Journal of Water and Soil
Year:2017 | Volume:30 | Issue:6 |Papers Count:35

Introduction: A total dissolved solid (TDS) is an important indicator for water quality assesment. Since the composition of mineral salts and discharge affects the TDS of water, it is important to understand the relationships of mineral salts composition with TDS.Materials and Methods: In this study, methods of artificial neural networks with five different training algorithm, Levenberg-Marquardt (LM), Scaled Conjugate Gradient (SCG), Fletcher Conjugate Gradient (CGF), One Step Secant (OSS) and Gradient descent with adaptive learning rate backpropagation (GDA) algorithm and adaptive Neurofuzzy inference system based on Subtractive Clustering were used to model water quality properties of Zarrineh River Basin, to be developed in total dissolved solids prediction. ANN and ANFIS program code were written in MATLAB language. Here, the ANN with one hidden layer was used and the hidden nodes' number was determined using trial and error. Different activation functions (logarithm sigmoid, tangent sigmoid and linear) were tried for the hidden and output nodes. Therefore, water quality data from seven hydrometer stations were used during the statistical period of 18years (1993-2010). In this research, the study period was divided into two periods of dry and wet flow, and then in a preliminary statistical analysis, the main parameters affecting the estimation of the TDS are determined and is used for modeling. 75% of data are used for remaining and 25% of the data are used for evaluation of the model, randomly. In this paper, three statistical evaluation criteria, correlation coefficient (R), the root mean square error (RMSE) and mean absolute error (MAE) were used to assess models' performances.

Introduction: Water crisis as a majorlimitation factor for agriculture, like other arid and semiarid regions exists in Isfahan province which is located in the central part of the Zayandehrud River Basin (ZRB). Rice appears to be the far-most profitable crop but at the same time it has a major impact on basin scale water resources, especially affecting downstream farmers. In the study area (ShahidFozveh Research Station), the water resources for agricultural production face heightened competition from other sectors like industry and domestic use. This necessitates considering different crops, altered agricultural systems and innovative methods that can reduce the water requirements for the irrigation of rice. The Alternative Wetting and Drying (AWD) seems to be an effective method reducing water use for rice crops and possibly save the water for downstream users. There have been no qualitative evaluations of rice production under deficit irrigation practices in Isfahan area. This study sought to determine, under study area conditions, the quantities of water irrigation used with AWD practices, the resulting water productivity (WP) and the effects of alternative irrigation management on yield, quality indices and rice production performance.

Introduction: Water for agriculture is one of the most important factors in arid and semi-arid areas and municipal wastewater treatment is an important resource for this purpose. Wastewaters even after treatment may contain many types of microorganisms that are pathogenic to humans and dangerous for the environment. Therefore, potential of transfer contaminations is a serious problem regarding use of treated wastewater for agriculture. Due to the risk of transfer contaminations through the use of wastewater, the study of transfer microbes in soil in recent decades has been of interest to researchers. Thereafter various irrigation techniques can be used associated with treated wastewater for agriculture. Accordingly, the present study was conducted on Fecal Coliform in the wastewater treatment in laboratory columns.Materials and Methods: The present study was conducted in Agriculture Faculty of TarbiatModares University for 62 days in 2013. This study was conducted on Fecal Coliform in the wastewater treatment in laboratory columns, having 30 cm diameter and 60 cm height. They were irrigated using surface drip irrigation system (DI). Samples of the effluent and soil solutions were collected from the experimental columns after each irrigation events. Soil texture was clay-loam that was collected from south of Tehran wastewater treatment plant. Three models of one site sorbtion's model, attachment/ detachment two kinetic site and attachment/ detachment one kinetic site, were used for simulation of Fecal Coliform transport by inverse solution option of the HYDRUS-ID model. For calibration of the model and estimating the model input parameters, soil hydraulic and transport parameters were inversely estimated. Results represented that the HYDRUS-1D with reasonably accurately simulated the outlet flow. To simulate the transfer of the bacteria in the soil, one site sorption model, two kinetic sites model (particle transport using attachment/detachment) and one kinetic site model were used.

Introduction: In recent years, due to the reduction in surface water, utilization of groundwater has been increased to meet the growing demand of irrigation water. The quality of these water resources is continually changing, due to the geological formations, the amount of utilization, and climatic parameters. In many developing countries, the irrigation water is obtained from poor quality groundwater resources, which in turn, creates unfavorable circumstances for plant growth and reduces the agricultural yield. Providing adequate water resources for agricultural utilization is one of the most important steps needed to achieve the developmental targets of sustainable agriculture. Thus, this necessitates the assessment and evaluation of the quality of irrigation water. There are many proposed methods to determine the suitability of water for different applications, such as Piper, Wilcox, and Schoeller diagrams. Zoning of quality and suitability of irrigation water could represent the prone and critical areas to groundwater exploitation. Garmsar alluvial fan is one of the most sensitive areas in the country where traditional agriculture practices had turned into modern techniques and excessive exploitation of groundwater has caused an intensepressure on aquifers and increased water salinity. The aim of this study is to evaluate the suitability of groundwater for irrigation in a 10-year period (2002-2012) and its changes in this basin.

