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.
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.
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.
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.