فهرست مطالب

  • سال دوم شماره 1 (بهار 1393)
  • تاریخ انتشار: 1393/01/01
  • تعداد عناوین: 9
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  • R. Tabatabaekoloor *, A. R. Kolouri Pages 1-10

    In this research, shear strength and specific cutting energy were determined for the factors including two stem orientations (45º and 90º), four cutting heights (5, 15, 25 and 35 cm above ground level), three bevel angles (20, 30 and 40º) and three shearing velocities (5, 10 and 15 mm min-1 ). A factorial experiment was used based on randomized complete design at three replications. The results showed that shear strength decreases by increasing cutting height and increases by increasing blade bevel angle. The minimum and maximum amount of shear strength were 1.2 and 3.95 N. mm-2 at the cutting height of 35 and 5 cm and the bevel angle of 20º and 40º, respectively. Shear strength reduced by increasing shearing velocity at the both stem orientations. The minimum amount of shear strength was 1.67 N. mm-2 for the shearing velocity of 15 mm. min-1 and the stem orientation of 45º. The specific cutting energy reduced from 33.5 mJ. mm-2 at the bevel angle of 40º and the orientation angle of 90ºto 7.5 mJ. mm-2 at the bevel angle of 20º and the orientation angle of 45º. The maximum specific cutting energy was 29.7 mJ. mm-2 at the stem orientation of 90ºand the shearing velocity of 5 mm min1 . Its minimum amount was 13.24 mJ. mm-2 at the stem orientation of 45º and the shearing velocity of 15 mm.min-1 .

    Keywords: Bevel angle, Cutting height, Shear strength, Specific cutting energy, Soybean
  • I. Eskandari *, H. Navid, F. Moradi Pages 11-22

    One approach to improve remote sensing techniques relies on the spectral response to infer soil and crop properties. The aim is to develop methods that can identify inferring factors so that they can be removed during later analysis. Differences in spectral reflectance can be the base of detecting crop residue and growth of crop in different tillage management. This experiment was conducted under dryland conditions to determine the influence of crop residue remained on soil surface in conservation and conventional tillage systems on soil moisture, canopy temperature and grain yield and also yield components of a winter wheat. Remotely sensed data were acquired three times prior to canopy closure using a handheld thermal imager (7,000 to 14,000 nm). According to results, differences between yields were significant (P<0.01). The yield of no-till treatment with all previous crop residue (NT2) was slightly more than that for no-till with only standing previous crop residue (NT1). Also, the yield of reduced tillage system (CD) was 31% higher than that for conventional tillage system (MD). A similar trend was observed for wheat biomass yield. No-till treatment increased soil moisture content in the 0–30 cm layer. At the flowering stage, soil bulk density in 0-20 cm depth was significantly lower for NT2 (the no-till with total residue) compared to MD and CD treatments. During the flowering stage, residues in NT1 and NT2 lowered the canopy temperature by 3-9 °C over other treatments (MD and CD). Results of this study indicated that for a dryland vetch-winter wheat cropping system with annual precipitation of 251 mm, NT2 had higher grain yields (762 kg ha_1) than that obtained by MD system.

    Keywords: Conservation tillage, Dryland wheat, Surface, Canopy temperature, Soil physical properties, Thermal Imaging
  • Gh. H. Shahgholi *, H. Irannazhad Pages 23-33

    Farm tractors play a key role in farm mechanization all over the world. They supply the required power for most of the agricultural operations such as soil cultivation, planting, weed control and harvesting. ITM 285 is the most popular tractor in IRAN. In spite of its high production and usage, less research has been conducted on its performance optimization. Performance of its engine depends on different parameters such as its components and their interactions. In this research, to demonstrate the operation of engine components and their interactions during engine operation, kinematic and kinetic analysis was conducted for key elements of the engine. The results were analysed in terms of velocity and acceleration of the piston, connecting rod and crankshaft. Also forces and moments acting on the moving crank of the crankshaft were computed. It was concluded that the results of the research are useful for stress and fatigue analysis in order to optimize the engine components and make them durable and lighter in the future.

