Limitations and usefulness of maximum daily shrinkage (MDS) and trunk growth rate (TGR) indicators in the irrigation scheduling of table olive trees

Maximum daily trunk shrinkage (MDS) is the most popular indicator derived from trunk diameter fluctuations in most fruit trees and has been reported to be one of the earliest signs in the detection of water stress. However, in some species such as olive trees (Olea europaea L.), MDS does not usually change in water stress conditions and trunk growth rate (TGR) has been suggested as better indicator. Most of this lack of sensitivity to drought conditions has been related to the relationship between the MDS and the water potential. This curvilinear relationship produces an uncertain zone were great variations of water potential do not imply any changes of MDS. The MDS signal, the ratio between measured MDS and estimated MDS with full irrigation, has been thought to be a better indicator than MDS, as it reduces the effect of the environment.. On the other hand, though literature results suggest an effect of environment in TGR values, there are not clear relationship between this indicator and meteorological data. The aims of this work are, on one hand, to study the improvements of the baseline approach in the MDS signal and, on the other, study the influence of several meteorological variables in TGR. Three years’ data from an irrigation experiment were used in to carry out the MDS analysis and six years’ data for full irrigated trees during pit hardening period were used for TGR study. The comparison between MDS vs. water potential and MDS signal vs. water potential presented a great scattering in both relationships. Values of MDS signal between 1.1 and 1.4 were always identified with moderate water stress conditions (−1.4 to −2 MPa of water potential). However, since this MDS signal values are around the maximum in the curvilineal relationship with water potential, greater values of MDS signal (in the range of 1.1–1.4) were not necessary lower values of water potential. In addition, during low fruit load seasons MDS signal was not an accurate indicator. On the other hand, absolute values of several climatological measurements were not significantly related with TGR. Only daily increments explain part of the variations of TGR in full irrigated trees. In all the data analysed, the daily increment of average vapour pressure deficit was the best indicator related with TGR. The increase of this indicator decreased TGR values. In addition, the agreement between this indicator and TGR was affected for fruit load. Great yield seasons decrease the influence of VPD increment in TGR.Spanish Ministerio de Ciencia e Innovación, (AGL2010-19201-CO4-03 and AGL2013-45922-C2-1-R

Identification of the water stress level in olive trees during pit hardening using the trunk growth rate indicator.

Water scarcity is generating an increasing interest in deficit irrigation scheduling. The trunk diameter fluctuations are daily cycles that have been suggested as tools for irrigation scheduling. The trunk growth rate (TGR) was suggested as the best indicator for olive trees during pit hardening. The aim of this work is to clarify how the TGR could be used to identify water stress levels. The experiment was performed during the 2017 season, in a commercial, super-high-density orchard in Carmona (Seville, Spain). Four different irrigation treatments were performed according to midday stem water potential values and TGR. The data obtained were very variable and both indicators presented a wide range of water status throughout the season. The maximum trunk diameter data clearly showed the pattern of the trees water status but the comparison between treatments and the identification of the water stress level was not possible. The average TGR was linked to the midday stem water potential, but with a minimum amount of data. Irrigation scheduling based on the average TGR was difficult because of the great increases in some daily TGR values. For clarity, the pool of data was grouped by midday stem water potential. These water stress levels were characterized using the weekly frequency of TGR values. The increase of water stress reduced the frequency of values between -0.1 and 0.3mm day-1 from 60% to less than 25%. Moderate water stress levels increased the percentage of values lower than -0.3mm day-1 from 7% to 37%. The most severe water stress conditions increased the TGR values between -0.3 and -0.1mm day-1 from 16% up to 22%.IRNASINSTITUTO DE LA GRASACSI

Umbrales sostenibles de estrés hídrico durante el endurecimiento del hueso en la producción de aceituna de mesa

