جستجوی مقالات مرتبط با کلیدواژه « depth » در نشریات گروه « کشاورزی »

Recently, the effects of climate change on the hydrological cycle and regime have become an important research topic. The results of atmospheric general circulation models (GCMs) together with hydrological models are used to determine the impacts of climate change on hydrologic regime. The daily minimum and maximum temperatures, rainfall and sunshine hours of the Shiraz synoptic station were simulated using the LARSE_WG6.0 statistical model. The efficiency of the model for simulating climate variables was determined using historical data of Shiraz station. To investigate climate change on runoff, two scenarios of the HadGEM2-ES model for two periods were downscaled using the LARSE_WG model. In the next step, runoff was simulated using the SWMM model and its results were compared with the measured runoff. For this purpose, 2 events were used for calibration and one event for validation. Based on coefficient correlation (R), root mean square error (RMSE) and Nash-Sutcliffe efficiency (NSE), the model has a suitable efficiency for simulating runoff. Then, LARSE_WG downscaled data were used in SWMM model and the runoff changes in future periods compared to present. According to RCP4.5 and RCP8.5 climate scenarios, precipitation will increase from 16.10 to 8.88% in 2021-2040 and 14.49% and 19.73% in 2061-2080. Therefore, assuming no change in landuse in Shiraz district 8, the volume of runoff will increase from 13.35 to 21.48 percent.

One of the main goals of spatial analysis of precipitation at area is to reach the standard project storm (SPS) for that area, through which can be reached the standard project flood (SPF). This analysis includes the characteristics of rainfall depth at a certain area and for a specific duration. Relation between depth and rainfall area which called depth-area-duration (DAD), is shown usually by set of curves that each shows different duration of rainfall. Using these curves, a reduction factor is determined for specific area and is applied to adjust the average point rainfall related to frequency of this project. The present study carried out under topic of investigation and map of depth- area- duration in Lorestan, in an area over 28559/5 Km2 in west part of country.

Weak coefficient of correlation is shown meaningfulness of the relation between rainfall and altitude in different time base. this is resulted from different reasons such as extension of area, lack of transmittal and number of suitable weather stations and different extension and tension of mountain than rain flaw. Considering above points cause those other methods of drawing precipitation maps include interpolation or geostatistical methods including, spline, IDW, kriging and Co-kriging were used.

Weak coefficient of correlation is shown meaningfulness of the relation between rainfall and altitude in different time base. this is resulted from different reasons such as extension of area, lack of transmittal and number of suitable weather stations and different extension and tension of mountain than rain flaw. Considering above points cause those other methods of drawing precipitation maps include interpolation or geostatistical methods including, spline, IDW, kriging and Co-kriging were used.

The results show that to preparing precipitation maps of selecting storms, simple co- kriging (SCK) is a suitable method to calculate the amount of rainfall of selecting storms in lorestan province. So the above way is used for preparing precipitation maps. Resulted from investigation of surface reduction factor of rain fall shows that in time duration 12 and 48 hrs with the increase of each 5000 surface reduction factor reduces for 0.1 in 24 hrs duration within 18000 Km2. This coefficient has a slow decreasing trend and then that is similar to 12 and 48 hrs rainfalls. Assessing the daily rainfall statistics of some of rain gauge stations in somewhere of the province by the Meteorological Organization and the Ministry of Energy, shows that sometimes there is a significant difference between the perception rates recorded by these organizations. Therefore, in order to eliminate the existing defects, it is suggested that the stations occupied by these organizations and their monitoring status be periodically evaluated by the experts of the relevant organizations and possible defects be prevented.

Over the past years, eutrophication due to human activities has been recognized as a major ecological problem for the coastal areas, which in turn leads to significant changes in physicochemical and biological factors. The aim of the present study was to determine the eutrophication status of the Gorgan Bay, which was evaluated using the Carlson index as one of the efficient methods for assessing the eutrophication status of water bodies. The Gorgan Bay is located in the southeast of the Caspian Sea. The sampling was carried out in 23 stations with three replications seasonally from summer 2018 to spring 2019. Nitrate, phosphate, chlorophyll α, depth, and transparency were measured in each sample. Carlson's index in terms of chlorophyll α showed that the bay is in the eutrophic status in three seasons including summer, autumn, and winter (with the numbers 53.48, 53.69, and 53.67, respectively), and the mesotrophic status in spring (with the number 42.75). In terms of phosphate concentration, the bay was eutrophic in autumn and winter, and in summer (69.22 and 55.17) and oligotroph in spring (26.75 and 35.30), while in terms of transparency the bay was categorized as eutrophic in all seasons (63.33, 61.61, 69.93 and 61.58, respectively). In general, the results showed that the bay is in the range of mesotrophic to eutrophic status and therefore, more conservation management of this unique ecosystem is essential.

