فهرست مطالب mehdi homaee

Cyanobacteria are one of the main components of soil biocrusts in arid and semi-arid regions that grow in the surface layer of the soil. They actively participate in the cycle of elements by secreting polysaccharides and play an important role in improving soil quality and fertility. Accordingly, they have been used in soil and water resources conservation issues in recent years through cultivating and producing the required biomass in laboratory conditions and inoculating at the soil surface. However, the proper media for optimal growth of the soil microorganisms have not been reported comprehensively. The present study was conducted to select the optimal culture medium for the growth of cyanobacteria in experimental conditions. For this purpose, the performance of three culture media viz. BBM, BG11 and CHU10 was compared during the one-month growth period of soil cyanobacteria. In this regard, the types of grown microorganisms as well as the number of cyanobacteria present during the growth period of one-month and on average once every 4 days were examined. The results showed that soil cyanobacteria in BBM culture medium had better growth than the other two culture media and at the end of the growth period, the number of cyanobacteria grown in BBM, BG11 and CHU10 medium was 91790, 48638 and 1491, respectively, per milliliter. Therefore, BBM culture medium is proposed as the optimal culture medium for use in preparing the biomass required by cyanobacteria for inoculation at the soil surface.

Runoff is one of the most important hydrological processes in ecosystems, which is very important in the management of water and soil resources. Although the use of soil microorganisms as soil inoculants in the bioengineering management of runoff has been confirmed, the use of soil microorganisms to control runoff in soils contaminated with petroleum has not been considered. Therefore, in order to evaluate inoculation of soil Bacteria, Cyanobacteria and fungi in reducing runoff in soil contaminated with petroleum, the present study was carried at plots of 0.5×0.5 m with slope of some 25% and level of 20000 mg kg-1 of gasoil and control contamination in three replicates. The plots will be then subjected to rainfall intensity of some 35 mm h−1 and duration of 30 min installed at the Rainfall Simulation Laboratory of Tarbiat Modares University at Faculty of Natural Resources. The results showed that the inoculation treatments, although there was no significant difference compared to the control treatment (P>0.05) except for the start of runoff (P<0.05), improved the components of runoff. The comparison of the mean of the study variables showed that the bacteria, cyanobacteria, fungi, bacteria+fungi, bacteria+cyanobacteria, cyanobacteria+fungi, and bacteria+cyanobacteria+fungi caused +47.10, -0.08, -10.72, -24.86, +14.85, +49.88 and +27.88 percent changes in runoff start time, +4.58, -54.04, +65.19, +72.20, -41.36, -84. 53 and +40.15 percent changes in runoff volume, and +4.75, +54.06 and -65.15, +72.28, -41.39 and -84.55 and +40.20 percent changes in runoff coefficient, respectively. The results of the research indicated the relative synergistic performance of the combination treatment of cyanobacteria + fungi in reducing the effect of gasoil on runoff properties. Finally, the results of the present study showed that the inoculation of native soil bacteria, cyanobacteria, and fungi can be an efficient and sustainable biological technology to improve runoff characteristics in areas contaminated with petroleum.

Water stress is one of the dominant stresses limiting crop growth and yield, particularly in arid and semi-arid regions. The best strategy to deal with water stress is choosing a water-tolerant plant based on reliable screening methods such as polyethylene glycol (PEG). To evaluate different predictive models and quantitatively investigate camelina response to drought stress during the germination stage, an experiment was conducted in a completely randomized design with three replications. Water stress treatments included six matric potentials of PEG6000: 0 (control, without stress), 3000, 6000, 9000, 12000, 15000, 18000 cm. Germination indicators were calculated using the SeedCalc package in R software and MATLAB was used for programming and models fitting. Water stress models including Feddes et al. (F), van Genuchten (VG), Dirksen and Augustijn (DA) and Homaee (H) were assessed and compared afterwards. Data analysis was performed using SAS software (V. 9.4). The threshold values under germination rate (GSI), mean seedling length (M-SL), mean root-to-stem ratio (Razao) and seed vigor (SV-S)) were then obtained for the control, 6000, 3000 and 3000 cm, respectively. According to these four germination indices, the camelina is very tolerant to water stress. In all four indicators of GSI, M-SL, SV-S and Razao, the H model presented the best performance. The highest values of GSI, Razao, M-SL, stem and root length were obtained at matric potentials of control, 3000, 6000, 3000 and 6000 cm, respectively, indicating the suitability of camelina cultivation in areas under water shortage.

When using a surface drip irrigation, the infiltrated water in the soil forms a wetted zone around an irrigation dripper. The knowledge of the soil water distribution and wetting patterns around the irrigation emitter is an important factor for designing and managing drip irrigation systems, for precise delivery of water and nutrients in the crop root zone and for matching the wetting pattern with the root growth pattern. The soil wetting pattern depends on soil hydraulic properties (soil texture, structure, hydraulic conductivity, water table) and irrigation management (Irrigation method, discharge rate, irrigation frequency, the total volume of applied water, emitter spacing and position above or below the surface). In recent years, using pulsed management in drip irrigation systems has increased because of its positive effects on the soil water distribution and consequently plant growth and development. Pulsed drip irrigation refers to irrigating for a short period of time and then waiting for another short period and repeating this on-off cycle until the entire irrigation depth is applied. In the present study, the effects of different pulsed managements with different off-time durations on the soil water distribution and wetting pattern dimensions in a clay soil was investigated, and the performance of the HYDRUS-2D model in simulating soil water distribution under pulsed drip irrigation was evaluated.

