The deleterious effects of sodium-induced secondary alkalinization on soil structure and hydraulic properties of calcareous soils can vary widely. This study aims to evaluate the impact of sodicity ...and leaching velocity on the physical and hydraulic properties of a calcareous clay-rich soil. Two application rates of tap water (TW) and sodic water (SW) are considered: fast leaching, equal to the saturated hydraulic conductivity, Ks, and slow leaching conditions, equal to have 1/2 Ks. For the TW and SW experiments, up to 14 and 26 leaching cycles were performed in duplicates, respectively. After the leaching applications, the PVC columns were cut horizontally, and undisturbed samples were removed from the different depths. It was observed that neither water quality nor water flow rate significantly affected water stable aggregate percentages. TW did not affect soil total porosity and bulk density except at the bottom of the column. On the other hand, there were remarkable reductions in soil porosity and bulk density in the SW leaching experiments ranging from 8.8 to 12.5% and 7.4–13.8%, respectively. High Na concentrations in leaching water caused aggregate swelling and dispersion, leading to reduced Na+ and enhanced Ca2+ transport to the lower portions of the soil column. In the lower layers, the severity of sodium-induced dispersion was restricted by calcium, which was exchanged by the excess amount of Na from the upper layers, maintaining soil particles flocculated. Ca2+, which tightens the soil particles and aggregates together, limited Na-induced disruption of the soil aggregation. Nonetheless, particles that broke away from aggregate did influence the hydraulic properties of the soils. Overall, the experiments revealed that although the physical and hydraulic properties of the soil are affected by the sodic waters and the flow rates, this effect is reduced in calcareous soils due to their strong bonding feature.
•Deleterious effect of Na on aggregation is less evident in calcareous clay-rich soil.•Sodium-induced degradation is more pronounced in the upper layers of calcareous soil.•Aggregates of well-structured calcareous soils resist compaction caused by Na.•Increased flow rates of sodic water accelerate soil degradation.•The higher the limestone and clay content, the more stable the soil structure.
•Examination of a simple alternative approach to laborious wind tunnel experiments.•Introducing sandblasting technique for wind erosion assessment on crusted soils.•Analysis of rainfall-induced crust ...abrasion by sandlasting technique.•Investigation of the variations in soil loss through changing abrasion conditions.•SOC' role on aggregate size distribution and crust strength.
Surface crust significantly affects the amount of soil detachment and transport during wind erosion events. In this context, the availability of a simple procedure to measure the detachment potential of the soil crust against impacting wind-blown particles provides the benefits of assessing the soil's vulnerability for saltation which accounts for50 to 90% ofthe total sediment transport by wind. This study aims to demonstrate a simple procedure designed in the National Soil Erosion Research Laboratory (USA) that directly measures particle detachment from a soil crust subjected to different amounts of impinging sand grains. The technique uses a conventional sandblasting tool with a control timer to blast sand particles (q, g) ranging from 0.44 to 3.55 g during the test. The soils used for the experiment were two silt loams, Palouse and Nansene, sampled from US Pacific Northwest. Besides testing sandblasting technique for measuring the abrasion index or relative abradibility of the soil crust, the technique has also been evaluated for effects of soil organic carbon (SOC) and aggregate (ASD) and particle (PSD) size distributions on crust strength. Results showed that an increase in q generally caused a significant increase in soil loss through abrasion (A, g) (P < 0.05*). The technique is very sensitive to cropping and management history considering the role of SOC, ASD, and PSD on crust formation mechanisms. This technique is low-cost and can quickly measure soil crust abrasion under impacting sand grains without the need to use a wind tunnel and the associated laborious sample preparation and testing procedures.
Time-dependent and phenology-based erodibility assessments in agricultural areas are extremely important for a more accurate evaluation of erosion. This paper aims to investigate soil erodibility ...factor (RUSLE-K) of the “Revised Universal Soil Loss Equation (RUSLE)” model in terms of phenological and seasonal variations in the 50 different winter wheat growing parcels with the interactions other dynamic RUSLE factors (RUSLE-R, RUSLE-C). For that, parcel-based erosion assessments were performed with the help of Dynamic Erosion Model and Monitoring System, digital elevation model, and satellite images in Polatlı, Ankara. Findings showed that RUSLE-K factor varied from 0.0150 to 0.0357 t ha h ha-1 MJ-1 mm-1 during the period the seeding germination to the end of the tillering from autumn to spring, and the lowest RUSLE-K was obtained when the plant was in the three-leaf stage. After the frost-free period, corresponding to the flowering and fertilization stages of the wheat plant, the RUSLE-K values changed between 0.0786 and 0.0976 t ha h ha-1 MJ-1 mm-1. This reveals that erodibility can vary up to nine times due to seasonality. However, the other dynamic model factors are not taken into consideration. Considering all dynamic factors on soil losses, the change coefficients from the highest to the lowest were obtained for RUSLE-R, RUSLE-K and RUSLE-C, respectively. These changes caused soil losses to change by 82% during the year. So, this study is expected to shed new light on studies of wheat or other commonly cultivated crops to accurately assess the water erosion risk as a significant land degradation problem.
