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Management practices in the inter-row area of olive orchards are undergoing significant transformations. Current regulations and recommendations are increasingly advocating the implementation of temporary spontaneous cover crops (TSCV) mainly to reduce erosion. Existing research has predominantly focused on evaluating the effectiveness of TSCV in mitigating soil erosion in olive orchards, with limited attention given to carbon (C) cycling, despite the potential of TSCV for contributing to the removal of atmospheric CO 2 and in the reduction of eroded carbon. Moreover, the limited number of studies on the effects of TSCV on C cycling have been confined to a few experimental sites and at the short term. This study aimed to assess the potential of TSCV to enhance carbon sequestration and nitrogen retention in rainfed commercial olive orchards under semi-arid conditions. To achieve this, we evaluated the annual aboveground organic carbon input due to TSCV, as well as the stocks of soil organic (SOC) and inorganic (SIC) carbon and total N (STN) in 24 commercial olive groves with calcareous Regosols and calcium Cambisols as the predominant soil types that have implemented TSCV for at least the last 8 years. These were compared with 24 comparable groves with bare soil (BS). Net aboveground annual carbon and CO 2 fixation of the TSCV averaged 125.7 kg C ha−1 y−1 and 460 kg CO 2 ha−1 y−1, respectively, which are figures relatively low mainly due to the low area covered by the TSCV. After eight years of implementing TSCV, the SOC stocks increased by an average of 2.03 Mg C ha−1 (in the top 30 cm of soil) compared to BS olive orchards. Moreover, SOC content of unprotected (>250 µm) and physically protected (53–250 µm) fractions were 82 and 38 % higher in the TSCV olive farms. Although there was a tendency of lower SIC content in TSCV olive orchards, differences were not significant. The STN content and the potentially mineralizable nitrogen in TSCV farms were on average 26 % and 77 % higher than in BS olive orchards. These findings underscore the potential of TSCV for organic carbon accumulation and nitrogen retention in the soil, contributing to climate change mitigation and soil fertility enhancement. Increasing vegetation coverage and productivity can enhance their effectiveness. • With TSCV on Calcareous Regosols and calcium Cambisols, SOC and STN were 25–26 % higher. • After 8 years of implementing TSCV, there were 2.0 Mg ha−1 (0–30 cm depth) more SOC compared to BS olive orchards. • Unprotected and physically protected C were the SOC fractions which most increased under TSCV. • SIC content tended to be lower under TSCV. • TSCV in olive groves demonstrated to contribute to climate change mitigation and N retention. [ABSTRACT FROM AUTHOR]

Cropland soils are key systems in global carbon budgets due to their high carbon-sequestration potential. It is widely accepted that clays are one of the soil components that have a significant effect on the stabilisation of soil organic carbon (SOC), owing to its surface interactions with organic molecules. However, the identification of the direct effects of clays on SOC stabilization is complicated, mainly due to the difficulty of accurately characterizing the mineralogy of clays, especially phyllosilicates. In this study, the relationships between soil phyllosilicates and functional SOC pools in woodlands and comparable olive groves, under two contrasting management systems (bare soils versus soil under cover crops) and parent materials (calcareous and siliceous), were explored. The total mineralogy of soil and clay fractions and the soil-clay assemblages were analysed through the decomposition of X-ray diffraction patterns, and were then related to four SOC pools. Total and unprotected SOC was higher in olive groves under cover crops, and this was true independent of the parent material, proving the importance of herbaceous covers in SOC sequestration in woody crops. Some significant correlations between clay minerals and SOC fractions were found. Interestingly, mixed-layer content was correlated with the biochemically protected SOC fraction (r = 0.810, p < 0.05), and this was so even when the partial correlation coefficient was calculated (r = 0.761, p < 0.05). According to the partial correlation networks (PCN), four separated clusters of variables were obtained, which joined into only one at fdr < 0.25. The PCNs supported the direct correlation between mixed-layer content, especially those rich in smectite, and the biochemically protected SOC fraction, suggesting that smectite layers may stabilize organic molecules. Since potassium enrichment is higher in the rooted layers of woodland and soils under cover crops, and this increase is related to the collapse of swelling layers, these soils were poorer in smectite phases than the bare soils. This also would explain why the biochemically protected SOC was more abundant in the latter. [ABSTRACT FROM AUTHOR]

