Models relying on limited inputs are very valuable for estimating reference evapotranspiration, and subsequently irrigation doses, but their accuracy can be very dependent from calibration. This study assessed three versions of the Hargreaves-Samani (HS) and the FAO Penman-Monteith (PM) equations to estimate reference evapotranspiration (ETo), relying respectively on three input combinations. Further the six models were adjusted each using different time windows for calculating the calibrating constants, namely global, annual, monthly, fortnightly, and weekly constants, while all the models were calibrated and tested using calculated and lysimeter benchmarks. The models relying on mean air temperature and solar radiation tended to be more accurate than those relying on mean air temperature and relative humidity, while these tended to be more accurate than those relying on air temperature difference, but there might be intra annual exceptions according to the monthly indicators. The errors of the PM estimations were just slightly higher than those of the corresponding HS estimations. The accuracy improvement in the calibrated versions was higher the shorter the time window used for averaging the calibrating parameters. Thus, the application of monthly or, at least, seasonal calibrating constant might be recommended for a suitable correction of the bias. During the year, the estimations presented markedly lower errors and lower differences within models during the summer. The error decrease in the calibrated versions was more marked during the winter. The assessment relying on lysimeter benchmarks provided similar qualitative patterns than the assessment relying on calculated benchmarks, but the corresponding error ranges were higher. Finally, 6 examples were presented for visualizing the effect of the method used to estimate ETo on the corresponding resulting average annual crop water requirements. If irrigation scheduling is based on a soil water balance using crop evapotranspiration estimates, at least, a monthly bias assessment of the ETo estimates in combination with the crop cycle lengths and dates might contribute to infer if crop water requirement infra-estimation trends are identified during crop sensitive stages to water deficit.

BACKGROUND: Climate change modifies the content and phenolic profiles of grapes and wines. It is known that high temperatures, related to climate change, reduce anthocyanins and procyanidin (catechin and tannin) compounds accumulated in the berries. In recent years, with the aim of improving the phenolic composition of the berries, the technique of crop forcing has been proposed to delay grape ripening to a more favourable period of temperatures. RESULTS: In this study, crop forcing was applied to cv. Tempranillo vines on two different dates, after flowering (F1) and after fruit set (F2), and compared to a treatment control (NF, without forcing). Additionally, as a secondary factor, two irrigation strategies were established in each treatment: irrigation with no water stress, and a preveraison deficit irrigation. The study was carried out in three consecutive years (2017-2019). For most of the parameters analysed, no interaction was found. Therefore, for these parameters, the effect of each of these techniques was investigated independently. Regardless of the irrigation strategy, F2 berries achieved higher contents of catechins and anthocyanins than NF berries. Each year, regardless of the irrigation strategy, crop forcing increased the content of monoglucoside forms, and had a positive effect on the total content of malvidin, petunidin, delphinidin, peonidin and malvidin derivatives, but only affected acetyl and coumaryl forms in 2017. However, the effect of irrigation strategy was less significant and consistent, being more dependent on the vintage. CONCLUSION: Regardless of vine water status, crop forcing technique applied after fruit set could be used by vine growers to delay ripening of the grapes and thus achieve an increase in the anthocyanin characteristics of the grapes. (C) 2023 Society of Chemical Industry.

In Mediterranean vineyards, high temperatures and scarce water resources affect the quantity and quality of harvests. Crop forcing (F) is a novel approach that consists of inducing the bud burst of buds developed during the current season in order to modify the phenology of the vine and shift berry ripening to a period of moderate temperatures. The aim of this work is to evaluate the effect of F on cv. Tempranillo grapes in the semi-arid conditions of Extremadura (Spain) under different water regimes. A field experiment was carried out from 2017 to 2019 in a vineyard of cv. Tempranillo with three pruning treatments: winter pruning only (NF) and two F treatments, in which, in addition to winter pruning, forced pruning was carried out at two different phenological stages, after flowering (F1) and after fruit set (F2). These treatments were subjected to two watering regimes: irrigation covering the vines' water requirements (I) and deficit irrigation (DI) with moderate water stress during the preharvest period. The average delay in harvest of the F treatments compared to NF was 32 and 56 days in F1 and F2, respectively, with a decrease in the average temperature during ripening (veraison to harvest). Yield was lower in F1 and F2 than in NF regardless of water regime, although yield levels were more stable between seasons in these treatments. Titratable acidity, malic acid content, total polyphenol content and total anthocyanin content increased in the F treatments, and the combined application of F and DI improved grape composition but also resulted in a higher yield penalty.

