Research Article
M. Mohammadi Aria; A. Lakzian; Gh. Haghnia; H. Besharati; A. Fotovat
Abstract
Abstract
A large number of studies have shown that direct application of rock phosphate dose do not have enough efficiency to release phosphorus compared to chemical fertilizers. The main purpose of this study was to increase the efficiency of direct application of rock phosphate. Incorporation of rock ...
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Abstract
A large number of studies have shown that direct application of rock phosphate dose do not have enough efficiency to release phosphorus compared to chemical fertilizers. The main purpose of this study was to increase the efficiency of direct application of rock phosphate. Incorporation of rock phosphate with sulfur, organic matter and inoculation with sulfur-oxidizing bacteria and phosphorous-solubilizing fungus, seems to be a suitable alternative for increasing the efficiency and applicability of rock phosphate. This experiment was carried out in laboratory condition, using completely randomized factorial design with 12 treatments and 3 replications. The treatments included sulfur at three rates, 0% (S0), 10% (S1), 20% (S2), vermicompost at two rates, 0% (V0), 15% (V15), and inoculation with Thiobacillus thiooxidanc, Aspergillus niger (BF) and without inoculation. Water soluble phosphorus and pH were measured during incubation time (15 and 60 days). The results of experiment showed that water soluble phosphorous increased over the time and the maximum level of water soluble P was observed using treatment of 20% sulfur, 15% vermicompost and inoculated with Thiobacillus and Aspergillus (BFS2V1). The amount of water soluble phosphorus in BFS20V15 was significantly higher than other treatments.
Keywords: Rock phosphate, Organic matters, Water soluble phosphorus
Research Article
R. Kassray; S. Saedi
Abstract
Abstract
To study the effects of sewage sludge on tomato seedling growth, a series of pot experiments, each pot containing 17 kg soil, were conducted in a randomized complete design with eight replications. Treatments used were: 5 levels of sewage sludge (5, 10, 20, 30 and 40 tons/ha) and two ...
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Abstract
To study the effects of sewage sludge on tomato seedling growth, a series of pot experiments, each pot containing 17 kg soil, were conducted in a randomized complete design with eight replications. Treatments used were: 5 levels of sewage sludge (5, 10, 20, 30 and 40 tons/ha) and two control treatments (T1, without sewage sludge and T2, sewage sludge + complete fertilizers). Analysis of variance for above ground fresh and dry weights showed that they were significantly higher than T2 (sludge + complete fertilizer) when 5 and 10 tons per hectare of sewage sludge were applied to the pot at %1 level of probability. Application of sewage sludge higher than 10 tons per hectare, due to its toxic effect, decreased fresh and dry weight of above ground plant parts drastically. For example, applying 30 tones sewage sludge decreased dry weight by 20 percent and fresh weight by 44 percent as compared with that of T2. Mean comparisons revealed that water content of tomato plants did not differ significantly in comparison with that of T2 when 10-20 tons of sewage were applied, but its difference was significant at 5 percent level of probability when 30 and 40 tons of sewage sludge were applied. Analysis of variance for dry, fresh and water content of fruit also showed that their differences with T2 were non-significant when 5 and 10 tons/ha sewage sludge were applied to the pots. However, applying sewage sludge beyond 10 tons per hectare reduced all these three attributes significantly. Applying 20, 30 and 40 t/ha of sewage sludge delayed growth and development and caused apparent necrosis in the leaf margins of young and mature plant within the first month, while the toxic effect of sludge on necrosis decreased at later growth stages. Higher availability of iron (Fe) at higher sludge application rates along with soluble cation and anion concentrations in soil solution, especially chlorine and probably other side effects caused by sludge application are the factors that may have toxic effects on plants.
Keywords: Petrochemical, Tomato, Sewage sludge
Research Article
A. Yari; A. Darzi; M. Shaghaghi; R. Yari
Abstract
Abstract
The temperature of water entering the soil or variation in soil temperature has a direct impact on soil hydraulic conductivity via the effect on water viscosity. In this research, the time variability of soil saturated hydraulic conductivity (Ks) was studied. The relation between soil temperature ...
