JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2005 | Volume:6 | Issue:23|Papers Count:13

The present study is concerned with the design and implementation of a computer-based control and monitoring system for greenhouses. For conducting the field experiments a model greenhouse with a floor area of 8 m2, (2×4 m) was constructed. It was covered with double inflated 200 m polyethylene films. Performance of the controller under different environmental conditions was evaluated by installing the system in the model greenhouse. Main components of the system are sensors, a microcontroller, a number of actuators, data processing unit, and data acquisition and recording device. The microcontroller receives data on greenhouse environmental conditions from a number of sensors installed inside as well as outside the greenhouse and transfers the data to and from a PC via RS 232 port. A graphical user interface was also developed to carry out the monitoring tasks. The program implements the control algorithms, comparing the received data with set points, sending control signals to the microcontroller so as to change the states in control devices, namely, heaters, fans, misters, etc., in order to attain the desired set points. To evaluate system performance, a set of experiments were carried out during autumn 2003, in the faculty of agriculture, Karaj. The overall performance of the system in controlling greenhouse air temperature was very satisfactory. The time constant to bring the temperature within the set points was about 10 minutes.

Banana is one of the desired tropical fruits with high nutritive quality. So its planting is in developing southern part of our country. Banana is a climatric fruit which is harvested in maturity stage with green colour. In this research, the effects of physical and chemical treatments on storage life of fruits of Dwarf Cavendish variety was studied. "Fullness index" is the weight devided by the length of an internal fruit of the first or second hand. The Fulness index, proposed by french researchers, was measured in this research. Two different treatments including heat treatment (immersing in 58ºC hot water for about two minutes) and the chemical treatment (immersing in fungicide solution for 5 min) were applied. Then the fruits were packed in two different carton boxes: Carton box covered inside with plastic layer and fruit carton box filled with stuffing. The next step was storing the packages for 25 to 30 days at 13-14 ºC. It has to be mentioned that the control treatments were packed without disinfecting. The result showed that the "Fullness index" was 6.5 to 7.2 which was lower than the proposed index for Cavendish Banana variety. They also indicated that the disinfected treatment (disinfected with Rovral T. S fungicide) led to the more safe fruits. But using other treatment fungal diseases have been seen with white mycelium on the surface of crown of hands. Fruits transferred to laboratory ambient after 25 day cold storage, which were rippened during 2-3 days. But remaining the cold storage condition caused rippenenig after 28-30 days of storage. Measuring quality charachteristics showed that TSS & sugar content were increased in rippening period due to rapidly changing starch to sugar in this stage.

Determination of wetted soil diameter and depth at different times after irrigation commencement is very important for irrigation design. The shape and dimension of wetting front is depended on soil texture, soil hydraulic conductivity, drip discharge and so on. The purpose of this study was to develop some empirical equation for determination of wetting front dimensions at different time after irrigation commencement. This study was undertaken in a plexiglass box with metal frame, dimension of from which one quarter was omitted. Wetting from dimension were measured after irrigation commencement at different times, using depicted lines on side walls of the model. In additional some functions were derived using Backingham theorem, dimension analysis and effective physical parameters on wetted soil volume. The derived functions were calibrated base on some measured data which showed a good agreement with the lab results. This indicates that the derived empirical functions could be used properly for designing tape irrigation system.

Irrigated crop is the main component of Iranian agriculture and 93% of the total extractable water resources is used in this sector. In general, water requirements of field crops is estimated by FAO-Penman-Montieth method based on the data collected from well-irrigated stations (reference stations). However, most of the climatological stations are not located in places where irrigation is practiced and therefore, the use of this data causes an overestimation of reference evapo transpiration. The purpose of the present study was to survey these overestimations after correction according to temperature data nationwide. Data from 153 synoptic stations was used and amount of annual and seasonal overestimation was calculated. Results showed that overestimation was as large as 68% for Spring-Summer in central and west regions and 65% for Autumn-Winter season in central and southeastern regions. This value for annual evapo-transpiration was 41% in southeastern regions.

