نشریه مکانیزاسیون کشاورزی
سال سوم شماره 2 (پاییز 1395)

Cotton is one of the main agricultural, industrial and commercial products in the world. It is the most important and valuable natural fiber and its seed is a valuable source of food for humans and animals. To evaluate the effect of defoliator spraying time and forward speed of cotton harvester on machine performance and quality of cotton fiber, an experiment was carried out in research station of Hashemabad, Gorgan in Iran during 2015. The studied factors consisted of two levels of defoliator spraying time, two levels of cotton varieties suitable for mechanical harvesting, and three levels of forward speed. The experiments used in this study was based on split plot in randomized complete block design with three replications. Results showed that, the effect of spraying time and varieties on the efficiency of the machine and seed cotton losses were significant. Also, the effect of defoliator spraying time-variety interaction on the efficiency of machine was significant. On the second spraying time, while 90 percent of bolls were open, the highest efficiency of the machine was obtained, while losses were low. Forward speed had no significant effect on the performance characteristics of the machine.

Allocation management is one of the main and well-known solutions for sustainable development in agriculture. The present research was undertaken aiming at investigation and determination of the factors affecting the choice of crops to be cultivated at Karaj and Savojbolagh, Iran. For this purpose, 9 factors affecting the choice of crops cultivation were investigated. Furthermore, energy efficiency and mechanization degree indices were calculated. Statistical population for the present research composed of farmers at two townships during 2012-2013 crop years. In order to gather required data, a researcher-made questionnaire was used whose reliability coefficient was found to be 0.91; Also, data from Agricultural Jihad Organization was utilized for this purpose. Obtained results indicated that, the factors “training and promotion” (with a correlation coefficient of 0.32) and “characteristics of technical and agronomic” (with a correlation coefficient of 0.06) have the maximum and minimum perceived usefulness, respectively. All effective factors of “characteristics of farming system” were found to be significant at 99%. In terms of energy efficiency indices, wheat, and in terms of mechanization degree, alfalfa, outperformed other crops investigated across two townships. Therefore, in order to approach sustainable agriculture and enhance importance coefficient of the factors such as climatic potential of different regions in selecting crops to be cultivated, one can go for farmers training and prepare required foundations for them. Accordingly, when it comes to cultivation of crops across Karaj and Savojbolagh, in the cases where agricultural input and energy consumption represent farmer's priorities, they may be recommended to cultivate wheat. Otherwise, where they have shortage of motor power, they may better going for alfalfa.

About one third of the onion harvesting time and cost is consumed for removing of leaves from onion bulbs. Accordingly, the use of appropriate topping technologies is one of the main objectives for development of onion harvesting mechanization. In this study, a rolling onion topper was modified in such a way that to be mounted on a tractor. Then, the effect of two rotational speeds of leaf remover blades namely, 2950 and 1800 rpm on remaining leaves of onion bulb after cutting, and also, the percentage of topped onions and percentage of damaged bulbs were measured to determine the suitable speed. Necessary modifications were made on the machine to enable it to be run and transported by a tractor. In the next step, the machine's field capacity was calculated and economical comparison between conventional topping method by labor and the device was carried out. The results showed that both 2950 and 1800 rpm rotational speeds of the topping blades do not have significant effect on remaining leaves after cutting, percentage of topped onions and percentage of damaged bulbs. According to the design requirements and energy reduction of leaves removing, the rotational speed of 1800 rpm was proved to be the appropriate speed. Economic evaluations showed that replacing of conventional topping method by topping machine reduces work force by 43 workers and saves 53% of the costs per hectare.

