فصلنامه تحقیقات مهندسی کشاورزی
سال دوازدهم شماره 4 (زمستان 1390)

Environmental pollution by heavy metals is a growing global concern. Most heavy metals accumulate in the top soil and in the long term, increased concentrations in the soil results in increased absorption and accumulation in plants. The usual concentration of cadmium in the soil is 0.001-2.4 mg/kg of dry soil. The level of absorption and accumulation in plants depends on the type of plant, tissue make-up of the plant and physical and chemical characteristics of the soil. There is a deficit of information on the amounts of absorption and accumulation of heavy metals at different tomato growth stages. This study was conducted to analyze the impact of the level of cadmium concentration in soil on its absorption and accumulation at different stages of tomato growth using factorial experimentation in a completely randomized design with three repetitions. The variables were three Cd concentrations (control treatment with no Cd; soil with 50 mg kg-1 Cd; soil with 50 mg kg-1 Cd; soil with 50 mg kg-1 Cd). The soil samples were collected from 400 ha of farmland at the Seed and Plant Improvement Institute in Karaj, Iran. They were sifted twice using 2 mm mesh and the treatments were prepared by adding cadmium nitrate to the soil to make homogeneous mixtures. The experiments were carried out in plastic cylinders 120 cm in length and 85 cm in diameter. The depth of the solution soil was sampled hourly and tomato organs were sampled at different growth stages to record the cadmium absorption rate. SPSS software was used to perform an analysis of variance of the data and the Duncan multiple range test was used to perform a comparison of means (P ≤ 0.05 and P≤ 0.01). Results showed that cumulative cadmium concentration differs in the tissues of the leaf, root, leg, fruit and peel in decreasing order. A negligible amount of the total cadmium added to the soil was absorbed by the plant. Total cadmium absorbed in the cellular colonies of the tomato plant in the control treatment, soil with 50 ppm added Cd, and soil with 100 ppm added Cd were 0.0384, 0.564 and 0.678 g, respectively. The results indicate a direct relationship between Cd accumulation and Cd concentration in the root region. A comparison of the outcomes indicated that increasing the cadmium concentration resulted in a reduction of tomato growth and, especially, the production rate. A 20-35% decrease in production rate was seen in 50-00 ppm cadmium exposure compared to the control. These results show that strong decreases in cadmium concentrations in the solution soil did not decrease the absorption rate of cadmium at various growth stages of the tomato.

The greatest limitations to agricultural development and production in Iran are scarcity of water resources, ineffective irrigation scheduling and wasteful water usage. Avenues discussed for optimum water use include improving water productivity by improving irrigation scheduling, farm water management and water profitability. The present study evaluated current water use and ways to improve winter wheat productivity by varying field scale water usage in the Abshar irrigation network in Esfahan province, Iran. Optimal irrigation depth and scheduling, and yield function for winter wheat using current water management tactics were determined. The availability of water, rotational water rights laws and field data were combined using the AquaCrop simulation model for field scale crop growth. Crop yield and winter wheat productivity were then simulated and compared to field results. Field research indicated that 800 mm of water is applied annually for winter wheat and crop yield averages 5000 kg per hectare. Improvements in water management and productivity based on different irrigation schedules (changes in depth and time) and water quantity schemes and the effect on water balance and crop yield were investigated. The baseline scheme used current conditions as a reference for other schemes. The results showed that eliminating the second, third and seventh irrigations from the schedule decreased the quantity of water applied by 38%r and yield by 4%, which produced a 45% increase in water productivity over the baseline scheme. However, improving agronomic management and decreasing the first irrigation depth by 50% (from 200 to 100 mm) also produced a slight variation in crop yield. Increasing the water applied to the optimal depth increased water productivity, but increasing the water applied to greater than optimal levels had no significant effect on yield and decreased water productivity. The results showed that proper irrigation scheduling using the AquaCrop model in combination with improved agronomic management decreased the quantity of water applied during irrigation 38%, increased crop yield by 16% and water productivity by 79%.

In arid, semiarid, and Mediterranean climates, particularly in West Asia and North Africa, farmers face limited water resources and must develop irrigation management methods to increase crop production while reducing water use. This study examined methods to reduce irrigation water loss and increase maize water productivity at Safiabad Agricultural Research Center in Dezful, Iran in 2007 and 2008. The experiment was a randomized complete block design with a strip-split plot arrangement of treatments in three replications. Planting and irrigation management methods used were: (T1) planting on 75 cm wide ridges and full irrigation (current method and the control treatment); (T2) planting on 75 cm wide ridges and variable alternate furrow irrigation; (T3) double row planting on 75 cm wide ridges and full irrigation; (T4) single row planting in 75 cm apart furrows and converting furrows to ridges at the 2-4 leaf stage; (T5) single row planting in 75 cm apart furrows keeping fixed furrows and ridges until the end of the growing period and; (T6) planting on 75 cm wide ridges using full drip irrigation. The three maize hybrids studied were Ossk-602, Bc-666 and Sc-704. Grain yield, biomass, irrigation water consumption, crop water productivity, and irrigation water productivity were recorded for evaluation of the planting and irrigation management methods. The results indicated that there were no significant differences in yield among the maize hybrids. In the control treatment, water loss occurred mainly as runoff. Treatment T5 resulted in a 31% decrease in irrigation water and higher grain yield over the control treatment. Mean crop water productivity was 1.45 kg/m3. This study showed that effective surface irrigation management methods and furrow planting increases irrigation water productivity (IWP) 45% over the control treatment. In addition, drip irrigation increased IWP three fold, approaching CWP for all the studied maize hybrids.