Soil susceptibility to detachment and transport sub-processes of erosion is generally controled by the aggregate breakdown mechanism. Measuring particle size and aggregation to the estimate ...erodibility potential of soils is important under erosive rainfall conditions. The Aggregate Size Distribution (ASD) is one of the most important determinants of soil structure along with soil organic matter content for describing the efficiency of applied, sustainable management strategies. This study aimed to compare the performances of three different aggregate size distribution models to predict the characteristic aggregate size parameter (median diameter, D50) for eroded sediment from interrill erosion processes of Rain-Splash Transport (RST) and Raindrop Impacted Flow Transport (RIFT). The ASDs of 1143 collected sediment samples from the RST and RIFT processes were measured and modeled by the Log-normal, Fractal, and Weibull approaches. The D50 value, as a characteristic parameter for aggregate size distributions, derived from the cumulative ASD curve was compared for soils from different land use types and different slope and rainfall intensity conditions. The performance of each model was evaluated using the Mean Square Error (MSE) and Coefficient of Determination (R2). The Weibull approach was the most accurate model showing the best fit with the lowest MSE values (0.0002 ≤ MSE ≤ 0.0048) and having the greatest R2 values (0.936 ≤ R2 ≤ 0.998) when compared with the Log-normal and Fractal models. Herewith, for semi-arid land use and soil, specific shape and scale parameters for the Weibull distribution, the respective ASDs were successfully re-generated for modeling the eroded sediment of the simulated RST and RIFT interill processes.
In modeling studies, the use of spatial data derived from geographic information systems and remote sensing applications to simulate the impact of phenological and seasonal changes on soil loss has a ...promising effect on the accuracy of predictions. The objective of this work was to estimate the C-factor (cover management) as a dynamic-factor RUSLE (revised universal soil loss equation) model based on an NDVI (Normalized Difference Vegetation Index) approach derived from high-resolution Landsat 8 and Landsat ETM7 satellite images for 140 different rain-fed wheat parcels in terms of seasonal and phenological-based by the integrated use of remote sensing and GIS. Overall, it was found that the highest
C
values, an average of 0.70, were estimated for the emergence period of the wheat, while the lowest value of 0.06 was found in the booting period. Seasonally, the estimated average
C
values in these parcels were 0.69, 0.63, 0.13, and 0.44 for the autumn, winter, spring, and summer, respectively. Corresponding soil losses for those seasons were 1.70, 1.55, 0.28, and 1.13 t ha
−1
year
−1
respectively. Comparatively, without considering the phenological growing periods of wheat, the annual predicted soil loss rate was 11.5% higher than the conditions considered. The present study concluded that an assessment of seasonal and phenological changes in the C-factor for fragile ecosystems with weak crop-cover development could significantly improve the accuracy of the RUSLE model predictions and effectively manage limited soil and water resources.
•Sensor-based cohesion measurement apparatus was prepared for fluidized bed approach.•Pressure drops and flow rates in soil mass were monitored under upward flows.•The relationships between soil ...properties and soil cohesion were analysed.•Soil cohesion increases with increase in fine particle and organic matter contents.•Changes in lime contents as well as particle size have effect on cohesive forces.
Measuring cohesion (Co) as a simple and reliable factor with the fluidized bed approach to assess the inherent resistance of soils against destructive forces corresponding to the separation of particles from the soil mass is considered a promising research area in place of alternative methods by rainfall–runoff experiments. However, the approach has only been tested for very limited soil types, and there is a need to analyze its suitability for more diverse soil conditions, especially for cohesive soils having higher clay, organic matter, or lime contents. This study aimed to evaluate cohesion for twenty soil types representing nine different texture classes that differed significantly in terms of their intrinsic properties with an “Automated Soil Cohesion Measurement Apparatus”. This device was equipped with modern electronic sensor technologies designed to function and measure cohesion with the fluidized-bed approach. In the measurements, pressure drops that occur while the water pressure increases gradually as it passes through the soil mass are visually and electronically monitored and continuously recorded during the experiments with the help of precise differential pressure and weight sensors. Effects of the changes in intrinsic soil properties such as particle sizes, organic matter contents, and lime contents in terms of coagulation potentials on cohesive forces were observed with the designed apparatus. Related to that, the analysis of variance and the Fisher’s least significant difference tests indicated that the cohesion (Co) and the flow velocity at fluidization (Vf) values were significantly different by soil type (p < 0.05). Fraction of the fine silt-sized particles (FNSI) was highly correlated with Co and Vf, and explained much of the variance for the cohesive conditions. In addition, the Co values in coarse-textured soil types with low cementing components and soils having greater sand contents were four times lower than those of heavy textured and clay-bound soils. The approach and the designed apparatus successfully simulated changes in internal soil conditions in terms of measured Co and Vf values.
► A comparative study for aggregate stability of loamy sand soils was performed. ► Short term effects of compost applications on soil structure were investigated. ► Six different aggregate stability ...approaches were compared. ► Detachment index (DI) statistically varied with applied aggregate stability methods. ► Using single sieve size or multiple sieve sizes made no difference for coarse soils.
