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There is a controversy regarding when it is appropriate to apply the irrigation restriction in almond trees (Prunus dulcis Mill.) to save water without penalizing yield. We hypothesized that knowing when plants demand fewer photoassimilates would be a good indicator of less sensitivity of the crop to water deficit. One parameter that defines the photosynthetic capacity is the triose phosphate utilization (TPU). Due to its connection to the export of sugars from the leaves to other sink organs, it is a good candidate for being such an indicator. The objective was to analyze the seasonal evolution of the photosynthetic capacity of three almond cultivars (cvs Guara, Marta and Lauranne) subjected to water stress during vegetative, kernel-filling and postharvest stages. Two sustained deficit irrigation (SDI) treatments (SDI75 and SDI65 with water reductions of 25 and 35%, respectively) and a control treatment (FI) consisting of fully irrigated trees were applied. The response of curves A(N)-Ci was analyzed to assess the maximum carboxylation rate (V-cmax), maximum rate of electron transport (J(max)), TPU and mesophyll conductance to CO2. In addition, leaf water potential and yield were measured. Our experimental findings showed any significant differences in the variables analyzed among cultivars and irrigation treatments. However, consistent differences arose when the results were compared among the phenological stages. During the kernel-filling and the postharvest stages, a progressive limitation by TPU was measured, suggesting that the demand for photoassimilates by the plant was reduced. This result was supported by the correlation found between TPU and fruit growth rate. As a consequence, a downregulation in J(max) and V-cmax was also measured. This study confirms that the kernel-filling stage might be a good time to apply a reduction in the irrigation and suggests a method to detect the best moments to apply a regulated deficit irrigation in almond trees.

[EN]: Climate change, water resources reduction, or land degradation and abandonment are some limitations to overcome within the new model of achieving competitive and sustainable agriculture. Among the possible strategies, the implementation of drought tolerant crops with high profitability, and the application of water saving strategies such as deficit irrigation (DI) should be considered. In this regard, almond (Prunus dulcis Mill.) would be an excellent alternative under water scarcity and climate change scenarios. However, it is essential to reach an equilibrium between crop management to enhance its productivity and the water availability; defining its water requirements and the relationships between irrigation needs and crop development. In this sense, the general objective of this doctoral thesis was to improve the almond irrigation management, specifically in three of the most traditional cultivars in south Spain (cvs. Guara, Marta and Lauranne) using two DI strategies; regulated deficit irrigation (RDI) and sustained deficit irrigation (SDI). In order to optimize the irrigation water management for each studied cultivar and increase the quality of almonds, [ES]: El cambio climático, la reducción de los recursos hídricos o la degradación y el abandono de la tierra son algunas de las limitaciones que hay que superar en la búsqueda de una agricultura competitiva y sostenible. Dentro de las posibles estrategias, debe considerarse la implementación de cultivos tolerantes a la sequía con alta rentabilidad y la implementación de estrategias de ahorro de agua como las estrategias de riego deficitario (RD). Dentro de las posibilidades de cultivo, el almendro (Prunus dulcis Mill.) sería una excelente alternativa ante un escenario de escasez de agua y cambio climático. Sin embargo, es esencial alcanzar un equilibrio entre la gestión de cultivos y la disponibilidad de agua, definiendo sus necesidades hídricas y las relaciones entre las necesidades de riego y las prácticas agronómicas. En este sentido el objetivo general de esta tesis doctoral fue mejorar el manejo del riego del cultivo del almendro, concretamente en tres de las variedades más implementadas en el sector almendrero (cvs. Guara, Marta y Lauranne) usando dos estrategias de RD diferentes; riego deficitario controlado (RDC) y riego deficitario sostenido (RDS). Con el objetivo de optimizar el manejo del agua de riego para cada variedad estudiada y aumentar la calidad de la almendra obtenida