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Abstract
The temperature of water entering the soil or variation in soil temperature has a direct impact on soil hydraulic conductivity via the effect on water viscosity. In this research, the time variability of soil saturated hydraulic conductivity (Ks) was studied. The relation between soil temperature and fluid viscosity with hydraulic conductivity were also studied. The necessary experiments were conducted on Aboureyhan campus research farm located in Pakdasht, 25 km southeast of Tehran. 18 holes were digged in a plot and saturated hydraulic conductivity of soils were measured in these holes using inverse hole method. Experiments were carried out 12 times from 16-Aug-2005 to 14-Jun-2006. Investigations showed that the lowest value of Ks was obtained in winter when the soil and air temperatures are at minimum and by increasing the soil and air temperatures, these values increased too. Statistical analysis of experiments indicated that soil or air temperatures can considerably affect the results. Using the average of measured Ks to design drainage systems showed that neglecting the time variability of Ks may result in over or underestimating of drain spacing by 18.9% and 23.3%, respectively. Using the average of Ks values which was obtained in soil temperature of 16-20 oC had least effect on drain spacing, so it can be used as an average Ks to design drain spacing.
Keywords: Saturated hydraulic conductivity, Time variability, Drainage systems
Research Article
S. Bagherifam; A. Lakziyan; S.J. Ahmadi; B. Salimi; F. Asghari zadeh
Abstract
Abstract
Uranium as a natural radioactive heavy metal widely disperses throughout the earth's crust. In many cases, the natural abundance has been re-distributed due to anthropogenic activities, resulting in radionuclide contamination in groundwater and surface soil. Uranium through the plant uptake ...
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Abstract
Uranium as a natural radioactive heavy metal widely disperses throughout the earth's crust. In many cases, the natural abundance has been re-distributed due to anthropogenic activities, resulting in radionuclide contamination in groundwater and surface soil. Uranium through the plant uptake can enter the chain. The degree of speciation of radio nuclides in soils in areas with differing levels of uranium is of great interest in order to further the knowledge of the processes that determine the mobility and distribution of these contaminants from the installation, and consequently the potential short and long term risks. In the present work, we used a sequential extraction procedure based on Tessier’s method to determine the fractionation of uranium in a calcareous soil. The effects of two levels of uranium, 585 and 3240 Bq/kg 238U on the uranium distribution in soil fractions at 30 and 90 days of incubation were studied. The results indicated that U primarily associated with the carbonate fraction (62%) and increased by increasing the uranium level in soils. A comparison of extraction results from different incubation times showed that the pattern of uranium association with different fractions changed during the time of incubation.
Keywords: Distribution of uranium, Sequential extraction, Calcareous soils
Research Article
H. Ansari; K. Davary; S.H. Sanaei-Nejad
Abstract
Abstract
Drought is a natural creeping event that starts due to lower moisture compared to normal condition. This phenomenon impacts all aspects of human activities. However there is neither any detailed definition nor a general and proper index for drought monitoring. In this study, fuzzy logic has ...
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Abstract
Drought is a natural creeping event that starts due to lower moisture compared to normal condition. This phenomenon impacts all aspects of human activities. However there is neither any detailed definition nor a general and proper index for drought monitoring. In this study, fuzzy logic has been applied to deal with inherent uncertainties of the real world data. We presented a fuzzy model to evaluate and analysis the drought. Using the Fuzzy logic for drought monitoring of Mashhad synoptic station showed its higher capability and efficiency compared to Boolean logic. We combined two membership functions related to SPI (Standardized precipitation index) and SEI (a presumable standardized index for evapotranspiration), to provide a new index (SEPI: Standardized Evapotrans-Precipitation Index). The results showed that fuzzy model which employed 81 rules with minimum of 2 and maximum of 4 rules is the most accurate approach. The new index (SEPI) not only covers all advantages of SPI, but also can be calculated using different time scales of available data. Moreover, it considers temperature effects on drought occurrence and severity too. Monitored drought using SPI and SEPI indices demonstrated high correlation (more than 90%) between these two indices across all time scales. Drought monitored by SEPI for Mashhad synoptic station, at 1 to 3 monthly scales showed high drought frequency but low duration. Increasing time scales resulted in low frequency but higher duration. Employing SEPI also showed that high intensity and frequency of drought occurred in years 2000 and 2001 across all time scales. The longest drought duration, by 3 years across all time scales, occurred between 1995 to 1998.