Under the Zero pollution action, there is a strong emphasis on promoting management practices that enhance nitrogen (N) cycling to decrease reliance on inorganic N fertilizers and mitigate potential environmental impacts. Olive (Olea europaea L.) groves constitute the dominant landscape of many areas of Southern Mediterranean as Andalusia (Spain). Different farming models coexist in the olive sector, but they had not been studied in the context of N cycle. By integrating field and model data, we analyzed N flows, N balance, levels of N cycling closure, and N footprints in olive groves employing various cultivation models. Farms were categorized on: Org (organic external fertilization, high level of biomass recycling, temporary spontaneous cover crops), Tra (organic external fertilization, low recycling, bare soil), Int (inorganic external fertilization, low recycling, bare soil) and IPr (inorganic or organic external fertilization, low recycling, temporary spontaneous cover crops). Tree N demand, averaging 55 kg ha-1 y-1, correlated with fruit production and canopy area, making them suitable proxies for calculating N demand without exhaustive sampling. The N balance was positive for all farming models, with the Org model showing a more neutral balance (+7.4 kg N ha-1 y-1) and the IPr olive farms showing surpluses (+40.2 kg ha-1 y-1). In Org farms, annual N inputs were the lowest and rely on natural entries like N fixation, while Cycling Index was significantly higher than those of other groups (between 1.45 and 1.81 times). This was attributed to N recirculation mechanisms such as cover crops, shredding tree pruning, and returning harvested N through composted olive mill pomace. Soil erosion, often overlooked, emerged as a major N outflow, especially in Org farms with the highest soil N content, resulting in the highest N losses per liter of oil. Per liter of olive oil, Trad, Ipr, and Int farms use between 1.9 and 2.2 times more anthropogenic N inputs than Org farms. Overall, our results highlight significant potential to enhance internal N cycling, increase self-sufficiency, and extend the lifespan of N in olive farming by implementing scalable management practices that promote nature-based processes. • Harvested fruit and tree canopy area were significant proxies for calculating the N demanded by olive trees. • Soil N balance of the groups of farms was positive and ranged from +7.4 to +40.2 kg ha-1 y-1, averaging +27.4 kg ha-1 y-1. • Highest N outputs other than harvested N were due to soil erosion. • Organic farms use half antropogenic N input per liter of olive oil compared to other olive farms. • Managements that enhance nature-based processes had the highest internal N cycling and throughoutflow. [ABSTRACT FROM AUTHOR]

Currently, there are some initiatives aimed at transforming agriculture from being a source to a sink of greenhouse gases, mainly by encouraging combination of management practices that drive nature-based climate processes (NbCS) resulting in an increase in the stocks of soil and biomass organic carbon. Olive grove cultivation represents a key socio-economic and environmental asset for Mediterranean rural regions. Being a woody crop planted in an orchard fashion, the potential for organic carbon accumulation in the biomass and the soil is very high. In this study, farm, trees and soil carbon balances were analysed in 12 pairs of olive groves located in Southern Spain with different tree densities, age, varieties and irrigation regimens. One from each pair of the olive groves has applied (> 8 years) a combination of management practices that promote NbCS resulting in an increase in the entry of carbon, whereas the other comparable nearby olive grove has not implemented management practices that promote NbCS or C entries (non-NbCS). C balance at the farm level was mainly neutral or positive and averaged + 1.20 Mg C ha−1 y−1. However, C balance in the NbCS olive groves was 5 times higher than that of the non-NbCS. The mean soil C balances were negative (−0.18 Mg C ha−1 y−1; losing soil organic C) in the non-NbCS and positive (+1.48 Mg C ha−1y−1) in the NbCS olive groves thanks to the increase in the carbon entries due to the management practices which boost NbCS. This study highlights the important contribution of olive farming in mitigating climate change, which in turn would be an economic incentive for olive growers. Nonetheless, there is a high potential for improvement by implementing management practices which enhance nature-based processes such as the cultivation of temporary spontaneous cover crops and the application of shredded tree pruning and composted olive mill pomace and/or manure to the soil. • C balance at farm level was positive in 21 out of 24 olive farms. • In some farms, the losses of SOC were compensated by the C gains in the trees. • C balance in NbCS olive groves was 5 times higher than these of the non-NbCS. • There was a clear positive relationship between soil C balance and the managed C inputs. [ABSTRACT FROM AUTHOR]