This research was conducted in khorasan Agricultural and Natural Resources Research Center in order to study the effects of plant oils on extending the storage life of apples in cold storage. The experimental design was structured as factorial with 4 factors, 3 replicates based on compeletely randomized design. Factor A was apple cultivars (Golden Delicious and Red Delicious), factor B was plant oils (canola, corn, sunflower), factor C was oil concentrations (0, 0.25, 0.5, 1, 2, and 3 percent) and factor D was time of sampling from cold storage (0, 45, 90, 120, 150 and 180 days). After treatment the fruits were transferred to cold storage( temperature 0-1 ºC and relative humidity 85%). The results revealed that plant oil had significant effect on pH and decay. Besides, oil concentration had a significant effect on pH, total soluble solids (TSS), TSS/TA, fruit flesh firmness and decay. The results of organoleptic tests showed that plant oil had significant effect on odor and taste. Also fruit texture was affected by and oil concentration. Overally results indicated that corn oil (2%) caused to maintain the qualitative and sensory characteristics of apple cultivars Golden and Red Delicious after 6 months keeping in cold storage.

This research was conducted in khorasan Agricultural and Natural Resources Research Center in order to study the effects of plant oils on extending the storage life of apples in cold storage. The experimental design was structured as factorial with 4 factors, 3 replicates based on compeletely randomized design. Factor A was apple cultivars (Golden Delicious and Red Delicious), factor B was plant oils (canola, corn, sunflower), factor C was oil concentrations (0, 0.25, 0.5, 1, 2, and 3 percent) and factor D was time of sampling from cold storage (0, 45, 90, 120, 150 and 180 days). After treatment the fruits were transferred to cold storage( temperature 0-1 ºC and relative humidity 85%). The results revealed that plant oil had significant effect on pH and decay. Besides, oil concentration had a significant effect on pH, total soluble solids (TSS), TSS/TA, fruit flesh firmness and decay. The results of organoleptic tests showed that plant oil had significant effect on odor and taste. Also fruit texture was affected by and oil concentration. Overally results indicated that corn oil (2%) caused to maintain the qualitative and sensory characteristics of apple cultivars Golden and Red Delicious after 6 months keeping in cold storage.

An experimental dynamic shear test apparatus with reciprocating mechanism was designed and constructed to measure the shear force of paddy stem. The effects of shearing velocity at four levels (0.6, 0.9, 1.2 and 1.5 m/s), and three levels of blade bevel angle (25, 30 and 35 degree) were also investigated on shear strength of four Iranian varieties of paddy, including "Khazar", "Fajr", "Hashemi", and "Binam". Analysis of variance of the data indicated that all the main effects of treatments as well as interaction between variety and shearing velocity affected the shear strength at 1% level of confidence. The maximum and minimum values of shear strength were related to the varieties "Khazar" and "Hashemi" , with mean of 0.210 MPa and 0.181 MPa, respectively. The results of Duncan test indicated no significant differences among the levels of shearing velocity at 0.6 m/s and 1.5 m/s at 1% level. The maximum and minimum shear strength were 0.226 MPa and 0.155 MPa for shearing velocities of 0.6 m/s and 1.5 m/s, respectively. The diference between levels of blade bevel angle was not significant. Interaction between variety and shearing velocity had significan difference on shear strength. The maximum and minimum shear strength were related to "Fajr" with mean of 0.234 MPa at 0.6 m/s, and "Binam" with mean of 0.137 MPa at 1.5 m/s, respectively.

