SSS2.1

Soil threats in the Mediterranean region: Status, drivers and strategies for sustainable land use

SSS2.1

Soil threats in the Mediterranean region: Status, drivers and strategies for sustainable land use

Soil is one of the most significant components of the biosphere, and is essential to achieve the Sustainable Development Goals for 2030; to secure global environments, societies, and economies, for current and future generations. Over previous decades, the importance of the soil and its conservation has been increasingly recognised. However, growing population and associated demands for food, raw materials and physical space, have led to increasing soil threats and degradation. Although identified worldwide, these problems are particularly relevant in the Mediterranean region, where overall erosion rates are faster and soil organic matter is lower than in most of Europe. Additional soil threats, including soil compaction, sealing, contamination, decline in biodiversity and salinization, are also of relevant concern. Mediterranean areas also experience rural depopulation and abandonment, resulting in soil degradation favoured by problems such as wildfires and landslides. On the other hand, urbanization, particularly in the coastal zones, further increases pressure on soils. Furthermore, Mediterranean soils are more vulnerable to the adverse impacts of global warming, and are significantly susceptible to desertification. These threats are undermining the long-term capacity of soils to produce ecosystem services, and thus, enhancing soil resilience is a critical aspect to protect this non-renewable resource.
This session aims to discuss the state-of-the art of soil threats in the Mediterranean region, and the strategies used to mitigate soil degradation and enhance soil resilience in agriculture, forest, rangelands and urban areas. Specific aims include:
•Exchange knowledge on monitoring and data acquisition approaches, including laboratory and field-based measurements, remote sensing and modelling, to characterize the current status of soil degradation;
•Assess the main drivers of soil degradation and their environmental, social and economic impacts;
•Explore current and innovative technological and nature-based solutions to mitigate soil threats, restore degraded land and enhance soil resilience against global changes (e.g. land-use and climate);
•Discuss appropriate soil management practices to improve water and food security;
•Debate the role of Mediterranean soils on climate change adaptation and mitigation;
•Discuss governance and policy aspects relevant to soil protection and restoration in the Mediterranean.

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Convener: Carla FerreiraECSECS | Co-conveners: Zahra Kalantari, Daniel EvansECSECS, Paulo Pereira

vPICO presentations

| Mon, 26 Apr, 15:30–17:00 (CEST)

vPICO presentations: Mon, 26 Apr

Chairperson: Carla Ferreira

15:30–15:35

5-minute convener introduction

15:35–15:37

EGU21-10093

ECS

Status, processes, and drivers of soil degradation in the Mediterranean region

Carla S. S. Ferreira, Samaneh Seifollahi-Aghmiuni, Georgia Destouni, Marijana Solomun, Navid Ghajarnia, António Ferreira, and Zahra Kalantari

Soil supports life on Earth and provides several goods and services of essence for human wellbeing. Over the last century, however, intensified human activities and unsustainable management practices, along with ongoing climate change, have been degrading soils’ natural capital, pushing it towards possible critical limits for its ability to provide essential ecosystem services. Soil degradation is characterized by negative changes in soil health status that may lead to partial or total loss of productivity and overall capacity to support human societies, e.g., against increasing climate risks. Such degradation leads to environmental, social and economic losses, which may in turn trigger land abandonment and desertification. In particular, the Mediterranean region has been identified as one of the most vulnerable and severely affected European regions by soil degradation, where the actual extent and context of the problem is not yet well understood. This study provides an overview of current knowledge about the status of soil degradation and its main drivers and processes in the European Mediterranean region, based on comprehensive literature review. In the Mediterranean region, 34% of the land area is subject to ‘very high sensitivity’ or ‘high sensitivity’ to desertification, and risk of desertification applies to over more than 65% of the territory of some countries, such as Spain and Cyprus (IPCC, 2019). The major degradation processes are: (i) soil erosion, due to very high erosion rates (>2 t/ha); (ii) loss of soil organic matter, due to high mineralization rates while the region is already characterized by low or very low soil organic matter (<2%); and (iii) soil and water salinisation, due to groundwater abstraction and sea water intrusion. However, additional physical, chemical and biological degradation processes, such as soil sealing and compaction, contamination, and loss of biodiversity, are also of great concern. Some of the degradation processes, such as soil erosion, have been extensively investigated and their spatial extent is relatively well described. Other processes, however, such as soil biodiversity, are poorly investigated and have limited data availability. In general, a lack of systematic inventories of soil degradation status limits the overall knowledge base and impairs understanding of the spatial and temporal dimensions of the problem. In terms of drivers, Mediterranean soil degradation has mainly been driven by increasing population, particularly in coastal areas, and its concentration in urban areas (and consequent abandonment of rural areas), as well as by land-use changes and intensification of socio-economic activities (e.g. agriculture and tourism). Additionally, climate change, with increasing extent and severity of extreme events (droughts, floods, wildfires), may also be a key degradation driver in this region. Improved information on soil degradation status (including spatio-temporal extent and severity) and enhanced knowledge of degradation drivers, processes and socio-economic, ecological, and biodiversity impacts are needed to better support regional soil management, policy, and decision making. Science and evidence based improvements of soil resource governance and management can enhance soil resilience to regional and global changes, and support the region to achieve related Sustainable Development Goals and the Land Degradation Neutrality targets.

