Journal of Agricultural Sciences and Natural Resources
Year:2005 | Volume:12 | Issue:2|Papers Count:19

SIRMOD is a simulation model used in design and management of surface irrigation system. In this model, Saint-venant equation is solved by Full Hydrodynamic (HD), Zero-Inertia (ZI) and Kinematic Wave (KW) methods. Performance of this model was evaluated in the field. This study was conducted on a clay soil located in research fields of University of Tehran. Flows of 0.8-1.2 l/s was deliverd to 200 m-long furrows with 0.75 width. Field tests for determining of advance rate, runoff, infiltration, flow geometry and inflow rate were conducted and the results were compared with SIRMOD model. The results show HD, ZI and KW models estimate advance and infiltration rates to be less than field observations. This study shows that advance rate of HD model is closer to field observations than ZI and KW models. In runoff comparison, model eoverstimated the observed data. Therefore overestimation of runoff inevitably result in lower estimation of infiltration volume.

Flow measurement is the basis of water distribution and management in the irrigation network, which is determined accurately by appropriate tools. In this paper, application of the Reploge flume was used for measuring and evaluating discharge rate as a measuring flume. A mathematical model has been defined for computing the stage - discharge relationship, and then it was compared with physical model data. Ideal flow (Qi) is supposed by mathematical model and boundary layer theory was used to determine energy losses. The actual discharge was computed with ideal discharge (Qi); energy losses and velocity coefficient. A satisfactory result was obtained in comparing physical and mathematical model data. Therefore it is recommended that the flume to be used in irrigation network in Iran.

Groundwater is the main source of water supply in many plains in Iran, including Mashhad plain. With increasing population and urban, industrial and agricultural activities, groundwater is exposed to pollution. Nitrate is one of the main contaminants in groundwater. The purpose of this study was to determine the nitrate pollution level and its origin in Mashhad plain. Fourty water wells were selected in different agricultural, industrial and urban regions of Mashhad plain. Sampling was performed monthly, for six months of July - December 2001. N03-, EC, pH, TDS, C03-2,HC03-, cl-, S04-2,Ca, Mg, Na, K, BOD, COD and Coliforms were measured and compared with different standard limits.The results showed that nitrate concentration in some parts of the studied area was more than the maximum permissible level (45 mg/L). Mean nitrate concentration varied between 5.3 to 74.4 mg/L. Highest nitrate pollution was in urban and populated parts of city of Mashhad. Water wells in agricultural and industrial areas had desirable quality. Mean EC of water samples varied from 0.4 to 3.2 dS/m, TDS from 230 to 1995 mg/L and total hardness from 152 to 1037 mg/L. Nitrate concentration in Jomhori square, Seyedi and Sheshsad-dastgah areas were 74.4, 68.5 and 49 mg/L, respectively, and its origin was due to leakage of domestic wastewater into the groundwater.

Knowledge of crop evapotranspiration, the combined process of evaporation and plant transpiration, is important in agriculture for scheduling farm operations and designing and managing irrigation and drainage systems. Weighing lysimeters are the most practical research method for direct measurement of short-term evapotranspiration. The main objective of this research was design, construction, and installation of two weighing lysimeters at Agricultural Research Station of Tehran University located at Karaj in order to determine the consumptive use of agricultural crops and reference crop. The lysimeter used for agricultural crops has a surface area of 9m2 with soil depth of about 2m. The one used for reference crop (grass) has a surface area of 16 m2 with soil depth of 1 m. Each lysimeter rests on a sensitive scale capable of measuring to the nearest 1000 gr. The weighing system is electronic with four load cells were used in each lysimeter for weighing operation. The weighing system accuracy is 0.1 and 0.06 mm of water depth for the first and second lysimeter, the soil tank was steel-made and reinforced against imposed forces and filled with disturbed soil.Lysimeters have been installed in the direction of the prevailing wind and 400 meter far from the farm edge. These lysimeters have free-drainage system. In this study, all limitations regarding to design and execution of lysimeters were taken into account.

To determine the effects of salinity on growth performance and carbon isotope discrimination three pistachio rootstocks (Badami-e-zarand, Sarakhsi and Ghazvini were used. Rootstocks were grown in soil in polyethylene pots. Sodium chloride treatments were 0, 75,150 and 225 mM NaCl. Plants were harvested before and after 30 and 60 days of exposure to the salinity treatments. Results indicated that relative growth rate decreased with time for all treatments and rootstocks. Salt treatment significantly reduced both relative growth rate (RGR), net assimilation rate on a leaf weight basis (NARw) but not leaf weight ratio (LWR) was significantly correlated with RGR, indicating that NARw was an important factor underlying the salinity-induced differences in RGR among the pistachio rootstocks.Salinity did not effects on leaf water potential, chlorophyll content and Fv:Fa ratio but with increasing of NaCl, proline accumulation in the leaves was increased, from selected rootstocks, so Ghazvini rootstocks accumulated more proline in compare with other rootstocks indicated more resistant to salinity. Results showed that carbon isotope discrimination reduced by salinity treatments in both leaves and stems, however no significant differences were observed between rootstocks. Carbon isotope discrimination in the second harvest was more than the first harvest, but this variation observed in leaf but not in the stems. We conclude that carbon isotope discrimination in pistachio rootstocks will be indicator of cumulative salinity history of plant but not a suitable indicator for prescreening of pistachio rootstocks to salinity resistance.