In humid regions, water table control during growing season is a common irrigation method for efficient use of water and optimum crop production. However application of this method in arid and semi arid region is doubtful because of high evaporation rate and salt movement toward the root zone limitations. This research was conducted to examine the possibility of using water table control techniques (i.e., controlled drainage and sub irrigation) in an arid region (e.g., Iran) with special attention to its salinity management. Three water table control treatments including: free drainage (FD), controlled drainage (CD), and sub irrigation (SI) were considered. Treatments were applied in 12 lycimeters (90 cm height, 57 cm diameter). The experimental setup included three treatments and four replications. Water table was set at depth 55 cm from soil surface. The electrical conductivity (EC) of water was 1.5 dS/m. The crop cultivated in lycimeters was tomato. The soil leaching considered to be conducted when EC reached to the plant threshold level (EC = 3 dS/m). The results indicated that SI and CD methods can be used in arid and semi arid conditions. In all the treatments the soil EC was not reach to the crop threshold level. However the EC of soil surface layer in SI treatment was high, but it had not any significant effect on crop yield. The evidence was the higher yield of SI treatment than FD treatment. The total yield of CD was 73% more than FD and 12% more than SI. However the number of tomato fruits in CD treatment was more than the other two treatments (FD, SI). Water consumption in SI was half of CD and FD treatments, and consequently its water productivity (1.4 Kg/m3) was higher than the water productivity for FD (0.57 Kg/m3), and CD (0.97 Kg/m3).

Pistachio is one of the most important horticultural products in Iran and its processing and packaging play major roles in exportation. Drying is a very important step in pistachio processing. In this step kernel moisture content decreases to 4-6 percent (d.b.), which is suitable for storage condition. The equilibrium moisture content (EMC) has important effects on drying time and kernel quality. In this research, pistachio moisture desorption isotherms were obtained at different drying temperatures (45, 60, 75, and 90ºC) for two split Iranian pistachio varieties: Kalehghouchi and Fandoghi. For this purpose, static method and saturated salts were used based on COST-90 procedure. The results were evaluated by several models including: GAB, Smith, Henderson, Halsy and Oswin. The experimental results showed that for each variety, EMC values were reduced by increasing temperature. At different temperatures, GAB and Smith models gave better fitness for the data compared to the other models. Increasing temperature caused the reduction of mono layer moisture content in pistachio. Also, regression equations were obtained for estimation of mono layer moisture content at 45- 90ºC for each variety.

The saturated hydraulic conductivity Ks and the effective porosity f are needed for modeling and many applications in drainage. The current design procedure is based upon calculation of the lateral spacing, using some average values of Ks and f within the area to be drained. The objective of this study was to take into account the spatial and temporal variability of these parameters and to introduce a new method for simultaneous estimation of Ks and f. The proposed method was based upon measuring water table profiles at different times. The an steady model of Glover-Dumm (1954) for predicting water table profiles was used with a nonlinear optimization technique to find the optimum values for Ks and f. Different data sets from the conducted experiments and literatures were used for calibration, using nonlinear optimization technique. A physical drainage model of 2.2 m length, 0.3 m width and 0.5 m hight was established in the laboratory and carefully packed with a sandy loam soil. A perforated drainage pipe of 4.5 cm diameter was established at the bottom end of the model. Some 16 piezometers were inserted in the soil for spatial and temporal water table monitoring. The proposed approach was evaluated with both constant and variable f. The pridicted values with new coefficiante showed of the new approach showed good agreement with the measured ones. With variable effective porosity the mothed is even much more successful to predict water table profiles.

Hydraulic conductivity is one of the soil"s dynamic properties, which plays a major role in water flow and salts transport within the soil. A saturated hydraulic conductivity value is needed for drainage projects design, which is almost constant. Different methods can be used in determining insitu hydraulic conductivity and they can be divided into two groups, e.g. above and below water table methods. Preliminary investigations showed that there was a significant difference between the results of these methods. The objectives of this study were 1) to investigate and compare the hydraulic conductivity values obtained using the above-mentioned methods in Iran and other countries; 2) to find the reasons of differences between the results of these two methods; and 3) to present practical solutions to minimize these differences. Generally, the results obtained by the above water table method were lower than those of under water table one. Based on the results of this research, values of under water table method were 0.5 to 32 times bigger than those of the above water table method. The reason for such a difference can be explained by various factors, e.g. water quality, the collapse of well walls, trapped air bubbles within soil pore, and the difference in flow patterns. Lower values obtained by the above water table method compare with under water table one may indicate that the saturated hydraulic conductivity cannot be accurately determined using the above water table method. Therefore, the results of this kind of method need to be closer to those of under water table one. In this regard, the suitable methods can be ranked as following: Natural model method, field model method, geostatitical method, Macnill method and correlation between texture and structure method.