Semiarid Mediterranean Conditions Research Articles

Shoot and Root Decomposition from Different Cropping Systems Under Semiarid Mediterranean Conditions

Improving the management of crop residues is essential for water and soil conservation and for increasing soil carbon (C) and nitrogen (N) levels in dryland agroecosystems. The main objective of the study was to evaluate the decomposition dynamics and C and N released from crop residues from different cropping systems under semiarid Mediterranean conditions. A litterbag experiment was conducted from July of 2020 to June of 2021 to examine the shoot and root decomposition dynamics of different cropping systems; the following systems were selected: V(B), vetch (Vicia sativa) residue decomposition in a barley crop; B(V), barley (Hordeum vulgare L.) residue decomposition in a vetch crop; P(B), pea (Pisum sativum) residue decomposition in a barley crop; B(P), barley residue decomposition in a pea crop; and B(B), barley residue decomposition in a barley crop. After 48 weeks of decomposition, a 45% and 60% of residues mass remaining (MR) was found corresponding to vetch and pea shoot residues respectively, whilst barley MR ranged 77–87% depending on the cropping system. In root residues, the mass decay from legume residues (40–45%) was higher compared to barley residues (17–29%). Exponential decay and linear models explained the residue decomposition observed in our study conditions. Residues C to N ratio and edaphoclimatic conditions played a major role controlling the decomposition. Residue decomposition and C and N release dynamics from different crop residues need to be considered for a transition to more sustainable agroecosystems under Mediterranean semiarid conditions.

Species, Cultivar and Seasonal Effects on Nodulation and Nitrogen Utilization of Spring Mediterranean Grain Legumes

Information on nitrogen economy of grain legumes during seed filling is critical for their sustainable cultivation in rainfed agroecosystems, but a comparable assessment of different legumes under the same growth conditions is lacking. The purpose of this study was to examine species, cultivar and seasonal effects on nodulation and nitrogen accumulation, remobilization, and utilization. Five grain legumes [common vetch (Vicia sativa L.), red pea (Lathyrus cicera L.), lentil (Lens culinaris Medik), chickpea (Cicer arietinum L.), and field pea (Pisum sativum L.)], each represented by two cultivars, were grown for two years in a semiarid Mediterranean environment. There were considerable environmentally induced differences among species in nodulation, with chickpea maintaining a sufficient number of nodules (16 nodules plant‒1) and nodule dry weight (57 mg plant‒1) even in the drier year (2015). Pre-podding nitrogen accumulation varied among species, particularly in the wetter year (2014). Nitrogen translocation from vegetative parts to seeds was correlated with pre-podding nitrogen accumulation (r = 0.99, P < 0.01 in 2014 and r = 0.98, P < 0.01 in 2015). Interspecific differences in nitrogen translocation efficiency were enlarged under drought, with red pea exhibiting the highest (84%) and lentil the lowest value (72%). Chickpea produced the highest seed nitrogen accumulation in both years and had the highest nitrogen utilization efficiency (21 kg seeds per kg N) the drier year. Nitrogen utilization efficiency was positively correlated with nitrogen harvest index and negatively with nitrogen concentration in vegetative parts at maturity. Most trait differences were less evident within species than between species. Overall, chickpea was found to outperform other legumes in semiarid Mediterranean conditions in terms of nitrogen accumulation in seeds and nitrogen utilization efficiency.

Pre-anthesis spike growth dynamics and its association to yield components among elite bread wheat cultivars (Triticum aestivum L. spp.) under Mediterranean climate

