Physiological changes induced by either pre- or post-veraison deficit irrigation in 'Merlot' vines grafted on two different rootstocks

Population growth, economic development, environmental demands, and climate change converge into a scenario of water scarcity worldwide (Fereres and Gonzalez-Dugo 2009). Water supply may therefore constraint grape production for quality wine. In this context, deficit irrigation (DI) strategies to stabilize yield and maintain or improve wine quality are critical. Recently, the use of regulated deficit irrigation (RDI) has expanded in vineyards to improve (sometimes to reduce) water application, yield per unit water supply, berry composition, and wine quality. The objective of RDI is to apply water deficits of predetermined levels during certain phenological stages when their effects on fruit growth and quality are neutral or positive, while keeping vineyard vigor in balance with potential production (Girona et al. 2006, 2009; Pellegrino et al. 2006; Greven et al. 2005). The short and long-term impact of deficit irrigation on production and quality vary with vineyard conditions, namely soil texture and depth, variety, atmospheric environment, and viticultural practices. These factors make it difficult to predict the best timing for imposing water deficits. Also, the desired intensity of deficit is not easy to impose uniformly over the whole vineyard, and the risks of excessive water deficits must be avoided through careful monitoring. Furthermore, there is a trade-off between regulated water deficit to improve yield per unit water supply and the need to maintain well-watered vines to reduce heat damage in warm and hot regions (Sadras and Soar 2009; Soar et al. 2009). Understanding the effects of timing and amount of irrigation on yield and berry composition is key to achieve the desired yield and berry quality. Thus, the correct determination of vineyard water requirements (or evapotranspiration, ET) and the monitoring of soil and vine water status are critical to apply the appropriate deficit irrigation strategies. The conventional crop coefficient (Kc) approach provides a simple and convenient way to estimate vineyard water requirements for a variety of soil and climatic conditions, but a major uncertainty in this approach is that the empirical nature of Kc which requires local calibration and monitoring of plant water status. Vine water status can be monitored with predawn, noon leaf, and stem water potentials, which integrate the effects of soil water status on both the environment (soil and atmosphere) and the vine (root and canopy size, stomatal conductance). However, there is no general agreement on which method is the most reliable to evaluate vine water status. This discrepancy may be explained by the combined effect of variety and rootstock, soil type and depth, range of soil water deficit, variability of weather conditions throughout the growing cycle, atmospheric evaporative demand, and source/sink ratio as affected by growing conditions and management practices shifting the balance between leaf area and fruit load. Midday stem water potential of horticultural trees, for example, is lower with high source/sink ratio (Sadras and Trentacoste 2011). Communicated by R. Evans.

Regulated deficit irrigation effects on growth, yield, grape quality and individual anthocyanin composition in Vitis vinifera L. cv. ‘Tempranillo’

Soil water deficit and salinity represent a major factor impacting plant survival and agricultural production. The frequency and severity of both abiotic stresses are expected to increase in a context of climate change, especially in arid and semi-arid regions. This work studied the growth pattern, biomass and mineral distribution and the seasonal pattern of water status, photosynthetic rate and stomatal conductance in plant of Pistacia lentiscus grown under different levels of water deficit and salinity. P. lentiscus plants growing under greenhouse conditions were subjected to four irrigation treatments during 11 months: control (C, 1 dS m-1), moderate water deficit (MW, 1dS m-1, 60% of the control), severe water deficit (SW, 1 dS m-1, 40% of the control) and saline (S, 4dS m-1). The results show that Pistacia lentiscus plants were more affected by deficit irrigation than salinity. Deficit irrigation and salinity inhibited plant height, with reductions of 20%, 22% and 35% for S, MW and SW, respectively. Total leaf area was not modified by effect of the treatments, with the result that plant compactness increased in MW. The salt stressed plants only showed lower relative growth rate at the end of the experiment. Plants responded to saline or drought stress by increasing their osmotic adjustment, which was more pronounced under salinity. Saline plants had the highest values in Na+ and Cl- ions and the lowest values for K+/Na+ and Ca2+/Na+ ratios in leaves and stems, which is correlated with a decrease in growth, stomatal conductance, photosynthesis and stem water potential, and can be used as a diagnostic tool to assess plant tolerance to salinity stress. As a measure of plant hydration, relative water content was more sensitive to deficit irrigation than salinity, being a good indicator of water stress. P. lentiscus plants subjected to both deficit irrigation treatments exhibited an increase in their intrinsic water use efficiency, which is an important adaptation for plants growing in environments with water scarcity.