    Keywords: Crankshaft, Kinematic, kinetic analysis, Piston, ITM 285 tractor
  • N. Eghra *, Y. Ajabshirchi, M. Sarshar, S.S. Alavi Pages 35-44

    Bioethanol production from agricultural residues is one of the promising methods, since the raw materials are abundant and unvalued. Pretreatment is the most important step in bioethanol production. In this study, saccharification percentage of steam and microwave pretreatment methods was investigated in sugarcane bagasse. Microwave pretreatment was studied in two factors of microwave power and retention time (170, 450 and 850 W and 2, 6 and 10 min, respectively). In addition, steam pretreatment was surveyed in two factors of sulfuric acid containing and retention time (0, 1, 2 and 3% and 7 and 14 min, respectively). After hydrolysis, saccharification percentage was up to 49.6% for steam pretreatment and 57.2% for microwave pretreatment, respectively, compared to 20.85% in non-pretreated bagasse. So, microwave was called the more effective pretreatment in this study.

    Keywords: Enzymatic hydrolysis, Pretreatment Microwave, Steam, Sugarcane bagasse
  • M. Shahabi Ghoyonloe, Sh. Rafiee *, S. S. Mohtasebi, S. Hosseinpour Pages 45-57

    In this study, the effects of drying air temperature and airflow rate on the drying duration of semi-dried and completely dried green tea were determined. Also, their effects on the ingredients of the extaction from green tea leaves were determined. Drying temperatures and airflow rates were: 50, 60, 70, 80 and 90 °C and 0.5, 1 and 1.5 m/s. The recorded data were: the drying duration and the amount of poly phenols available in the dried leaves extractions. A factorial statistical experiment was conducted by randomized complete block design. The results showed that with increasing temperature and drying airflow rate, the required time to reach half and completely dried samples are decreased.The variation in the airflow rate at high temperatures did not have any significant effect on drying duration. However, at the low temperatures the variation in airflow rate had significant influence on the drying duration. The amount of poly phenols extracted from green tea leaves dried at high temperatures was more than that for those dried at low temperatures. However, the airflow velocity did not show any significant effect on the indredients of the extraction. Due to destruction of the ingredients of green tea at both high and low temperatures of dryer, it is recommended to use the average temperatures in drying process

    Keywords: Drying, Extraction, Green tea, Poly phenols, Medicinal plants
  • J. Taghinazhad *, T. Mesri Pages 59-68

    Equipment and machinery choose for agricultural operations is generally not a simple task. The main problem by using seed driller for soybean is the lack of sufficient accuracy in the distribution and the location of seeds in the soil. This problem is rather less in row planters. To maximize the yield, changes in product varieties, row spacing and seed rate per unit area are inevitable. The aim of this study was to select the most appropriate system for planting soybeans in Moghan plain. So an experiment with statistical complete randomized block design with four replications was conducted during two years in Moghan. Machines and plant systems (treatments) include cereal deep planters (Hassia) with T1:25 and T2:50 cm row space, grain drills (Barzegar Hmadani) with T3:25 and T4: 50 cm row space, pneumatic row planters with T5:50 cm in row space (Gaspardo) and T6 (Noda) two rows on ridge 75 cm row distance. Results indicated that T6 and T4 treatments have the highest and lowest yield with 2864 and 2252 kg ha-1 , respectively. T6 had the maximum seed germination rate (87.32%). According to the coefficients of seed distribution T6 had the maximum uniformity in adjusted distances (83.04%) and in average distances (87.32%). It is recommended to use of, pneumatic planters with two rows on ridge and 75cm in row distance which showed the highest yield and also was preferred in terms of many other factors.

