JWSS - Journal of Water and Soil Science

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In quantitative land suitability evaluation, economic aspects land evaluation such as impact of environmental physical factors on crop production and the amount of yield per surface unit are considered. The purpose of this research was to study quantitative land suitability of northern Baraan area located in eastern Isfahan. The study was a continuation of the previously accomplished qualitative land suitability evaluation of the area. The economic studies include economic data collection, matching inputs and outputs and gross margins analysis. Radiation-thermal production potential of the crops was calculated based on plant physiology and temperature (FAO model), which was 10.45, 10.11, 13.64 and 11.93 ton/ha for wheat, barley, maize and rice, respectively. Radiation-thermal production potential, observed and marginal yields and the results of the qualitative land evaluation were used to perform quantitative land evalution and to determine the corresponding suitability classes. The predicted yield in different land units varies between 1.64 and 9.17 ton/ha for wheat, 1.81 and 9 ton/ha for barley, 2.06 and 9.42 ton/ha for maize and 2.35 and 7.14 ton/ha for rice. Presence of significant statistical correlation between the observed and the predicted yield values reveals the validity of the evaluation methods used. The results from quantitative land evaluation show that most of the land units are slightly to moderately suitable for wheat, barley, maize and rice, while a few are not. The best land utilization type in each land unit can be selected through a combined consideration of quantitative land evaluation results, benefitability of each land unit and impact of the land use on the soil. Rice cultivation is not recommended in the study area, because of its adverse effect on soil physical properties and soil drainage.

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For the study of field wind erosion and the design and evaluation of wind erosion control techniques, detailed observations of soil particle transport and vertical destribution of eroded soil particles are needed. The objectives of this study were: 1) To describe one device for soil transport particle measurement, i. e. the BSNE sediment catcher and 2) To assess vertical distribution of wind–eroded sediment with height in eastern Isfahan. The BSNE sediment catcher is a wind erosion sampler that traps eroded material at seven heights of 0.24, 0.60, 1.08, 2.00, 3.00, and 4.00 m above the soil surface. Each trap consists of a steel container with an inlet and outlet, mounted on a wind vane that rotates about a central pole. Before using the sampler in the field, it was tested and calibrated in the wind tunnel. The results showed that the average trapping efficiency with speeds ranging from 5.2 to 7.2 m sec^-1 for 4 different wind–eroded sediments was 0.44 to 0.68. However the trapping efficiency depended on wind speed, particle size distribution, particle density and type of sediment. The sampler had the lowest efficiency for particles < 44 μm. A BSNE sediment catcher was installed in Babaii Air Base. After a sampling period, the sediment in each trap was collected and weighed. The trapped materials were a mixture of saltation and suspension particles. Vertical distribution of wind–eroded sediment showed that the amount of soil collected decreased with increased height and the percentage of fine particles (<63μm) increased with height. The amount of trapped materials for each cm2 frontal intake with increased height were 12.00, 3.42, 1.44, 1.56, 0.75, 0.21, and 0.39 g cm-2, respectively, for the one sampling period.

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Cultivating rangeland to be shifted to crop land farms commonly causes soil degradation and runoff generation. This study was conducted to evaluate the cultivation effects on runoff generation and soil quality. The experiment was performed in a rangeland and a 40-year cultivated land located at two slope positions (back slope and shoulder) of a hillside in Dorahan, Chaharmahal & Bakhtiari Province. A 60±5 mm.hr^-1 rainfall intensity was simulated by a rainulator. Organic matter, mean weighted diameter, saturated hydraulic conductivity, collected runoff and sediments were measured. The differences between the means were tested using T-test. Results showed 35, 53 and 8% increases in the organic matter, mean weighted diameter, and saturated hydraulic conductivity in back slope, respectively. The increases in these parameters in shoulder position were 39, 60 and 33%. The values for runoff and sediments in back slope were 3 and 8 times greater than in other similar positions while the values in the shoulder position were 11 and 55 times greater than the same values in other positions.

