JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2008 | Volume:8 | Issue:4|Papers Count:20

Both arid and semi-arid regions, which make up the greatest portion of the earth, suffer from a lack of precipitation and unsuitable water distribution. The agricultural sector consumes most of the fresh water resources in comparison with other sectors. Thus, it is important to increase water use efficiency (WUE) and practical ways to maintain soil water. Superabsorbent polymers are water containers that absorb and retain large quantities of water when applied to the soil. These materials release the absorbed water, allowing the plants to consume adequate amounts of water at all growth stages. This study investigated the cyclic swelling behavior of superabsorbent polymers. Two polymers, TA-100 and TA-200, were applied to loamy and sandy soils. The treatment levels consisted of 0, 0.25, 0.5, 0.75 and 1 gr of both polymers per kg of dry-weighed soil in 3 replicates. The water content for each treatment was measured at 0, 100, 300, 500, 1000, 3000, 5000 and 15000 kPa and soil water retention curves (WRC) were obtained for each soil sample. The samples were then oven-dried and re-wetted five times and the WRCs were again obtained. The results indicated that, by applying more polymers to the soil, the water content at any soil water pressure head increased. However, this influence declined for the next four drying-wetting cycles. The most dominant influence of the superabsorbent polymers on water retention for each drying-wetting cycle appeared in the lower soil water pressure heads (0-5000 kPa). A comparison of the TA-100 and TA-200 polymers indicated that the TA-200 has a larger water retention capacity and also appeared to absorb more water than did the TA-100 during the subsequent four cycles. Parametric analysis of the retention curves indicated that qs, n and qr parameters in all treatments increased when more polymer was applied. However, the variation of magnitude of qr was small. It was also observed that when any type of superabsorbent was applied, the a parameter decreased in sandy soil and increased in loamy soil.

This research was conducted at the Shahrood Agricultural Research Center in 1382 and 1383 to study the effect of alternate furrow irrigation on potato yield and its economic evaluation. The experimental design was a randomize complete block design and the treatments were: every furrow irrigation (EFI), fixed alternate furrow irrigation (FAFI), variable alternate furrow irrigation (VAFI), fixed alternate furrow irrigation to onset of tuber setting (FAFIB), fixed alternate furrow irrigation to end of tuber setting (FAFIE), variable alternate furrow irrigation to onset tuber setting (VAFIB), variable alternate furrow irrigation to end of tuber setting (VAFIE). The water requirement was calculated based on the Penman-Montith method at each irrigation time and the water was supplied to each treatment using a volumetric meter and polyethylene. Results showed for FAFI and VAFI, plant height, tuber number for each plant, average weight of tubers and yield were considerably reduced. There was no difference between EFI and the other treatments (FAFIB, FAFIE, VAFIB, VAFIE). Water usage can be reduced at the first growth stages and the end of the tuber forming stage with suitable irrigation management without yield reduction. For the economic analysis, the partial budgeting method and marginal benefit-cost ratio were applied. Economic analysis showed that the benefit-cost ratio was 3.03 for VAFIE and water usage was reduced from 8632 m3/ha (EFI) to 7250 m3/ha (VAFIE), saving 1384.7 m3/ha water. As a result, it is recommended to irrigate a crop based on the VAFIE treatment. In this way, without significant yield reduction, water usage and labor cost are reduced.

A canola seed pneumatic conveyor was designed and constructed to convey canola seed at a 90 g/hr mass flow rate through a 58 mm diameter pipe. Physical and aerodynamic properties of the canola seed that are critical to the design process were measured. System pressure drop, comprising air pressure drop and solid pressure drop and which is the most important aspect of pneumatic conveyor design, was calculated. After pressure drop calculation and selection of a suitable centrifugal blower, rotary feeder, power transport mechanism, pressure drop measurement station and frame were constructed. These sections were combined and the conveyor was completed. The ventilation velocity of the seeds was 11.47 m/s practically, which was greater than the value predicted by theoretical equations. The changing internal air velocity of the blower (13.03, 14.11, 14.83, 15.18, 15.29 m/s), the mass flow rate (50, 70, 90 kg/hr) and the length of the transport pipe (2, 4 m) were measured and the horizontal pressure drop of the system was measured using a pitot tube and oblique monometer. The effects of these parameters were evaluated and a regression model of variable parameters for horizontal pressure drop is presented.