Wheat (Triticum spp.) grain yield (GY) is highly associated with grain number per unit area (GN m-2). Biomass accumulation and partitioning are essential to understand pre-anthesis spike growth dynamics which determines spike dry matter at anthesis (SDMa) - a GN determinant. Spike growth takes place during the stem elongation period (SE), from terminal spikelet to anthesis, following leaf and spikelet initiation (LS) from sowing to terminal spikelet. In this study, bread wheat cultivars were examined under Mediterranean semi-arid conditions to determine (i) the varietal differences in pre-anthesis phase duration, (ii) whether this variability influences biomass partitioning and spike-related traits, and (iii) to what extent, the genotypic variations in pre-anthesis phase duration and spike growth are associated with yield components. A panel of Israeli commercial bread wheat cultivars were grown in the field during 2016–17 (three environments) and 2017–18 (two environments) and characterized for pre-anthesis phases, floral conditions and spike fertility via histological measurements; spike traits, dry matter accumulation, partitioning at anthesis and maturity and for yield components. Significant variability in the timing of pre-anthesis phases was detected within the tested panel for both LS and SE phases. LS duration was positively associated with growing degree days (GDD) to anthesis across environments (0.72–0.90) while variation in SE was related with differences in GDD to anthesis but to a lesser extent and not in all environments (0.47–0.79). In addition, LS duration, and occasionally SE, were favourably related with a higher dry matter of fertile florets spike-1 (at anthesis) and SDM (at both anthesis and maturity). Principal component analysis (PCA) clearly separates environments and to a lesser extent cultivars within each environment. Two cultivar pairs 'Zahir-Yuval' and 'Negev-Gedera', which flowered concurrently, showed significant differences in the durations of LS and SE phases across most of the environments. Longer LS, in cultivars Zahir and Negev, exhibited increased spikelets spike-1, whereas longer SE (e.g., in Yuval and Gedera) enhanced spike fertility through improving the survival rate of floret primordia (FSR%) of central spikelets. However, there was a trade-off for FSR at the proximal and distal spike portions, resulting in lower grain set (%) leading to reduction of final GN (or GY) in cultivars with longer SE. In the tested panel and under our environmental conditions characterized by growing cycle and Mediterranean climate, the duration of both LS and SE contribute to spike fertility, but LS duration seemed a stronger driver than SE for GN and yield enhancement. Our results highlight the importance of pre-anthesis phases, especially the role of LS in wheat yield increment during the short growing cycle. The varietal combination with variable LS and SE duration could be implemented in breeding pipelines and used as pre-breeding materials for GN improvement. Furthermore, the findings will encourage pre-anthesis traits adoption in Mediterranean bread wheat future breeding programs.

Behavior assessment of some Triticale (Triticosecale wittmack) Genotypes under Mediterranean Semi-arid Conditions

Background: In Mediterranean climate, drought and heat stress are the main constraints for cereal production under rainfed conditions. In these conditions, the selection of suitable genotypes is crucial to improve production. Methods: 20 advanced triticale lines were evaluated under semi-arid conditions in Setif (Algeria) during the 2019/2020 season using agronomic, morphological and physiological traits. Result: The results obtained showed that lines with higher numbers of tillers, spikes, grains per spike, leaf area index and leaf chlorophyll content produced more grains and used water more efficiently when faced to drought and heat stress in post-anthesis phase. Also, high chlorophyll content, high relative water content and maintenance of cell membrane stability delayed senescence and extended the grain filling stage. Relative water content was also related to high grain protein content. This work evaluated this set of triticale lines and identified traits positively related to grain yield and water use efficiency in Mediterranean region.

The Adaptability of Cities to Climate Change: Evidence from Cities’ Redesign towards Mitigating the UHI Effect

The urban heat island effect can be studied through satellite imaging, field measurements, or analytical and numerical tools. However, the latter methods are considered more comprehensive due to the complexity of the built environment and the large quantity of data required for an adequate analysis. This study aims to investigate the extent to which specific urban bioclimatic design concepts and strategies affect the urban heat island intensity in Mediterranean semi-arid environmental conditions, classified as subtropical. The case study site chosen was Kaimakli, an urban district in Nicosia, Cyprus, known for high urban heat island intensities due to its location and rapid growth characterized by more impervious materials and less green vegetation. The analysis of the specific site considers parameters such as urban density, vegetation, soil sealing effect, building age and materials, land coverage ratio, and orientation. A design scenario consisting of three mitigation policies of different building types, heights, and vegetated types was developed and investigated. The study found that under semi-arid conditions, the use of extensive vegetation in an urban block of a 200 × 200 m² area and the reduction of the built area by about 10% resulted in an air temperature reduction of 1.5 °C during the summer solstice at 3:00 pm. These findings quantify the impact of specific urban heat island mitigation practices on decreasing the intensity of the effect under subtropical climatic conditions. This study provides valuable insights into the potential of specific urban bioclimatic design concepts and strategies to mitigate the urban heat island effect. The use of extensive vegetation and a reduction in the built area have been shown to be effective in reducing air temperatures, which can have significant implications for public health, energy consumption, and overall urban sustainability.

