Journal of Water and Soil Science

Study the Performance of Hybrid Constructed Wetland with Pumice Substrate and Vetiver Plants in Urban Wastewater Treatment

J. Abedi-Koupai

One of the ways to reduce the amount of wastewater pollution is the use of constructed wetlands. In this research, the performance of a hybrid constructed wetland with pumice ore and vetiver plant on urban wastewater has been investigated. Hybrid wetlands with these specifications were constructed in the vicinity of wastewater treatment at the Isfahan University of Technology. To evaluate the performance of constructed wetland the effects of three and six days of retention time on the removal efficiency were studied using a completely randomized design. On average, for three days of retention time, in the wetland with the vertical flow, the horizontal flow, and hybrid wetland, fecal coliform was 47.4, 98.3, and 99.1 percent, BOD₅ was 7.6, 20.9, and 26.9 percent, and the COD was 4.6, 40.0, and 42.7 percent decreased, respectively. Also, during the six days of retention time in the wetland with the vertical flow, the horizontal flow, and hybrid wetland, fecal coliform was 61.6, 99.3, and 99.8 percent, BOD₅ was 10.7, 29.9, and 37.4 percent, and COD was 16.0, 86.8, and 88.9 percent decreased, respectively. The combination of Pumice as a porous material with the ability to absorb the elements as well as vetiver as a plant capable of phytoremediation indicated a very suitable performance during low retention time.

The Conversion of Inorganic Phosphorus Fractions, Phosphatase Activity, and Some Biological Properties in Sandy Soil Enriched with Minerals, Organic Matter, and Microbial Modifiers under Two Months of Incubation

R. Zalaghi

This study investigated the effect of the inoculation of the soil with some phosphorus solubilizing microorganisms (PSM) on inorganic P fractions in sandy soil enriched with inorganic and organic amendments. A factorial experiment arrangement was performed in a completely randomized design with three replications, using two factors: microorganisms (control, Entrobacter cloacae, Brevundimonas, and piriformospora indica) and amendments (control, (5%) apatite, (5%) apatite + (3%) zeolite, (5%) apatite + (1%) molasses). A 60-days incubation was performed after the application of treatments. Inorganic P fractionation and alkaline phosphatase activity of soil were measured at the end of the experiment. Phosphorus distribution in soil was as follow: octacalcium phosphate > apatite P > dicalcium phosphate > Olsen p > aluminium phosphate > iron phosphate. The application of apatite increased all of the P mineral fractions. The application of zeolite-appatie was very effective and although did not increase Olsen P (probably because of the low cation exchange capacity of soil), had a significant effect (p<0.05) on other P forms and caused dicalcium phosphate to increase (69.2%) and apatite P and octaclcium phosphate to decrease (34.8% and 60.0%, respectively) compared to apatite application. Application of molasses resulted in significant increases in dicalcium phosphate and octacalcium phosphate (48.9% and 29.3%, respectively) and decreases in apatite P and Olsen P (62.1% and 63.9%, respectively). Microbial inoculation resulted in a significant increase in Olsen P and dicalcium phosphate and a decrease in octacalcium phosphate and apatite P; showing the ability of these organisms to increase the phosphorus availability. Entrobacter and Piriformospora indica were more effective than Brevundimonas. It seems that microorganisms in different substrates had used different mechanisms; such that in apatite and apatite-molasses treatments microbial inoculation resulted in an increase in alkaline phosphatase activity, but in zeolite-apatite treatment, pH had decreased indicating the organic acid production by microorganisms.