La programación del riego deficitario controlado (RDC) es una necesidad derivada de la escasez de agua disponible para el riego. La resistencia al estrés hídrico de los diferentes estados fenológicos en olivar está bastante bien documentada pero no así los niveles de estrés hídrico. El objetivo de este trabajo es sugerir en base a experimentos realizados en los últimos 7 años los niveles de estrés hídrico para el manejo del RDC en olivar.Los experimentos descritos en la presente comunicación se han desarrollado en la finca “La Hampa” propiedad del IRNAS (CSIC) en Coria del Río (Sevilla), en un olivar de 37 años cv “Manzanillo” y a un marco de 7*5m. Los experimentos se establecieron con diferentes tratamientos de riego, aplicando condiciones de estrés hídrico durante endurecimiento de hueso y unas semanas antes de cosecha. Se discute los diferentes umbrales detectados y su efecto en cosecha, cantidad y calidad, y en la fisiología de la planta en el años en curso en el ciclo bianual del olivo.Ministerio de Economía y Competitividad AGL2007-66279-C03-00Ministerio de Economía y Competitividad AGL2010-19201-CO4-03Ministerio de Economía y Competitividad AGL2013-45922-C2-1-

Identification of water stress conditions in olive trees through frequencies of trunk growth rate

Continuous monitoring of the tree water status will enhance irrigation performance, particularly when applying deficit schedules. The olive tree is a highly drought-resistant species and management of the water stress could increase water savings. Trunk diameter fluctuations can be displayed as daily curves representing the shrinkage and swelling, and can provide information about tree water status. In olive trees, trunk growth rate (TGR) is the most useful indicator, but the daily variability reduced the commercial applications. Recently, weekly frequencies of TGR values were associated to the water status in one seasonal experiment. The aim of this work is to study the seasonal pattern and the interannual variations of these parameters in order to integrate them in an irrigation scheduling tool. The experiment was performed during two consecutive seasons (2018 and 2019) in a superhigh density mature olive orchard at Carmona (Seville, Spain). Three different irrigation scheduling treatments were considered in a randomized complete block design. The control treatment was fully irrigated with 150–175% crop evapotranspiration (ETc) in order to ensure an optimum water status. Regulated deficit irrigation-1 (RDI-1) was scheduled using only TGR data provided through the continuous measurements from a dendrometer. In this treatment, water stress conditions were controlled during the pit hardening period. RDI-2 was similar to RDI-1, but with a more severe water stress conditions during pit hardening and a maximum seasonal amount of water that limited rehydration. Water stress was greater during the 2019 season than the 2018 season, according to the midday stem water potential (SWP). Weekly frequencies of TGR values lower than − 0.3 mm day− 1 (Severe FR) and values between − 0.1 and 0.3 mm day− 1 (Good FR) described the water status pattern in the three treatments for both seasons. Only under severe water stress conditions (SWP more negative than − 4 MPa) the values of these frequencies did not identify accurately the water status. However, the use of weekly frequencies of values greater than 0.3 mm day− 1 (Alert FR) and the pattern of these Severe FR and Good FR themselves identified such conditions. The use of these three weekly frequencies (Severe, Good and Alert (SGA) approach) are suggested for continuous deficit irrigation scheduling in olive trees

Water Relations in the Irrigation Scheduling of Olive Orchards

Olive trees (Olea europea L) are traditional Mediterranean specie. The agricultural management of olive orchards has been changed from 90’s of the last century. The most important change is the great increase of the irrigation surface. This new water demand has been produced in water scarcity areas. Such conditions and the traditional rainfed management of the orchards have produced very restrictive water used. The traditional irrigation scheduling based on water budget is a useful tool in conditions of full irrigation, but most of the olive orchards are deficit irrigated. In the last decades, plant water status measurements have been suggested in different fruits trees in order to improve the management of deficit irrigation. In this work, results of several experiments in different olive orchards using midday stem water potential and trunk daily diameter are presented. The water stress sensitivity and the real commercial utility are discusse