Agricultural sector has a considerable and increasing ratio of the total energy consumption of the societies. The main causes of the increase in energy consumption in this sector are: the growing population and living standards and therefore, increasing demands for agricultural products, the limitations of cultivatable land area and thus, the need for increase in the yield per area unit, and the low price of fuels and other energetic inputs, especially in Iran. This subject represents the importance of the energy and resources analysis in agriculture. Several researches have been done about the energy consumption in agricultural fields in the world and also different regions of Iran. However, there is a need for a comprehensive study on the obtained results of these researches. In this study, the consumed and produced energy for one of the main crop of Iran (wheat) through the energy indices, obtained from related papers and dissertations, were analyzed. The energy indices were determined as the energy output-input ratio (OIR), energy productivity (EP), energy intensity (EI) and net energy yield (NEY). The results indicated that, the average total energy consumption for wheat production was 34800 MJ/ha in Iran. The mean grain yield was about 4230 kg/ha for normal conditions on irrigated farms. The largest share of energy input was related to nitrogen fertilizer followed by diesel fuel and machinery, responsible for 32, 22 and 15% of the total energy input, respectively. The average OIR was 2.09 MJ/MJ for Iran with the highest and lowest values for provinces of Goldstein (3.72) and Sistan (0.81). The average EI was 8.23 MJ/kg, for Sistan and Baluchestan province being the highest with 17.8 MJ/kg and for Golestan province being the lowest with 3.9 MJ/kg.

Attaching a side-mounted furrower diggers makes it possible to use a rear-mounted machines for digging onion bulbs in broadcast planted farms, avoiding wheeling damages. For this purpose, two types of onion diggers, with and without sifting mechanism have been developed. To compare these machines from technical and economical point of view, an experiment was conducted based on randomized complete block design in Faridan region of Isfahan province, Iran. Results showed that the rod type digger due to inconsistent working depth causes the product weight loss of 2.32%, which is non economical. The product weight losses were 0.15% and 0.16% in blade type digger and sieve chain type digger, respectively, which are negligible compared to that of rod digger. The required labour force for collecting the crop dug by blade type digger was 15% higher than that of chain type digger. The higher labour force in this machine was due to more time and accuracy needed for collecting of bulbs. The 15% saving in labour cost in chain type digger obtained in exchange with a higher purchase price which was three fold compared to that of blade type digger. The economical breakeven points for chain type digger and blade type digger were 5.27 and 1.76 hectares, respectively. In general, the chain type digger proved to be more recommendable for larger farms if high power tractors were available. However, the blade type digger with lower price, simple structure and lower maintenance cost can be a more appropriate option for small farm holders.

Excessive consumption of fossil fuel, as a result of changes in lifestyles and ever increasing population, makes exhaustion of fossil fuels inevitable. In order to reduce the environmental impacts, promoting more efficient use of fossil fuels, deploying energy-saving methods and using alternative sources of energy are all unavoidable options. Solar energy is one of the renewable energy resources that all countries benefit from it in different ways. Iran is one of the sun-rich countries and in its most regions has a radiation rate of approximately 2000 to 2500 kWh/m-2 . One of the suitable technologies for exploitation of this energy is the use of flat plate solar air collectors. Unfortunately, because of the low specific heat of air, the efficiency of these collectors is not high. In this research, in order to improve the performance of this type of collectors, the trapezoid-shaped obstacles were used. Two collectors (SAH112 and SAH113) were used, each having the trapezoid-shaped obstacles with different arrangements. The third one (SAH111) without obstacles was used as a control collector. Air flow was supplied with three identical blowers to all three collectors. Tests were conducted for 7 days starting from July, 8 2016, 8 am to 7 pm in an open area (latitude 38/4°). The results showed that the solar collector outlet temperature in the collector with more obstacles (SAH113) at solar noon was 8.3% higher than that of SAH112, and 16% than SAH111. Static pressure drop in the SAH113 collector was higher than those of two other collectors (about 13/96 Pam-1 ).