The treatments included three pulsed drip irrigation scenarios where irrigation water was applied in two (P2), three (P3), and four (P4) cycles with two on-off time duration periods were taking either the on and off times equal (T1) or considering the off-time duration periods as three times that of the on-time duration (T2). A soil container of internal dimensions (90 cm length, 90 cm width and 120 cm depth) was used in the experiments. One sides of this container are plexi-glass sheets to monitor advancing soil wetting pattern at different times during the experiments and the other sides are metal plates. The soil texture used in this study was clay. The duration of the experiment for all treatments was three hours, so the volume of water was constant for all treatments. The gypsum blocks that were calibrated before were used to measure the soil moisture within the wetting pattern. The measurements were recorded by a reader every half an hour after the start of the experiment in each treatment. The HYDRUS-2D model were used for simulating the soil water content under different pulsed treatment. It was calibrated and validated by the soil moisture measurements using inverse modeling. In order to statistically analyze the results of applying different irrigation pulses on the soil moisture distribution and wetting pattern the t-test analysis was used at a significance level of 5%. The simulated values of soil water content by the HYDRUS-2D model were compared with the corresponding measured values using some statistical criteria including root mean square error (RMSE), mean absolute error (MAE), and model efficiency (EF).

In the present study, the effect of different pulsed management and off-time duration on soil moisture distribution in a clay soil under a drip irrigation system was investigated. The performance of HYDRUS-2D numerical model was also evaluated to simulate moisture distribution in a clay soil under pulsed drip irrigation system. The results showed that increasing the number of pulses, increased the depth and width of the soil wetting pattern by 8 and 12%. Also, increasing the off-time duration, increased soil wetting pattern dimensions (depth and width) around an irrigation dripper in a clay soil by 13.5% and 20%, respectively. Pulsed irrigation improves soil water content distribution that it does not exceed from field capacity despite the heavy soil texture. Therefore, it can be concluded that better conditions in terms of aeration and oxygenation are provided for the crop roots under pulsed drip irrigation management. Also, evaluating the simulation of soil water content distribution and soil wetting pattern dimensions with the measured ones showed that the HYDRUS-2D model has a good accuracy in estimating soil wetting pattern dimensions (R2=0.95) and simulation of soil water content distribution (RMSE=0.018) in a heavy soil under pulsed drip irrigation. Therefore, the HYDRUS-2D numerical model can be used to simulate soil wetting pattern and soil moisture distribution for the design, management and scheduling of the drip irrigation systems with pulsed management.

Iran has a large area under cultivation, and reliable and timely crop yield forecasts are critical for making timely food supply decisions. As a result, several methods for estimating crop yield based on remote sensing observations have been published in recent years. One of the first and most critical steps in this study is to estimate real evapotranspiration using the SEBAL algorithm and high spatial and temporal resolution Landsat8 satellite images. The evapotranspiration obtained from satellite images was compared to evaporation data from the Zanjan synoptic meteorological station's evaporation pan, with statistical indicators (MAE=0/36, RMSE=0/45, R2 =0/94) indicating satisfactory results. The AquaCrop model and its four execution steps were used to simulate the product yield, and the necessary coefficients and data from the model were applied in satellite imagery calculations for each of these steps. For comparing CC data determined by satellite imagery and AquaCrop model, the RMSE, MAE, and R2 indices were respectively 11/06, 9/2 percent, and 0/94, and 0.633 and 0/359 mm/day and 0/95 for transpiration. The average yield was calculated to be 1/189 ton/ha in field pixels and its comparison with agricultural statistics and field studies (1-1/2 ton/ha) showed acceptable estimates for wheat yield in the area of this study.

Germination plays a vital role in crop establishment and its yield. Most oilseeds are sensitive to salinity at germination, so cannot be irrigated with saline water. Although camelina is considered as a tolerant crop to water stress, but its tolerance to salinity must be investigated. To quantitatively evaluate camelina response to salinity at germination stage, an experiment with a completely randomized design was conducted including 17 water salinity levels of 0.85, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 dS m-1, each with three replicates. Germination indicators were calculated using the SeedCalc package in R software and MATLAB. The optimization procedure was carried out with frequent changes in the model parameters based on reduced RMSE and minimizing least squares error. Then, parameters of salinity models including Maas-Hoffman, van Genuchten-Hoffman, Dirksen-Augustijn and Homaee et al. were derived and compared. The obtained threshold values of germination rate (GSI), seed vigor (SV), SeedCalc seed vigor (SV-S) were 2, 12 and 12 dS m-1, respectively; The corresponding reduction slope for these variables were 2.4, 7.7 and 1.7%, respectively. Based on the obtained EC* and the slope, it was concluded that camelina is very tolerant to salinity at this growth stage. So that, it can be established quickly and produce strong seedlings at very high salinity levels. Further analyses of model performance statistics indicated that the examined nonlinear models provide better performance. Best performance of fitted models was obtained by HVG and H models, respectively. Germination indices were decreased by increasing the salinity levels, a lower GSI was associated with decreased seeds water uptake. The higher the seed vigor, the higher the GSI and seedling growth, as well as the lower MGT. Overall, camelina can be considered as a suitable alternative for oilseed cultivation in semi-arid regions.

