نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال هجدهم شماره 3 (پیاپی 69، پاییز 1393)

Organic substances produced by cyanobacteria and some polymeric compounds play a role in soil aggregation and increase soil structure stability in sandy soils. Effects of biological soil crusts and some polymeric compounds on some properties of a sandy soil were investigated in this research. Inoculation of three cyanobacterial treatments (Nostoc sp., Phormidium sp. and their combination) and four time intervals on crust formation, organic carbon and calcium carbonate contents, resistance to penetration and MWDD in soils below the crusts were studied in the first experiment. Combination of two cyanobacterial species in 60 days treatment with 2.2 % organic carbon, 0.2 Mpa resistance to penetration, and 96.7 % large aggregates was introduced as the superior treatment. Effect of superior cyanobacteria and time treatments on aggregate size distribution was studied in the second part of this experiment. Sixty-day treatment with 96.7 % of large aggregates was the most effective treatment. Structural stability of a sandy soil influenced by four concentration levels (0, 1, 2 and 4%) of anionic polyelectrolyte polymer at the depths of 1, 2 and 3 cm was investigated in the second experiment. Four percent concentration treatment of polymer with 0.6 Mpa resistance to penetration and 90.9 % large aggregates was the most effective one. A significant difference in resistance to penetration among three depth intervals was also observed.

Phytoremediation models are important to understand the processes governing phytoremediation and the management of contaminated soils. Little effort has been made for evaluating the potential of the phytoremediation of metals based on the mathematical models. Therefore, the purpose of this study was modeling the phytoremediation of the nickel-contaminated soils. For this purpose, a model was recommended for estimating the rate of the phytoremediation of nickel from the soil by means of relative transpiration reduction and concentration of nickel in the plant functions. To evaluate the model, soil was contaminated with different levels of nickel by nickel nitrate. Then, the pots were filled with contaminated soil and Basil (ocimum tenuiflirum L.) seeds were planted. To avoid the dry tension, the pots were weighed and irrigated to the point of field capacity (FC) at short time intervals (48 hours). The plants were harvested in four times. At each harvesting stage, the relative transpiration values and nickel concentration in the soil and plant samples were measured. The performance of the model was evaluated by statistical methods such as Maximum Error, Root Mean Square Error, Coefficient of Determination, Efficiency of Model and Coefficient of Residual Mass. Results demonstrated that in the case of nickel contamination in soil, changes in the relative transpiration of Basil can be measured by the two proposed models and the linear model (R2=0.94) has a better performance compared to the nonlinear one (R2=0.84). Also the model obtained from the combination of linear function and nickel's concentration in soil has a relatively good (R=0.7) fit with the measured values of the remediation rate of nickel in soil.

Organic acids play an important role in improving the bioavailability of soil nutrients. The objectives of this study were to determine the effect of oxalic acid on the release of soluble, exchangeable and non-exchangeable forms of K from micaceous minerals and potassium feldspars, and also to investigate the trend of K release by time. A laboratory study was carried out using a completely randomized design with two replicates. Biotite, phlogopite, muscovite, Zanjan and Yazd K-feldspars (< 50 μm size) were treated with 0, 10 and 100 mM of oxalic acid solutions for a period of 5 hours and 20, 60 and 90 days. The amount of K was determined by flame photometer. The results indicated that most amount of soluble, exchangeable and no-exchangeable K was released by 100 mM of oxalic acid. The maximum soluble K (0.86 gKg-1) was released from phlogopite, and the maximum exchangeable and non-exchangeable K (1.5 and 29.6 gKg-1, respectively) were released from biotite. Muscovite with 0.19, 0.34 and 1.41 gKg-1 of soluble, exchangeable and non-exchangeable K, respectively, had the lowest release of K among the studied minerals. The kinetics K release from minerals consisted of two phases. The first phase was relatively rapid and then it had a slow rate until the end of the experiment. Given that the applied concentration of organic acid was high, potassium release during the experiment period did not reach the steady state. Therefore, a longer period of release experiment is suggested.

Phytoremediation is one of the best methods for cleaning heavy metal contaminated soils. In this method, tolerant plants with high absorption potential are used to clean up the pollutant. The purpose of this greenhouse study was to find the most suitable plants with the highest Zn translocation factor and shoot concentration. Soil samples were collected from zinc and lead Bama mine in Isfahan province, Iran. To compare the hytoextraction power, Heliantus annus.L., Thlaspi caerulescens, Trifolium pretense L. and Amaranthus retroflexus were planted in 8 kilogeram pots. The experiment was conducted in completely randomized design with three replications. After seventy days, plants root and shoot were harvested and Zn concentration was measured. The result showed that Thlaspi caerulescens had significantly higher root and shoot Zn concentration (3125 and 4041 mg kg-1, respectively). The highest bioaccumulation factor and translocation factor was observed in Thlaspi caerulescens. Based on this research, Thlaspi caerulescens was one of the suitable Zn hyper accumulators for cleaning up the Zn pollution.