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(Ψstem) values during the postharvest period (e.g. ψstem 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.

Deficit irrigation limits almond trees’ photosynthetic productivity and compromises yields

Drought and mandatory water restrictions are limiting the availability of irrigation water in many important blueberry growing regions, such as Oregon, Washington, and California. New strategies are needed to maintain yield and fruit quality with less water. To address the issue, three potential options for reducing water use, including deficit irrigation, irrigation cutoffs, and crop thinning, were evaluated for 2 years in a mature planting of northern highbush blueberry ( Vaccinium corymbosum L. ‘Elliott’). Treatments consisted of no thinning and 50% crop removal in combination with either full irrigation at 100% of estimated crop evapotranspiration (ET c ), deficit irrigation at 50% ET c (applied for the entire growing season), or full irrigation with irrigation cutoff for 4–6 weeks during early (early- to late-green fruit) or late (fruit coloring to harvest) stages of fruit development. Stem water potential was similar with full and deficit irrigation but, regardless of crop thinning, declined by 0.5–0.6 MPa when irrigation was cutoff early and by >2.0 MPa when irrigation was cutoff late. In one or both years, the fruiting season was advanced with either deficit irrigation or late cutoff, whereas cutting off irrigation early delayed the season. Yield was unaffected by deficit irrigation in plants with a full crop load but was reduced by an average of 35% when irrigation was cutoff late each year. Cutting off irrigation early likewise reduced yield, but only in the 2nd year when the plants were not thinned; however, early cutoff also reduced fruit soluble solids and berry weight by 7% to 24% compared with full irrigation. Cutting off irrigation late produced the smallest and firmest fruit with the highest soluble solids and total acidity among the treatments, as well as the slowest rate of fruit loss in cold storage. Deficit irrigation had the least effect on fruit quality and, based on these results, appears to be the most viable option for maintaining yield with less water in northern highbush blueberry. Relative to full irrigation, the practice reduced water use by 2.5 ML·ha −1 per season.

Water relations in vineyards have been largely studied; giving insides regarding the way grapevine interacts with its environment according to water availability, providing us terminologies like Isohydric and Anisohydric, which have been applied to categorize cultivars and rootstocks. Recently, the use of this terminology has been subjected to discussion regarding its use as a category to describe and separate grapevine cultivars instead of using it as a continuous, where grapevines can behave more iso or anysohidric depending on the environment where they are grown. In this study, using a deficit irrigation (RDI) trial in a commercial vineyard located in Maule Valley in Central Chile, the relationship between Midday Stem Water Potential (ψx), Stomatal Conductance (gs), Soil Water Content (WC), and Vapour Pressure Deficit (VPD) on cv. Cabernet Sauvignon was studied, a grape variety that has been classified as isohydric. The trial was carried out for 3 years from 2018 to 2020 in which four RDI treatments were employed to replenish different portions of evapotranspiration (ET) from pea-size until harvest. These irrigation treatments were conceived as 100% ET, 70% ET, 50-100% ET (50% ET before veraison and 100% ET afterwards) and 35-100% ET (35% ET before veraison and 100% ET afterwards). Findings in this study show how the relationship between ψx and gs is treatment dependent; in treatments where no water deficit was imposed a weaker relationship between the variables was observed, showing a large variation between gs at similar ψx, being gs more dependent on VPD compared to the treatments with a larger deficit on its irrigation. As the deficit irrigation increased, grapevines started to shift to a smaller variation on its gs over large variations on its ψx. This result shows that irrigation management and deficit irrigation strategies impact the way plants react to water availability and leads to different behavior on its gs/ψx relationship.