The present study estimated relative frequency index of Purpleback flying squid and Oman cuttlefish also evaluated the effect of depth, distance, and time of capture (before & after noon) on them. Sampling was in the west of the Gulf of Oman at the spring of 2019. The depth of the Gulf was 208 to 285 meters. The vessel used was an industrial Myctophid trawler and the sampling gear was a rope trawl that operated with the fishing technique in a water column (the bottom panel was maximum 6 meters higher than the bottom of the Gulf). According to field observations, the average catch per unit of effort index in Purpleback flying squid and Oman cuttlefish was estimated to be 7584.22 and 1345.066 gram / hour based on weight and 19.062 and 18.250 number / hour based on number, respectively. Based on the selected models, the variables of depth and distance had a significant effect on catch per unit of effort for Purpleback flying squid (P<0.05). With increasing depth and distance, the catch per unit of effort for squid increased. However, based on the results, no significant effect of the studied variables on the relative abundance index of Oman cuttlefish was observed, given the lack of sufficient research on this theme and the discard caught of these species in Iranian waters, more extensive research to manage their stock in the Gulf of Oman is a need..

The habitat suitability model is a common method for assessing the habitat needs of fish in freshwater systems. The aim of this study was to investigate the habitat suitability of Kiabi loach (Oxynemachilus kiabii) in the Dinor River, Kermanshah province, Iran. For this purpose, 7 stations along the Dinor River were sampled in April 2017 using an electrofishing device. In addition to recording fish abundance, environmental characteristics including water temperature, water velocity (m/s), depth (cm), river width (m), average bedrock diameter (cm), alkalinity (pH), electrical conductivity (EC), and total dissolved solids (TDS) was recorded at each station. The habitat suitability index was evaluated according to the relationship between environmental variables and fish abundance. Based on the results, the most desirable habitats for O. kiabii in the Dinor river are areas with a river width of 6-7.2 m, river depth of 26-34 cm, water flow velocity of 0.17-0.45 m/s, water temperature of 22-23 °C, EC values of 300-350 μS/cm, pH values of 7.80-8.92, TDS values of 580-610 mg/l, and average diameter of bedrock less than 5-6 cm. In the present study, the value of habitat suitability index (HSI) for O. kiabii was determined to be 0.51. Overall, the results showed that the Dinor River, in terms of habitat characteristics, compared to other fish species (such as Alburnus sellal), has a moderate suitability for the Kiabi loach. This indicates that the expansion of human activities in the Dinor River basin has disrupted the habitat range of this endemic species. Therefore, conservation priorities need to be considered by fisheries experts and managers in order to conserve and manage the stocks of this valuable species.

The rate of static pressure drop of air passing through the mass of agricultural products is one of the basic data for selecting the fan used in aeration or dryer systems. In this study, the amount of static air pressure drop through the masses of Agria and Marfona cultivars was measured using a simulator device consisting of an air compressor, a rotameter, a cylindrical bin, and a U-shaped barometer and their regression relationship with some parameters such as depth of mass, moisture content and percentage of unwanted materials (soli &, etc.) were defined by using of Shedd’s model. According to these tests: As the air velocity increases from 0.085 to 0.53 (m/s), the static air pressure drop increases too. By each 25 cm increase in the depth of Agria and Morfona potatoe piles, the static pressure will be dropped by 1.49 and 1.53 times respectively. With each 2% increase of soil and other impurities in the potato pile, the rate of air pressure drop in the potato mass of Agria and Marfona increases 1.36 and 1.33, respectively. At similar airflow rates, potatoes with higher moisture content showed fewer static pressure drops. The airflow resistance of the Agria potato piles measured 4 to 6% more than the Marfona cultivar, at the same condition.