Vibration from the operation of industrial implements can be harmful to the human body. These implements, such as the power tiller or hand tractor often used to till rice in northern Iran, can vibrate the entire body or one part, particularly the hands. In this research, the transmissibility and effects of vibration from a Mitsubishi power tiller of 7.7 hp and 2400 rpm on the operator’s health was evaluated. The experiments were conducted in two positions (moving by hand and tilling), five speeds (1600, 1800, 2000, 2200, 2400 rpm), at three points (power tiller grip, operator’s arm, operator’s chest), and three modes (vertical, lateral, longitudinal). It was observed that with an increase in engine speed at the three points, the total acceleration value, ahv, increases. It was also observed that the dominant frequency of vibration at all points and modes corresponds to the piston strokes or revolutions per second of the motor. It was observed that the value of exposure to vibrations in an eight-hour work day, A(8), was 19.14 m/s2, which is more than the standard value of 2 m/s2 that is known to cause health disorders in the operator. It is predicted that use at this exposure will cause blanching of the fingers and vascular disorders of the hands for 10% of the machine operators within two years.

Drying is one of the most important steps in raisin processing. During this step, initial moisture content decreases up to 15-17% (db) for suitable storage. Achieving optimum drying conditions can affect the processing time and improve raisin quality. Temperature, air velocity and pretreatment are important factors in the quality of the grape drying process. In this research, the effect of temperature at 50oC, 60oC, 70oC, and 80oC, air velocity at 1, 2 and 3 m/s, and four pretreatments (hot water, 5% potassium carbonate, 0.4% olive oil, 0.5% sodium hydracids) and no pretreatment were measured. Diffusivity and activation energy of all treatments were determined. The results of ANOVA showed that temperature, air velocity and pretreatment have significant effects on drying time and average drying rate. Pretreatment has a significant effect on the drying process and decreases the drying time up to 69% at some temperature levels. Also, increasing the temperature decreases drying time up to 66% for some pretreatments. Increasing the hot air velocity decreases it about 8.6%.

To study the effect of planting pattern and water quantity on potato yields under drip irrigation, this research was conducted using a split plot based on a randomized complete block design with four replications in three regions (Mashhad, Ardebil and Damavand, Iran) during 2003-2004. Nine treatments were used. The main-plots were three levels of irrigation: 100%(I1), 80%(I2), and 60%(I3) of crop water requirement. Three planting pattern were used in the sub plots: B1, the distance between cultivation rows being 75cm using one drip irrigation lateral line, B2, two cultivation rows with a 35cm distance and one drip irrigation lateral line between rows (distance between laterals = 135cm), and B3, two cultivation rows with a distance of 45cm and one drip irrigation lateral line between rows (the distance between laterals = 150cm). Results showed that the B2 planting pattern had the highest total yield and economic yield in three regions. There was a significant difference between the B1 and B3 treatments in Ardebil, but no significant difference in Mashhad and Damavand. The B2 had the longest tube yield (35-55mm) for the three regions. Water use efficiency (WUE) of the B2 planting pattern was greater than for the B1 and B3, the difference being significant in Ardebil and Damavand, but not in Mashhad. Water stress led to a reduction of the total tube yield, economic yield and WUE. The highest tube yield (35-55 and more than 55mm) was measured when total crop water requirement (I1) was applied and showed a significant difference with I2 and I3 in Mashhad and Ardebil. There was same results for WUE. Accordingly, drip irrigation was suggested for potato cultivation when 100% of crop water requirement was applied.

The sensitivity of plants to salinity varies during growth season. Most plants are resistant at the germination stage, but at the seedling or earlier growth stages become more sensitive to salinity. Their tolerance usually increases with age. The salt tolerance of different plants has been extensively studied, however, the results have either been qualitative or expressed as average values of root zone salinity for the whole growth season. Thus, developing appropriate models for quantitative characterization of plant response to salinity at different growth stages is essential. Consequently, canola, a plant of high economic value, was selected for this study. Three vegetative stages for canola (seedling, rosette, bud) are recognized. A greenhouse study was conducted in a natural saline loamy sand soil, using salinity treatments comprising one non-saline water (tap water) and eight natural saline waters of 3-17 dS.m-1.Canola plants were irrigated with tap water before the desired stage and then the salinity treatments were applied. Maas and Hoffman (1977), van Genuchten and Hoffman (1984), Dirksen et al., (1993), and Homaee et al., (2002b) models were used to predict relative seedling number and relative transpiration (Ta/Tp). To compare the models and their efficiency, the maximum error, root mean square error, coefficient of determination, modeling efficiency and coefficient of residual Maas were calculated. Results indicate that the Maas and Hoffman (1977) model provides a reasonable prediction at the seedling stage while the Homaee et al. (2002b) model provides better predictions at the rosette and bud growth stages.

