نشریه مکانیزاسیون کشاورزی
سال چهارم شماره 1 (تابستان 1397)

Moldboard plough (MP) is widely used by farmers around the world. Inverting the soil only to the right side, creating ridges or open furrows in the middle of the field, lower field efficiency, higher fuel consumption and unnecessary traveling on the headland are the disadvantages of these ploughs. In order to eliminate those disadvantages of MP, reversible moldboard plough (RMP) has been developed. However, high depreciation in the turning mechanism of RMP, need for a powerful tractor due to its heavy weight, and its high price caused to limited development of RMP. In this research, to eliminate the disadvantages of MP while maintaining its benefits, new design of moldboard plough named as symmetric moldboard plough (SMP) was developed. For evaluation of the new design of moldboard plough a randomized complete split block experimental design with three main plots of plough types: MP, RMP and SMP beside the sub plots of tillage speeds of 2.7, 4.0 and 4.7 km/h was used. The field experiment of SMP on soil turning was successfully performed. With removal of the top bottoms of RMP, the SMP weight in the prototype model was reduced by 32% and the parts subjected to high depreciation were eliminated. In the field experiment there was no significant differences between the SMP with specific draft of 44.45 kNm-2 and a tested RMP with specific draft of 43.37 kNm-2. But the tested MP with specific draft of 32.73 kNm-2 had the lowest.

In this research, modeling of energy consumption and environmental emissions for different process of tea production in Gilan province (Iran) were investigated using regression and artificial neural networks. Data related to agricultural and industrial activities of tea production chain were collected through questionnaire survey from tea farms of different counties in Guilan province. Also, the datatbank of agricultural organization, tea research institute and tea factories were collected. The results showed that the total energy input and output for green tea leaf production were 34343.51 and 10996.45 MJ/ha, respectively. Also, the total energy input for dry tea was obtained 64885.23 MJ/ton. The results of the life cycle assessment in tea farms revealed that the highest effect belonged to nitrogen in abiotic depletion, dcidification, eutrophication and global warming potential impacts. The survey of life cycle assessment in the tea processing factories illustrated that diesel fuel had the highest share in abiotic depletion, ozone layer depletion, human toxicity, fresh water aquatic ecotoxicity and photochemical oxidation impact categories. In acidification, eutrophication, global warming potential impacts, green leaf input had the highest share. Moreover, the highest share of marine aquatic ecotoxicity and terrestrial ecotoxicity was belonged to coated paper. The results of energy and environmental emissions modeling for green tea leaf production showed that artificial neural networks can predict the outputs and inputs with more accuracy than regression technique.

Some agricultural operations such as transplanting, flamethrower and digging canals need a low tractors speed, while this speed is created by creep gear in new tractors. ITM 285 tractor is a common tractor used in different agricultural operations in Iran and most agricultural activities are done by them. Its use is limited due to inability to establish low speeds for such operations. In this study, a gearbox was selected to be installed on ITM 285 tractors and its performance in terms of speed and maximum drawbar pull was evaluated. The gearbox consists of a hydromotor and a planetary gear. The tractor hydraulic output is connected to hydromotor. By reducing rotational speed in planetary gear, the hydromotor rotation movement is transmitted to PTO shaft. Because PTO shaft is in wheel round position, the shaft moves cause to movement of tractor. Assessments showed that the made power transmission system is able to produce a speed of 0.12 to 0.38 km/h for tractor. In this case, the measured maximum drawbar pull force was 1421.42 N. This power transmission system can be used in operations such as, transplanting, flamethrower, digging canals and vegetables harvesting.

 Conservation tillage method can lead to sustainable agriculture and reduce soil erosion, soil moisture and costs. For conservation tillage application, its effects on yield indicators and soil characteristics should be investigated. This study was carried out to evaluate the effects of conservation systems on maize production in rotation with wheat in Dasht-e- Naz Sari agro-industry. In addition to the conventional method, evaluated treatments were applied to different conditions of wheat residue (absence and presence of crushed residues). Plant height, leaf number and ear weight, potassium content, phosphorus and nitrogen, organic matter, EC, pH, soil moisture and bulk density were measured after planting and harvesting. Although the effects of conservation tillage would occur in a long term, there were no significant differences in some measurements but some changes in different indices. Direct planting of maize in wheat residues showed the highest soil phosphorus content. Also, the effect of treatments on soil moisture content and bulk density after planting showed a significant discrepancy. On the farm with shredded wheat residue and considering that reduced tillage had been applied for wheat planting, corn plant produced larger stem height. In this study, the lack of negative effectiveness of conservation system on the most of the studied quantities was observed. Considering the decrease in use of machinery in conservation methods and its economic and environmental benefits, it can be a strong point for implementation of conservation tillage in Dasht-e Naz Sari agro-industry.