Physiological Influence of Water Stress Conditions on Novel HLB-Tolerant Citrus Rootstocks

Citrus are one of the most relevant fruit crops in the Mediterranean basin, which is the second-highest citrus-growing region in the world. However, these crops are mainly grown under Mediterranean semi-arid conditions, characterized by long periods of drought and torrential rain. In this work, we have assessed the response of three promising HLB-tolerant citrus rootstocks (Orange-14, UFR-1, and B11R3T27) to the application of four water stress conditions (Control, Mild water stress, Drought, and Flooding), comparing them with Carrizo citrange. Aerial plant symptoms were recorded during the experimental period, whereas plant water parameters, including stomatal conductance, leaf water potential, and relative water content, were obtained at the end of the assay. For all assessed rootstocks and variables, drought treatment was the most limiting factor, with Carrizo citrange being the most suitable rootstock under this condition. Flooding was the second restrictive treatment, in which UFR-1 was the least affected rootstock. Mid-water stress with 50% water requirements did not differ from the Control treatment, which can help save water resources in semi-arid regions. This information can be helpful for the citrus industry to increase the efficiency of citrus crops subject to water stress in semi-arid regions.

Irrigation and Phosphorus Management of Alfalfa Under Semi-Arid Conditions

The frequency of irrigation and deficit irrigation management are drawing attention because water resources are becoming limited year by year, especially in the last decade. Besides, the rate and application time of P fertilization gained more importance just after the researchers found out it is more effective than N-fertilizing for alfalfa cultivation. This study aimed to determine the effects of different irrigation managements (seasonal deficit, intervals of 5, 7, and 9 days), phosphorus application season (autumn and spring), and the rate of P fertilizer (0, 30, 60, 90 kg ha-1) on the yield and forage quality of alfalfa. The experiment was conducted in the 2019-2020 years, which was the 3rd and the 4th years of alfalfa respectively, under semi-arid Mediterranean conditions. The stand height and fiber content (NDF) were higher in the autumn application. However, forage contained more nitrogen in the spring application. A higher amount of water (800 mm) with higher irrigation frequency (5 days – I5d) caused a reduction in yield due to water excess. The yield was the highest (21.34 t ha-1) and the forage quality was better in 448 mm water application with 9 days intervals (I9d). Seasonal deficit water management caused a significant loss in yield and quality. Nevertheless, 18.04 t ha-1 dry matter yield with 24.05 % CP content was recorded at seasonal deficit water management. P fertilization increased the yield and forage quality. The yield was the highest (20.23 t ha-1) at the rate of 90 kg ha-1 P fertilizer, but yield and forage quality characteristics were similar between 30, 60, and 90 kg ha-1 P. The results showed that P fertilization could be done in both autumn and spring at the rate of 30 kg ha-1 and 448 mm water could be applied at 9 days intervals for fulfilling performance under semi-arid Mediterranean conditions. When water resources are very scarce, the seasonal water deficit should be applied, especially in late summer.

Effects of wildfire and post-fire salvage logging on rainsplash erosion in a semi-arid pine forest of Central Eastern Spain

Rainsplash erosion on forested hillslopes can be increased by both wildfires and post-fire salvage logging, especially under semi-arid Mediterranean conditions. However, few studies have compared rainsplash erosion among forest sites impacted by logging to other forest areas. To fill this gap, this study has evaluated surface runoff and soil erosion in a burnt and logged (manually or mechanically) pine forest of Central-Eastern Spain under simulated rainfall and compared it to unlogged and unburnt plots. Compared to the unburnt plots, surface runoff significantly increased (over 150%) in logged areas, with a peak of 220% on the areas directly subjected to logging machinery. Peak runoff was substantially increased by fire (+130%) and less by logging (+8. Soil loss due to rainsplash erosion was about 235% (manual logging) to 750% (mechanical logging) higher compared to the unburnt plots. Wildfire exerted a much higher soil disturbance compared to salvage logging, with a soil hydrological response that can be up to an order of magnitude higher. The increased runoff and erosion rates in response to wildfire and logging were ascribed to soil compaction, which increased on average 60% on logged plots as well as to the removal of vegetation cover (−80%), whereas soil roughness played a minor role. From these results, we suggest using lightweight machinery in burnt soils, to reduce surface runoff and erosion. The possibility of building contour felled log debris using the burnt wood may also be considered, in order to retain the eroded sediments.

