نشریه تحقیقات سامانه ها و مکانیزاسیون کشاورزی
پیاپی 76 (زمستان 1399)

Wild oat (Avena fatua) is the most common weed of wheat fields. Given that the presence of even small amounts of wild oat in the wheat grain mass may lead to a sharp drop in the quality of flour produced, separation of wild oat from wheat will increase the purity of the seed and enhance the economic value of the crop. In present study, some physical properties of wheat and wild oat, including geometric properties, gravity properties, frictional properties and initial moisture content were determened. A gravity separator - equipped with some tools to adjust  five parameters: air flow rate, frequency of oscillation, amplitude of oscillation, longitudinal slope and latitudinal slope of the table - was used to separate wild oats from wheat grain mass. The effects of these parameters were studied to achieve maximum separation of wild oat from wheat mass. Statistical analyses were performed in two factorial experiments in a completely randomized design. Also, using dimensional analysis, a dimensionless dimensional parameter V/aω was obtained (where v is air speed, a is oscillation and ω is oscillation frequency), which was effective in evaluating the effect and reducing the number of parameters. The results showed significant differences (1%) in moisture content, mass and particle density, boundary velocity and interaction between grain type and friction surface between two grain types. Also, the results indicated that the maximum separation of wild oats from wheat (70.47%) was obtained when the air flow rate was 6 m/s, the oscillation was 5 mm, the oscillation frequency was 395 cycl/min,, and the longitudinal slope and latitudinal slope were 2.5° and 1.5°, respectively.

Among renewable and clean energies, geothermal energy is superior to other types of energy, and unlike other renewable energies, it is not limited to the season, time, and conditions. One of the applications of geothermal energy is the use of ground heat at shallow depths as the earth-air heat exchanger (EAHE), which is used as a modern and effective technique for preheating the air in the winter and vice versa precooling in the summer. In this study, the design of an EAHE converter for a commercial greenhouse for heating or cooling purposes was examined. A one-dimensional model of the EAHE system was developed to evaluate the effects of main parameters such as diameter, length, air flow rate, and fan power and system efficiency. Given the direct relationship between number of the transfer units (NTU) and the effictiveness of EAHE (ε), it is possible to construct an EAHE system in order to obtain an appropriate NTU and its ε and handle the design of an EAHE system to a point where these two parameters will be obtained with the desired values. By the model and method presented in this study, the effects of main parameters as the effective design factors can be simply assessed without any waste of energy and time and complexity.

In some parts of Iran, wheat will be grown up upon harvesting of previous crop, rice.  Leaving over paddy stems, as plant residues, could be a good solution due to limitation of time between harvesting of rice and preparing the land for sowing wheat. On the other hand, the presence of rice residues can affect the performance of the direct planter and consequently on the yield of wheat. This study was conducted in Khuzestan province, Iran, for two years (2015-2017) to investigate the effects of height of standing rice residues, stubble height, on grain yield of wheat when direct planting machine, Gaspardo machine, was used to sow the seeds. The experiment of this project was based on split plot with randomized complete blocks design with two factors and three replications. The main factor was the rice stubble height at three levels: 25, 35 and 45 cm, and the sub factors were the wheat seed rates at three levels: 160, 180 and 200 kg.ha-1.Analysis of variance in two years showed that stubble height and seed rates had significant effects on grain yield but interaction of them had no significant effect in this index. In addition to grain yield, stubble height caused significant effects on biological yield, seedlings per m2of land, and the number of grains per spike.  Based on average of two years grain yield, it has been found that among stubble height, 25 cm with 4634 kg.ha-1and 45 cm with 3894 kg.ha-1had the highest and lowest value, respectively. From the point of biological yield, the highest (10524 kg.ha-1) and lowest (8894 kg.ha-1) value were found when the height of stubbles were 25 cm and 45 cm, respectively.

Rapid diagnosis of plant diseases has always been an important challenge for the agricultural industry. One of the approaches that has been welcomed in this field is the use of image processing methods. The advantage of these methods is that they are automatic, fast, low cost, non-destructive and accurate. In this article efforts were focuced on distinguishing automatically healthy plants from unhealthy ones and also diagnosing the types and severity of their disease, by processing the images of the leaves of plants and agricultural products. To do this, deep learning-based methods including several different architectures of convolutional neural networks were used along with a support vector machine classifier. The proposed method in this study can be generalized to different plants and products as well as several plants simultaneously. The designed networks were evaluated using two different subsets of Plant Village data sets. In the first subset, which was related to the diagnosis of apple tree disease in four different classes, the accuracy was 95%, and in the second subset, which was related to four different plants in ten classes, the accuracy was 96.8%. Evaluation results showed that combining the support vector machine classifier with deep learning networks improved plant disease detection accuracy.

