maryam varavipour

The aim of the research is quantitative modeling of the underground water flow of the plain aquifer and the investigation of management solutions to deal with the drop in the underground water level. This research was investigated using hydrogeological information, hydrology, meteorology and basic studies of underground water sources. Quantitative underground water modeling was done using GMS software and Modflow code and the underground water level was simulated for the years 2011-2015 with 60 monthly time steps. Manual calibration of the model was done for 2011-2014 and its validation was done for 2014-2015. Future management solutions, in the form of combined scenarios:One- 10% reduction in withdrawal from wells with a 5% reduction in feeding from return of agricultural water. Two- 20% reduction in withdrawal from wells with a 10% reduction in feeding from return of agricultural water. Three- Their comparison with the continuation of the existing trend was predicted for the years 2015-2019. The result of the aquifer modeling for the above time periods showed the deficit of the reservoir 33.09 MCM. But by applying a 10% reduction in withdrawal and a 5% reduction in feeding, 21.38 MCM/year and by applying a 20% reduction in recharging from the return flows of agricultural consumption and 10% reduction in feeding, 25.94 MCM/year were added to the volume of the water balance. But with the continuation of the current trend, the deficit volume of the aquifer was estimated to be more than 54 MCM.

In this study, the performance of a Proportional-Integral (PI) automatic control system for the operation of the main channel of the northern branch of the Abshar irrigation network was evaluated under low-water operation scenarios. The actions taken to achieve the research objectives included:1) Development of a hydraulic flow simulation model in the main channel of the Abshar irrigation network using a simplified Integral-Delay (ID) mathematical model. 2) Development of a decentralized PI automatic control operation model. 3) Coupling the automatic operation control model with the hydraulic simulation model in MATLAB and determining the proportional and integral coefficients of each controller using system identification methods. 4) Simulation of the operation status using the designed automatic system under normal, low-water, and severe low-water operation scenarios with input fluctuations. The simulation results demonstrated that the controller had acceptable capability in implementing desirable operation under normal operation scenarios, with performance evaluation indices MAE, IAE, and STE fluctuating within the ranges of 0.11 to 0.140, 0.0013 to 0.0182, and 0.0001 to 0.0011, respectively. With the emergence of low-water scenarios and their intensification, water distribution conditions were assessed as desirable in upstream intakes but uncertain in downstream intakes. The calculated maximum error values in the lower intervals ranged from -10 to -20 and -35 to -45 centimeters, respectively. The results showed that the controller transferred the effects of low-water conditions and inflow fluctuations downstream, resulting in desirable surface water distribution for upstream intakes but inappropriate distribution for downstream intakes.

This research assesses and investigates the impact of automating the Abshar irrigation network's main canal using a decentralized control system on the adequacy and stability of surface water distribution. To achieve this, the study analyzes 30 years of historical discharge data at the Abshar diversion dam and selects seven representative operational scenarios. It then employs the Integral-Delay (ID) hydraulic simulation model to simulate surface water distribution in the main canal under each scenario (a total of 540 simulations). These simulations are compared with results obtained using a simplified Integral-Delay (ID) mathematical model. Additionally, the research develops a decentralized PI automatic control system model for the network. This control system model is then integrated with the Integral-Delay (ID) hydraulic simulation model within the MATLAB environment. By utilizing system identification techniques, the study determines the proportional and integral gains for each controller in the control system. Finally, the performance of the automated control system is evaluated by analyzing the simulated surface water distribution results for the chosen scenarios using performance indices related to water distribution adequacy and stability. This allows for a comparison of the automated control system's effectiveness with the pre-automation scenario.

This study aimed to evaluate the environmental and economic effects of the development of mini-bubbler pressurized irrigation projects as a modern irrigation system in Birjand County, South Khorasan Province, from the perspective of farmers and users, so the quantitative and qualitative processes of these irrigation projects can be evaluated. Data collection was conducted with a survey technique and the results showed that most of the farmers had a favorable assessment of the environmental and economic effects of the plan. The economic factor was found to be the most important factor during the evaluations, which included the variables of reducing the time required for irrigation, increasing the amount of production per hectare, increasing the cultivated area, reducing labor costs, reducing water and irrigation costs, improving the quality of products, and increasing the income from agriculture, which explained ca. 26.2 percent of the total variance. The second factor was the environmental factor, which includes the variables of the more appropriate use of fertilizers and pesticides, reduction of plant diseases, reduction of weeds, and prevention of soil salinization, which explains 21.6 percent of the total variance. Also, the effects of mini-bubbler irrigation on agricultural inputs were also evaluated, which included the variables of less water consumption, less seed consumption per hectare, compliance with the cultivation pattern, and increasing the mechanization factor, and explained 17.8 percent of the total variance. The social factor also includes the variables of gaining social credit, the cooperation of users in maintaining the system, and observing the irrigation schedule, and it explains 11.2 percent of the total variance. Finally, based on the obtained results, suggestions have been made for the success of implementing and using such projects.

