Research Paper
R. Montaghami Rad; E. Ahmadi; S. Zarif Neshat
Abstract
Introduction Storage conditions of product after harvest and during storage are important factors that affect the quality parameters of the products such as color and mechanical properties. The observance of effective issues on the fruit quality, ...
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Introduction Storage conditions of product after harvest and during storage are important factors that affect the quality parameters of the products such as color and mechanical properties. The observance of effective issues on the fruit quality, such as weather conditions, harvest methods, timing of harvesting, temperature of storage and time of storage in maintaining of olive quality and reduce waste, will be very effective. Performance of mechanical testing and mechanical and colorimetric properties of products has an important role in study of qualitative and quantitative properties during storage. Moreover, the study of color and mechanical properties of products, such as olive is necessary, for use in machine design for processing and recovery processing lines in order to reduce waste. Materials and Methods In this study, two types of olives, bitter and sweetened with 1.5% NaOH were harvested and tested to study the effect of storage time on their color and mechanical properties. Olive fruits were stored in two temperatures (environmental conditions with 25 and refrigerator with 4) for 3 months. During this period, experiments were carried out at the intervals of 10 days. Universal testing machine and color meter devices were used for determining the mechanical properties and the color of olives, respectively. By performing a factorial experiment under completely randomized design, the effects of independent factors including storage time, storage temperature and type of olive on the measured properties (shear modulus, shear force, shear energy, modulus of elasticity, penetration force, yield strain, L*, a*, b*, h and c*) were studied. Results and Discussion The results of analysis of variance for shear modulus showed that the main effect of olive type, temperature, time of storage and the dual effects of these parameters were significant at the level of one percent. Analysis of variance for shear force showed that the effect of type, temperature, time of storage and interaction effects of type× temperature and type× time of storage were significant at the level of one percent. The results of data analysis for shear energy showed that the independent parameters, including the type, temperature, time of storage and the effects of dual and triple of their were significant at the level of one percent. According to the graphical results, shear modulus and shear energy of any type of olive on the thirtieth day with the fast steep increased. Water surface evaporation, changes in the texture of olive and a sharp drop in humidity are reasons for the sudden increase of shear modulus and shear energy on the thirtieth day. With increasing time of storage, shear strength and other mechanical properties for bitter and sweet olive increased. This result conformed to the results of Lavassani et al and Nanos et al. Analysis of variance of mechanical properties for olive fruit in penetration test showed that the effect of type and interaction effects of type and time of storage on modulus of elasticity were not significant. Analysis of variance of yield strain showed that the only effect of type was significant at the level of one percent. The results of mean comparison with Duncan test showed that during storage, penetration force and modulus of elasticity for bitter and sweet olive increased. This result correlated with the results of De Castro et al. The penetration force, yield strain and modulus of elasticity of sweet olives during storage were higher in comparison to bitter olives. The penetration force and modulus of elasticity of bitter and sweet samples stored at 4 were higher in comparison to the same sample in temperature of 25. This result correlated with the results of Nanos et al. Analysis of variance of colorimetric properties showed that the interaction effects of type and time of storage on L* were not significant. The effects of type and time of storage on a* and all effects on b* and c* were significant at 1% probability level. The results of mean comparison showed that the brightness and yellow of bitter and sweet samples increased with increasing time of storage compared to the first, tenth and twentieth days. The increase in L* and b* color characteristics correlated with the results of Piga et al. Color characteristics L*, b* and c* of bitter samples in each of the temperatures and days of storage were higher in comparison to sweet samples. In addition, the values of L*, b* and c* of bitter and sweet samples stored at 25 were higher in comparison to the same samples in temperature of 4. Conclusion The results of mechanical and colorimetric tests showed that by increasing the storage time, stiffness, shear strength and other mechanical parameters increased in both types of olives, and the L* and b* values of the samples were higher in comparison to the first, tenth and twentieth days. Bitter and sweet samples stored at 4 temperature displayed higher stiffness, modulus of elasticity, shear modulus, shear force and shear energy values and lower L*, b* and c* in comparison with the same samples stored at 25 temperature.
Research Paper
M. Safari; R. Amiri Chayjan; B. Alaei
Abstract
Introduction Almond (Amygdales Communist L.) is a perennial plant growing in the cold and xeric environments of Iran. The kernels of almond form an important source of energy and protein. An infrared- vacuum dryer with microwave pretreatment benefits includes high mass transfer coefficients and high ...