The combination of crop diversification and no tillage enhances key soil quality parameters related to soil functioning without compromising crop yields in a low-input rainfed almond orchard under semiarid Mediterranean conditions

Soils provide key ecosystem services and are crucial to combat climate change. Agriculture provides important ecosystem services but also causes negative environmental effects depending on agricultural management. In this regard, crop diversification is a promising sustainable land management strategy to combat soil erosion and degradation, mitigate climate change and ensure food security. Here, we assess the combined short-term effects of crop diversification and no tillage on several key soil physico-chemical parameters related to soil functioning as well as on crop yields in a rainfed almond (Prunus dulcis Mill.) orchard under semiarid Mediterranean conditions. Almond trees were inter-cropped with Capparis spinosa L. (caper) or Thymus hyemalis Lange (winter thyme) and compared with the almond monocrop system. The experimental design consisted of three plots in a randomized-block design, with three replicates for each crop management treatment (almond monocrop, almond inter-cropped with caper, and almond inter-cropped with winter thyme). Along with crop yields, the combined effects of crop diversification and no tillage on a range of soil quality and health indicators including soil physical (bulk density, aggregate stability, water retention and availability) and chemical (total and particulate organic carbon and nitrogen, ammonium and nitrate content, available macro- and micro-nutrients) properties were monitored in the topsoil and subsoil (at 0–10 and 10–30 cm depth, respectively) one and three years from establishment. Resultsfrom this study indicate that soil water retention capacity and water availability for plants were enhanced in both crop diversification systems after three years from their implementation at 0–30 cm depth. Likewise, improvements in particulate organic carbon and available N were observed in the subsoil of both crop diversifications. Crop diversification did not significantly affect the main crop yields, highlighting that crop diversification can be a promising sustainable management practice for improving soil health without compromising food security under semiarid Mediterranean conditions. Indeed, land equivalent ratios (LER) of almond trees inter-cropped with winter thyme were higher than those of their respective monocrop systems for two consecutive years, indicating that inter-cropping with aromatics can improve the productivity of rainfed woody monocrop systems under semiarid conditions. Our results emphasize the importance of selecting an appropriate secondary crop that ensures a permanent soil cover while contributes to enhance the agroecosystem productivity from the first year of establishment onwards to off-set plausible lower yields from the main crop. In this regard, preliminary assessments on soil condition and crop nutrient requirements are encouraged before designing and implementing a crop diversification in these low-input cropping systems.Likewise, long-term studies are needed to provide evidence on the stability of the production of diversified crop management, particularly in these low-input cropping systems under harsh environmental conditions.

A GIS‐based multicriteria decision analysis to reduce riparian vegetation hydrogeological risk and to quantify harvested biomass (Giant reed) for energetic retrieval

The vegetation development in riverbeds creates obstructions to the regular water flow with the flooding hydraulic risk increase. Giant reed (GR) (Arundo donax L.) is one of the most successful invasive species of riparian ecosystems in Mediterranean semi-arid climate conditions, with significant public administrations costs for its removal and disposal. At the meantime, due to its high biomass yield and adaption capacity to several conditions, GR is a very promising no-food crop to produce biogas by the anaerobic digestion (AD). The research activity provides for the involvement of territories belonging to the inner areas of Sicily, especially Calatino one, in which the SIMBIOSI Consortium operates an AD plant fed with agricultural by-products from other close agro-industrial companies. The aim of the study was to map and to quantify the actual spatial distribution of GR in watercourses embankments through Remote Sensing (RS) techniques applied in a Geographic Information System (GIS) environment. In this regard, a method based on the automatic supervised classification, was applied on three different combinations of spectral bands (True Color Image – TCI; Near-Infrared, Green and Blue – NGB; Vegetation Red Edge – VRE) of Sentinel-2 satellite images related to the summer season (11th August 2019), with the aim of identifying the most suitable classification to map the GR. The results showed that the VRE composition is the most accurate combination of spectral bands for the identification of GR, followed by the NGB image. The worst performance was obtained by using the TCI combination. A further elaboration was carried out combining the three classified images, in order to obtain a more accurate localization and quantification of GR. The final thematic map allowed to correctly classify GR for the 46 % of the cases, with an overall accuracy of 85.02 % and a high Kappa Coefficient of Agreement value equal to 0.81. Finally, the surface covered by GR in the study area (computed in the GIS environment) was about 2 km2 and the estimated GR biomass, available for the biomethane production, obtainable from watercourses embankments maintenance interventions would amount to about 11,780 tons year−1. The study could contribute to the development of a watercourses maintenance plan with the aim to reduce the risk of streams flooding in valley areas and at intersections with infrastructure works. Furthermore, the proposed methodology can be used by stakeholders in marginal areas, for the watercourses management, offsetting its costs through the energy use of the collected biomass.