Dinor River is one of the tributaries leading to Gamasiab River in Tigris river drainage and one of the habitat of Kermanshah stone loach (Sasanidus kermanshahensis). The river has been affected by human activities such as agriculture. In this study, a total of 168 specimens were collected from 21 stations of Dinor River for the study of Kermanshah stone loach’s habitat suability index. For this purpose, the river characteristics, including water velocity (m/s), water depth (cm), altitude (m), river width (m), bedrock index, and average bedrock diameter (cm) were recorded at each station. The habitat suitability index was examined according to the relationship between environmental variables and species abundance. The results showed that river width and water velocity are directly related and altitude, water depth, and bed index were inversely related to the abundance of S. kermanshahensis. The HSI index with a value of 0.497 showed that this river has moderate suitability for this species. Also, the results indicated that the selected habitat of S. kermanshahensis includes areas with high water velocity due to the need for adequate oxygen, sand-mud bed, high width, low altitude, and shallow depth. The findings can be used to manage and protect the reserves of this species, which is part of the country's natural heritage..

Preferential flow is formed through large pores in soil. The flow transmission in the large pores is faster than the regular parts of soil. Therefore, the effect of preferential flows, which are created by factors such as cracks, should be assessed on the distribution of moisture profile. The analytic, empirical and quantitative models can be used to assess the various modeling parameters and water distribution in soil in various environmental conditions, in order to save money and time. Hydrus-2D model is one of the potent models for stimulating the movements of water and salts in soil, based on the Richards' equation numerical solution. Nowadays, the use of deficit irrigation methods is increasing due to the water resources shortage. In addition, the preferential flows creating in farms have an important role in water and contaminant transport. Therefore, the purpose of this study is to investigate the effect of pore geometry (with different width and depth) on soil moisture distribution in soil profiles, at different levels of irrigation. To investigate the effect of preferential flow on soil moisture profile, sandy and sandy loam texture (in the preferred area) was used. In this study, column with a diameter of 160 mm and a length of 350 mm were applied. The soil columns were filled in layers. The method of Wang et al. (2013) was employed to establish the preferential flow. Due to this method, the columns were placed in the water container from the floor and a pipe with a diameter of 16 mm and a height of 350 mm was placed in the center of the column. The soil was poured in layers around a 16 mm pipe and after each layer a little water was sprinkled on the soil surface. After filling the soil column, the 16 mm tube was gently pulled out of the larger column, and then the 16 mm tube was filled with find grain sand (treatment T1). Irrigation levels of 120, 100, 80 and 60% were selected (T120, T100, T80 and T60, respectively). The initial soil moisture of the treatments was the lower limit of readily available water. The T80 and T60 treatments had 20 and 40% less irrigation volume and T120 treatment had 20% more than the T100 treatment, respectively. The RETC software was used to estimate the Van-Genuchten coefficients. To calibrate the Van-Genuchten equation coefficients, soil moisture profiles were used in Hydrus. The model initial conditions were the initial soil water content at different depths. To compare the amount of simulation and observational values, the root mean square error (RMSE), NRMSE and correlation coefficient (r) were used. The Hydrus-2D software was employed to investigate the soil moisture distribution under different geometric shapes of the preferential flow (PF). The PF’s geometries created in V-shaped pores from the soil surface to deep where the top-width was 0.5, 1 and 1.5 cm (B0.5, B1, B1.5) and the total depth was 10, 20 and 30 cm (H10, H20, H30). In this study, the soil moisture was simulated with the Van-Genuchten coefficients. The results showed that the water content with the coefficients was estimated with a good accuracy. The minimum and maximum correlation coefficients were 0.83 and 0.95, respectively. The average percentage of moisture error at depths of 0 and 20 cm in the T60 and T120 was about 2% and the moisture content of the model was slightly different from the observed values. According to the research results, by increasing the depth of cracks, the amount of soil moisture in the soil surface decreases, compared with the non-cracked soils. Thus, the water transfers to the lower depths and consequently increases the soil moisture. In the deficit irrigation condition, the presence of preferential flow causes a more uniform soil moisture distribution in the soil profiles; But, the more irrigation level/ time increases the more deep percolation losses that finally decreases the irrigation efficiency. Some research result showed that PF in most farms has caused increasing deep percolation losses about 71%. Playan and Matthews (2004) evaluated irrigation efficiency by changing irrigation management. Their results showed that with decreasing irrigation time, irrigation water use efficiency increased from 44% to 71%. Also in their study, the soil moisture content at the soil surface in T60, T80, T100 and T120 treatments in the presence of the PF with depth of 30 cm (H30) and a width of 1.5 cm (B1.5), decreased about 11, 9.3, 9.2 and 9.1%, respectively, where the moisture at the depth of 20 cm increased about 24.1, 25, 27 and 21.1%, respectively. In our research, the results for different PF forms in T120 and T80 showed that the presence of a crack with low depth (h=10 cm), for all width scenario (B=0.5, 1 and 1.5 cm), had not a significant effect on the distribution of soil moisture profiles. For the PF with H=20 and H=30 cm, the effect of the crack width (B) on the soil moisture distribution in T80 became more noticeable at a distance of 3.5 cm from the center of the column. The amount of soil moisture in the soil profile did not differ much for the different crack’s width in T120 treatment, but with increasing the depth of the cracks (H20, H30), the moisture distribution at different depths became more uniform. The results of this study showed that with increasing the depth and width of the preferential flow, the moisture distribution is more uniform and the higher the irrigation level, the more uniform distribution is. This process decreases surface soil moisture and causes water flow to the lower depth in comparison with the non- preferential flow condition. For example, in the soil surface in treatments with irrigation levels of 60, 80, 100 and 120%, the amount of soil moisture at the soil surface, under preferential flow conditions with a depth of 30 cm and a width of 1.5 cm, was decreased around 11, 9.3, 9.2 and 9.1 %, respectively and it caused increase in the soil moisture at depth of 20 cm with 24.1, 25, 27 and 21.1 percent, respectively.