Late Quaternary alluvial sedimentary units in the Guadiana Menor River valley, a tributary of the Guadalquivir River in southern Spain are described based on geomorphological mapping, sedimentological analysis, palaeosol development, and radiocarbon chronology. Four infill units in the valleys were differentiated with surfaces at + 45 (MU1), + 70 (MU2), + 8–6 (MU3), and + 10 m (MU4) above the riverbed. Each unit is capped by a palaeosol. Unit MU1 (Late Pleistocene: > 43.5–34 cal kyr BP) consists of gravel and sand in channels and bars in braided river systems distally evolving to silty clays in the floodplain with vertic and clayic calcisols. It is capped by dark clays with gleysol development representing wetland environments in endorheic basins. Channelized gravels alternating with sandy silts make up unit MU2 (34–24 cal kyr BP), capped by a gypsisol and interpreted as a semi-arid alluvial fan distally evolving to playa-lake depositional systems. Unit MU3 (5600–2700 cal yr BP), extending along the valley bottom, is represented by gravels and sand distally evolving to a red and white laminated rhythmite of silt and clay deposited in the playa. Unit MU4 (600–700 cal yr BP) is scattered and represented by centimetre-thick gravels and sand sheet layers deposited by sheet flows in semi-arid constrained alluvial fans. Alternating intervals of alluvial aggradation (> 43.5–24 kyr BP, 5700–2700 cal yr BP, Late Middle Ages) and fluvial incision (24–6 cal kyr BP, 2700 cal yr BP to 1200 AD, 1500 AD to present) are interpreted as valley responses to climate variations and changes in land use. Two regional geomorphological changes are recorded in the sediments: (1) climate-induced aridification after 34 cal kyr BP with an arid climax after 24 cal kyr BP before the incision linked to the last glacial period, and (2) two human-forced aggradation stages (5600–2700 cal yr BP and 1200–1400 AD) interrupting the Late Pleistocene to Early Holocene incisional trend. [ABSTRACT FROM AUTHOR]

Abstract: During field soil surveys various soil morphological properties such as texture, structure, consistence, cutans and color are evaluated. However, these soil properties are described using nominal or ordinal variables. This makes it difficult to assess these variables objectively using numerical methods such as clustering or chronofunctions. Recently, principal component analysis (PCA) with non-linear optimal scaling transformation of the nominal and ordinal variables has been employed. We used this approach on the morphological properties of a Quaternary soil chronosequence from the fluvial terraces of the River Guadalquivir (Southern Spain) between the towns of Andújar and Villanueva de la Reina. The study comprised five pedons and 35 horizons (including the parent material from the current course of the river) in the following order: Haplic Palexeralf (1st terrace), Calcic Haploxeralf (2nd terrace), Haplic Palexeralf (3rd terrace), Typic Calcixerept (4th Terrace) and Typic Xerofluvent (Floodplain). A total of 17 field morphological variables were evaluated and transformed. The nominal variables were: structure type, texture, cutan morphology, hue dry and hue moist. The ordinal variables were: structure size, structure grade, consistence when moist, consistence when dry, stickiness, plasticity, cutan thickness, cutan frequency, value dry, value moist, chroma dry and chroma moist. The scaling obtained for variables showed a systematic trend with the soil age sequence, growing numerically with the expression of the property. The most important principal component of the non-linear PCA, PC1 (56% of the variance) was closely associated with the soil processes of illuviation of clay and rubefaction, which dominate the preholocenic soils of the chronosequence, and, consequently, was positively correlated with increase in hue, chroma, consistency when moist, structure grade and presence of cutans. The optimal scalings obtained from the morphological properties permitted the application of statistical methods such as cluster analysis, which grouped the five pedons and the parent material (PM) of the chronosequence in strict chronological order. Finally, we obtained chronofunctions of the transformed morphological variables which fitted the logarithmic models satisfactorily. [Copyright &y& Elsevier]