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Introduction Almond (Amygdales Communist L.) is a perennial plant growing in the cold and xeric environments of Iran. The kernels of almond form an important source of energy and protein. An infrared- vacuum dryer with microwave pretreatment benefits includes high mass transfer coefficients and high quality and the appropriate control on dryer conditions. The aim of this study was to evaluate the effect of air temperature, microwave power and vacuum pressure in drying process of almond kernels and calculate the effective moisture diffusivity, activation energy, energy consumption, shrinkage and color changes. Materials and Methods Fresh almond kernels were obtained from a field located in Asadabad (Hamedan Province), Iran and stored in a refrigerator at 4±1˚C for experiments. The initial moisture content of almond kernels was determined by drying of 10 g of sample in an oven at 105±1°C until constant weight was attained. In this study, the drying properties of almond kernels with moisture content of 47% (d.b.) in an infrared- vacuum dryer with microwave pretreatment were investigated. Three levels of air temperatures (45, 60, 75 °C), three levels of microwave powers (270, 450 and 630 W) and three levels of vacuum pressures (20, 40 and 60 kPa) were applied to perform the experiments. Seven mathematical models were fitted to the experimental drying data of almond kernels. Weight loss of samples was measured and recorded every 20 seconds in microwave dryer and every 300 seconds in infrared-vacuum dryer, respectively. Drying time was defined as the time required to reduce moisture content of samples to 0.1 g of water per g of dry mass. Results and Discussion It was observed that increasing the air temperature and microwave power decreased the time required to reach a certain level of moisture ratio. Also, by reducing the vacuum pressure, drying time for almond kernels was decreased. The results showed that the highest values of coefficient of determination were obtained with the Midilli et al. model. The Midilli et al. model gives higher R2 and lower RMSE and . Therefore, the Midilli et al. model may be supposed to demonstrate the drying behavior of the almond kernels in an infrared-vacuum dryer with microwave pretreatment. The maximum value of Deff (5.33×10-9 m2/s) during the experiments was depending on the air temperature of 75˚C, vacuum pressure of 20 kPa and microwave power of 630W. The minimum value of Deff (8.03×10-10 m2/s) depended on the air temperature of 45˚C, vacuum pressure of 60 kPa and microwave power of 270W. Air temperature had a larger effect on the Deff values of almond kernels drying. Minimum and maximum values of activation energy (Ea) for almond kernels were 28.73 and 51.84 kJ/mol, respectively. The highest and lowest values of energy consumption were 0.26 at air temperature of 45˚C, vacuum pressure of 20 kPa and microwave power of 270W and 0.07 kWh at air temperature of 75˚C, vacuum pressure of 60 kPa and microwave power of 630W, respectively. Increase in inlet air temperature demonstrated an exponential decrease in energy consumption. It was also observed that increase of inlet air temperature, vacuum pressure and microwave power decreased specific energy consumption. Maximum and minimum values of shrinkage were 14.14% at air temperature of 75˚C, vacuum pressure of 60 kPa and microwave power of 630W and 7.78% computed at air temperature of 45˚C, vacuum pressure of 20 kPa and microwave power of 270W, respectively. The results indicated that the shrinkage increased with increasing air temperature, vacuum pressure and microwave power but the effect of air temperature was more than other parameters. Raising the drying temperature increased the movement of water molecules and made increasing the distance between the molecules in the structure of the sample. The highest and lowest values of total color change were 8.85 at air temperature of 75˚C, vacuum pressure of 60 kPa and microwave power of 630W and 2.61 at air temperature of 45˚C, vacuum pressure of 20 kPa and microwave power of 270W, respectively. Results showed that total color change increased with increasing air temperature, microwave and vacuum pressure. Conclusion With respect to the quality indices of shrinkage and color changes, the recommendation is to dry the almond kernels under air temperature of 45 °C, microwave power of 270 W and vacuum pressure of 20 kPa.
Research Paper
N. Hafezi; M. J. Sheikhdavoodi; S. M. Sajadiye; M. E. Khorasani Ferdavani
Research Paper
M. Khorramian; S. Salimpour
Abstract
IntroductionThe area cultivated for wheat is about 550000 ha in Khuzestan province. Limited rainfall conditions and incompatibility of rainfall patterns with wheat crop requirements leads to decreasing of soil moisture and drought stress. Studies have shown that water supply affects the uptake of nutrients ...
