نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال چهارم شماره 2 (پیاپی 12، تابستان 1379)

Peak discharge is one of the basic parameters in the design of hydraulic structures. There are various methods for peak discharge determination. Regional flood frequency analysis is based on physical, climatological and hydrological characteristics of basins. The objective of this study is to examine different models for the estimation of quantiles for some catchments in western Iran (namely: Gharehsoo, Gamasiab, Kashkan, Seimareh, Sezar and Abshineh) for which only maximum daily mean discharge data exist. In this research, peak and maximum daily mean discharges for 11 stream gauging stations were collected for a 21-year period. The ratio of these two discharges (R) and mean and standard deviations of peak discharges and maximum daily mean discharges were computed. Catchment characteristics including catchment area, catchment perimeter, main channel length, mean elevation, mean slope equivalent rectangle length, circular ratio, Gravelius coefficient, drainage density, time of concentration, relief ratio and diameter of the circle having equal area with the catchment were computed. Linear regression analysis was performed between independent variables of the catchments and mean standard deviation of the parameter “R” to develop a relation. The results of this study can be applied to the estimation of extreme flow values for non-recording stream gauging stations (daily reading sites).

In this study, seven citrus gardens in different parts of Darab were chosen to evaluate the drip irrigation systems. The evaluation process was based on the Merriam and Keller’s model (1978). Besides the evaluation of drip irrigation systems, the water requirement of citrus was estimated using four models including Blany-Criddle modified by FAO, Hargrive-Samani, Pan Evaporation and Solomon-Kodama model. On the basis of the results obtained by Hargrive-Samani with 1296 mm annual water requirements, a comparison was made between irrigation with existing systems and irrigation under favorable and desired conditions. The results from field measurements indicate a considerable reduction in the emitter discharges. The low pressure and emitter clogging could be two major reasons for the problem. Low pressure at head control, topography, head losses and also using no filter(s) or unefficient filters are the main reasons for the reduction. In some gardens, overirrigation even up to 2.5 times of water requirement was practiced by using extra emitters and increased irrigation times. Overirrigation causes considerable water losses through deep percolation and in reased overwetting area. Field measurements indicated a good emission uniformity (EU) for the fields with overirrigation. EU in chosen fields varied from 40 to 91%, AELQ varied from 31 to 82% (poor to good) and PELQ varied from 36 to 82%. This study showed that most farmers are not familiar with plant water requirements. The fields with efficient filtration due to using extra emitters per plant are mainly overirrigated. But fields without any filter of unefficient filters are not irrigated sufficiently. The very high manufacturing variation coefficient of IEM emitters (Cv=0.22), which are widely used in Darab, causes a design emission uniformity of 55%.

The application of “Modified Einstein Procedure” is recommended by the Specialized Committee on Sediment, Iranian Ministry of Energy. However, this method has not been applied to any river in the country. It is the purpose of this study to investigate the total sediment load of the Karun and Karkheh rivers at Ahwas and Hamidieh stations. The graphical calculations of the method are very complicated and time consuming. Therefore, a mathematical model has been developed in this study to improve the accuracy, simplicity and speed of computations. The required data were obtained from the above stations for seven years (1988-95), and applying these data, the total sediment load was calculated using the model. The bed load for the above stations was also computed and the ratio of bed load to total sediment load was calculated. In addition, measured data from East Fork river (in USA) were applied to examine the accuracy of the method in estimating the bed load. Comparison of the measured and computed results shows that the “Modified Einstein Procedure” estimates the amount of bed load with a high accuracy. The relationship between the bed load and suspended load and also between the total load and the stream discharge have also been established. Finally, it is concluded that the “Modified Einstein Procedure” with minor modifications can be successfully applied for the above-mentioned rivers of Karun and Karkheh.

Mutual understanding among officials and followers has been a point of concern in behavioral management. Natural resources extension which, from the very first step, is concerned with the exploration of practical problems is in serious need of an atmosphere of mutual understanding between agents and clientele. In this research, attention was drawn toward the measurement of mutual understanding between executives and nomads regarding nomads’ problems in utilizing natural resources and breeding cattle in Isfahan Province. For this purpose, initially, understanding between nomads and natural resources administrators (extension agents and specialists) regarding their respective problems were measured and compared. The research population of the study consisted of two groups. The first, involved 32 administrators, extension agents and specialists, and the second, 75 nomad families. Two different questionnaires were developed for the study as research instruments in which 52 items regarding nomad problems were included. Each part of the population was asked to rank the items accordingly. Then, some nonparametric tests such as Kruscall Wallis and Mann Whitny U tests were applied to compare the mean rank for each item within and between the two groups. Results showed that the administrators and nomads had different attitudes in only two of the 52 items. Administrators had no statistically significant different attitude in 52 problems. Eliminating the discriminating items, the attitudes in only two groups were compared and results showed that they had no significant difference in the remaining 48 items. Therefore, extension agents can follow these problems based on their mean rank priority in their developmental projects. This method of data reduction and understanding field constraints can be applied to the studies dealing with planning agricultural and/or natural resources development projects through extension education.