Intermittent irrigation of paddy fields with long intervals can cause cracks in heavy soils, facilitate loss of water and finally damage the crop. This study was carried out in order to investigate the cracking trend and some other factors affecting soil cracking in four different physiographical areas of paddy field. The study areas were Rasht, Shanderman, Astaneh and Khomam in Guilan province. The experiment was carried out in paddy fields with transplanted rice by determining the physical properties relevant to cracking behavior after irrigation withdrawal in the reproductive stage. Soil analysis showed that despite similarity in type of dominant minerals, the linear expansion coefficients of Rasht and Khomam soils were higher than those of two other areas. In addition, there was a significant relationship between crack dimensions and volumetric soil water content and clay content. Furthermore, the temporal variation in study of crack development (depth, width and density) showed that they varied in different areas and were affected by volumetric soil water content and the groundwater depth. In addition, the depth of cracks in all soils did not reach the hard pan. All the investigated soils showed a definite threshold for width and depth of cracks for 20-25 days after irrigation withdrawal. After this period, specific values for width (about 3.0, 2.0, 2.5, and 5.0 cm) and depth of cracks (20, 25, 17, and 27 cm) were registered for Astaneh, Khomam, Shanderman and Rasht, respectively.

Although addition of amendment materials to soil is not for changing of soil K status, secondary effects of these materials can be important in K distribution among soluble, exchangeable and non-exchangeable forms. In this research, effect of addition of 2% zeolite, 2% vermicompost and 1% zeolite+ 1% vermicompost on 10 calcareous soils of Fars province belonging to five orders was investigated. The experiments were done as a randomized complete block with three replicates. Samples were incubated at 22±2 °C and 50% of saturated moisture content for 90 days. Then different forms of K were determined in the samples. Zeolite application induced 279 mg kg-1 increase in exchangeable K and 24 mg kg-1 decrease in non-exchangeable K, but it had not a significant effect on soluble K. Although vermicompost application increased soluble and exchangeable K, its effect was more sensible for soluble K (139 mg kg-1). Zeolite+vermicompost application increased all forms of K. Increase in soluble K with vermicompost application may increase risk of K leaching; but zeolite application can preserve K in exchangeable phase and inhibit K leaching and fixation.

Sediment is as one of problems related to water resources utilization. Numerous formulas have been developed for bed load estimation in rivers. In this study, eleven common formulas including hydrologic and hydraulic methods such as Einstein; Tofalti; Meyer, Peter and Muller; Van Rayne; Modified Van Rayne; Yalin; Bagnold; Fraylink; Habibi and Sivakumar and Samaga were used for selection of the most suitable bed load estimator formula in Kharajgil hygrometry station on Navrud river. The results showed that Habibi and Sivkumar formula is the most suitable with the mean computed to observed data=1.35, standard deviation computed to observed=1.96, RMSE=1.63 and ill sorted ratio(computed transportation ratio to observed)=33.82% within the range of 0.5 to 2.

While the mass density current penetrates the stagnant fluid, a plunge point occurs. In this regard, the boundary of the dense fluid with ambient fluid is determined at the plunge point height. In this research, the hydraulic parameters of the dense flow and the bed slope of the stagnant fluid which have a significant effect on the plunge point have been investigated under the two turbulence models: the k- and the RNG at the Flow-3D model. To achieve the purpose of this research, a physical model was set up at the hydraulics laboratory of Shahid Chamran University (SCU), Ahwaz, Iran. Then, using the Flow-3D model with both the k- and the RNG turbulence model, the height of the plunge point was simulated according to the same experimental condition. Findings showed that the predicted depth under the RNG model is closer to the results of the physical model. For example, the k- and RNG model for the 12% slope can estimate the plunge point depth by 30% and 12.28% respectively more than the experimental data. However, for all the slopes, the k-e model can on average overestimate by 27% and RNG model 10.5% more than the results of experimental data. The statistical analysis showed that the RNG model predicts the plunge point depths with a satisfactory precision.