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Investigation of paleosols plays a great role in paleoecological and paleoclimatological studies. They are also important in soil survey and planning, as they exhibit characteristics different from younger soils. Paleosols are those soils which formed under conditions different from present ones, and are either buried within sedimentary sequences or those which lie on persisting surfaces. Although such soils are widespread in central Iran and Zagros Zone, they have not been studied adequately. Paleosols are identified by different parameters such as morphological, physical, chemical, mineralogical, and micromorphological characteristics. In this study, morphological, physical, and chemical properties of three paleosols from Isfahan and Chaharmahal & Bakhtiary provinces were investigated. The profiles were on different landforms including alluvial fan, dissected old plain, and old lagoonal deposits. Soil profile in Segzi site, on old lagoonal deposits, had a very dark and thick layer at a depth of 45-60 cm containing some macrofossil shells. This shows that this area was covered by brackish water during the early Holocene. In Sepahanshahr profile, presence of strong clay coating and high concentrations of CaCO₃ indicates a wetter environment in the past than the present conditions with a precipitation of only 100 mm. In Emam-Gheis profile, a buried paleosol was identified with strong clay coating and free CaCO₃ horizons that shows more humid conditions. Evidences obtained from the three paleosols studied indicate that effective moisture in central Iran and Zagros regions during Late Pleistocene had been higher than its present levels.

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Cation exchange capacity (CEC) is one of the most important chemical characteristics which influences soil quality from different aspects. At the same time, CEC is an input parameter of many computer models being applied in soil science and agriculture. Methods of CEC determination are always time-consuming and laborious. Therefore, developing a model for CEC estimation from other soil properties is essential. The objective of this study was to understand the associations between CEC (as a dependent variable) and sand, silt, clay, organic matter and pH (as independent variables). In this study 464 soil samples from A, B, and C horizons of different soils were used. Results revealed that CEC is negatively correlated with sand (r=-0.389***) and is positively correlated with organic matter (r=0.772***), clay (r= 0.391***) and silt (r= 0.233***). No significant correlation was observed between CEC and pH. Stepwise regression analysis showed that both organic matter and clay enter the model and that coefficients of determination (r²) for the multiple models are higher than those of simple linear correlations. Other parameters could not increase the r² considerably. Correlation analysis on data from A, B, and C horizons revealed that the CEC of organic matter in different horizons are not the same. Separation of Aridisols could not increase the r² of the model and the accuracy of the estimations. Correlation studies in acid soils showed that the contribution of organic matter in CEC is much higher than that of clays.

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Clay minerals deserve special attention as they play a crucial role in many soils. The clay mineralogy of five gypsiferous soils from different landforms in eastern Isfahan was investigated using X-ray diffraction (XRD). In addition, soil aggregates and wind-deposited sediments were examined by scanning electron microscope (SEM) and analyzed by energy dispersive X-ray analyzer (EDX). The results indicate the presence of palygorskite, mica, kaolinite, chlorite, and quartz with a trace amount of vermiculite and randomly interstratified layers in all soils. Smectite occurs in soils of both the piedmont plain and old river terrace, but not in the alluvial fan soils. Mica, chlorite, quartz, and kaolinite were probably inherited from the parent material. Palygorskite seems to increase with depth in the alluvial fan, whereas, in the old terrace soils, this clay mineral decreases with depth. Palygorskite present in alluvial fan soil appears to have been formed authigenically when the basin was covered with shallow hyper-saline lagoons toward the end of the Tertiary. Palygorskite in the old terrace seems to be mostly detrital and an eolian origin of palygorskite is likely because a large amount of palygorskite is present in upper soil horizons. A higher proportion of smectite in deep soils of the old terrace, as compared with palygorskite, suggests the possibility of authigenic formation of smectite from palygorskite. .