Marine products are currently important in Iran due to the following reasons: 1) aquatics are recognized as safe and healthy food by food scientists 2) because of low dependence of fishing technology on foreign resources, they are more reliable sources for protein and food security. Therefore, it is important to increase labor productivity using advanced fishing technology under a sustainable fishery management policy. In general, the prevailing methods of fishing in the southern coasts of Iran can be classified into three groups based on the level of technology and the length of journey made: traditional, semi-industrial, and industrial. In this study, labor productivity in the traditional and semi-industrial groups were compared using data obtained from a sample of 35 fishermen in Bushehr Province. To determine the marginal and average labor productivities, transcendental production functions were estimated for fish and shrimp, separately. The findings indicated that the marginal and average productivities of labor in semi-industrial fishing were significantly higher than in traditional fishing.

As apparent Zn recovery in mineral soils (saturated and unsaturated) is nill, the precise assessment of processes responsible for Zn retention in these soils is of great importance. A laboratory study was conducted to characterize Zn adsorption in eight lowland calcareous soils. The fit of sorption data was evaluated by Freundlich and Langmuir isotherms. In this study, 2-g soil samples were equilibrated for 24 hours with 40 mL 0.0lM CaCl2 solution containing 5 to 500 mg Zn L-1. The amount of Zn adsorbed was calculated based on the difference between the initial and equilibrium Zn concentrations. Zinc adsorption data were fitted to a linear form of Freundlich equation. However the Langmuir isotherm was divided into two distinct linear portions, representing two different types of adsorption sites. The Langmuir K1 was higher and adsorption maxima (b1) was lower in part I (corresponding to lower Zn concentration) than in part II (corresponding to higher Zn concentration). Thus, it seems that in parts I and II, sites are more important for their high adsorption energy and adsorption capacity, respectively. Langmuir adsorption maxima (b2) was positively correlated with clay content, CCE and P concentration and negatively correlated with CEC.

In order to find the critical period of weed control, the best time of weed control beginning (i.e. herbicide application time), and the length of weed control period (i.e. herbicide persistency) in corn, field experiments were conducted in Bajgah and Kooshkak in Fars Province in 1995 using a randomized complete block design with 14 treatments and four replications. Treatments consisted of different times of weed control beginnings (20, 30, 40, and 50 days after corn emergence), different duration of weed control periods (10, 20, and 30 days), a weedy check, and a weed-free check during the period of corn growth. In Kooshkak, a 10-day duration of weed control period had significantly lower corn yields than 20 and 30-day periods. In Bajgah, a 10-day weed control period had significantly lower corn yields than a 30-day period. Time of weed control beginning was not significant at both locations however, the interaction between beginning time and the duration period of weed control was significant. It appears in both locations that a minimum 20-day control period at the initial stages of corn and weed growth, and a minimum 30-day control period before corn pollination are necessary to prevent corn yield losses. In order to prevent corn leaf area decline at both locations, a 20-day weed control period until 40 days after crop emergence is necessary.

Diallel crosses of six breeding inbred lines of corn (Zea mays L.) were used to estimate combining abilities, heterosis and some other genetic parameters for yield and some of its components. Parents, 15 F1 crosses and 4 filler genotypes, were evaluated in a 5×5 simple lattice design. For all the traits studied, except seed length, the efficiency of lattice design was less than one. Therefore, data were analysed as a randomized complete block and after eliminating the filler genotypes, Grriffing’s method 2 with mixed B model was used in the genetic analyses. General and specific combining ability (GCA and SCA) mean squares were statistically significant for all traits studied. The ratios of GCA to SCA mean squares were greater than one for all traits, except for the number of seed rows per ear, indicating the importance of non-additive gene effects in their genetic control. Low heritability estimates and degrees of dominance lower than one were further evidence of the presence of non additive gene effects for all the traits studied, except for the number of seed rows per ear. Therefore, production of single cross hybrids in order to take advantage of non-additive gene effects is of prime importance for grain yield, number of seeds per ear row, l00-seed weight, seed length, ear length, and comb percentage. For genetic improvement of number of seed rows per ear, selection methods for parental lines will be more efficient. In the hybrids studied, number of seed per ear row and l00-seed weight played a more important role in the observed variations in yield. In general, hybrids 4×5 and 5×6 with high SCA for number of seed per ear row, l00-seed weight and grain yield were considered favorable for the conditions of this study.