• Soil morphological properties differentiate productivity levels of bananas. • The categorical regression analysis can deliver an operational model in banana. • There are few backgrounds of soil quality indices with soil categorical properties. Soil morphological properties described in the field, such as texture, consistence or structure, provide a valuable tool for the evaluation of soil productivity potential. In this study, we developed a regression model between the soil morphological variables of banana plantations and a crop Productivity Index (PI) previously developed for the same areas in Venezuela. For this, we implemented categorical regression, an optimal scaling procedure in which the morphological variables are transformed into a numerical scale, and can thus be entered in a multiple regression analysis. The model was developed from data from six plantations growing "Gran Nain" bananas, each with two productivity levels (high and low), in two 4-ha experimental plots, one for each productivity level. Sixty-three A horizons in thirty-six soils were described using 15 field morphological variables on a nominal scale for structure type, texture and hue, and an ordinal scale for the rest (structure grade, structure size, wet and dry consistence, stickiness, plasticity, moist value, chroma, root abundance, root size, biological activity and reaction to HCl). The optimum model selected included biological activity, texture, dry consistence, reaction to HCl and structure type variables. These variables explained the PI with an R2 of 0.599, an expected prediction error (EPE) of 0.645 and a standard error (SE) of 0.135 using bootstrapping, and EPE of 0.662 with a SE of 0.236 using 10-fold cross validation. Our study showed how soil quality is clearly related to productivity on commercial banana plantations, and developed a way to correlate soil quality indicators to yield by using indicators based on easily measured soil morphological parameters. The methodology used in this study might be further expanded to other banana-producing areas to help identify the soils most suitable for its cultivation, thereby enhancing its environmental sustainability and profitability. [ABSTRACT FROM AUTHOR]

The fine sand fraction (50–250 μm) of Mediterranean soils from southern Spain provides valuable information on soil genesis and the origin of their parent materials. This study considers the whole fine sand and heavy fine sand (ρ > 2.82 g cm−3) of Luvisols, Calcisols and Fluvisols, which form a chronosequence (ages from 600 to 0.3 ka) of the River Guadalquivir terrace system. Advanced techniques (X‐ray diffraction, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, variable pressure scanning electron microscope with an energy dispersive X‐ray spectroscopy system and Raman analysis) were employed. Inheritance is the principal pedogenic process. The whole fine sand consisted of carbonates (calcite and dolomite), tectosilicates (quartz, K‐feldspar and plagioclases), phyllosilicates (illite/moscovite, biotite, Na‐mica, chlorite, kaolinite, interstratified vermiculite‐chlorite, vermiculite‐illite and smectite‐illite) and iron oxides (goethite and haematite). The minor minerals (rutile, anatase, ilmenite, zircon, staurolite, monazite, barite, apatite, andalusite, garnet and titanite) are concentrated, also through inheritance, in the heavy fine sand. However, there is also substantiated evidence for neoformation of rutile in these soils, never reported previously. In addition, we report that (a) the geochemical indices calculated in fine sand (SiO2/CaO, Chemical Index of Weathering (CIW), Weathering Index of Parker (WIP), Weathering Index (WI), Base Depletion Index (BDI), Weathering Ratio (WR) and Sr/Zr) are closely related to soil age, allowing chronofunctions to be established, and (b) geochemical indices provide information on the origin of soils and permit the establishment of a "critical point" corresponding to "time zero;" that is, the start of pedogenic alteration of the parent material. Highlights: Mineralogy and geochemistry inform on the provenance of the fine sandRutile is neoformed in the fine sand and co‐exists with the polymorph anataseThe properties of the fine sand including geochemical indexes fit chronofunctionsGeochemical indices determine a "critical point" related to the start of weathering [ABSTRACT FROM AUTHOR]