Diosgenin is a widely-used starting material for the semi-synthetic production of steroid drugs. It is obtained mainly from the tubers of Dioscorea composite, D.Floribunda, D.deltoidea and some species of Tamus (Dioscoraceae) in the tropical forest areas. Tamus Communis has been reported as a source of steroidal sapogenin. The plant used in this study named Tamis (or Razak) was collected in Afra Tapeh forest (Ali-Abad city, Golestan Province), north of Iran. The sample of plant material was seperated into rhizome, leaves and berries. Acid hydrolyzed tissue was dried and extracted with chloroform. We used three different hydrolysis methods. Among them, method C (sulphuric acid in isopropanol) showed more diosgenin. In this study we showed, the sapogenin mixture and diosogenin concentration in rhizome is higher than other organs but there was no significant difference (P<0.1). About the catbohydrate moiety, the TLC indicated the hexoses and pentoses in the leaves and stem, but no pentoses in the rhizome and seeds. In the rhizome, the amounts of soluble and insoluble sugars are more than other parts.

Microscopic studies on the lichen flora of ascomycetes in Golestan province, show that this lichen flora have a rich variety and in this research, in order to compare with other resources of this region and Europian and Asian countries, 9 species of 5 family were described. Most of the identified species belonged to Lecanorales. All of the identified lichens of this research are the epiphytic lichens of the north of Iran; that their characteristics and morphology as the macroepiphytic species on the forest trees of golestan province, is presented: Cladoniaceae: Cladonia coniocraeaLecanoraceae: Bryoria capillaris                     Evernia prunastri                     Xanthoria parietinaParmeliaceae: Flavoparmelia caperata                     Parmelia sulcuta                     Punctelia subreductaPhyscicaceae: Physcia adscendensUsneaceae: Usnea articulata

There are evidences that bread quality in Iran has been deteriorated in recent years, mostly due to employing wheat flours with low quality. In order to choose the best flour suitable for Taftoon bread, physical, chemical, rheological, and sensory properties of flour bread wheat produced in Isfahan province were investigated. The results indicated that chemical properties i.e. starch damage, acidity, pH, colour, and ash had no significant effects on baking properties of the flours. Flour particel size, protein, and wet gluten content and sedimentation value were however, the most significant factors affecting baking quality of the flours. Water absorption data obtaind from farinogram along with other rheological characteristics indicated that 400 BU line was the best line to be employed for adding water to prepare a suitable Taftoon dough.The lowest shear stress was found in breads made from Ghods wheat flour immediately after baking and after 24hr storage, followed by Omid bread after 48 hr storage, however the highest shear stress was belonged to Mahdavis bread samples in three varying periods. According to the results, baking properties of Omid and Rooshan wheat flours were considered to be good where as those of Ghods and Mahdavis samples were medium and weak, respectively.

A study was conducted to determine resistance of 150 sugarcane varieties to a mixture of stem borers (Sesamia cretica and S. nonagrioides) at harvest time in year 2000. Screening for resistance has been carried out under natural infestation in the field condition at two prominent Agro-Industries located in Khuzestan, southern province of Iran. Percentage of bored internodes was used at both stations. In order to unify the findings of two stations, a bored internode index (BII) was created.Since the distribution of the finding was in a normal pattern, an intervals of standard deviation from the mean (ISDM) was developed to classify the varieties. Following the classification, canonical discriminate analysis (CDA) was used to assess the contribution of variables to separation, and also investigate the effectiveness of the classification procedure. The result of CDA confirmed the accuracy of the classification procedure used, showing that 98% of the original data was correctly classified in the predicted group membership. Moreover, hierarchical cluster analysis was used to group varieties into resistance potential classes. There were no substantial differences between the results obtained by the method of ISDM and those of the cluster analysis. The finding showed a significant positive correlation of Percentage of bored internodes between the two stations. Consequently, in spite of the considerable differences in the levels of bored internodes between two stations, it is concluded that the resistant varieties might be durable. Throughout the research process, varieties of sugarcane have shown a wide spectrum of resistance to stem borers; therefore potential long-term breeding program should address this resistance problem.