In order to determine the most suitable cultivar and N level based on yield and silage value of forage sorghum, an experiment was conducted in summer 1995. The experiment was arranged in a split-plot design with four replications. Two levels of N (300, 500 Kg/ha urea) were the main plots and the subplots were three sorghum hybrids (Sugar graze, Super dan and Speed feed). Seeds were hand sown on June 29 with an inter row space of 50 cm and a final density of 20 plant/m2. The results showed that when the N rate increased, forage yields and percent of protein in forage and silage increased. Also panicle dry weight increased at anthesis. The N rate had no significant effect on other traits. A significant difference was observed among hybrids for all characteristics measured. Sugar graze with a bigger stem diameter was taller and produced higher number of leaves. At anthesis, plant leaf and stem dry weight was also highest for Sugar graze however, the highest panicle dry weight belonged to Speed feed. There was a significant interaction between hybrids and N levels for dry matter production. The percent of leaf, stem and panicle dry matter was highest in sugar graze, Super dan and Speed feed, respectively. The Sugar graze produced the highest forage and dry matter yield. This hybrid produced 30 ton/ha of dry matter and 97 ton/ha of forage, respectively. Furthermore, this cultivar had the highest percent of forage crude protein (7.45%) and the least percent of forage crude fiber (25.12%). Ensiling caused a decrease in percentage of crude protein and an increase in crude fiber. The Sugar graze and Speed feed had the highest and lowest dry matter digestibility, respectively. Based on the results obtained from this study, Sugar graze was found to be the most suitable hybrid due to its highest forage and dry matter yield and better silage quality. Higher N rate (500 kg/ha) is also recommended for higher forage yield and higher percentage of protein.

Obtaining high seed and oil yields of sunflower requires coincidence of vegetative and reproductive stages of growth of the plant with suitable environmental conditions via selecting appropriate planting date. Since the suitable date of planting for sunflower cultivars under Isfahan environmental conditions was not determined, this experiment was conducted in 1996 at the Agricultural Research Station, Isfahan University of Technology. In this study, five dates of planting (April 27, May 12 and 27 and June 12 and 29) and three open pollinated sunflower cultivars (Record, Vnimik 8931 and Armavirec) were evaluated using a randomized complete block design with split-plot layout in three replications. Date of planting was considered as the main plot and cultivars were randomized in the sub-plots. Number of seeds per head (SH), l000-seed weight (SW), seed oil percent (SOP) and, consequently, yields of oil (OY) and seed (SY) were significantly reduced as planting was delayed. Reduction in these traits were considered to be related to the coincidence of vegetative and reproductive growth stages with higher temperatures prevailing at later plantings. Vnimik 8931 had higher SH and SW, and thus produced higher SY. This cultivar had lower SOP than Record, but produced higher OY than Record due to its higher SY. Armavirec was ranked the least for the measured traits, except for its SH that was slightly higher than that of Record. SH was the most contributing trait to the increase in SY, and SY was the most determining trait for the increase in OY. Date of planting by cultivar interactions for SH, SY and OY were significant. Nevertheless, the highest amount of the measured traits were obtained with Vnimik 8931 at the first planting date.

The esterification process causes some desirable changes in physicochemical properties of fat by exchanging the acyl groups in triglyceride molecules. The aim of this study was to produce a suitable edible fat for industrial and home uses. In this study a mixture of 60 percent soybean oil and 40 percent edible tallow were inter-esterified, using 0.5 percent sodium methylate or ethylate as catalyst. The results obtained for solid fat contents and melting points indicated that the process of inter-esterification was accomplished in 30 minutes at 90°C. It was also observed that sodium methylate and. ethylate had similar effects on physical and chemical characteristics of the esterified blend. Iodine and saponification values indicated that the esterification process did not have any considerable effect on the degree of unsaturation or molecular weight of fatty acids. The peroxide values showed that the processing condition did not produce any peroxide. The esterified blend contained 1.10 percent trans fatty acids, which were originally present in the tallow. It is concluded that interesterification of soybean oil and edible beef tallow can be used as an alternative method to hydrogenation to produce a suitable plastic fat with low levels of trans fatty acids for the manufacture of different types of margarines and fats for home uses.

The difficulties of control of greenhouse whitefly on crops and greenhouse plants make extensive studies and investigations necessary in different areas of Iran. Morphological and biological studies were carried out on a prevailing species of greenhouse whitefly, Trialeurodes vaporariorum Westwood, in Isfahan. In this study, six species of whiteflies T. vaporariorum on Althaea sp. and Lantana camara, Bemisia tabaci Gennadius, B. argentifolii Bellows & Perring and B. hancoki Corbett, on Lantana camara, Aleyrodes proletella L. on Brassica sp. and Aleyrodes rosae on Rosa sp. were collected. These species were described using different identification keys. Morphological characteristics and different growth stages of greenhouse whitefly including egg, 1st to 4th nymphal instars and adult were defined and figures drawn. Biological studies were conducted in 24±1°C, 65±5% RH and 16:8 (L:D) on eggplant, solanum melongena. The developmental time for egg, 1st, 2nd, 3rd and 4th nymphal instars was 7.33±0.48, 3.37±0.52, 3.25±0.45, 2.51±0.26 and 7.66±0.83 days, respectively. The total period from egg to adult lasted 24.12±0.51 days. The number of eggs laid in 24 hours varied between 1 to 10 with an average of 5.93±1.67. Life-span of the male ranged between 19 to 23 with an average of 20.88±1.54 and that of the female varied between 20 to 28 with an average of 26.44±1.17 days. Four nymphal instars were identified and three substages for the 4th nymphal instars were determined. There was a positive correlation between nymphal instars and average body length and width. Since only male offsprings were produced through parthenogenesis, the strain of greenhouse whitefly in Isfahan was found to be European.