Estimation of Short-Duration Rainfall Depth from Daily Rainfall Values Using a Single-Parameter Method

S. Farhadi

One of the important relationships which are used in the estimation of river discharges and floods is Intensity-Duration-Frequency (IDF). The accuracy of this relation is dependent on the accuracy of its parameters which need to be found based on short-duration rainfall depths (such as 15, 30, 60 minutes, and so on) for a long term (i. e. 30 consecutive years). Unfortunately, only 24-hour rainfall depths are available in many rainfall stations in Iran. Various empirical relations are available to convert 24-hour rainfall depth to sub-daily. One of these methods is IMD and its accuracy in some regions is low. In this research, the IMD method was transformed into a single-parameter equation and then, this parameter is evaluated for some rainfall stations in Iran. To do this, maximum 24, 12, 6, and 3-hour rainfall depths were extracted and their frequencies were calculated using Weibull and Gumbel methods. Regional coefficients in the modified IMD method were estimated using a linear regression method. Although the power of the IMD method is 0.33, results showed that this parameter for the rainfall stations ranged from 0.28 to 0.35. To make more comparison, the IDF relation of Kordan’s watershed was calculated using the short-duration rainfall depth which was estimated using the modified IMD, and then, this IDF was compared to observed data and Ghahraman’s relation which is commonly used in Iran. The comparison showed that the modified IMD relation could estimate the short-duration rainfall data better than Ghahraman’s relation. After calibration of the modified IMD relation for various regions in Iran, the sub-daily rainfall depth can be obtained with high accuracy.

Investigation of Wind Erosion Threshold in Different Land Cover and the Effect of Soil Properties on It (Case Study: Niatak Region of Sistan)

V. rahdari

Wind erosion is one of the most important natural processes in arid and semi-arid regions. Sistan plain has a hyper-arid climate and is one of the windy regions of the country. Due to the soil characteristics of the Sistan plain, wind erosion is very intense in this region. In this study, the relationships between some soil's physical and chemical properties and wind erosion were investigated in different land cover in a part of the central region of Sistan in 2018. A map of land cover in five classes was prepared using the results of field studies and the classification of satellite images. Fifty soil samples at a depth of 10 cm were collected to investigate the physical and chemical soil properties and the wind erosion threshold was determined at each location using a portable wind tunnel device. Also, the relationship between physical and chemical soil properties including soil texture, soil moisture, specific apparent weight, EC, SAR, ESP, Na⁺, k⁺, with the speed of wind erosion threshold was investigated. According to the results, the highest and the lowest threshold speed were 8.2 and 3.8 m s^-1 and occurred in agricultural lands and hilly lands, respectively. The results of this study indicated that the velocity of wind erosion threshold in different lands adjacent to sandy areas is less than the average of that cover. Also, the soil texture, EC, and SAR have the most significant effect on soil wind erodibility at P <0.05 in the study area.

Investigation of a Combined Physical Model of Water Extraction from Atmosphere in Different Atmospheric Conditions

M. Hesam

Due to many problems in the field of water supply, no study has been done on atmospheric water extraction devices. The objective of this research was to optimize the control parameters and the amounts of water produced from a physical model designed and built by the team including two-phase (refrigeration collector and sponge collector) in different atmospheric conditions were investigated. First, the effect of the sponge filter on the amount of water obtained, then the pilot in different weather conditions were studied to obtain optimal conditions. The suctions of 450 to 1400 rpm were applied at each humidity and temperature. In all the mentioned cases, the temperature of the device was studied at 2, 4, and 6 degrees below the dew point. Results showed that the sponge filter can increase the water produced by up to 15%. The first evaporator produced more water than the second evaporator. The optimal air suction speed inside the device depends on the relative humidity and temperature values. For the first and second evaporators, temperatures below 4 °C and 6 °C are optimal, respectively, and with increasing absolute humidity, the optimum suction speed increases. Parameters such as airflow velocity, number of collectors, temperature difference with dew point, and moisture absorption levels were influential in the amount of water produced. According to the qualitative study, the obtained water has a desirable quality for use in sensitive applications.

A Two-Level Optimization of the Manning Roughness Coefficient Method Based on the Modification of USDA-NRCS Method for Basin Irrigation Evaluation