How to cite: Ferreira, C. S. S., Seifollahi-Aghmiuni, S., Destouni, G., Solomun, M., Ghajarnia, N., Ferreira, A., and Kalantari, Z.: Status, processes, and drivers of soil degradation in the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10093, https://doi.org/10.5194/egusphere-egu21-10093, 2021.

Soil erosion in the Mediterranean region

15:37–15:39

EGU21-10255

Highlight

Global soil erosion: Storm on the horizon

Pasquale Borrelli, David A. Robinson, Panos Panagos, Emanuele Lugato, Jae E. Yang, Christine Alewell, David Wuepper, Luca Montanarella, and Cristiano Ballabio

We use the latest projections of climate and land use change (year 2070) to assess potential global soil erosion rates by water erosion (interrill and rill processes) (Borrelli et al., 2020) using the RUSLE-based semiempirical modeling platform (GloSEM) (Borrelli et al., 2017). With some degree of uncertainty, GloSEM allows prediction of both state and change of soil erosion, identifying hotspots thanks to its high resolution (250 × 250 m) and predicting future variation based on projections of change in land use, soil conservation practices, and climate change.

Three alternative scenarios (2.6, 4.5, and 8.5) are tested using the Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) (LUH2 data) and 14 General Climate Models (GCMs) (WorldClim data), for a total of 42 modelling scenarios.

In the 2015 scenario, we estimate global soil erosion equal to 43 (+9.2/−7) Pg yr⁻¹; with a study area covering ∼95.5% of the Earth’s land surface (in Borrelli et al. 2017 the study area was ~84.1% of the Earth’s land surface). The future scenarios suggest that socioeconomic developments impacting land use will either decrease (SSP1-RCP2.6–10%) or increase (SSP2-RCP4.5 +2%, SSP5-RCP8.5 +10%) water erosion by 2070. By contrast, climate projections, for all global dynamics scenarios, indicate a trend, moving toward a more vigorous hydrological cycle, which could increase global water erosion (+30 to +66%). Quantitatively, 56.1 (+20.6+ /- 16.4) Pg yr⁻¹, 64.8 (+28.5/-21.4) Pg yr⁻¹, and 71.6 (+32.5/-24.7) Pg yr⁻¹ are predicted for the SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5 scenarios, respectively.

The modeling framework presented in this study adopts standardized data in an adequate format to communicate with adjacent disciplines and moves us toward robust, reproducible, and open data science.

References

Borrelli, P., Robinson, D.A., Fleischer, L.R., Lugato, E., Ballabio, C., Alewell, C., Meusburger, K., Modugno, S., Schütt, B., Ferro, V. and Bagarello, V., 2017. An assessment of the global impact of 21st century land use change on soil erosion. Nature communications, 8(1), pp.1-13.

Borrelli, P., Robinson, D.A., Panagos, P., Lugato, E., Yang, J.E., Alewell, C., Wuepper, D., Montanarella, L. and Ballabio, C., 2020. Land use and climate change impacts on global soil erosion by water (2015-2070). Proceedings of the National Academy of Sciences, 117(36), pp.21994-22001.

How to cite: Borrelli, P., Robinson, D. A., Panagos, P., Lugato, E., Yang, J. E., Alewell, C., Wuepper, D., Montanarella, L., and Ballabio, C.: Global soil erosion: Storm on the horizon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10255, https://doi.org/10.5194/egusphere-egu21-10255, 2021.

15:39–15:41

EGU21-1504

Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain).

Juan F. Martinez-Murillo, José A. Sillero-Medina, and José D. Ruiz-Sinoga

During the last 25 years, an increasing rainfall erosivity occurred in South of Spain according to recent studies. This fact may rendered in an increment of the derived threatens from water erosion and, consequently, soil loss processes, one of the main geomorphic agent in that geographical area. This study deals with the application of RUSLE equation in two-contrasted Mediterranean mountainous watershed from 1997 to 2018. Both of them are characterised with very common ecogeomorphologic features from Mediterranean mountains but differs in the rainfall regime: one watershed shows an altitudinal gradient from dry-Mediterranean to subhumid Mediterranean climate, and the other one from semiarid to dry-Mediterranean climate.

From the methodological point of view, RULSE was applied but some modifications were introduced in its calculation: i) rainfall intensity calculated in 10-minutes instead of 30-minutes for Factor R; ii) vegetation cover estimated by means of NDVI for Factor C; and iii) validation using field inventory of soil surface components.

The results indicated differences between both watersheds given their different ecogeomorphologic conditions. The precision of using I10 let valuate better the soil loss estimation and its spatial and temporal variability. The validation with the soil surface components obtained better results in the rainiest watershed with more biotic ecogeomorphological conditions. This study is of great useful to detect priority areas to carry out revegetation plans to control erosion and floodings.

How to cite: Martinez-Murillo, J. F., Sillero-Medina, J. A., and Ruiz-Sinoga, J. D.: Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1504, https://doi.org/10.5194/egusphere-egu21-1504, 2021.