With the influx of agricultural, industrial and hospital pollutants into surface and groundwater, human health and other living organisms are facing a serious threat. Zarjoub River is one of the most polluted rivers in the country, which passes through the center of Rasht and all kinds of dangerous pollutants such as nitrate, phosphate and dangerous heavy metals flow into it. Artificial wetlands are one of the low-cost and environmentally friendly wastewater treatment methods that have received a lot of attention today. In this study, the use of artificial wetlands in sequential using three different plant species of phragmites, lemna and vetiver with two different arrangements to remove nitrate in autumn of 2019 and summer of 2020 has been investigated. The results showed that the average percentage of nitrate reduction by two plant treatments was 73% and 68%, and for the control treatment it was 35%, which indicates the effect of plants in wetlands. Also, the result showed that the amount of nitrate reduction from the effluent was directly related to temperature changes and growth status of plants. The results showed that the use of hybrid wetlands can have a good removal efficiency for pollutants compared to their individual use, but the difference in plant arrangement in wetlands, although statistically significant at a probability level of 1%, had little effect on the nitrate removal process on effluent.

Water crisis is one of the most important problems in arid and semi-arid areas such as Iran. Also, in these areas indiscriminate use of nitrogen fertilizer have had severe environmental consequences. Thus, assessment of plant responses to water stress, the amount of nitrogen and, estimation of production function for determining optimal use of water and fertilizer is inevitable. The objective of this study was to investigate the interrelations of yield, irrigation depth and, applied nitrogen fertilizer of Radish (Raphanus sativus L.). For this purpose, the study was conducted in the College of Aburaihan (Southeast Tehran, Pakdasht, Iran) in 2020. Experiment was arranged based on randomized complete block design with two treatments of nitrogen fertilizer and irrigation water depths with three replications. In this study the Levels of irrigation depth were 120% (I1), 100%(I2), 80%(I3) and 60%(I4) of irrigation requirement the levels of applied nitrogen fertilizer were 120%(N1), 100%(N2), 80%(N3) and, 60%(N4) of nitrogen use requirement. In this study four equations of of linear, Cobb-Douglas, quadratic and transcendental were used to determine the water-nitrogen production function production. The results showed that the quadratic equation simulates the dry yield of radish with a higher accuracy. The results showed also, the I3 (142 mm) and N2 nitrogen (150 Kg per hectare) treatments, were yielded the highest yield and irrigation water use efficiency.

Many ornamental plants have the ability to extract toxic metals from the soil and are able to store large amounts of metals in their organs with no health problems for humans as they do not enter the human food chain. This study aimed to investigate the effect of sewage sludge application on the performance of Helianthus annuus and to investigate its phytoremediation ability for heavy metals (Pb, Ni and Cd) in soil. This study was carried out with three levels of sewage sludge related to southern Tehran wastewater treatment plant, including 0, 10 and 20 percent by weight of soil in three replications in a completely randomized block design on Helianthus annuus. The results showed that the application of sewage sludge caused a significant increase in the concentration of heavy metals and wet and dry yield of different parts of the flower in the plant. Application of sewage sludge at 20 percent by weight of soil was more suitable for growth index and accumulation of heavy metals in plant in terms of growth index such as wet weight (root 12.03 g and shoot 48.56 g), dry weight (root 1.97 g and shoot 8.69 g), stem diameter (0.78 cm), stem height (19.4 cm) and flower diameter (7.44 cm) as well as concentration of heavy metals Pb (root and shoot 9.09 and 4.35 mg/kg respectively), Ni (root and shoot 3.65 and 2.04 mg/kg respectively) and Cd (root and shoot 0.598 and 0.364 mg/kg respectively). Due to root bioaccumulation factor above 1 and transfer factor less than 1, Helianthus annuus is a plant suitable for the uptake and transfer of heavy metals, which prevents the entry of heavy metals into the shoot parts by a plant stabilization mechanism.