The need to improve agroecosystem sustainability to secure yields, minimize environmental impacts and improve soil health is widely recognized. Organic production systems are one of the strategies that may be used to alleviate the negative environmental repercussions of conventional agriculture. In the present study, we compared the impact of conventional and organic production systems on the almond (Prunus dulcis (Mill.) D.A. Webb) yield and quality of nuts of two cultivars (Marcona and Desmayo largueta), with both systems being managed on marginal hillslopes in the southeast of Spain. Our findings show that the organic production system in rainfed almond trees has positive effects on certain nut quality parameters, with a slight decrease in almond yield, specifically 9.5% for cv. D. largueta and 1.3% for cv. Marcona, with respect to the conventional system. The results obtained have varied depending on the cultivar. Statistically significant differences have been obtained for cv. Marcona in the sugar content (54.4 and 49.8 g kg−1 in organic and conventional, respectively) and the total phenol content (3.41 and 2.46 g GAE kg−1 for organic and conventional, respectively). In the case of cv D. largueta, statistically significant differences were found between the organic and conventional systems for antioxidant activity (14.8 vs. 8.68 mmol Trolox kg−1, DPPH), fatty acid content (229 vs. 188 g kg−1 dw), saturated fatty acids (36 vs. 28.7 g kg−1 dw), monounsaturated fatty acids (113 vs. 110 g kg−1 dw) and polyunsaturated fatty acids (60.3 vs. 49.6 g kg−1 dw ). Here, we show for the first time how a rainfed organic system allows for higher- quality almonds, specifically with a higher content of phytochemicals beneficial for health, which, together with the higher price compared to conventional almonds, could compensate for the yield losses while preserving the sustainability of marginal agroecosystems.

As a network of researchers we release an open-access database (EUSEDcollab) of water discharge and suspended sediment yield time series records collected in small to medium sized catchments in Europe. EUSEDcollab is compiled to overcome the scarcity of open-access data at relevant spatial scales for studies on runoff, soil loss by water erosion and sediment delivery. Multi-source measurement data from numerous researchers and institutions were harmonised into a common time series and metadata structure. Data reuse is facilitated through accompanying metadata descriptors providing background technical information for each monitoring station setup. Across ten European countries, EUSEDcollab covers over 1600 catchment years of data from 245 catchments at event (11 catchments), daily (22 catchments) and monthly (212 catchments) temporal resolution, and is unique in its focus on small to medium catchment drainage areas (median = 43 km2, min = 0.04 km2, max = 817 km2) with applicability for soil erosion research. We release this database with the aim of uniting people, knowledge and data through the European Union Soil Observatory (EUSO).

Deficit irrigation (DI) strategies are considered essential in many arid and semi-arid areas of Mediterranean countries for proper water management under drought conditions. This fact is even more necessary in crops such as almond (Prunus dulcis Mill.), which in the last recent years has been progressively introduced in irrigated areas. An essential aspect to be considered would be the ability to improve fruit-quality parameters when DI strategies are imposed, which can boost the final almond price and ensure the sustainability and competitiveness of this crop. This work examines the effects of sustained deficit irrigation (SDI) on three almond cultivars (Marta, Guara, and Lauranne) on parameters related to almond functionality, aroma and sensory profile, which consequently influence its marketability and consumers acceptance. SDI strategies allowed the improvement of physical parameters such as unit weight, kernel length, kernel thickness or color. Moreover, higher total phenolic compounds, organic acids and sugars were found in SDI almonds. Finally, the highest concentrations of volatile compounds were obtained under SDI, this being a clear advantage in relation to almond flavor. Thus, moderate SDI strategy offered relevant improvements in parameters regarding the marketability, by enhancing the final added value of hydroSOStainable almonds with respect to those cultivated under full irrigation conditions.

Terracing is a soil conservation strategy applied worldwide to prevent erosion and runoff on sloping lands. Orchard terraces can considerably reduce soil loss due to water erosion if they are well planned, correctly constructed and properly maintained. Terraces have to be combined with additional soil conservation practices, of which the most important is the maintenance of a soil cover, especially during the rainy period. On the coastal strip of the provinces of Granada and Malaga (south-eastern Spain), irrigated subtropical fruit species have been introduced and cultivated on terraces with a considerable importance as the only European producer region. The subtropical farming in this zone also has strong socio-economic impact. In the present chapter, land-use changes were analysed in a selected representative watershed over 29 years. According to the findings, formerly, 97.5% of the watershed was devoted to traditional Mediterranean crops; however, after this period, due to abandonment, this area was reduced to 17.6% and increased in subtropical fruit crops (26.6%), shrubland (29.8%) and abandoned cropland (24.6%). The main driving force in land-use change has been intensive irrigation on terraces planted with subtropical crops, which are economically more profitable than traditional rainfed crops, almond and olive, which have been replaced or abandoned. The intensification of subtropical farming in terraces provokes environmental effects, especially those regarding soil and water resources, which need to be minimized. The results support the recommendation of using plant covers on the taluses of subtropical crop terraces in order to control soil erosion and improve the soil quality in the taluses of orchard terraces. In this sense, compared to bare soil, thyme and native spontaneous vegetation plant covers reduced the runoff with 94% and 93% and declined erosion with 71% and 79%, respectively. That is to avoid the collapse of the structure and make more feasible