The optimal design, operation and management of drip irrigation systems relies significantly on selection of a suitable combination of emitter discharge rate, emitter and lateral spacing, root depth and soil hydraulic properties that should be in consistent with root growth pattern in the soil for delivering required amount of water and nutrition to the plant. Modeling soil wetting pattern is more practical and easier than the conducting laboratory or field measurements. In this study, an empirical model was developed to predict the dimensions of the wetting pattern under pulsed drip irrigation using dimensional analysis method. The main inputs of the proposed model are emitter discharge rate, saturated hydraulic conductivity, total volume of applied water and pulse ratio.  Experimentations included determination of the maximum depth and width of the wetting pattern after water application under different combination of pulses in a clay soil. The treatments were consisted of three pulses (P2, P3, P4) and two Off-Time durations (T1, T2). The predicted values of wetted depth and width by the empirical model and the HYDRUS-2D model were compared with the observations. The coefficient of determination parameter for the measured and estimated wetting pattern dimensions that obtained from empirical model was 0.94 and 0.93 and for numerical model was 0.95 and 0.97, which indicates good accuracy of the models. The results of the T-test analysis indicated that the empirical and numerical model simulated values were not significantly different (with a probability of 99.5%) from the observed ones. Although, on the basis of RMSE, ME and EF parameters the HYDRUS-2D model performance was better than the proposed empirical model but due to the simplicity of use and requiring less number of input parameters, it is recommended to use the developed empirical model to predict the wetting pattern as required in the design of drip irrigation systems.

Due to the scarcity of water around the world especially in arid and semi-arid regions, accurate determination of crop water requirement is essential for proper irrigation planning and management. One of the common methods for estimating crop evapotranspiration is the use of reference evapotranspiration and crop coefficient (Kc) (or the FAO-56 Kc-ETo approach). Different climatic conditions, plant variety, and differences in crops, soils and irrigation management practices result in variations in crop coefficient for the same crop between the locations, therefore locally developed Kc values are necessary for more accurate estimation of crop evapotranspiration. The aims of this research were to estimate silage maize crop coefficient using water balance method under pulsed drip irrigation system during two growing seasons (spring and summer) and to develop an equation to calculate silage maize crop coefficient based on growing-degree-days in Varamin. Silage maize actual evapotranspiration based on water balance method was 465 and 373 mm for spring and summer growing seasons respectively. Silage maize crop coefficient for initial, mid and late growth stages of spring and summer growing seasons were calculated 0.24-0.27, 1.28-1.3 and 0.8-0.88 respectively. The results showed that using silage maize crop coefficient proposed by FAO-56 caused 8% underestimation in crop evapotranspiration. Significant difference ( ) was found between  and , while using the equation presented in this study estimates silage maize evapotranspiration reasonably well, with the mean absolute error (MAE) of 0.53 mm/day, the root mean square error (RMSE) of 0.7 mm/day and the agreement index (d) of 0.98. Therefore, using developed regionally based and growth-stage-specific Kc helps in irrigation management and provides precise water applications for this region.

Sediment production at each stage of erosion and its redistribution vary at different scales in a watershed, a slope and even a plot. The preparation of sediment budgets on watershed and slope scales have been considered in the two preceding decades, and a review of this tool on a plot scale can also help to better understand the process of sediment production, redistribution and delivery. The present study was conducted to budget sediments in laboratory plots with sandy-loamy soil and under rainfall simulation with the intensities of 30, 50, 70 and 90 mm h-1. Sediment tracing was performed on the surface of the plots by measuring the changes in the density of synthetic color-contrast aggregates using image processing. The results indicated the ability of this method to prepare sediment budgets on a plot scale. The contribution of interrill erosion in sediment production was increased with an increase in the rainfall intensity; however, the proportion of sediment redistribution within the plot was decreased. The average sediment delivery ratios for the rainfall intensities of 30, 50, 70 and 90 mm h-1 were 7.30, 8.54, 11.74 and 15.64%, respectively. The insignificance of this ratio on a plot scale was emphasized due to the short period of the experiment and should be considered in laboratory research projects.