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IntroductionThe area cultivated for wheat is about 550000 ha in Khuzestan province. Limited rainfall conditions and incompatibility of rainfall patterns with wheat crop requirements leads to decreasing of soil moisture and drought stress. Studies have shown that water supply affects the uptake of nutrients and nutrient use effeciency. On the other hand, the benefical effect of the application of zinc and potash nutrients under different water stress in Khouzestan is not convenient for farmers. Therefore, this study aimed to determine the effect of drought stress and zinc and potash in silty clay loam soil on yield and water use efficiency (WUE) of wheat. Materials and Methods The experiment was carried out in Safiabad Agricultural Research Center (SARC) of Dezful, Khuzestan during the years of 2008-09 and 2009-10. Before the experiment, initial composite soil samples (0-30 cm & 30-60cm depth) were collected from the experimental plots and were analyzed. The soil was silty clay loam with low organic matter content (OC=0.5-0.75%) and well drained without salinity (ECe=0.27-1.3 ds m-1). On the other hand, micronutrient content of the soil (Fe, Mn and Cu) was higher than the threshold limit. The design was a split plot on a completely randomized block design with three replications. The main plot consisted of three different levels irrigation after 50 (I50), 75 (I75), and 100 mm (I100) evaporation from evaporation pan and sub plots included three levels of fertilizers, without micronutrient (F0), fertilizing based on soil analysis value (F1), and fertilizing basesd on 1.5 times more than the recommended level (F2). Every subplot size was 3.6 m x 10m. The studied cultivar was Chamran and the sowing date was on November with a density of 400 seeds per m-2 and harvested during May in both growing seasons. Soil moisture content was measured before every irrigation in root zone depth using the weighning method. Applied water was measured using flow meter for every treatment. After seed ripening, grain yield per hectare and component yield were measured from the total area of each treatment. Statistical analysis was performed using MSTATC software packages and mean comparison was also performed using Duncan’s Multiple Range Test (DMRT). Results and Discussion The rainfall during plant growth for first and second years was 68 and 221 mm respectively. The mean temperature of Mars and April in the seconed year was 26.1 and 34°C increasing by about 1.4 and 1.9°C compared to the first year. The higher temperature in the second year increased heat stress which led to yield decrease. Irrigation water consumptions in first year for I50, I75, and I100 treatment were 960.6, 804.1 and 682.2 mm and in the second year 182,115 and 95 mm respectively. Higher rainfall in the second year in comparison with the first year led to decrease in number of irrigation events. All the studied parameters except for 1000-grains weight and number of grains per spike were significantly influenced by different levels of fertilizer treatments.The highest yield belonged to fertilizing based on soil test results (F1), (40 kg K per ha, Zinc Sulfat with 200 kg per ha potash) while the lowest yield was found in the control treatment(F0). Cakmak et al. (1996) and Yilmaz et al.(1997) also observed similar responses. A similar trend was observed in the biological yield, number of spike and 1000-grains weight. Increasing rates of K and zinc(up to 40 kg.ha-1) increased the values of crop parameters such as biological yield, number of spike , 1000-grains weight and water use efficiency and thereafter higher levels of K and zinc fertilizer (F2 treatment) led to their decline. Analysis of variance on yield showed that irrigation regime, potash and zinc fertilizer levels were significantly different (p<5%), so that the highest and the lowest yield belonged to I50F2 with 673.5 gr m-2 and I100F0 with 450.3 gr m-2 respectively. Although there was no significant difference between F1 and F2 treatments, increasing the applied fertilizer in I50 treatment increased yield and water use efficiency. On the other hand, applying potash and zinc fertilizer more than recommended levels in soil under moisture stress (I75 and I100), resulted in decreased yield. Conclusion The overall results from this study indicated that it is essential to avoid applying potash and zinc fertilizers over recommended values in soil under moisture stress conditions. Intraction between different irrigation levels in combination with fertilizer showed that I75F1 with yield and WUE, of 6.4 t ha-1 and 1.28 kg m-3 respectively could be recommended.
Research Paper
R. Tabatabaekoloor; R. Hadipour
Abstract
Introduction Sugarcane is one of the most important crops for sugar production. Iran produces about 6800 tons of sugarcane from 88000 ha. Sugarcane is subjected to different loading during harvest and postharvest processes. In order to design and modify sugarcane harvesting and processing machines there ...
