Journal of Agricultural Sciences and Natural Resources
Year:2006 | Volume:12 | Issue:6|Papers Count:27

The effect of discharge rate or drainage coefficient on water table build-up and its effect on crop production are important. A laboratory drainage model was used to investigate the effect of different discharge rates ranging from 4.617 to 42.12 cm3/s on 19 different water table profiles under steady state conditions. Soil used in the model was sandy loam with bulk density of 1.4 g/cm3 and saturated hydraulic conductivity of 0.53 m/day. The model had a drainage pipe and nine piezometers that were installed at 10 cm intervals inside the model. The results of statistical analysis showed that relationship between water table profile and discharge rate can be expressed by a polynomial of order 6 with coefficient of determination of more than 92 percent. The prediction of this polynomial function versus the measured data showed this function can predict the measured water table profile closely.  

In order to investigate the effect of applying different methods of Manning's roughness coefficient determination to estimate the amount of flooding area, HEC-Geo-RAS software was applied. This software can be linked with HEC-RAS and Arc View soft wares. A part of a river with 5.5 km length and 103 cross sections was considered and divided into 10 reaches by field observation. In order to estimate the amount of Manning's coefficient for main channels and banks of reaches, 5 different methods were applied as follows: Cowen, photos and slides, Iranian management and plan organization, soil conservation services (SCS) and Chow. Seven amounts of floods with different return periods were considered and their flooding areas were estimated by the mentioned methods. Comparison of the estimated flooding areas, by different methods revealed that some tens of thousands of square meters diversity could be achieved. Cowen and photos and slides methods had the lowest and highest estimations, respectively. Almost similar results were obtained from Cowen and SCS methods and from Chow and Iranian management and plan organization methods. The results of photos and slides method, on the other hand, were not comparable to any of the other methods.  

Circular-crested and cylindrical weirs are used for flow measurement and have wide applications in hydraulic engineering. They can also be used to control the water level in farm ponds and reservoirs. The advantages of the circular-crested and cylindrical weirs compared to other weirs include the stable overflow pattern, the ease to pass floating debris, the simplicity of design, the higher discharge coefficient and the associated lower cost. In this study, the hydraulic characteristics of circular-crested and cylindrical weirs such as the coefficient of discharge, the relative depth over the crest and the energy loss were investigated. A total of eighteen physical models, divided in five groups were tested. It is found that the coefficient of discharge of cylindrical and semi-cylindrical weirs increase when the relative total head is increased. It is also shown that in circular-crested weirs the variation of upstream and downstream slopes do not change the coefficient of discharge for a specific relative total head. The head loss for cylindrical weir is more than that of semi-cylindrical for a specific relative total head. For all the models head loss increases when the downstream slope is increased. The relative flow depth over the crest is 0.7 for cylindrical and semi-cylindrical weirs. The relative flow depth over the crest increases a little for relative total head greater than 0.6 when the upstream slope is increased and does not change with the downstream slope.  

Considering the growing population and increased demand for food in Iran, it is necessary to use sources of water more efficiently. One of the effective methods of increasing water use efficiency is sprinkler irrigation. In this method, in addition to accurate selection of sprinkler, net arrangement, pressure, and sprinkler riser level also affect water distribution uniformity and increasing water use efficiency. In this research, zb sprinkler at of 2.5, 3 and 3.5 atm, two riser levels 60 and 100cm and different arrangements 15×18m, 12×18m, 15×15m, 12×15m, 9×15m, 12×12m and 9×12m were evaluated under calm wind with three replications in Hashemabad Cotton Research Station of Gorgan. The results showed that, water distribution uniformity increased nonsignificantly with increasing sprinkler riser level from 60 to 100 cm. Maximum water distribution uniformity was obtained at 3 atm and under higher and lower pressures, water distribution uniformity decreased due to spray and drops of water. Water distribution uniformity was also maximized at 12×12marrangement but according to the economical condition it is better to increase the space of sprinklers so that water distribution uniformity will be maintained in an acceptable range (more than 80%).  

