Hossain Shohab Arkhazloo; H. Emami; Gholam Hosain Haghnian; Abazar Esmali
Abstract
Introduction: Gully erosion is an important type of soil erosion in Iran and Ardebil province (Moghimi and Salami, 2011; Khatibi, 2006). Increasing the cross section of gullies is an indicator for gully developing (Deng et al, 2015). Topography and soil properties are two important factors in gully developing ...
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Introduction: Gully erosion is an important type of soil erosion in Iran and Ardebil province (Moghimi and Salami, 2011; Khatibi, 2006). Increasing the cross section of gullies is an indicator for gully developing (Deng et al, 2015). Topography and soil properties are two important factors in gully developing in various regions of worldwide (Poesena et al, 2003). Despite the importance of soil properties in gully erosion, the direct effect of these agents was less investigated and few researches have been carried out to the effect of physical and mechanical soil properties on gully erosion. Therefore, the objectives of this research were to determine 1) the effect of topography on gully erosion, 2) effect of surface and subsurface soil physical and mechanical properties on increasing the cross section of gullies and 3) to select the most important soil properties affect developing the cross section of gullies in three regions of Ardebil province (Ortadagh, Molla Ahmad, and Sarcham). In addition, the relationship between the most soil properties and topographic agents was investigated
Materials and Methods: The effect of topography on gully erosion was investigated by using of two methods i.e. topographic threshold of gully forming (as , where A and S is gully watershed cross section and slop, respectively, a and b is local coefficients) and the relationship between slope classes with gullies density. In regard to catchment characteristics, a set of similar gullies was selected in each region and the changes of cross section area for gullies in four points along its length were measured as indicator of gully development during two years. 17 physical and mechanical of surface and subsurface soil properties in each point were measured and the most important properties that affect on gully development were selected based on principle component analysis (PCA) method. Finally, the stepwise regression model was fitted to the soil properties selecting from PCA for gully's development in each region.
Results: The relationship between Slope classes and gully density showed that in MollaAhmad region gully density was increased with increasing the slope. In OrtaDaghregion, similar trend was observed up to 20-30% slope, while in Sarcham region these was no relationship between slope classes and gully density. According to the topographic threshold it seems that runoff is the main agent for gully forming in MollaAhmad,but in Sarchamthe piping and tunnel erosion might have caused gully formation and in Ortadagh both surface and subsurface flows were recognized as effective agents for gully formation. Increasing values of the cross section for the selected gullies during 2 years was 0.9, 0.6, and 0.8 m2 for Ortadagh, MollaAhmad, and Sarcham regions respectively, which were 41, 44 and 61 percent more than their initial cross sections. Among mechanical soil properties, liquid limit (LL), plastic limit (PL) and shear strength (SS) had the negative and significant correlations with increasing the cross sections of gullies in 3 regions. Among the particle size fractions, Water dispersible clay had the most effect on increasing the gully’s cross sections and except for surface depth of Molla Ahmad, its correlation with gully’s cross section was significant. Principle component analysis (PCA) demonstarated that in MollaAhmad and Ortadagh mainly mechanical properties of soil and aggregate stability had the more effect on increasing the gully cross section, but in Sarcham soil particle size classes and aggregate stability indices had more effect on gully’s cross section.
Conclusion: According to topography threshold, it can be concluded that surface runoff is the main agent for gully forming in MollaAhmad and gully density increases by increasing the slope classes. In this region the effect of surface runoff on surface soil erosion was sever. In Sarcham there was no relationship between slope and gully density and it was found that the subsurface flow is predominant factor for gully forming. In OrtaDagh both surface and subsurface flows were the main factors for gully forming, so due to increasing the surface flow up to slope 20-30% class, maximum gully density was noted in this slope class and the effect of subsurface soil properties in developing gully cross section was higher than surface soil properties. In general, the relationship between gully density with slope classes, topographic threshold and soil physical and mechanical properties which were effective on gully development indicated the close consistency between the type of hydrologic flow in gully forming and the most important soil properties on increasing the gully’s cross section.
Sh. Asghari; S. Dizajghoorbani Aghdam; Abazar Esmali
Abstract
Knowledge of the spatial distribution of soil properties is the major issues in identifying, program planning, management and utilization of soil and water resources. This study was carried out to investigate the spatial variability of some important soil physical quality indices including sand, silt, ...
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Knowledge of the spatial distribution of soil properties is the major issues in identifying, program planning, management and utilization of soil and water resources. This study was carried out to investigate the spatial variability of some important soil physical quality indices including sand, silt, clay, mean weight diameter of aggregates (MWD), organic carbon (OC), saturated hydraulic conductivity (Ks), saturated water content (θs) and bulk density (Db) in the three adjacent land uses i.e. forest, agriculture and range land located at Fandoghlou region of Ardabil. Totally, 100 soil samples were systematically (100 × 100 m grade) taken from 0-15 cm depth in spring 2013. At first, the accuracy of Kriging and inverse distance weighting (IDW) geostatisticaly methods in mapping of studied parameters was evaluated then the final map was presented. The values of nugget effect to sill ratio for clay, sand and silt were 0.5, 0.47 and 0.49, respectively so these parameters have an average spatial structure. The values of above mentioned ratio for OC, Db, θs, Ks, and MWD were obtained 0.002, 0.014, 0.0007, 0.05 and 0.008, respectively, indicating strong spatial structure. According to the R2 criteria, Kriging method in estimating clay, sand and silt and IDW method in estimating MWD, OC, Ks ،θs and Db had the highest accuracy. The final map indicated that forest land had higher OC, MWD and Ks and lower Db compared with agriculture and range land. The results of this research showed that soil physical quality of the studied region in agriculture and range land uses was lower than forest lands.
Z. Lotfi Arpachaei; Abazar Esmali; kazem hashemimajd; n n
Abstract
In modern agriculture, the preparation of soil fertility map seems to be necessary to plan for appropriate using of fertilizers for crops. This study was conducted to prepare a distinct map for evaluating soil fertility according to soil chemical properties in 136 soil samples of Ardabil plain in Ardabil ...
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In modern agriculture, the preparation of soil fertility map seems to be necessary to plan for appropriate using of fertilizers for crops. This study was conducted to prepare a distinct map for evaluating soil fertility according to soil chemical properties in 136 soil samples of Ardabil plain in Ardabil province. To achieve this purpose, the available K and P, total N, EC, pH and organic matter of soil were mapped using geostatistical Kriging estimator into Geographic Information System (GIS) by ArcGIS9.3 software. The Analytical Hierarchy Process (AHP) was used for weighting soil fertility factors as the input data. Then a membership functions was defined for each factor by factorial scoring and the map of soil fertility was prepared and classified for wheat and potato by using AHP technique into GIS program. The results showed that 74.84, 3.59, 19.3 and 2.32 percentage of lands for wheat cropping were classified based on soil fertility into groups of weak, moderate and suitable, respectively while for potato it was 24.88, 27.57, 7.19 and 40.34 percentage, respectively. As a final result, this type of distinct soil fertility map for different crops could assist us to manage the appropriate using of lands and fertilizers.