B. Moravejalahkami

The current research was performed to present a quick and proper method for basin irrigation infiltration equation estimation by optimization of the Manning roughness coefficient. A two-level optimization of the Manning roughness coefficient method was presented by developing a zimod simulation model and initial intake families method, USDA-NRCS, (infiltration equation based on soil characteristics), and modified intake families (infiltration equation based on soil characteristics and inflow discharge). The investigation of the results of the model based on observed advance, recession, and surface storage showed the relative error of surface storage volume estimation was decreased by 38 to 50 % by adjusting the initial intake families method. The normalized root mean square error (NRMSE) of the advance estimation was between 0.22 to 0.85 for initial intake families and this parameter was between 0.09 to 0.5 for modified intake families. NRMSE of the recession estimation was between 0.13 to 0.75 for initial intake families and this parameter was between 0.09 to 0.19 for modified intake families. The presented method based on modified intake families increases the accuracy of infiltration estimation as compared to the initial intake families method and can evaluate basin irrigation acceptably. In addition, this method needs less time for basin irrigation evaluation as compared to the complete methods of optimization of infiltration parameters and roughness coefficient.

Effect of Angle, Height of Support and Pipe Line Diameter Size on Scour Hole

M. Saneie

Scouring holes under the oil, gas, and water pipelines threaten their stability by bending and demolishing. This phenomenon can cause damage to the environment and the oil and gas industry. The present study investigated the effect of the pipe diameter, the height of support, and the angle of the pipeline with flow direction by applying the experimental aspects to the cohesive sediments. The experiments were carried out by considering three angles of deviation as zero,15, and 30 degree based on the flow direction. Three opening gaps were considered through the experiments based on the pipe height as 0, D/2, and D/4 from the sand bed. Furthermore, three pipe diameters were employed to investigate the effect of diameter size. The results indicated that by increasing the angle of deviation, the height of scour hole decreased significantly, however, the raising the opening gap between pipe and bed increased the sediment deposition and it causes the height of scour hole is decreased consequently which was constituted approximately 18 percent. Moreover, the pipe diameter affects the scour hole formation and its effect on a downward jet and horseshoe vortexes and the result indicate by increasing the piper diameter the scour hole is increased based on its effect on the flow configuration. Finally, based on the experimental data, an equation was estimated to predict the scour depth by employing the non-linear regression technique.

Investigation of Integrated Modeling of Surface Water- Ground Water Using SWAT- MODFLOW Model

Hossein Ansari

Hydrological models are useful tools in water resources planning, but some of them do not have satisfactory performance on a regional scale. Hydrological models are appropriate for a specific spatial scale and the lack of input data is a limiting factor in the modeling. One way to overcome this limitation is by using a flexible comprehensive model in different watersheds. Since surface and ground water have dynamic interaction in environmental ecosystems and form a combined water resources system so, the application of two general methods including fully integrated and coupled regions has been evaluated in this research. An investigation of these methods showed that the major focus in most studies is on increasing the accuracy of recharge and evapotranspiration rates in simulation. The results showed that the simultaneous use of SWAT and MODFLOW models to understand the hydrological conditions in a region has been able to cover the defects associated with the semi-distributional and distributive constraints of two models, simulating the surface-groundwater and the interaction between the aquifer and river. This method can provide useful information about the water balance of the basin and help to plan water resources more accurately

Chaotic Study and Reconstruction of the Dynamic Phase Space of Evaporation Using Chaos Theory (Case Study: Semnan Synoptic Station)

M.R. Yazdani

Investigating the behavior of water surface evaporation is one of the basic issues in design, operation, and studies related to water engineering. Therefore, the application of new methods such as chaos theory in hydrology and water resources has recently been considered due to its innovation and capabilities. Since the fluctuations of evaporation from free water surfaces are dynamic and non-linear in nature, the aim of this study was to investigate the possibility of chaotic behavior in evaporation from the free water surface in the Semnan synoptic station on daily and monthly time scales in 1995-2018 using the concepts of chaos theory. The daily, monthly, and annual evaporation rates of this synoptic station were calculated to be 68.8, 200, and 2600 mm, respectively. To reconstruct the state space, two parameters of delay time and embedding dimension are needed. The mean of mutual information and false nearest neighborhood has been used to estimate these two parameters. The first step to study a process with chaos theory is to investigate the chaotic nature of the correlation dimension method as one of the most common methods. First, the embedded dimension was calculated by the nearest neighborhood method equal to 3. To calculate the delay time, cross-evaporation diagrams were drawn at Semnan station at different time scales. According to this method, the first local minimum in the diagram is considered the latency, which was obtained for evaporation at daily and monthly scales of 30 and 3, respectively. Unlike complicated and conventional computational methods, these results are obtained by observation and in the least amount of time, as follows: monthly data are more chaotic than daily data. The enclosed dimension and the slope of the correlation dimension diagram were obtained at 8.8 and 9.8, respectively, after calculating the latency and reconstruction of the state space.

