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The continuous monitoring of water stress will increase the accuracy of the deficit irrigation scheduling. Almonds are very sensitive to water stress conditions and an important water consumer. Recently, a novel approach to the use of trunk growth rate (TGR) data has been proposed for olive trees. These works suggested the use of TGR frequencies to evaluate water status of the trees. The aim of the current work was to compare the seasonal pattern of three different indicators derived from the daily curves of trunk diameter fluctuations with midday stem water potential. During three consecutive seasons (2017-2019), an irrigation experiment was carried out in a mature almond orchard (cv Vairo) at Dos Hermanas (Seville, Spain). Four irrigation treatments replicated in four blocks were evaluated using the daily curves of midday stem water potential and trunk diameter fluctuations. The different irrigation treatments were: Control, full irrigated conditions; RDI-1 (irrigation scheduling based on midday stem water potential with a deficit irrigation during kernel filling [values around -1.2 MPa]); RDI-2 (similar to RDI-1 but with a more severe water stress [-2 MPa]) and incomplete recovery after harvest due to limitation of the seasonal amount of water (around 100 mm); SDI, sustained deficit irrigation with a seasonal applied water equal to RDI-2. Trunk diameter fluctuations were measured with a wireless band dendrometer. The daily curves were processed to obtain three different indicators. Maximum daily shrinkage (MDS) was the difference between the daily maximum and minimum. Trunk growth rate (TGR) was the difference between two consecutive daily maximums. The frequencies of several ranges of TGR were compared with the midday stem water potential. Weekly frequencies of values greater than 0.3 mm day(-1) decreased with the reduction of midday stem water potential, but the pattern changed greatly in different seasons. The weekly frequency of values between - 0.1 and 0 and

Drought sensitivity in olive trees varies throughout the season. The yield response to drought needs to consider the final use of the fruits and harvest date. In Mediterranean climates, the oil accumulation tends to occur in a period of low evaporative demand and during the rainy period. The aim of this work was to evaluate the effect of water stress during pit hardening on the yield components of oil olive trees. The experiment was conducted during three seasons (2017–2019) in a mature hedgerow olive orchard (11 years-old, Arbequina cv). The experiment design was a randomized completed block with 4 repetitions of 4 different irrigation treatments. Treatments were: Control, no water stress throughout the season; Regulated deficit irrigation (RDI)-1, moderate water stress during pit hardening and total recovery after the last week of August; RDI-2, same as RDI-1 but with severe water stress and partial recovery; and sustained deficit irrigation (SDI), constant applied water rate and the same seasonal water than RDI-2. The irrigation scheduling in RDIs were based on the frequencies of the trunk growth rate. No significant differences were found in fruit and oil yield between treatments. There were a significant relationship between water status measurements and fruit and oil yield. Part of the decrease in fruit yield with midday stem water potential (SWP) was related to fruit moisture, as no significant fruit drop was found. Only conditions of water stress in 2017, before the end of endocarp size, were related to a great reduction of fruit volume and, consequently, with fruit and oil yield. The relationship between the percentage of oil in dry weight and SWP was quadratic in different phases. Such relationships could help quantify the water stress level in these periods to maximize oil accumulation. © 2021 Elsevier B.V.

Regulated deficit irrigation (RDI) involves water stress management in different phenological periods throughout the season. Research in olive trees (oil production) suggested RDI during pit hardening based in pre-dawn and midday stem water potential (SWP) thresholds. However, the previous thresholds may not be extrapolated to table olive because fruit size, a very important feature in the table olive yield quality, is very sensitive to water stress. RDI in table olive deserve further research to determine the optimal water potential thresholds and the duration of the RDI periods for the specificity of the crop (low crop load to promote high fruit size). The aim of this work was to study different RDI schedules during pit hardening, considering different levels and durations of water stress. The experiment was performed in the 2015, 2016 and 2017 seasons, in a commercial mature table olive orchard (cv. Manzanilla) in Dos Hermanas (Seville, Spain). Control treatments were based on midday SWP measurement in order to optimize the water status with values around −1.4 MPa. Two RDI treatments were applied during pit hardening, dated (according to the changes in longitudinal fruit growth) from mid-June to the last week of August) to maintain water potential values around −2 MPa (RDI-1) and −3.5 MPa (RDI-3). Another RDI treatment (RDI-2) received irrigation to maintain values around −3.5 MPa but the recovery was performed at early July in order to obtain different durations of water stress. Irrigation strategies were evaluated with water relations measurements (soil moisture, gas exchange), fruit and shoot growth and quality and quantity yield indicators. Yield was not significantly affected in any of the RDI treatments with an ANOVA analysis. However, fruit drop estimated as the percentage of fruit lost only in the period of water deficit was related with water stress parameters (SWP and stress integral, IS). In addition, the relationship between fruits size and these latt

El olivar es un cultivo milenario en la cuenca Mediterránea, asociado habitualmente a condiciones de secano. Esto es debido a su gran resistencia al estrés hídrico, que le permite soportar condiciones extremas de falta de agua, siendo capaz de continuar produciendo. No obstante, el riego e este cultivo supone una mejora en la producción, mayor cuanto más densos son los olivares. Esta mejora productiva ha dado lugar a un incremento paulatino de la superficie en estas condiciones