The bio-dynamic relations of soil aggregate stability, as a widely accepted soil quality indicator, with the physical, chemical and biological soil properties are very complicated in the soil system, and there exist many methods of measuring the soil aggregate stability to establish these relations. This study aimed to evaluate different aggregate stability methodologies for loamy sand soils. The applied aggregate stability methods of the research chiefly involved sieving soil samples through either multiple sieves or a single sieve using operations of wet sieving, dry sieving, pre-wetting, slow wetting, fast wetting and mechanical breakdown. These were used either alone or in combination, and the methods were compared in terms of a detachability index (DI), which is the ratio of the Mean Weight Diameter after wet sieving (MWDW) to that before wet sieving (MWDD). The statistical analysis showed that the mean values of the DI for wet sieving by multiple sieves, fast wetting and mechanical breakdown varied significantly (*P<0.05) from other methods. Clearly, depending upon the magnitude and extent of aggregate destructive forces, the DI changed significantly, and simulating diverse physical processes which could operate sequentially or simultaneously resulted in different consequences in terms of the aggregate stability.
Functional relationships between soil erodibility equations of empirically-based revised universal soil loss equation and process-based water erosion prediction project models were investigated using ...new datasets from rainfall simulation experiments to overcome conceptual differences of models in estimating soil erodibility. Erodibility potentials of two different soils were quantified for three different initial soil moisture conditions, and relations between the process-based erodibility, partitioned as interrill erodibility, rill erodibility and critical shear stress, and empirically-based erodibility were examined. A process-based soil erodibility assessment within the universal soil loss equation was attempted. Statistically significant differences are found when considering the effects of surface hydrologic conditions on soil erodibility. Process-based soil erodibility estimates under dry conditions were found to be comparable with original water erosion prediction project datasets. The results showed that procedure could be useful for tapping into the large number of datasets available and building the next generation of process-based erosion models.
•Sodicity was investigated in a semiarid Calcisol of the Great Konya Basin.•pH gradually increased while the EC decreased with irrigation water treatment.•Water quality strongly influenced ion ...concentrations in calcareous soils.•Short-term leaching with poor-quality waters restricts permeability.•Poor quality irrigation treatments increase the risk of secondary salinization.
The often-indispensable use of poor-quality irrigation water in drylands instigates diverse physicochemical dynamics leading to soil salinization and sodicity which are recognized as major contributors to land degradation. This study aimed to examine the effects of water quality and irrigation mode on solute transport conditions in terms of ion exchange of colloidal particles. Laboratory studies with undisturbed soil columns were carried out with two water treatments - tap and sodic waters - as well as two water flow velocities: fast leaching which corresponds to Darcy velocity equal to the saturated hydraulic conductivity and slow leaching equal to half the fast-leaching case. Results indicated that the flow velocities did not significantly influence pH, EC and ion concentrations due to the high calcium carbonate and clay contents of the soil which make the soil less permeable. However, flow velocity rapidly decreased in the fast leaching compared to that in slow leaching as the sodic water was applied. This reveals the destructive effect of Na+ in the soil. The EC rapidly dropped at the beginning of leaching for both water qualities opposite to pH, then became steady. All sodic applications caused an increase in Na+ till the end of treatments. This also resulted in variations in measured soluble anions. In general, sharp decreases in highly soluble anions were observed in all treatments, leading to an increase in HCO3–, especially for sodic treatments. Overall, sodicity caused significant changes in flow dynamics and ion concentrations and created favorable conditions for secondary salinization in this low permeable soil system.
Direct measurements, models, and risk maps play significant roles in assessment and monitoring of wind erosion cases. Although active and passive traps allow researchers to measure point sediment ...transports directly, it is also possible to make geostatistical analysis of wind erosion with grid and random sampling at multiple points. Geostatistical models can be used in multi-sample eolian researches to improve model success and update model parameters. The present study was conducted for case-based geostatistical analysis of sediment transport rates (STRs) over two adjacent dunes (plot A and B) with different vegetation cover rates between 22 May and 15 June 2011. The plot A has a vegetative cover ratio of 30%, while the plot B has a vegetation cover ratio of 2% and sand content of the plots is 88%. Actual mass transports were measured with BEST sediment traps. A total of 19 BEST sediment trap assemblies were placed randomly over the plot A and 21 were placed over the plot B. A climate station was installed over the research site to record climate data throughout the experimental period. There were two wind erosion cases during the research period.
U
test indicated that differences in sediment transport rates of the plots for each case were significant (
p
< 0.00). Spatial analyses of STRs (kg m
−1
h
−1
) also exhibited case-based differences. While nugget effect was observed in case 1 of the plot B, the other case in both plots were modeled with spherical model. Maximum likelihood distances in plot A and B were respectively identified as 61 m and 1 m in the first case and as 13 m and 30 m in the second case. Total mass transport was measured as 112 kg m
−1
in plot A and as 2162 kg m
−1
in plot B. Consequently, it was found that 30% vegetation cover reduced the total mass transport dramatically.
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