Journal of Agricultural Science and Technology
Volume:12 Issue: 1, Jan 2010

Bionomics of Aphis gossypii Glover and its predators Coccinella septempunctata L. and Hippodamia variegata Goeze were studied in Varamin (Tehran Province) during 11th May to 5th October 2006 on eggplant crop, with the interaction (density dependence) between the aphid and either of the predators determined. The reliable sample size (number of leaves) with a maximum variation of 6.73% was about 56. The index of dispersion, regression models (Taylor and Iwao), Morisita’s index as well as Lloyd’s mean crowding to mean were employed to estimate the spatial distribution pattern of the insects. The results indicated that the highest population densities of A. gossypii, C. septempunctata and H. variegata occurred in 8th June (11.62 per leaf), 17th August (0.36 per leaf) and 3rd August (2.11 per leaf), respectively. The index of dispersion, regression models (Taylor and Iwao), Morisita’s index and Lloyd’s mean crowding to mean showed aggregated distribution for all species. The linear regression model between prey and predators’ population densities showed a density independent predation by C. septempunctata and H. variegata on A. gossypii. This study indicated that spatial distribution parameters of the cotton aphid and its natural enemies can be employed to outline a sampling program and to estimate the population densities of these insects for use in integrated pest management programs.

This study was carried out to obtain quantitative relationships between Zn in equilibrium solution and that retained by 20 calcareous soils. Soils were brought into equilibrium with varying solution concentrations of Zn, and the amounts removed from solution were used to check the fit to six adsorption isotherms, namely, Freundlich, Langmuir, Temkin, Gunary, two surface Langmuir and Adjusted Freundlich. Zinc sorption and desorption data showed hysteresis which indicates adsorption and desorption mechanisms not being the same. Fits of adsorption equations showed that Freundlich equation did not describe Zn sorption in most of the soils at low equilibrium concentrations, but after removal of the three first concentration points this equation showed a best fit to the data. The single surface Langmuir equation did not describe Zn sorption data, but a two surface Langmuir equation showed statistically significant fits to the data for some of the selected soils. Temkin equation described data only at low equilibrium concentrations.

The European Corn Borer (ECB) is one of the most important insect pests of corn and some other crops such as rice in Iran. This pest is one of the most important hosts of the entomopathogenic fungus Beauveria bassiana, a well known fungal entomopathogen with high host range and considerable potential in insect pest control. In an isolate selection program of fungal isolates against ECB, ten isolates consisting of eight isolates from Iran and two from other countries were assayed using the dipping method on third instar larvae of ECB. Inoculum concentrations were 104, 105, 106, 107, and 108 conidia ml-1. For each concentration, 30 larvae were dipped into the conidial suspension for 30 secends. Control larvae were treated with distilled water containing 0.03 percent Tween-80 as surfactant. Each experiment was repeated three times. Results showed that BEH isolate which was isolated from the soil of insects living in the field, caused the highest mortality in larvae in comparison with other isolates with a mean of 57.67 percent mortality using 108 conidia ml-1. Other isolates, such as DEBI007 and EVIN I, were scored in the lower position with producing 53.43 and 42.67 percent mortality, respectively. EVIN II, DEBI002, and DEBI008 caused the lowest mortality in assayed larvae. A decrease in larval feeding was detectable a few days before death. Possible causes for the low mortality in isolates are discussed.

Vibration generated by vehicles during road transport has an important effect on the agricultural products damage process, particularly vegetable and fruit. Modulus of elasticity is one of the most important mechanical properties of fruits and its variation can be described as one of the damage criteria during transportation. This research was conducted to evaluate the effects of vibration parameters (frequency, acceleration and duration) and fruit position in the bin, on watermelon damage. At first, vibration frequency and acceleration were measured on the different points of a truck-bed in order to obtain the range of vibration frequency and acceleration distribution during transportation. Second, a laboratory vibrator was used to obtain some factors influencing damage during watermelons transportation. The damage was described as a difference in the modulus of elasticity of the watermelon (flesh and hull) before and after the test. According to the results measured on the truck-bed, the vibration frequency mean values were 7.50 Hz and 13.0 Hz for 5-10 Hz and 10-15 Hz frequency intervals, respectively. Furthermore, vibration acceleration mean values were 0.30 g and 0.70 g for 0.25-0.50 g and 0.50-0.75 g intervals, respectively. Vibration frequency and acceleration mean values were used for vibration simulation. Vibration durations were 30 and 60 minutes and damage was measured for watermelons at the top, middle and bottom positions in the bin. Laboratory studies indicated that, vibration frequency, vibration acceleration, vibration duration, and fruit position, which were taken into consideration as controlled variable parameters, significantly affected the damage (P< 0.01). Damage to the watermelon flesh was higher than watermelon hull. Vibration with a frequency of 7.5 Hz, acceleration of 0.70 g, and duration of 60 minutes caused higher damage levels. Fruits located at the top of the bin showed more damage than those in middle and bottom positions (P< 0.05)