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Satellite data use is finding global applications because they provide repeated cover, broad information, high electromagnetic spectral resolution, and software-hardware compatibilities. This study aims to evaluate of the Landsat TM data capabilities in land-use mapping of Bazoft River basin (Chahar Mahale Bakhtiary Province). Six spectral bands of the Landsate TM were employed to produce land-use map of the Region. The date of image acquisition was May 5^th, 1998. Performance of the geometric correction completed with RMSE= 1.008 pixels. Various image enhacement methods (e.g. FCC, filtering and Vegetation Indices) were used to study the different land-covers. Field investigations were carried out using a GPS, 1:50000 scale topographic map and false color composites images. Heterogeneous land-use units were studied in 62 sample sites estimating percentage of vegetation cover. A regression analysis was performed between percentage vegetation covers and vegetation indices values of NDVI, RVI, SAVI, DVI, TSAVI₁, NRVI and MSAVI₂. Results show that NDVI, SAVI, TSAVI1, NRVI and MSAVI₂ have high correlation coefficients. But RVI, DVI and PVI have low correlation coefficients. The resulting values of vegetation cover were density sliced to produce the land-cover map. After supervised classifications and density slicing of Vegetation Indices, classifacation accuracy was assessed and, finally, land-use map of the study area was produced with Hybrid classification method. Supervised classification with maximum likelihood method was the best technique for land-use mapping in the study area the total Kappa index was %87. In general, detection of some land-use classes through single date TM data is not feasible, these include: scattered forest trees with cultivated understory, annual grasses, and fallow lands. Also TM digital data are incapable of distinguishing small and separated rural constructions or soil-covered routes.

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Soil pollution and accumulation of heavy metals in crops in industrial areas are the most important bioenvironmental problems that threaten the life of plants, animals and humans. The objective of this study was to determine Ni, Mn and Cd distribution in soil and crops shoots around the Mobarakeh Steel Plant. In this study, we separated 50 zones based on soil utility maps taking into consideration the dominant wind direction (south-western to north- eastern). In each zone, soil was sampled at 0-5, 5-10, 10-20 and 20-40 cm depths (200 samples) and DTPA-extractable concentrations of Ni, Mn and Cd were determined in soil samples. Also 36 plant samples from shoots of 18 main crops were collected in the region and the concentrations of heavy metals were determined in crop samples. Results showed that maximum DTPA-extractable concentrations of Ni and Mn were in the northeast of the region in the 0-5 cm layer (4.2 and 312 mg/kg.soil, respectively) and decreased in 5-10,10-20 and 20-40 cm layers (2.7,2.7,2.1 and 200,212,146 mg/kg.soil, respectively). The concentrations of Ni and Cd in shoots of crops were undetectable with atomic absorption method. The concentration of Mn in rice shoots was 716.6 mg/kg.dry.m. It was higher than USEPA standards (15-100 mg/kg.dry.m). .

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Paleosols include soils formed under climatic condition different from the present. Although such soils are widespread in central Iran region, adequate investigations of them are yet to be carried out. Micromorphology is one of the most important tools in plaeoclimatological studies. This investigation was carried out to study microscopic features of two paleosols from Isfahan province to reconstruct the paleoclimatic condition during the Quaternary. The results of this study indicate that strong clay coatings are presented in Sepahanshahr paleosol, indicating moisture regime in the past. This paleosol is polygenetic due to calcite and gypsum accumulation during drier periods compared to clay illuviation condition. Micromorphological features in Segzi paleosol indicate that this area has experienced a swampy environment during the younger Dryas. The overall results from this study indicate that climatic oscillation evidences during Quaternary have been preserved in paleosols from Isfahan region.

