JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2008 | Volume:9 | Issue:1|Papers Count:13

Peanuts, an oilseed crop, contain about 46% oil. The peanut shell can be used as fuel or pallets and its dry matter as feedstuff. The whole pods consist of 1-6 kernels. Shelling is done at harvest time when the pod moisture content is 5-10%. In this research, a peanut sheller was designed and developed to separate the shell from the pod. The sheller included a hopper, sheller cylinder, concave, kernel tray, fan, electric motor, belt, pulley, frame, cover and bearings. Four cylinder speeds (4, 5, 6, 7 m/s) and four clearance levels between the sheller cylinder and concave (8, 12, 16, 20 mm) were tested. The effect of cylinder speed and clearance on shelling efficiency and peanut breakage was investigated. The experimental design was factorial with a completely randomized block design. The results indicated that cylinder speeds of 5 to 7 m/s and a clearance of 12 mm produced maximum shelling efficiency and minimum kernel breakage.

An important problem in performance evaluations of irrigation systems is the difficulty of the determining share of structural and operational elements and determining improvement solutions. In most studies, the combined impact of structural and operational elements on the performance of irrigation systems is assessed. Some researchers try to separate the effects of structural and operational elements, but ambiguity in the proposed indicators affects the accuracy of the separation. In this research, separate indicators for the performance evaluation of irrigation systems are defined. By considering the objectives of water distribution and the interaction of operational and structural elements on the performance of the system, indicators for depth of water and delivered flow are defined. Two other sets of indicators are defined to accommodate the importance of operation timing and flexibility of irrigation systems in meeting water user requirements. To test the applicability of the indicators, an operational scenario was assessed for the E1R1 canal of the Dez irrigation network. To evaluate this scenario and its appropriate improvement options, the canal was simulated using an ICSS hydrodynamic model. The results for this scenario show that the total, structural and operation depth deficit indicators are 78%, 90%, and 86%, respectively. The total, structural, and operational adequacy indicators are 96%, 94%, and 90%, respectively. The improvement option improved the operational, structural and overall depth deficit indices by 12%, 7% and 18%, respectively. In addition, operational, structural and overall adequacy indices for the improvement option improved by 9%, 4% and 13%, respectively. The results show the capability of the proposed indicators in determining the share of structural and operational elements on the performance of an irrigation system which can be easily used to prioritize improvement options.

The effect on sugar beets of water and nitrogen movement in the soil under different water conditions was assessed over two years (2000-1) at the Khorasan Agricultural Research Center. Three water treatments (no water stress, continuous stress and primary stress) and three N amounts (80, 160 and 240 kg N/ha) were investigated. The amount of moisture depletion in the water treatments was 50%, 80% and 90%, respectively. The leaching estimation and chemistry model (LEACHM) is a process-based model developed by Hutson and Wagenet (1992) that describes water and solute movement, transformation, plant uptake and chemical reactions in unsaturated soils. The model applies numerical techniques to the Richard’s water flow equation and the convection dispersion equation (CDE) using finite difference methods. The LEACHM model contains four modules: LEACH-W simulates only the water regime, LEACH-N simulates nitrogen transport and transformation, LEACH-P simulates the pesticide displacement and degration, LEACH-C simulates the transient movement of inorganic ions. LEACH-N, the version of LEACHM that addresses N dynamics, was selected for this study because it has subroutines to calculate water flow, NO3 leaching, evapotranspiration, heat flow, rate content adjustments for temperature and water content, N transformations and uptake. Mineralization, nitrification, denitrification and volatilization are the major N transformation processes modeled by LEACH-N. The model predicted the amounts of moisture, ammonium and nitrate in the soil with acceptable precision. The correlation between the measured and predicted amounts was significant at the 1% level. Immediately after the application of N, the amounts of ammonium and nitrate in the surface layers increased sharply. The amount of ammonium in the surface layers was less for the non-stress treatment than the other treatments. Ammonium and nitrate uptake decreased at the time of stress, but increased after stress. By increasing the soil depth, the amount of nitrate in the non-stress treatment increased. In stress treatments, the amount of N losses caused by ammonium volatilization, denitrification and nitrate leaching decreased.