Soft computing techniques have been extensively studied and applied in the last three decades for scientific research and engineering computing. The purpose of this study was to investigate the abilities of multilayer perceptron neural network (MLP) and neuro-fuzzy (NF) techniques to estimate the soil-water retention curve (SWRC) from Khozestan sugarcane Agro-Industries data. Sensitivity analysis was used for determining the model inputs and appropriate data subset. Also, in this paper, the van Genuchten and Fredlund and xing models were used to predict SWRC. Measured soil variables included particle size distribution, organic matter, bulk density, calcium carbonate, sodium adsorption ratio, electrical conductivity, acidity, mean weight diameter, plastic and liquid limit, resistance of soil penetration, water saturation percentage and water content for matric potentials -33, -100, -500 and -1500 kPa. The results of this study in terms of various statistical indices indicated that both MLP and NF provide good predictions but the neural network provides better predictions than neuro-fuzzy model. For example, using MLP and NF models values of NMSE at prediction θs, θr, α, n and m in Fredlund and Xing equation corresponded to (0.059, 0.065), (0.154, 0.162), (0.109, 0.117), (0.129, 0.135) and (0.129, 0.145), respectively. Furthermore, α and n parameters at the first depth, and θr and α parameters at the second depth in Fredlund and Xing equation were estimated with higher accuracy compared with equivalent parameters in van Genuchten equation.

Salt with various kinds and contents is one of the most important factors affecting soil splash erosion rate. The aim of the present study was to evaluate various salinity and alkalinity levels on splash erosion rate and its components (upslope, down slope and total splash) in different slopes. A factorial experiment with three factors was conducted in a completely randomized design with three replications by a Multiple Splash Set (MSS). The treatments included splash erosion rate at 4 levels of salinity and alkalinity (EC: 2 dSm-1, SAR: 2، EC: 15, SAR: 24، EC: 56, SAR: 42، EC: 113, SAR: 47), two levels of rainfall intensity (2. 5 and 3. 5 mm. min-1) and 5% and 15% slope levels. The results showed that the organic carbon and mean weight diameter (MWD) decreased at higher levels of salinity and alkalinity. The effect of saline and sodic, slope and rainfall intensity levels on the splash erosion rate and its components was significant. Also, slope×saline and sodic, rainfall intensity×saline and sodic, slope×saline and sodic×rainfall intensity interaction treatment caused a significant increase in splash erosion rate and its components. It seems that splash erosion is increased in saline and sodic soils due to the reduction in OC and MWD.

Improper use of rangelands may lead to their destruction. Therefore, the conversion of these degraded rangelands to agricultural lands and other land uses may improve their soil quality. The purpose of the present study was to evaluate the impact of cultivation in the degraded rangelands on some soil characteristics in Safashahr region of Fars province. Four land uses including the rangeland with sparse vegetation (degraded rangeland), the rangeland converted to agricultural land over 17 years, the agricultural land converted to apple orchard for 4 years and also to an apple orchard for 40 years were selected. Samples were randomly taken from each land use at two depths (0-20 and 20-50 cm) with five replications. The results revealed that land use change significantly increased organic matter and MWD in both soil depths. Bulk density and water dispersible clay increased in agricultural land and new orchard while a decrease was observed for old apple orchard. It is suggested the traditional farming to be replaced with new cultivation methods like minimum tillage and no tillage. Overgrazing of the rangelands must also be avoided.

Cylindrical and semi-cylindrical weirs are used in water distribution systems for flow measurement in open channels and for control of water surface. Review of literature shows that cylindrical and semi-cylindrical weirs are not widely used in practice. Because of their low construction cost and simplicity, an investigation was done to study cylindrical and semi-cylindrical weirs in terms of their hydraulic characteristics such as discharge coefficient, energy loss and flow depth over the spillway crest. The research was done for 128 models in the hydraulic laboratory of water engineering department, Shiraz University. According to the results, due to flow separation from body of the weirs, flow coefficient increases in the cylindrical and semi cylindrical weirs by 57%. It was found that discharge coefficient increases by increasing the total head of upstream. Therefore, construction of cylindrical and semi-cylindrical weirs and side weir is recommended due to reduction in weir length, increased hydraulic efficiency, and reduced administrative costs compared to other wide edge side weirs.

The aim of this study was to evaluate soil properties changes in a soil toposequence series in Khuzestan province. Twelve soil profiles were dug in north to south direction in this province, according to the changes of the slope in Karoon’s alluvial deposits. The results showed that soil texture regularly changes to heavier form from north to south. It was slightly of redoxomorphic features in low land. Therefore, salic horizon was formed in this land. Despite high water table in this area, gray or mottle forms were few due to high soil salinity. The carbonates were eluviated from surface to subsurface horizon; therefore, calsic horizon was formed due to illuviation. Secondary carbonate accumulation was maximum in the studied area. Both classic horizon and cambic horizon were formed in some pedons under long time cultivation in north regions. These developments were originated from organisms that grew under good drainage class. The smectite was seen in the south part of region. It may have been transported by river and deposited under high salinity and flocculated in contact to Persian Gulf’s saline water. The palygorskite was not seen in all patterns. This clay was removed in pedons under long time cultivation in the north area due to more leaching. High irrigation water can accelerate palygorskite transformation. Also, the XRD patterns showed that chlorite, illite, kaolinite and quartz were main clay minerals in the studied soils.