Since suitable speed must be selected for every work especially in agricultural activities, feasibility of achieving different speeds by operator under the intended conditions is one that companies take into consideration. These speeds include: creep speed, slow speed, farm speed and transport speed. This study aimed to redesign the gearbox of ITM285 to produce a gearbox which can provide the operator with creeping speed besides the span of speeds already existed. After necessary calculations, the kinematical diagram was prepared, the ratio and size of gears were figured out, and the loads on the gears were examined. Both theoretical and software methods were used for calculate and analysis, and the required modifications were made in dimensions. The involute spur gear was drawn using Geartrax2008, modeled in Solidworks2008, and the analysis was made using Ansys11.0 and Cosmos2008. The loads on the pins and shafts in different gears were calculated and examined in terms of their strength to stand for bending and torsion stresses. Considering the restrictions on redesigning and applying the maximum possible modifications on the dimensions and technical specifications of gears in ITM285 gearbox, it was shown that only making some modifications in the gearbox is not enough to achieve creep speed. Using the final driver of ITM399 with the reduction ratio of 4.8 was thus suggested so that the forward speed of 1.2 km/h was achieved

Evaluation of changes in physical and mechanical characteristics of fruits has special importance for better management of harvesting and storage process of horticultural products. In this study that was conducted in a factorial experiment based on completely randomized design with four replications, the effects of harvesting time and storage duration was studied on changes of physical and mechanical characteristics of 'Bidaneh Sefid' grape fruits. The fruits were harvested at three different stages from 4 September to 29 September at 12 days interval. Fruits stored two months at temperatures of 1±0.5 °C and 90-95% relative humidity. During ripening and cold storage, some of the physical and mechanical characteristics such as TSS, berry density, berry dimensions, cuticle thickness, skin weight, fresh weight, berry dry weight, weight loss, fruits color, firmness, and tensile strength of the skin and tail were evaluated at 20 days interval. The results showed that over harvest time, the density of berry and weight of fruit skin increased and berry cuticle content decreased. Berry fresh weight increased with delay in harvesting and decreased during storage. With increase in ripening degree, a significant increase was observed in the weight loss of fruits during storage. Delay in harvesting, and also during storage period, decrease in firmness of berries and Skin tensile strength was observed. Tail separation force increased for second harvest samples but it decreased for the third harvest one. However, tail tensile strength was maintained at the higher level for harvested samples in the third harvesting time until 40 days storage period.

One of the useful and innovative solutions to solve the problems of agricultural and animal wastes is biogas production from these materials that is valuable and environmentally friendly fuel. In this study, the factors affecting biogas production including C/N ratio, loading rate, retention time and pH were investigated in combination of poultry manure, cattle dung and rice straw. The experiments were carried out in three stages and in each stage three digesters were used in each experiment. The first digester contained the combination of cow manure and rice straw, the second digester contained the combination of cow manure, poultry manure and rice straw, and the third digester was devoted to the cow manure. The ratio of materials to water was approximately 1 to 2 in all digesters. The results showed that the maximum amount of biogas (11200 ml) obtained at the first digester with C/N=27.1, and the minimum biogas (2717.5 ml) was produced in the second digester with C/N=9.81. It was determined that the large reduction in C/N caused a sharp drop in the amount of biogas production so that in the second test at digesters No.2 with C/N=9.81, the rate of biogas production dropped to 97.83 liters. At the third digester with 3 liter loading rate per three days, the maximum biogas production was 472.6 liter during 36 days. Also, the closer pH to neutral resulted in higher performance. Cow manure was resistant against pH changes so it can be used as a stabilizer of the digestion process. In general, adding rice straw to cattle dung increased the amount of produced biogas. Flame test showed that the highest amount of methane in the biogas is in the middle of digestion process.

This study aimed to compare the effects of practices of protective agriculture and conventional methods of farming on soil compaction and the amount of plant residues. The experiments included 9 treatments based on split plot design in a randomized complete block with three replications in Mashhad Agricultural Research Station of Torogh, Iran. The treatments were consisted of three different tillage practices at three levels (1- conventional tillage, 2- reduced tillage, 3- No-tillage) and crop residue management at three levels (1- without residue, 2- retains 30% residue, 3- preserved remains 60%). Some physical parameters of soil such as cone index, bulk density, mean weight diameter and aggregate soil moisture content were measured in this study. The results showed that the effect of various tillage methods on all of the studied indices was significant. The effect of management methods on plant residues were also significant on cone index and moisture content of the soil. The effect of interaction of two factors on cone index for some depths of the soil and soil moisture content was significant.