Hydraulic simulation of water flow in irrigation canals may reveal management shortcomings and help managers find solutions to them. Hydraulic simulation models can be appropriate tools for understanding hydraulic behavior of irrigation systems. In the present study, the steady state HEC-RAS model was tested and compared with the MIKE 11 unsteady state model. A secondary irrigation canal in the Doroodzan irrigation system in southwest Iran was selected to test the models. The control structures in the system were radial gates and sluiced orifices. New discharge algorithms were obtained for the free flow radial gates using previously published measured laboratory and field data and applied to the HEC-RAS model. The two models were calibrated and validated using two sets of observed discharges, gate openings and water levels. Statistical indicators were used to compare the models. Results showed that the new algorithms can be useful and the HEC-RAS model, with fewer estimation errors, appropriate for the study of steady state flow in irrigation canals. Results showed that pinion height in radial gates is an important factor for developing discharge algorithms.

The soil water retention curve (SWRC) is a basic characteristic of the determination of soil hydraulic properties, including unsaturated hydraulic conductivity. Measurement of this curve is essential to research, thus scientists have focused on indirect methods such as pedotransfer functions and empirical relationships to estimate SWRC easily. Since there is a close relationship between SWRC and particle-size distribution (PSD), fractal geometry was used in this study to define a relationship between the fractal dimensions of these two curves. This helps to obtain an SWRC equation based on soil particle size distribution as a readily available parameter. To achieve the above objective, 40 soil samples with seven different textures were used. Two logarithmic equations were presented for determination of the fractal dimensions of PSD and SWRC based on their clay percentages. Their correlation coefficients equaled 0.96 and 0.93, respectively. Finally, a cubic polynomial equation was obtained between the fractal dimension of SWRC (Ds) and the fractal dimension of PSD (Dp) with a goodness of fit of R2=0.94. The physical properties of another five soils collected from Pars province were used to evaluate this relationship. First, the Dp of the soils were calculated. Next, using the Ds-Dp relationship, the Ds and the SWRC equation were estimated using the Xu model. To increase the accuracy of the prediction of SWRC, a calibration model was used to adjust the predicted water content values by using two measured points on the SWRC. Comparison of the adjusted water content values with measured ones was done by statistical analysis and calculating the relative standard error (RSE) and Akaike's information criterion (AIC).  The results showed that the RSE and AIC values decreased 50% to 85% and 20% to 93%, respectively, using the calibration model.

Gaz-angubin is a sweet exudate naturally produced by an insect from the Gavan-e-Gaz-angubin plant. Adsorption and desorption isotherms for a Gaz-angubin sample were determined at 15o and 25oC over a range of relative humidity from 0 to 90% using a dynamic vapor sorption system. At different levels of relative humidity, changes in sample mass were continuously measured versus time and described using an exponential model. Gaz-angubin exhibited type III sorption behavior. The sorption capacity decreased with increasing temperature. The sorption-desorption isotherms revealed the phenomenon of hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for the desorption curve than for the adsorption curve. Water sorption/desorption isotherms were modelled using the Guggenheim-Anderson-de Boer (GAB) model. The GAB model showed a good fit to experimental data for water activities of up to about 0.75. It was observed that, for short intervals, the diffusion of water can be described by Fickian laws and Gaz-angubin showed essentially a Fickian diffusion.

Starch is a versatile and useful polymer having physicochemical properties that can be altered by chemicals or enzymatic modification and/or physical treatment. Native starches possess many disadvantages that decrease their application and industrial use, but could be modified to obtain the desired properties to meet industrial needs for a wide range of starch applications. Physically modified starches are considered to be very safe, natural materials. Power ultrasound appears to be an effective process for modification of starch. Natural wheat and potato starches were sonicated under different conditions and their physical properties were investigated. Studies on starch pasting properties have shown that starches treated with power ultrasound had lower peak viscosities and higher pasting stability than did native starch. Ultrasound treated starches exhibited an increase in pasting temperature. Sonication also induced the starch paste to become more transparent and less viscose. The same treatments were applied for potato starch and showed almost the same patterns and effects, but indicated that temperature and amplitude are more important. Most changes occurred at temperatures higher than that of gelatinization because of structural changes in the granules. Data collected at different stages were analyzed using a factorial experimental design and means were evaluated in the form of mathematical models with linear and 3D-surface charts. Power ultrasound may be applied for the preparation of a physically modified starch that has good clarity and low viscosity and also aids the production of thin boiling starch produced by chemical treatments such as acid or oxidation.