Keywords: Fuzzy logic, Drought index, Standardized Precipitation index (SPI), Standardized Evapotransprecipitation Index (SEPI).
Research Article
.A Sadat; Gh. Savaghebi; F. Rejali; M. Farahbakhsh; K. Khavazi; M. Shirmardi
Abstract
Abstract
The objective of this study was to assess the effects of few arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria on the growth and yield indices of two wheat varieties in a saline soil (EC=10/1 dSm-1). A factorial experiment with completely randomized design with four replications ...
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Abstract
The objective of this study was to assess the effects of few arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria on the growth and yield indices of two wheat varieties in a saline soil (EC=10/1 dSm-1). A factorial experiment with completely randomized design with four replications was conducted to investigate the effects of three levels of fungal inoculation (non inoculation , inoculation with Glomus etunicatum and with Glomus intradices) and four levels of bacterial inoculation (non inoculation, inoculation with P. fluorescens strains 4 , 9, 12) on two wheat varieties (Sistan and Chamran) as tolerant and semi-tolerant to salinity, respectively. Our results showed that the growth and yield indices of two varieties were significantly (P
Research Article
M. Khezriyan; M.R. Majdzadeh Tabatabaei; S.S. Mousavi
Abstract
Abstract
The concept of armouring is used to discuss the coarse surface layer in rivers. Selective erosion in an alluvial channel reach for which there is no upstream sediment supply can lead to formation of a layer coarser than the under laying material. This phenomenon inhibits sediment transport ...
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Abstract
The concept of armouring is used to discuss the coarse surface layer in rivers. Selective erosion in an alluvial channel reach for which there is no upstream sediment supply can lead to formation of a layer coarser than the under laying material. This phenomenon inhibits sediment transport from the reach.Numerical modeling of armouring river bed, provides an approach to simulation of this phenomenon, however, these models are complicated in application. In addition, discretisation errors, affect the solution. Herein this paper, an analytical-based model has been developed; it is a simple one layer, 1-D, model to analysis different parameters in development of an armour layer, to predict depth of erosion and bed gradation curve of an armour bed. Differential equations describing armouring process, have been solved analytically, for each time step. The time steps are selected small enough to solve the equations analytically, for uniform flow, by avoiding discretisation errors.Predicted results are then compared by experimental data and numerical model results. This has shown reasonable validation of the model.
Keywords: Analytical model, Sediment transport, Armouring, Depth of erosion, Grain sizes
Research Article
B. Abasi; K. Esmaili; J. Abrishami
Abstract
Abstract
Although many studies have been carried out about dam break, this phenomenon still is one of the most important issues in the field of hydraulic engineering due to its hazards to human societies. Predicting the critical conditions including coincidence of flooding and dam break indicates more ...
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Abstract
Although many studies have been carried out about dam break, this phenomenon still is one of the most important issues in the field of hydraulic engineering due to its hazards to human societies. Predicting the critical conditions including coincidence of flooding and dam break indicates more field studies requirement. In this research the mutual effects of coincidence of negative surge due to dam break and flash flood has been studied using under different stored water levels. In addition, the effects of bed slope, existence of reservoir sediment and different initial reservoir depth have also been studied. Due to unsteady condition of flow, the stereoscopy method was employed to measure the hydraulic parameters such as depth. Using two digital cameras, results showed that by increasing the initial depth in dam's reservoir and channel slope, the reservoir would evacuate faster. Furthermore, sediments in which act like step in the flow direction can cause an increase in speed of the positive surge toward downstream. In addition by increasing the maximum of flow rate and base time of hydrographs, water rise in downstream was monitored as well.