It is necessary to identify potential of biocontrol agents for use against lepidopterous pests in fields and gardens. The solitary endoparasitoid Meteorus gyrator (Thunberg) attacks a range of macrolepidopterous larvae, including those of important crop pests and also the rice armyworm, Mythimna unipuncta (Haworth). Laboratory trails designed to investigate the biology and morphology of M gyrator on larvae of the rice armyworm, M. unipuncta shows that parasitoid have different stages including egg, first, second and third larval instars and pupae and adult. The egg and larval stages as solitary parasitoid are in the host larvae and in the last larval instar emerges from host larvae and change into pupae. This study revealed that the parasitoid is capable of parasitizing all larval stages of its host, third instars being parasitized most frequently. Each female parasitoid lives for up to 40 days (at 25oC), ovipositing into an average of 70 hosts. Pre adult development is rapid (about 2 weeks), and sex ratio of offspring is 1:1. This parasitoid is capable to parasitize and destroy between 10% to 30% of M.unipuncta larvae in critical months (August and September). The parasitoid can exist on different hosts in cereal crop, vegetables and woody plants in autumn and winter and therefore is capable to preserve its population and begin to parasitize Mythimna larvae in upcoming year and in the rice fields.

Biological studies on predacious pentatomid bug, Andrallus spinidens showed that the larvae of the green rice semilooper, Naranga aenescens were the most important prey of the predator in Guilan rice fields. The functional response of the predator A. spinidens was tested at various densities of the Naranga aenescens (2, 4, 8, 16, 32 and 64 larvae) under laboratory conditions (26±1 oc and 56 ± 2% R.H. and 10 D: 14L Period light). The Holling disc equation fitted to the data. A type 11 functional response curve was exhibited by the adults of A. spinidens. The instantaneouse searching efficiency (a) was 24.86 and 20.15, respectively after 8 and 24 hours.

Low flow is a complex phenomenon that different factors directly or indirectly affect on its procedure. This factors contain edaphic, climatic and management factors. Morphogenetic characteristic are the important edaphic factors which with regard to less changeability and affecting on flows procedures has the especially importance. Morphometry factors with climatic and geology is the principal factors in hydrologic interactions. Although, principal method for morphometey and flows relations investigating and analyzing relations between watershed characteristic, climatic data and flow characteristics. Identify effect factors on low flows has the especially importance. To determine the effective factors on low flow, Tehran province watersheds were divided into 12 sub-watersheds. Then, all affects physical and climatic factors on low flow in each sub-watershed using GIs was recognized. In addition Drainage densities Graveluous, Miller, Schumm, Horton coefficient, and unit shape factor were calculated. Then these factors were analyzed using the principal component analysis. Based on the most effective factors were: Area, mean annual precipitation, average weighted infiltration and average slope of the watershed that illustrate 99.36 of variation of data. Then homogeneity areas were identified using cluster analysis and two-homogeneity area was obtained.

Most areas in our country are subject to frequent flood damages and increasing loss of lives and properties. This research present a methodology, based on the use of mathematical hydrologic models simulating mutual interaction of effective factors, to study the spatial distribution of flood producing areas with in watersheds. The watershed of interest, Damavand, was divided into seven subwatersheds which were digitally characterized in a geographic information system (GIS). Subwatersheds flood hydrographs associated with design rainfalls were determined using HMS model and were routed in the stream network to yield the total hydrograph at the outlet. With successively eliminating subwatersheds from the simulation process, in a method titled "successive single subwatershed elimination method", flood hydrograph at the outlet was determined so that the contribution of each subwatershed in the flood peak at the outlet could be quantified. Then, all subwatersheds were ranked with respect to the order of contribution to the outlet flood peak. The routing results show that this contribution is not only a function of subwatershed discharge and size but also a function of other factors. Thus, any flood control measure must consider the flood area prioritization in term of contribution at the outlet.

There are 32000 hectares tea plantation in Guilan Province and about 83% of tea orchards are located in steepy area. For some reasons, erosion is the main problem of these area, which causes heavy soil losses on surface horizons. To estimate soil erosion by Cs-137 method, at the first, the content of Cs-137 must be determined in various sites of study area and reference profiles, then by the help of mathematical relation between Cs-137 and erosion (Zhang equation), the amount of surface soil erosion can be determined. This research was carried out at the north and South facing of steepy regions under tea cultivated area. The average of surface soil erosion is estimated as 4.84 tons per hectare in year Since the parent materials of the region is granitic, the soil development is weak and soil formation is slow, therefore the erosion must be really controlled. The main reasons of this high level of erosion in these area, incorrect land using due to high slope and bad management of tea orchars. So it is necessary to train the farmer of these regions and show them the scientific and correct manner of tea cultivation.

In this study in order to reducing using of pesticides and herbicides and effective removing of row crops weeds was designed and constructed one row from four rows of mounted tractor rotary cultivator in agricultural engineering research institute in Karaj. The power supply source of system was tractor Pto shaft. The main parts comprise transmission unit, tillage unit, adaptation with rows unit was designed then was evaluated performance of machine by RNAM test procedure in Karaj Kamal Abad sugar beet research station. After working of machine in five meters distance and three replications, results proved weeding efficiency is varied between 87%-93% and theoretical field capacity for four rows is 0.6-0.64 hectare per hour and operating costs for rotary cultivator is 95% less than conventional-hand working-method.