Introduction: Iran is a vast country with limited water resources. Iran is located in arid areas and average precipitation is estimated to be 250 mm. In recent years, water shortage has created many problems for Iranian farmers. In these conditions, surface and ground water use is excessive. High consumption, low irrigation efficiency, bad time and geographical distribution of precipitation, population growth and increasing agricultural land are one of the main reasons for the irrigation water crisis. Therefore, the main problem of drought and water shortages still remains. The area of agricultural land in Golestan province is high, but most of them are rain-fed cultivation or left fallow. Due to the loss of irrigation water in traditional agriculture, development of pressurized irrigation as a solution to increase productivity and reduction of strain on water resources was raised. With government support, the use of pressurized irrigation systems is increasing.

Introduction: Snowmelt runoff plays an important role in providing water and agricultural resources, especially in mountainous areas. There are different methods to simulate the process of snowmelt. Inter alia, degree-day model, based on temperature-index is more cited. Snowmelt Runoff Model is a conceptual hydrological model to simulate and predict the daily flow of rivers in the mountainous basins on the basis of comparing the accuracy of AVHRR and TM satellite images to determine snow cover in Karun Basin. Additionally, overestimation of snow-covered area decreased with increasing spatial resolution of satellite data. Studies conducted in the Zayandehrood watershed dam, showed that in the calculation of the snow map cover, changes from MODIS satellite imagery, at the time that the image does not exist, using the digital elevation model and regression analysis can provide to estimate the appropriate data from satellites. In the study of snow cover in eastern Turkey, in the mountainous regions of the Euphrates River, data from five meteorological stations and MODIS images were used with a resolution of 500 m. The results showed that satellite images have a good accuracy in estimating snow cover. In a Watershed in northern Pakistan in the period from 2000 to 2006, SRM model was used to estimate the snow cover using MODIS images. The purpose of this study was to evaluate the snowmelt runoff using remote sensing data and SRM model for flow simulation, based on statistical parameters in the Kardeh dam basin.

Introduction: Due to sensitiveness of flow to roughness coefficient (RC), selection of this coefficient is important in earth canals designing purposes. Precision selection of this coefficient is necessary for design and operation of earthen canals purposes. Overestimation of the actual amount of this coefficient will cause an underestimation for flow velocity. Accordingly, sedimentation in the earth canals will reduce canals' capacitances. Adversely, underestimation of this coefficient will cause an overestimation for flow velocity and water flux in the earth canals. It will also increase the risk of soil erosion in the channels. This coefficient is expressed by Manning, Chezy and Darcy Weisbach equations. While, hydraulic engineers have selected Manning equation to estimate the flow rate in open channels due to ease of use and acceptable precision in the application of this equation. Water for crop production in Moghan, as one of the most important agricultural centers in Iran, is supplied from Moghan-Meel diversion dam via main canal of irrigation and drainage network with a capacity of 80 m3 s-1 with a length of 116 km. All of the branched 63-channel from the main channel are earthen. Continual sedimentation in the earth canals reduced the capacity of them and re-estimation the capacity of this canals needs to the precise quantities of variables such as roughness coefficient. Because the overestimation of the actual value of the coefficient would reduce the canals’ capacity and underestimation of the coefficient increase the risk of erosion in earth canals. The analysis of the correlation among variables, regression, analysis of statistical distribution of variables, analysis of variance of variables and the analysis of the events probabilities for stochastic variables can be made by statistical methods. Therefore, these methods were applied to analysis of roughness coefficient in the earth canals. Also, due to the importance of roughness coefficient and significant sensitivity of the capacity to this coefficient, the current study was conducted to statistically analyze and to evaluate roughness coefficients in non-vegetated canals for irrigation and drainage network of Moghan (in North-west of Iran). The results of the research may be applied in the design, evaluation and utilization of networks, especially in the irrigation and drainage network of Moghan.

