نشریه مکانیزاسیون کشاورزی
سال یکم شماره 2 (پاییز 1392)

Measuring the resistance and fracture force of materials is a basic and fundamental issue in designing of many agricultural equipment and machinery. In this study, the fracture force of four varieties of safflower seed cultivated in Iran at moisture content of 5.5% (w.b.) in both horizontal and vertical positions were determined. In the experiments a grain pressure test device (Instron) was used. The results showed that in horizontal loading position, the maximum fracture forcebelongs to Padideh variety (83 N) and then Goldasht variety (80.29 N), while the minimum fracture force belongs to Esfahan 28 variety (65.64 N). At vertical loading position the maximum and minimum fracture forces belong to Goldasht variety (50.74 N) and PS variety (34.64 N). By comparing the effects of loading positions (horizontal and vertical), the fracture force values for Goldasht variety are significantly more than those for other varieties. Therefore, Goldasht variety is preferred to other varieties because of its highest strength against mechanical damages. In all varieties, the fracture force of the seeds in horizontal loading position was about twice as much as in vertical loading position.

Accelerated development of agricultural mechanization is causing problems on occupational health and safety for people working in different fields of agriculture. Noise is considered as one of the most debilitating conditions in farming and therefore, a comprehensive investigation in this relation is required. In this study, some factors affecting the noise generated by a Goldoni garden tractor were evaluated. Studied factors were including engine speed, gear ratios, type of operation and microphone distance. In this relation, factorial experiments in randomized complete block design with three replicates were performed. The results of this study indicated that different levels of gear ratio, type of operation and microphone distance at level of 1% and engine speed is significant at 5% are significant variables. Also the results of this study revealed that sound pressure level decreases with increasing center frequencies. At center frequency of 4000 Hz, it was 56.65 dB. According to the results, the maximum sound pressure of this garden tractor was 94.87 dB.

With regard to the importance of forage production in Iran, the main objective of this study is to analyze the relationship between inputs and yield in different alfalfa harvesting systems by using production function. Therefore, data on alfalfa hay production were collected from 75 farms in Zanjan province using face to face surveying in the year 1391(2012). By a systematic random sampling method. Two farms in different areas were managed by silage harvesting system and data on all farms for alfalfa silage production estimated based on data obtained. The relationship between inputs and yield were estimated using Cobb-Douglas production function for different harvesting systems (alfalfa hay and alfalfa silage). The results of the production function showed that machinery had the highest impact among the inputs for alfalfa hay and alfalfa silage productions. The biocide and electricity for irrigation had negative impacts on yield in different alfalfa harvesting systems. Seed for alfalfa hay and machinery for alfalfa silage production had the highest marginal product values. Moreover, these results revealed that scale economies exist in different harvesting system of alfalfa production. Accordingly, proportionate increase in the inputs is recommended in order to find a more economical production process.

Soybean is mostly harvesteds by conventional grain combine harvesters. Harvesting losses is one of the major issues in this way. Harvesting losses cannot be reduced to zero, but using the correct methods and proper equipments could reduce it to an acceptable level. Estimate of the losses rate in harvesting stage and recognition of effective factors in essentioal to decrease the losses. For reaching to a minimum loss, each one of harvesting processes (cutting, threshing, separation and …) must be optimized in operation. In this study the influence of forward speed, moisture content and plant density factors were used to make a mathematical model for John Deere 955 combine harvester rear losses. The experiments were conducted in soybean farms in Moghan plain, which is one of the major soybean prodcution areas in Ardabil province, Iran. For statistics a 3×3×3 factorial pattern based on randomized complete block design with 3 replications (in total 81 tests) was used. The effects of forward speed (in three levels of 1.8, 2.5 & 3.2 km h-1), moisture content (15, 19 & 23%) and soybean plant density  (40, 50 and 60 plant m-2) were tested again combine harvester rear losses (%). ANOVA results showed that the effects of all three factors with the double and triple interactions were significant at 1% probability level on rear losses. The losses were increased with increasing forward speed, plant density and moisture content. Linear regression was used to determine the relationship between dependent and independent parameters. The results of regression analysis of the model showed that 77% of the combine harvester rear losses is justified by the three variables studied in this study. The higher standardized coefficient of combine forward speed in the model make it the greatest effect on the rate of combine harvester rear losses.

Simulation of the heat and moisture transfer is one of the effective techniques for modification and optimization in different food drying methods. One of the most important factors to improve the accuracy of the predicted temperature and moisture content profiles in a drying process is the shrinkage or volume reduction of products The aim of this study was mathematical modeling of the shrinkage rate and the moving velocity of product boundary during drying process in order to prediction of slices thicknesses and the distance of inner nods using numerical solution for related function by finite element method. The drying of apple slices was conducted in the air velocity of 0.6, 1.2 and 1.8 m s-1 and the temperature of 50, 60 and 70 ºC. Based on the results, the thickness of the samples reduced from 0.0053 to 0.0014 m. The exponential model showed a better fitness to the results for thickness and boundary moving velocity change in compare to the other studied models. The model coefficients were calculated as a function of drying time, temperature and velocity of hot air. The distance of domain internal nods was predicted as a function of outer boundary velocity and drying time. A good fitness was observed between the experimental and simulation results in sample shrinkage.