Mango (Mangifera indica L.) is one of the most important fruit crops in tropical and subtropical regions worldwide. On the coast of Granada and Malaga (SE Spain), irrigated subtropical fruit species have been introduced and cultivated on terraces with a considerable economic importance as the only European production region. The subtropical fruit production in this zone is possible with intensive irrigation on terraces, which are economically more profitable than traditional rainfed crops (almond and olive), which have been replaced or abandoned. A 2-year monitoring period was conducted using drainage lysimeters to determine the crop coefficients (Kc) and fruit yield in mango (Mangifera indica L. cv. Osteen) orchards. Also, some quality parameters such as titratable acidity, total soluble solids, and vitamin C were evaluated under these conditions. The averaged Kc values of mango trees varied within production cycle of 0.43, 0.67, and 0.63 at flowering, fruit set, and fruit growth, respectively. In this study, the fruit yield under full water requirements (100% ETC) averaged 24.1 kg tree−1, amounting to 21.2 kg ha−1 mm−1 in terms of water-use efficiency. The quality parameters of the mango fruits harvested in the study area were satisfactory. Thus, this study highlights the need to optimize the irrigation-water use according to actual mango requirements, thereby achieving more sustainable Mediterranean subtropical farming in orchard terraces.

Water scarcity in many semi-arid agricultural areas, in particular for the Mediterranean basin, is promoting changes in irrigated agriculture, with alternative strategies being introduced for water-use optimization. The coast of Granada and Malaga (Southeast Spain) is an economically important area for subtropical fruit cultivation. This intensively irrigated agriculture is characterized by requiring extra amounts of water and the adoption of sustainable practices to improve agricultural water management. A two-season experiment was conducted to assess (1) the water use in terraced cherimoya (Annona cherimola Mill. cv. Fino de Jete) orchards under conventional and organic production systems with drainage lysimeters, and (2) the impact on fruit yield and nutritional effects between the two considered production systems. Crop coefficient (Kc) values for cherimoya were 0.60–0.66, 0.64–0.71, and 0.48–0.62 at flowering, fruit set, and fruit growth, respectively. Fruit yield was similar in both systems, ranging from 47.1 for conventional to 44.1 kg tree−1 for organic farming, averaging 13.2 and 12.3 t·ha−1, respectively. No differences between these systems were observed in terms of leaf nutrient status, with variations in the N, P, and K contents during the different phenological stages. The N, P, and K lessen during flowering and fruit growth; the highest levels of these nutrients were fixed at harvest. These patterns were the opposite in Ca and Mg, ascribable to the antagonism between K and both Ca and Mg. Thus, these findings highlight the need to establish the optimal use of irrigation water with respect to crop requirements, thereby encouraging sustainable subtropical farming in terraces.

Water is the most limiting resource in many semi-arid areas of Mediterranean countries. Among the strategies to improve water productivity, the implementation of deficit irrigation (DI) strategies and the introduction of drought-tolerant crops in irrigated areas (such as almond) are being widely studied. Recently, the use of biostimulants to enhance crop tolerance to drought under water-scarcity scenarios is increasing. This work examines the response of three almond cultivars (‘Guara’, ‘Marta’, and ‘Lauranne’) in terms of yield and associated physiological responses in the main phenological stages to biostimulants (HYT® A and HYT® B plus) applied to young trees subjected to different irrigation levels: (i) a full irrigation treatment (FI), irrigated at 100% of crop evapotranspiration (ETC); and (ii) sustained-deficit irrigation (SDI75), irrigated at 75% of ETC. Significantly higher yields were obtained with HYT applications in 2 of 3 cultivars; these differences were most evident in the SDI75 treatment. In particular, ‘Guara’ registered the most significant improvements in nut yield when the HYT product was applied (15–20% higher). With regard to crop physiological responses, higher values of leaf water potential and stomatal conductance were noted with the HYT application in some cultivars and phenological stages. These results indicated that the use of biostimulants can be a feasible strategy for almond cultivation, especially when SDI is used.

