نشریه دانش آب و خاک
سال بیست و چهارم شماره 1 (بهار 1393)

Glomalin is a specific glycoprotein that is produced by a fungi belonging to the order Glomerales in phylum Glomeromycota. Noting the widespread symbiotic relation of these fungi with a large number of plants، considerable amounts of glomalin are entered into the soil ecosystems، annually. Heavy metals can influence the both symbionts physiology and hence glomalin production by the fungi. In this study، the effects of Cu levels were investigated on mycorrhizal establishment in corn plants inoculated by either Glomus mosseae or G. intraradices as well as glomalin production by the system. Copper levels of 0، 250 and 500 mg Cu. kg-1 soil (as CuSO4. 5H2O) were applied to the pots before plant culture. Non-mycorrhizal treatment was left un-inoculated as control. Easily extractable glomalin (EEG) and total glomalin (TG) were determined by the Bradford method after extraction from soil. With increasing Cu concentration in soil، shoot and root fresh and dry weights، P and K concentrations in shoot and root، root colonization، EEG and TG decreased and proline concentration in leaves، Cu concentration in shoot and root increased. The results showed that، glomalin levels in fungal treatments significantly increased compared to the non-mycorrhizal control. The results also showed a positive correlation between the measured glomalin and the percent of root colonization.

In order to evaluate the agro hydrological model of SWAP3. 03 for estimating soil water content under different qualities and quantities of irrigation water، an experiment was carried out on wheat varieties with three replications during 2005-2006 growing season in the research Field of University of Birjand. The treatments consisted of three water qualities (1. 4، 4. 5، 9. 6 dS/m)، and four levels of irrigation (50، 75، 100 and 125 % of crop water requirement). Water deficit and saline irrigation treatments decreased the accuracy of the model prediction for various growing stages. The best and worst estimates of the soil water content by the model belonged to the full irrigation treatment (I3) with RMSE values of 0. 93 to 1. 37 % and the least irrigation treatment (I1) with RMSE values of 1. 77 to 2. 57 %، respectively. With decreasing salinity، there was greater agreement between the measured soil water content values and those predicted by the model.

Flow separation at upstream of the inlet is one of the major problems that occurs in the intakes. The reason for this، which results in reduction of intake efficiency and sedimentation in front of the intake inlet، is the velocity difference at the upstream and downstream of the inlet. The velocity difference creates a separation zone at which flow circulation prevents the flow transition resulting in accumulation of sediments at the inlet of intake. One of the best methods to increase intake efficiency and eliminate vortices is to determine the optimal hydraulic conditions. Any method producing a uniform velocity between upstream and downstream of the inlet، reduces the secondary flow، separation zone، sedimentation and hence increases the intake efficiency. In this study a numerical model (SSIIM 2. 0) was applied to determine the optimal hydraulic conditions.

Iron (Fe) is an essential plant nutrient. The bioavailability and mobility of metals in soils depend on distribution of these metals between solution and solid phases and among solid phase components. Two sequential extraction procedures (Singh et al،1988 and Sposito et al،1982) were used to investigate the distribution of Fe chemical forms in 10 calcareous soils of Fars province varied in physico-chemical properties. Distribution of iron chemical forms in calcareous soils of Fars provinc were in the following order: FeEx = FeMnOSin = ND < FeOMSin < FeOMSpo < FeCaSin < FeSorSpo < AFeSin < FeCaSpo < CFeSin < FeReSin < FeReSpo، Chemical forms of Fe were significantly positively correlated with soil properties and DTPA extractable Fe. Absorbable iron (extracted with DTPA) showed significantly positive correlation with FeCa، FeOM and FeSor (Sposito et al،1982 proposed method). There were significant correlations between some chemical forms of Fe indicating the existence of a dynamic relationship between them in soils. Also، results showed that there were some problems as bad burning in flame of atomic absorption machine، in some soil extraction process.