Soil quality maintenance is essential for sustainable food production, waste decomposition and etc. For sustainable management of soil, it is necessary to evaluated soil quality. Soil physical quality drastically affect by tillage methods. Since conventional tillage increases soil erosion, it is better to replace other farming tillage methods. In this study effect of three tillage methods including conventional tillage (tillage with moldboard), chisel plow and disk plow with notillage as controlled treatment on the bulk density, porosity, saturated hydraulic conductivity field, organic matter, aggregate size distribution, soil aggregates stability investigated. Complete randomized blocks were used as statistical design for field experiments. The results showed tillage operations compared with controlled treatment decreased organic matter, bulk density and aggregates stability in the soil surface layer (0-10 cm) significantly (p ≤ 0.01). Tillage operations increased soil porosity in the soil surface layer (0-10 cm) significantly. The treatments effects on saturation hydraulic conductivity and aggregate size distribution were not significant. Generally no-tillage or the controlled treatment maintains more soil physical quality compare with other tillage operations. In order to maintain soil physical quality, cultivation without tillage is recommended.

The most effective wayto optimize traction performance of attractor is creation of proper coordination between power, load on driving wheels, forward speed and draft of implements with wheels slip. In this study, the effects of speed and depth of plowing on slip, draft force and traction efficiency of ITM299 tractor were measured. In this regards, drawbar pull, rolling resistance and slip of driving wheels has directly been measured. Field tests were done on clay soil with 14% constant moisture content(based on dry weight), performed in a randomized complete blocks design with factorial effects of two levels of tillage depth (20 and 30 cm) and three levels of forward speed (3, 4.5 and 6 km/h). According to the results of experimental tests, increase in forward speed and tillage depth lead to increase in drawbar pull. However, increase in tillage depth or reduce in forward speedleadto increase in drive wheels slip. Interaction effect of tillage depth and speed on draft and tractor wheels slip was insignificant. The most effective parameter on traction ratio was forward speed. So that the maximum traction ratio (80.82%) occurred with the average tillage depth and maximum speed and withtheslip of 10.5%.

In this study, the energy consumption of button mushroom production in Khorasan Razavi province (Iran) was calculated. Data were collected from 13 production units with face to face questionnaire method. The production units were divided into three levels (categories) based on their area as: smaller than 7,000 m2 , 7,000-20,000 m2 and larger than 20,000 m2 . The results showed that the energy input per areafor the production of button mushroom was 2,480.86 MJ.m-2 . In between the the different energy sources, the highest share of energy consumption belonged to fuel (79.76%) followed by wheat straw (12.40%) and machinery (5.59%). The Cobb-Douglass model results revealed that the wheat corn and poultry manure had the highest regression coefficient (1.30 and 0.77) among the other inputs (for button mushroom and by-product compost production). Furthermore, the effect of poultry manure input on button mushroom yield was significant at the level of 5%. The production units with cultivated area of 7,000-20,000 m2 consumed the least amount of energy and had the highest energy ratio.

Increasing of energy consumption in the developing agriculture reveals necessity of optimizing the operation tools used in this sector. The objective of the present research is studying the interaction of narrow tillage tines and soil to reach the optimum geometric shape in order to raise the yield of energy consumption. This research was performed in a soil bin with factorial experiments in a completely randomized format with three iterations. Testing treatments were tillage depth (10, 20 and 25 cm), rake angle (60, 70 and 90°) and blade width (3 and 6 cm) and studied parameters were draft force, soil disturbance area and specific draft force. The results showed that depth and rake angle have significant influences on the amount of draft resistant force, soil disturbance area and specific draft force (p<0.01). Also blade width influenced draft resistant force and soil disturbance area significantly, but it did not have significant impact on the amount of specific draft force ).The comparison of averages revealed that the combination of 25 cm depth with 90° rake angle provides superlative soil disturbance. However, it needs maximum amount of draft force. Also, consequences showed that the best combination, in order to decrease the specific draft force, is the use of wider blades (6 cm) with smaller rake angle (60°) and less working depth (10 cm).

In designing a sifting machine, geometrical size of seeds and static coefficient of friction, as two physical properties, determine the hole diameters and slope of sieves, respectively. Since the geometrical size of seeds on various cultivars is different, various sieves should be designed with different hole size or be able to change for various seeds. Otherwise, losses will increase in sifting machines. Moreover, the rolling and sliding coefficients of static friction are different in various surfaces for wheat cultivars. Therefore, the slope of sieves should be adjusted for various wheat cultivars to decrease wheat losses. In this investigation, geometrical size of seeds and static coefficient of friction were studied for four cultivars of wheat seeds (Azar, Sardari, Sabalan and Alvand).Results indicated that these two physical properties are different for various cultivars of wheat. The maximum length belongs to Azar cultivar equal to 7.8 mm. The maximum width and thickness, respectively equal to 4.05 and 3.45 mm, belong to Alvand cultivar. The minimum length belongs to Azar cultivar, equal to 5 mm. The minimum width and thickness, respectively equal to 1.85 mm and 1.75 mm, were obtained for Alvand cultivar. The minimum rolling and sliding coefficients of friction reach 0.379 and 0.685 (respectively) for Alvand cultivar on a metallic surface. Furthermore, the maximum rolling and sliding coefficient of friction, equal to 0.664 and 1.181(respectively) belong to Sabalan cultivar on a fabric surface. In existing sifting machines, the slope and diameters of sieves are not modified for various wheat cultivars. Therefore, it causes the losses in sifting machines.

Tillage systems are one of the main factors affecting the physical properties of soil and volatilities of yield of agricultural products. This experiment was done in summer 2013 in the research field of Islamic Azad University of Varamin. The study was performed using the statistical split plots in the form of completely randomized blocks design with three replications. The main factors in this study included four different methods of tillage and as the sub-factors two varieties of forage maize. Completely randomized blocks design was used for the statistical analysis of soil physical properties. Based on the results, the different tillage methods affect the measured traits such as soil physical properties and plant yield significantly at 1% probability level. The maximum yield rate was related to the single cross 704 variety with twice disc tillages at the depth of 10-15 cm and equal to 88.18 tons fresh fodder per hectare.