“Crop-forcing” is an effective technique to delay grape maturation to a period of lower temperatures, and in this way, improve grape quality. Because of the aggressiveness of this technique (removal of leaves and fruit to reinitiate a second vegetative cycle), it may affect the level of reserves and could provoke progressive vine exhaustion. The aim of the present work is to evaluate the short- and medium-term evolution of carbohydrate reserves in different plant organs and the effect of “crop-forcing” under different irrigation regimes on seasonal biomass production and its distribution. The study was carried out over a four years period (2017–2020), applying “crop-forcing” in three consecutive years (2017–2019) to the same vines on two different dates and using two irrigation strategies. The application of “crop-forcing” did not decrease root reserve levels in either the year of application or the following year, but did modify starch and soluble sugar levels in shoots and leaves in some moments of the vegetative cycle during the years of “crop-forcing” application. Total biomass production in terms of grams per vine was lower in the “crop-forcing” treatments and continued to be so when “crop-forcing” was no longer applied. The percentage of biomass in vegetative organs increased at the expense of productive organs.

Background and Aims . High temperatures during grape ripening have a negative effect on the winemaking characteristics of musts. The crop forcing technique delays ripening to a period when temperatures are lower. The objective of this study is to provide information to winemakers and grape growers on how the delay in ripening caused by crop forcing can affect berry performance. Methods and Results. This study of 3 growing seasons (2017–2019) analyzes the effect of this technique in a vineyard of the Vitis vinifera L. cv. Tempranillo in Extremadura, together with two irrigation strategies. The grapevines were forced 4 and 22 days after anthesis ( F 1 and F 2, respectively), compared to a treatment without crop forcing techniques (NF). Each treatment was subjected to two irrigation strategies: to cover the water needs of the plants (C) and deficit irrigation during preveraison (RI). Crop forcing delayed the harvest between 32 and 56 days on average in relation to NF. Crop forcing and irrigation strategy modified berry composition at harvest: C- F 1 and C- F 2 had higher total polyphenol and anthocyanin concentrations, total acidity, malic acid content, and lower pH relative to C-NF; RI-NF increased total anthocyanin concentration and pH and decreased titratable acidity value. Conclusions. Crop forcing is able to delay grape ripening to lower temperature periods. This is a promising technique for restoring the coupling between phenolic and technological ripeness. The combination of both crop forcing and deficit irrigation strategy maintains the berry quality while improving water use efficiency. Significance of the Study. The present work shows how the “crop-forcing” technique is effective in modifying the relationship between different parameters that determine the characteristics of berries throughout ripening as a raw material for winemaking, compared to vines with traditional winter pruning, under different irrigation strategies. To the memory of Jordi Marsal

In recent years, there have been increasing efforts to link phenology models with seasonal climate predictions in so-called Decision Support Systems (DSS) to tailor crop management strategies. However, temporal discrepancies between phenology models with temperature data gathered on a daily basis and seasonal forecasting systems providing predictability on monthly scales have limited their use. In this work, we present a novel methodology to use monthly average temperature data in phenology models. Briefly stated, we modelled the timing of the appearance of specific grapevine phenological phases using monthly average temperatures. To do so, we computed the cumulative thermal time (Sf ) and the number of effective days per month (effd). The effd is the number of days in a month on which temperatures would be above the minimum value for development (Tb). The calculation of effd is obtained from a normal probability distribution function derived from historical weather records. We tested the methodology on four experimental plots located in different European countries with contrasting weather conditions and for four different grapevine cultivars. The root mean square deviation (RMSD) ranged from 4 to 7 days for all the phenological phases considered, at all the different sites, and for all the cultivars. Furthermore, the bias of observed vs predicted comparisons was not significantly different when using either monthly mean or daily temperature values to model phenology. This new methodology, therefore, provides an easy and robust way to incorporate monthly temperature data into grapevine phenology models.