In this research, the status of water productivity for wheat production and strategies to increase water productivity in different quantitative conditions of water was determined and analyzed in the irrigation district of Sistan Dam. In this regard, the SWAP simulation model was calibrated and validated by considering the current water resources operation, various quantities of irrigation water, and use of field information. Water production functions were used to determine the irrigation schedule (time and depth) for wheat crop. The results of field measurements in the crop year 2016-2017 in the irrigation district showed that farmers irrigate wheat on average four times in the current conditions. Farmers' average crop yield and water productivity were about 1450 kg/ha and 0.41 kg/m3, respectively. These results show that available water is not appropriately used and should be addressed with practical solutions to improve water productivity. The validation and calibration results of the SWAP model also showed the high accuracy of the model in the case study. The results of different management scenarios of eliminating some irrigation shifts compared to the existing conditions indicated that, although there was no significant difference in water productivity, crop yield decreases about 37%. The results of evaluating the scenarios of reducing the depth and frequency of irrigation (using 640 mm per season and applying 40 mm at each shift) showed that, with reliable and timely water supply and more frequent irrigation, water productivity could be increased by 30% compared to the baseline scenario; and crop yield can be doubled. In these scenarios, the presence of adequate moisture in the plant's root zone increases the yield, and the amount of deep percolation is greatly reduced. The amount of water used by farmers is excessive for various reasons. Therefore, it is recommended to train farmers on how to improve irrigation and crop management according to the water available in the irrigation district, so that they can distribute water according to the real needs of the plant and irrigate at the right time and sufficient quantity.

Copper is an essential micronutrient to plants, which it`s deficiency is common in calcareous soil. Most of the soils are calcareous in Iran, therefore farmers and gardeners may observe the deficiency of this element during the growing season. Given the importance of copper in the nutrition of date trees, especially in calcareous soils, a better understanding of the mechanism and kinetics of copper release from the soil can provide useful information about the factors affecting the bioavailability of this element. Therefore, this study was conducted to investigate the influence of depth and canopy of three palm cultivars on kinetics release of copper. For this purpose, soil samples were collected from three depths of 0-20, 20-40 and 60-40 cm and two locations (under canopy and outside the canopy) with three replications, for three cultivars of date palms; Shahani, Ghasab and Halvan. Extraction was performed in eight different time periods with ammonium bicarbonate Diethylene Triamine Penta acetic acid (AB-DTPA). Results showed that the power function, simple Elovich, and parabolic diffusion were the best fitted models for describing Cu release. The pattern of copper release was fast during the first two hour and decreased at subsequent time. The results of this study indicating the positive effect of date palm canopy on the availability and rate of copper release from calcareous soils. So that the rate of copper release related to the depth of 40-60 cm of the soils under the canopy was higher than the one in the same depth outside the canopy, which can be attributed to root exudations and pH reduction. Among the three cultivars studied in this research, Shahani cultivar had the highest amount of copper release.