• Better growth: F. pulverulenta > A. prostrata > P. coronopus. • Increase in Na+ and Cl−, and decrease of K+ in plants with saline excretion. • Greater increase of metabolite concentrations in the most tolerant plants. • A common signaling response (phenols and polyamines) in three halophytes. Soil analyses of three saltmarshes in Jaén province (southern Spain) indicated Sodic Solonchack type for Don Benito saltmarsh, and Sodic Calcixerepts for Barranco Hondo and Brujuelo saltmarshes. Three halophytes (Frankenia pulverulenta , Atriplex prostrata , and Plantago coronopus) from these saltmarshes were submitted to long (21 days) and gradual (0, 100, 200, and 300 mM NaCl) salinity stress, under hydroponic culture. The results of fresh mass, dry mass, root:shoot ratio, leaf water content, ion content, proline, total phenols, and polyamines (putrescine, spermidine, spermine and cadaverine) were examined to investigate the species' responses to saline stress. Maximum biomass production and leaf water content was found between 100 and 200 mM NaCl in F. pulverulenta and at 100 mM NaCl in A. prostrata , while a decrease of these parameters was registered in P. coronopus as the salt concentration and salt-exposure time increased. In leaves, Na+ and Cl− accumulation increased with salt concomitant with a reduction of K+ in plants with salt excretion mechanisms (F. pulverulenta and A. prostrata), while high levels of ions were found with and without salt in P. coronopus. For osmotic adjustment, proline content proved important in F. pulverulenta and A. prostrata , while in P. coronopus this osmolyte decreased with salt, while phenols and polyamines increased in all three species. The highest levels in (Spermidine + Spermine): Putrescine ratio was related to the more salt-tolerant species. These results appear to indicate various adaptation responses to salinity. Rising levels of proline, phenols, and polyamines were related to better growth, which could contribute to different degree of tolerance and distribution of these species in saltmarshes. [ABSTRACT FROM AUTHOR]

Gully erosion is one of the main processes of soil degradation, representing 50%–90% of total erosion at basin scales. Thus, its precise characterization has received growing attention in recent years. Geomatics techniques, mainly photogrammetry and LiDAR, can support the quantitative analysis of gully development. This paper deals with the application of these techniques using aerial photographs and airborne LiDAR data available from public database servers to identify and quantify gully erosion through a long period (1980–2016) in an area of 7.5 km2 in olive groves. Several historical flights (1980, 1996, 2001, 2005, 2009, 2011, 2013 and 2016) were aligned in a common coordinate reference system with the LiDAR point cloud, and then, digital surface models (DSMs) and orthophotographs were obtained. Next, the analysis of the DSM of differences (DoDs) allowed the identification of gullies, the calculation of the affected areas as well as the estimation of height differences and volumes between models. These analyses result in an average depletion of 0.50 m and volume loss of 85000 m3 in the gully area, with some periods (2009–2011 and 2011–2013) showing rates of 10,000–20,000 m3/year (20–40 t/ha*year). The manual edition of DSMs in order to obtain digital elevation models (DTMs) in a detailed sector has facilitated an analysis of the influence of this operation on the erosion calculations, finding that it is not significant except in gully areas with a very steep shape. [ABSTRACT FROM AUTHOR]