فصلنامه تحقیقات مهندسی کشاورزی
سال دهم شماره 1 (بهار 1388)

Ten varieties of Iranian soybeans are cultivated in different areas of the country; Persia or Sahar (SR), Hill (HL), Williams (WZ), Gorgan 3 (GN), Clarke (KL), Hawkey (HK), Zaan (ZN), Harcor (HR), Dare (DR) and Simes (SS), grown in tropical regions. Samples of these 10 varieties were obtained from the Institute of Plant and Seed Research. After sample preparation, their oils were extracted and analyzed for iodine content, saponification, refractive index, specific gravity, peroxide, free fatty acids, color, fatty acids composition, Fe and Cu. Statistical results showed that there were significant differences (P < 0.05)between them. Fatty acid profiles showed that the ZN and GN varieties had the lowest and highest linoleic and linolenic fatty acids, respectively. The ZN variety had the highest oleic acid content. It was concluded that the ZN variety is best in chemical composition for oil production, with HR and WZ ranked second and third.

Ethylene affects the ripening of fruits and is naturally produced in most plant tissues. Its production and accumulation during storage can cause serious damage to stored fruits such as black sweet cherries (cv: Takdaneh Mashhad). It affects shelf-life and can cause a marked increase in respiration rates, increasing ripening and senescence. In some commodities, accelerated aging and the initiation of ripening can occur following exposure to ethylene concentrations as low as 0.1 ml/l. As senescence begins, spoilage due to indigenous bacteria can be augmented. The removal of ethylene can delay over-ripening, prevent spoilage and increase the shelf-life of harvested fruit. This study investigated the effect of removing ethylene from storage using nano particles. Potassium permanganate and two types of zeolite-based nano-molecular filters were used. Small 5g sachets were placed directly onto the fruit in each container o r an ETH 1500 machine (BIOCONSERVACION) was used. The experimental design was factorial in randomized complete block design with four replications. The two factors were the presence or absence of the sachets or the machine. Commercial traits affecting market shelf-life of the fruit are: total soluble solids concentration (TSS); pH; titrable acidity (TA); texture (firmness); color (chroma, hue and lightness); fruit stem browning; and the reduction in fresh weight. These were measured at the beginning of the experiment (day 0) and after 10, 20 and 30 days of storage. As expected, there were significant differences in the traits at different sampling times for all treatments. However, fruits with an ethylene absorbent (especially the machine) were healthier, better looking and showed significantly lower reduction in fresh weight. After 30 days of storage,the highest firmness value (6.04 N), lowest weight reduction (4.48%), lowest TSS (19.63%), lowest stem browning (25-50%), and lowest reduction in TA (0.44) were obtained from fruits with an ETH machine or sachets. The lowest firmness value (2.61 N), highest weight reduction (15/20%), highest TSS (24.38%), highest stem browning (75%), and highest reduction in TA (0.17) was obtained from fruits stored without an ETH machine or sachets. It was concluded that the use of potassium permanganate and zeolite-based nano-molecular filters increase the shelf life and market value of black cherries and are advisable for fruit storage facilities.

Ultrasonic testing (UT), a nondestructive testing (NDT) method, is under development for quality determination of agricultural products, although it has long been used in the food industry. Determination and measurement of product quality are important in modern agricultural research. Noninvasive/nondestructive quality determination is a novel aspect of the postharvest process in which parameters measured by NDT methods are correlated with product quality. Reviews show that the “through-transmission method” is better than other UT methods for examination of agricultural products. The main parameters of the through-transmission method are wave velocity and attenuation.In this research, a UT system was designed and developed to analyze a signal passing through a product. The system consisted of a set of fabricated pulser/receiver units with ultrasonic transducers, control software and a data acquisition system. The system semi-automatically determined the two important ultrasonic parameters of wave velocity and attenuation coefficient by signal processing. The effect of couplant type, contact force, enveloping, delay line, and sample thickness were investigated using the signal. Several types of fruits and vegetables having differing tissue types (apple, potato, nectarine, banana, carrot, cucumber and quince) were selected for testing. The thicknesses of thesamples were 5cm to 12cm. Results demonstrated that using couplant, enveloping signal, low contact force (5N) and suitable sample thickness, the ultrasonic measurement system could measure ultrasonic parameters effectively at a suitable response speed. The ultrasonic wave was transmitted through most of these products using a pulse signal with 40kHz excited frequency at low power. The precision of the time-of-flight measurement increased with enveloping of the transmitted signal.

The hydrodynamic behavior of approaching flow and the amount of sediment entry into right-angled lateral intakes in diversion dams were investigated using a laboratory channel by experimental measurement and observation. The velocity field upstream of the intake in the main channel and before it at the sluice gate was measured at different elevations of flow at different discharge rates of the river, intake and sluice gate. Velocity profiles were also measured from upstream to downstream for the intake and the amount of sediment entry into it. Analysis of the velocity data showed that discharge at the sluice gate strongly affected velocity profiles and the mechanism of sediment entry. All velocity profiles where the sluice was closed had an inflection point, where the flow direction changed, leading to a return velocity near the bed. The elevation of this point was a function of the intake discharge and approximately equal to the height of the entrance sill. Observation showed that sediment entered the intake in whirlpool vortices. The strength and frequency of the vortices depended on the intake and sluice gate discharges. Analysis of sedimentary data showed that the amount of sediment entering the intake increases with an increase in intake discharge. In addition, for any given intake discharge rate, an increase in the sluice gate discharge caused an increase in sediment entry into the intake.