15:41–15:43

EGU21-8879

Projections of rainfall erosivity over Italy exploiting EURO-CORDEX ensemble

Monia Santini, Roberta Padulano, Guido Rianna, Marco Mancini, and Mirko Stojiljkovic

Erosion processes are caused by a combination of predisposing factors (slope, intrinsic soil properties), accelerating factors (removal of vegetation cover, altered soil properties due e.g. to fires, overgrazing, tillage) and triggering factors (water – from rain and rivers – and wind). While the first components are rather unchanging (or changing slowly) at the human time scale, the last two must deal with the consequences of global changes. Indeed, modifications in land use, land management and climate have strong feedbacks so that, from one side, lands are more and more overexploited, degraded and exposed to erosion and, on the other side, over these lands, the frequency, magnitude, duration and timing of triggering events could deviate from their “normal” conditions.

According to the well-known RUSLE soil loss estimation model, the triggering effect of rainfall for sheet and rill erosion is accounted for by means of the so-called rainfall erosivity or “R-factor”. R-factor consists of the annual summation of the erosive power of relevant storm events, averaged over a significant period of observation. For each storm event, computation of R-factors requires high-resolution rainfall information for the evaluation of the maximum rainfall intensity occurring over a time window of 30 min during the rainfall event. Due to the generally limited access to sub-hourly precipitation observations, a number of empirical models relating R-factor to easily accessible climate, physical and geographical covariates, such as rainfall data at coarse aggregation levels, have been developed for different areas of the world.

As concerns Italy, a novel empirical model is proposed relating rainfall erosivity to cumulative precipitation, elevation and latitude. Such model, calibrated for a significant selection of relevant rain gauges with available sub-hourly data, showed a good accordance with observations and a large amount of explained variance at the annual scale, with promising results also at the monthly level. The model was effectively extended to cover the whole Italian Country for the period 1981-2010 by means of gridded rainfall datasets retrievable in the Copernicus Climate Change Service (C3S) Climate Data Store (CDS), with limited performance loss, exploring the feasibility of Copernicus products for erosion-related assessments. Although affected by limitations, the proposed model is particularly suitable for applications involving future rainfall projections since it explicitly accounts for monthly cumulative precipitation as the only climate covariate, differently for other proposed methodologies also including rainfall-related variables with higher temporal resolution, whose future trends cannot be robustly evaluated with current climate modelling tools. In the present research an ensemble of twelve future rainfall projections included in the Euro-Cordex initiative, bias-adjusted by means of the ERA5-Land reanalysis dataset, is considered to account for the uncertainties coming from the use of multiple projections. The proposed approach provides a unique example of rainfall erosivity dataset accounting for a wide ensemble of bias-adjusted rainfall projections resulting from different General Circulation Models/Regional Climate Models coupling, for multiple Representative Concentration Pathway scenarios (RCP 2.6, RCP 4.5 and RCP 8.5) and different future horizons (near, 2021-2050, and far, 2051-2080, future).

How to cite: Santini, M., Padulano, R., Rianna, G., Mancini, M., and Stojiljkovic, M.: Projections of rainfall erosivity over Italy exploiting EURO-CORDEX ensemble, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8879, https://doi.org/10.5194/egusphere-egu21-8879, 2021.

15:43–15:45

EGU21-1671

ECS

Soil characteristics and erosion in the UNESCO Geopark Estrela, Portugal.

Gerald Raab, Wasja Dollenmeier, Dmitry Tikhomirov, Markus Egli, Gonçalo Vieira, Piotr Migoń, Fabio Scarciglia, Christopher Lüthgens, and Marcus Christl

In Europe, a high soil erosion risk is modelled for the Mediterranean area such as the Iberian Peninsula (e.g., EEA, 2009), while actual field data often lacks behind. Here we present the first ^239+240Pu soil erosion results (last ~60 years) in the UNESCO Geopark Estrela, Portugal. We investigated soils in a former vastly glaciated and a non-glaciated area. We hypothesized that erosion rates in relatively young areas (max. about 16–20 kyr) will be distinctly higher than in old areas (several 100 kyr). We assumed that soil structure, organic matter and weathering degree in younger (natural) soils are still less favourable and do not yet protect efficiently enough soils from erosion. Besides soil erosion, we explored the weathering degree of the soil material using chemical weathering indices, determined the soil surface age using meteoric ¹⁰Be and looked at a broad set of physico-chemical soil characteristics of these two landscape settings.

A glimpse of our first Plutonium results indicates that the differences between these two settings are rather minor. Soil erosion rates in these natural conditions (Geopark) predominantly depend on slope. With increasing slope angle, a maximum soil erosion rate of ~1600 [t km^-2 yr^-1] is reached. Not surprisingly, the age estimates of the soils within the formerly glaciated area confirmed the start of formation after the beginning of ice-decay. The formerly glaciated area is depleted in C and N compared to the never glaciated area. In the never glaciated area, a higher soil weathering degree is found by multiple weathering indices and an overall lower SiO₂ content. Although past glacial activities rejuvenated the soil material (expressed by a lower weathering degree) and affected the soil organic matter content, soil erosion susceptibility does not seem to be higher compared to never glaciated areas. Under natural conditions, a quasi-steady state with respect to soil erosion seems to be reached fairly before 20 kyrs.