There is an increased demand for high quality winegrapes in the São Francisco Valley, a new wine producing area in Brazil. As the grape quality is closely linked to the soil water status, understanding the effects of rootstock and irrigation management on grapevine water relations is essential to optimize yield and quality. This study was carried out to investigate the effects of irrigation strategies and rootstocks on water relations and scion vigour of field-grown grapevines in Petrolina, Pernambuco state, Brazil. The cultivars used as scions are Moscato Canelli and Syrah, both grafted onto IAC 572 and 1103 Paulsen rootstocks. The following water treatments were used: deficit irrigation, with holding water after veraison; and partial root-zone drying, supplying (100% of crop evapotranspiration) of the water loss to only one side of the root system after fruit set, alternating the sides periodically (about 24 days). In general, all treatments had values of pre-dawn leaf water potential higher than -0.2 MPa, suggesting absence of water stress. The vine water status was more affected by rootstock type than irrigation strategies. Both cultivars grafted on IAC 572 had the highest values of midday leaf water potential and stem water potential, measured on non-transpiring leaves, which were bagged with both plastic sheet and aluminum foil at least 1 h before measurements. For both cultivars, the stomatal conductance (g s), transpiration (E) and leaf area index (LAI) were also more affected by roostsotck type than by irrigation strategies. The IAC 572 rootstock presented higher g s, E and LAI than the 1103 Paulsen. Differences in vegetative vigor of the scion grafted onto IAC 572 rootstocks were related to its higher leaf specific hydraulic conductance and deeper root system as compared to the 1103 Paulsen, which increased the water-extraction capability, resulting in a better vine water status.

We measured the effects of planting density (238, 317 and 476 trees ha−1), irrigation (fully irrigated control vs. deficit irrigation) and their interaction on the vegetative growth, yield and irrigation water use efficiency (IWUE) of young olive trees during three seasons. In the water deficit treatment, irrigation was applied when midday stem water potential (SWP) dropped below −2.5 MPa; SWP of controls was maintained between −1.2 and −1.5 MPa. Across irrigation treatments, oil yield at high density (968 kg ha−1) was 70 % higher than at low density. Reduction in oil yield due to deficit irrigation was not significant compared to control (501 vs. 664 kg ha−1). IWUE at lower tree density averaged 1.5 kg ha−1 mm−1, increased by 50 % in intermediate density and by 57 % at the highest density. Deficit irrigation increased IWUE twofold with respect to controls. IWUE responded to the interaction density × irrigation whereby the highest IWUE (4.6 kg ha−1 mm−1) was obtained at highest density and deficit irrigation. IWUE was nonlinearly related to seasonal water stress integral ( $$S\psi$$ ), where maximum efficiency corresponded to 180 MPa days. The negative correlation between fruit water concentration and $$S\psi$$ highlights the potential benefit of deficit irrigation of increasing oil extractability. The positive outcomes of increasing the density (higher oil yield) and deficit irrigation (higher IWUE, lower water concentration in fruit) need to be weighed against the long-term effect on vegetative growth. Under our conditions, three seasons of water deficit reduced crown and trunk size by 35 % in relation to fully irrigated.