Intercropping legumes and cereals increases resource use efficiency and crop productivity in low phosphorus soils under semi-arid Mediterranean conditions

ABSTRACT Intercropping ensures multiple benefits like enhancement of yield, environmental security, production sustainability, and greater ecosystem services. In order to better understand how mixed crop cultures mitigate stressful conditions, this study aims to highlight the beneficial effect of the intercropping legume–cereal in enhancing nutrient uptake for plant growth and productivity in low phosphorus (P) soils. To address this question, faba bean (Vicia faba L. cv. Sidi Aich) and barley (Hordeum vulgare L. cv. Rihane 3) were grown as sole- and inter-crops over two growing seasons in 2017 and 2018 in a northern Algerian agro-ecosystem with a semiarid Mediterranean climate. The results showed that the plant growth and nodulation were significantly increased by 18% and 32%, respectively, for intercropping than for sole cropping and so more in 2018 compared to 2017. Moreover, grain yield and resource use efficiency (N and P) were significantly improved, as indicated by higher land equivalent ratio (LER > 1) in intercropping over sole cropping treatments. Also, the P and N concentrations measured in the rhizosphere were increased compared to bulk soil and even more so in the rhizosphere of intercropped species over two seasons. Our findings suggest that intercropping cereals with legumes may achieve high crop productivity and land use efficiency at reduced input levels.

Critical nitrogen dilution curve and dry matter production parameters for several Mediterranean vegetables

• Twelve typical Mediterranean vegetables were studied. • The average and critical nitrogen dilution curve coefficients were obtained. • The dry/fresh matter ratios and harvest indexes were also obtained. • There were no differences between the average and critical dilution curves. • Differences of dry matter yield did not affect any of the parameters. Inadequate nitrogen fertilizing practices lead to low nitrogen uptake efficiency (NUE), which increases water NO 3 − pollution, as well as N 2 O emissions to the atmosphere. In order to increase the NUE and decrease the N losses as NO 3 − and N 2 O from the soil-plant system, accurate data about optimum crop N concentrations and dry matter production throughout the growing season are still needed for many vegetables typically grown under Mediterranean climate. For this reason, several N fertilization trials were set up for globe artichoke, carrot, cauliflower, chard, chinese cabbage, early potato, leek, lettuce, onion, red cabbage, romanesco, and spinach, under the semiarid Mediterranean conditions of the Valencian Community (Eastern Spain) during several years. The fresh and dry matter weight ( W ), as well as the nitrogen concentration in the dry matter (% N ) in both the marketable and non-marketable crop parts, was measured between 3 and 7 times throughout their respective growing seasons. The a and b coefficients of the average N dilution curve (% N = a W − b ), for which all % N and W data were used, and the critical N dilution curve (% N c = a W c − b ), for which only the minimun % N for maximum W data were used if available, in addition to the dry/fresh yield matter ratio ( DM ) and the harvest index ( HI ), were calculated for all these crops. No significant differences were observed between the average and critical N dilution curve coefficients in this work. Interestingly, the coefficients of both N dilution curves differed from the ones found in the literature with the exception of those obtained for similar cultivars, e.g., early potatoes, and under similar climatic conditions, i.e., Mediterranean. Besides, there were neither differences of DM and HI among the several N fertilization treatments. Therefore, due to the absence of changes in the N dilution curve and dry matter production coefficients for the different N supplies, all these parameters were estimated on the basis of the whole dataset, i.e., regardless of the N input. The use of the critical nitrogen dilution curve coefficients and dry matter production parameters presented in this work should contribute to better fit the N fertilizer additions to N demands of these vegetables under Mediterranean conditions, mainly, by their use through simulation models. Therefore, the NUE in horticulture should increase and the N losses as NO 3 − to inland and sea waters in these environments, and as N 2 O to the atmosphere should decrease.