Consequence of interrill erosion is a considerable issue of soil and nutrient losses especially in farmlands. Thus، factors affecting interrill erosion must be well known. The aim of the current study was to investigate the effect of surface sealing on soil interrill erodibility factor (Ki). Two sandy loam (S1) and clay loam (S2) soils from Ilkhichi farmlands with low organic matter and high Ki and one clay soil (S3) from Caleibar farmlands with high organic matter and low Ki were examined. Several pertinent chemical and physical characteristics of the three soils were measured. Rainfall simulation experiments were carried out on 200 kg of each soil sample under 5، 15، 25 % slopes and 21، 38، 50، and 81 mm/h rainfall intensities. Relative sealing index (RSI) and the time needed to reach to the final infiltration rate (tlim) were measured in every combination of slope and rainfall intensity. The results showed that S1 soil with RSI= 2. 23 and tlim= 6 min was the most sensitive and S3 with RSI= 8. 9 and tlim= 102 min was the least sensitive to surface sealing. The findings indicated that there were no significant differences among Ki’s at different slopes and the assumption of constant Ki for all soils was correct، except for soil S1. There were also no significant differences among Ki’s at different rainfall intensities for the examined soils.

Channel confluence is a common feature of the most irrigation and drainage channels and river systems، where tributary conflicts the main channel. Due to complex flow patterns - because of variation of magnitude and direction of flow velocity، flow and sediment discharge -bed erosion، shoreline erosion and accumulation of sediment at the downstream of river confluence are common processes. This phenomenon causes damage of the adjacent structures and changes river morphology. A common practice to prevent and control bed erosion at river confluence is to use a cover of stone or rip rap. Criterion for design of stone has not been developed in the past، therefore in this study، some stone sizes (D50) with different specific gravity under different hydraulic conditions have been tested to determine the factors that affect the stability of riprap at the threshold and failure conditions. The stability number (SN)، which is a decisive factor for riprap stability has been studied for some different stone sizes (D50)، specific gravity (Gs) and flow discharge ratio (Qr). It was found that with increasing flow rate، the stability number decreased; also it revealed that the stability number decreased by decreasing particle size of riprap for a constant discharge ratio (Qr). Apart from the effects of the other variables، the stability number (SN) increased، as the specific gravity of stone (Gs) decreased. Finally، a relationship with an acceptable accuracy (R2 = 0. 86) was determined to estimate the stability number (SN).

The soil evolution of a region is function of type and intensity of soil forming factors and processes and can be studied using some soil properties such as pedogenic Iron (Fed) content in A and B horizons and its transformation with time and accumulation index of Iron oxides. In this research work different forms of Iron oxides were studied in nine soil families from eleven soil profiles of Marand region. The dominant geomorphologic units in the study area were rock pediment، mantled pediment، piedmont plain and alluvial plain and according to soil-geomorphology relationships، eight geomorphologic surfaces were diagnosed inside the units. Based on soil morphological and physico-chemical properties and different forms of Iron oxides significant correlation were observed between total Iron (Fet)، pedogenic Iron (Fed) and noncystalline Iron (Feo) as well as Iron forms with each other. The variations of different Iron forms followed the geomorphologic units and increased from mountain to alluvial plain units. But Fet، Fed and Feo changes in each unit depended on stability of geomorphologic surfaces. The highest (11. 24 g/kg) and lowest (1. 53 g/kg) Fed were observed at buried argillic horizon in alluvial plain and mountain، respectively، which showed instability of mountain unit. The soils of stable surface of mantled pediment (Smp) surface were more developed by continuity of soil forming processes and the soils of mountain showed less development due to high slope and limited soil forming processes progressing.

Using slot in bridge piers is one of the reduction methods of scour depth around them. In this study، the flow field around a cylindrical pier located in a smooth bed with and without slot was simulated using FLOW-3D software. The RNG k-ε turbulence model was used for closing the Navier-Stokes equations. The comparison of the numerical results and laboratory measurements for one bridge pier without slot showed that the model could predict velocity and shear stress parameters with reasonable accuracy. The influence of the slot width on the flow field around bridge pier was then investigated. The formed vortex at downstream of the pier became smaller by increasing slot width. In the largest slot case، this vortex was completely disappeared. Also، by increasing slot width، the value of the maximum velocity occurred adjacent the pier decreased، but its location was fairly constant. Finally، because of the lower reduction of the longitudinal velocity of the flow in the vicinity of the upstream face of the pier for the largest slot، shear stress pattern in this area was similar to that of the upstream area.