Keywords: Usteady flow, Dam break, Flash flood, Experimental simulation
Research Article
B. Salavati; H.R. Sadeghi; A.R. Telvari
Abstract
Abstract
Flood is among phenomena which result considerable damages to resources and is a serious issue among hydrologists. The proper estimation of runoff is necessary for designating appropriate approaches for its control or optimal management. Various problems have been reported in application of ...
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Abstract
Flood is among phenomena which result considerable damages to resources and is a serious issue among hydrologists. The proper estimation of runoff is necessary for designating appropriate approaches for its control or optimal management. Various problems have been reported in application of empirical models. The regional analysis of runoff with different return periods by applying watershed characteristics is an alternative with numerous applications. In this study, mean discharge data of 7 hydrometric stations in Kurdistan Province watersheds, Iran, were collected for a period of 30 years and discharges with return periods of 2, 5, 10, 20, 25, 50, 100 and 200 years were consequently calculated using SMADA package. The relationship between mean discharges with different return periods and 26 physiographic and climatic factors were evaluated by using bivariate and multivariate regression models using SPSS 13.5 package and their partial influence were also determined. The results of the study showed that the nonlinear models performed better than linear regression. The main variables include the area, main waterway length and Gravellius factor. Data analysis also revealed the possible change of variables and their importances in determination of monthly mean discharges with different return periods.
Keywords: Kurdistan Province, Physiographic characteristics, Return Period of flood, Flood modeling
Research Article
F. Khamchin Moghadam; H. Sedghi; F. Kaveh; M. Manshouri
Abstract
Abstract
Most heavy storms result in destructive floods. One of the basic elements in analyzing floods in watersheds without data is hourly storms. The Determination of the storm of the watershed needs regional analysis of storms and transferring them to the gravity center of the watershed. Maximum ...
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Abstract
Most heavy storms result in destructive floods. One of the basic elements in analyzing floods in watersheds without data is hourly storms. The Determination of the storm of the watershed needs regional analysis of storms and transferring them to the gravity center of the watershed. Maximum daily precipitation ( ), is the most accessible storm in any region, which can be converted to hourly precipitation. The analysis of the point and regional is one of climate studies requirement. Regionalization of , can be an influential step toward analyzing storms and floods. In order to accomplish such a task, two approaches are possible, one is using the old methods of geographical regionalization and the other one is using the new methods like "Cluster Analysis" and "L-Moments Homogenous Tests". In this paper second approach was employed. All existing rain-gauge stations (N=396) were considered and their available data were collected in this study. Basic tests were applied and 266 stations were removed due to the lack of the required conditions and only 130 stations were used in analysis. "Principal Components" method was used to omit the uninfluential variables (only 6 variables out of 21 were proved as basic and important). "Hierarchical Clustering" was used in the process of regionalization of the stations indicated of seven different regions. These regions were distributed in different locations throughout the country and the regionalization map is presented. The "L-Moments Homogenous Tests" were also employed for further indication. According to the final results, the regionalization of of Iran's rain-gauge stations can be defined as 7 homogenous regions.
Keywords: Regionalization, Maximum daily precipitation, Principal Components, Cluster Analysis, L-Moment
Research Article
N. Sayari; M. Bannayan Aval; A. Alizadeh; M.B. Behiar
Abstract
Abstract
Accurate prediction of hourly minimum temperature is required for various crop models which simulate photosynthesis and transpiration. Such data can be used for crop protection and reducing the crops injuries due to freezing as well. Our objective of this study is employing trigonometric and ...
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Abstract
Accurate prediction of hourly minimum temperature is required for various crop models which simulate photosynthesis and transpiration. Such data can be used for crop protection and reducing the crops injuries due to freezing as well. Our objective of this study is employing trigonometric and pattern recognition (k-NN) approaches to evaluate their potential in prediction of hourly temperature for the whole 24 hours and also minimum temperature time occurrence. Our observed data contain every 3 hours minimum temperature data for 16 years of synoptic Mashhad climate station. Various scenarios were employed to predict the minimum temperature for first of Aban and first of Ordibehesht using, 1 day, 7 days, 110 days and 315 days observed data for next day minimum temperature prediction. Our results showed that if there is no full access or partly access to the minimum temperature data then the trigonometric function including Sine function is able to reproduce the required data. k-NN approach showed that as the distance of data to target data decreased the accuracy of prediction increased.