How to cite: Raab, G., Dollenmeier, W., Tikhomirov, D., Egli, M., Vieira, G., Migoń, P., Scarciglia, F., Lüthgens, C., and Christl, M.: Soil characteristics and erosion in the UNESCO Geopark Estrela, Portugal., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1671, https://doi.org/10.5194/egusphere-egu21-1671, 2021.

15:45–15:47

EGU21-1787

ECS

Comparison of water-stable aggregates on different soil types and land-uses in a Portuguese Mediterranean catchment

Radek Klíč, Carla Sofia Santos Ferreira, António Ferreira, and Miroslav Kravka

Erosion is one of the main soil threats in the Mediterranean region, leading to degradation and desertification of several areas. Water stable aggregates (WSA) is a rate of the extent to which soil aggregates resist falling apart when wetted and hit by rain drops, indicating also the resistence of soil to compaction and soil quality status. This study aims to determine the WSA in differrent soils, characterized by distinct land-uses and soil types. This work is part of Ribeira dos Covões catchment research, in the suburbs of Coimbra, the largest city of central Portugal, where research dealing with soil and hydrological properties has been developed for long time. WSA were investigated for agricultural and forest soils, on both sandstone and limestone. Soil surface samples (0-10cm) were collected in December 2020, and analysed through wet sieving method which quantifies the amount of water-stable soil aggregates fractions.

Not surprisingly, the results showed that forest soils contain a much higher proportion of water-stable soil aggregates of larger fractions than agricultural soil, where the smaller fractions prevailed. Similar results have been also reported in previous studies and found during our previous research at Praha-Suchdol locality (Housle), in Czech Republic. The fraction distribution of WSA in sandstone and limestone was comparable for forest soils. In case of agricultural soils, distribution of WSA was slightly different. WSA are a relevant part of soil surface layer, with important impacts on other soil properties (e.g. soil moisture, hydrophobicity, infiltration), thus affecting the rainfall-runoff-erosion processes, previously investigated in the study area. Further research will be developed to better assess WSA differences between distinct forest types, given the relevance of vegetation species for example on hydrophobicity and WSA dynamics. A better understanding of WSA in different soil types will be useful to support improved soil management and mitigate land degradation.

How to cite: Klíč, R., Sofia Santos Ferreira, C., Ferreira, A., and Kravka, M.: Comparison of water-stable aggregates on different soil types and land-uses in a Portuguese Mediterranean catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1787, https://doi.org/10.5194/egusphere-egu21-1787, 2021.

15:47–15:49

EGU21-16224

Multi-fractional sediment fingerprinting in monitoring sediment sources in a peri-urban Portuguese catchment

Rory Walsh, Carla Ferreira, William Blake, Sam Higton, and Antonio Ferreira

This paper explores the potential for using multiple particle size fractions in a hierarchical geochemical sediment fingerprinting approach to the assessment of changes in sediment sources through time within a small Mediterranean peri-urban catchment. Conventional sediment fingerprinting has focussed on the <63µm fraction of fine bed-sediment on the basis that this fraction represents suspended sediment, which in turn is considered dominant over bedload in catchment sediment budgets. In reality, however, coarser sediment than 63µm may form part of suspended sediment and/or occurs as relatively fast-moving fine bedload. Furthermore, sediment sources vary in their particle size distribution and, as geochemical composition can vary with particle size, it is arguable that sediment fingerprinting studies should consider use of multiple size fractions.

This study explores this approach using <63µm, 63-125µm, 125-250 µm and 250-2000µm size fractions. It focuses on the north-south flowing Ribeira dos Covões catchment (6.2 km²), on the outskirts of Coimbra in central Portugal. The climate is humid Mediterranean. Catchment geology is 56% sandstone (in the east), 41 % marly limestone (in the west) and 3 % alluvium. Current land-use is 56% woodland, 4 % agricultural and 40% urban (mainly residential, but also including a recently constructed enterprise park (5%) and major highway (1%)). Recent urbanization has largely occupied former agricultural land.

The study adopts a multi-proxy sediment fingerprinting approach to assessment of changes in sediment sources, based on geochemical (elemental) characterization of the four different size fractions of fluvial bed-sediment and soil samples, using a Niton x-ray fluorescence (XRF) elemental analyser. Sampling of fluvial sediment was carried out at 33 sites within the stream network (including all significant tributaries, downstream sites and the catchment outlet). Samples were collected in July 2018 and November 2018 following contrasting ‘late-wet-season’ and ‘end-of-dry-season’ events. In July 2018, samples of potential sediment sources were collected including: (i) soil surface (0-2cm) samples at 64 locations, (ii) 17 samples from eroding channel margin sites, and (iii) 15 samples of road sediment. All fluvial and soil samples were sieved to obtain the four target size fractions. The elemental geochemistry of each sample fraction at all fluvial and source sites was derived using the XRF analyser. (These results were added to similar datasets previously obtained on three occasions in 2012-15 in a period of enhanced urban constructional disturbance). Differences (and similarities) in geochemical signatures between the different size fractions at each survey date at and between each tributary and potential source site were assessed using a range of statistical techniques. Messages arising are discussed. For each size fraction and survey date, Bayesian unmixing models were used in a hierarchical (confluence-based) fashion to assess the contributions of sub-catchments to downstream sites and the catchment outlet. Modelling results for the two 2018 events were validated by comparing them with suspended sediment records collected at five tributary locations and at the catchment outlet. Although overall, the modelling was successful in indicating and quantifying significant changes in sediment sources through time within the catchment, uncertainties in interpretation of the multiple fractions are identified and discussed.