Due to the population increase and growing need for food production development in cities and to improve urban agriculture through urban greenhouses, there is an urgent requirement to provide optimal subsurface irrigation methods. Optimal irrigation methods mean methods that reduce water consumption and allow the use of lower quality water for irrigation while maintaining product quality. There are different methods for subsurface irrigation in greenhouses, for example there are some hydroponic methods which need special equipment and many studies have been conducted on them. In this research, performance of a new sub-irrigated planter method (SIP) for panting basil plant in two seasons in a greenhouse, in term of water productivity was evaluated and compared with conventional surface irrigation.

In SIP system, plant was planted in pot and a water reservoir (saturated gravel reservoir) was prepaid below the growing medium in pot (bottom of pot) to provide the water for plants through capillary action in growing medium (upper part of pot). Variable parameters to study were: depth of growing medium (D1: 50 cm and D2: 30 cm), Type of growing medium: (clay loam + cocopeat + perlit (SC) and cocopeat + perlit (C)) and three irrigation salinity levels (1.2, 3.5 and 5 dS.m-1: basil tolerance to irrigation water salinity: 1.5 dS.m-1); which were compared in both SIP and surface systems.

All SIP-C treatments had considerably higher water productivity in 5% statistical level compared to surface treatments which proved the superiority of C growing medium to be used in SIP systems in order to increase water productivity in a greenhouse. Considering optimum depth, water productivity in SIP-SC-D1 was not meaningfully higher than SIP-SC-D2; although in SIP-C, all D2 treatments had considerably higher water productivities than D1s. As a result it is recommended to use lower depth of growing medium while using C growing medium in SIP systems. Increasing irrigation water salinity level did not affect the fresh yield weight in SIP systems; although the salinity level was remarkably high in surface layers of SIP pots unlike the higher salinity layers observed at bottom of surface pots; which shows the need to monitor the growing medium salinity levels during growing season and applying the leaching between growing seasons when necessary in SIP systems.

This study showed that sub-irrigated planter method while is a very simple method and has no need to complex technology and expensive equipment and installation, significantly reduces the amount of water required for irrigation and also is able to compete with conventional surface irrigation systems. Therefore this method can be used as conservative system to save both water and soil as an agricultural goal and keep the productivity in high levels.

Today, due to legal restrictions on the methods burying sewage sludge, environmentalists recommend using it as a fertilizer as a fertilizer in agriculture to get rid of the problems caused by sludge produced in treatment plants. Sewage sludge can be the best and cheapest organic fertilizer for agricultural lands due to its high content of organic compounds and nutrients required by the plant. But at the same time toxic factors such as heavy metals in sludge are the most important limiting factor for its use. The purpose of this study was to investigate the effect of sewage sludge application on some soil chemical properties and heavy soil metals. This study was carried out in the Aburaihan Campus Research Greenhouse of Tehran University with three levels of sewage sludge for anaerobic and dehydrated anaerobic wastewater treatment plant south of Tehran containing 0, 10 and 20 g/kg soil, in three replications in a completely randomized block design on Helianthus annuus. After finishing the growing season, the Soil of control and treated pots were sampled. After physical and chemical tests on soil samples, it was observed that application of sewage sludge in soil significantly increased Organic Matter (O.M), Cation Exchange Capacity (CEC), Salinity (EC), total nitrogen, potassium and Heavy metals Pb, Ni, Cd concentrations, and There was a significant decrease in pH in the treated soils compared to the control treatment. Also, treatment of 20 g of sewage sludge per kg soil had the best effect on soil chemical properties.

AquaCrop model simulates biomass yield under deficit irrigation management. This model developed by FAO and requires less input data than other similar models. One of the input data of this model is the normalized water productivity (wp*) that should be known for each plant. This parameter for the radish plant, which is part of the C3 plant, has not yet been determined. Therefore, the first objective of this study is to determine it for Pakdasht area and its second objective is to analyze the sensitivity of the Aquacrop model to the input data of reference evapotranspiration (ETo), Wp*, initial canopy cover (CCo) and maximum canopy cover(ccx). This research was carried out in the research center of Abourayhan Campus, University of Tehran in Pakdasht District during 2018 crop year. According to the results of this study, normalized water productivity of radish was determined to be 11.3 g / m2. The results of sensitivity analysis showed that the AquaCrop model has the most sensitivity to the normalized water productivity parameter for full irrigation conditions, in which the sensitivity coefficient was estimated to be 0.88. Under deficit condition, the model is most sensitive to the ETo parameter, and the less irrigation is more severe, the sensitivity coefficient increases. The sensitivity coefficient for 60% deficit irrigation was -10.99.

