JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2014 | Volume:14 | Issue:4|Papers Count:10

The table grape (Vitis viniferal) is a non-climacteric fruit with a relatively low rate of physiological activity and is subject to serious water loss after harvest that can result in dry brown stems, shattered grapes, and wilted and shriveled grapes. Grapes can be stored for a short time, but increasing living standards have increased the demand for fresh grapes in Iran. The possible introduction of new grape varieties of good quality with long shelf lives has been a focus of attention. The present study compared the performance of 8 Torkaman cultivars and 3 local cultivars (Koladary, Kajangor, Rezghy). The result showed that the Torkaman cultivars had good quality and quantity characteristics and, most importantly, longer shelf lives and are recommended as potential varieties for cultivation.

Starch is a major source of energy in the human diet. Physical, chemical, and enzymatic modifications provide changes that are not available or controllable in commercially available native starches. The effect of one physical treatment, ultrasound, was investigated on the crystallinity and microscopic properties of rice starch. In this research, rice starch despersions (8%) were sonicated and scanning electron microscopy and light microscopy were used to study the morphological changes to the rice starch granules. The dried samples were analyzed using x-ray diffraction to evaluate the crystalline fraction of the starches. Response surface methodology was used to evaluate the effects of temperature (45-65 oC), time (10-300 s), and amplitude (0%-100%) on the crystallinity and microscopic properties of rice starch granules. The results showed that ultrasound did not change the x-ray diffraction pattern (A type) and that crystallinity decreased as the temperature and time increased. Higher temperatures and amplitudes decreased the degree of crystallinity in rice starch. When temperature, time, and amplitude increased simultaneously, some granules started to lose their polyhedral shapes, and pores and fissures were detected on the surface of the granules.

The present study developed an improved nanocomposite based on polylactic acid (PLA) biopolymer. The structural properties of PLA nanocomposites of clay and cellulose nanoparticles were evaluated for level and water vapor permeability (WVP) using thermal and casting methods. Thermal tests (DSC) showed that pure PLA had a glass transition point (Tg) of 53.83, a melting point (Tm) of 153.95oC and crystallization (x%) of 41.36%. With the incorporation of clay nanoparticles, Tg and x% increased, while Tm showed no significant change. The micro-crystal cellulose (MCC) nanoparticles were not compatible with the polymer matrix, so there was no effect on the thermal properties. WVP results showed that pure PLA had high permeability; the addition of clay nanoparticles strongly decreased WVP. The sample with 7% clay had a permeability of 0.92×10-11 g/m.S.Pa. WVP of the film increased significantly as a result of the hydrophilic nature of the MCC. The SEM images of the samples confirmed the results.

Simulation models of the effect of water on crop yield are valuable tools for improving on-farm water management and water productivity. The AquaCrop model has recently been developed by the FAO to predict crop productivity, net water requirements, and water use efficiency for different scenarios, including rainfed and limited irrigation. The model is suitable for evaluating different regions and crops.The present research examined the efficiency of the AquaCrop model for simulating yield, soil moisture content, and crop canopy response to water availability for wheat in rainfed areas. The region under study in Iran was the upper Karkheh River basin in the Selseleh region of Lorestan province during 2005-2007. The on-farm trials included three irrigation treatments (rainfed, single irrigation only at planting time, single irrigation only in spring). To evaluate the model performance and accuracy of prediction, maximum error, normalized root mean square error, and index of agreement were computed from observed and simulated variables (grain yield, soil moisture content, evapotranspiration). The reliability index of normalized RMSE was 8.34% to 10.56% and of efficiency was 0.78 to 0.93. This indicates that the model was able to accurately simulate soil water content of the root zone, grain yield, and crop canopy under research conditions when compared with field data. The d-statistic indicates that the closer the index value is to unity, the better the agreement between the two variables compared and vice versa. The AquaCrop model for estimation of sowing date under rainfed conditions was not efficient because it required a minimum value for precipitation. The model performed satisfactorily for simulation of grain yield, soil water content, and crop canopy for the rainfed and limited irrigation treatments. The AquaCrop requires minimal input data that is readily available or can easily be collected, making it a user-friendly option for users.