Consequences of heavy metals accumulation in soils are of concern. One way of decontaminating heavy metals from soils is the use of chelating agents، particularly EDTA. In this research، three soils contaminated by Zn، Pb and Cd with total amounts (of these metals) of 10. 5، 55. 8 and 80. 6 mmol kg-1 were collected from the surface layer (0-20 cm) of the lands surrounding a zinc-lead smelting plant in Zanjan province. The release of Zn، Pb and Cd by Na2H2EDTA using a one-step batch method for 180 minutes as well as the effects of EDTA concentration، solution/soil ratio، kinetics of release of metals، changes in pH and concentration of Ca and Fe in extracts were investigated. Results showed that increasing concentration of EDTA raised Zn and Pb release much greater than that of Cd. Furthermore، the orders of the release percentages for the three metals were quite different in the three soils. During the release process، pH of the extracts exceeded 7. 2 and then fixed at about 8. 1. Meanwhile، the average concentration of Ca in extracts became more than 1000 times greater than that of Fe. On average، 96 percent of the extracted Cd was released at less than 30 minutes. This figure was 76 percent for Zn and Pb and the release time were sometimes greater than 30 minutes. Compared to other kinetic models، the kinetic data was best described by simplified Elovich، power function and parabolic diffusion equations. According to the results، release of Cd and Pb from the soils was enhanced by low (5:1) and high (50:1) solution/soil ratios، respectively.

One of the hydraulic flow types in pipes is transient flow، which is specifically called water hammer. Transient flows start from a steady state and end to another steady flow. Several calculation methods introduced to study water hammer phenomenon، and have been used since 1950. One of the applied methods is Joukowski equation، which has been selected as the manual solution in this study. Because of ignorance of momentum in most of the pipeline design software such as WaterCad and WaterGems، they can not calculate unsteady flow. So it is important to launch specific software to calculate unsteady flow especially water hammer. In fact Hammer and Hytran software are numerical simulations of hydraulic phenomenon of water hammer in conduits of water، sewage and industrial sewage. In this study the ability of these software are compared with Joukowski equation solution method. For this purpose maximum pressure of water hammer in pump at sudden shut-off condition with no control equipment is studied using Hammer & Hytran software and Joukowski equation. Results show an overestimated water hammer pressure in Joukowski equation solution. Hytran and Hammer software calculate the surge pressure rate 23% and 32% less than Joukowski equation، respectively.

Formation of shock waves has high importance in study of supercritical flows. These waves are often found during supercritical flow in the non-prismatic channels. In the present study، values of depth and instantaneous velocity were measured in various points of shock waves observed in the straight-wall contraction for four Froude Numbers. Numerical simulation of supercritical flow in the contraction was performed using RNG k-ε and RSM turbulence models of FLUENT software. In order to investigate the accuracy of the models in calculation of wave profile and wave velocity a comparison was also done between the results of numerical models and measured values for Fr1=7. 0. The average relative errors of the wave depth calculation using RNG k-ε and RSM turbulence models were 1. 82% and 1. 06%، respectively. Also، for the wave velocity، the values were 2. 25% and 1. 44%، respectively. The results showed that the RSM model performed slightly better than RNG k-ε model in simulating shock waves.

The present study was conducted to evaluate the effect of agriculture on phosphorus (P) accumulation and changes of inorganic P fractions in some soils around Yasouj. Ten pairs of agricultural and virgin fields adjacent to each other were selected and composite soil samples were taken of each land use in three replications from the depth of 0-30cm. After sample preparation، inorganic P fractions were determined by successive extraction with NaHCO3 (NaHCO3-P)، NH4OAc (NH4OAc-P)، MgCl2 (MgCl2-P)، NH4F (NH4F-P)، NaOH-Na2CO3 (HC-P)، citrate-dithionite-bicarbonate (CBD-P)، and H2SO4 (H2SO4-P). Statistical analysis was carried out based on paired factorial in a completely randomized design. Results showed that agricultural land use significantly increased all of the P fractions except HC-P at 1% level. Sum of the inorganic P fractions in agricultural fields were 64 to 318 mg kg-1 higher than those of virgin soils. Averages relative increases of various fractions'' were NaHCO3-P 5. 2%، NH4OAc-P 18. 8%، MgCl2-P 8. 4%، NH4F-P 12. 2%، HC-P 0. 22%، CBD-P 15. 1% and H2SO4-P 39. 4%. Results indicated the high amount of P fertilizers application and accumulation in the region. In addition، results indicated that there was the probability of transformation of applied P to stable Ca-P compounds.