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Stabilizng sand dunes has been one of the main challenges in the arid regions. So far, different kinds of mulches have been used extensively for sand dune stabilization. This study was carried out to determine the optimum composition, concentration and thickness of clay mulch for sand dune stabilization. For this purpose two soil samples from clay flats of a playa with different amount of salinity from Ardestan area were used to make clay mulches. A sand dune sample was selected as bed for applying the mulch. To select the right ingredient and treatments, clay samples were mixed with sand and different amount of water, and sprayed on sand dune bed. In addition, wheat straw was added to some mixture to test its effect on stability of the mulch. Treatments with lowest crack and highest penetration of mulch in sand bed were selected for the experiment in this study. Mulch treatments contained (1): 250g sand dune + 250g clay + 25g straw (2) 250g clay + 25g straw (3) 250g sand + 250g clay (4) 250g clay (5) 125g sand + 125g clay and (6) 125g clay. All treatments were mixed with 500ml water. The experimental design was a CRD with a 6(mulch) * 2(thickness)* 2 EC factorial method with 3 replications. The results showed that clay mulch were resistant to wind erosion, but erosion took place when they had been bombarded with sandblast. The mulches with straw showed the highest resistance to erosion as compared to other treatments. With increasing the number of mulch layers, resistant to erosion also increased. The added stability of mulch was due to the increase in mulch thickness and also increases in clay and silt content. The overall result of this study shows that the mulch with two layers and higher mixture of clay and sands was the best treatment for the stabilization of sand dunes.

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In Iran, the development of cultivated areas becomes gradually impossible due to ever-increasing population growth and urban area development. Therefore, it is very important to use the existing cultivated lands more efficiently. Land suitability evaluation makes the sustainable use of the lands feasible. The objective of this study was qualitative, quantitative and economic assessment of land suitability in Talandahst area for rainfed wheat, barley and chickpea. Talandasht plain with a surface area of 4500 ha is located southwest of Kermanshah city. The climate is semi-arid with cold winter and moderate summer. The successive stages of this research included soil survey in the field, soil analysis, qualitative and quantitative and economic evaluations of land suitability. In qualitative evaluation of land, climatic, topographic and soil suitability classes were determined according to the degree of the matching. Limitation and parametric methods were used in qualitative evaluation. Quantitative and economic evaluations made based on the observed yield and gross benefit, respectively. Based on qualitative evaluation, the studied area is marginally suitable for rainfed farming of wheat, barley and chickpea. This is due to water deficiency occurring during some stages of the growing cycle. The solution for this problem is supplementary irrigation. In addition to climate limitation, there are also topographic and soil restriction for the growth of the studied crops. On the basis of observed yield, the land units are moderately to highly suitable for rainfed wheat and barley production. Among the three named crops, the most and least profitable ones are chickpea and barley, respectively, and wheat ranks between them.

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Improper use of natural resources, especially soil, causes its degradation and severe soil erosion. Water erosion is an important factor causing soil degradation. Land use change of pasture would result in severe soil erosion mainly due to the reduction of vegetation cover and also surface soil disturbance. The objectives of this study were to estimate the amount of sediment, runoff and nutrient loss in four different land uses including a pasture with good vegetation cover (> 20%), a pasture with poor vegetation cover (< 10%), a currently being used dryland farm and a degraded dryland farm which is not used. Soil samples were taken from the depth of 0–10 cm in a completely randomized design with four replications. A rainfall simulator was run for two hours to estimate the amount of sediment, runoff and nutrient loss. Organic matter, total N, available P and distribution of particles size in soil and sediment were measured. The results showed that a very high degradation has occurred in the area mostly due to water erosion created as a result of overgrazing in pasture, susceptibility of geological formations and more importantly, the change of land use pasture to inefficient dryland farming. Maximum and minimum runoff was observed in the abandoned dry landfarm and pasture with good vegetation cover, respectively. Maximum sediment content was observed in dryland farm. Sediment content in dryland farm, abandoned dry landfarm and pasture with poor vegetation cover were 54.5, 21 and 10.4 times more than that in the pasture with good vegetation cover, respectively. Enrichment ratio (ER) of soil particles in sediment was highest for fine silt (2-5µm), followed by clay. A minimum of ER was obtained for sand fraction. Percentages of organic matter, total N and available P in sediment were higher in the first hour as compared to the second one. This is mainly due to the fact that fine particles are removed at the beginnings of the rainfall event. Total removal of these chemical factors was highest in dryland, intermediate in pasture with poor vegetation cover and abandoned dryland and lowest in pasture with good vegetation cover. In general, cultivation and disturbance of the pasture in the area land have caused a great decrease in soil quality and made the surface very sensitive to erosion.