Investigation the Effect of Irrigation Levels on Peppermint Yield and Water Productivity under Salinity Stress

H. Banejad

This research was conducted to study the effect of deficit irrigation and saline water on yield and yield components of Peppermint in the experimental research greenhouse of Ferdowsi University of Mashhad from 2018 to 2019. This research was performed as a factorial experiment based on the randomized complete design with three replications. In this research, irrigation levels consist of 4 levels (100 (I1), 80 (I2), 70 (I3), and 55 (I4) percent of FC) and saline water factors consist of 4 levels (0.9 (EC1), 1.9 (EC2), 2.5 (EC3), and 3.4 dSm^-1 (EC4)). The result showed that a decrease of the water to 15, 30, and 45 percent have resulted in the reduction of shoot fresh weights (to 15.8, 28.4, and 30.1 percent), shoot dry weights (to 7.1, 11.5, and 11.5 percent), and root dry weights (to 4.6, 9.2, and 9.2 percent), respectively. Also, results showed that irrigation with EC2, EC3, and EC4 has resulted in a decrease in shoot fresh weights (to 12.7, 28.5, and 34.0 percent), shoot dry weights (to 3.6, 11.6, and 11.6 percent), and root dry weights (to 6.7, 12.4, and 14.6 percent), respectively. The result indicated that interaction effects of salinity and water stress decreased peppermint water productivity, as the highest and lowest peppermint water productivity with 3.54 and 2.06 Kgm-3 were in the EC1I4 and EC3I1 treatments, respectively. Results revoluted that maximum dry yield and peppermint water productivity were in the EC1I4, so this treatment was recommended for irrigation of peppermint.

Optimal Location of Flood Dispersion Using Quantitative Fundamental Models in Fuzzy Logic (Case Study: Gorbayegan Watershed)

M. Nohtani

The basis of land management is the geomorphological zoning of the land surface, which is determined based on the same geomorphological characteristics of the zoning. Ground zoning detect land features by basic surface features such as height, slope, and slope direction. In this study, quantitative zoning of the land surface with small coefficients to the surface has been used to identify suitable areas for artificial feeding in the mountainous region of Gohar and Dasht-e Gorbayegan in Fars province. Quantitative zoning of the land surface has been performed by Evans-Shri coefficients due to the accurate determination and separation of types, faces, and surface features of the land has an important role in determining the exact land use. In this research basic models included linear, circular, and divergent models. These basic models with the dimensions of the final windows are ranked second in the MATLAB software to the level the ground is fitted to determine the fit of these models, the parameter of total squared difference has been used. In addition, the suitability of the study area for flood distribution in five different classes was determined using fuzzy logic. The most suitable areas for feeding downstream of the cones had five parameters with a maximum score of 20. The inappropriate class related to the lower plains of alluvial fans have a minimum score of five input classes in fuzzy logic, which is equal to zero.

Simulation and Optimization of Profitability of Jofeyr (Isargaran) Irrigation and Drainage Network Products Using System Dynamics Approach

H. Nozari

In the present study, a model was developed using a system dynamics approach to simulate and optimize the profitability of crops of the Jofeyr (Isargaran) Irrigation and Drainage Network located in Khuzestan Province. To validate the results, the statistical indicators of root mean square error (RMSE), standard error (SE), mean biased error (MBE), and determination coefficient (R²) were used. To validate the simulation results of the benefit-cost ratio, the values of these indicators were obtained 0.25, 0.19, 0.005, and 0.96, respectively. Then, to determine the optimal cultivated area of the network and increase the profitability, the cropping pattern was determined both non-stepwise and stepwise in 2013 to 2017 cropping years. In the non-stepwise, the cultivated area of each crop changed from zero to 2 times of current situation. In stepwise, due to social and cultural conditions of inhabitants, this change was slow and 10% of the current situation every year. The analysis of the results showed the success of the model in optimizing and achieving the desired goals and the total benefit-cost ratio increased in all years both non-stepwise and stepwise. For example, in 2017 compared to 2016, production costs decreased by 7.1 percent and sales prices increased by 5.8 percent, and increased the benefit-cost in 2017 compared to the previous year. The results showed that the present model has good accuracy in simulating and optimizing the irrigation network, its cropping pattern, and defining other scenarios.