Use of essential oils as pesticides or fungicides is safer than chemicals, but it requires plenty of the plant to be effective. Hence, finding the effective compounds of essential oils and their synthesis decreases the problem of preparing the natural compound. The antibacterial effect of Satureja hortensis L., Thymus vulgaris L. essential oils, and their major constituents were determined using the disc diffusion method. These essential oils prevented Erwinia amylovora growth (that causes fire blight disease). The essential oils were fractionated using preparative column chromatography (Silica column) and all fractions were tested for their antibacterial activities on this bacterium. Effective fractions were analyzed by GC-MS. Results showed that carvacrol is the effective compound in Satureja hortensis essential oil and has strong antibacterial effect. The effective compounds in Thymus vulgaris essential oil are thymol and carvacrol. Thymol and carvacrol showed a strong antibacterial effect against E. amylovora in the disc diffusion method. These compounds prevented the growth of E. amylovora in sucrose and nutrient agar media.

The forecasting of hydrological variables, such as streamflow, plays an important role in water resource planning and management. Recently, the development of stochastic models is regarded as a major step for this purpose. Streamflow forecasting using the ARIMA model can be conducted when unknown parameters are estimated correctly because parameter estimation is one of the crucial steps in modeling process. The main objective of this research is to explore the performance of parameter estimation methods in the ARIMA model. In this study, four parameter estimation methods have been used: (i) autocorrelation function based on model parameters; (ii) conditional likelihood; (iii) unconditional likelihood; and (iv) genetic algorithm. Streamflow data of Ouromieh River basin situated in Northwest Iran has been selected as a case study for this research. The results of these four parameter estimation methods have been compared using RMSE, RME, SE, MAE and minimizing the sum squares of error. This research indicates that the genetic algorithm and unconditional likelihood methods are, respectively, more appropriate in comparison with other methods but, due to the complexity of the model, genetic algorithm has high convergence to a global optimum.

Cohesive sediment transport remains a complicated subject that hydraulic engineers are frequently faced with in water-related engineering problems. This is primarily affected by the macroscopic aspects of water-sediment system characteristics. In this paper a 1-D mathematical model was developed to be employed in predicting the cohesive sediment transport under simultaneous conditions of erosion and deposition. This model is based on the convection-diffusion equation with proper source and sink terms and dispersion coefficient. The equation developed in the model has been solved by applying the finite volume approach. The model has been calibrated by employing the optimization technique using laboratory experimental data. For optimization, the transformed Powel''s method has been employed. The data were collected in a flume of 10 m length, 0.30 m width and 0.45 m height. The applied discharges and concentrations were between 3 to 5lit/sec and 7 to 15 lit sec-1, respectively. The performance of this model has been assessed using two data sets: a set obtained in this study, and another provided by other researchers. The model shows good agreement with both data sets. The results obtained suggest that the deposition and erosion are functions of flow concentration, flow depth and shear stress exerted on bed.

Grasspea (Lathyrus sativus) is a protein-rich forage legume that contains a neurotoxin (beta-ODAP) that causes severe malformation of the body’s extremities when eaten in large quantities. Various low-toxin lines of grasspea have been developed to reduce the toxin’s concentration in the grain, i.e. to below the 0.2% critical value, but there are indications that zinc (Zn) can also reduce the toxin. Thus, we assessed the effect of added Zn, using a low Zn (0.4 mg kg-1 DTPA Zn) soil, on B-ODAP in several grasspea lines in two greenhouse experiments and three field trials on the same soil type from northern Syria. In the greenhouse, Zn consistently reduced the toxin in three lines in the first experiment but not in the second one with some high-toxin lines, while added P had no effect on Zn. In the field trial for three seasons (260, 429, and 405 mm rainfall) with nine grasspea lines, applied Zn (0, 5, 10, 20 kg ha-1) tended to reduce B-ODAP in the grain by 10 to 40%. There was no relationship between Zn concentrations in the grasspea grain or straw and the reduction in B-ODAP. The mechanism by which the B-ODAP concentration may be reduced by added Zn is not known. The effect of Zn is only a partial solution at best to the problem of neurolathyrism; breeding grasspea lines that have no harmful levels of the toxin is required.