Keywords: Minimum temperature, Freezing, Sine model, Sine-Expo model, Prediction, Mashhad
Research Article
M. Bannayan Aval; A. Mohamadian; A. Alizadeh
Abstract
Abstract
Climate variability empowers critical consequences on sustainability of soil and water resources. In this paper the trend of annual and seasonal time scale of temperature (minimum, maximum, average), relative humidity (minimum, maximum, average), precipitation, wind speed, extreme events, cloudiness, ...
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Abstract
Climate variability empowers critical consequences on sustainability of soil and water resources. In this paper the trend of annual and seasonal time scale of temperature (minimum, maximum, average), relative humidity (minimum, maximum, average), precipitation, wind speed, extreme events, cloudiness, reference evapotranspiration employing Mann-kendall and least square errors were studied. These parameters showed direct or indirect effect on climate variability in northeast of Iran. The results, for example in Mashhad station, showed an increasing trend in temperature, decreasing trend in humidity and no trend in precipitation. In addition, there were an increasing trend in the number of clear days (no cloud) and a decreasing trend in number of cloudy days across all study stations but Mashhad.
Keywords: Trend Analysis, Temperature, Relative Humidity, Precipitation, Wind Speed, Extreme Climate Events, Reference Evapotranspiration, Mashhad Climate Change
Research Article
M. Taghipour; H. Khademi; Sh. Ayoubi
Abstract
Abstract
Accumulation of heavy metals in soils has become a serious environmental problem in many parts of the world. No information is currently available on the distribution pattern of heavy metals concentration in soils of Hamadan province. The objective of this research was to determine the spatial ...
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Abstract
Accumulation of heavy metals in soils has become a serious environmental problem in many parts of the world. No information is currently available on the distribution pattern of heavy metals concentration in soils of Hamadan province. The objective of this research was to determine the spatial distribution of Pb and Zn and its relationship with land use and parent materials of a selected area surrounding the city of Hamadan. A total of 263 composite surface soil samples (0-10 Cm) were taken from an area of about 1600 km2. The location of each sampling site was recorded by using a GPS and its land use type (residential, uncultivated, agricultural land and dryland wheat) was also determined. In addition from six major types of bedrock in the Hamadan province were also sampled with 3 replicates. The total and plant available Zn and Pb in soil samples and the total concentration of these elements in parent rocks were measured by atomic absorption spectrophotometer after extraction. Selected soil properties including pH, electrical conductivity, organic matter, cation exchange capacity and soil texture were also determined. The spatial variability of variables was examined by variography and kriging analysis. The mean concentration of total and available Zn were 71.4 and 2.5 mg Kg-1 and those for Pb were 24 and 2.5 mg Kg-1, respectively. The results of geostatistical analysis showed that spherical model was the best model for describing the spatial variability of Pb and Zn. The range of influence was estimated 9750 m for Pb and 11550 m for Zn. It seems that the major factor controlling the high concentration of total Pb and Zn in the area is land use type. Analysis of parent rock samples indicated that shale as the major parent rock occurring in the southeast and west part of the study area contains a high quantity of Zn (96.2 mg Kg-1). Therefore, it appears that Zn has entered the soils in the study area through the weathering of parent materials. In other words, the content of Zn in the soils studied seems to be mainly controlled by soil parent material and land use. A significant correlation was found between organic matter and the concentration of Pb.(r2= 0.35) and Zn (r2= 0.33).
Keywords: Spatial variability, Heavy metals, Parent materials, Variogram, Kriging, Hamadan
Research Article
F. Moshiri; M. Ardalan; M. Tehrani; Gh. Savaghebi
Abstract
Abstract
Due to calcareous soil conditions, zinc deficiency is a yield limiting factor for wheat production in Iran. One solution for this problem is the cultivation of Zn-efficient wheat varieties. Ten wheat cultivars (nine bread wheat and one durum wheat) with different tolerance to Zn deficiency ...