The purpose of this study was to investigate the effect of irrigation with urban treated wastewater on yield, yield components and water use efficiency of maize (Single cultivar 704) at the research field of Aburaihan Campus, University of Tehran in Pakdasht during the year of 2017. The experiment was carried out as split plots and based on the randomized completely block design with main factor (type of irrigation water) and sub factor (three levels of water requirement) with three replications. Type of Irrigation treatments included well water and treated wastewater that were used in three levels of water requirement including 100 (D1), 75 (D2) and 55 (D3) percent of maize water requirement. The results showed that the type of applied water caused a significant difference in dry matter, so that the highest yield (2090.18 kg/ha) was obtained in wastewater treatment and the lowest yield (17231/15 kg/ha) was obtained in well water treatment. In terms of different amounts of water, the highest water use efficiency based on dry matter (3.52 kg/m3) was obtained by D1 treatment (100%) and the lowest ones (3.46 and 3.44 kg/m3) were obtained by D2 (75%) and D3 (55%) treatments, respectively. Analysis of variance showed that irrigation with urban treated wastewater had a significant effect on dry matter yield, ear length and water use efficiency based on dry matter. Therefore, the refined wastewater at level of 75% water requirement can be suggested as a suitable irrigation practice for corn in Pakdasht area.

The normalized water productivity parameter is one of the AquaCrop model’s input, upon which the crop biomass yield is simulated on a daily basis. The necessitate of this research is that the amount of normalized water productivity for spinach has not been determined so far. This research was carried out at the Abourihan Campus farm of the University of Tehran which is located in Pakdasht. The experiments were performed during cultivation year of 2017-2018 with six planting densities of 12, 16, 17, 22, 25 and 33 plants per square meter and four replications with full irrigation. The biomass yield was measured seven times during the cultivation season. Considering the measured data of biomass and relative transpiration, the normalized water productivity was obtained for five treatments. The highest amount of normalized water productivity (12.4 g/m2) was related to 25 plants per square meter density. A relationship function was found using normalized water productivity and planting density data. This function was tested using the remaining treatment and placing the normalized water productivity in the Aqua Crop model. The mean root square error and the mean bias error between the measured and simulated data were 20.9 and 6.6 g/m2 at the test step. The results of this study showed that the planting density affects normalized water productivity and it is increased by increasing planting density (optimum density) and then it is decreased. Finally, this study suggests that the normalized water productivity regarding to planting density is entered to the AquaCrop model.

Water and nitrogen are two main factors of plant production. Water scarcity is one of the most important challenges in the production of agricultural products in arid and semi-arid regions, as in most parts of Iran. A great deal of research has been done on the interaction between water and nitrogen and has shown that irrigation and nitrogen treatments interact with the yield. So far, various models have been developed to simulate plant performance in response to different levels of water and nitrogen. The FAO organization has provided the AquaCrop model. This model simulates yield performance in response to water consumption. The effect of nitrogen deficiency on yield in the latest versions of the AquaCrop model (versions 4 and 5) is carried out using semi-quantitative method. In this method, nitrogen deficiency is assumed to be based on four parameters: 1- Normalized water productivity (WP*), 2- maximum canopy cover (CCx), 3- The Canopy growth coefficient (CGC) and 4- Canopy decline coefficient (CDC). The hypothesis of this research is that there is a relationship between the four above parameters and nitrogen fertilizer for corn, and from them, we can determine the values of four parameters for each fertilizer level and use them in the AquaCrop model. Therefore, the first goal of this study was to determine the equations between nitrogen fertilizer and the four above parameters. The second goal of this study was to evaluate the accuracy of the AquaCrop model for simulating the response of corn to nitrogen fertilizer using parameters derived from the equations defined in the first part.