Increasing in consumption of fossil fuels and their price and environmental impacts, have led to a growing need and interest in replacement of these fuels with new and renewable energy sources. Anaerobic digestion is one of the attractive methods to produce biogas from organic matter.Wet state and solid state arethe categories of anaerobic digestion. Some benefits of solid-state anaerobic digestion (SS-AD) include the need for smaller reactor capacity requirements, less energy used for heating, and easier handling.In this study, SS-AD of organic fraction of municipal solid waste (OFMSW) was examined. The study was done in the laboratory scale of (1-liter volume), mesophiliccondition (37°C), and 20% solid content. Characterization of OFMSW indicated good potential of these materials to produce biogas through SS-AD (69.37% of total solids, 76.2% of volatile solids, and a C/N ratio of 38.28%). According to the results of SS-AD, a total of 372 ml biogas/g of volatile solids was obtained under normal laboratory conditions, of which 230 ml (61.82%) was methane. Also, a reduction of 64.7% was obtained for volatile solids, which is one of the parameters of the experiment productivity.

In urban environments, root growth is limited because of limitation of soil and some problems the plants are faced with, for example soil compaction. The aim of this study was to build and evaluate a device that could improve the existing deficiencies for tree roots by increasing soil porosity and permeability through air injection. After construction of the machine, weighing 240 kg, equipped with a 7.5 HP engine and maximum injection pressure of 12 bar, the effects of machine operation and some important physical properties of soil such as porosity and infiltration were investigated. Multiple linear regression was used to investigate the relationship between the independent variables of the device including air pressure at 3 levels (4, 8 and 12 bars) and depth at 2 levels (30 and 60 cm) and the dependent variable of porosity. The results showed a significant regression model among the variables. Also, the regression model estimation error was 1.75%. Based on the results, the system can be reliably designed and manufactured to inject air into the soil to increase porosity.

The current study quantified the effects of culture media and environmental factors (temperature and pH) on factors in the production of microalgae Spirulina platensis by photobioreactor. The culture of microalgae was done separately in Walne, BBM, and Jordan media. Temperature, pH, and light intensity (5000 lux for all stages and 16 hours per day) were applied in each culture medium separately. Cell density, biomass, lipid percentage, chlorophyll a, and carotenoids were measured for all treatments. The differences in parameter's effects were assessed by SPSS software. The results showed a significant difference at 1% in cell density, biomass, chlorophyll, carotenoid, and lipid content in the Walne, BBM, and Jordan culture medium at pH (8±0.5&10±0.5) and temperature (25 & 30 °C), respectively. Average data revealed that  the highest cell density, amount of chlorophyll a, the number of carotenoids were found in  M1T1P1 treatment (Walne culture medium at 25 ◦C and PH=8±0.5), and the lowest amount was found in  M2T2P2 treatment (BBM culture medium at 30 °C and PH10±0.5). In terms of biomass, the highest levels were obtained in M3T1P1 treatment (Jordan culture medium at 25 °C and PH=8±0.5). Conclusions showed that Walne medium culture at pH=9 and temp 25 °C was suitable for microalgae of Spirulina. But from the point of the cost of culture medium, Jordan culture medium seemed to be more economical.The results showed that there was a significant difference at 1% in cell density, biomass, chlorophyll, carotenoid, and lipid content in the walne, BBM, and Jordan culture medium at pH (8±0.5&10±0.5) and temperature (25 & 30 °C), respectively. According to the results of comparing the average data, the highest cell density, chlorophyll a, the number of carotenoids related to M1T1P1 treatment (walne culture medium with 25 ◦C and PH8±0.5), and the lowest amount related to M2T2P2 treatment (BBM culture medium with 30 °C and PH10±0.5 (In terms of biomass, the highest levels were obtained with M3T1P1 treatment (Jordan culture medium at 25 °C and PH8±0.5). The present study, with a scientific criterion, showed that Walne medium culture with PH9 and temp 25 °C was suitable for microalgae of Spirulina. But due to the cost of culture medium, Jordan culture medium is more economical.