This study aims to analyze the effects of non-limiting irrigation (I) vs. rainfed (R) through two different shoot densities, high-load (H) and low-load (L), on vegetative growth, agronomic parameters, flavonoid and non-flavonoid polyphenol substances of cv. Tempranillo grown in a semi-arid climate during three consecutive seasons (2014–2016). Under these conditions, in the 2015 and 2016 seasons, irrigation showed significant increases in berry weight (14.7% and 13.4% in H and L, respectively, in 2015, and 35.6% and 23.5% in the same treatments in 2016) and yield (66.7% and 48.5 in 2015; 27.9% and 177.5% in 2016). Additionally, a general decreasing trend is observed in anthocyanins with the exception of peonidin derivates, almost all flavonol compounds, cinnamic acid and resveratrol values with different degrees and statistical significance depending on the shoot density of the vines. A slight variation is observed in 2014 in these parameters. On the other hand, no general trends are established either in flavanol compounds or hydroxybenzoic acid. Thus, the effect of irrigation depends on the parameter considered, the shoot density of the vine and the season considered.

Wine phenolics are of considerable interest due to their implication in the organoleptic appreciation of wines and due to their bioactive functions as antioxidants. In this work, the effects of sustainable strategies in the vineyard, regulated deficit irrigation treatments (RDI) and crop load level (CL) on Tempranillo grape phenolics over two seasons was studied. Rainfed (T), early (EDI) and late (LDI) regulated deficit irrigation was applied. Cluster thinning (TH) and control (C) without cluster removal were also applied under each irrigation treatment. The effect of CL remained independent of RDI for all compounds, except for phenolic acids. The RDI influence on the grape skin phenolic profile was higher than CL in the dry season (2009); however, in 2010, the effect of CL was greater. In 2009, a tendency to increase anthocyanin and hydroxycinnamic acid content in grape skins was registered in EDI with respect to T. However, significant decreases in hydroxycinnamic and flavanol compounds were found in LDI. In 2010, the wettest year, CL increased all phenolic families’ content. Thus, it can be concluded that the effects of RDI and cluster thinning treatments depend on the family of compounds considered and the meteorological conditions of the year.

The efficient use of water in the vineyard requires knowledge of the crop's response to irrigation in terms of production and quality and the interaction of the same with the environmental conditions. In this work, the behavior of a trellis system vineyard in cv. Tempranillo, located in the south-west of Spain, was analyzed for three years in relation to different irrigation strategies based on crop evapotranspiration (ETc), and with two levels of crop load established by early cluster thinning. The response of the vineyard to the same irrigation strategy varied depending on the characteristics of the year. The vineyard's biomass production increased in a linear trend as annual water status improved. However, during pre-veraison, the water status had a more significant impact on the harvest by affecting bud fertility. The increase in individual cluster weight only partially compensated the loss of yield caused by cluster thinning. The year's characteristics highly conditioned the response to the irrigation treatment and, together with cluster thinning, modified the characteristics of the musts, although the response was varied.

Lysimeters are the reference method for determining ETc, but they are expensive and complex, which limits their use. The first objective of this work was to adjust and evaluate the robustness of sap flow sensors in order to determine the transpiration of a vineyard and, together with an evaporation model, to calculate the ETc of the vineyard. For this purpose, we compared water consumption data obtained from a vineyard weighing lysimeter (ETcLys) with the sum of transpiration obtained from sap flow sensors (TSF) and evaporation estimated empirically over four years (2012, 2013, 2014 and 2015). The second objective was to obtain the relationship between the vegetative growth and transpiration of the vines with different water availability (irrigation and rainfed treatments), as an alternative method for estimating vine water needs adjusted to their real development. The third and last objective was to evaluate the transpiration response of the vines when subjected to water stress. We carried out the work in an experimental vineyard which has a well-established weighing lysimeter. As a result, a good match was obtained between vine sap flow and transpiration (R2 = 0.85) as well as a good relationship between vegetative growth and vine transpiration (FiPAR: R2Irrigation = 0.34. R2Rainfed = 0.54; LAI: R2Irrigation = 0.68. R2Rainfed = 0.53).

Aim of study: The concentration of phenolics in the grape berries can be influenced by cultural practices such as irrigation or thinning. The main objective of the present study was to evaluate the effect of combinations of these practices on grape size and phenolics content. Area of study: The trial was carried out in an experimental cv. Tempranillo vineyard located in Extremadura, Spain. Material and methods: Two irrigation regimes were considered: rainfed vines (non-irrigated, NIr), and 100% ETc irrigated vines (Ir). For each irrigation treatment, two cropping levels were studied: low shoot-thinning (LT) vs high shoot-thinning (HT) implemented in winter and spring, respectively. Berry weight, and total phenolics, proanthocyanidin, and anthocyanin concentrations were determined at eight stages of berry development in three consecutive years (2014, 2015, and 2016). Main results: Specific weather conditions of each year affected phenolics accumulation differently. In 2014, where maximum temperatures were low and an important rainfall occurred at Stage II, both the NIr-LT and NIr-HT treatments led to the greatest concentrations of total phenolics, proanthocyanidins, and anthocyanins. In 2015, where a little rainfall was registered at Stage II, the berries from the NIr-HT and Ir-HT treatments accumulated the greatest total phenolics and proanthocyanidin contents, but the NIr-LT and NIr-HT treatments led to the greatest accumulation of anthocyanins. Finally, in 2016, where high maximum temperatures and scarce rainfall were registered, the Ir-LT and Ir-HT treatments presented the greatest concentrations of total phenolics, proanthocyanidins, and anthocyanins. Research highlights: A significant effect of irrigation and thinning was observed on berry size and phenolic content, as well as year × thinning interaction.

