نشریه مهندسی زراعی
سال سی و ششم شماره 1 (تابستان 1392)

Salinity limited plant growth and will decrease the yield with decrease in solution osmotic pressure, nutrient imbalance and toxicity of some specific elements. Application of amendment materials such as gypsum and cattle manure can adjust the undesirable effects and increase the nutrient elements in leaf and grain. In this regard a pot experiment was conducted during 2009 growing season based on split factorial with four replications in complete randomize design. In this experiment the main factor was inclusive different level of salinity in irrigation water {0, 3, 6, 9 and 12 dS/m as NaCl and CaCl2 (1:1 w/w)} and subsidiary factors were inclusive gypsum (0, 15 and 30 ton/ha) and the cattle manure (0 and 30 ton/ha). The results showed that increasing the salinity content of irrigation water causes reduce the amount of phosphorus and increase nitrogen and potassium in wheat leaves. Also, with increasing in salinity of irrigation water the amounts of phosphorus and potassium in grain decreased and the amount of nitrogen in grain increased. Application of gypsum increased the amounts of the nitrogen, phosphorus and potassium 6.31, 10.89 and 14.82 percent in leaves and the amounts of the nitrogen, phosphorus and potassium 10.32, 10.84 and 3.45 percent in grain, respectively. Using manure at different salinity treatments was significant affecting on the amounts of nitrogen and phosphorus in leaves and phosphorus and potassium in grain. The highest amounts of nitrogen and phosphorus in leaves and grain were obtained using 15 and 30 tons of gypsum per ha while the highest amount of potassium in leaves and grain were obtained using 30 tons of gypsum per ha.

Wastewaters from different industries contain great amounts of heavy metals which can contaminate the ground water after entering the soil. Few studies have been conducted on the application of clay minerals such as sepiolite in preventing the leaching of these elements. This study was conducted to evaluate sepiolite as a strong and inexpensive adsorbent in preventing the leaching of lead and zinc from sandy soil columns under laboratory conditions. Therefore, 400 ml of solutions containing lead and zinc with a concentration of 75 mg/l, were passed through pre-saturated soil columns with different amounts of sepiolite (2, 4, 6 and 8 weight percent) in two sizes, < 2 and 20- 50 microns, under a flow rate of 1.2 liter h-1. The concentration of lead and zinc in the successive 20 ml leachate was then measured using atomic absorption spectrophotometer. Results showed that application of sepiolite in soil columns decreased leached amount of Pb and Zn as compared to control treatments. Also, with increasing sepiolite application rate, and decreasing its particle size, leaching of zinc and lead from the soils was reduced. However, the amount of lead leached was less than that of zinc. It seems that sepiolite mineral could be utilized as suitable materials to reduce the leaching of lead and zinc from soil to ground waters.

Drying grape fruit as a strategic product in Iran faces numerous challenges including color change, spoilage, and hygienic issues and long drying time. To this aim, the present research was conducted to kinetically study the thin-layer hot air drying of grape fruit together with mathematical modeling to cover the drying process. The results give a promising opportunity for an appropriate design of a dryer. Experimental setups included four levels of air temperature, 40, 50, 60 and 70 oC and air velocity of 1.2 ms-1. Ten semi-empirical and empirical models were subsequently fitted to the experimental data and statistical criteria, coefficient of determination (R2), Chi square (χ2) and Root Mean Square of Error (RMSE) were investigated. Results showed that air temperature of drying has a meaningful effect on the drying rate in a way that increasing the temperature from 50oC to 60oC led to a 59% reduction in the drying time. It was observed that the whole drying process was located in the falling drying phase. Modeling evaluation of data showed that Midili model fitted best (R2=0.9978, χ2=0.0001679 and RMSE=0.010234) to the experimental results. Additionally, the influence of air temperature on the constants and coefficients of the studied models was extensively assessed.

In mathematical modeling and design of hydraulic systems, it is very important to determine the flow rate through control valves on the basis of discharge coefficient and also the orifice cross section created in the valves. Although the discharge coefficient depends on the oil flow type through the orifice, it is usually assumed as constant in hydraulic valves. Thus, in this paper, the discharge coefficient of orifice created by spool and three conventional poppet types in hydraulic valves were examined experimentally. Then, based on the experimental data, the curve fitting of discharge coefficient versus square root of Reynolds number was extracted for four types of orifice created by the moving members including spool, cone, spherical and cylindrical. Curve assessment showed that the discharge coefficient in turbulent flow for all four types of moving members was constant, but in the laminar flow conditions, the discharge coefficient linearly varied by square root of Reynolds number for them. The discharge coefficient in turbulent flow conditions for the orifice created by spool was lower than the other moving members. While, the slope of the linear part of the discharge coefficient curve for this orifice was more than others.