Volume estimation of most agricultural products using mathematical methods is not accurate because of their irregular shape. An alternative method is image processing, which can be used in continuous sorting machines. The objective of this study is to find a practical method for volume estimation of potatoes using image processing. Fifty potatoes (Marfona variety) were selected as experimental samples. An image was captured from two perpendicular views of each potato sample using a digital camera and a flat mirror. The image was then processed with MATLAB software and the potato's dimensions were measured based on the edge position in the image index matrix. After imaging, the potato volume was estimated by two methods. In the first, volume was determined using an experimental equation based on three perpendicular diameters. In the second, the sum of calculated section volumes from image division into smaller truncated cone sections with elliptical bases was used. The size of the three perpendicular diameters and the length of the truncated cone sections were measured using image processing. After measuring the actual volume of the potato samples by water displacement, the error of the estimated volume of both methods was calculated and compared. Results showed that the image division method using 64 sections estimates potato volume more accurately (8.15% error) than the experimental equation method (20.5% error). Thus, the image division method can be recommended as a practical method for potato grading based on volume.

Paddy de-awning using a de-awner increases the uniformity and flow rate of paddy grains through the orifices of hoppers, bucket elevators and chutes. In this study the effects of paddy variety, rotational blade speed and moisture content on performance of a prototype de-awner machine were investigated. The experiment was conducted in a factorial design with three factors, variety (Hashemi and Binam), blade rotational speeds (600, 700, 800, 900 and 1000 rpm) and paddy moisture content (9, 11, 13 and 15% wb) in a completely randomized design with three replications. The results revealed that the effect of variety was significant for de-awning efficiency (P<0.05) and cracked grains (P<0.01). The blade rotational speed significantly affected de-awning efficiency, broken, de-husked paddy (P<0.01) and cracked grains (P<0.05). The paddy moisture content significantly (P<0.01) affected de-awning efficiency and broken paddy. The de-awning efficiency increased from 45.33 to 80.33%, broken paddy from 0.59 to 1.14%, de-husked paddy from 0.56 to 1.11% and cracked grains from 5.50 to 7.63% as the blade rotational speed increased from 600 to 1000 rpm. When moisture content increased from 9 to 15% wb, de-awning efficiency decreased from 75.03 to 57.90%, broken paddy from 0.92 to 0.77%, de-husked paddy from 0.81 to 0.74% and cracked grains from 6.73 to 6.10%. The de-awning efficiency of the Hashemi variety was higher than that for the Binam variety. The appropriate blade rotational speed was 700-800 rpm and paddy moisture content was 9-11% wb.

The purpose of this research was to determine the effect of modified atmosphere packaging (MAP) containing high carbon dioxide gas concentrations on the quality of Sayer dates, to be used as a safe alternative to methyl bromide fumigation. Different percentages of gases (85% CO2 + 3% O2 + 12% N2, 75% CO2 + 12% O2 + 13% N2, 34% CO2 + 37% O2 + 29% N2) were injected into the cellophane packages. The control samples were cellophane packages with normal atmosphere content and simple heat seals. The packages were stored at 4oC and 30oC and sampled after 30, 60, 90 and 150 days of storage. The dates were tested for sugar spotting, blemish formation, pH value, water activity (aw), survival of Oryzaephilus surinemensis insects, and mold and yeast counts. The samples were analyzed in three replications using a randomized complete factorial design. The percentage of insects and the mold and yeast counts were highest in the control samples stored at 30oC and the lowest values were in packages containing 85% CO2 + 3% O2 + 12% N2. The lowest pH value was found in samples in MAP with 34% CO2 + 37% O2 stored at 30ºC. Samples stored at 30oC had a significantly lower pH values than did those at 4oC (p<0.05). Gas concentration did not have a significant effect on blemishing but the interaction effect of gas concentration and period of storage was significant (p<0.05). Increasing CO2 concentration had a significant effect on the reduction of sugar spotting with the least sugar spotting percentages reported in MAP containing 85% CO2 + 3% O2 + 12% N2 (p<0.05). Overall, the MAP treatment of samples containing 85% CO2 + 3% O2 + 12% N2 and stored at 4o C was considered the most suitable for Sayer date fruit preservation and disinfestation.