Introduction: With increasing of population and the valuable water resource pollutions, a demand has been felt for new and inexpensive methods in order to remediation and improving of water quality. Cadmium is a trace element. In low concentration, this heavy metal is harmful to life, and considered as a dangerous pollutant. Cadmium leads to pollution and reduction of water quality; sometimes even toxicity through contaminated sources such as wastewater (Agricultural, municipal and industrial). Phytoremediation with aquatic macrophytes is an effective and inexpensive method for improving water quality and wastewater. The aim of this study was to investigate the cadmium phytoremediation by Ceratophyllumdemersum L. as a potential method for remediation of cadmium pollution in aquatic medium.Materials and Methods: In this study, the remediation of cadmium pollution in aquatic medium monitored, within 14 days cultivation of coontail (Ceratophyllumdemersum L.). At first, for estimating the level of local wastewater cadmium pollutions, five-month cadmium concentration measurement of steel industrial wastewater and urban wastewater set. Then, plants collected from the irrigation channels of Shahid Chamran University of Ahvaz. After finding the best pH of nutrient solution for Ceratophyllumdemersum L. growth by cultivating the plants in 2 liters pots filled by the solutions with three different pH (5.5, 7 and 9.5) within three weeks; 12 grams of plants cultivated in 2 liters of Hoagland nutrient solution contaminated by cadmium (pH=7). The initial contamination levels were set as five different concentrations of cadmium (0, 1, 2, 4, and 6 mg l-1) with three replications. The cadmium concentrations of the pots were measured every day and on the last day of cultivation, plants wet weight, plants dry weight and Cd concentration in plants were measured. Then, biomass production, Cd bioconcentration factor (BCF), Cd uptake index, and Cd uptake percentage of plants were calculated. Standard deviations calculation and correlation and regression analysis were performed using Microsoft Office Excel2007 and SPSS 16. One-way ANOVA performed to identify significant differences in metal concentrations in the different treatments. Differences considered significant at p<0.05.

Introduction: In spite of improving the water productivity due to development in water infrastructure systems, population increasing causing the water withdrawal is triple in the last fifty years. In this situation competition on water consumption especially in the agricultural sector which is the biggest consumer in the world and also in Iran is a severe problem. Water allocation has been assessed widely in the recent past. Additionally, several studies have explored methods to incorporate conflict resolution methods in water allocation. In a general classification, there are two types of methods. One is the method based on game theory, graph theory and general models based oncooperative game into a category that has the ability to consider the stakeholder preferences and assess the several scenarios under specified policy. Although this type of methods iseligible to cooperate the stakeholder in modeling but due to their weakness on considering the information on details and their limitations in adoption with changes caused from uncertainty, they are not popular in practical cases. Another type of conflict resolution method which is eligible to considering more detailed information of systems has the optimization approach basically, has the most interests between researchers. There is namely the Nash bargaining solution, the Kalai-Smorodinesky solution, the Equal loss solution and the area monotonic solution. There are several studies which areapplied these methods to investigate about groundwater (5, 6 and10). There are a few applications of water resource allocation models which is incorporated with conflict resolution methods in Transboundary Rivers nowadays and restricted to game theory related methods (1 and 2). The aim of this study is the assessment of the application of conflict resolution methods such as symmetric and non symmetric Nash solution, non symmetric Kalai-Smorodinesky, non symmetric equal loss solution and finally the area monotonic solution in water allocation between beneficiary's provinces in Atrak basin. The performances of these methods are compared with each other and also with the common water allocation model.

Introduction: In the present study, dealing with water deficit challenges for Gorgan River Basin has been considered. Golestan province's economy is dependent on agriculture but the occurrence of drought periods reduced the agricultural production and consequently the region's economy is in crisis. Therefore, performing studies for programming and management of the water resources of the province and the water allocation in the margin of Voshmgir dam in Gorganrood basin has a great deal of importance. The issue of the allocation of water resources is proposed in order to maximize the expected profit of the water system. According to the regional water organization policy, one of the main goals of Voshmgir dam water management is the allocation of water between the competing consumers. If the amount of promised water is released in the future, the expected net profit of the system will be realized and if it is not released, the system will experience losses.