Water scarcity across the world has led researchers to develop a new irrigation technique called pulsed drip irrigation in order to improve soil moisture distribution as well as to increase water productivity. Pulsed drip irrigation refers to irrigating for a short period then waiting for another short period and repeating this On-Off cycle until the entire irrigation depth is applied. In this study, the combined effects of pulsed drip irrigation and its On-Off time duration on yield, yield components and water productivity of silage maize under two growing seasons (spring and summer) were evaluated. The selected experimental design was split-plot in completely randomized block design with three replicates. The treatments were consisted of four pulsed drip irrigations (P1, P2, P3, P4) and two Off-Time duration, 1 and 3 times of On-Time duration in a pulse (T1, T2). Results indicated that the interaction of the studied treatments on yield, yield components and water productivity of silage maize is significant. The maximum dry yield and water productivity was 25.86 (ton/ha) and 5.95 (kg/m3) in (T2 P4) treatment (average of two growing seasons) which increased by about 17% compared to (T1 P1) treatment. Increasing the number of irrigation pulses to four times lead to 6% and 17% increase in the studied parameters, respectively, in T1 and T2 treatments. Consequently, based on the positive effect of increasing the Off-Time duration in applying pulsed drip irrigation with high flow rate, it is suggested that the ratio of Off-Time to On-Time duration should be increased.

Increasing scarcity of water resources and its influence on quality and quantity of crop yield motivates farmers to apply deficit irrigation as an approach to overcome the lack of water. On the other hand, the importance of water as an intermediate good in agriculture has increased competition to access water as an economic good. Consequently, determining the irrigation water price under deficit irrigation is necessary to improve water productivity. In order to assess the impact of water price on water productivity, in this study green pepper was cultivated under four different water levels including 50, 70, 100 and 120% of crop water requirement. The crop was cultivated in the writers’ personal greenhouse under controlled and isolated environmental circumstances in Tehran. The crop yield was then harvested and its dry matter measured at the end of growth period. The results showed that after applying deficit irrigation and optimizing irrigation water depth, water price was reached to the maximum which was 183.44×〖10〗^3 Rials per cubic Meter. In addition, under deficit irrigation, water use efficiency was 5.67(kg/m³), physical productivity was 5.1(kg/m³), physical-economical productivity was 191.42×〖10〗^3 (Rls/m³/ha) and economical productivity was 1.04. Furthermore, the deficit irrigation before water depth optimization did not considerably affect irrigation efficiency, while after water depth optimization, deficit irrigation resulted better irrigation efficiency than full irrigation scheme.

Soil water retention curve is among the most important properties needed for many soil and water management purposes. Due to high spatial and temporal variability in soils, its direct measurement is rather difficult, time consuming and expensive. Consequently, it would be more feasible to estimate it by using some indirect mathematical methods. The objectives of this investigation are to (1) determine the fractal dimension of the soil retention curve by fitting fractal models to the measurements and (2) investigate the relationship between the fractal dimension and other physical/textural/hydraulic parameters such assoil particle fractions of clay, silt, and sand in large scale. For this purpose, 190 soil samples with broad range of textures from four large agricultural areas were collected, and their particle size distribution, bulk density, organic carbon, salinity, pH, and retention curves were measured. To evaluate the performance of examined fractal models, three statistical parameters including RMSE, RMSD and R2 were used. Results indicated that the fractal dimension has an inverse relationship with soil texture; the finer the soil texture, the greater the fractal dimension. The lowest and greatest fractal dimensions of the Tyler-Wheatcraft model in loamy sand and clay textures were obtained to be 2.38 and 2.74, respectively. These were significant at 1% level based on the Duncan’s multiple range tests. Results further showed that the most accuracy of estimating retention curve in different soil textures by using van Genuchten, Brooks-Corey, and Tyler-Wheatcraft with normalized errors average obtained were 0.06, 1.09, and 3.27, respectively. Furthermore, the obtained R2 values were ranged from 0.88 to 0.99 for Tyler-Wheatcraft and van Genuchten models, respectively. Compares to Brooks-Corey model, the van Genuchten retention model provided better accuracy in estimating retention curve for different soil textures.

Soil and water salinity is one of the most important factors in reducing the yield of plants in arid and semi-arid regions, which tends to limit plant growth and its development. In saline soils, yield production directly influences by soluble salts in the root zone as well as by shallow water table depth. The first step for reclamation of such soils is reducing salinity to optimum level by leaching practice. Assessing the quantity of water required for this practice, as well as saving the applied water and proper use of water resources for optimal water management are of great importance for leaching process. The objectives of this study were to investigate theoretical models to predict ultimate salinity and to compare the predicted outcomes with experimentally obtained data. For this purpose, several field saline-sodic soil reclamation experiments were carried out in Jafir area, Khuzestan plain, Iran, by using double rings. All experiments were conducted by applying 100 cm water depth in four-25 cm intervals and intermittent ponding method. Four theoretical leaching models including series of reservoirs (SRM), numerical solution (NM), continuous column (TPTM) and secondary reservoir (SRBM) models were used to predict the ultimate salinity. All models outputs were then verified with the real data. Results indicated that among four examined models, the SRM and SRBM models provide more reliable outputs. Although the performance of studied models differed for different depths of applied leaching water, but considering the lower RMSE and RMSEn values of SRM model, this model is more suitable for forecasting the results of leaching and soil reclamation in the study area. This model could reasonably well estimate the designated final salinity.