The Easiness of mining from the rivers and its low cost have increased use of these resources. In the present study, the effects of pit migration and development on the bridge inline piers were investigated experimentally. The circular and sharp rectangular shapes of the piers have been employed in this study. The results showed that the pit holes are developed to the downstream and upstream bridge piers in order to achieve sediment balance, which causes piers scouring at downstream and upstream. Also, the development of the holes towards upstream pier is more than the downstream pier. Regarding to aero-dynamical shape of the rectangular sharp nose bridge, the magnitude of the scouring hole at the up and downstream is reduced 24.5 and 31.55% respectively as compared to circular piers. Finally, the empirical relationships related to the maximum length and depth of scouring were derived. By using these relationships, the geometric and effective statistical parameters on the pier scouring, as well as the relative error percentage and RMSE of the obtained functions were evaluated and the depended graphs were depicted. It was found for both sediment dimensions, by reduction of the hole depth and Fr number, the dimensionless parameter of the H/y(the pit holes depth to flow depth) is decreased and the L/y and B/y (the pit holes length and width to flow depth) parameters are increased. Finally, the parameters affecting the maximum length and depth of the pit scouring were identified and introduced for both sharp piers.

Vertical distribution of seed, Plant residual, Granule fertilizers and other chemical complexes in depth of soil influence of tillage with various implements is one of the important issues in agronomy. So, an experiment done with SeedChaser model to recognize the patterns of seed vertical distribution in soil (0-18 cm) with 15 types of tillage implements in simulation study and 9 of ones in field experiment. Results showed that patterns of seed vertical distribution were different and it depends on infiltration depth of implements in soil, curve degree of knife and soil bulk of be moved. Spader, Rigide tine, moldboard, and rotovator buried seeds in below 10 cm depth of soil, although Rotary hoe, Drill, Residual management, Para plow and Strip tillage implements buried seeds in shallow depths (02 cm) and was between 2-8 cm in others. Also, results released that critical depth for D90 (90% of seeds in a certain depth) ranged 14-18 cm for Moldboard, Rotovator and Spader while was 0-10 cm for other implements. Prediction results recognized that the model predicted seed vertical distribution in a good mood which the highest dispersal related to chisel plow and the lowest observed in tillage with Moldboard

Soil hydraulic conductivity (K) is an important parameter in designing drainage systems and estimating water flow in soils, Although some methods are suggested for direct measurements of saturated hydraulic conductivity (Ks) but they are usually time consuming and costly. Pedotransfer functions (PTFs) is a valuable tool and indirect method to predict the Ks from the available soil data. The purpose of this research was to derive the best PTF that can predict saturated hydraulic conductivity values from the available parameters in Abadan. After basic studies drainage include logging (determination of texture, color, resistance to drilling, stickiness and plasticity) and determination of watertable, saturated hydraulic conductivity was measured on the soil columns using Ernest auger hole method then by exact semidetailed soil survey, morphological characteristics such as structure were specified as well, some physical and chemical properties of soil were measured, Geometric mean diameter (dg) and geometric standard deviation of soil particles (dg) were calculated by the exist equations. The multiple linear and nonlinear regression methods were used to develop the pedotransfer functions by using soil structure class, geometric mean diameter (dg), porosity and depth. From these four pedotransfer functions which were derived , the results indicated that accuracy of the derived PTF with R2=0.955 can predict the saturated hydraulic conductivity well from these four parameters and it can be used for primary estimation in order to design of irrigated poject.

Soil water repellency (SWR) is a soil characteristic that creates strong resistance to water penetration and decreases infiltration time from a few seconds to hours, days or weeks. The undesirable consequences of SWR have received interest from the scientific literature. However, the SWR has some beneficial aspects like increasing aggregate stability. Although several authors have reported the soil organic carbon as the origin of SWR but it seems only some parts of the soil organic carbon are hydrophobic and are involved in SWR. Thus, the aims of this study were: (a) to determine which soil organic carbon pools are linked with SWR, (b) to assess the impact of SWR on aggregate stability and (c) to determine which vegetative cover produce more hydrophobic organic compounds and contribute to SWR.
Soil samples were collected from the 0-5, 5-10 and 10-20 cm layers of the lands under different forest tree species including Populus caspica, Oak (Quercus castaneifolia), Alder (Alnus glutinosa), Bald cypress (Taxodium distichum), Loblolly pine (Pinus taeda) and Juniper (Juniperus polycarpos). The soil samples were analyzed for organic carbon content, pH, water repellency and aggregate stability (MWD) and were also separated to different organic matter pools based on particle size fractionation. The experimental variables were soil depth and kinds of vegetative cover and the data obtained from the soil samples were analyzed statistically by a two-way analysis of variance (ANOVA) using a factorial experiment with completely randomized design and 30 replications. Also Pearson linear correlation was used to indicate the relationships between the measure characteristics.
The vegetative covers and soil depths had significant impacts on SWR and the measured soil properties. The highest water drop penetration time (WDPT) was measured for the surface soil layer (0-5 cm). About 13.33 and 3.33 % (n=30) of the samples collected from the soil surface under P. taeda and T. distichum had the more than one hour WDPT (extremely repellent class). In contrast, the lowest SWR classes were mostly observed under the vegetative covers of P. caspica, Q. castaneifolia and A. glutinosa which were broadleaves tree species. The water repellency decreased with soil depth and 82.22% of the soil samples collected from the 10-20 cm layer of all tree species (n=180) determined as wettable soil (WDPT The strong correlation between SWR and the organic carbon content of the sand fraction indicates that this fraction contains organic compounds that contribute to SWR. Increase in soil pH and extent of decomposition of soil organic matter, however changes the solubility of soil organic matter and decrease SWR. As the soil aggregation depends on the total soil organic carbon content, the stability of aggregates is affected by hydrophobic fraction of soil organic carbon. Despite the extreme SWR in coniferous, Considering the undesirable quality of soil under coniferous trees such as low pH, MWD and organic carbon content, it is recommended to use discretion in the selection of these species for afforestation and reforestation projects.