Introduction: Better use of water and soil resources in paddy fields, increase in rice production and farmer's income, installation of subsurface drainage system is necessary. The main goalof these systems, are aeration conditions improvement prevention of water logging, yield increase, land use increase and multiuse of the land. In different countries, installation of subsurface drainage cause yield increase and working condition on the land, but no research has been conducted in different depths and spacing. On the other hand, spacing and depth are the most important parameters in the installation of drainage systems, have a direct effect on incoming water into the drains. The aim of this research, is an investigation of the effect of subsurface drainage with different depths and spacing on discharge rate variation and water table fall, in order to analyze the improvement of water flow movement in the soil. Also, study the effect of different drainage systems on the increase of the canola yield as the second cultivation in these treatments have been compared.Materials and Methods: To measure hydraulic conductivity in different depths, the auger holes have been dug (excavated). The saturated hydraulic conductivity in these holes was determined using Ernst method (1950) before installation of drainage systems. In the drainage pilot plot of Sari Agricultural Sciences and Natural Resources University three subsurface drainage systems with mineral envelope have been installed. 1- The first one with the 0.9 m depth and 30 m spacing (D90 L30), 2- The second one with 0.65 m depth and 15 m spacing (D0.65 L15) and 3- The third one with 0.65 m depth and spacing (D0.65 L30) and one bi-level system with mineral envelope including four drains of 15 m spacing with 0.9 m and 0.65 m depths were installed alternatively. After auger hole equipment installations, in the middle spacing of two subsurface and water table reading possible, the water table fluctuation and drain outlet discharge rate from farm drains during canola growing season were measured on a daily basis. Also, canola yield during 4 years after drainage systems were monitored.

Introduction: Bridges are certainly one of the most important structures but costly service elements in a transport system. The bridges are very required to access the damaged areas in emergency situations such as floods and earthquakes. Scour around the foundations of bridge piers exposed to the flowing water than can destroy the bridge itself is a subject of major concern. Flow pattern is known as responsible for all changes in stream bed. Any obstacle in the channel can form new flow patterns causing additional shear stress exerted on the bed than the equilibrium condition of the absence of the obstacle. Appropriate shaping of flow pattern and proper selecting of pier geometry and the location of bridge piers can be one of the proper methods in reduction of scour amount which is the main subject of the present study.Materials and Methods: Inclined bridge group pier is a type of bridges with modern geometry based on development in building technology of structures. Many of these bridges have been built all around the world and the 8th bridge built crossing the Karun River in Ahvaz is a sample of the Iranian ones considered in this research. Hydrodynamic behavior of flow is investigated around the inclined bridge group pier settled on foundation using the FLOW-3D numerical model. Inclined bridge group pier investigated in this study, includes two rectangular piers which are 2.5 cm long and 3.5 cm wide and set in an angle of 28 degree on rectangular foundation which is 16 cm long and 10 cm wide and installed in three different foundation levels namely at, above and below the bed levels. The physical model of prototype pier considered in this study was constructed to the scale of 1: 190 of the Ahvaz 8th bridge. In order to verify the accuracy of the numerical model, velocity data obtained from image processing technique were used.

Introduction: River discharge as one of the most important hydrology factors has avital role in physical, ecological, social and economic processes. So, accurate and reliable prediction and estimation of river discharge have been widely considered by many researchers in different fields such as surface water management, design of hydraulic structures, flood control and ecological studies in spetialand temporal scale. Therefore, in last decades different techniques for short-term and long-term estimation of hourly, daily, monthly and annual discharge have been developed for many years. However, short-term estimation models are less sophisticated and more accurate. Various global and local algorithms have been widely used to estimate hydrologic variables. The current study effort to use Lazy Learning approach to evaluate the adequacy of input data in order to follow the variation of discharge and also simulate next-day discharge in Talar River in Kasilian Basinwhere is located in north of Iran with an area of 66.75 km2. Lazy learning is a local linear modelling approach in which generalization beyond the training data is delayed until a query is made to the system, as opposed to in eager learning, where the system tries to generalize the training data before receiving queries.

Introduction: During the last five decades there has been a sharp increase in water consumption owing to the population explosion, unprecedented rise in standard of living, and enormous economic development. Limitation of water resources in Iran motivates sustaining and preserving of these resources in order to supply future water needs. Fulfilling these objectives will not be possible unless accurate water balance of watersheds. An assessment of the available water resources is a pre-requisite to undertake an analysis of the stress on the water resources and to subsequently adopt appropriate management strategies to avoid adverse environmental effects and reconcile conflicts between users. Water balance models have been developed at various time scales (e.g. hourly, daily, monthly and yearly) and various spatial resolutions to varying degrees of complexity. Monthly water balance models were first developed in the 1940s by Thornthwaite (1948) and later revised by Thornthwaite and Mather (1955, 1957). These models have since been adopted, modified, and applied to wide spectrumof hydrological problems. Using GIS and computer models are useful tools for water balance calculating and results analyze. A spatial hydrology model is one which simulates the water flow and transport in a specified region of the earth using GIS data structures. The purpose of this study was to develop a computer model for rapid calculation of the water balance which is based on distributed meteorological data, and estimate uncertain factors of water balance on the basis of physical data. Try to minimize the complexity of the assumptions and also it is suitable for Basin water balance evaluation. Daily evapotranspiration and precipitation data were used to calculate daily changes of soil moisture balance, but the result is presented annually.