Responses of Some Soil Bioindicators to the Interaction Between Sugarcane Bagasse Biochar and Salinity Stress in a Cadmium-Polluted Soil

N. Azadi

Biochar as an efficient strategy for the improvement of soil properties and organic waste management may reduce the potential effects of abiotic stresses and increase soil fertility. However, the effects of this organic amendment on soil microbial indicators under combined salinity and pollution have not been studied yet. Therefore, the objective of this study was to evaluate the influence of sugarcane bagasse biochar on some soil bioindicators in a Cd-polluted soil under saline and non-saline conditions. A factorial experiment was carried out with two factors, including NaCl salinity (control, 20 and 40 mM NaCl) and sugarcane bagasse biochar (soils unamended with biochar, amended with uncharred bagasse, 400 ^oC biochar, and 600 ^oC) at 1% (w/w) using a completely randomized design. Results showed that salinity increased the mobility of Cd (12-17%), and subsequently augmented its toxicity to soil microorganisms as indicated by significant decreases in the abundance and activities of the soil microbial community. Conversely, sugarcane bagasse biochar application reduced the concentration of soil available Cd (14-18%), increased the contents of soil organic carbon (89-127%), and dissolved organic carbon (4-70%), and consequently alleviated the effect of both abiotic stresses on soil microbial community and enzyme activity. In conclusion, this experiment demonstrated that the application of sugarcane bagasse biochar could reduce the salinity-induced increases in available Cd and mitigate the interaction between salinity and Cd pollution on the measured soil bioindicators.

Cavitation Risk through the Bottom Outlet of the Dam Using Numerical Solution of Ansys Model

A. Khosrojerdi

Abstract
The objective of the present research was to investigate the flow properties through the bottom outlet of the Nesa dam based on numerical and experimental studies. 22 piezometers were employed to measure the static pressure through the experimental model. The bottom outlet section was divided into three blocks to measure the endangered region. The graph of cavitation numbers was plotted for different flow discharge and cavitation damage levels to compare with a safe zone to find out the areas with a high risk of cavitation. The results illustrate that block No. 1 cavitation index is located at the “possible cavitation” damage. The studies showed that the cavitation index is the dependent parameter with the height of the water at the upstream reservoir. Furthermore, for block No. 2, the level of cavitation ranged from x/L = 0.44 to 0.90 and the cavitation level is related to the velocity, and by increasing the velocity to 16 m/s, the threat of the cavitation and its consequences is raised, dramatically. Regarding block No.2 and 3, the cavitation through this block depends on the negative pressure since the negative values of the cavitation index is related to the negative static pressure and it is assumed that the negative pressure can reach the threat of major damage. Also, a comparison between different numerical turbulence models illustrates that the k-ε RNG with fine mesh showed less error with experimental values which causing the numerical model with this condition to reach an appropriate agreement between numerical and experimental simulations.

Effect of Different Levels of Tape Irrigation on Yield and Water Productivity of Tropical Alfalfa Cultivars