Determine appropriate locations with accuracy and speed required is for Floodwater spreading very important. The main objective of this research, preparation, use and evaluation decision support systems is based on GIS and RS techniques to identify and prioritization appropriate areas Floodwater spreading in the study area. In this study area suitable for flood water spreading were selected based on major criteria four, sub criteria eight and index twentyfour. Finally five scenario will be provide and assessment (a scenario based on the relative values for the criteria four, and different scenarios four based on the obvious one of the main criteria). Comparison desirability average among the scenarios five indicate that it is Sub watershed (1) In the scenario third (infilteration preferred, water application preference and equality of all the main criteria) had a higher average desirability therefore between Sub watershed 2 in this scenario is preferred more than the other Sub. Of between the two sub watershed ivar region considering that the desirability average, sub watershed (1) and implemented of between scenarios, scenario (1) (infilteration major criteria preferred) were selected as first priority. Second priority for Floodwater spreading site selection is belong to sub watershed 2, and with scenario (1).

The aim of this study was to assess the drinking quality of Shahrekord aquifer based on a GWQI (groundwater quality index) within a GIS framework. To do this, samples from 97 wells were analyzed for pH, Electrical Conductance (EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Turbidity, Ca2+, Mg2+, Na+, K+, Cl-, HCO3- and SO42-, and total hardness was also calculated. These water quality parameters were geostatistically mapped. Maps showed that maximum quality of water occurs in the northwest while the lowest quality occurs in the south of aquifer. To calculate GWQI index, each map was difference-normalized and converted to a rank map. Assuming the mean value of each rank map to be the weight of corresponding parameter, a GWQI map was created with values varying from 0 (lowest) to 99 (highest quality). Mean GWQI of 84 indicates a relatively good drinking quality of water in the aquifer. However, based on the GWQI map the quality of water declines from very good (GWQI=87) in northwest to a lower quality (GWQI= 80) in southern part of the aquifer. The lower quality of water in the southern part may have been caused by industrial activities, intensive animal husbandry, presence of wastewater plant, irrigation with treated municipal effluent and also by the inward hydraulic gradient. Map removal sensitivity analysis indicated that TSS and to some extent Na+ were important water parameters in this aquifer, which must be monitored with greater accuracy and frequency.

Evaluation of hydrologic behaviour and soil erosion as an environmental crisis is important in order to maintain watershed ecological safety at optimum level. The aim of this study is to evaluate the performance of the distributed hydrological WetSpa model in simulating erosion and sediment transport and also sedigraph in Taleghan watershed, Iran. Base digital maps and daily meteorological time series data for 9 years are the major model inputs. The calibration of global parameters was done for the first 5 years and the model validation was carried out for 4 years considering three month warm-up period at the beginning of both calibration and validation periods. The Nash-Sutcliffe criterion for the calibration and validation periods pointed out the efficiency of model simulation (82.7% and 79%, respectively). The next phase, the erosion module was calibrated for erosion and sediment transport simulation. The results showed the Nash-Sutcliffe efficiency criterion (60% and 64% for suspended sediment concentration and transport, respectively). Overall, the evaluation results reveal the good ability of WetSpa model in simulation of the hydrological processes e.g., runoff, raindrop detachment, runoff detachment, net soil loss, etc., in a given time and space.

In order to study the effect of depth of drip placement in soil in subsurface drip irrigation, and fertilization time during irrigation events, on tuber yield of potato, an experiment was carried out in Jiroft area in 1389. This experiment was in a completely randomized block design with four replications, with depth placement of drip tape as the main plot, and fertilization time as the sub-plot. Results showed that depth placement of drip tape had a significant effect on tuber yield, plant height, number of stems, stem diameter and dry plant weight at 1% level, number of tubers in plant, and wet plant weight and stolen height at 5% level. Fertilization time had a significant effect on tuber yield, stem diameter, stem number in plant, and plant height at 1% level and on dry plant weight and plant tuber number at 5% level. But, it did not show any significant effect on other attributes. Also, interactional effects of treatments were significant on tuber yield per plant, stem diameter, plant height, and number of tubers at 1% level, and on dry plant weight at 5% level, but the effect on other traits was not significant. According to the statistical results, the highest yield was obtained from the depth of 15 cm and middle time of fertilization.