Introduction: Soil Hydraulic conductivity is considered as one of the most important hydraulic properties in water and solution movement in porous media. In recent years, various models as pedo-transfer functions, fractal models and scaling technique are used to estimate the soil saturated hydraulic conductivity (Ks). Fractal models with two subset of two (solid and pore) and three phases (solid, pore and soil fractal) (PSF) are used to estimate the fractal dimension of soil particles. The PSF represents a generalization of the solid and pore mass fractal models. The PSF characterizes both the solid and pore phases of the porous material. It also exhibits self-similarity to some degree, in the sense that where local structure seems to be similar to the whole structure. PSF models can estimate interface fractal dimension using soil pore size distribution data (PSD) and soil moisture retention curve (SWRC). The main objective of this study was to evaluate different fractal models to estimate the Ks parameter.Materials and Methods: The Schaapetal data was used in this study. The complex consists of sixty soil samples. Soil texture, soil bulk density, soil saturated hydraulic conductivity and soil particle size distribution curve were measured by hydrometer method, undistributed soil sample, constant head method and wet sieve method, respectively for all soil samples. Soil water retention curve were determined by using pressure plates apparatus. The Ks parameter could be estimated by Ralws model as a function of fractal dimension by seven fractal models. Fractal models included Fuentes at al. (1996), Hunt and Gee (2002), Bird et al. (2000), Huang and Zhang (2005), Tyler and Wheatcraft (1990), Kutlu et al. (2008), Sepaskhah and Tafteh (2013). Therefore The Ks parameter can be estimated as a function of the DS (fractal dimension) by seven fractal models (Table 2). Sensitivity analysis of Rawls model was assessed by making changes (±10%, ±20% and±30%) in input parameters (porosity, fractal dimension and the intake air suction head).Some indices like RMSE, AIC and R2 were used to evaluate different fractal models.

Introduction: Pollution of soil and water environment by release of heavy metals is of great concerns of the last decades. Sorption of heavy metals by low cost materials is considered as an inexpensive and efficient method used for removal of heavy metals from soil-water systems. The presence of different ligands with various complexing abilities can change the sorption properties of heavy metals and their fate in the environment as well. In order to assess the effect of citrate and arginine as natural organic ligands in soil environment, in a batch study we investigated the effects of these ligands on equilibrium sorption of nickel to sepiolite and calcite minerals and also kinetics of Ni sorption by these minerals.Materials and Methods: Minerals used in this study included sepiolite from Yazd (Iran) and pure calcite (Analytical grade, Merck, Germany). Sepiolite was purified, saturated with Ca using 0.5 M CaCl2, powdered in a mortar and sieved by non-metal 230 mesh standard wire sieve. For equilibrium sorption study, in a 50-mL polyethylene centrifuge tube, 0.3 g sample of each mineral was suspended in 30 mL of a 0.01 M CaCl2 solution containing 0, 5, 10, 20, 40, 60, 80 and 100 mg L-1 Ni (NiCl2) and containing zero (as control) or 0.1 mmol L-1 citrate or arginine ligands.

Introduction: Biofertilizers have been identified as alternative to chemical fertilizers to increase soil fertility and crop production in sustainable farming systems. One of the most useful kind of biofertilizers include plant growth promoting rhizobacteria (PGPR). Azospirillum is an associative rhizobacteria which can be very useful for plants such as wheat. It can help plant by fixing nitrogen through biological way, causing root development, plant strength improvement in primary phases, causing germination percent increment, improving plant tolerance in stress situations (drought, salinity, soil compaction and pathogens), secreting plant promoting hormones like cytokinin, Oxin and finally yield increment will be observable. Modern agriculture largely relies on the extensive application of agrochemicals, including inorganic fertilizers and pesticides. Although pesticides are important, their effects on nontarget organisms are of great concern because this poses a risk to the entire ecological system. The fungicides may also adversely affect the soil microflora, especially the types of microorganisms that can applied to seeds as bacterial inoculants. Considering useful effects of plant growth promoting rhizobacteria especially Azospirillum on Wheat, this study was done in order to survey interaction effects between fungicide and available biofertilizers in Iran market.