Greenhouse gas emissions associated to sprinkler-irrigated alfalfa under semi-arid Mediterranean conditions

Aim of the study: Alfalfa is one the most important forage legume crop worldwide but little information is available regarding to greenhouse gas emissions (GHG) under Mediterranean sprinkler-irrigated conditions. Area of study: Middle Ebro valley, Spain Materials and methods: The GHG emissions during two alfalfa growing periods (4th and 5th stands) were evaluated using both the static method chambers and two automatic chambers coupled with a photoacoustic equipment that measured short-term gas emissions. Main results: Year-average CH4 fluxes were -0.71 g C ha-1 day-1, generally no significantly different from zero. Year-average N2O flux was 3.96 g N ha-1 day-1 with higher fluxes associated to some specific large rainfall or irrigation events. Average cumulative emissions of 865 g N ha-1 year-1 were found. We found short-term peaks of N2O (up to 160 g N ha-1 day-1) associated with high values of soil water filled pore space (WFPS) that can go unnoticed using the static chamber procedure. In spite of the higher soil NO3‾ concentration in the alfalfa-precedent field compared to the maize-precedent field, no significant differences in cumulative N2O emissions were observed in the two-month period after alfalfa or maize residues incorporation. Research highlights: Low GHG emissions were found in an irrigated alfalfa crop compared to N-fertilized crops but a deeper knowledge of the limiting factors of denitrification observed during some anoxic events (WFPS&gt;90%) is necessary to properly quantify N2O emissions in irrigated alfalfa.

Crop Diversification Effects on Soil Aggregation and Aggregate-Associated Carbon and Nitrogen in Short-Term Rainfed Olive Groves under Semiarid Mediterranean Conditions

Soil particle aggregation and their associated carbon (C) and nitrogen (N) content can provide valuable diagnostic indicators of changes in soil properties in response to the implementation of different agricultural management practices. In this sense, there is limited knowledge regarding the impact of intercropping on soil organic carbon (SOC) and total nitrogen (TN) pools in aggregates. This study aimed to evaluate the short-term effect (4 years) of three crop diversifications in rainfed olive orchards on soil aggregation, SOC and TN concentration and SOC stocks (SOC-S) under semi-arid Mediterranean conditions. Olive orchards were diversified with Crocus sativus (D-S), Vicia sativa and Avena sativa in rotation (D-O) and Lavandula x intermedia (D-L) and compared with monocropping system (CT). Soil samples were collected at two depths (0–10 and 10–30 cm) and analysed for soil aggregate mass, SOC and TN content in aggregate-size fractions obtained by the wet-sieving method. Changes caused by crop diversifications on SOC-S were also determined. Overall, after 4 years, a reduction in aggregation values was observed. However, D-S increased the macroaggregates (&gt;250 μm) percentage, Mean Weigh Diameter values, and Geometric Mean Value in the 0–10 cm. Across treatments, aggregate-associated C in 0–10 cm was higher in the D-S treatment, while in the 10–30 cm soil layer, the greatest values were found in CT. Regarding the SOC-S, after 4 years, significant losses were recorded under CT management in 0–10 cm (−1.21 Mg ha−1) and 10–30 cm (−0.84 Mg ha−1), while D-O and D-L showed similar values to those obtained at the beginning of the study. The highest increases in SOC-S were found in D-S, with an increase of 5.88% in the 0–10 cm and 14.47% in the 10–30 cm. Our results showed the high potential of the diversified cropping system to increase soil stability and SOC sequestration.