An accurate estimation of reference evapotranspiration is crucial for optimal irrigation scheduling and management. Also, achieving accurate medium range forecasts of effective parameters in estimating reference evapotranspiration is a key component for dynamic irrigation scheduling. This study was aimed to investigate the effect of using Weather Research and Forecasting Model (WRF) regional forecasts to increase the accuracy of reference evapotranspiration estimation. Consequently, the precision and accuracy of the model, and the outcome of forecasts performance at 24, 48, 72, 96, and 120-hours were evaluated to estimate the reference evapotranspiration. For this purpose, the output of the model for four stations including Qazvin, Esmaeil-Abad, Karaj and Hashtgerd were extracted for a period of three months (May-July, 2018) with a 10-days average of the base period. The weather data of 2018 at these stations with the corresponding ones were compared afterwards. The results indicated that the 10-days reference evapotranspiration (average of all stations) in the study period, according to the base period were -20.9, -8.12 and 7.83 percent, respectively. These variations reflects the deviation of the reference evapotranspiration value in the study period in comparison with the base period, indicating the need for using medium-range forecasting in order to correct reference evapotranspiration estimates. The range of determination coefficient (R2) of model output was obtained to be between 0.813 and 0.921. Due to the statistics, the model output for all stations and the lead-time forecasting periods of 24, 48, 72, 96 and 120 hours can be evaluated with high accuracy and its application would enhance the accuracy of reference evapotranspiration estimates. According to the results, not only in terms of time coordination, but also in terms of quantity, there was a high similarity between the estimated values of evapotranspiration derived from its post-statistical output of the (WRF) with calculated values.

This study was aimed to determine the influence of temperature within the landfill on the shear strength of the MSW samples through the shearing procedure. Different waste samples, i.e., the fresh (C1), 2 years old (C1-2Y) and lab oratory prepared (C2) MSW samples, were heated up, prepared, and placed in the shearing box with the designated temperatures of about 25, 45, and 65 °C (i.e., the range of an anaerobic landfill). The Mohr–Coulomb strength parameters for the warmed-up and room-temperature specimens were separately calculated and compared. The temperature decreases the friction angle from 21 to 17° for T > 45 °C. The cohesion was also decreased by temperature from 19.9 to 13.1 kPa. In addition, two nonlinear envelopes were developed for the specimens tested at room and simulated temperature within the landfill. The test results show a reduction of about 20% for friction angle and shear strength at the temperatures between 45 and 65 °C. Although the warmed-up specimens of fresh MSW were denser under certain normal stress, heating the MSW specimens to temperatures of 45 and 65 °C resulted in loss of the shear strength. Results further indicated that the temperature of the wastes plays an important role when the shear stress is conducted on the MSW specimens. It can be then concluded that temperature of the landfill should be considered as a factor influencing the shear strength of MSW. Considering temperature for site investigation of the shear strength and the correlation of the results with the laboratory tests is important, too.

Soil salinity and nutrient imbalances are two important limiting factors for plant production in arid and semiarid regions. Quantification of such limiting factors is pivotal for any management in these areas. In this investigation novel deterministic linear and nonlinear models were derived for predicting plant response to interactive effects of salinity and phosphorus through integration of a non-linear salinity model with two basic soil fertility models. To examine and evaluate performances of newly proposed models, several experiments were conducted under separate and combined salinity and phosphorus levels in field conditions. Treatments were consisted of five natural salinity (0.3, 3, 6, 9 and 12 dS m−1) and four phosphorus levels (0, 20, 40 and 80 mg kg−1 soil as KH2PO4), each with three replicates. The obtained results indicated that the proposed nonlinear model (Eq. 7) with R2 of 0.92 provides better estimations than other proposed models for canola yield under different levels of salinity, different levels of soil phosphorus and under combination of different levels of salinity and phosphorus. All proposed models accounting for simultaneous salinity and phosphorus showed that applying 20 and 40 mg P kg−1 soil, or even no use of phosphorus in soil had no significant impact on performance of salinity threshold value, while adding 80 mg P kg−1 soil would lead to increase the salinity threshold value.

Knowledge about soil texture is very important in agricultural studies due to its direct impact on other soil properties. However, determining the soil texture in vast areas requires a lot of time and money. For this reason, researchers are looking for ways to determine this important feature of the soil on a large scale. One of these methods is the use of surface soil spectrometry. In this method, the choice of calibration method significantly affects the accuracy of measuring the characteristics of the surface. In this study, the performance of two regression techniques, namely, partial least-squares regression (PLSR), principal component regression (PCR) were compared to identify the best method to assess sand, silt and clay. For this purpose, 50 soil samples from Tehran province were collected and used as a data set for Calibration and Validation. Soil samples with different moisture levels (oven dry, 5, 10, 15 and 20 w/w) were scanned using a FieldSpec Pro Spectroradiometer with a measurement range of 350–2500 nm. The spectra were subjected to three pre-processed techniques, e.g., Savitzky–Golay (SG) smoothing, first derivative with SG smoothing (FD-SG), Normalization with SG smoothing (Normal-SG). The R2 results from cross-validation indicated that the PLSR model had a better performance than PCR. Normal + SG pre-processing method for clay loam texture and SG method for sandy clay loam texture showed better estimation of measured properties. The amount of R2 for clay was 0.74, 0.81, 0.97 and 0.87, respectively, in moisture content of oven dry, 5, 15 and 20% in   clay loam texture And 0.95 and 0.61 at oven dry and 5% levels in sandy clay loam. Silt was better predicted by R2 0.67 in moisture content of 5% in clay loam texture and R2 0.97 in moisture content of 20% at sandy clay loam texture. Sand was also predicted (R2= 0.86 and 0.72) in moisture content of 5 and 10% in clay loam texture.