Phenolics are involved in many of plants’ biological functions. In particular, they play important roles in determining the quality of grape berries and the wine made from them, and can also act as antioxidants with beneficial effects for human health. Several enzymes are involved in the synthesis of phenolic compounds. Among them, stilbene synthase (STS) is a key to the biosynthesis of stilbenes, which are considered to be important secondary metabolites in plants. Other enzymes, such as polyphenol oxidase (PPO) and peroxidase (POD), are involved in the degradation of phenolics, and become activated during late stages of berry ripening. In the present study, Vitis vinifera L. berries were sampled at eight stages of development, from 10 days after anthesis to late harvest. The PPO and POD enzymatic activities were determined at each stage. The presence of STS, PPO, and POD proteins in the grape exocarp and mesocarp was detected immunohistochemically and histochemically. The amount and intensity of the immunohistochemical and histochemical signals correlate with the variations in enzyme activities throughout fruit development. Strong STS immunoreactivity was detected until the onset of ripening. Labeled tissue increased gradually from mesocarp to exocarp, showing an intense signal in epidermis. At subcellular level, STS was mainly detected in cytoplasm grains and cell walls. The amount of PPO immunoreactivity increased progressively until the end of ripening. The PPO signal was detected in hypodermal layers and, to a lesser extent, in mesocarp parenchyma cells, especially in cytoplasm grains and cell walls. Finally, POD activity was stronger at the onset of ripening, and the POD histochemical signal was mainly detected in the cell walls of both exocarp and mesocarp tissue.

Must nitrogen is very important for successful fermentation. Irrigation can influence vine nitrogen availability, and therefore must nitrogen content and wine quality. The aim of this work was to assess the effect of vine water status on the nitrogen concentration of cv. Tempranillo grown under semiarid conditions. A rainfed and two regulated deficit irrigation (RDI) strategies, late (LDI) and early deficit irrigation (EDI) were applied during pre- and post-veraison respectively periods over two seasons in Badajoz (Spain). Twenty-eight amino acids, amines and ammonia were determined by high performance liquid chromatography (HPLC) in the must. Results showed an effect of the pre-veraison vine water status on the must amino acid concentration. Higher values of nitrogenous indices were reached in musts from LDI treatments, mainly in the dry year. Significant correlations between pre-veraison stem water potential and 19 amino acid concentrations were observed. Therefore, LDI was a more suitable strategy for increasing the content of nitrogenous substances in the must.

5 paginas, 1 tabla y 1 figura.- Trabajo presentado en las III Jornadas del Grupo de Viticultura celebradas en Palma de Mallorca entre el 28 y el 29 de noviembre de 2018.

The work was carried out on Vitis vinifera, L. (cv. Macabeo) grafted onto 110 Ritcher rootstock and cultivated in two locations of the southern half of Spain: La Albuera (Badajoz) and Villarrobledo (Albacete), during 2016 and 2017. The soil of La Albuera is clay-loam texture, 1 m deep and 160 mm/m available water capacity (AWC); respect to climate is warm, cool nights and very dry according to the classification of [1]. The Villarrobledo soil is 0.75 m deep, silty-clay-loam texture and 135 mm/m AWC; the climate is very warm, cool nights and moderately dry climate. The study consisted in maintaining during two consecutive years and in both locations, the same hydric state of grapevine, which was evaluated by measurements of midday stem water potential, and comparing productive results obtained in the two places. Results derived from the analysis of yield components, as well as those derived of grape composition (total acidity, tartaric acid, malic acid, pH, potassium and soluble solids) show little variation between locations, instead great interannual variation among the parameters studied, so the "year-variety" effect seems to influence much more to the final result than the "locality-variety", for the case under study.