No tillage systems can reduce operating costs, enhance soil organic matter, ameliorate soil structure and prevent environmental damage caused by stubble burning. However, the lack of an appropriate direct drill for the hardened soil of arid areas reduces adequate soil-seed contact and, thus, the system has shown contradictory results in past tests. Developing a direct drill to place the seed and fertilizer at different depths, then cover the seed with a layer of fine soil without incorporating stubble into it is the first step inapplying the no tillage system in pilot experiments. In this study, an active notched coulter (PTO driven) acting as a circular saw that cuts a groove on the soil surface was installed on a grain drill and was evaluated in hardened soil covered by wheat residue mulch. The active coulter operated at different rotary speeds in the forward and backward directions (with or against the rotation of the tractor wheels). Preliminary experiments showed that the backward rotation of the coulter cut a deeper groove at a given speed and left a relatively clean, empty groove than did the forward rotation, which nearly refilled the groove. A cutting unit, therefore, was designed based on the backward rotation of an active coulter at 580- 700 rpm. The coulter cut a 15 mm wide groove to an average depth of 55 mm as it moved forward, throwing the soil forward and upward. This necessitated placement of a mudguard over the coulter to prevent or redirect the upward flow of soil toward the end of the cutting unit. The soil particles thrown off of the end of the mudguard then refill about 20% of groove depth, the amount of soil required to create a layer of soil between the fertilizer and seed. The fertilizer tube was installed immediately behind the coulter (50 mm above the soil surface) before the soil flow partly refilled the groove. The seed pipe was then installed far enough behind the cutting unit along the groove to allow the seeds to be placed on the partially-filled groove. Finally, a fork coverer filled the groove with fine particles of cut soil spread alongside the groove. Evaluation of the procedure showed that the direct drill equipped with such a cutting unit was able to place the fertilizer granules about 20 mm beneath the seeds in a hardened dry soil covered with stubble while cutting less than 10% of the soil surface.

This study examined suitable mechanized methods to seed rice in dry-bed conditions using dried seeds and determined the most suitable varieties for each method. The experimental design was strip-plots in a randomized complete block design with two factors (seeding methods and rice varieties) and three replications. The testing took place during 2003-2004 at the Shavour Agricultural Research Station in Khuzestan province. The rice varieties were Anboury, Champa and Danial (horizontal factors) and theseeding methods were use of grain drill (Barzagar Hamadan), row planter (hill drop planter) and centrifugal broadcaster (vertical factors). The rice varieties were evaluated based on total yield, yield components and other agronomic characteristics. Seeding machines were evaluated and compared based on field capacity, fuel consumption, inter-row and intra-row seed spacing uniformity and seed germination. The analysis of variance for the two years showed that the grain yield was significantly affected by year, variety and their interaction. The average yield of the second year was significantly greater than that of the first year. A maximum yield of 7246 kg/h and minimum yield of 5667 kg/h were recorded for Danial (LD183) and Champa, respectively. There was no significant difference between the average yields of the different seeding methods in both years. Seeding methods also had no significant effect on the agronomic characteristics of the rice varieties except for the number of panicles per m2. In this case, the grain drill with329 and row planter with 289 panicles per m2 had the highest and lowest values, respectively. The evaluation of the seeding machines showed that there was a significant difference between the machines for all operational parameters. The centrifugal broadcaster had greater field capacity, low fuel consumption and better seed germination. In case of inter-row and intra-row seed spacing uniformity, the row planter had 68.8% inter-row uniformity and 89.7% intra-row uniformity, giving it the best seeding uniformity of the tested machines. Results indicate that the use of a row planter for dry seeding of rice is recommended because it used a less seed (20-25 kg/h) and had better seeding uniformity. However, considering farm conditions and available facilities, the centrifugal broadcaster and grain drill can be used for dry rice and direct seeding, respectively.

Soil hydraulic properties such as saturated and unsaturated hydraulic conductivity play an important role in environmental research. Since direct measurement of these soil hydraulic properties is time-consuming and costly, indirect methods such as pedotransfer functions and artificial neural networks (ANN) were developed based on readily available parameters. In this study, the use of ANN to predict saturated hydraulic conductivity using a measured soil moisture curve and bulk density was investigated. Measured bulk density and soil moisture curves were used to estimate saturated hydraulic conductivity from calculated fractal dimensions, air entry values, bulk density and effective porosity using ANN. In the training and testing steps of ANN, 114 and 28 measured soil samples were used, respectively. R2 and MSE were 0.76 and 0.0028, respectively, for the ANN method with four inputs. A comparison of ANN with Rawls et al. (1993, 1998) models showed that the neural network more accurately predicts saturated hydraulic conductivity.