (the amount of fruit produced per unit of water applied) was doubled since at the same yield the amount of water applied, was reduced by 50 %.
- Partial rootzone drying: effects on growth and fruit quality of field-grown grapevines (Vitis vinifera)Publication . Santos, Tiago P.; Lopes, Carlos Manuel Antunes; Rodrigues, M. Lucília; Souza, Cláudia R. de; Maroco, João; Pereira, João Santos; Silva, Jorge R.; Chaves, Maria ManuelaA study to assess the effects of the Partial Rootzone Drying (PRD) irrigation strategy in comparison to other irrigation systems was carried out in southern Portugal in two field-grown grapevines varieties, Moscatel and Castelão. We addressed the question of whether by regulating growth and plant water use, the PRD system would enable an equilibrated vegetative development, leading to a favourable capture of solar radiation for photoassimilate production and, at the same time to provide an optimum environment for fruit maturation. Three irrigation schemes were applied in addition to the non-irrigated (NI) vines: partial root drying (PRD), 50% of crop evapotranspiration (ETc), supplied to only one side of the root system while the other one was allowed to dry, alternating sides every 15 days; deficit irrigated (DI), 50% ETc supplied, half to each side of the root system and full irrigated (FI, 100% ETc). During the whole season FI plants of both varieties exhibited a high leaf predawn water potential (ψpd , ca –0.2 MPa) while a progressive decline was observed in NI plants, reaching ψpd values near –0.7 MPa at the end of August. PRD and DI presented intermediate values. PRD vines exhibited a stronger control over vegetative growth as compared with DI and FI plants. This was expressed by lower values of total leaf area at harvest, leaf layer number, canopy wideness and water shoots number, allowing a higher light interception at the cluster zone that induced an improvement in some berry quality characteristics. Watering had no significant effects on sugar accumulation in the berries but led to a favourable increase in the must titratable acidity, mainly in Castelão. Whereas in DI and FI treatments berry skin anthocyanins and phenols content were always lower than in NI, in PRD there was either no reduction or the reduction was much lower than in the other irrigation treatments. Water use efficiency (WUE) was increased by about 80% in PRD and DI when compared with FI, as a result of almost similar yields in the three treatments. Yield gains of irrigated plants in relation to NI were modest, explained by the rainy spring in both years.