Hydraulic conductivity and retention are important characteristics of porous environment in relation to imposed contaminants. Retention curve and hydraulic conductivity are dependent on soil characteristics and soil solution. When Chlorinated pollutants enter to groundwater will contaminate it due to its compounds. Thus preventing them to enter soil and water is crucial to avoid any contamination. In order to investigate the hydraulic behavior of Trichloroethylene in soil, the retention of Trichloroethylene and water were determined. Determining the saturated hydraulic conductivity and estimating the unsaturated hydraulic conductivity by Mualem -van Genuchten, Mualem - Brooks- Corey and Mualem- Kosugi models in the two-phase NAPL-air systems were further objectives of this study.

In this study, the hydraulic behavior of both Trichloroethylene fluid and water were examined. In order to draw the water and Trichloroethylene retention curves in SiL soil the hanging water column method was used. The constant head method was employed to determine the saturated hydraulic conductivity. The Soil retention parameters for Trichloroethylene and water were obtained based on van Genuchten, Brooks-Corey and Kosugi retention models, using the RETC program. The unsaturated hydraulic conductivity, for both fluids as a function of Matric potential was obtained based on Mualem -Brooks-Corey, Mualem -van Genuchten and Mualem-Kosugi models. The performances of these models were assessed by some statistics including ME, RMSE, EF, CD and CRM.

The obtained results indicated that in a certain amount of liquid phase, Trichloroethylene has lower retention and larger hydraulic conductivity compared to water in soil. According to lower surface tension and viscosity of Trichloroethylene compared to water, the saturated hydraulic conductivity of Trichloroethylene and water were 136.75 and 94.5 cm/day, respectively. For water, the van Genuchten retention model demonstrated highest EF (0.93) and lowest RMSE (0.018) values compared to Trichloroethylene fluid. The other two models were also provided more efficiency for water than Trichloroethylene. In the case of Trichloroethylene, the van Genuchten and Brooks-Corey models showed highest efficiency. Generally, the accuracy of all three models for Trichloroethylene was less than water.

The validation results of hydraulic models shows that the van Genuchten model provides better prediction for retention in soil compared to Kosugi and Brooks-Corey models in the two-phase air-water and air-Trichloroethylene system. Trichloroethylenefluid according to its higher hydraulic conductivity and lower retention compared to water, if enters to soil would have faster movement to the groundwater as a consequence of high infiltration rate to aquifer.

Loss of yield as a result of natural damages and its adverse effect on crop production is one of the important issues in agriculture (Barlow et al., 2015). Environmental stresses, particularly cold and frost stresses, affect the morphological and physiological characteristics of plants (Akhil et al., 2008). Identifying and determining spatial distributing of rice fields under frost damage is important for evaluating the food security and improving crop production management (Simaie et al., 2013). The objective of this study was to come up with zoning the frost damage using satellite imagery and cold degree days (CDD) index to evaluate the severity of frost damage in different growth stages of rice plant. In this research, climatic parameters including maximum, minimum and mean of temperature were obtained from Kiyashahr synoptic station. A number of 180 images with the MOD11A1 code related to the crop season, which covering the Guilan area, were taken from the National Aeronautics and Space Administration (NASA) site. In order to create surface temperature maps in Rasht, land surface temperature product of MODIS sensor was pre-processed. By using the satellite images and Cold Degree Days indices in three growth stages of rice (seedling, panicle initiating to the end of booting, cluster to flowering), the influence of frost damage on different growth stages of rice in part of rice fields in Guilan province was evaluated. The severity of frost damage in rice fields was estimated at times when the plant was growing below the critical temperature. The obtained results indicated that the index of cold degree days (CDD) was 8.7 at seedling stage, 3.1 at panicle initiating to the end of booting stage and 11 in flowering stage. Also, investigating the trend of frost zones indicated that Kuchesfahan, Lashtnesha and Khoshbijar areas due to severe frost damage during rice plant growth period imposed to the most damage to plant growth and yield. The zones with the dark pixels (lower than the temperature threshold for growth) in the panicle initiating to the end of booting growth stage were more exposed to frost damage than other growth stages. The obtained results further indicated that integration of remote sensing data with ground information can be used under an improved pattern for interpreting satellite data for areas where low ground data is accessible. This method has a reasonable capability to determine the risk of rice cultivation at rice fields and at different times of year, and consequently can be used to determine the potential of rice fields for second cultivation. Knowledge of spatial and temporal distribution of rice farms temperature is essential for determining energy balance, meteorological studies and identification of rice fields under temperature stresses. Based on the obtained results, satellite images perform well in evaluating temperature stresses. Using satellite imagery, the temperature stresses (frost and heat damage) in different rice growth stages as well as for crop yield reduction can be investigated. The results of the prediction of the average air temperature and the zoning of frost damage can be used in environmental planning such as disease and pest control, optimal water resources management, estimation of damage to fields and environmental studies.

