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Eshel G.,Soil Erosion Research Station | Lin C.,Beijing Normal University | Banin A.,Hebrew University of Jerusalem
Science of the Total Environment | Year: 2015

We investigated changes in element content and distribution in soil profiles in a study designed to monitor the geochemical changes accruing in soil due to long-term secondary effluent recharge, and its impact on the sustainability of the Soil Aquifer Treatment (SAT) system. Since the initial elemental contents of the soils at the studied site were not available, we reconstructed them using scandium (Sc) as a conservative tracer. By using this approach, we were able to produce a mass-balance for 18 elements and evaluate the geochemical changes resulting from 19. years of effluent recharge. This approach also provides a better understanding of the role of soils as an adsorption filter for the heavy metals contained in the effluent. The soil mass balance suggests 19. years of effluent recharge cause for a significant enrichment in Cu, Cr, Ni, Zn, Mg, K, Na, S and P contents in the upper 4. m of the soil profile. Combining the elements lode record during the 19. years suggest that Cr, Ni, and P inputs may not reach the groundwater (20. m deep), whereas the other elements may. Conversely, we found that 58, 60, and 30% of the initial content of Mn, Ca and Co respectively leached from the upper 2-m of the soil profile. These high percentages of Mn and Ca depletion from the basin soils may reduce the soil's ability to buffer decreases in redox potential pe and pH, respectively, which could initiate a reduction in the soil's holding capacity for heavy metals. © 2014 Elsevier B.V.


Stavi I.,Dead Sea and Arava Science Center | Argaman E.,Soil Erosion Research Station | Zaady E.,Israel Agricultural Research Organization
Catena | Year: 2016

Stubble grazing by livestock in post-harvest wheat fields is common in drylands. Previous studies have shown that this practice causes land degradation. Therefore, the objective of this study was to examine the effect of long-term stubble grazing, by comparing soil quality indicators in continuous wheat croplands of two rain-fed farming systems: with moderate stubble grazing during the summer (GR) vs. entire stubble retention (NO). Multi-annual averaged dry organic matter residue retained on the ground surface was ~0.8Mgha-1 in NO, as opposed to ~0.3Mgha-1 in GR. the same soil characteristics were also studied in 'natural' lands (NAT), to assess land-use change impact. The study was implemented in the semi-arid, northern Negev of Israel. Sampling of soil at depths of 0-5 and 5-10cm was conducted in summer 2013. Some of the results suggest the degradation of soil quality following land-use change from NAT to croplands, as well as in GR, compared to NO. This included the coarse root biomass, which was 67% to ~two times greater under NAT than that under NO and GR. This impact was also revealed by the aggregate slaking index which was 18% to two times greater under the two cropland treatments than that under NO, as well as for the clay dispersion index which was ~two to three times greater under the two cropland treatments than that under NO. At the same time, unexpectedly, the majority of soil characteristics showed better soil quality under GR than that under NO. For example, hygroscopic moisture content under NAT was only 10% greater than that under GR, but 22% greater than that under NO. Also, the soil organic carbon pool was similar between NAT and GR, which had 16-22% greater value than that under NO. Overall, soil aggregation properties also suggested negative impact of land-use change, but, at the same time, showed a positive impact on soil quality by GR compared to that under NO. These aggregation properties included the micro-aggregate content, stable aggregate content, contents of the aggregates >2000μm, the aggregate size fraction 1000-5000μm, mean weight diameter of aggregates, and mean weight diameter of the 1000-5000μm aggregate size fraction. An unexpected effect was recorded for the content of clods >8000μm, which was ~two times greater under NAT than that under the two cropland treatments. The soil organic carbon's stratification ratio was marginally affected by treatment (P =0.1015), and was 4% and 17% greater under NAT than that under NO and GR, respectively, revealing the clearest layering of soil organic carbon under NAT and the least clear layering under the GR. This suggests that mixing of organic residues in soil is smallest under NAT and greatest under GR. It is proposed that, in the long term, together with the input of animal excretion, the mixing of stubble residue in soil imposed by the livestock trampling compensates for the quantitative loss of stubble (through its consumption by the grazing animals), increasing soil organic carbon pool, and improving macro-aggregation processes and overall soil quality. A conceptual model is proposed to summarize these effects and relate them to soil conservation issues. © 2016 Elsevier B.V.


