Partial rootzone drying: effects on growth and fruit quality of field-grown grapevines (Vitis vinifera)

Abstract

Abstract. A 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 (ψ pd , ca -0.2 MPa) while a progressive decline was observed in NI plants, reaching ψ pd 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.

Partial rootzone drying: regulation of stomatal aperture and carbon assimilation in field-grown grapevines (Vitis vinifera cv. Moscatel)

“…Drought can cause a decline of TPU due to diminished supply of inorganic phosphate to the Calvin cycle, consistent with a slow-down in growth generally observed in drought-stressed plants (Chaves 1991). Statistically significant growth inhibition was indeed observed in NI and PRD vines (see dos Santos et al 2003). Although no Pre-dawn leaf water potential (MPa) significant differences were found between irrigated treatments, PRD and NI vines showed an increase of RSL of photosynthesis, indicating that stomatal conductance was more reduced than in DI and FI vines.…”

“…While the benefits of PRD relative to NI (increased CO 2 assimilation) and to FI (increased water use efficiency) were obvious, from a strictly physiological point of view differences between the PRD and DI treatments were subtle. Nevertheless, vegetative growth, as measured by leaf area and pruning weight, was significantly affected as described in a companion study (dos Santos et al 2003). Whether this is sufficient to recommend this practice at the commercial level, at least under conditions of moderate drought as those prevailing in this experiment, will depend on the integrated effects on vegetative growth (with impact on microclimate) and fruit quality.…”

Effects of partial rootzone drying and rootstock vigour on growth and fruit quality of 'Pink Lady' apple trees in Mediterranean environments

“…In DI trees, vegetative growth reductions may also be explained by the higher number of fruits and crop load determining stronger competition among sinks for assimilates and water. Vegetative growth reductions, mainly in terms of reduced shoot length, were also reported in raspberry (Grant et al 2004), grapes (Dry and Loveys 1999;Dry et al 2000;Santos et al 2003), olive (Wahbi et al 2005), and potted apple (Gowing et al 1990), while trials conducted on field-grown apple trees indicated variable responses depending on irrigation volumes (O'Connell and Goodwin 2007), or no shoot growth reduction in response to PRD (Einhorn and Caspari 2004;Lombardini et al 2004). Discrepancies between the two trials of this study and with previous field trials could be attributable to some differences in crop load and associated degree of g s reduction in response to PRD irrigation.…”

Improving water use efficiency of vineyards in semi-arid regions. A review

“…Root growth rates under partial root zone drying conditions can change the proportion of roots in a drying soil having implications for abscisic acid synthesis, water extraction, and also nutrient uptake. Partial root zone drying induces also lower canopy leaf area and consequently lowering water use Davies et al 2002;Kang and Zhang 2004;Santos et al 2003;Stoll et al 2000). These physiological changes observed in partial root zone drying are not always found in all field experiments (Bravdo 2004;Dry et al 2000a, b;Gu et al 2004;Intrigliolo and Castel 2009;Marsal et al 2008).…”