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Avocado (Persea americana Mill.) is a subtropical tree, particularly sensitive to either an excess or a lack of water. Understanding this balance is crucial to determine the optimum water supply and enhance crop productivity. The rising shortage of water resources in semiarid producing regions and the need for irrigation optimization call for sustainable water savings. A 3-year monitoring study with avocado cv. “Hass” tested sustained-deficit irrigation strategies supplying 33, 50 or 75% of the estimated crop water demand. They were compared with a control strategy supplying 100% of the estimated crop water demand. The leaf water potential, stomatal conductance, tree growth, yield and several fruit quality parameters were evaluated. The yield, tree growth and fruit size were significantly and proportionally lessened by deficit irrigation treatments. Over the study, the average yields amounted to 31.6, 38.3 and 43.8 kg tree−1 in the 33, 50 and 75% treatments respectively, which were significantly less than the yield of 47.5 kg tree−1 measured in the control. The 33% and 75% sustained-deficit irrigation treatments increased the omega 3 and omega 6 fatty acids as well as the unsaturated fatty acids (oleic); however, the 33% deficit irrigation treatment significantly reduced the yield, size and fruit weight. We consider, therefore, that approximately 25% of the irrigation water can be saved without adversely affecting the avocado tree performance in short and medium terms and we recommend implementing the 75% sustained-deficit irrigation strategy. Here we show for the first time the key role of redesigning irrigation strategies in Mediterranean areas, focusing on the benefits of sustained-deficit irrigation, which can save water, encourage water use efficiency and enhance fruit quality. In order to save water, it is critical and necessary to implement such novel water shortage strategies, at the affordable cost of reducing fruit yield while enhancing its quality.

Mango (Mangifera indica L.) is broadly grown in tropical regions and can also be cultivated in irrigated subtropical semi-arid areas; however, water shortages are a serious problem in the latter region. Among biotic and abiotic factors, water supply is one of the most crucial elements that determine productivity. The allocation of water will be an ever-increasing source of pressure because of vast agricultural demands under changing climatic conditions. Although the mango is considered to be tolerant to drought, water stress during growing cycle can reduce productivity. Here, we review the recent progress in evaluating and augmenting mango water productivity. Developments in physiological and agronomic understanding that have led to a boost in water productivity are presented. In addition, this review deals with deficit irrigation strategies to elucidate the effects on mango yield, water use efficiency, and the response of physiological indicators to water stress. Our main findings were as follows: (1) Under a changing climate, traditional irrigation based on water balance will not be sustainable in the medium/long term; (2) deficit irrigation strategies applied to mango can save irrigation water by up to 40% and improve water use efficiency by up to 30%; and (3) there is valuable potential for further improvement owing to advanced knowledge in terms of the physiological response of mango to water stress, and there are good prospects within the current approaches if they are associated with specific environmental physiology. We concluded that under current medium-/long-term perspectives regarding available water resources, particularly in arid and semi-arid regions, there is an urgent demand for adaptive and water-saving strategies. Thus, it will be vital to redesign irrigation schemes in areas where water is scarce to adjust deficit irrigation strategies not only to save water, enhance water use efficiency, and maintain yield, but also to produce fruits with improved quality.

Mango is one of the most cultivated tropical fruits worldwide and one of few drought-tolerant plants. Thus, in this study the effect of a sustained deficit irrigation (SDI) strategy on mango yield and quality was assessed with the aim of reducing irrigation water in mango crop. A randomized block design with four treatments was developed: (i) full irrigation (FI), assuring the crop’s water needs, and three levels of SDI receiving 75%, 50%, and 33% of irrigation water (SDI75, SDI50, and SDI33). Yield, morphology, color, titratable acidity (TA), total soluble solids (TSS), organic acids (OA), sugars, minerals, fiber, antioxidant activity (AA), and total phenolic content (TPC) were analyzed. The yield was reduced in SDI conditions (8%, 11%, and 20% for SDI75, SDI50, and SDI33, respectively), but the irrigation water productivity was higher in all SDI regimes. SDI significantly reduced the mango size, with SDI33 generating the smallest mangoes. Peel color significantly changed after 13 days of ripening, with SDI75 being the least ripe. The TA, AA, and citric acid were higher in SDI75, while the TPC and fiber increased in all SDI levels. Consequently, SDI reduced the mango size but increased the functionality of samples, without a severe detrimental effect on the yield.