How to cite: Walsh, R., Ferreira, C., Blake, W., Higton, S., and Ferreira, A.: Multi-fractional sediment fingerprinting in monitoring sediment sources in a peri-urban Portuguese catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16224, https://doi.org/10.5194/egusphere-egu21-16224, 2021.

Degradatio in agricultural areas / Conservation agriculture

15:49–15:51

EGU21-1309

Tillage-induced management impact on soil properties and initial soil erosion in degraded calcareous soils in Mediterranean fig orchard

Igor Bogunovic, Leon Josip Telak, Ivan Dugan, Carla S. S. Ferreira, and Paulo Pereira

High majority of soil erosion studies focus on cereal croplands, vineyards, olive, avocado, citrus, almond, persimmon, apple, and apricot orchards. To date, there is a lack of information about the possible impacts of tillage management on soil properties and hydrological response in fig orchards. Understanding this will be crucial to design efficient soil conservation practices and degradation control. Therefore, the aim of this research was to study the initial soil erosion in fig plantations and temporal evolution of initial soil erosion after the tillage intervention on undeveloped, Calcic Fluvisol in Dalmatia, Croatia. The study was conducted by collecting undisturbed soil samples, followed by rainfall simulations (58 mm h^-1, during 30 min, over 0.785 m² plots) in eight repetitions per measurement 2 days, 1 month, and 3 months after the intensive tillage. The results showed a clear difference among soil properties trough time. Seasonal effect significantly modifies soil properties and hydrological response. Soil bulk density and mean weight diameter increase (p < 0.05), while water holding capacity, water stable aggregates, soil organic content, and available phosphorus decrease (p < 0.05) by time after tillage_.The highest runoff was measured 1 month (100.5 m³ ha^-1), followed by 3 months (82 m³ ha^-1), and 0 months (48.3 m³ ha^-1) after tillage. Sediment losses were highest at 3 months (3488.9 kg ha^-1), followed by 3.5 times lesser losses at 1 month (990.6 kg ha^-1), and 8.2 times lower right after the tillage (426.1 kg ha^-1). Temporal variations of soil erodibility in this study were under the influence of soil natural consolidation and precipitation. Fig orchards on young, undeveloped soils are highly erodible forms of land use and conservation practices need to be deploy in order to mitigate land degradation.

Keywords: soil physical properties, runoff, permanent plantation, short-term changes, undeveloped soil

Acknowledgments

This work was supported by Croatian Science Foundation through the project "Soil erosion and degradation in Croatia" (UIP-2017-05-7834) (SEDCRO).

How to cite: Bogunovic, I., Telak, L. J., Dugan, I., Ferreira, C. S. S., and Pereira, P.: Tillage-induced management impact on soil properties and initial soil erosion in degraded calcareous soils in Mediterranean fig orchard, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1309, https://doi.org/10.5194/egusphere-egu21-1309, 2021.

15:51–15:53

EGU21-15889

SQI: Development index and application for two contrasting mediterranean landscapes

Jose Antonio Sillero-Medina, Paloma Hueso-Gonzalez, and Jose Damián Ruiz-Sinoga

Soil quality indexes (SQIs) are very useful in assessing the status and edaphic health of soils. This is particularly the case in the Mediterranean area, where successive torrential rainfall episodes give rise to erosion and soil degradation processes; these are being exacerbated by the current climate crisis. The objective of this study was to analyze the soil quality in two contrasting Mediterranean watersheds in the province of Malaga (Spain): the middle and upper watersheds of the Rio Grande (sub-humid conditions) and the Benamargosa River (semi-arid conditions). Field soil sampling was carried out at representative sites, and the soils were subsequently analyzed for various edaphic properties in the laboratory. From the resulting data, the mean values have been grouped and reclassified, and based on a multicriteria evaluation, a SQI for the study region was generated. The results show that there are major differences between the two watersheds, with optimal soil quality values being found in the Rio Grande watershed, but more unfavorable values occurring throughout most of the Benamargosa River watershed.

How to cite: Sillero-Medina, J. A., Hueso-Gonzalez, P., and Ruiz-Sinoga, J. D.: SQI: Development index and application for two contrasting mediterranean landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15889, https://doi.org/10.5194/egusphere-egu21-15889, 2021.