A. asareh

The present research was conducted to determine water stress tolerance and water productivity (WP) of 5 alfalfa cultivars as a split-plot design in a randomized complete block with 3 replications in the Safiabad Agriculture and Natural Resources Research Center (SARRC) with Silty clay loam soil texture during 2018-2019. The main plot was 4 levels of water irrigation depth (including 25, 50, 75, and 100% water requirement supply) with a constant irrigation cycle and the sub-plot was the five alfalfa cultivars (Baghdadi, Yazdi, Nikshahree, Omid, and Mesasirsa). Two-year data on forage yield and WP for six harvests (from June to November) were analyzed by SAS software. The results showed that the wet and dry forage yield decreased by applying water stress and the percentage of dry forage increased. The highest yield of dry matter (12.4 tons ha^-1) and WP of dry forage (0.94 kg m^-3) were obtained from 75% water requirement supply treatment. Baghdadi genotype with wet and dry forage yield 39.1 and 10.7 tons ha^-1, respectively, and the WP of dry forage 0.9 kg m^-3washigher than other genotypes. However, the Yazdi genotype had the lowest yield of wet and dry forage (30.3 and 8.5 tons ha^-1, respectively) and dry forage WP (0.75 kg m^-3). Therefore, the Baghdadi genotype with a 75% water requirement supply is recommended for similar conditions to the climate of Northern Khuzestan to increase water productivity.

Study of the Effect of Crossover Structures and Roughness Coefficient on Depth and Flood Plain of the Urban Watercourses (Case Study: Zarkesh Watercourse, Mashhad)

A. Mosaedi

In recent decades, population growth, urban sprawl, urban environmental changes, and related issues are one of the significant issues in proper planning to manage the urban environment. One of the issues in urban development is the occurrence of floods and flooding due to heavy rains. In this research, flood modeling was studied in Mashhad Zarkash watercourses. The amount of rainfall for the return period of 10, 25, 50, 100, and 200 years were extracted by CumFreq software using the maximum 24-hour rainfall statistics of three rain gauge stations closer to the Zarkesh, Jagharq, Sar-e-Asyab, and Torqabeh watercourses basins during the statistical years 1364 to 1390. The peak discharge was calculated using the US Soil Protection Organization (SCS) rainfall-runoff method. Zarkesh watercourse is located on the outskirts of Mashhad. River and flood flow modeling was performed using Arc GIS, HEC-GEORAS, and HEC-RAS software in two conditions including structure (bridge) and no structure. Due to urban marginalization, urban development and land use change have greatly expanded in this region. The results of flood simulation showed that flood levels with a return period of 50 years increased by 50000 m² equal to 22% in the presence of a structure compared to the state without a structure. The results of this research show that the construction of bridges on the river, the roughness coefficient by land use change, and the number of curves due to land permeability changes are effective in the flood zone.

Heavy Metals Pollution Assessment in Groundwater Resources of Hamadan-Bahar Plain in 2018

M. Cheraghi

The qualitative assessment of groundwater resources as the most important sources of drinking and agricultural water is very important. Therefore, the present study was conducted to evaluate the quality of heavy metals in groundwater resources of the Hamadan-Bahar plain in 2018 using water quality indices. In so doing, a total of 120 groundwater samples were collected from 20 stations during the spring and summer seasons and the values of physico-chemical parameters were determined based on the standard methods and also the content of heavy metals was determined using inductively coupled plasma spectroscopy (ICP). The results showed that the mean concentrations of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn (µg /L) in the samples in the spring season were 5.08, 0.260, 1.05, 2.70, 1.50, 0.490, 1.50, 7.48, and 1.75, respectively, and in the summer season were 20.7, 0.220, 0.950, 7.12, 1.34, 0.490, 1.29, 8.23, and 2.08, respectively and except for As in the summer season, the mean content of other elements was lower than maximum permissible limits established by WHO for drinking water. Meanwhile, the mean values of C_d, HPI, HEI, MI, and PoS indices in the spring season with -7.51, 9.91, 1.42, 1.42, and 328, respectively, indicate the water quality was categorized as low, low, low, low and moderately affected and in the summer season with -5.90, 10.0, 3.04, 3.04, and 673, respectively, were categorized as low, low, low, moderately affected, and high pollution. Due to the extensive use of agricultural inputs, especially chemical and organic fertilizers and chemical pesticides containing heavy metals by farmers in the study area, the possibility of increasing the concentration of heavy metals in the soil and their penetration into groundwater aquifers will not be unexpected in the medium term. Therefore, periodic monitoring in groundwater resources of the study area is recommended.