The canola drying process was investigated using three laboratory scale dryers connected to a computer which continuously recorded the drying processes of each unit. A completely randomized design (CRD) with three replications was used for the statistical analysis. The effect of temperature (40o, 50o, 60oC) and air velocity (1, 2 m/s) on the drying kinetics of a monolayer were studied. The effective moisture diffusion coefficient (Deff), activation energy and percent of free fatty acids were measured for the drying process and dried canola. A drying estimation model was determined using a linear regression model for increasing temperatures. The results indicated that changes in temperature have the greatest effect on canola drying time. Increasing the temperature from 40o to 60oC caused the drying time to decrease by 66.4%. Changes in air velocity from 1 to 2 m/s reduced drying time 29.4% on average. Deff increased from 2.05694×10-8 to 5.8061×10-8 m2 and activation energy from 27.34 to 37.49 kJ/mol with a 40o to 60oC increase in temperature. Changes of temperature and air velocity did not have adverse effects on canola free fatty acids.

Performance evaluations on irrigation networks around the world show that they perform far below expectations. In addition to physical and managerial shortcomings, methodological difficulties contribute to poor performance. Traditional methods have only resulted in marginal performance improvements. A number of researchers are working on performance assessment methods for irrigation networks. However, because numerous components affect the performance of systems, selection of the appropriate performance improvement option is a complex issue. It is important to determine the impact of improvement options and variations in each decision component quantitatively on the degree of performance improvement. In this study, a decision support system based on data envelopment analysis (DEA) and its sensitivity analysis capability was developed. This model determines performance evaluation, performance standards and improvement potentials. The impact of different options on performance improvement is determined and ranked using sensitivity analysis. The ranked improvement options provide basic support for decision makers. The model was applied to eight irrigation networks and a sample of the results is presented. For example, the performance of sample network 1 is 0.2 and its reference unit is determined. The results show that personnel and machinery indicators perform more weakly than the technical and economic indicators. It was found that the economic indicator has a greater impact on the performance of the system than the technical indicator. Reducing the system input has more impact on performance improvement than the other indicators. The application of this decision support system, with its capability of sensitivity analysis in DEA, provides necessary information for system management to select improvement options.

The nutritional value of cereal straw can be increased using urea treatments as a source of ammonia. The conventional urea treatment process for cereal straw is a laborious and time-consuming task. It is essential to facilitate or eliminate part of the procedure with the use of machinery. This study examines the mechanical urea treatment of wheat straw and compares chemical components and digestibility of the treated straw with that treated conventionally. For mechanized urea treatment, a rectangular baler fitted with a urea solution sprayer was used to treat the straw. The machine was connected to a tractor and used to prepare mechanized urea treated bales. At the same time, the conventional method was used to treat chopped straw. The samples were then compared with the mechanized treated straw. Results showed that treatment methods had no significant effect on the chemical compositions of DM, ash, ADL, DM, and CP. The effect of treatment method on other chemical compositions (NDF, ADF) and straw digestibility parameters (DMD, OMD and DOMD) was significant (P<0.05). The mean values of DMD, OMD and DOMD for untreated straw were 30.00%, 27.64%, and 25.92%. These values were 44.35%, 44.43%, and 41.46% for the conventional treatment method and 40.35%, 37.87%, and 35.51% for the mechanized method. The effective field capacity and effective material capacity of the mechanical urea treatment were 0.41 ha/h and 2.05 t/h, respectively. Results of this research also showed that mechanical urea treatments can be done under field conditions along with baling operations. This method of urea treatment can also increase the moisture content of the straw to the recommended range for urea treatment of wheat straw.