Aqua solutions containing nitrogen as nitrate are considered to be one of the most important pollutants of surface water and underground water. Denitrification bioreactors would provide a carbon sourced environment. Passing drainage water through such bioreactors would result in an increase in denitrification level and also, an increase in nitrate elimination from the environment. Denitrification bioreactors provide a carbon sourced environment. Passing drainage water through such bioreactors results in an increase in denitrification level and nitrate elimination. In this study, biochar is used as carbon wall in bioreactors. At first, nitrate and ammonium elimination performance of biochar-filled bioreactors and wheat straw-filled bioreactors are compared to each other. Later, effect of height of bioreactor on concentration of output nitrate and ammonium is taken under study. Also, performance of bioreactors in nitrate and ammonium elimination is investigated in a four month time period. In order to perform this research, poly-ethylene bioreactors with height of 125 centimeters were used. Height factor is taken under study in four levels; H1= 32.5cm, H2=62.5cm, H3=92.5cm, and H4=125cm. Control bioreactors (B0) were filled with 30% wheat straw and sample bioreactors (B1) were filled with 30% Biochar of wheat straw. Results showed that output nitrate concentration of denitrification bioreactors significantly depends on biochar type. Output concentration of biochar-filled bioreactors (B1) were measured 18.16 mg/liter while the output nitrate concentration of wheat-straw filled bioreactors (B0) were 49.01 mg/liter. Also it has been shown that increasing bioreactor’s height would reduce output nitrate concentration in both bioreactors. After four month of sampling, output nitrate concentration from 160 mg/liter was reduced in different treatments; 20.91 mg/liter in H1B1, 12.85 in H1B2, 8.05 mg/liter in H3B1 and 5.23 in H4B1. Also in control treatments nitrate concentration was reduced to 42.17 mg/liter in H1B0, 36.36 mg/liter in H2B0, 28.99 mg/liter in H3B0 and 19.65 mg/liter in H4B0. Time also has a significant effect on nitrate elimination (P <0.01). after four month of experiment, average concentration of output nitrate in sample bioreactors reached the minimum 21.77 mg/liter, while it was measured 59.21 mg/liter on the first day of experiment. Concentration of output ammonium in both biochar-filled and wheat straw-filled bioreactors was increased comparing to concentration of input ammonium. It can be explained as some of the nitrate is dissimulate to ammonium by anaerobic bacteria. But this increase was less than 0.5 mg/liter, hence was negligible. performance of nitrate elimination in biochar-filled bioreactors is more than wheat-straw bioreactors. Also height increase in bioreactors would result in more nitrate elimination.

The nitrogen (N) consumption management during the plant growth season plays an important role in achieving maximum crop yield and reducing environmental hazards. Determination of N nutrition index (NNI) is one of the methods for diagnosing plant N status. The main objective of this study was to investigate the role of monitoring NNI in improving nitrogen consumption management. The field experiment was carried out during the growth period of summer maize in Pakdasht region, southeast of Tehran, in 2015 and 2016. Grain yield, dry matter and nitrogen concentration of crop samples from seven treatments including: 0 (N0), 50 (N1), 100 (N2), 150 (N3), 200 (N4), 250 (N5) and 300 kg N. ha-1 (N6) were measured during the growing season. The results showed that NNI monitoring during the growing season could show the variation of N status in different treatments. In addition, NNI was closer to one in the optimal treatment (N4), which produced maximum dry matter with less N application, as compared with other treatments. Moreover, the relative grain yield decreased with a constant rate whenever the NNI was less than one. Agronomy and recycling efficiencies for the N4 treatment were higher than the ones in the other treatments. Water use efficiency of N4, N5 and N6 treatments in both cultivation years was almost equal and more than the ones of other treatments. These results indicated that the water and nitrogen use efficiencies were higher in treatment with NNI closer to 1 (optimal treatment) as compared to other treatments.

Biochar is a coal produced from plants biomass and agricultural waste in limited Oxygen condition. In the process of producing Biochar no Carbon Dioxide is released into atmosphere, so Biochar is fully carbonated. Many studies have been conducted on the ability of Biochar in improving soil condition and maintaining soil nutrients; however limited studies have been conducted on effect of Biochar on nitrate removal from drainage waters. In this paper, it has been assumed that because of high amount of Carbon in Biochar, using Biochar instead of raw Carbon materials in nitrate removal bioreactors can effectively eliminate the nitrate from subsoil drainage. In order to evaluate the effect of different mixtures of Biochar (0, 10, 15, 20and 30 percent) and effect of different inlet nitrate concentration (40, 160 mg/liter) on bioreactor performance regarding nitrate removal, bioreactors with 125cm poly-ethylene pipes were stimulated. The experiment was performed in factorial method in a random scheme with three repetitions. Results showed that nitrate removal is strongly affected by Biochar percentage used in them. The maximum nitrate removal was reported in pipes with 30% Biochar (96.4%) and the minimum was reported in replication pipes with no Biochar (80.7%). Also, nitrate removal is also affected by concentration of inlet nitrate solution. Nitrate removal percentage in C2 treatment (160 gr/liter) was lower than C1 treatment (40 mg/liter), the results were 89.9% and 91.4% respectively.