The latest recommendations of the International Commission on Irrigation and Drainage from the 8th Micro-irrigation Congress held in 2011 in Iran was to develop a global orientation for subsurface microirrigation methods. The congress focused attention on the international dimensions of water scarcity, especially in arid and semi-arid regions of the world. Aridity and the cumulative effect of successive droughts in Iran have made the clay subsurface irrigation system of concern to farmers, experts, and researchers. Although this irrigation method is traditional and has both advantages and disadvantages over other subsurface micro-irrigation methods, with modification to its mechanism, it can be a suitable application for Iran. The hydraulic properties of porous clay capsules have a major effect on the performance of clay subsurface irrigation systems. The present study determined the relationship between seepage rate-time and seepage rate-hydrostatic pressure of porous clay capsules used in clay subsurface irrigation systems. The experiments examined three soil textures (sandy loam, silty clay loam, silty clay) under actual field conditions on the large scale. They were conducted as a randomized complete block design with a split plot layout and three replications. The results obtained over three months of operation at 2, 3 and 4 m of hydrostatic pressure show that the daily seepage rate of porous clay capsules were significantly affected by soil texture. In addition, the effect of operating pressure on the seepage rate of porous clay capsules in the three soils was significant. Also, the results of testing of seepage ratehydrostatic pressure over a two-week period for the three soil types showed a nonlinear relationship (power) between the two irrigation system design factors. The best hydrostatic pressure for porous clay capsules in the three soil textures was 3.5-4 m.

Two types of paddy combine harvester (head-feed and whole-crop) are commonly available in different widths in developed countries. The use of combine harvesters can greatly decrease labor costs and efficiency. Combine harvesters have been introduced in several East Asian countries (China, Japan, South Korea) to decrease costs, but their technical and economic performance has not yet been studied. The current study examined three combine harvesters with different mechanisms and widths: Iseki (2 rows, head-feed; Japan), Kukje (3 rows, head-feed, South Korea); Jiangsu (whole-crop, China). The experiment was conducted in a randomized complete block design with three replications. The results showed that there were significant differences between treatments for field efficiency, loss, feed rate, theoretical and effective field capacity, and cost per ha. There was no significant difference in slippage among the combine harvesters. The whole-crop combine had the highest rate of loss at 1.74% (excluding natural loss) and soil compaction. The whole-crop combined cost per ha was lowest at 1.3873 million rials. It can be concluded that the whole-crop combine performed the best of the tested combines.

Concentration decreases the amount of water in liquid food and increases shelf life. Several types of evaporators are used for concentration, thus, it is necessary to simulate the process before design to control efficiency. The flow of pomegranate juice was simulated in a forward-feed flat plate evaporator at concentrations of 18 to 50 Brix in a two-phase mixture model using computational fluid dynamics. The results show that a vacuum developed in the evaporator column causing a slight drop in pressure at the inlet. Temperature increased at high intensities at the flow entrance zone. The magnitude of the velocity of the vapor increased as the flow increased from the inlet toward the outlet of the evaporator. Radial velocity was at a maximum in the middle of the flow medium and decreased gradually toward the boundary layer. The volume fraction of the pomegranate juice decreased and the volume fraction of the steam increased gradually from the inlet toward the outlet of the evaporator. This model can be applied for other liquids, but it is first necessary to define the thermo-physical properties of the liquid at different concentrations.

Walnuts are one of the most important nut crops worldwide. The area under cultivation increases every year. In 2008, the Food and Agriculture Organization reported exports of about $17.1 billion. The country of Iran is the 4th largest producer of walnuts in the world. Stages from production to consumption are very important, because the condition and quality of the shelled nutmeats affects the marketable yield. The present study fabricated a single-shelled barrel-type walnut cracker and assessed it for quality at 4 sizes of nutmeat, 4 rotor speeds, and 4 humidity levels with three replications. The results of statistical analysis found that the best quality nutmeats were achieved at 10% to 14% moisture (level 1), 280 rpm rotor speed, and 55.30-75.31 mm walnut size (Juglans regia).