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Abstract
Due to calcareous soil conditions, zinc deficiency is a yield limiting factor for wheat production in Iran. One solution for this problem is the cultivation of Zn-efficient wheat varieties. Ten wheat cultivars (nine bread wheat and one durum wheat) with different tolerance to Zn deficiency were studied in a greenhouse experiment. Plants were treated with Zn (10 mg Zn Kg-1 soil as ZnSO4.7H2O) and without it. Based on the results of pot experiment, two wheat cultivars with different Zn efficiency were selected to assess the ability of phytosiderophore release from their roots. Visual Zn deficiency symptoms, such as light colored necrotic patches and reduction in plant height appeared more severe in Alvand, Mahdavi (bread wheat) and Yavares (durum wheat) cultivars. Under Zn deficiency, shoot dry matter decreased in most cultivars. Zn efficiency of wheat cultivars ranged from 80.4% to 106.2%. Based on shoot dry weight, Pishtaz and Darab were the most Zn-efficient and Alvand and Mahdavi were the most Zn-inefficient wheat cultivars. Zn supply markedly increased the Zn concentration and content of shoots of all cultivars. Cultivars differed in Zn uptake under Zn-deficient and Zn-sufficient conditions. On average, Zn-efficient cultivars had more Zn uptake efficiency compared to Zn-inefficient cultivars. Our results strongly suggested that sensitivity to Zn deficiency varied widely among wheat cultivars. Different susceptibility of cultivars did not correspond well with the Zn concentration of the shoot. In contrast, the total amount of Zn of shoot was better related to the sensitivity of wheat cultivars to Zn deficiency. Under Zn deficiency, different ability of genotypes to release phytosiderophore from roots was observed. Pishtaz exuded more phytosiderophore than Alvand. Higher Zn uptake in Zn-efficient wheat genotypes may be attributed to higher release rates of Zn-mobilizing phytosiderophores from roots.
Keywords: Wheat cultivars, Zinc efficiency, Zinc concentration, Zinc uptake
Research Article
A.R. Akhgar; K. Khavazi
Abstract
Abstract
In this study a greenhouse experiment was conducted to evaluate the role of ACC deaminase enzyme on alleviation of salinity stress of canola plant. Canola plants were exposed to Pseudomonas fluorescens strain P12 which contains a rhizobacter capable of producing Pseudomonas fluorescens in comparison ...
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Abstract
In this study a greenhouse experiment was conducted to evaluate the role of ACC deaminase enzyme on alleviation of salinity stress of canola plant. Canola plants were exposed to Pseudomonas fluorescens strain P12 which contains a rhizobacter capable of producing Pseudomonas fluorescens in comparison with plants exposed to mutant Pm12 unable to produce the required enzyme. The mutant was chemically produced using Ethyl Methane Sulfonate (EMS). Comparison of wild strain P12 with its mutant Pm12 indicated that under both saline and non-saline conditions, strain P12 significantly enhanced canola growth parameters including shoot fresh and dry weight, root dry weight, shoot length and green area index. In addition, canola plants inoculated with strain P12 absorbed higher rates of sodium, potassium, calcium, and magnesium, which can be attributed to enhanced roots growth. However, comparing strains P12 with Pm12 indicated that the production of ACC deaminase enzyme by P12 enhanced canola salinity tolerance and consequently, its growth.
Keywords: ACC deaminase, Pseudomonas sp., Salinity, Canola
Research Article
K. Esmaili; B. Naghavi; F. Koorosh Vahid; J. Yazdi
Abstract
Abstract
Weirs are the most common structures for discharge measurement in engineering research. Streamline curvature, non hydrostatic pressure distribution on weir and nappe adherence to the weir lead to differences between calculated and measured discharges. Thus discharge coefficient, which is the ...