    Keywords: Planter, Planting system, Soybean, Yield
  • J. Asghari Meidany *, E. Karimi, N. Loveimi Pages 69-76

    Effects of tillage on wheat yield in forage-wheat rotation are still unknown in Iran. So, this study was performed in order to investigate the effects of different methods of tillage on soil physical properties and yield of dryland wheat in rotation with spring forage hay. This experiment was carried out with 6 treatments and 3 replications for 3 years in RCBD statistical design in Maragheh region. The results showed significant differences for yield components in spring planted forage-wheat rotations affected by the treatments.T1 treatment (chisel plough + cyclotiller + wheat grain driller) had the highest stubble (4.320 ton/ha), grain (2.398 ton/ha) and biologic yield (6.720 ton/ha) and also harvesting index (33.89 %). Soil moisture was significantly different in 3 soil depths between treatments, and T1 treatment had the highest soil moisture in all depths. Bulk density differences was significant in 3 depths andT1 treatment had the lowest bulk density in three depths The results of this study suggest the application of "chisel plough + cyclotiller + wheat grain driller” for wheat production in rotation with winter and spring vetch forage.

    Keywords: Bulk density, Dryland wheat yield, Soil moisture, Tillage, Wheat-Forage rotation
  • M. Azadbakht*, N. Tajari, R. Pourbagher Pages 77-86

    Weather conditions are of the main factors affecting the quality and quantity of agricultural and horticultural crops. Climatic conditions vary from one region to another, and these differences have important roles in the development of some products. In this study, some physical properties (mass, volume, density, length, width, thickness, arithmetic mean diameter, geometric mean diameter, equivalent diameter, sphericity index and area), and kiwi fruit storage (at room temperature) after two weeks, and some of the mechanical properties (rupture energy and force, the maximum deformation and toughness). Kiwi fruit (Hayward variety) harvested from three provinces of Golestan, Gilan and Mazandaran was evaluated in a completely randomized design. According to the analysis of data, the effect of regions on the physical properties of kiwi fruit was not significant. But, the storage effect on some physical properties such as the length, geometric mean diameter and arithmetic mean diameter was significant at the significance level of 1 . Interactions between different regions and storage on the rupture energy, rupture force and toughness was significant at the 1 level. The effect of storage on the maximum deformation was significant at the 1 level. The effect of regions on the maximum deformation was significant at the 5% level. The highest rupture energy and rupture force was for the kiwi fruit from Gilan at the first day of storage, equal to 3364.7 N.mm and 619.04 N, respectively. The maximum deformation 12.47 mm and toughness 0.02342 N.mm-2 belonged to the first day of storage. The minimum rupture energy and rupture force belonged to the kiwi fruit from Mazandaran and at the 14th day of storage, equal to 551.5 N.mm and 109.54 N, respectively. Also, the minimum deformation, 9.84 mm at the 14th day of storage and the minimum toughness, 0.00842 N.mm-2 was in Mazandaran.

    Keywords: Kiwi fruit, Mechanical properties, Physical properties, Region effect, Storage
  • R. Rahimzadeh *, Sh. Abdollahpour, Y. Ajabshirchi, N. Sartipi, A. Sharifi, A. Mohammadi Pages 87-96

    Direct planting has become a more common practice in the recent years, because it conserves soil and water as well as it is low-cost method. Since it requires special implements, it did not have much progress in our country. Regarding that the direct planting is practiced in undisturbed lands, seed planter (especially its furrows openers) must have an especial structure. In order to obtain a suitable furrow opener, this experiment was conducted in Dryland Agricultural Research Institute in Maragheh. Hence, O1 and O2 openers were designed and their performance compared with hoe opener (check). At three different operating speeds (5, 8 and 10 km.ha-1 ), all openers were evaluated for draft force, plant depth uniformity, soil disturbance and number of seedlings. The experiment was conducted using a split plot design based on RCBD at 4 replications. The results showed that there were significant differences among the openers. Maximum planting depth uniformity and seedling number were observed in O2, and the lowest draft force was seen in O1, where the check opener had minimum soil disturbance. Although, O2 had the highest soil disturbance, but its draft force did not significantly differ with check opener. Increasing operating speed, draft force increased and reduced planting depth. Moreover, it had no significant effects on soil disturbance and seedling number. It can be concluded that new designed O2 opener could improve the germination of seedlings, and the uniformity of planting depth without need to significantly draft force increasing in compared with the check. Hence, O2 opener could be recommended to use for direct planting in drylands.

    Keywords: Conservation tillage, Dryland, New opener