Nitrogen leaching from agricultural lands is a major threat to groundwater and surface waters. This study investigated the relationship between the characteristics of wheat-straw biochar produced at different temperatures and its impact on the uptake of NO3--N.
Three types of biochar were produced from wheat straw at three different pyrolysis temperatures of 300, 400 and 500°C, and sampling was done 3 times for each biochar. Physical and chemical characteristics of biochar were determined using a variety of methods including specific surface with methylene blue adsorption method, and elemental content with elemental analyzer, and water solubility with standard ASTM (D5029-28) method. Statistical analysis was performed using Freundlich and Langmuir models. Nitrate concentration was measured using a UV-V spectrophotometer with a wavelength of 500 nm.
It was indicated that with an increase in biochar pyrolysis temperature from 300 to 500°C, the hydrogen, oxygen and nitrogen in the biochar were significantly decreased (P The present study shows that pyrolysis temperature greatly influences the biochar chemical and physical characteristics, and subsequently nitrate adsorption ability of the biochars. The wheat straw biochar, which is produced at a pyrolysis temperature of 500°C, has the highest adsorption capacity for nitrate.

The normalized water productivity (WP*) parameter was calibrated for Corn Single Crosses 704 in this study. This parameter is one of the inputs AquaCrop model upon which the daily biomass production simulated. The default value of WP* is 33.7 grams per square meter in the model. This study was conducted for two years (2015-2016) at an experimental farm of Abouraihan collage belonging to the University of Tehran in Pakdasht Region. The total numbers of plots were tree. Each plot size was 25 m2. Biomass yield of corn was measured six and seven times during the growing season in 2015 and 2016, respectively. The data measured in the first year (2015) and second year (2016) were used for calibration and verification, respectively. Calibration was done using two methods of trial and error and Steduto et al. (2009). The WP* was calibrated with a little more accuracy by Steduto et al. (2009) method and its value was estimated equal 32.3 grams per square meter. Root mean square error and mean bias error for the comparison between measured and estimated biomass production are 0.73 and 0.25 ton ha-1 for the tested data set.

Nitrate leaching under furrow irrigation is one of the main reasons of underground water contamination. In order to use fertilizer efficiently and reduce loss of nitrogen, more detailed studies should be done about distribution of different forms of nitrogen under ridges and furrows because the solute movement is not same in those positions. The main objective of this study was to scrutiny effects of different rate of urea on nitrogen uptake and accumulation of nitrate and ammonium under ridge and furrow during growing season. So that maize was planted in the treatments with nitrogen rates of 0, 150 and 250 kg ha-1 by Randomized Complete Block design with three replications. The amounts of dry aboveground biomass and nitrogen uptake during growing season plus concentration of nitrate and ammonium in soil before and after fertilizing and after harvesting were measured over different depth under ridges and furrows. Results showed that depth and rate of nitrogen were two effective factors on accumulation of nitrate and ammonium under ridges and furrows. More nitrate concentration was observed under ridges in comparison with furrows. After fertilizing, nitrate concentration under ridges and furrows was decreased and increased respectively along with raising depth. Also, it was demonstrated that nitrogen uptake were increased and agronomic nitrogen efficiency were reduced by more nitrogen application. Furthermore, most nitrate accumulation was observed below roots area, especially under ridge, after harvesting therefore the probability of nitrate leaching was very high.

Transport and transformation of urea, nitrate, and ammonium in the soil take place as a sequential decay chain reactions which should be considered altogether for more precise management of water and fertilizer in agricultural farms. In this study, HYDRUS-2D model was evaluated to predict distribution of water, nitrate and ammonium under furrow and ridge during the growing period of maize. Thus, maize was planted in the treatments with nitrogen rates of 0, 150, and 250 kg ha-1. The amounts of nitrogen uptake, soil water, nitrate, and ammonium concentrations during the growing season, before and after fertilization, and after harvesting were measured over different depths under ridges and furrows. Results showed suitable agreement between predicted and measured water, nitrate and ammonium distribution in soil during validation stage. NRMSE and R2 as evaluation indexes for the predicted soil water were calculated as 0.772 and 4.37%, respectively. Besides, these indexes were calculated for the predicted ammonium concentration under furrow and ridge for all treatments and were found to be in the range of 0.645-0.798 and 14.23%-29.4%, and for the predicted nitrate concentration, they were in the range of 0.716- 0.829 and 23.57%- 25.2%, respectively. According to the results of this study, the HYDRUS model is a useful tool for management of water and fertilizer in furrow irrigation.