15:53–15:55

EGU21-7994

ECS

Highlight

Effect of conservation agriculture practices on the resilience of Mediterranean soils to the predicted seasonal drought events

Laura Morales, María T Domínguez, Mª Belén Herrador, Engracia Madejón, and Elena Fernández-Boy

How climate change will affect soil functioning is a major concern, especially in Mediterranean agrosystems, where, according to climate change projections, the occurrence of extreme temperatures and drought events will be increased. The main objective of our experiment was to evaluate the effect of land management (tillage system) on soil resilience against a simulated dry-rewetting cycle. Soil samples were collected from an in-situ field experiment established in 2008 in the Guadalquivir Valley, where conservation agriculture practices have been tested. Three different land management practices under a typical Mediterranean wheat-legume rotation system were compared: 1) traditional tillage (TT), 2) minimum tillage (MT) and 3) no-tillage (NT). Following our hypothesis, conservation agriculture practices (reduced tillage and no-tillage) may allow a more mature soil microbial community by reducing soil perturbation, and this would result in higher resistance of soil functioning against drought periods. Soil enzyme activities (β-glucosidase, phosphatase, acetylglucosaminidase, aminopeptidase, and dehydrogenase activities), microbial functional diversity (Microresp method), and soil DNA concentration (as an index of microbial biomass) were analyzed in a base-line sampling. Afterwards, a dry-rewetting cycle was simulated under controlled conditions. 8 subsamples of 50g from each soil sample were hydrated to reach 70% of each soil water holding capacity (WHC) and kept in those conditions for a pre-incubation period of 15 days. After this period, half of the replicates were let dry for 12 days (drought), while the others were maintained at 70% WFC (controls). Finally, all replicates were rehydrated again to the initial water content during a 14 days rewetting period. During this cycle, soil respiration rates were periodically measured to study the evolution of soil microbial activity. Our results showed that initial respiration rates were slightly higher in MT compared to NT (p<0.1), likely due to higher organic C and N content in the MT soils. Drought extremely reduced respiration rates in the three treatments, but the results did not show a clear pattern among treatments. During the rewetting period, respiration rates were significantly higher in drought samples in comparison with the controls, while no significant differences were found for the land management treatments. Besides, land management practices did not have a significant effect on soil DNA concentration, functional diversity of the microbial community, or enzyme activities. To conclude, the absence of a clear effect of land management practices on soil resilience to drought may be due to the experimental conditions. An in-situ experiment will allow us to determine if tillage reduction enhances soil resilience to moisture stress.

How to cite: Morales, L., Domínguez, M. T., Herrador, M. B., Madejón, E., and Fernández-Boy, E.: Effect of conservation agriculture practices on the resilience of Mediterranean soils to the predicted seasonal drought events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7994, https://doi.org/10.5194/egusphere-egu21-7994, 2021.

15:55–15:57

EGU21-2158

ECS

The role of inter-row grass cover in steep viticulture: understanding soil erosion combining in-field observation and remote sensing

Eugenio Straffelini, Stefan Otto, Anton Pijl, Enrico Marchesini, Simone Gottardi, Nicola Tormen, Andrea Pitacco, Luca Tezza, and Paolo Tarolli

Steep slope viticulture is a common practice in the Mediterranean basin offering landscapes of considerable environmental and socio-economic value. However, these agricultural systems are very fragile. One of the main problems is soil erosion due to extreme rainfall, both for drop splash and water accumulation. This may cause a progressive reduction in soil fertility and the occurrence of instabilities and land degradation phenomena. To worsen this condition there is the soil compaction by mechanization and the intensification of severe weather events due to climate change (Tarolli and Straffelini, 2020).

Sustainable farming techniques may provide innovative solutions to reduce the risk of soil erosion. A virtuous approach involves the use of herbaceous coverings between the rows of vines, for many reasons. They provide active protection from the kinetic energy of water droplets; reduce the amount of water flowing on the surface positively affecting the infiltration capacity of the soil; improve ecosystem services in the vineyard.

This work aims to evaluate the effectiveness of different types of grass cover in terms of erosion and runoff generation in steep slope viticulture. The research is part of the SOiLUTION SYSTEM project (www.soilutionsystem.com) within the EU Rural Development Programme (Programma di Sviluppo Rurale per il Veneto 2014-2020); it is proposed to identify an integrated system of environmentally and economically sustainable interventions to reduce the risk of erosion and improve soil management in the terraced area of Soave (Veneto region), one of the two Italian GHIAS-FAO site. In particular, we have set up an experimental vineyard, where different managements are being tested, one for each inter-row of equal size and slope. Downstream of each of them, a water/sediment trap has been developed, obtaining continuous measurements of water volume and sediment concentration over two years. In this way, it is possible to compare the measures understanding the propensity of managements to generate runoff and soil erosion.

Specifically, many types of managements have been evaluated. (1) Continuous tillage, or a bare soil row; (2) Reference, a row where the farm's traditional grass cover is proposed; (3) Nectariferous, or a mix of herbaceous species capable of attracting insects and thus increasing biodiversity in the row; (3) Single tillage, or a row tilled once a year; (4) Native, or a row sown with native species of the place where the vineyard is located.