Introduction: Boron (B) is an essential plant micronutrient whose soil availability is influenced by many soil factors. Understanding the processes controling activity of boron (B) in the soil solution is important for soil fertility management. The reaction of adsorption and desorption of boron in soil determines the amount of boron that is available to plants. Adsorption- desorption processes play a major role on boron equilibrium concentration and therefore on its bio-availability. Ionic strength, pH and ionic composition in exchangeable phase are among the major factors affecting B adsorption reactions. Reduced adsorption of boron at high pH is because of a surface potential decrease on minerals with pH-dependent charge.Ionic strength has also a considerable effect on B adsorption. Several studies have been performed in the adsorption of boron and the effect of factors such as ionic strength and cations has been understudied, however, the effect of sodium adsorption ratio and its interaction with the ionic strength on boron adsorption behavior has not been reported. In this study, the adsorption isotherms of boron in the soils affected by the combined effects of ionic strength and sodium adsorption ratio were investigated.Materials and Methods: In order to assess the effects of ionic strength (IS) and Sodium Adsorption Ratio (SAR) on availability of B, the adsorption of B was investigated in a calcareous soil that had low levels of electrical conductivity, sodium adsorption ratio and available P. For this purpose, 5 g soil was equilibrated with 20 mL of B solution (0, 2, 5, 8, 10, 15, 20 mg L-1) in 0.02, 0.06 and 0.12 M background solutions (prepared by NaC1, CaC12.2H2O, MgCl2.6H2O), at two SAR levels (20 and 100).The reaction temperature was 25°C. The suspension was centrifuged, filtered, and a sample was removed and B was determined by Azomethine-H spectrophotometric method (at a wavelength of 420 nm). B adsorption in Soil was obtained by subtracting B in solution after filtration, from added boron.

Introduction: Soil organic matter is influenced strongly by vegetation cover and management, therefore it is proposed as the main indicator of soil quality and health. The changes in soil organic matter status occur much more rapidly in the labile pools than in organic C. Thus, labile pools can be used as early indicators of changes in total organic matter that will become more obvious in the longer term here. In addition, the labile fraction has a disproportionately large effect on nutrient-supplying capacity and structural stability of soils. Land management as well as soil and environmental conditions lead to the deployment of different plant communities in rangeland ecosystems, which in turn may have different effects on soil quality indicators. The main objective of this research was to investigate the influence of different vegetation covers on the quantity and quality of soil organic carbon fractions in Gonbad experimental watershed, Hamadan. Moreover, the seasonal changes of selected soil carbon fractions were investigated.Materials and Methods: Paired Gonbad watershed in Hamedan consists of two sub-basins: in control sub-basin no grazing management is applied, while in protected sub-basin, grazing has been restricted to a very short period in late autumn since 2002. Average annual precipitation and average annual temperature in the area are 304.4 mm and 9.5 °C, respectively (5). The soil cover of the watershed consists of TypicCalcixerepts, TypicHaploxerepts and Lithic Xerorthents (9).

Introduction: Soil erosion by water is one of the most important processes of land degradation, especially in semi-arid areas. Among different types of the soil erosion, gully erosion accounts as one of the most critical processes which can cause soil destruction, changes in landscape and water resources filling of reservoir of dams, decrease in water transport capacity of rivers and agricultural lands destruction in the lowland areas. Based on the Posen definition, gully is a river with high slope walls and an erosive high slope and active head which occurs by erosion resulted from the surface flow (usually during or after high density rainfalls). Different factors play role in occurrence and development of gullies and sediment production resulted of this kind of erosion which includes slope, amount and distribution of rainfall intensity, construction operations, vegetable cover destruction, land-use change, unsuitable utilization, and susceptibility of bed materials to the erosion and flood. Considering the importance of gully erosion and the way of its occurrence and development and its control, more comprehensive studies are needed to be done. Although, some studies have done in this subject that some of them are depicted below:Rinkez et al showed that gully erosion is further occurred in soils with high exchangeable sodium percentage and sodium absorption ratio and they depicted that these two factors are important indices for soil diffusion amount in gullies. Buma and imson investigated factors such as electricity conductivity, calcium carbonate percentage, and the type of clay mineral in white, brown, and gray samples of marl in the Peter area, Spain. According to their results, factors such as electrical conductivity and sodium absorption ratio had high correlation with erosivity of the Bad Lands.

Introduction: Minerals are one of the main components of soils which play different roles in the soils.Minerals make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases plant nutrients which are retained by other minerals through adsorption, cation exchange, and precipitation. Minerals are indicators of the amount of weathering that has taken place, and the presence or absence of particular minerals gives clues to how soils have been formed. The physical and chemical characteristics of soil minerals are important consideration in planning, constructing, and maintaining of buildings, roads, and airports. Clay minerals can be used for understanding of soil formation, optimum management of dry and wet lands and interpretation of paleo environments. Moreover, clay minerals can provide some valuable information such as the origin of sediments, transportation and precipitation of sediments and also some information about intercontinental weathering regimes. Quaternary sediments have occupied most of the agricultural and natural resources of Urima plain and recognition of mineralogical of these soils is essential to optimum and stabile use of these soils. Additionally, caly mineralogical investigation can provide some information about the intensity of weathering processes and climate change in this area. Thus, in this study clay minerals of quaternary sediments in northeast of Urmia and the mechanisms of their formation and also tracing probable climate change in this area were investigated.