The Effect of Manure and Compost on Soil Chemical Properties and Availability of Exchange Cations in a Saline Sodic Soil

E. sabbagh tazeh

The utilization of organic amendments in the reclamation of saline-sodic soils can reduce the necessity for the application of chemical Ca⁺² sources. In this research, soil leaching experiments were conducted in CRD as split factorial. The main factors were 1) amendment type including manure and compost, 2) amendment rate including 1, 3, and 5 percentage w/w, and 3) leaching stage with 5 levels including without leaching, once, twice, three times, and four times leaching, every time with one pore volume and with 30 days’ intervals. All columns were incubated for 30 days after the addition of amendments and then were leached. The parameters in each column were studied in three depths as a subplot. After 120 days, EC and ESP of soils amended with both types of conditioners reduced under 5 dS m^-1 and 15%, respectively. After 150 days, the exchangeable K and Mg were reduced by both conditioners. Exchangeable Ca increased significantly in both amendments at the end of the 5th month. The efficiency of 1% by weight of two conditioners in improving the salinity and sodicity characteristics of soils was the same as other rates. There was not a significant difference between leaching by 3 and 4 pore volume in both conditioners in the most of parameters. In leaching treatment with three pore volumes using 1 percentage w/w of manure and compost, soil EC decreased by 80% and 71% and soil ESP by 44.5% and 35%, respectively.

Investigation of Salt Concentration Fluctuations of Paddy Fields in Underground Drainage Conditions and Application of Applied Management Scenarios Using Drainmod-S Model

M. Pourgholam-Amiji

In this study, the Drainmod-S model was used to vary soil salt concentration and the effect of underground drainage on the amount of leaching in a physical model (large lysimeter). A soil extractor was installed at depths of 40, 50, and 70 cm at a distance of 35 cm from the drainage to measure the salinity of the soil solution. In this study, three scenarios were applied including salinity profiles under conventional conditions (mid-season and end-season drainage), soil salinity profiles under different drainage conditions, and prior scenarios with saline irrigation. The second and third scenarios were applied in four drainage stages, respectively. These stages include transplanting and mid-season drainage (days 15 to 20), mid-season drainage (days 35 to 40), mid-season and end-season drainage (days 55 to 60), and end-season drainage (days 75 to 80). The results showed that after simulating the total solute concentration overtime at a depth of 40 cm and comparing it with the measured values, the coefficient of determination (R²) was 0.77 indicating an acceptable Drainmod-S model simulation. This parameter for simulating solute concentration at 50 and 70 cm depth was 0.76 and 0.75, respectively. The mean absolute error parameter (MAE) value was also negligible.

Effects of Vegetation Type and Slope on Cl- and K+ Transport in Runoff and Drainage of a Clay Loam Soil

A. Safadoust

This study was conducted to investigate the effects of vegetation type (Alfalfa and Wheat) and slope (5% and 20%) on runoff and drainage pollution in clay loam soil. Sampled soils were repacked in the box with one soil drainage outlet and one surface flow outlet and were cultivated by wheat or alfalfa. A solution containing 0.05 M KCl was poured quickly and uniformly, over the surface of each box, after plant growth. Simulated rainfall was applied to the soil box with the intensity of a constant rate of 64 mm h-1 for 2 hours immediately. Then the concentration of Cl- and K+ were measured in the collected samples of runoff and the drainage outlet. Results showed that the measured concentration of K⁺ was lower than the Cl^-concentration as a result of its absorbable property. The breakthrough curves (BTCs) of Cl^- and K⁺showed that slope and vegetation type affected the transport of Cl^- and K⁺. The peak of the BTCs for Cl- and K⁺ in runoff ranked in the order of wheat and 20% slope> alfalfa and 20% slope> wheat and 5% slope> alfalfa and 5% slope, and in the drainage changed to alfalfa and 5% slope> wheat and 5% slope> alfalfa and 20% slope> wheat and 20% slope. For each slope, the intensive vegetation cover of alfalfa than wheat considerably reduces Cl^- or K⁺ pollution in runoff; whereas drainage development of larger and deeper root systems was the cause of higher leached concentrations for both tracers. Based on our research changes in soil surface vegetation cover from wheat to alfalfa are suggested in slope land to prevent surface water pollution; although other factors such as the climate, soil texture, and structure should also be considered.