In combination with in-field experiments, an analysis was carried out on remote sensing data. The evolution of high-tech in topography permits low-cost tools and methodology to create high-resolution Digital Terrain Models (DTMs). For this purpose, we used a RPAS (Remotely Piloted Aircraft Systems) paired with Structure from Motion technique (RPAS-SfM). 3D reconstruction provides detailed knowledge of the terrain features, offering interesting insight to understand the processes that took place in the vineyard. The integrated implementation of in-field measures with remote sensing data opens new opportunities in runoff and soil erosion understanding, providing stakeholders with useful guidelines for sustainable management.

Tarolli, P., & Straffelini, E. (2020). Agriculture in Hilly and Mountainous Landscapes: Threats, Monitoring and Sustainable Management. Geography and Sustainability, 1 (1) (2020), pp. 70-76. https://doi.org/10.1016/j.geosus.2020.03.003

How to cite: Straffelini, E., Otto, S., Pijl, A., Marchesini, E., Gottardi, S., Tormen, N., Pitacco, A., Tezza, L., and Tarolli, P.: The role of inter-row grass cover in steep viticulture: understanding soil erosion combining in-field observation and remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2158, https://doi.org/10.5194/egusphere-egu21-2158, 2021.

15:57–15:59

EGU21-606

Long-term evaluation of cover crops on soil and runoff losses under trafficked conditions in olive orchards

Jose Alfonso Gomez and Gema Guzman

Maintenance of ground cover vegetation in olive orchards has been shown to reduce soil and runoff losses as compared to bare soil. However, extrapolation of its impact at hillslope scale under different conditions still challenging for several reasons. One is the limited duration of available experiments, usually shorter than 3 years, which can´t capture the annual variability in precipitation typical of Mediterranean type of climate. A second reason is the small scale in which many experiments are carried out, which do not capture all the relevant erosion processes at hillslope scale. A third reason, hardly discussed, is the use of the runoff plots that limits traffic resulting in conditions that might not be fully representative of actual orchards.

For evaluating the effect of temporary cover crops on water erosion processes in olives at hillslope scale, runoff and soil losses have been monitored from 2008 to 2019 in La Conchuela. This is an olive farm located in Southern Spain, where average annual precipitation is 655 mm, on Typic Haploxerert (clay content > 50%). Six runoff plots (14x24 m) delimited by steel beams on concrete foundation were established in a 13.4 % slope, containing 3 rows of 4 trees. This allows normal farm operations. Since 2008-2009, two soil management systems, conventional tillage (CT) and temporary cover crops (CC), were tested. In the two CT plots ground vegetation was controlled by 2-3chisel ploughing passes during the year. CC in the other four plots consisted of sowing manually in mid Fall a grass or a mix with grasses every 1 to 3 years without disturbing the soil surface, been mowed in early Spring. The aim of this cover crop was to be grown up spontaneously from seed produced the previous year. Weeds along the tree rows are controlled by herbicides in both cases.

No significant differences were detected (p < 0.05) for the whole period, although CC showed lower runoff and soil losses values. Runoff data ranged from 157.7 ± 61.2 to 144.5 ± 46.4 mm, and soil losses varied from 24.3 ± 9.1 to 16.4 ± 7.0 t·ha^-1 at the CT and CC treatments respectively. The lack of statistical differences can be explained by the large variability recorded in the measurements at the six plots, especially at the CC due to the specific weather and traffic conditions. Our experiment shows how in a crop, olives, subject to intense traffic during the harvesting season (happening in late fall or early winter, rainy season) and in an orchard on heavy soils, maintenance of a good cover crop is challenging in many years. Our results call for caution when extrapolating the benefits of cover crops in olives from the experimental plots to real world conditions. It also highlights the need for improved soil management under these conditions (e.g. controlled traffic, combination with inert mulch, …) to improve soil and water conservation in intensively cultivated olive orchards in heavy soils.

How to cite: Gomez, J. A. and Guzman, G.: Long-term evaluation of cover crops on soil and runoff losses under trafficked conditions in olive orchards, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-606, https://doi.org/10.5194/egusphere-egu21-606, 2021.

15:59–16:01

EGU21-6199

Introduction of legume cover crops practice in intensive grain corn crop system to mitigate soil threats in the Mediterranean region

Anne Karine Boulet, Carlos Alarcão, Carla Ferreira, Adelcia Veiga, Lara Campos, António Ferreira, and Rudi Hessel

In Portugal, grain corn is the main cereal produced, comprising 56% of total cereal yield. It is grown in intensive monoculture cropping systems that may have negative effects on soil quality, affecting long-term fertility and productivity, and therefore the sustainability of production. A promising management practice to mitigate soil degradation is to grow a cover crop during the usual fallow period. This study examined in which extend six species of legume cover crops (forage pea (pisum sativum L), yellow lupin (lupinus luteus), crimson clover (trifolium incarnatum), balansa clover (trifolium michelianum), persian clover (trifolium suaveolens), and arrowleaf clover (trifolium vesiculosum) are suitable to mitigate soil threats in grain corn systems specifically in the Mediterranean region. Specific objectives were to identify the effectiveness of the legume 6 species in improving soil fertility (i.e., soil organic matter content), mitigating nutrient leaching, nutrient recycling, and weed control. The study was performed in the lower Mondego valley in central Portugal. It covered two autumn to spring periods of cover crop cultivation, and assessed changes in soil fertility, dry biomass yield of legumes and weeds, and their associated nutrient content (total nitrogen-phosphorus-potassium).