Eshel G.,Soil Erosion Research Station | Singer M.J.,Water Resources University
Geoderma | Year: 2016

In order to evaluate the possibility of tracing dissolved inorganic carbon (DIC) derived from calcite dissolution under open system conditions, controlled laboratory experiments using stable carbon isotopes were conducted in a specially designed reaction chamber with constant pH monitoring. The system design also allowed us to measure the forward and backward (degassing) gas transfer reactions rates. We confirmed that the degassing reaction rate can be two to four times slower than the gas transfer reaction rate depending on the differences in pCO2 between the gas phase and the liquid. The isotopic analyses suggest that the carbon isotopic signature of DIC under open system conditions is controlled by the CO2 carbon isotopic signature, the isotopic fractionation between CO2, the relative occurrence of the different DIC species, and changes in pH. We found that the isotopic signature of DIC is not affected by the isotopic signature of the calcite or the mechanism controlling the dissolution (protonation or hydration). Practically this study suggests that it is not possible to trace the DIC derived from calcite dissolution under open system conditions. It supports the approach of evaluating the pedogenic carbonate content by stable carbon isotopes methods. In open system conditions: a) pH can explain up to 8‰ variation in the DIC δ13C signature and b) temperature is the second most important factor affecting the δC13-DIC signature, and only at pH above neutrality. © 2016 Elsevier B.V.


Stavi I.,Dead Sea & Arava Science Center | Argaman E.,Soil Erosion Research Station
Catena | Year: 2016

Water availability is a major limiting factor for dryland afforestation. Earthworks that modify natural landforms for the formation of runoff harvesting systems are prevalent in the Israeli drylands, with the aim of establishing afforestation projects. However, serious concerns alarm that such earthworks have detrimental effects on the geo-ecosystem functioning. Therefore, the objective of this study was to examine the impact of the establishment of contour bench terrace (also called shichs/shychs/shikim) runoff harvesting systems on selected soil properties, with particular focus on soil aggregation. Thus, we assessed the effect of the establishment of contour bench terraces in a multi-aged forestry land, comprised of 2-year-old and 9-year-old afforestation areas, and compared them to ‘natural’ hillslopes as a reference treatment. The study was implemented in the Ambassadors' Forest, located in the semi-arid northern Negev of Israel, where we sampled the surface soil (at a depth of 0–5 cm) in north- and south-facing hillslopes. Considerable differences were recorded for the afforestation systems between the source (inter-terrace area) and sink (terrace-bottoms) areas. Data normalizing according to the relative cover percentage of the terraces and inter-terrace areas showed that the mean values of mean weight diameter (MWD), stable aggregate content, and particulate organic carbon in the natural hillslopes were 1.4%, 32.4%, and 20%, respectively, greater than in the 9-year-old afforestation systems, and 12.1%, 28.9%, and 31%, respectively, greater than in the 2-year-old systems. Means of clod content, aggregate slaking index, and clay dispersion index in the natural hillslopes were 62.3%, ~ twofold, and 35.0%, respectively, smaller than in the 9-year-old systems, and almost threefold, nearly twofold, and 46.2%, respectively, smaller than in the 2-year-old areas. The soil calcium carbonate content was similar in soils of the natural hillslopes and 9-year-old afforestation lands, which was ~ 17% smaller than in the 2-year-old afforestation systems. Considerable differences among the land-uses were also recorded for the soil texture. Mean coarse root biomass, despite revealing only a marginally-significant effect (p-value = 0.0765), was 40.0% greater in the natural hillslopes than in the 9-year-old systems, and more than twofold greater than in the 2-year-old systems. Hillslope aspect affected some of the measured properties, revealing only slightly better soil conditions in the (mesic) north- than in the (xeric) south-aspects. The data revealed that forestry-related earthworks degrade the soil quality and geo-ecosystem functioning in the short term. Yet, despite some discrepancies, the data also showed the occurrence of self-restoration processes of the geo-ecosystem over the long term. © 2016 Elsevier B.V.