A standard fruit growth curve, used commercially as an aid to hand thinning, was compared to periodic volume measurements of apple fruit ( Malus domestica Borkh. `Delicious') subjected to early season regulated deficit irrigation (RDI) to determine when to end RDI, which is used to control vegetative growth and save water. RDI suppressed stem water potential, stomatal conductance, and fruit growth rate compared to the trickle- and furrow-irrigated controls, which wetted about one-half and the entire soil volume, respectively. Full irrigation was restored to RDI trees by trickle and microsprinklers, which wetted about one-half and the entire soil volume, respectively, after terminal buds set. Stem water potential, stomatal conductance, and fruit growth rate of RDI trees increased to that of the controls, except for RDI/trickle trees, which had 80% the stomatal conductance of the other treatments. Fruit weight at harvest was affected by an interaction of irrigation treatment and cropload. RDI trees had similar or less vegetative growth and similar or higher yield efficiency than the controls. We recommend ending RDI before fruit growth declines below the standard curve.

Irrigation techniques that reduce water applications are increasingly applied in areas with scarce water resources. In this study, the effect of two regulated deficit irrigation (RDI) strategies on peach [Prunus persica (L.) Batsch cv. “Catherine”] performance was studied over three growing seasons. The experimental site was located in Murcia (SE Spain), a Mediterranean region. Two RDI strategies (restricting water applications at stage II of fruit development and postharvest) based on stem water potential (Ψs) thresholds (−1.5 and −1.8 MPa during fruit growth and −1.5 and −2.0 MPa during postharvest) were compared to a fully irrigated control. Soil water content (θv), Ψs, gas exchange parameters, vegetative growth, crop load, yield and fruit quality were determined. RDI treatments showed significantly lower values of θv and Ψs than control trees when irrigation water was restricted, causing reductions in stomatal conductance and photosynthesis rates. Vegetative growth was reduced by RDI, as lower shoot lengths and pruning weights were observed under those treatments when compared to control. However, fruit size and yield were unaffected, and fruit quality was slightly improved by RDI. Water savings from 43 to 65 % were achieved depending on the year and the RDI strategy, and no negative carryover effect was detected during the study period. In conclusion, RDI strategies using Ψs thresholds for scheduling irrigation in mid–late maturing peach trees under Mediterranean conditions are viable options to save water without compromising yield and even improving fruit quality.

Effects of arbuscular mycorrhizae on tomato yield, nutrient uptake, water relations, and soil carbon dynamics under deficit irrigation in field conditions

Effects of timing and intensity of deficit irrigation on vegetative and fruit growth of apricot trees

<p style="text-align: justify;"><strong>Aims</strong>: The impact of water deficit stress on vine shoot growth, berry weight, grape composition and overall vintage quality was investigated in Bordeaux vineyards. Methods for assessing water deficit stress were compared.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Vine water status was assessed on three soil types during four vintages by means of stem water potential and carbon isotope discrimination measured on grape sugar. Regional water deficit was compared for a range of over 30 vintages by means of water balance modelling. It was shown that water deficit stress anticipated shoot growth slackening, limited berry weight and enhanced berry anthocyanin content. Berry sugar content was greatest when water deficit was mild. It was shown that stem water potential measurements and carbon isotope discrimination are accurate tools for assessing vine water status at plot scale. Seasonal water deficit at a regional scale can be correctly estimated by water balance models. Vintage quality in Bordeaux is determined by the intensity of water deficit stress rather than by the level of the temperatures.</p><p style="text-align: justify;"><strong>Conclusions</strong>: Vine phenology and grape ripening are highly dependent on water uptake conditions. Mild water deficit stress enhances grape quality for the production of red wines. Vine water status can accurately be assessed by means of stem water potential or carbon isotope discrimination measured on grape sugars. Quality losses through severe water stress can be avoided through the use of drought-adapted plant material, appropriate canopy management, yield reduction or the implementation of deficit irrigation.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This study shows the key role of water deficits in the production of quality grapes for red wine production. Methods for assessing vine water status are compared and discussed. Among many existing methods, the accuracy of stem water potential, carbon isotope discrimination measured on grape sugar and water balance modelling are emphasized.</p>

Water relations, biochemical – physiological and yield responses of olive trees (Olea europaea L. cvs. Arbequina and Manzanilla) under drought stress during the pre-flowering and flowering period