A free overfall offers a simple device for flow discharge measuring by a single measurement of depth at the end of the channel yb which is known as the end depth or brink depth. When the bottom of a channel drops suddenly, the flow separates from sharp edge of the brink and the pressure distribution is not hydrostatic because of the curvature of the flow. In channels with subcritical flow regime, control section occurs at the upstream with a critical depth (yc). Although pressure distribution at the critical depth is hydrostatic, the location of the critical depth can vary with respect to the discharge value. So, the end depth at brink is offered to estimate the discharge. A unique relationship between the brink depth (yb) and critical depth (yc), known as end-depth ratio (EDR = yb/yc), exist. Since a relationship between the discharge and critical depth exists, the discharge can ultimately be related to yb. However, when the approaching flow is supercritical, critical section does not exist. Therefore, the discharge will be a function of end depth and channel longitudinal slope.
In current study, an analytical model is presented for a circular free overfall with different flat base height in subcritical and supercritical flow regimes. The flow over a drop in a free overfall is simulated by applying the energy to calculate the EDR and end depth-discharge (EDD) relationship.
End-depth-discharge relationship: The flow of a free overfall in a channel can be assumed that is similar to the flow over a sharp-crested weir by taking weir height equal to zero. It is assumed that pressure at the end section is atmospheric, and also streamlines at the end section are parallel. To account for the curvature of streamlines, the deflection of jet due to gravity, the coefficient of contraction, Cc, is considered. At a short distance upstream the end section, the pressure is hydrostatic. By applying the energy equation between end section and control section which is at upstream the end section, the flow depth at the end of the channel yb in terms of depth at the control section can be determined.
Subcritical flow regime: In this case, the approach flow to the brink is subcritical for negative, zero and mild bed slopes with critical depth at the control section. Using the definition of the Froude number at critical depth, the discharge can be determined. As the explicit relationship between discharge and depth at the brink don’t exist, a relationship should be presented through regression analysis between discharge and yb using the different values of yc over the practical range of 0.01 to 0.84. In this study, below explicit equation is presented for computing Q*(dimensionless discharge) in terms of ( ): Where d is channel diameter, is the ratio of bottom elevation to the channel diameter and . This equation can be used for different values of over the practical range of 0.06–0.6.
Supercritical flow regime: A critical flow occurs upstream of the free overfall under the subcritical approach flow. However, no such critical flow occurs in the vicinity of the overfall under supercritical flow regime. Therefore, the Manning equation for known value of channel bed slope and Manning’s coefficient is exercised to derive the discharge relationship under the supercritical flow regime. Since an explicit equation for discharge in term of yb is impossible, a direct graphical solution for discharge for known end depth, channel bed slope, and ratio of bottom elevation has been provided for supercritical flow regime.
The free overfall in a circular channel with flat base has been simulated by the flow over a sharp-crested weir to calculate the end-depth ratio. This method also eliminates the need of an empirical pressure coefficient. The method estimates the discharge from the known end-depth. In subcritical flows, the EDR has been related to the critical-depth. On the other hand, in supercritical flows, the end-depth has been expressed as a function of the longitudinal slope of the channel using the Manning equation. The mathematical solutions allow estimation of discharge from the known end-depth in subcritical and supercritical flows. The comparisons of the experimental data with this model have been satisfactory for subcritical flows and acceptable for supercritical flows.