Goldshleger N.,Soil Erosion Research Station | Chudnovsky A.,Boston University | Ben-Binyamin R.,Soil Erosion Research Station
International Journal of Remote Sensing | Year: 2013

Soil salinity is one of the most common soil degradation processes, found particularly in both arid and semi-arid areas. Salt (Cl)- and sodium (Na)-affected soils impact vegetation and plant communities. Under these conditions, soil salinity can serve as an indicator of vegetation salinity. In this study, we explored whether spectroscopy could quantitatively assess foliar Cl and Na concentration as indicators to assess salinity in tomato plants. Reflectance spectra of soil samples were obtained in the 400-2500 nm region using a hyperspectral radiometer. The relationship between the Na and Cl contents of tomato plants growing in various saline environments and soil spectral reflectance was determined using partial least squares regression. The Cl-content model was more accurate for determining leaf salinity (R2 = 0.92, root mean square error of prediction (RMSEP) = 0.2%) than the Na-content model (R2 = 0.87, RMSEP = 0.6%). We conclude that reflectance spectroscopy is potentially useful for characterizing the key properties of salinity in growing vegetation and assessing its salt quality. The results of this study can serve as a starting point in precision agriculture for salinity measurements in tomato fields and could be further upgraded for use by airborne/satellite remote-sensing modes. © 2013 Copyright Taylor and Francis Group, LLC.


Zaady E.,Israel Agricultural Research Organization | Arbel S.,Soil Erosion Research Station | Barkai D.,Israel Agricultural Research Organization | Sarig S.,The Katif Research Center
Journal of Arid Environments | Year: 2013

The natural landscapes of semiarid areas worldwide comprise a series of scattered patches of shrubs within a matrix of biologically crusted soils (BSC). As BSCs are considered ecosystem engineers the relationships between the BSC and the shrub patches determine system functioning. The objective of our study was to investigate long-term effects of agricultural practices on biological soil crusts and their influence on hydrological aspects of a semiarid ecosystem. During 1991, we experimentally simulated five of the area's agricultural practices; 1) Scraping - the topsoil was removed to a depth of 2 cm, 2) Spraying - phototrophic organisms were chemically killed with herbicide, 3) Mowing - perennial vegetation was cut and spread to simulate grazing practices, 4) Car track - a heavy roller was used to simulate car-tracks, 5) Control - undisturbed natural plots. Sixteen years later, in 2007, these agricultural practices were found to have a long-term effect on the crusted soil surface and the related soil-surface properties. Mowing and car-track treatments led to decreased overland runoff and increased hydraulic conductivity, whereas scraping and spraying treatments led to increased overland runoff production and decreased hydraulic conductivity. We conclude that the practices had a long-term residual impact on BSC succession and related soil surface properties, which affected the hydrological processes and system functioning. © 2012 Elsevier Ltd.


Shoshany M.,Technion - Israel Institute of Technology | Goldshleger N.,Soil Erosion Research Station | Chudnovsky A.,Boston University
International Journal of Remote Sensing | Year: 2013

Agricultural land degradation is a global problem that severely hampers the production of food needed to sustain the growing world population. Mapping of soil degradation by remote sensing is instrumental for understanding the spatial extent and rate of this problem. Methods aimed at detecting soil loss, soil drying, and soil-quality deterioration have been demonstrated in numerous studies utilizing passive and active remote sensors. This review presents a short description of each form of soil degradation, including data regarding known extents and rates, and then reviews the methods with respect to direct and indirect modelling approaches. Two types of obstacles to achieving wide regional detection of soil degradation are revealed. The first concerns the complex and non-unique relationships between remote-sensing indicators and different soil properties, such as roughness, soil moisture (SM), soil salinity, and organic matter content. The second concerns the difficulties involved in acquiring data on subsurface soil properties. In view of these difficulties, we recommend expanding the use of phenomenological models capable of estimating soil-degradation potential according to combinations of environmental conditions, thus enabling remote-sensing efforts to be focused on local areas where the environmental threat is highest. The second avenue for improving the contribution of remote sensing on a wide regional scale involves the application of integrative methods, such as those based on hyperspectral, multisensory, and multitemporal approaches, as well as those that incorporate environmental information (such as topography, soil types, and precipitation). © 2013 Copyright Taylor and Francis Group, LLC.