Modeling of flow and transport processes in variably saturated porous media requires detailed knowledge of the soil hydraulic properties. The hydraulic properties to be determined by the inverse problem solution are the unsaturated hydraulic conductivity K(h) and the water retention curve θ(h). The inverse modeling approach assumes that both θ(h) and K(h) as well as transport parameters can be determined simultaneously from transient flow data by numerical inversion of the governing flow and transport equations. In order to find answers to the questions of uniqueness, identifiability and stability of different experimental setups, a new numerical experiment of redistribution was carried out. To study the shape of the objective function near its minimum, response surfaces for the estimated parameters were generated. The sensitivity of model outputs with respect to changes in input parameters was also computed and analyzed. Results of the redistribution experiment suggest that the non-uniqueness increases when the model output variables are not sensitive enough to the optimized parameters. As expected, the estimated values of parameters were sensitive to the magnitude of error in the measured data. In this experiment, the parameter estimation based on the pressure head observations provides unique solution. Due to preferential flow in the sample, tensiometric observations may provide poor results for inverse problem solution. Taking into account information about saturated hydraulic conductivity, Ks improved the likelihood of uniqueness and reduced the errors in parameter estimation of the shape parameters (α, n). It was found that the sensitivity analysis could be a useful tool to design the optimal time and location distribution of experimental observations.

Limitation of available water resources and crisis of water scarcity has been discussed in water conferences since a long time ago. In Iran’s climatic conditions, the most important problem for increasing agricultural production is limitation of available water resources. Drip irrigation methods are one of the suitable solutions for efficient use of water resources under a condition that selection, design, implementation and operation of drip irrigation systems would perform precisely. In this study, potential and suitability of drip irrigation systems in South Khorasan province was analyzed according to climatic conditions, quality of groundwater resources, topographical status and soil profile areas. To do this, all the effective parameters in drip irrigation are zonated and classified using software Arc GIS 9.3 and then using computational average method in AHP they are turned into a map to find suitable places for drip irrigation in the province. According to the study, about 50 percent of the land in South Khorasan province has the ability to use the drip irrigation system. The remaining 50 percent can also be used for drip systems if improved, with the exception of 9 plains. However, the performed drip irrigation plans are rare in this province and there should be more efforts to inform farmers to develop such systems in this province.

This study was done to compare K+ and NH4+ fixation in different agricultural systems in Khuzestan province. Soil samples were collected from Shushtar and Abadan. Samples were collected from depths of 0-30 and 30-60 cm in sugarcane, multi cropping, palm and uncultivated land. Then, 0-50-100-200-400-600-800-1000 mg kg-1 K+ or NH4+ concentrations were added to 0.5 gram of clay separated from these soil samples. These clay samples were kept for 24 h at room temperature. Then, they were extracted with 0.5 M magnesium acetate, and K+ and NH4+ were determined by flame photometer and micro diffusion methods, respectively. Fixed K+ or NH4+ was determined from added and extracted cations. Also, XRD studies were done in some samples. Kaolinite, palygoreskite, illite, chlorite, smectite and quartz were identified by XJRD. Statistical analysis showed that K+ or NH4+ fixation and rate were increased by increasing the concentration. Maximum K+ or NH4+ were fixed in surface layer’s clay in Shushtar multi cropping and Abadan Palm cultivation. The results showed that K+ and NH4+ fixation were increased by increasing the concentration. But, under increasing concentration for a cation, fixation decreased for others and vice versa. NH4+ fixation was more than K+. This may be due to smectite clay mineral in these samples. Smectite group tend to cause NH4+ fixation more than K+. These results can be applied for K+ or NH4+ fertilizers management.

Advance velocity is an important factor in surface irrigation system design and simulation. Volume balance is a simple model based on continuity equation used in surface irrigation design and management. In the past volume balance models, it is generally assumed that the upstream depth of surface water is constant and equal to normal depth. This initial assumption may cause significant errors in computing advance flow. In this paper, a modified volume balance (MVB) model is developed to predict the advance curve in furrow irrigation. In the suggested method the upstream surface, water depth is actual depth and variable in time. Predicted advance distance of VB, VB-ZI and MVB was compared to the observed data obtained for the three furrow lengths of 60, 80 and 90m. Evaluation indexes indicated that the modified volume balance equation is more accurate than the previous equations by RMSE 9.26, 7.37 and 6.76 respectively. Sensitivity analysis showed that the inlet discharge has the greatest effect on the model and the model is more sensitive to decreasing the discharge amount than to increasing it.