In general, the six legume cover crops (LCC) species showed good adaptation to Mediterranean conditions, yielding large amounts of biomass (up to 8 ton/ha for clovers species). At the short term, LCC incorporation into the soil had no clear effect in soil organic matter content. The median uptake of NPK macronutrients for all species was high respectively 176-20-172 kg/ha, due to their generally high biomass production, highlighting their great potential to mitigate nutrient leaching. The capacity of the LCC to provide green manure services enabled a median reduction of 40% of N, 60% of P, and 100% of K supplied by mineral fertilizers necessary to attain a corn grain yield of 12t/ha. LCC showed a good effectiveness in weeds control, although only in the second year of the study. Three clover species (crimson, balansa, arrowleaf) performed best in terms of weed control maintaining weed production below 0.5 ton/ha, vs 3-4 ton/ha in control plots, due to early establishment and/or high biomass production in later growth stages, and avoiding the first application of herbicide in pre-emergent herbicide for grain corn cultivation.

How to cite: Boulet, A. K., Alarcão, C., Ferreira, C., Veiga, A., Campos, L., Ferreira, A., and Hessel, R.: Introduction of legume cover crops practice in intensive grain corn crop system to mitigate soil threats in the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6199, https://doi.org/10.5194/egusphere-egu21-6199, 2021.

16:01–16:03

EGU21-91

ECS

Plant trait analysis to determine effective annual cover crops for Spanish orchards

Helena Ripley, Carly Stevens, and John Quinton

This paper investigates the use of plant trait analysis on cover crop species, and the impact selected species had on soil chemistry in a Spanish olive orchard. Farmers with hillside orchards in Spain frequently remove vegetation between tree rows due to concerns about water competition in the semi-arid environment. However, this increases the vulnerability of the soil to water erosion. Despite research showing that annual cover crops control soil loss, there has been little uptake of this form of management by farmers.

Ten species, native to southern Spain which had previously been used in cover crop experiments, and for which the seed was low cost, were assessed with plant trait analysis. Above and below ground traits, including specific leaf area, total biomass, root diameter and root volume, were examined to indicate the potential of the plants to reduce splash erosion, runoff and soil detachment. Four of the species were then selected and used in monocultures and mixes in an olive orchard set up in collaboration with CSIC in Cordoba. Soil moisture, rainfall, temperature and soil cover data was collected. Chemical analysis of plant and soil samples is to take place in January 2021.

Brachypodium distachyon, Calendula arvensis, Medicago sativa and Medicago truncatula had the most potential as cover crop species. In the field, the treatment with the greatest number of species (two grasses, one legume and one forb) had the highest mean soil cover at 78 ± 16%. It is hypothesised that the plots in which the greatest cover was established would show the greatest change in soil chemistry and that, where the legume was planted there will be higher nitrogen in the soil.

This presentation will outline the plant traits analysed, the outcomes of this analysis and the impact selected plants had on plant and soil chemistry in the field.

How to cite: Ripley, H., Stevens, C., and Quinton, J.: Plant trait analysis to determine effective annual cover crops for Spanish orchards, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-91, https://doi.org/10.5194/egusphere-egu21-91, 2021.

16:03–16:05

EGU21-7408

ECS

solicited

Highlight

Plastic mulch in agriculture: the case of low density polyethylene and its interactions with pesticides and soil microbiota

Nicolas Beriot, Raul Zornoza, Paul Zomer, Onurcan Ozbolat, Eva Lloret, Raúl Ortega, Isabel Miralles, Esperanza Huerta Lwanga, and Violette Geissen

Low Density Polyethylene is the most applied plastic mulch in agriculture, for decreasing water evaporation, increasing soil temperature, or preventing weeds. Incomplete removal of polyethylene mulch causes plastic pollution in agricultural soils. In conventional agriculture the use of plastic mulch is combined with the use of pesticides. Little is known about the long term effects on soils of plastic debris accumulations in relation with pesticides residues.

We studied 18 parcels in vegetable farms, under organic or conventional management, where plastic mulch has been used for 5 to 20 years in Cartagena’s country side (SE Spain). We sampled soil at two depths: 0-10 cm and 10-30 cm. We compared the macro and micro plastic debris contents, the pesticides residue levels and the soil physiochemical properties between parcels. The ribosomal 16S and ITS DNA regions were sequenced to study shifts in bacterial and fungal communities, respectively. Soils under conventional management contained on average more than 6 different pesticides residues and soils in both managements contained on average 0.2±0.26 g/kg plastic debris. This study also showed how plastic and pesticides interact in soils and affect the microbial community. We identified the most sensitive groups which can act as bioindicators for plastic and pesticide pollution in soils.

How to cite: Beriot, N., Zornoza, R., Zomer, P., Ozbolat, O., Lloret, E., Ortega, R., Miralles, I., Huerta Lwanga, E., and Geissen, V.: Plastic mulch in agriculture: the case of low density polyethylene and its interactions with pesticides and soil microbiota, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7408, https://doi.org/10.5194/egusphere-egu21-7408, 2021.

16:05–17:00

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