Soil organic matter is considered as an indicator of soil quality and its fertility due to its impact on the physical, chemical and biological properties of soil. The purpose of this study was to investigate the effect of moisture on soil spectral behavior in order to estimate the amount of organic matter using visible-near infrared spectroscopy. Also, the performance of different preprocessing methods was compared in modeling. For this purpose, 50 soil samples from a surface layer (0-30 cm) were randomly collected from some cities in Tehran province. The samples were air-dried and passed through a 2 mm sieve. The amount of organic matter and soil texture were measured in the laboratory. To measure spectral reflectance, soil samples are dry in the oven and they were hydrated with levels of 5, 10, 15 and 20 wt.% (Grams of water / g of soil). Then, Soil samples were scanned using a FieldSpec Pro Spectroradiometer with a measurement range of 350–2500 nm. The results of the cross-evaluation indicated that SNV pre-processing method was better in predicting organic carbon content of soil. The best result for the validation group was obtained in dry oven moisture with R2 and RMSE values of 0.83 and 0.422 respectively. Also, R2 and RMSE were 0.75 and 0.543, respectively, at 5% moisture content, 0.70, 0.553 at 10% moisture, 0.605, 0.558 in moisture content of 15%.

The increase of irrigation efficiency is a technique applied to water conservation; therefore, appropriate and productive management and the application of efficient methods in order to maintain enough water in the soil for optimum utilization of scarce water resources is necessary in the long run. The use of super-absorbent polymers offers effective ways of saving water in agriculture. However, before selecting a suitable polymer, determining of an appropriate model is essential. In this study, the water absorption model was evaluated by two super-absorbent polymers from polyacrylamide family, abbreviated as T-A200 and T-A100. The experiment was carried out with four replicates and water absorption was recorded by the polymers in different times until reaching the equilibrium swelling (stable inflation), as instantaneous and cumulative. After testing the free swelling, the absorption kinetics of fluid (the changes in the absorption of water by the gel time) was determined by immersion in water. After that the result was presented by a graph that depicted the changes in the ratio of absorbed solvent in time to this solvent in equilibrium in time. Also, the trend of solvent absorption by the two polymers in time measured. To determine the mechanism of penetration, the mentioned model used and the values of n and k were calculated. The results showed that the fluid absorption in heterogeneous environments such as gels was associated with significant deformation. The graph shows that in all cases n was less than 5.0, and therefore the mechanism of transfer of the solvent into the polymer network follows the Fick's law. the appropriate super-absorbent polymers in agriculture must be able to absorb maximum amount of water at the minimum time; therefore, doing so will prevent from the loss of rainfall or irrigation water applied. To prove it, the model should follow the Fick diffusion which penetration rate is lower than the speed of molecular relaxation, and only diffusion phenomena is effective through the transfer of ground-penetrating, so, molecular relaxation phenomenon does not affect on the transfer of ground-penetrating. Consequently, after any deformation or swelling, the polymers quickly reached a new balance and stresses will quickly vanish; therefore, it does not have any effect on the speed of penetrating component. In this study, the penetration of the fluid into the polymer followed the Fick model. Hence, this model would certainly be recommended to periodic swelling ability in agricultural purposes.

Soil and groundwater contamination due to leachate from municipal solid waste landfills is one of the most important environmental challenges for management of soil and water resources. This study was aimed to propose a landfill liner from the existing natural materials that in addition of having proper permeability, provides more capacity to absorb leachates. Two natural amendments including bentonite and DCP were applied to coarse landfill soil of Evaz city in Fars province between zero to a maximum 9% and 0.2% of base materials dry weight, respectively. The required permeability tests were conducted with both water and synthetic leachate. Results indicated that for the materials containing 6% bentonite, application of 0.2% DCP was considerably reduced the permeability compares to the bentonite application. Due to larger viscosity, the permeability of synthetic leachate in base liner materials and containing 3% bentonite, was less than the water. However, in the 6% bentonite application, due to its acidity, the permeability of leachate was increased. In 9% bentonite, synthetic leachate had minor effect in reducing or increasing the soil permeability. This can be attributed to significant increase of fine particles and the increase of soil buffering properties.