Influence of rootstocks on pistachio (Pistacia vera L.) water relations

Pistachio potted plants budded on three different rootstocks were submitted to water stress during 28 days with the aim of studying their water relations and physiological responses. Water stress resulted in an accented drop of stem water potential and leaf conductance. Nonetheless, pistachio plants showed a great capacity to contrast drought effects by the recourse to osmotic adjustment mechanisms. Regarding rootstocks, UCB-I results being the less adapted rootstock to conditions of water stress

Antioxidants (carotenoids and phenolics) profile of cherry tomatoes as influenced by deficit irrigation, ripening and cluster

The purpose of this study was to assess the relationship between the effect of regulated deficit irrigation, cluster, developmental stages and two seasons (autumn 2015 and spring 2016) on the commercial and functional quality (carotenoids and plenolics levels) in ‘Lazarino’ and 'summerbrix’ tomatoes. Autumn had a positive effect on the commercial quality, with larger fruits (22% in 'summerbrix’; 26% in ‘Lazarino’) and higher soluble solids (16% in 'summerbrix’; 12% in ‘Lazarino’). Total carotenoids did not change significantly with irrigation and variety while total phenolics did with the cluster and season. In most cases, the main amounts of carotenoids and phenolic were found in the higher cluster and carotenoids in ripe fruit. Thus, irrigation of such varieties could be reduced drastically (ca. 80%) without affecting considerably the overall quality of their fruits (changes not greater than 30%).Ministerio de Economía y Competitividad AGL2012-37610, BIO2015-71703-RED

Criteria for HydroSOS Quality Index. Application to Extra Virgin Olive Oil and Processed Table Olives

Water, especially in arid and semiarid regions, is increasingly a disputed commodity among different productive sectors; the pressure for a more sustainable use of water in agriculture will grow. The main strategy to cope with water scarcity is the use of improved, innovative, and precise deficit irrigation management practices which are able to minimize the impact on fruit yield and quality. The aim of this paper was to develop a certification index or hydroSOS quality index for extra virgin olive oil and processed table olives. The hydrosSOS fruits and vegetables are those cultivated under regulated deficit irrigation (RDI). Different indicators in three quality areas ((i) fatty acids, (ii) phenolic compounds, and (iii) sensory attributes) were identified as showing characteristic or typical responses under RDI conditions. Marks or scores were assigned to each one of these indicators to calculate the proposed index. It can be concluded that an extra virgin olive oil (EVOO) or processed table olives are hydroSOStainable foods, if they meet 2 conditions: (i) fulfill the conditions established in the hydroSOS “irrigation” index, and (ii) fulfill the requirements of the hydroSOS “quality” index. HydroSOS quality index will be specific to each crop and variety and will depend on functional and sensory factors

Absence of Yield Reduction after Controlled Water Stress during Prehaverst Period in Table OliveTrees

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 tree

Effect of regulated deficit irrigation on commercial quality parameters, carotenoids, phenolics and sugars of the black cherry tomato (Solanum lycopersicum L.) ʽSunchocolaʼ

In this preliminary study, the effect of regulated deficit irrigation (RDI) on the commercial quality (size, weight, soluble solids, firmness and colour), content of carotenoids, phenolics and sugars of black tomato (Solanum lycopersicum L.) ʽSunchocolaʼ was studied. Two water irrigation treatments were applied: regulated deficit irrigation (RDI) and control with 82,7 and 398 mm of water supplied, respectively. Tomato of the first cluster harvested at three stages of maturity were studied. The size and weight of the tomato did not present significant differences regarding the RDI and maturity. In both groups the concentration of carotenoids and phenolics increased with the degree of maturity (on average 57 % and 8 % respectively). On the other hand, in most cases, the content of carotenoids, phenolics and sugars showed significant differences between irrigation treatments (p < 0.1). In conclusion, with the application of the RDI, it was possible to maintain the size and weight and increase the carotenoid levels of the fruits.Secretaría Nacional de Educación Superior, Ciencia, Tecnología e Innovacion (SENESCYT)Ministerio de Economía y Competitividad AGL2012-37610Ministerio de Economía y Competitividad BIO2015-71703- RED