Crop Diversification Effects on Soil Aggregation and Aggregate-Associated Carbon and Nitrogen in Short-Term Rainfed Olive Groves under SemiaridMediterranean Conditions

Crop Diversification Effects on Soil Aggregation and Aggregate-Associated Carbon and Nitrogen in Short-Term Rainfed Olive Groves under SemiaridMediterranean Conditions

Effects of post-fire mulching with straw and wood chips on soil hydrology in pine forests under Mediterranean conditions

Mulching is one of the most common post-fire management techniques, which has been widely studied at the global scale. However, more research is needed on the hydrological effects of mulching in forest ecosystems under Mediterranean semi-arid conditions. This study has evaluated water infiltration, surface runoff and soil loss using a portable rainfall simulator in Central-Eastern Spain after post-fire treatments. In this area, a large wildfire recently affected a pine forest, and the burned soil was mulched using wheat straw (dose of 0.3 kg/m2) or wood chips (2 kg/m2) on plots with two different slopes (about 30%, lower slope, and 50%, higher slope). The study has shown that the soil condition (burned control vs. soils mulched with straw or wood chips) and slope (lower vs. higher) did not significantly influence the water infiltration. However, the mean infiltration of the soils mulched with straw were higher (+40% and + 17%, respectively) compared to both the control and the plots mulched with wood chips. Moreover, lower surface runoff (−23%) was measured in the mulched soils compared to the control plots. The soil mulching with straw was more effective at decreasing the runoff coefficient (−31%) compared to plots treated with wood chips (−18%) and the control areas. Soil loss was significantly lower in plots treated using straw (−87% compared to the burned and not treated soils) compared to wood chips (−54%). Peaks of 90–95% of reduction in the soil loss were even recorded in the steeper soils. Finally, we suggest the application of wheat straw rather than wood chips, since the wheat straw mulch material provides a higher soil cover (on average 73% against 48% of wood chips) and therefore is more indicated to reduce the hydrological response in burned soils, as confirmed by the lower runoff (in the average − 16%) and erosion (−73%) measured in this experiment on both gentler and steeper soils.

Physiological and Agronomical Responses of ‘Vairo’ Almond and ‘Big Top’ Nectarine Cultivars Grafted onto Different Prunus Rootstocks and Grown under Semiarid Mediterranean Conditions

Two trials were conducted under Mediterranean conditions to monitor several physiological indicators before harvest (leaf chlorophyll concentration, quantum yield of photosystem II electron transport, stem water potential, and stomatal conductance) and some agronomic performance parameters before and at harvest (vigor, fruit growth, fruit size, fruit weight, and yield), of ‘Vairo’ almond and ‘Big Top’ nectarine cultivars grafted onto eight Prunus rootstocks, six of which are common in both cultivars. For both ‘Vairo’ almond and ‘Big Top’ nectarine cultivars, factors including rootstock, date, and the interaction between rootstock and date, from fruit set to harvest were evaluated. Significantly affected were certain physiological and agronomical traits which were evaluated before harvest, with stem water potential being the parameter affected by interaction in both cultivars. In fact, the stem water potential presented low levels in Rootpac-20 and high levels in Rootpac-40 for both cultivars. With regard to the other physiological traits evaluated during the growing period, changes in stomatal conductance were observed in ‘Vairo’, but not in ‘Big Top’. Comparing rootstocks throughout the season, Rootpac-40 and IRTA-1 exhibited the highest stomatal conductance values, whereas the lowest was observed in Rootpac-R; Rootpac-20 and Ishtara also presented low values. Regarding agronomical traits at harvest, GF-677 and IRTA-1 produced high yields for ‘Vairo’ almond cultivar, whereas Rootpac-40 and Ishtara performed better with ‘Big Top’ nectarine cultivar.

Effects of organic and inorganic fertilization on growth and yield of Physalis peruviana L. crop under Mediterranean conditions