International audience; AbstractThe soil erosion rates are high in the rainfed olive (Olea europaea L.) mountain plantations applying conventional practices in a semi-arid Mediterranean environment, which compromise their long-term sustainability. The implementation of sustainable soil management strategies is vital for hillslopes and low-fertility soils where plantations cover vast tracts of land. In Lanjarón (Granada, Spain), the soil erosion and runoff patterns over a 4-year monitoring period were studied in erosion plots on a mountainside under four types of production systems: (1) organic (spontaneous vegetation and leguminous covers), (2) conservation agriculture (combinations of minimum tillage with spontaneous and leguminous strips), (3) integrated (combinations of no-tillage with spontaneous vegetation and leguminous strips), and (4) conventional tillage. The olive yield responses to each production system were evaluated, and the selected physico-chemical soil properties (pH, bulk density, soil organic carbon, cation exchange capacity, and total N, P, and K), soil enzymes (β-glucosidase, protease, dehydrogenase, and phosphatase activities), and soil-microbial biomass C and N were monitored. Throughout the study period, the erosion rates for organic, conservation, integrated, and conventional systems averaged 0.70, 2.10, 1.52, and 3.25 t ha−1 year−1 with runoff of 5.8, 6.3, 11.9, and 17.6 mm year−1, respectively. The mean olive yield was not significantly affected by the production system applied, being 2.43, 2.10, 2.04, and 2.11 t ha−1 year−1 for integrated, organic, conservation, and conventional, respectively. Here, we show a substantial improvement in soil health restoration using the organic rather than a conventional system. Our findings suggest that sustainable cropping systems on hillslopes integrating a blend between organic and conventional doctrines better maintain or improve soil ecosystem functioning. This study highlights a balanced design for an integrated production system for rainfed olive orchards that can maintain productivity while suitably encouraging environmental quality and ecosystem services.

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 specie...

Land degradation, singularly water erosion, is presently the main challenge for the agriculture of the Mediterranean basin. The combination of increasingly frequent extreme rainfall events and conventional farming practices coupled with steep slopes, poor soil structure and pauper plant cover are the elements that explain the development of water-driven soil erosion. The rainfed fruit crops with conventional practices register soil erosion values much higher than soil formation rates, affecting crop productivity. That is, runoff and soil losses are especially important in arid and semi-arid areas of the Mediterranean zones, where both these natural resources are the limiting factors for successful development and productivity of agroecosystems. Moreover, the forecasts for this region anticipate a more significant water shortage in the coming years with a possible severe impact on crop production. In this context, the use of soil and water conservation systems at wider scale are needed to reduce erosion and runoff, to increase the availability of water and plant nutrients, to avoid soil degradation and improve soil productivity. Because these are critical aspects for the economic and environmental sustainability of agricultural systems, especially in hilly areas. This chapter presents and discusses the advantages of conservation agriculture against conventional practices in rainfed fruit crops in terms of soil and water conservation.

The demand for aromatic and medicinal plants (AMPs) is growing worldwide, and most of them are from the wild collection. Today there is a consensus that for industrial purposes the AMPs must be cultivated. Many studies have shown the importance of the collection strategy used to guarantee the plant regeneration, and soil protection against erosion process in mountainous areas in the Mediterranean region. In this work, during three-year monitoring period we compared in four AMPs two harvest strategies by cutting biomass in 25% (BHI25) and 50% (BHI50) of oregano (Origanum bastetanum L.), lavender (Lavandula lanata L.); sage (Salvia lavandulifolia V.); and santolina (Santolina rosmarinifolia L.) in order to assess their effect on essential-oil content, and to be consistent with both plant and soil conservation in Mediterranean steeply sloping areas. The experimental plots were located in Lanjarón (Granada, SE Spain), on a 20% slope. According to the findings the strategy BHI50 of fresh herb of oregano, lavender, sage, and santolina produced essential-oil yield of 13.2 ± 1.74, 17.3 ± 1.69, 9.7 ± 5.21, and 10.8 ± 2.00 L·ha-1, respectively. Since significant differences were found between BHI25 and BHI50 strategies for harvest and distillation of aromatic plants, we recommend a rational harvest, leaving the 50% of the plant biomass in the field to avoid the soil degradation. In addition, with this rational harvest strategy encourages the sustainable AMP cultivation without significant alterations for essential-oil yields, and at the same time guaranteeing the regrowth, and conservation of them in its habitat. Therefore, encouragement local decision-making measures regarding environmental compatibility, social acceptability and economic viability in land use and management will be crucial. Otherwise, the inappropriate harvest of aromatic shrubs in mountain areas compromises land conservation.