Petroleum hydrocarbons are among the major organic environmental pollutants whose toxicity and carcinogenicity effects have raised great concerns while the numerous available physical and chemical methods to remove petroleum hydrocarbons are rarely employed due to their extreme costs and harmful side effects, biological methods, including phytoremediation, have attracted wide attention during the recent years. The current study used sorghum (Sorghum vulgare) and barley (Hordeum vulgare) to decrease petroleum hydrocarbon content of contaminated soil around Isfahan Oil Refinery (Isfahan, Iran). It also assessed the concentrations of petroleum hydrocarbons and petroleum-degrading bacteria at different depths of soil following phytoremediation. Polyvinyl chloride (PVC) pipes (20 cm in diameter and 130 cm long) were employed for phytoremediation. In each pot, hordeum or sorghum seeds were separately sown approximately 1-2 cm below the soil surface. Thirteen weeks after sowing of the plants, soil columns were sampled at 25, 50, 75, and 100 cm depths and concentration of petroleum hydrocarbons and number of oil-degrading bacteria was determined. Statistical analyses indicated the two plants to reduce the concentration of petroleum hydrocarbons to a significantly higher extent (23%-35%) than the control treatment Obviously, such an effect was only detected in depths where plant roots penetrated (especially 0-50 cm), i.e. the absence of roots in deeper parts of the soil column (50-100 cm) was accompanied by lower number of oil-degrading bacteria and higher concentration of petroleum hydrocarbons. Accordingly, future studies are recommended to investigate the efficacy of landfarming and stimulation and injection of oil-degrading microorganisms in eliminating deep soil contamination.

In recent years, production techniques and equipment have been developed for conservation tillage systems that have been adopted by many farmers. With proper management, overall yield averages for conventional and reduced tillage systems are nearly identical. Sometimes, field operations can be combined by connecting two or more implements. Much research has focused on either reducing or eliminating tillage operations to develop sustainable crop production methods. The greatest costs in farm operations are associated with tillage due to greater specific energy requirement in tillage and the high fuel costs. Combined operations reduce both fuel consumption and time and labor requirements by eliminating at least one individual trip over the field. Light tillage, spraying, or fertilizing operations can be combined with eitherprimary or secondary tillage or planting operations. The amount of fuel saved depends on the combined operations. Generally, light tillage, spraying, and fertilizing operations consume between 0.25 and 0.50 gallons of diesel fuel per acre. Fuel savings of 0.12 to 0.33 gallons per acre can usually be expected from combining operations. Eliminating one primary tillage operation and combining one light tillage, spraying, or fertilizing operation with another tillage or planting operation can usually save at least a gallon of diesel fuel per acre. Combining operations has the added benefit of reducing wheel traffic and compaction. To improve the tillage energy efficiency, implementing effective and agronomic strategies should be improved. Different tillage systems should be tested to determine the most energy efficient ones. Tillage helps seed growth and germination through providing appropriate conditions for soil to absorb sufficient temperature and humidity. Tillage is a time consuming and expensive procedure. With the application of agricultural operations, we can save considerable amounts of fuel, time and energyconsumption. Mankind has been tilling agricultural soils for thousands of years to loosen them, to improve their tilth for water use and plant growth and to cover pests. Tillage is a process of creating a desired final soil condition for seeds from some undesirable initial soil conditions through manipulation of soil with the purpose of increasing crop yield.The aim of conservation tillage is to improve soil structure. Considering the advantages of conservation tillage and less scientific research works on imported conservation tillage devices and those which are made inside the country, and considering the importance of tillage depth and speed in different tiller performance, this investigation was carried out. This investigation was carried out based on random blocks in the form of split plot experimental design. The main factor, tillage depth, (was 10 and 20cm at both levels) and the second factor istillage forward speed, (was 6, 8, 10, 12 km h-1 in four levels for Bostan-Abad and 8, 10, 12, 14 km h-1 for Hashtrood) with 4 repetitions. It was carried out by using complex tillager made in the Sazeh Keshte Bukan Company, which is mostly used in Eastern Azerbaijan and using Massey Ferguson 285 and 399tractors and its fuel consumptionwas studied. In this study, the effect of both factors on the feature of fuel consumption was examined. Regarding tillage speed effect for studies characteristic in Bostan-Abad at 1% probability level fuel consumption was effective. The effect of tillage depth has significance at 5% probability level on fuel consumption. The interaction effect of tillage speed and depth on fuel consumption was significant at probability level of 1%. In Hashtrood, the effect of tillage speed was significant on fuel consumption at probability level of 1%, and also tillage depth effect was significant on fuel consumption amount at probability of 1%. The interaction effect of tillage speed and depth on fuel consumption was significant at 1% level of probability. In this study, the effect of both factors on fuel consumptionwas examined. In Bostan-Abad and Hashtroud on the whole, the results indicated that with the increase in the speed of tillage, fuel consumption, was reduced per hectar.The speed of 10 kilometers per hour was the best for this implemented work. Also, with an increasing depth of tillage, the fuel consumption increased.Through an increase in tillage speed, fuel consumption mass reduced at unit level. Moreover, the optimum speed was concluded to be 10km per hour. The best tillage depth using this machine is 10cm.