Introduction: Application of organic fertilizers in agricultural soils with low organic matter content is one of the best ways of nutrients addition to these soils. Different organic fertilizers have different effects on nutrient availability in soil. Moreover study of the distribution of nutrients in the soil allows investigating their mobility and bioavailability. The nutrients availability and kinetics of nutrients desorption into the soil solution is often closely related to the distribution of nutrients to different fractions in the soil. It has been assumed that the factors influencing metal fractionation and availability in soil include rate of amendment application, amount of nutrients in amendment, root-induced pH changes, metal binding by root exudates, root-induced changes of microbial activities, and metal depletion because of plant uptake.Materials and Methods: In this study, availability and fractionation of Zinc (Zn) and Copper (Cu) were compared in one calcareous soil amended with 0, 0.5, and 1% (w/w) of cow manure and vermicompost in a completely randomized design. Also, wheat was planted in treated and untreated soils in greenhouse condition. Available Zn and Cu were determined using different methods (DTPA-TEA, AB-DTPA, and Mehlich 3). For Zn and Cu fractionation, the soil samples were sequentially extracted using an operationally defined sequential fractionation procedure, based on that employed by Tessier et al. (1979) in which increasingly strong extractants were used to release Zn and Cu associated with different soil fractions.

Introduction Soil infiltration rate is the major soil hydraulic property which can be affected by the soil physical characteristics and management practices. The use of land can affect various soil properties such as physical and hydraulic properties. Differences of the hydraulic soil characteristics such as infiltration rate in various land uses can affect their potential to runoff production as well as soil loss in the catchment. The knowledge of the physical and hydraulic characteristics of various land uses can help to better management of soil and water in the catchment. It is very essential in the semi-arid catchments where vegetation cover is generally poor, the soils are often instable against erosive factors especially when the rainfalls are consecutive and intensive. Therefore, this study was conducted to investigate the soil physical and hydraulic characteristics in the TahamChai catchment, in a semi-arid region, NW Zanjan. Various land uses consist of pastures, rainfed and irrigated lands can be observed in the catchment, which cover about 62%, 33%, and 5% of the catchment area, respectively. The pastures have been covered with poor vegetation and are intensively exhausted by overgrazing. Rainfed lands are mostly under winter wheat cultivation. Soil erosion and sedimentation were the major environmental problem in this catchment.Materials and Methods The maps of land use and slope gradient were provided for study area. A total of 20 sites were selected based on the surface area of each land use in the catchment located between 34° 46’-36° 53¢N latitudes and 48° 17’-48° 37’ E longitudes. The study area consisted of ten sites in the pasture, seven sites in the rainfed and three sites in the irrigated lands. The geographical positions of study sites were determined by a global positing system (GPS).

Introduction: Application of EDTA may increase the heavy metal availability and phytoextraction efficiency in contaminated soils. In spite of that, it might also have some adverse effects on soil biological properties. Metals as freeions are considered to be severely toxic, whereas the complexed form of these metalswith organic compounds or Fe/Mn oxides may be less available to soil microbes. However, apart from this fact, some of these compounds like EDTA and EDTA-metal complexes have low bio- chemo- and photodegradablity and high solubility in their own characteristics andable to cause toxicity in soil environment. So more attentions have been paid to use of low molecular weight organic acids (LMWOAs) such as Citric acid because of having less unfavorable effects to the environment. Citric acid increases heavy metals solubility in soils and it also improves soil microbial activity indirectly. Soil enzymes activity is a good indicator of soil quality, and it is more suitable for monitoring the soil quality compared to physical or chemical indicators. The aims of this research were to evaluate the changes of dehydrogenase, urease and alkaline phosphomonoesterase activities, substrate-induced respiration (SIR) and Pb availability after EDTA and citric acid addition into a contaminated soil with PbCl2.Materials and Methods: An experiment was conducted in a completely randomized design with factorial arrangement and three replications in greenhouse condition. The soil samples collected from surface horizon (0-20 cm) of the Typic haplocalsids, located in Mashhad, Iran. Soil samples were artificially contaminated with PbCl2 (500 mg Pb per kg of soil) and incubated for one months in 70 % of water holding capacity at room temperature. The experimental treatments included control, 3 and 5 mmol EDTA (EDTA3 and EDTA5) and Citric acid (CA3 and CA5) per kg of soil. Soil enzymes activity, substrate-induced respiration and Pb availability of soil samples were determined by standard methods after 7, 14, 21 and 28 days of chelates addition.

Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. More than 60 playas have been identified in Iran. Considering the fact that playas and surrounding landforms are important archive of landscape evolution and paleoenvironmental variations, it seems that less attention has been paid to them so far. Soils are known as indicators of the landscapes evolution. Previous studies in arid regions of Iran imply different periods of deposition and soil formation in playa and alluvial fans or pediments. Bajestan playa is one of the known playa in northeastern Iran, and the largest clay flat exists in this playa. There is no information on the soils and their evolution in Bajestan playa. The objective of this study were to 1) identify the soils in different landforms along a transect from alluvial fan to clay in Bajestan playa 2) determine the morphological, micromorphological and mineralogical characteristics of these soils 3) determine the periods of soil and landform evolution and 4) comparison of soils evolution of the study area to other arid regions of Iran.

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 S = aAb, 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.

Introduction: Globally, Soil erosion is a principal degradation process resulting in negative impacts on different soil functions (food and other biomass production, water storing, filtering and transformation, habitat and gene pool, physical and cultural environment for mankind, and source of raw materials) which ultimately causes irreversible effect on the poorly renewable soil resource. Determination of the soil erodibility factor (K-factor) is a cumbersome and expensive undertaking in the effort to predict the soil loss rates. Soil erodibility (K-value) is a key parameter in erosion prediction and is important for conservation planning in the face of a rising need for protecting the limited land resources. The technique proposed by Wischmeier& Smith for estimating the soil erodibility factor is among the most important methods in this regard.Materials and Methods: Given the high amounts of silt and lime content in loess soils of eastern parts of Golestan province, the purpose of this study was to evaluate the ability of Wischmeier & Smith index to estimate the soil erodibility of this region. In this study, soil erodibility was obtained by Wischmeier's nomograph and then was compared with the actual values obtained by selecting three plots and then performing physical and chemical tests on these samples.

Introduction: Solar Net Radiation (Rn) is one of the most important component which influences soil heat flux, evapotranspiration rate and hydrological cycle. This parameter (Rn) is measured based on the difference between downward and upward shortwave (SW) and longwave (LW) irradiances reaching the Earth's surface. Field measurements of Rn are scarce, expensive and difficult due to the instrumental maintenance. As a result, in most research cases, Rn is estimated by the empirical, semi-empirical and physical radiation models. Almorox et al. (2008) suggested a net radiation model based on a linear regression model by using global solar radiation (Rs) and sunshine hours. Alados et al. (2003) evaluated the relation between Rn and Rs for Spain. They showed that the models based on shortwave radiation works perfect in estimating solar net radiation. In another work, Irmak et al. (2003) presented two empirical Rn models, which worked with the minimum numbers of weather parameters. They evaluated their models for humid, dry, inland and coastal regions of the United States. They concluded that both Rn models work better than FAO-56 Penman-Monteith model. Sabziparvar et al. (2016) estimated the daily Rn for four climate types in Iran. They examined various net radiation models namely: Wright, Basic Regression Model (BRM), Linacre, Berliand, Irmak, and Monteith. Their results highlighted that on regional averages, the linear BRM model has the superior performance in generating the most accurate daily ET0. They also showed that for 70% of the study sites, the linear Rn models can be reliable candidates instead of sophisticated nonlinear Rn models. Having considered the importance of Rn in determining crop water requirement, the aim of this study is to obtain the best performance Rn model for cold semi-arid climate of Hamedan.

Introduction: The Southern Oscillation is a large scale phenomenon that changes the Normal oscillating air pressure on both sides of the Pacific Ocean. It disrupted the normal conditions and the patterns of temperature and precipitation change in the nearby region and other regions of the world. This phenomenon is caused by changing the water slope in the Pacific Ocean between Peru (northwestern South America) and Northern Australia (about Indonesia and Malaysia). ENSO phenomenon is formed of Elnino (warm state) and La Niña (cold state). There is high pressure system in the East and low pressure system in the West Pacific Ocean in normal conditions (Walker cycle). The trade winds blow from East to West with high intensity. ENSO start when the trade winds and temperature and pressure balance on both sides of the Pacific Ocean change. High pressure will form in the west and low pressure will form in the East. As a result, west will have high and east will have low rainfall. Temperature will change at these two locations. Enso longs about 6 to 18 months. This research investigated the impact of ENSO on monthly precipitation and temperature of Mashhad. The results showed that temperature and rainfall have a good relation with ENSO. This relation occurs in 0-5 month lag.