  Achieving to sustainable development is not possible without soil and water resources conservation and land degradation reducing. On the other hand, in the low density-vegetation lands, biological soil crusts induced by soil micro-organisms' activities play an important role in conserving and improving of soil stability. However, in degraded lands, biological soil crusts are less developed. Thus, recently, biological soil crusts restoration by providing the appropriate conditions for increasing soil micro-organisms' activities have been further considered through the new biotechnologies applying such as soil micro-organisms stimulants. However, the quick and sustainable effectiveness of applying soil conservation strategies is the most important criteria in the selection of managerial practices. Hence, this study was planned to assess performance of a soil bacterial stimulant nutrient (named B4) as completely bio-amendment in reducing soil loss and runoff at laboratory and small plots conditions. In the study, the experimental plots were filled by collected soil of degraded and erosion-prone area of Marzanabad-Kandelus region based on the layering, grain size and bulk density of the native soil area. The solution with 15 g calcium acetate l-1 distilled water (dw), four g yeast extract l-1 dw, and five g dextrose l-1 dw was prepared as B4 stimulant nutrient. Then the B4 was spraied on plots. To this end, two treatments of B4 injection and control with three replications were considered. After 15 days, in the Rain and Erosion Simulation Laboratory of Tarbiat Modares University, the simulated rainfall was carried out with during of 100 min and intensity of 50 mm h-1 according to high-erosive rainfall of the native area. Then, the soil loss and runoff components were measured. Statistical comparison of results indicated that injection of B4 stimulant nutrient improved the soil loss and runoff components through stimulate proliferation of soil bacteria and its adhesion and productivity properties. The start time and time to peak of runoff at the control plots (without injection) were increased significantly (p<0.05) from 24.83 to 49.22 min and from 78.66 to 92.66 min at the stimulant nutrient plots, respectively. As well as, volume and peak of runoff, soil loss and sediment concentration at the stimulant nutrient plots were decreased significantly (p<0.05) and about 88, 92, 95 and 35%, respectively in compared to control. So that, the volume and peak of runoff, soil loss and sediment concentration at the stimulant nutrient treatment were measured about 275.66 and 18.66 mm, 0.49 g and 1.79 g l-1, respectively. According to our results, the restoration and enhancement of biological soil crusts in low density-vegetation and degraded lands through stimulating and increasing population of soil micro-organisms induced by stimulant nutrient founded as an efficient, quick and bio-strategy to conserve soil and water resources. However, further researches are required to achieve reliable strategies by using other microbial stimulants and evaluating their durability under consecutive precipitation and time passing

Soil and water relations are so complex that the most advanced mathematical models can hardly be able to simulate them accurately. Retention curve and unsaturated hydraulic conductivity are among the most important factors in the study of water flow in the soil. Because the high variability and soil complexity, obtaining soil hydraulic properties directly is difficult, time consuming and costly and therefore it is necessary to estimate indirect methods. The purpose of this study was to determine the fractal dimension of soil moisture curve using fractal models and to investigate the relationship between the moisture curvature fractal dimension with hydraulic parameters, clay, silt and sandy percent in a wide area. For this purpose, some soil samples collected from different tissues from the regions of the country were collected and the variables of particle size, bulk density, organic carbon, salinity, pH and moisture content were measured in different suction. Finally, the parameters of the van Genuchten model as well as models Tyler-Wheatcraft and Rieu-Sposito fractals were calculated for soil particle size distribution. The results showed that van Genuchten model parameters have fractal behavior and can be quantified by using fractal models. The results also showed that the higher the amount of sand in the soil, the fractal decreases, but the clay content has a direct linear relationship with the Tyler-Wheatcraft fractal dimension. This means that by increasing the amount of clay in the studied soils, the fractional dimension of the Tyler-Wheatcraft (Dm) model also increases and with the increase in the amount of sand, the fractal dimension of the Tyler-Wheatcraft (Dm) model decreases.

Soil structure is of great importance from both crop production and water resources management point of views. Since soil structure is often expressed qualitatively, the so-called fractal geometry, as a novel method, can be used to describe the soil structure in a quantitative manner. Using fractal concept and its comparison with the classical aggregate stability methods can assist to better understanding of soil structure. This research was aimed to quantitatively assess the soil aggregate stability by using some fractal and classical models. To attain this purpose, a number 30 soil samples were collected from topsoil of an agricultural area. Then, the mean weight diameter MWD and geometric mean diameter GMD of soil samples were determined by using wet and dry sieving method. The fractal dimensions of soil samples were determined for four fractal models including the number-size and mass-size of Rieu and Sposito, number-size of Mandelbrot, and mass-size of Tyler and Wheatcraft. Results indicated that the range of fractal dimensions for mass-size model of Rieu and Sposito in dry condition varies from 2.86 to 2.92 and in wet condition from 2.90 to 2.99., this range for Tyler and Wheatcraft model was 2.52 to 2.78 and 2.24 to 2.55, for dry and wet conditions, respectively. Results further showed that for the number-size model of Rieu and Sposito the fractal dimension varied from 2.77 to 3.59 in the dry and from 2.35 to 3.18 in wet conditions. These ranges for Mandelbrot model were obtained to be 2.89 to 3.72 and 2.21 to 3.22 for the dry and wet sieves, respectively. The largest standard deviation was obtained for MWD, while the lowest belonged to the mass-size model of Rieu and Sposito. The obtained results further indicated that by increasing the fractal dimension, aggregate stability decreases and aggregate instability tend to increase. It can be then concluded that by using fractal dimensions one can more precisely describe the aggregate stability compares to the classical methods.