It seems necessary to study different beds on which pot plants can be grown in apartments. Organic wastes and different types of mineral substances can be used to prepare domestic beds as cheaper, more available, and higher-quality alternatives for foreign and imported beds. For this purpose, the present study explores effects of different organic and inorganic beds on the pot plant Dracaena marginata Ait and its ornamental leaves. The beds used for growing the plant in this study included different ratios of peat, urban waste compost, and vermicompost in combination with perlite and zeolite. Findings indicated that the beds composed of peat (50%) + perlite (50%), waste compost (50%) + perlite (50%), and vermicompost (50%) + perlite (25%) + zeolite (25%) are the most effective ones on plant altitude, number of leaves, and stem diameter while the poorest results were obtained for a combination of waste compost (50%) + perlite (25%) + zeolite (25%). The highest level of absorption for nitrogen, phosphor, and potassium was observed in the treatment peat (50%) + perlite (50%) while the lowest absorption was found in the plants treated with waste compost (50%) + perlite (25%) + zeolite (25%). Given these results, and due to the lower cost and availability of urban waste composts and vermicompost compared to peat, the combination of vermicompost (50%) + perlite (25%) + zeolite (25%) as well as waste compost (50%) + perlite (50%) can be used to replace the imported products (i.e. peat (50%) + perlite (50%)) in growing Dracaena marginata Ait and other ornamental or pot plants in our country.

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. One of the best options for increasing the irrigation efficiency and better application of precipitation in arid and semi-arid areas are application of superabsorbent polymers to soil. Different sizes of particles of a superabsorbent polymer were compared on the soil water retention capacity. The study adopted a factorial experimental design based on a completely randomized design in loamy sand and clay loam soil with three replications. There were 7 treatments of water absorbent material including control (without the water absorbent material) and superabsorbent Taravat A200 in 6 sizes (0.21-0.25, 0.25-0.5, 0.5-1, 1-2, 2-3.4 and 3.4-4.75 millimeter, each at 2g per kg soil). Then soil water content was measured for each treatment at suctions 0, 0.1, 0.3, 0.5, 1, 3, 5 and 15 bar and the soil moisture curves were plotted separately. The results showed that there was a significant difference among treatments and two soil textures in various suctions and the interaction of these factors at the level of %1. Also, it was observed that the superabsorbent polymer 1-2 mm compared with other treatments resulted in increase the soil water holding capacity, significantly especially in the light soil texture.

In order to study the effect of potassium and manure fertilizer on yield and concentration of macro elements in leaf and grain of wheat (N-81-18 cultivar) under water stress, a pot experiment was conducted in split plot based on randomized complete design with four replications in 2009-2010 crop years. The main factor was inclusive irrigation after depletion of 75, 50 and 25 percent of available water, and the subsidiary factor was inclusive potassium sulfate in three levels (0, 300 and 600 kg/ha) as well as manure fertilizer in three levels (0, 20 and 40 ton/ha). Results indicated that irrigation treatment had a significant effect on grain yield and elements of nitrogen, phosphorous and potassium in leaf and grain at p<0.01 and the greatest amount of elements except for the phosphorous of grain was observed in irrigation treatment after depletion of 75% available water. Phosphorous in leaf and grain increased with the consumption of manure fertilizer and the most amount of phosphorous of grain was obtained in irrigation treatment after depletion of 50% available water and application of 40 ton ha-1 manure fertilizer and the greatest amount of phosphorous of leaf was observed with consumption of 20 and 40 tons ha-1of manure fertilizer. The maximum amount of grain yield was achieved in irrigation treatment after depletion of 25% available water and usage of 40 ton ha-1manure fertilizer. Grain potassium was increased with the consumption of 300 and 600 kg/ha-1 potassium sulfate.

In order to evaluate the effects of type of herbicide and tillage implements on weeds control, seed yield and some agronomic traits ofbean (Phaseolous vulgaris L.), two field experiments were carried out as factorial arrangement in complete block design with three replications during 2007 and 2008 growing seasons at Khomain Research Station (49º 57´ N; 33º 39´ E, and 1930 m above sea level) in Agricultural and Natural Resources Research Center of Markazi Province. Two types of herbicides including Trifluralin and Ethalfluralin and three tillage implements such as rotary plow, disc and cultivator, comprised the experimental factors. Results of combined analysis showed that the effect of tillage implements and type of herbicide for seed yield and weed population were significant at 5% probability. In this research, application of Ethalfluralin and rotary plow had superiority for enhancement of seed yield and decrement of weeds population. In addition, tillage implements such as rotary plow and disc showed superiority for incorporation of soil and herbicide, respectively.