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 the subtropical fruit cultivation in the study area. Thus, it is possible to mitigate the impact of subtropical farming on terraces by adopting sustainable measures for soil and water conservation.

Severe climatic events combining water scarcity and droughts are predicted to increase in intensity, frequency, and geographic extent as a result climate change. To grow crops successfully in this adverse scenario, farmers will need to adjust to less available water. The application of efficient water-management strategies such as deficit irrigation is a key element to increase agricultural water productivity in areas affected by water scarcity. This is the case for subtropical Mediterranean farming, particularly terraced mango ( Mangifera indica L.) orchards in southeast Spain. In this chapter we have described that the conventionally applied irrigation (100% ET C ) could be reduced in order to maximize productivity and promote water-saving programs. That is, the highest yield and water-use efficiency were attained by reducing the ET C to 50%, and thus the greatest volumes of water did not increase fruit yield. However, the fully irrigated trees produced the greatest fruit length, width, and weight. In addition, the largest size of the tree was recorded with this treatment, so that the extra irrigation water under 100% ET C was invested in vegetative growth rather than in fruit yield. Consequently, the deficit irrigation at 50% of ET C should be adopted as the most appropriate strategy for achieving sustainable water management under a water-scarcity scenario in subtropical Mediterranean environment.

In this chapter, we present a review of irrigation requirements, water-deficit irrigation techniques, and the main physiological parameters used to determine water status in avocado ( Persea americana Mill.). From our review, only a few trials have been performed under the conditions of a subtropical Mediterranean area. In particular, SE Spain (Granada and Malaga provinces) has irrigated avocado orchards spread widely along the Mediterranean coast, where several advantages related to favorable climate and location make Spain the only European avocado producer. However, limited water resources worsened by climate change exacerbate water scarcity and exert greater pressure on a territory under a dry Mediterranean climate, making further research urgent to boost water use efficiency. Therefore sustainable irrigation programs for this crop become key in this water shortage scenario, which needs the support of transfer and teaching as well as the collaboration of governmental institutions, irrigation associations, and farmers.

La descomposición de la hojarasca es una de las principales vías de consumo de energía en un ecosistema y uno de los pilares básicos en el ciclo de nutrientes. Por otro lado, en las últimas décadas, los cultivos subtropicales se han expandido de forma considerable en la costa de Granada (sureste de España). Para evaluar dichos ciclos se llevó a cabo un ensayo con bolsas utilizando para ello hojas de mango (Mangifera indica L.), chirimoyo (Annona cherimola Mill.), aguacate (Persea americana Mill.) y níspero (Eriobotrya japonica L.). El objetivo de este trabajo fue realizar un seguimiento de la dinámica de descomposición de las hojarascas producidas por el mango, aguacate, chirimoyo y níspero, y de la evolución de su contenido en carbono y nitrógeno en condiciones de clima mediterráneo subtropical. Las bolsas fueron enterradas y se recuperaron cada cierto tiempo para evaluar la concentración de carbono y nitrógeno, así como la pérdida de masa en cada una de ellas. Los resultados de este estudio mostraron de forma evidente que los agricultores pueden beneficiarse del conocimiento de la dinámica de nutrientes en hojarasca para mejorar la materia orgánica en el suelo a largo plazo y la incorporación de nitrógeno. En este sentido, el níspero y el mango mostraron las mayores tasas de acumulación de nitrógeno y, por lo tanto, la biomasa de estas especies podría ser utilizada como enmiendas de tipo orgánico a largo plazo. Por el contrario, el chirimoyo acumuló mayores cantidades de carbono que el resto de los cultivos estudiados.