Physalis peruviana L. is an Andean Solanaceae fruit crop with great nutraceutical qualities, potential health benefits and adaptability to Mediterranean climates. In the current study, a first approach on the effect of organic and inorganic fertilization on P. peruviana crop under Mediterranean semi-arid conditions was performed. A field experiment was laid out according to a completely randomized design, with three replicates and three fertilization treatments [untreated (control), organic fertilization (biocyclic humus soil) and inorganic fertilization (inorganic fertilizer 40-0-0+14.5 SO3)]. Phenological growth stages and their corresponded growing degree days were evaluated. In addition, some growth parameters, fruit yield and yield components were evaluated. The results indicated that the duration of phenological growth stages was in accordance with durations mentioned in tropical climate. The highest branches number per plant (24.4), leaf area per plant (1997.3 cm2), fruit number per plant (41.52), fruit yield (7.51 t ha-1) and average fruit weight (5.32 g) were found in inorganic fertilization plots, whereas the highest plant height (44.15 g) and fruit diameter (12.52 mm) were recorded under organic fertilization; however, the differences between the organic and inorganic fertilization were not statistically significant. In terms of dry weight per plant, there were significant differences among the fertilization treatment with the values obtained under inorganic fertilization (81.24 g). To sum up, P. peruviana showed satisfying adaptability under Mediterranean climate conditions and has great potential in becoming an alternative cultivation for small and medium producers of Mediterranean countries. In addition, the results indicated that organic fertilization (with biocyclic humus soil) should be considered as an alternative to inorganic fertilizers for P. peruviana production.

Modeling Influence of Soil Properties in Different Gradients of Soil Moisture: The Case of the Valencia Anchor Station Validation Site, Spain

The prediction of spatial and temporal variation of soil water content brings numerous benefits in the studies of soil. However, it requires a considerable number of covariates to be included in the study, complicating the analysis. Integrated nested Laplace approximations (INLA) with stochastic partial differential equation (SPDE) methodology is a possible approach that allows the inclusion of covariates in an easy way. The current study has been conducted using INLA-SPDE to study soil moisture in the area of the Valencia Anchor Station (VAS), soil moisture validation site for the European Space Agency SMOS (Soil Moisture and Ocean Salinity). The data used were collected in a typical ecosystem of the semiarid Mediterranean conditions, subdivided into physio-hydrological units (SMOS units) which presents a certain degree of internal uniformity with respect to hydrological parameters and capture the spatial and temporal variation of soil moisture at the local fine scale. The paper advances the knowledge of the influence of hydrodynamic properties on VAS soil moisture (texture, porosity/bulk density and soil organic matter and land use). With the goal of understanding the factors that affect the variability of soil moisture in the SMOS pixel (50 km × 50 km), five states of soil moisture are proposed. We observed that the model with all covariates and spatial effect has the lowest DIC value. In addition, the correlation coefficient was close to 1 for the relationship between observed and predicted values. The methodology applied presents the possibility to analyze the significance of different covariates having spatial and temporal effects. This process is substantially faster and more effective than traditional kriging. The findings of this study demonstrate an advancement in that framework, demonstrating that it is faster than previous methodologies, provides significance of individual covariates, is reproducible, and is easy to compare with models.

Effect of progressive irrigation water reductions on super-high-density olive orchards according to different scarcity scenarios

The cultivation of super-high-density (SHD) olive orchards in the Mediterranean Basin usually faces drought events due especially to low precipitation, high temperature and solar radiation in summer. Hence regulated deficit irrigation (RDI) strategies can be a useful tool for irrigation management to limit yield loss. Therefore, this work aimed to find the most suitable RDI strategy by placing special emphasis on phase II of fruit growth for SHD olive orchards irrigated below theoretical water requirements. Four irrigation strategies were defined according to different water availability scenarios: fully-irrigated, RDI1, RDI2 and RDI3, scaled to respectively supply 450, 350, 250 and 150 mm year-1. Tree water relations, trunk growth, fruit and oil yields, were evaluated. The study was carried out for 5 years in an ‘Arbequina’ commercial orchard (1667 trees ha-1) in Villena, Alicante (Spain). The main results showed that ‘Arbequina’ tree irrigation water productivity (both olive and oil) gradually increased as irrigation dose lowered. Olive yield depended heavily on the applied irrigation dose, with the highest olive yield for the Control trees. However, the oil yield in the RDI1 trees was similar to that of the Control trees, but strategies RDI2 and RDI3 reduced yield. All the RDI strategies diminished vegetative development, and RDI2 was the most efficient strategy for resource distribution (olive yield vs. vegetative growth). Therefore based on oil production, vegetative growth and irrigation water savings, RDI1 was the most recommendable irrigation strategy for the Arbequina’ olive trees cultivated in SHD under semi-arid Mediterranean conditions.