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To investigate the degree of forest degradation and the effect of land use change on selected soil quality attributes in loess-derived landforms, samples were taken from different land uses including forest, rangeland, degradated rangeland and farmland in Pasang watershed located in the Galikesh area of Golestan province (37°16'N, 55°30'E). The annual average temperature and mean precipitation of study area were 15°C and 730 mm respectively. Organic matter, pH, EC, CaCO₃ and nutrients (N, P, K) as chemical indicators, hydraulic conductivity, bulk density and porosity as physical indicators and soil respiration as biological indicator were measured. The results showed that the amount of organic matter decreased three percent when it was turned from forest to farmland, and increased two percent from farmland to rangeland. The amount of CaCO₃ in surface layer of deforested area was more than in the forest soils. The amount of soil N in forest and soil P and K in rangeland were higher than in other land uses. Bulk density and porosity in forest and MWD in rangeland were higher than in other land uses because of the decrease in organic matter due to farming activities. Soil respiration in forest was highest as compared to in other land uses. Difference of enzymes activities (L-asparaginase and Dehydrogenase) compared to microbial respiration indicates that enzymes activity is related to specific biological processes while soil microbial respiration basically depends on the general activity of soil microbial population. It could be concluded that amount of organic matter, soil N, bulk density, porosity, MWD, soil respiration and enzymes activities are suitable indicators for soil quality evaluation in this area.

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Geologic and pedologic controls are the main factors determining the distribution of elements in natural soil environments. In order to assess the role of these factors in the content and distribution of major elements of soil, six parent materials including phyllite (Ph), tonalite (To), periditite (Pe), dolerite (Do), shale (Sh) and limestone (Li) were selected in Fuman-Masule region. Soil genesis and development of representive residual pedons were studied for each parent material. Total content of Si, Al, Ca, Mg, Fe, Mn, K, Na, Ti and P of soil horizons were measured and compared to the geochemical and mineralogical composition of parent materials. Maximum concentrations of Fe2O3 and MgO were found in the soils derived from Pe and Do however, these soils had low content of SiO2 and Al2O3, which is in conformity with the geochemical composition of the parent rocks. On the contrary, FeCBD content of these soils was lowest, indicating the low degree of soil development and, by the same fact, the importance of inheritance factor in soil Fe concentration. However, comparison of total Fe and FeCBD in Li1, Sh2 and To2 revealed that relative development of these pedons is higher than the others. Silicon depletion in Ph1, To2 and Sh2 pedons, relative to parent rocks, is higher than in Pe and Do pedons. However, this element is enriched in Li pedons. MnO content of Pe and Do pedons is governed by geogenic factors, while in Sh pedons, pedogenic factors, especially redox conditions, play the major role. Exchangeable forms of Ca and Na are determined by soil properties rather than by parent material type. Notwithstanding the redistribution of all major elements throughout pedons due to soil forming processes, the importance of inheritance factor in soil Si, Al, Mg, Fe, K, and Ti is higher than pedogenic factors.

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Models are helpful tools to predict runoff, sediment and soil erosion in watershed conservation practices. The objectives of this research were to investigate sensitivity analysis, calibration and validation of EUROSEM model in estimation of runoff in Tangh-e-Ravagh sub-basin of Karoun watershed. The model was tested in a one hectare experimental test site. The area was divided into nine elements according to EUROSEM user's manual. A triangular weir was installed at the outlet of the area to collect runoff in specified time periods for six rainfall events. Sensitivity analysis of the model was performed by a ±10% change in the dynamic parameters of the model and examining the outputs for a rainstorm. Sensitivity analysis showed that total runoff was sensitive to saturated hydraulic conductivity and insensitive to soil cohesion. Sensitivity analysis indicated that the model sensitivity depends on evaluation conditions and it is site-specific in nature. Calibration and validation of the model was performed on input parameters. Calibration of hydrographs was performed by decreasing saturated hydraulic conductivity and capillary drive and increasing initial soil moisture. Validation results showed that EUROSEM model simulated well the total runoff and peak of runoff discharge, but it could not simulate well the time of runoff, time to peak discharge