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Introduction Sugarcane is one of the most important crops for sugar production. Iran produces about 6800 tons of sugarcane from 88000 ha. Sugarcane is subjected to different loading during harvest and postharvest processes. In order to design and modify sugarcane harvesting and processing machines there is a need to study the physical and mechanical properties of crops and their relationship with the machines. Materials and Methods In this study, the experiments were performed on the sugarcane variety of CP48 supplied from Bahnamir city in Mazandaran province, Iran. The physical properties such as moisture content, diameter and linear density were measured. The relationship between linear density and diameter of sugarcane stem was determined on the node and between nodes and also at different heights of stem. Three mechanisms were developed and assembled to a universal testing machine (ASTM50) to measure the shearing, bending and compressing forces of stem. Experiments were conducted on stem samples of 5 cm length. The sugarcane properties in shear, compression and bending were determined using the related equations. All experiments were conducted at three portions of stem (bottom, middle and up) and two points (node and inter nodes). Data were analyzed using a factorial test based on a completely randomized design. Results and Discussion The results of analysis of variance showed that height (bottom, middle and up) and cutting place (on the node and inter nodes) had significant effects on the shear strength and specific shear energy. The shear strength at the bottom and on the node of stem was higher than other parts of stem, but in reverse specific shear energy at the top of stem was higher. The lower parts of stem due to cellular structure and stiff and thick fibers had higher strength. The specific shearing energy at upper portion and on the node was higher than the bending and compression energy at these points. The maximum amount of shear strength was 2.47 Mpa at the bottom of stem and on the node. The specific shear energy was obtained from the area under force-displacement diagram and increased at the upper parts of stem. The maximum and minimum specific shear energy was 56.1 and 41.8 mJ.mm-2, respectively. Analysis of variance showed a significant effect of height and cutting place on the bending stress, bending energy and bending modulus of elasticity for sugarcane stem. The variation range of bending stress from bottom to the top of the stem was 93.4-79.2 Mpa. The bending energy of sugarcane stem was changed from 72.4 to 110.2mJ.mm-2. It was significantly higher in the bottom of the stem than the upper part of the stem. Also, the bending module of elasticity was changed from 721.3 Mpa at the bottom of the stem to 636.7 Mpa at the top of the stem. The effect of height and cutting place on the compressive modulus of elasticity and compressive energy was significant. There was a difference between compressive forces at different parts of stem. The upper parts of stem had less pressure force due to cavity of inter cellular structures. It was 111.3 Mpa at the bottom of the stem and 44.1 Mpa at the top of the stem. The compressive energy at upper parts reduced significantly as the maximum was 215.3 Mpa on the node and the minimum was 84.5 Mpa between nodes. Modulus of elasticity and bending stress at the upper portion and on the node was higher than other points. The same behavior was observed for compressive energy. The compressive modulus of elasticity showed a significant difference at different parts of the stem but there was no meaningful difference between nodes and on the nodes of the stem. Conclusion The results indicated that shear, compressive and bending properties of sugarcane stem were affected by height on the stem. Shear strength was obtained at the range of 1.53-2.47 Mpa at different parts of the stem. The compressive force at the lower parts of the stem was higher than top of the stem. The maximum compressive module of elasticity was 215.3 Mpa on the node and at the bottom of stem. Also, the maximum compressive energy at the bottom of the stem was 111.3 Mpa and at the top of the stem it was 44.1 Mpa. The range of bending stress was obtained from 79.2 to 93.4 Mpa. In general, the results indicated that the lower parts of the stem due to cellular structure and stiff and thick fibers and the nodes due to complex structure and intersection of fibers have more strength than other portions. Therefore, mechanical properties of sugarcane stem are the function of stem structure at different points.
Research Paper
I. Fazeli Farsani; M. H. Salehi; A. A. Besalatpour; M. R. Farzaneh
Abstract
Introduction In order to achieve sustainable management of water resources, integrated knowledge of water resources and modeling is essential, especially in arid and semi-arid regions where water resources have become scarcer with increasing demands from socioeconomic development and population growth. ...