Stroosnijder L.,Wageningen University | Moore D.,Wageningen University | Alharbi A.,Qassim University | Argaman E.,Soil Erosion Research Station | And 2 more authors.
Current Opinion in Environmental Sustainability | Year: 2012

Drylands cover 41% of the global terrestrial area and 2 billion people use it for grazing and cropping. Food security is low owing to institutional and technical constraints. Absolute water scarcity and also the inability of crops to use available water are major technical issues. Significant progress has been made in identifying land management practices that improve water use efficiency in terms of more crop per drop. Examples are presented that improve infiltration and storage of rainwater, reduce evaporation losses, harvest and conserve water in the Mediterranean region and Africa and use treated waste water for irrigation. Drylands show a wide diversity and therefore, require appropriately adapted best mitigation practices and strategies. © 2012 Elsevier B.V.


Lugassi R.,Tel Aviv University | Ben-Dor E.,Tel Aviv University | Eshel G.,Soil Erosion Research Station
Remote Sensing of Environment | Year: 2010

Heterogeneous heat was applied to a homogenous soil surface to simulate a natural fire event. Subsequently cooled soil samples were evaluated spectrally and a spectral-spatial cube was generated corresponding to the burned area. Heat-induced spectral changes associated with thermal effects on soil minerals were observed across the entire spectrum, including: soil color changes (iron-oxide transformation); shifting absorption bands (iron-oxide transformation and illite/calcite ratio); changes in spectral shape (illite/montmorillonite ratio); disappearing absorption features (unknown); and changes in the overall brightness (soot). A model was developed using Partial Least Squares (PLS) to predict maximum soil surface temperatures, measured using thermocouples, from soil spectral reflectance. Thus, this proof-of-concept study demonstrates that soil spectroscopy reveals important information about soil temperature history and as such, represents a promising tool for viewing fire events retrospectively. © 2009 Elsevier Inc. All rights reserved.


Stavi I.,Dead Sea and Arava Science Center | Fizik E.,Soil Erosion Research Station | Argaman E.,Soil Erosion Research Station
Geomorphology | Year: 2015

Forestry activities are a widely accepted means of restoring degraded lands. In the semi-arid Negev of southern Israel, extensive lands have been modified for runoff-harvesting-based afforestation projects comprised of contour bench terrace systems (also called shichs/shychs/shikim). However, some alarming evidence in recent years calls for assessing the environmental impact of these forestry lands. We assessed the effects of contour bench terrace afforestation systems on herbaceous vegetation productivity and the soil quality of the uppermost layer (0-5cm depth) and the 0-80cm profile, in 2-year-old and 9-year-old afforestation systems, and natural, unperturbed hillslopes in the multi-aged Ambassadors' Forest. Results revealed considerable differences between the sink (contour bench terraces) and source (inter-terrace spaces) areas of the afforested lands. Normalizing data to the relative cover of these areas revealed similar herbaceous vegetation biomass and soil wetting front values for the natural hillslopes (1.47Mgha-1 and 59.8cm, respectively) and 9-year-old afforestation systems (1.64Mgha-1 and 59.3cm, respectively), and significantly lower values for the 2-year-old systems (0.07Mgha-1 and 49.4cm, respectively). Unexpectedly, the opposite trend was recorded for soil hygroscopic moisture content, which was significantly smaller for the natural hillslopes (1.7%) and 9-year-old systems (1.9%) than the 2-year-old systems (3.2%). Soil bulk density was also significantly affected by afforestation treatment, following the trend 2-year-old systems>9-year-old systems>natural hillslopes (1.57, 1.55, and 1.53Mgm-3, respectively). Soil penetration resistance varied greatly throughout the 80-cm soil profile. There was no significant effect of afforestation treatment on soil gravimetric moisture content (in the spring). Overall, soil quality and herbaceous vegetation cover were only slightly greater on the north-facing aspects than those on the south-facing aspects. We concluded that the establishment of contour bench terraces increases geodiversity on a hillslope scale, but removes the surface soil (A horizon) from extensive areas, increases soil compaction, and decreases herbaceous vegetation production, adversely affecting soil quality, pastoral productivity, and ecosystem functioning and health in the short term. However, over the long term, self-restoration of small-scale geodiversity and functioning of the geo-ecosystem is suggested to improve soil quality and increase herbaceous vegetation productivity in these dryland afforestation systems. © 2014 Elsevier B.V.

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