One of the factors affecting soil structure is freezing and thawing process. It could change soil compressibility threshold (bearing capacity or pre-compression stress). For this purpose, the effect of freezing and thawing process on the bearing capacity and energy consumption during soil compression was studied. The soil samples in this study were prepared in two humidity levels of 10% and 15%, with the density of 1.15, 1.265 and 1.39 g/cm3. They were affected by freezing and thawing process and the results were compared with the similar samples without thaw-freeze process. The results showed that soil thawing and freezing process has reduced significantly the bearing capacity and required energy for soil compaction. Although this process improves and modifies soil structure, but any excessive pressure over normal load, not only eliminates the beneficial effects of freezing and thawing on soil structure, but also causes more soil compaction.Therefore, the use of machines and implements on farms must be carefully according to soil physical properties and the factors affecting it.

 Drying process is an important and critical operation in the storage and transportation cycle of agricultural products. Drying is one of the best solutions to store and supply most of products throughout year. In this study, thin layer drying of Kumquat fruit was carried out at three temperature levels of 60, 70 and 80 degree of Celsius and three thickness levels of 2, 4.5 and 7 mm with three replications. In order to predict the correct drying process, the data from the experiment were fitted with twelve different models. The obtained results showed that Midilli model has the highest determination coefficient of 99.855, the lowest values ​​of MRPD, RMSE, X2 and the highest value for the desirability function in comparison with other drying models. Investigating of the thin layer drying of Kumquat fruit at different temperatures showed that increasing the thickness of layers and reducing the temperature, the drying process will last longer. The highest drying rate (1.34 kg/kg dry matter per hour) was obtained at 80 ° C and 2 mm thick. The activation energy has a direct relationship with thickness, which was 34.29, 76.68 and 80.56 kJ per moles in thicknesses of 2, 4.5 and 7, respectively. Also, the penetration coefficient showed an increasing trend by increasing the temperature and thickness. The maximum penetration coefficient was 7.594 × E-10 m2/s at the highest temperature and thickness.

Solar energy is the largest resource of clean energy in the world and it is available in most areas. This energy is a durable energy that needs to be collected for use. An example for solar collectors is the solar pond that collect and store solar energy by high concentrated brine. The most common type of solar ponds are salt gradient ponds, which use a gradient layer to prevent the loss of energy. In this research, a small salt gradient pond was constructed with a cylinder diameter of 65 centimeters and a total height of 85 centimeters and examined for 10 weeks. The pond was constructed in a gradient form with three distinct layers and insulated completely. After construction of the pond, concentration of the layers differed slightly from designed concentration due to mixing. However, after a week, the density of the pool reached relative stability and retained its layered structure by the end of the experiment period. The maximum-recorded temperature was 41.7 °C. This little change in temperature of the storage layer could be in result of the low environmental temperature in the region. The surface layer density was increasing during the daily test period. However, the density of the gradient layer had the slightest variation among the pond layers. The temperature increased by an average rate of 0.37 ° C per day.

In order to design the processing machines for onion, it is necessary to have enough information about its size, density, shape index, angle of friction and penetration resistance (hardness). In this research, physical and mechanical properties of onion cultivar Horand were studied with a completely randomized design experiment with 20 replications. Three levels of, small, medium and large onion bulb size (small was less than 4 cm, medium between 4 to 7 cm and large greater than 7 cm) were evaluated. The results showed that with the increasing size of the bulbs there was an increase in the mass (18.16 to 151.85 gr), geometric mean diameter (34.49 to 68.51mm), arithmetic mean diameter (34.54 to 69.42 mm), surface area (5241.98 to 18827.18mm2), volume (31500 to171400 mm3), coefficient of static friction on the plastic and galvanized iron surfaces (0.34 to 0.57 and 0.37 to 0.53, respectively) and finally, the shape index of onion bulbs (1.02 to 1.22). Increasing bulb size increased Horand cv. true density (772.3 to 886.6 kgm-3), static friction coefficient on the wood surface (0.32 to 0.41) and requirement power for penetration (5.66 to 6.50 kgf). Big bulbs were more susceptible to frictional injuries than medium and small ones.