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Introduction In order to achieve sustainable management of water resources, integrated knowledge of water resources and modeling is essential, especially in arid and semi-arid regions where water resources have become scarcer with increasing demands from socioeconomic development and population growth. In recent years, utilization of hydrological models has been increased to simulate watershed processes for cost saving purposes. Various hydrological models such as soil and water assessment tool (SWAT) have been developed to simulate runoff in the watersheds. In this study, SWAT was used to simulate monthly runoff in Bazoft watershed and the impact of springs discharge on the simulation accuracy was evaluated. Materials and Methods Bazoft is one of the watersheds in Karun basin, (31° 37′ to 32° 39′ N and 49° 34′ to 50° 32′ E) located in northern part of the Karun river basin in southwestern Iran. The area of the watershed is 2168 km2. The main river in the watershed is Ab Bazoft which is joined by the Karun River at the outlet of the watershed. The elevation ranges from 880 m in the south of the watershed to 4200 m on Zardkuh Mountain in the north eastern area. Because the topography is very high in the watershed, the rainfall distribution is different, the average of rainfall in the northern part of the watershed is 1400 mm, while the southern part is 500mm. SWAT was used because the model is a continuous time, spatially and semi-distributed and basin-scale model, in which hydrological processes and water quality are coupled with crop growth and agricultural management practices. Input data include digital Elevation Model (DEM), land use, soil type, meteorological and hydrological observed data were provided. After running the model, a sensitivity analysis was done using the one at time method and SUFI-2 program. For calibration and uncertainty analysis in this study, we used the PSO (particle swarm optimization) algorithm. SUFI-2 and PSO are linked to SWAT in the environment of SWAT-CUP software. We used about two-third of the observed data for calibration and the remaining for validation. The simulation period was from 1992 to 2008. The study period was 1998–2008 for calibration and 1992–1997 for validation. The calibration and validation period results were analyzed at monthly time scale. ). The objective function was the Nash– Sutcliffe coefficient. Two indices, the P-factor and the R-factor, are used to quantify the goodness of calibration performance. The P-factor is the percentage of data bracketed by the 95PPU band, and ideally we would like to bracket all measured data, except the outliers, in the 95PPU band, and the R-factor is the average thickness of the 95PPU band divided by the standard deviation of the corresponding measured variable. Theoretically, the value of P-factor ranges between 0 and 100%, while that of R-factor ranges between 0 and infinity. In ideal conditions when the uncertainty model is perfect, P-factor will be 1 and the R-factor will be 0. Results and Discussion The results showed that the simulated base flow, peak flow, and hydrograph trend by entrance of spring discharge data to the model were more in agreement to the observed runoff data than the model with no spring discharge data. Therefore, the constructed model with the spring discharge data was selected to calibrate the particle swarm optimization (PSO) algorithm. In the sensitivity analysis, the parameters of curve number for moisture condition II (CN2), groundwater delay time (GW_DELAY), deep aquifer percolation fraction (RCHRG_DP), snow pack temperature lag factor (TIMP), the average monthly precipitation during the prediction period (PCPMM), temperature and precipitation parameters and surface runoff lag time coefficient (SURLAG) were the most sensitive parameters in the watershed. Conclusion The calibration and validation results for the base period (1992-2008) showed that the accuracy of the simulations was satisfactory for the discharge and sediment values. The obtained evaluation criteria r-factor, p-factor, and R2 for the calibration period were 1.01, 76% and 0.79 and for the validation period were 0.76, 72% and 0.57, respectively. Therefore, due to the noticeable effects of spring discharge data and the input parameters on the runoff simulation in the study area, it appears that it is essential to consider these factors for the runoff simulation using SWAT in similar mountainous watersheds with high topography.
Research Paper
S. Firouzi
Abstract
Introduction The hazelnut (Corylus avellana L.) is one of the most cultivated and consumed nuts in the world, not only as a fruit but also as a main constituent into a wide range of manufactured food products. Iran after Turkey, Italy, USA, Azerbaijan, Georgia and China, is the world's seventh largest ...
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Introduction The hazelnut (Corylus avellana L.) is one of the most cultivated and consumed nuts in the world, not only as a fruit but also as a main constituent into a wide range of manufactured food products. Iran after Turkey, Italy, USA, Azerbaijan, Georgia and China, is the world's seventh largest producer of hazelnuts. Guilan province is the largest producer of hazelnuts in Iran. More than 90 percent of hazelnut of this province, after removing the initial green shell is sold at low prices. Therefore, design and optimization of harvesting machines and processing equipment to produce this product is important. Thus, the aim of this research was to study the physical, mechanical and nutritional properties of three common hazelnut cultivars in Guilan province of Iran. Materials and Methods In this study, two common local cultivars of hazelnut in north of Iran (Gerd and Badami), and an improved variety namely Keshavarzi were considered for all experiments. Experimental samples were supplied from Eshkevarat region as the major hazelnut producing part of Guilan province. All physical, mechanical and nutritional properties of both the hazelnut and kernel samples were measured and computed at moisture content of 2.3–3.3% dry basis. Nutritional properties including crude protein, oil, crude fiber, ash, dry matter, carbohydrate and some minerals, i.e. N, P, K, Mn, Fe, and Zn