The nitrogen demand during growing period is variable for plant, but most farmers use large amount of nitrogen without the knowledge of the proper time in order to achieve maximum product. This pattern of fertilizer consumption causes environmental pollution. The optimum demand of nitrogen during growing period could be determined by the critical nitrogen equation. The main objective of this study was to determine the coefficients of the critical nitrogen equation for maize in Pakdasht. Comparing these coefficients with suggested coefficients in France and China was the second objective of this research. The maize (single cross 704) for a season was planted on the farm of Aburaihan campus. The aboveground biomass (W) and its critical nitrogen concentration (Nc) were measured in six different times, from 26 days after planting to the harvesting time. The coefficients of critical nitrogen equation were determined using theory of critical nitrogen dilution curve. Finally, the equation of Nc = 2.9 W -0.27 as nitrogen critical dilution curve was proposed for maize in the Pakdasht. The results showed that the nitrogen status was mispredicted in 21% and 14% of measured data point, by France and China equations respectively while this erorr was only 9% by using the equation provided in this study. The main reasons for these errors are differences in climate and prevalent varieties of maize in different areas.

Soil salinization is a process in which the accumulation of soluble salts in soil profile can affect soil physical and chemical properties، such as osmotic pressure، permeability and hydraulic conductivity. These، in turn، can seriously impair or completely stop the growth of plants. In this study، four theoretical models for predicting soil leaching contains including Series of Reservoirs Model (SRM)، Theoretical Plate–Thickness Model (TPTM)، Convection – Dispersion Model (CDM) and Numerical Model (NM) were studied in order to select and introduce the best model for predicting ultimate soil salinization. The results of these models were compared with real data obtained from field experiments. To do this، 15 basin plots (each has one square meter) were firstly built. Then، five leaching depths of 20، 40، 60، 80 and 100 cm were applied to basins in three rows. Results revealed that the investigated models showed different performance for the different depths of leaching. Overall، Series of Reservoirs Model (SRM) was able to estimate the ultimate salinity more accurately.

Saturated hydraulic conductivity (Ks) is one of the most important physical features of soil that have wide usage in soil and water science. Measuring Ks carries on laboratory and field. Guelph permeameter (GP) method is one of the field measuring method for determining field saturated hydraulic conductivity (Kfs) above the ground water table. Well-shape-factor (C) is one important parameter needed to calculate Kfs, which related to pressure gradient of flow through the soil around the borehole. Several approximated analytical solution are presented to determine C, such as Porchet solution, Glover solution, half-source (Reynolds et. al.) solution. Numerical solution is obtained using finite difference by Reynolds et. al. (1985) and applied formulae fitted them by Zhang et. al. (1998). Developed theory of flow out a borehole corresponds the flow to hydraulic conductivity (Kfs) and soil matrix potential (Ǿm) which can be obtained by measuring outflow in two different ponding depth in single hole. One of the restrictions of this method is the negative results that may be seen in some cases. In this research, the GP experiments were down in 18 holes of 3 cm radius and 60 cm depth in a loamy soil with different ponding head (H), (maximum and minimum H was 5 and 20 cm, respectively). Then the field saturated hydraulic conductivity (Kfs) was determined by two head analysis of GP, Richards, Laplace and Regression analysis with different solution methods for well shape factor (C). Results showed that if the Porchet method was used for C factor calculation, negative results have been minimized and other methods for the C calculation (Glover, Numerical and Half-Source) have been produced low to high negative results for (Kfs), respectivity. According to this study, the increasing of ratio of H2 to H1 will be caused a large number of (Kfs) values to be positive and also there were no significant differences between their means. In the Richards, Laplace and Regression analyses, the Glover, Numerical and Half-Source solution of C had the least deviation of mean, respectively. Analyses of Regression model with Numerical Solution of C has the nearest results with two head analysis.