Deficit irrigation scheduling is becoming increasingly important under commercial conditions. Water status measurement is a useful tool in these conditions. However, the information about water stress levels for olive trees is scarce. The aim of this experiment was to evaluate the effect on yield of a moderate controlled water stress level at the end of the irrigation season. The experiment was conducted in the experimental farm of La Hampa (Coria del Río, Seville, Spain) during three years. A completely randomized block design was performed using three different irrigation treatments. Deficit irrigation was applied several (4 or 2) weeks before harvest. Irrigation was controlled using the midday stem water potential, with a threshold value of −2 MPa and compared with a full irrigated treatment. This water stress did not reduced gas exchange during the deficit period. The effect on yield was not significant in any of the three seasons. In the high-fruit load season, fruit volume was slightly affected (around 10%), but this was not significant at harvest. Results suggest an early affection of fruit growth with water stress, but with a slow rate of decrease. Moderate water stress could be useful for the management of deficit irrigation in table olive trees.

Sustainability is a feature that most companies adopt in order to improve their profits, even when their activity is not sustainable or the definition in their sector is not clear. This concept actually relates to the management of natural resources. Agriculture, and particularly irrigation scheduling, is strongly linked to a sustainable management; however, it is not clear what defines a sustainable management. Several efforts have been made to improve the conservation of water resources, but most of them have not involved growers at the orchard level; and consequently, they have lost their opportunity to create a real improvement in terms of sustainability. The aim of this work was to design a “hydroSOStainable index” (or “hydroSOS index”) that evaluates different aspects at orchard level to improve the sustainability of the water resources. The hydroSOS index considers 16 indicators grouped in 4 areas: (i) hydraulic indicators, (ii) horticultural indicators not related to irrigation scheduling, (iii) horticultural indicators related to the moment when deficit irrigation is applied (when?), and (iv) horticultural indicators related to the way deficit irrigation is applied (how?). Each indicator provides different marks or scores, and their sum allows classifying orchard management into four labels. The weight of each indicator and each group is not in itself enough to obtain a maximum label. Groups allow to easily identify the main limitations for the orchard to achieve a sustainable irrigation management. This index was used to evaluate water management of two cases of study. © 2019 Elsevier B.V.

Reduced water availability around the world drives the need for indicators that enable a better control of water stress at orchard level. Among the different parameters that could be used as indicators, trunk diameter fluctiations, are daily cycles suggested as tools for irrigation scheduling. These cycles can define different indicators and the trunk growth rate (TGR) was suggested as the most suitable for olive trees. Several works indicated that average TGR values are related to the tree water status even threshold values have been suggested. In addition, only daily TGR values below −0.1 mm day−1 were mentioned as water stress indicators. The aim of this work is to evaluate an irrigation scheduling approach based on those two results mentioned. To this end, an experiment was performed during the 2017 season, in a commercial, super-high-density orchard in Carmona (Seville, Spain). Four different irrigation treatments were applied based on midday stem water potential values and TGR. The Control treatment, with 100% ETc (crop evapotranspiration) and sustained deficit irrigation, was compared with two regulated deficit irrigation strategies based on TGR measurements. Severe water stress conditions were measured in the three deficit treatments. Irrigation scheduling using average TGR was not a suitable tool for the aim of the experiment because some data were lost and there were great variations in TGR values. However, it was found that average TGR values were related to midday stem water potential. The water potential and daily TGR data were grouped according to water stress levels (into values with water potential higher of −1.4 MPa and lower than −4 MPa). Daily TGR values greater than 0.3 mm day−1 were identified in response to severe water stress conditions. Weekly frequency of daily TGR values between −0.1 and 0.3 mm day−1 decreased from 60% to 25% when water stress level increased. Therefore, frequency and value of daily TGR are suggested as irrigation schedulin

Irrigation needs in mature almond orchards are very high. Although almond trees grow in rainfed conditions, the yield response is very sensitive to irrigation. Continuous monitoring of the water status could be an adequate tool to optimize deficit irrigation. In this sense, trunk diameter fluctuations appeared as a very promising indicator at the beginning of the century, but few data have been published. The aim of this work is to check threshold values of maximum daily shrikage (MDS) and identify possible limitations to their use in commercial orchards. The experiment was performed in a commercial farm in Dos Hermanas (Seville, Spain) during the 2017 season on a 7-years-old orchard (cv Vairo). The irrigation treatments were Control (100% ETc), sustained deficit irrigation (SDI) with a maximum seasonal irrigation of 100 mm and two regulated deficit treatments (RDI). Both RDI treatments (RDI-1 and RDI-2) were scheduled using the signal of maximum daily shrinkage (signal) and the midday stem water potential (SWP). In RDI-1, full irrigation conditions were provided before kernel filling and during postharvest, using the threshold values suggested in the bibliography. During kernel filling, the water stress level was designed to be -1.5 MPa (SWP) and 1.75 (signal). RDI-2 trees were irrigated using the same scheduling as RDI-1, but target water stress values were higher in kernel filling (-2 MPa and 2.75) and with a maximum seasonal amount of water of 100 mm. SWP in Control trees was near the McCutchan and Shackel baseline for most of the season. None of the deficit treatments reached the signal values suggested. Moreover, the signal values were almost equal between treatments, with no water stress effect. The trunk growth rate (TGR) presented clear differences depending on the water status.