contents of hazelnuts, were measured based on the standard methods. All nutritional and mineral data were analyzed through a completely randomized design with three replications. Physical properties including dimensional properties, bulk and true densities, porosity, natural angle of repose, terminal velocity, and coefficient of friction on plywood structural surface and galvanized iron sheet were measured based on the standard procedures. All physical data were analyzed through a completely randomized design with five replications. Mechanical properties including rupture force, deformation and energy absorbed at rupture point along with the hardness of nuts were determined by applying force to three major perpendicular axes of all nut samples. The energy absorbed for rupture nuts was determined by measuring the area beneath the strain-stress curves and hardness of nuts was computed as the ratio of rupture force to the corresponding value of deformation at rupture instant. All mechanical data were analyzed through a completely randomized design with five replications. Results and Discussion According to the variance analyses, there were significant differences between the hazelnut cultivars in terms of crude protein and fiber, ash and carbohydrate contents (pStudy of the physical properties showed that there were significant differences among all dimensional characteristics of the hazelnut cultivars and their fruits. All dimensional characteristics of hazelnut cultivars were significantly higher than those of their fruits. All linear dimensions of Keshavarzi hazelnut cultivar were significantly more than those of local cultivars of Badami and Gerd, while there were no significant differences among length and width of Keshavarzi cultivar and Badami local cultivar. Bulk density, porosity, dynamic natural angle of repose, terminal velocity, and static coefficient of friction on plywood sheet of the hazelnut cultivars were found to be statistically significant at five percent level and p<0.001, but there was no significant difference among true densities of cultivars. There were significant differences between values of bulk density, dynamic natural angle of repose, terminal velocities, and coefficient of friction on plywood structural surface, but no significant differences were seen for true density, porosity, and coefficient of friction on galvanized sheet. Differences among the majority of physical characteristics of hazelnut cultivars and their fruits can be used in design and adjustment of harvesting and processing equipment. Different data were recorded for mechanical properties in various axes of all hazelnut varieties. In more spherical cultivars, the mechanical properties in three dimensional axes were close to one another. The data of rupture force, deformation and energy absorbed at rupture instant, and hardness of nuts can be used for design and adjustment of hazelnut crackers. Conclusion There were significant differences between a large number of physical and mechanical properties of three common hazelnut varieties in Guilan province, Iran. The differences among the engineering characteristics should be used in design and optimizing of hazelnut machineries and processing equipment. The results showed that the improved hazelnut cultivar of Keshavazi had no considerable superiority to landraces cultivars of Gerd and Badami in terms of nutritional and mineral contents. Therefore, it is essential that along with the physical superiority of alternative hazelnut cultivars, their nutritional and mineral advantages be considered by the agricultural experts in Guilan province, Iran.
Research Paper
A. Mradani; N. Dibagar; A. Modares Motlagh
Abstract
Introduction Simulation of tire- soil models have called attention so far when compared to the expensive and time consuming experimental tests. Materials and Methods: To simulate the model, first the soil and different components of tire were designed separately. To design a research model, soil was ...
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Introduction Simulation of tire- soil models have called attention so far when compared to the expensive and time consuming experimental tests. Materials and Methods: To simulate the model, first the soil and different components of tire were designed separately. To design a research model, soil was considered as a single-layer material with a complete elastic- plastic behavior. Its elastic parameters such as Young’s modulus (E), potion ratio (ѵ) and two plastic parameters; friction angle (φ) and cohesion (c) were obtained through tri- axial and direct shear tests, respectively. The tests revealed that soil internal friction angle, cohesion and density were obtained at 36°, 0.003 kg/cm2, and 1600 kg /m3, respectively. The soil profile dimensions were considered as 3×1.2×2 so that there would be no impact on the results or tire position. The tire used for test belonged to a tractor tire type of 220/65 R 21 with 36 cm in width and external diameter of 80 cm with a radial structure, manufactured by Good Year company. Since in simulation of tire ignoring the details of tread design has a negligible impact on large deformations and dynamic loading of tire, the simulated tire in this research was simplified to include tread, carcass, and rim. To design the tread of tire, the incompressible hyper- elastic material features, with Mooney – Rivlin coefficients were considered. To design the internal rubber of the tire model, which includes the belt and carcass, the boosted multiplied elastic approach was used. The dimensions of the modeled tire were compatible with a real one. From the symmetric point of view, only the half of the tire was simulated and dynamically analyzed which decreased the running time. A reference point was defined in the center of the tire to let the speed and load to be exerted through the point. According to mobility of the tire, the torque of every test based on its acceleration was considered on axel (connector) and the movement was measured from two separate points. It is worth to note that the boundary conditions, loading, and material characteristics should be entered in ABAQUS software close to the real conditions. The experimental tests were conducted at different levels of travelling speed (0.4, 0.8 and 1.2 ms-1), dynamic load (2000, 3000 and 4000 N) and depth (0.1, 0.15 and 0.2 m) with measuring the soil vertical stress. The experimental tests of this research were performed in Urmia University using the soil bin testing facility. The system includes various sections such as soil bin in dimensions of 22×2×1 m, carriage, soil processing equipment, dynamic system, evaluation tools, and controlling systems. In order to start data acquisitioning and to supply required power for wheel carriage, an industrial three phase electromotor with 22 kW (30 hp) was used. Analysis of variance was performed using SPSS version 20. Results and Discussion To assess the performance of driven tire-soil model, numerical results were compared with preliminary experimental data. The comparison showed a reasonably good agreement between the simulated and measured soil vertical stress at the tire-soil interface under three different levels of forward speed, dynamic load and depth. Using both methods, the increase of speed led to the reduction in soil vertical stress at different combinations of dynamic load and depth. When tire speed increases, the time during which tire makes contact with soil surface decreases. Therefore, tire dynamic load cannot be transferred into the soil layers completely. Increasing the amount of tire vertical load led to the increase of soil vertical stress but the effect of dynamic load variations on soil stress at different depths was not in a similar manner. It was inferred that the effect of all independent variables as well as their interactions on soil vertical stress was significant. Conclusion In all combinations of vertical load and forward speed, the results of both numerical and experimental tests were close to each other in three different levels of soil depth, so that, driven tire _soil finite element model of this study can be considered as a model with a reasonable accuracy to evaluate tire-soil performance in different operating conditions. In all combinations of dynamic load and forward speed the results of both tests at three different depths were close to each other.
Research Paper
A. Fathi Gerdelidani; H. Mirseyed Hosseini; M. Farahbakhsh
Abstract
Introduction Phosphorus deficiency is one of the major problems of calcareous soils in Iran and based on current statistics more than 70 % of all soils in Iran are under critical P levels of 15 mg kg-1 (51). Previous research results show that application of organic matter increases P availability (46) ...
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Introduction Phosphorus deficiency is one of the major problems of calcareous soils in Iran and based on current statistics more than 70 % of all soils in Iran are under critical P levels of 15 mg kg-1 (51). Previous research results show that application of organic matter increases P availability (46) and changes the P distribution between various forms in calcareous soils.The aim of this study was to evaluate the effects of different levels of spent mushroom compost and sugar cane bagasse biochar as agricultural by products or crop residues on availability and phosphorus fractions in a calcareous soil from Karaj (Alborz provience, Iran). Materials and Methods The soil for the experiment was obtained from 0-30 cm depth of Agriculture Faculty farm of Tehran University at Karaj. Some physical and chemical properties were determined using standard methods (table 1). The spent mushroom compost (SMC) was from Malard mushroom factory and Sugarcane bagasse was from a farm in Khozestan. The Biochar (B) was prepared from the raw material heated to 500 degree celcius inside furnace for 3 hours. Some basic properties of SMC and biochar were also determined (table 2). The experiment was conducted in a completely Randomized design with 5 treatments, and 3 time periods with three replications of each treatment. Treatments included 2 biochar levels B1, B2 (15 and 30 Mg ha-1 respectively), 2 spent mushroom compost levels SMC1, SMC2 (20 and 40 Mg ha-1 respectively) and the control treatment (C). For each treatment, 300 grams of air dried soil was used in small pots and after application of materials and mixing they were moist to field capacity and kept inside an incubator at 28-29 ˚C for a period of 120 days. At 14, 60 and 120 days soils were sampled for analysis (by eliminating the pots). Soil properties such as pH, available P, water soluble P and various inorganic P fractions (23) were determined in soil samples. Statistical analysis of the data was done using SAS software and mean comparison using LSD method was also performed. Results and Discussion Results showed that the available P in the control increased significantly (p<0.01) from 8.8 mg kg-1 of soil to 17.8, 28.8, and 12.8 mg kg-1 of soil in the SMC1, SMC2, and B2 respectively, which had an increasing trend with time in B2, but in the SMC2 it was highest on 60 days. This can be related to higher microbial activity after application of organic materials and release of P after organic matter decomposition (22). The water soluble P also increased from 2.1 mg kg-1 in the control to 2.8 and 2.7 mg kg-1 in the SMC2 and B2 respectively, which showed an increasing trend over time for SMC2 (p<0.01). In the SMC treatments, part of the P content is in inorganic water soluble form and also in the biochar treatments some ash containing P soluble salts may be the source of increase in water soluble P content. The Ca2-P form in the control was increased from 5.1 mg kg-1 of soil to 11.1 and 16.2 mg kg-1 of soil in the SMC1 and SMC2 respectively, which had an increasing trend with time(p<0.01). During 120 days of incubation, the Ca8-P, and Al-P forms were also increased from 158 and 27 mg kg-1 of soil in the control to 186 and 35 mg kg-1 of soil in the SMC2 treatment (p<0.01). The distribution pattern of P fractions after application of SMC and Biochar was different and it changed with the level of the applied material. Conclusions: Based on the results of this experiment application of organic materials of different nature such as spent mushroom compost and sugarcane bagasse biochar to calcareous soils can affect the availability and various forms of phosphorus to the extent that it should be considered as a measure to improve P availability conditions.