In recent years, production techniques and equipment have been developed for conservation of tillage systems that have been adopted by many farmers. With proper management, overall yield averages for conventional and reduced tillage systems are nearly identical. Sometimes, field operations can be combined by connecting two or more implements. Combined operations reduce both fuel consumption, and time and labor requirements by eliminating at least one individual trip over the field. Light tillage, spraying, or fertilizing operations can be combined with either primary or secondary tillage or planting operations. Tillage helps seed growth and germination through providing appropriate conditions for soil to absorb sufficient temperature and humidity. Moreover, it helps easier development of root through reducing soil penetration resistance. Tillage is a time-consuming and expensive procedure. With the application of agricultural operations, we can save substantial amounts of fuel, time and energy consumption. Conservation tillage loosens the soil without turning, but by remaining the plant left overs, stems and roots. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. Bulk densities above thresholds indicate impaired function. Bulk density is also used to convert between weight and volume of soil. It is used to express soil physical, chemical and biological measurements on a volumetric basis for soil quality assessment and comparisons between management systems. This increases the validity of comparisons by removing the error associated with differences in soil density at the time of sampling. The aim of conservation tillage is to fix the soil structure. This investigation was carried out considering the advantages of conservation tillage and less scientific research works on imported conservation tillage devices and those which are made inside the country, besides the importance of tillage depth and speed in different tiller performance. This investigation was carried out based on random blocks in the form of split plot experimental design. The main factor, tillage depth, (was 10 and 20cm at both levels) and the second factor, tillage speed, (was 6, 8, 10, 12 km h-1 in four levels for Bostan-Abad and 8,10,12,14 km h-1 for Hashtrood) with four repetitions. It was carried out using complex tillage made in Sazeh Keshte Bukan Company, which is mostly used in Eastern Azerbaijanand using Massey Ferguson 285 and 399 tractors in Bostab-Abad and Hashtrood, respectively. In this investigation, the characteristics of soil bulk density were studied in two sampling depths of 7 and 17 centimeters. Bulk density is an indicator of soil compaction. It is calculated as the dry weight of soil divided by its volume. This volume includes the volume of soil particles and the volume of pores among soil particles. Bulk density is typically expressed in g cm-3. In this study, the effect of both factors on the feature of the soil bulk density at the sampling depth of 5-10 and 15-20 cm was examined. In Bostan-Abad, regarding tillage speed effect for studies characteristics at 1% probability level on soil bulk density was effective. The effect of tillage depth on the soil bulk density was significant at 5% probability level. The interaction effect of tillage speed and depth on soil bulk density was significant at probability level of 1%. Regarding sampling depth effect, the soil bulk density was significant at 5% probability level, respectively. In Hashtrood, the effect of tillage speed on soil bulk density at probability level of 1%, and also tillage depth effect on soil bulk density was significant at 5% level of probability. The interaction effect of tillage speed and depth on soil bulk density was significant at 5% level of probability. Regarding the depth of sampling it was significant on soil bulk density at probability level of 1%. Through an increase in tillage speed, soil bulk density reduces at unit level. In this study, the effect of both factors on the feature of the soil bulk density in the sampling depth of 5-10 and 15-20 cm was examined. In Bostan-Abad and Hashtroud, on the whole, the results indicated that the increase in the speed of tillage, soil bulk density, was reduced and the speed of 10 kilometers per hour was the best for this to implement work. Also, with an increasing depth of tillage, the bulk density increased. Through an increase in tillage speed, soil bulk density reduced at unit level. Moreover, the optimum speed was concluded 10km per hour. Through an increase in tillage depth, bulk density and soil humidity increase accordingly. The best tillage depth using this machine is 10cm.