Land suitability evaluation is determining the fitness of a given tract of land based on its potential for a defined use. With regard to information in references and land suitability evaluation methods، square root parametric method for qualitative suitability evaluation and yield per unit area for quantitative suitability evaluation were selected. Potential yield was calculated about 8. 5 t/ha using the method proposed by FAO (AEZ). The quantitative land suitability evaluation and its classes were defined according to incorporating potential، actual and marginal yields with the qualitative suitability evaluation results. The predicted yield varied from 5. 3 to 7. 9 t/ha in different land units and high correlation between the observed and predicted yields indicated the appropriate selection of the factors and evaluation methods. Obtained results showed that important limiting characteristics were climatic characteristics، especially relative humidity percentage after milky stage، harvest stage and mean temperature of the developing stage. Light soil texture in coastal lands، high groundwater table، and severe limitation of drainage in some land units caused suitability reduction. In the studied area the climatic class was determined low suitability for rice، while، results of quantitative evaluation showed that the most of the land units had high suitability for rice cultivation. With regard to low area of rice cultivation for each person، basic consumption of produced rice by farmers and their low pure income، using of secondary cultivation was proposed subsequent to rice harvest.

Infiltration is one of the most important soil physical variables and basic data in rainfall–runoff models for water loss determination in watersheds. Its measurement is، however، time consuming and costly. For this reason، soils infiltration rates determination by different models is always a serious concern to researchers. In this research، a single event precipitation was measured using rainfall simulator during a 90-minute rainfall for determination of the best infiltration equation in watershed scale. The parameters of five infiltration models namely Kostiakov، Green-Ampt، Horton، NRCS and Philip، were estimated by sum of squared error optimization for four different land uses and three soil textures of sandy clay loam، loam، and sandy loam. The cumulative infiltration rates estimated from the different models were compared using eight different statistics. The results showed that the Kostiakov and NRCS models had the highest priority score and the most permanent trend for accurate estimating of cumulative infiltration rate in different land uses whereas the Horton model was situated in the next position. Overall، the empirical models (Kostiakov، NRCS and Horton models) had the more realistic efficiency than the physical models (Green-Ampt and Philip models).

Diagnosis and recommendation integrated system (DRIS) can be used as an efficient method to interpret the results of plant analysis and the nutritional needs of field and orchards crops. To determine the DRIS norms in sugar beet (Beta vulgaris L.)، leaf samples were collected from 57 fields and N، P، K، Ca، Mg، Fe، Mn، Zn، Cu and B concentrations in the leaves were measured. On the basis of yield amounts، the fields were divided into two groups of low and high yielding populations. Standard DRIS norms were established for the different nutrient ratios and also DRIS indices were calculated to evaluate nutrients balances and order of nutrients requirements. DRIS-derived sufficiency ranges in sugar beet leaves were 3. 0-5. 4، 0. 21-0. 47، 1. 7-3. 7، 0. 55-1. 6، 0. 19-0. 34 % for N، P، K، Ca، Mg and 24-168، 42-138، 10-19، 10-14، 9-20 mg/kg for Fe، Mn، Zn، Cu، B، respectively. The average of DRIS indices of priority based on the macro and micro nutrients as P>Cu>N>Zn>K>Ca>Mg>Fe>Mn>B was determined. The nutritional balance DRIS index of all fields with low yielding population was much more than zero، indicating an imbalance nutritional in low yielding fields.

This study presents a supervised committee fuzzy logic (SCFL) model to estimate transmissivity in the aquifer of the Tasuj Plain، Iran. The estimation of transmissivity especially in a heterogeneous aquifer is expensive and time consuming. In this study، fuzzy logic models such as Mamdani fuzzy logic (MFL)، Larsen fuzzy logic (LSL) and Sugeno fuzzy logic (SFL) were applied to estimate transmissivity using hydrogeological and geophysical survey data. The results showed that all of these models have a similar fitting to the transmissivity data in the Tasuj Plain. The SCFL model was adopted to combine output of the three single fuzzy models instead of the selecting superior single model. To reap the advantage of considering single models، the SCFL proposes a nonlinear combination of individual FL model outputs through a committee fuzzy logic model. The SCFL method uses an artificial neural network (ANN) model to re-estimate transmissivity based on the output of the three FL models. The result showed improvement to the committee machine with a linear combination of FL models estimations. The results also showed significant fitting improvement to individual FL models.