Barbari is a common Iranian flat bread that has a short shelf life. The effect of low density polyethylene/clay nanocomposite film was investigated for the package and shelf life of the flat bread when stored at different temperatures and relative humilities with different percentages of nanoparticles. Nanoclay concentrations of 2% and 6% were used for the nanocomposite and pure polyethylene was used as a control. Bread packages were stored at 10°, 25° and 40°C and 30% and 75% relative humidity for four days and then the quality of the bread and changes in the concentration of oxygen inside the packages were analyzed. The results showed that the permeability of nanocomposite films decreased as the percentage of nanoparticles increased. Increasing the temperature increased the permeability, reduced the quality of bread and the rate of oxygen penetration into the packages and removed moisture from the packages, causing hardening of the bread texture.

design equipment and facilities to dry, preserve and process pomegranates, it is To necessary to know their specific heat and thermal conductivity. The objectives of this study were to determine the specific heat and thermal conductivity of pomegranates and -The effects of moisture content (15 mathematical estimation models for them. develop 75% w.b.) and temperature (5-20°C) on the thermal properties of pomegranates (Alak variety) were studied. Specific heat was measured using the mixtures method. The thermal conductivity was measured using a line heat source probe for pomegranate exocarps and The results showed that an mesocarps and the bare-wire transient method for the seeds. increase in moisture content and temperature produced a linear increase in the specific 0.931 to 3.066 kJ/kg°C for mesocarps, and heat from 1.127 to 2.789 kJ/kg°C for seeds, 1.516 to 3.411 kJ/kg°C for exocarps. Thermal conductivity increased from 0.1524 to 0.4218 W/m°C for seeds, 0.148 to 0.451 W/m°C for mesocarps and 0.131 to 0.4204 W/m°C for exocarps as moisture content and temperature increased. However, the effect of moisture content was greater than the effect of temperature on specific heat and thermal conductivity. The empirical equations for these thermal properties were subsequently expressed as a function of moisture content and temperature.

Varieties of St. John’s wort (Hypericum perforatum L.) native to Iran possess the largestpercentage of hypercin in their leaves and flowers. Isotherm curves show the relationshipbetween the relative humidity and moisture content of the plant at a constant temperature. It is essential to understand the isotherms curves for successful storage and drying of the plant. This study used adsorption and desorption to determine the moisture equilibrium of St. John’s wort flowers at 40°, 50°, 60° and 70°C. Moisture content was determined to be 0.11-0.84 using the gravimetric static method. Five mathematical models (modified Henderson, modified Oswin, modified Halsey, modified Chung-Pfost and GAB equations) were used to compare the experimental data. The modified Halsey and Chung- Pfost models were found to be the best models for describing desorption and adsorption isotherms curves.

Iran is a major world producer of walnuts and a hub of walnut exports to other countries. Walnut harvesting and cracking is still done manually, which increases price and waste. Design and development of an effective harvester and walnut crusher is required to reduce costs and wastage. This study determined the mechanical properties of a test apparatus employing two flat jaws using different treatments and walnut varieties. Testing was done on three varieties of walnuts at two speed loads (30 and 50 mm/min) in three directions (one vertical and two horizontal). A universal testing machine was used to determine the rupture force, rupture energy and toughness for Hartley, Z63 and Z30 walnut varieties. Results showed that the effect of variety and loading direction was significant at the 0.01 level and the effect of load speed was significant at the 0.05 level for rupture energy and toughness. The triple effect was not significant. Result shows that increasing loading speed increased rupture energy and rupture force and decreased toughness.

In this study, the performance of a fabricated fluffer was evaluated and compared with common field curing methods for alfalfa. The drying rate, baling loss and alfalfa nutrient value (dry matter and crude protein) were the criteria for evaluation. The alfalfa was cut using a mower-conditioner. A randomized complete block experimental design was used with three treatments (fluffing swathed alfalfa with fluffer, raking swathed alfalfa, swathed alfalfa without treatment) and four replications. Moisture content at mowing was 70% (w.b.) and at baling was 20% (w.b.). Moisture content was measured using standard methods at three hour intervals. Data values were fitted to the exponential model and the drying constant was determined under different conditions. Results indicated that the raked alfalfa and alfalfa processed by a fluffer had faster drying rates than the untreated alfalfa and or the alfalfa cured by conventional methods. The drying constant on the first day after raking for alfalfa processed by rake was 0.068, by fluffer was 0.068, and by mower-conditioner 0.043. Corresponding values for the second day were 0.087, 0.064, and 0.06. The analysis of variance showed no significant differences among the treatments for baling loss and alfalfa nutrient value.