Research Paper
M. A. Delavar; A. Naderi
Abstract
Introduction Generally, formation and development of sodic soils often appear as almost large in flat plains capable of cultivation, especially in arid and semi-arid regions. Due to their unsuitable characteristics, Slickspots leave bad effects on plants growth and finally on human health. High levels ...
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Introduction Generally, formation and development of sodic soils often appear as almost large in flat plains capable of cultivation, especially in arid and semi-arid regions. Due to their unsuitable characteristics, Slickspots leave bad effects on plants growth and finally on human health. High levels of soluble and exchangeable sodium ions and colloidal material are the main marks of sodic soils. Different surface areas of Slickspot are spread over the flat and arable plains in Iran. The aim of this study was to evaluate the different properties of sodic soils and related soil formation factors in the semi-arid soils of Abyek plain. Materials and Methods The study area, with the coordinates 35° 47′ - 35° 53′ N and 50° 31′ - 50° 33′ E, was located in the southeastern of Abyek city, Ghazvin providence. Piedmont plain was the main physiography of the area and altitudes were divided in three topographic zones: 1190-1180, 1170-1160, 1150-1140 meters above sea level that the zones were classified into upper, middle and flat parts, respectively. Based on topography and site properties, 13 soil profiles were excavated in the topographic zones and all profiles were described based on USDA Standard Soil Description Manual Results and Discussion The results showed that soil acidity measured in saturated extraction ranged from 8.6 to 9.1, 9.8 to 9.7 and 9.1 to 10.1 for upper, middle and flat areas, respectively. Field observation studies of upper parts revealed that gravelly and subangular blocky soil structures were found in surface and subsurface horizons, respectively, while the subangular blocky and massive structures were found in subsurface horizons of middle parts profiles. The subangular blocky and columnar structures were demonstrated structures in profiles of the flat areas. Despite the low topography difference, 5 to 10 m in upper lands, exchangeable sodium content and electrical conductivity were low, and saline or sodic soils were not observed. These soils were classified as Xeric Haplocambids. In the middle part with 2 to 5 m difference in elevation, soils were classified as Sodic Xeric Haplocambids and Sodic Xeric Haplocalcids. The white spots observed in the sodic soils were classified as Xeric and Vertic Natrargids. Compare with the adjacent areas, the concentration of carbonate and bicarbonate anions were relatively high in soils of the flat areas that led to considerable increase in soil acidity. This can shows the accumulation of sodium carbonate salts in the soils. The presence of carbonate and bicarbonate anions in middle areas, probably was due to the development of Sodicization in the soils. The XRD diffractometers showed illite, montmorilonite, chlorite and palygorskite as the clay minerals in soil heorizons. Illite was found in all soil horizons of flat areas with deep decline. This decline was along with increasing of smectite clay minerals in Natric horizons that had poor drainage conditions. The clay coatings in the natric horizons were confirmed by micromorphology and scanning electron microscopy techniques. The cumulative clays on external surfaces of soil aggregates and wall pores, in flat areas, revealed the clay eluviation process. Because of the high soluble and exchangeable sodium cations, the conditions were favorable for transfer of clay in the soils, even in the presence of lime. Conclusion Consequently, the main soil formation factors in sodic soils can be presented as different in soil positions on piedmont physiography, the local relief, lateral and vertical movement of water and soluble salts from neighboring areas into the downstream lands and also salt and sodium containing minerals deposited by wind. The Slickspots and related soils were one of the major terrestrial phenomena in the plain Abyek. The Sodic soils in the plain were formed in the absence of high ground water table. Other environmental factors such as micro reliefs, position on the Landform, lateral movement of water and soluble salts and windborne sediments, played and essential role in the formation of sodic soils. The results of the experiments indicated that Sodicization process is developing towards the adjacent land and the absence of gypsum accelerated this development in these areas. Also, mineralogical studies indicate the presence of smectite mineral clay in Natric horizon where the drainage condition was poor and gave the possibility of neoformation of smectite, and that clay movement evidence from upper parts of profile was confirmed by micromorphological studies.