There are different methods for estimation of soil infiltration equations’ coefficients depending on irrigation system. In this study، seasonal variations of the Philip equation coefficients (PEC) were investigated in three different soil textures including loam، sandy loam and sandy clay loam soils. The PEC،s were calculated using four following mehods: Rawls، one-point Shepard، Clemmens and adjusted Weibo methods. The advance phase was simulatied using SURFACE software. The results showed that the Rawls and adjusted Weibo methods estimated the advance phase more accurate than the others in the three soil textures. The sorptivity coefficient (S) at the fourth irrigation was compared with the first one and it showed that S decreased to 85، 10 and 82 percent for Clemmens، one-point Shepard and adjusted Weibo methods، in loamy soil، respectively. Similarly، it decreased to 74، 54 and 65 for the sandy clay loam soil from first to fourth irrigation event. The result showed no trend for transmisivity coefficient (A). Sensitivity analysis remarked that the S was more affected by inflow discharge in one-point Shepard and adjusted Weibo methods than the two others، and also it was affected by hydraulic conductivity in Rawls method.

Increasing salinity in agricultural lands has led to the limitation of crop cultivation and reduction of crop yields. Therefore، many researchers in the world focus on finding alternative crops. Halophytes، because of some mechanisms such as antioxidant systems are resistant to salt stress. In order to study the effects of NaCl salinity and nitrogen levels on growth، ascorbic acid and nitrate contents in the edible halophyte S. aegyptiaca، a factorial experiment with 5 levels of NaCl including 10، 20، 40، 60 and 80 dS m-1 as the first factor and three levels of nitrogen including 25، 50 and 75 mg kg-1 in urea form as the second factor in completely randomized design with three replications was conducted under the greenhouse conditions. NaCl treatments were applied after the plants had reached a stand. Nitrogen was also added at two stages within 10 days. The results showed that the highest fresh and dry weights of plants were obtained at 20 dS m-1 salinity level. The fresh and dry weights decreased more by increasing salinity. At salinity levels of 10 and 20 dS m-1، the fresh and dry weights increased with increasing nitrogen levels، but at higher salinity levels، the moderate levels of nitrogen produced the highest fresh and dry weights. With increasing salinity up to 40 dS m-1 the vitamin C content firstly increased and then decreased with further increase in salinity. The vitamin C levels also decreased with increasing nitrogen levels. Furthermore، the nitrate concentration increased with increasing nitrogen levels. At salinity levels of 10، 20 and 40 dS m-1 concentration of nitrate at different levels of nitrogen was constant but decreased at 60 and 80 dS m-1 salinity levels with decreasing nitrogen levels.

The assessment of water quality in reservoirs is essential because reservoirs are often one of the main sources of water for human consumption and irrigation. In this paper، a two-dimensional، laterally averaged CE-QUAL-W2 model was used to simulate the water surface elevation، water temperature، and water quality parameters such as dissolved oxygen and nutrients in the Ilam dam reservoir. After simulating the water level، the temperature and dissolved oxygen were respectively simulated with an average absolute error 0. 76°C and 1. 41mg/L during the calibration period and 1. 18°C and 1. 18 mg/l during the verification period. The model results showed relatively good agreement between the measured and simulated data. After model calibration and validation، in order to investigate the hydrological changes on reservoir water quality، two inflow scenarios were simulated based on the dry and normal years. The results of the dry year indicated a six-month stratification period from April to September. Due to increase of water retention time in the dry years، Chlorophyll A concentrations increased in summer so that the reservoir conditions changed from mesotrophic to eutrophic. A similar pattern was observed between the temperature and dissolved oxygen profiles. In the normal year، stratification period included seven months from April to October. Due to decrease of water retention time in reservoir in the normal year، Chlorophyll A concentrations decreased in summer so that the reservoir conditions changed from mesotrophic to oligotrophic condition.