Native phosphate solubilizing bacteria (PSB) were isolated from four areas (Ankober, Keyt, Mehalmeda and Molale) of Ethiopia to study their effect on releases of soluble phosphorus from insoluble P sources. The highest bacterial number was found at Keyt (2.6´103 g-1soil) and the least at Molale (15 g-1soil). Five efficient PSB were selected for further study based on their ability in forming a higher clear zone diameter than the other isolates. These isolates were identified based on phenotypic characters as Pseudomonas sp. Anb-105, Meh-008, Meh-101, Meh-303 and Meh-305. The phosphate solubilizing efficiency of these five isolates along with Jim-41 isolate from the National Soil Research Centre were studied using different P sources [Tricalcium Phosphate (TCP), Egyptian Rock Phosphate (ERP), Bikilal Rock Phosphate (BRP) and Old Bone meal (OB)] in an incubation study. The results revealed that all the PSB isolates significantly (P£ 0.01) solubilized a higher amount of TCP, ERP and OB over the uninoculated control. The highest amount of solubilization was achieved for TCP with Meh-305 (39 mg per 50 ml) followed by ERP with Meh-101 (31 mg per 50ml) at pH 3.82 and 3, respectively. Although Meh-008 and Jim-41 isolates solubilized significant amount of BRP during the 20 days of incubation, the soluble P obtained was very small as compared to other P source tested.

Soil data can be very significantly informative in archeological and anthropological studies. Bam Citadel (BC), as the largest and oldest earthen (non baked brick) monument of the world has been restored for several times, but no data have yet been available surrounding the materials employed in the restoration work. Bam Citadel (BC) was almost totally destroyed by the severe earthquake of December 26th, 2003. A detailed knowledge concerning the old sun-dried cobs and the architecture of the exposed parts could be essential for a better ongoing as well as future restoration. Some old parts of the citadel have been exposed following the devastating earthquake. A micromorphological, physico-chemical, mineralogical and sulfur isotope geochemistry study was carried out to compare the characteristics of the soil samples obtained from the previously restored vs. those of the exposed old parts of the BC. The results indicated that the electrical conductivity differs widely between the samples obtained from the exposed old parts and those obtained from the restored parts (6.4 dS m-1 and 42.4 dS m-1 respectively). This indicates that a saline soil (EC 42.4 dS m-1) has been used in the recent restoration work, while the old non saline cobs’ building material, used by original builders, are thought to have been brought from other non saline areas. Smectite, illite, kaolinite and palygorskite were determined as the predominant clay minerals. Massive microstructure was found as dominant in all the samples, but igneous microlites and gypsum crystals were observed only in the repaired parts. The soil matrix from the old parts was found to be high in organic matter.

There are different methods of reconstructing hydrologic data. Depending on the conditions of the station a particular method can produce the best results. Generally, in order to estimate the lost data in a station and its surrounding stations, hydrologic, climatologic and/or physiolographic similarities are used. Recently, the fuzzy regression method has been used to reconstract the hydrologic data. In this research, the efficiency of this method in reconstructing the montly discharge data of hydrometric stations in comparison to other methods was investigated. The credited omission method was used in this investigation, then by omitting the observed data deliberately, their values were estimated using the different methods. Afterwards, by the use of the statistical index of root mean squared error (RMSE) the best method of reconstruction was determined. The results showed that the best methods of reconstructing monthly discharge data for the hydrometric stations in the great Karoon River basin in order of accuracy are artificial neural network, simple linear regression, multiple linear regression, normal ratio, fuzzy regression, autoregresive and graphical methods.

In the present study, the Soil and Water Assessment Tool (SWAT 2000) model was tested on both a monthly and yearly basis and applied to the Kordan Watershed, located in Iran. The main objective of the research was to assess the accuracy of the model in sediment-yield and surface water bicarbonate concentration estimation. The attributes of sub-watersheds, tributary channels and the main channel in each sub-watershed were generated using the Digital Elevation Model (DEM) and Geographical Information System (GIS) Arc View SWAT 2000 interface. The model was calibrated and validated for the period from 1990 until 2004. Calibration results revealed that the model predicted monthly and yearly sediment-yield, but not such good results were obtained for the bicarbonate concentration. Therefore, some efforts were made in order to find a solution for SWAT bicarbonate temporal modeling. Around 70 samples of the Kordan River water quality data were used and, upon doing statistical calculations, the best correlation between the average pH–EC of water and the bicarbonate concentration was obtained. The formula shall be tested at several watersheds, and it can also be defined to SWAT in order that the model is able to calculate bicarbonate concentration according to pH and EC of the river water, which are introduced to SWAT by the user as a stream water quality file (SWQ).