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Abstract
Weirs are the most common structures for discharge measurement in engineering research. Streamline curvature, non hydrostatic pressure distribution on weir and nappe adherence to the weir lead to differences between calculated and measured discharges. Thus discharge coefficient, which is the ratio of real and theoretic discharges, is usually less than unity. In circular weirs the pressure distribution and velocity differs from sharp crested weirs which affect on flow discharge and extend the discharge coefficient more than unity. In this study, pressure distribution and velocity of different circular weir measured in laboratory models and compared with Fluent simulation as a numerical code. The results showed significant relation between measured and simulated data. Also it is found that the critical flow depth and separated flow are located respectively before and after the crest of weir. Nappe separation depends on overflow discharge and will shift to the downstream face of the cylinder in high discharges. To recognize the location of critical flow conditions and nappe separations, theoretical formulations has is proposed. The equations are found to be dependent on weir size and inflow conditions. The theoretical predictions showed good agreement in comparison with experimental results.
Keywords: Circular weir, Velocity and pressure distribution, Nappe separation, Critical depth, Fluent
Research Article
R. Khorassani
Abstract
Abstract
Plant species differ in their ability to grow at low available P soils in other words, plant species differ in P use efficiency at low P supply. This ability can be investigated by comparing P uptake efficiency of plants and relative effective factors. A pot experiment was carried out in the ...
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Abstract
Plant species differ in their ability to grow at low available P soils in other words, plant species differ in P use efficiency at low P supply. This ability can be investigated by comparing P uptake efficiency of plants and relative effective factors. A pot experiment was carried out in the growth chamber and sugar beet, maize and groundnut were grown in a low available P soil in a completely randomized design with three P fertilizer levels of low, medium and high. Three harvests were performed at two different growth periods. The results showed that at low P supply, sugar beet was the most efficient plant among three species as it showed the highest relative yield. The higher P use efficiency of sugar beet was due to a higher P uptake efficiency. Phosphorus uptake for sugar beet was 29 mg P plant-1 while those for maize and groundnut were 19 and 0.8 mg P plant-1, respectively. The main reason for higher P uptake efficiency of sugar beet was its higher P influx as compared to maize and groundnut. Under low P supply during the first growing period, P influx of sugar beet was higher than that of maize and groundnut by factor 4 and 22, respectively. Finally, the higher P use efficiency of sugar beet was due to a higher P uptake efficiency which in turn was due to a high P influx.
Keywords: Phosphorus efficiency, Phosphorus influx, Sugar beet, Corn, Groundnut
Research Article
M. Sadeghi; M.R. Gohardoust Monfared; B. Ghahraman
Abstract
Abstract
To estimate spatial variability of soil hydraulic functions, scaling methods were developed and have been widely used. Among these functions, physically based methods have been found more desirable because of possibility of estimating soil hydraulic functions from soil physical properties. ...
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Abstract
To estimate spatial variability of soil hydraulic functions, scaling methods were developed and have been widely used. Among these functions, physically based methods have been found more desirable because of possibility of estimating soil hydraulic functions from soil physical properties. In this paper, a new and physically based method has been described for scaling soil hydraulic conductivity function. In this method, use of effective capillary drive (hcM) has been proposed for scaling of soil water suction axis in the hydraulic conductivity function. Using this method, data of all natural soils, from sand to clay, can be presented by a unique exponential curve as reference curve. The approach was validated by 396 sets of hydraulic conductivity data, including all soil texture classes, taken from UNSODA database. To determine hcM, fitting Brooks-Corey and Gardner-Philip models and also a model-free method were used. The results indicated an acceptable performance of the proposed method. Brooks-Corey and Gardner-Philip models and the model-free method results showed the average absolute error of relative hydraulic conductivity between the scaled data and the reference curve as 0.019, 0.056, and 0.059, respectively. In the employed methods, fitting capability of the mentioned models can be taken into account as the only limitation. Thus scaling performance would be well if the mentioned models could fit well the hydraulic conductivity data and vice versa.
Keywords: Scaling, Soil unsaturated Hydraulic conductivity, Effective capillary drive, Unique exponential reference curve