Almond (Prunus dulcis Mill. [D.A. Webb]) is the third most widely spread crop in Spain and has traditionally been cultivated in marginal areas and shallow soils under rainfed conditions. However, it recently has been progressively introduced in flat irrigated areas. The implementation of cover crops in the inter-rows of woody crops has been proven as a suitable strategy to reduce the runoff and soil erosion but they also can boost soil quality and health. A field experiment was conducted during two-monitoring seasons to examine the soil nitrogen and carbon sequestration potential of three seeded cover crops [barley (Hordeum vulgare L.), hairy vetch (Vicia villosa Roth), and a mixture of 65% barley and 35% vetch] and a control of spontaneous flora in irrigated almond orchards (SW Spain). Here, we show that barley provided the highest biomass amount, followed by mixture covers, vetch, and the control treatment. Also, vetch covered the soil faster in the growing stage, but its residues were decomposed easier than barley and mixture treatments during the decomposition period after mowing, providing less soil protection when the risk of water erosion with autumn rainfall is high. On the other hand, vetch improved soil nitrate content by over 35% with respect to barley and mixture treatments at 0–20 cm soil depth throughout the studied period. In addition, a greater carbon input to the soil was determined in the barley plot. That is, the mixture and barley cover crops had higher potential for carbon sequestration, augmenting the soil organic carbon by more than 1.0 Mg ha−1 during the study period. Thus, taking into consideration the findings of the present experiment, the establishment of a seeded cover crop would be more advisable than spontaneous flora to mitigate soil erosion, enhancing soil fertility and carbon sequestration in irrigated almond plantations in Mediterranean semi-arid regions.

The Mediterranean region is one of the most water-scarce areas worldwide and is considered a climate-change hotspot. To assure the viability and competitiveness of irrigated agriculture, it is vital to implement strategies that can maximize water saving without compromising yield. Deficit irrigation (DI) for cultivating drought-tolerant species such as almond (Prunus dulcis (Mill.) D.A. Webb) can help in achieving this goal, while at the same time improving fruit chemical composition. This work evaluated the effect of DI techniques and cultivars on the chemical composition of almonds (cvs. Marta, Guara, and Lauranne) in order to elucidate the most suitable irrigation dose under water-scarcity scenarios. Three irrigation regimes were imposed: a control treatment (FI), which was fully irrigated, receiving 100% of the irrigation requirement (IR), and two sustained-deficit irrigation (SDI) strategies that received 75% (SDI75) and 65% (SDI65) of IR. Significant differences among cultivars and irrigation treatments were observed for antioxidant activity and organic acid, sugar, and fatty acid content, which were increased by the SDI strategies. In addition, highly significant correlations were found between leaf-water potential and components such as fumaric acid, sugars, and fatty acids. In terms of the cultivars, cv. Marta showed the highest antioxidant activity, cv. Guara was the richest in organic acids, and cv. Lauranne had the highest fatty acid content. Consequently, SDI strategies improved almond quality parameters related to their nutritional and sensory composition, with significant water savings (reductions of 25–35%) and without important yield loss.

Climate change, water resources depletion, or land degradation and abandonment are some constraints to overcome within the new paradigm of achieving competitive and sustainable agriculture. Within the possible strategies, the introduction of drought-tolerant crops with high profitability, and the implementation of water-saving strategies such as deficit irrigation (DI) should be considered. Within the crop possibilities, almond (Prunus dulcis Mill.) would be an excellent alternative under water scarcity and climate change scenarios. However, it is essential to reach an equilibrium between crop management and water availability, defining its water requirements and the relationships between irrigation needs and the agronomical practices. Once done, adaptation strategies to water scarcity should be considered, especially in those cases of lack to cover the total irrigation needs by DI practices. In this agreement, the success of these strategies will depend on the proper knowledge respect to crop phenological development and the assessment of physiological status using different available tools. Thus, different crop physiological responses to water stress will be observed and different taking decisions should be considered. Finally, implementing water-saving strategies will be done not only from the perspective of preserving maximum yields but also for product quality improvements, and hence providing a final added value.

The climate change is already affecting many agricultural systems and human environments, and the implementation of adaptation strategies, especially those related to irrigated agriculture in semiarid regions, is urgent. In this regard, deep knowledge about the effects that irrigation has on the food quality parameters will allow us to estimate the potential benefits of deficit irrigation (DI) strategies. This work presents the effects on the quality parameters of three almond cultivars (Marta, Guara, and Lauranne) subjected to three irrigation doses: (i) full-irrigated treatment (FI) at 100% crop evapotranspiration (ETC), (ii) an overirrigated treatment at 150% ETC (150% ETC), and (iii) regulated deficit irrigation (RDI65) treatment, in which irrigation was done as in FI, expect during the kernel-filling period when this treatment received 65% ETC. According to experimental findings, the cultivar most sensitive to water stress was Marta, having the most significant improvements for RDI65. In general, the effects of the irrigation dose on the morphological and physicochemical parameters were not huge but some improvements were observed in key parameters such as the color and contents of specific sugars, organic acids, and unsaturated fatty acids. Thus, it can be concluded that the irrigation dose did not drastically affect the fruit almond quality, although it is possible to improve several key parameters when a moderate RDI strategy is applied.