A proper understanding of factors affecting evaporation and drift losses in sprinkler irrigation is important for developing water conservation strategies. In semi-arid areas, the portion of water that might be lost due to wind and evaporation would be significant. The purpose of this study was to obtain formulas by using multiple regressions to determine evaporation and drift losses in semiportable sprinkler irrigation system under different water pressures (45 and 50 m) and weather conditions in south-east region of Khuzestan province. The standard ISO 7749/2 has been taken into account to determine evaporation losses. The type of field test was conducted under single sprinkler condition. The results showed that evaporation and drift losses increased from 20 percent when wind speed exceeded from 15 mps and vapour pressure deficit from 6 kpa. Therefore sprinkler irrigation is not recommended in this condition.  

Agriculture has played a key role in sustainable development because of its contribution in providing economic growth, food security, and employment opportunities. Therefore, it is vital to understand factors that influence production in this sector. Human resource is one of the critical factors that determine how effective agricultural sector can operate in order to provide food and fiber for the population at large. The purpose of this descriptive study was to provide a  conceptual framework for developing an in-service training program for personnel in agricultural organizations across the country. Using survey research design, a two stage cluster sampling  technique was adapted to collect data from specialists, managers, and supervisors employed in agricultural organizations. Results indicate that there is a large discrepancy between "current situation" and "degree of importance" for developing an effective program in human resources as a means of improving the organizations' towards a desired situation. A ten step model is proposed for improving the current situation and further recommendations are given based on the findings.  

In a greenhouse experiment tomato seedling (c.v.Cora) were inoculated with species of VA mycorrhiza (Glomus mosseae and Glomus intraradices) or left uninoculated as control plants in sterile and nonsterile with three levels of phosphorus (0, 20, 40 mg/kg). A factorial RB design was used with three factors of fungus, soil and phosphorus levels. Statistical analysis indicated that the main effect of phosphorus had significant effect on the shoot dry matter, vitamin C of fruit and percent root length colonization (RLC).The main effects of fungus on vitamin C concentration and percent RLC were significant at P< 0.01. Percent RLC was decreased significantly (P<0.05) with effect of (fungus * P level).The effect of (soil*fungus) was significant on percent RLC and vitamin C concentration of fruit. Correlation analysis between measured parameters indicated that shoot dry matter positively correlated with root dry weight and plant length (P<0.01).A positive correlation was observed between root dry matter and vitamin C content of fruit (P<0.05). Percent RLC positively correlated with vitamin C content of Fruit (p<0.01). Considering the results and necessity to reduce the rate of fertilizers application, P2 level, which is (20kg P/ha) less than the recommended rate for tomato, can be suggested without any reduction in quality of fruit as well as enhancing of mycorrhizal activity in tomato roots.    

To investigate the critical period of weed control in soybean, an experiment was conducted in Eraghi-Mahalleh Research Station, located at 7km of north Gorgan, Golestan providence in 1998. The experiment comprised of 14 treatments, which were compared in+ a complete block design with 4 replications. In this experiment the weeding time and its relation to reduction of soybean seed yield and yield components were investigated. The treatments were divided in two groups: The first group was kept totally weed free and the second one was kept weed infested up to some defined phonological growth stages of soybean. An exponential relationship between soybean seed yield and weed dry weight was observed. Continuation of weed competition to the later stages of crop development caused significant decreasing of yield components pod number per plant was the most important factor and had a highly positive and significant correlation with yield production (R=0.99). Seed number per pod and thousand-seed weight was less effective on final seed yield. The peak competition period of weeds in soybean crop was between formation of the third (V3) to seventh node (V7). If the weeds are controlled within this period, soybean would be protected against a significant seed yield reduction.  

In a field experiment the influence the used of planting date and seasonal changes on growth and nodulation of three alfalfa cultivars was studied. cultivars Sacoeal, Hamadani and Ghara-youngeh inoculated by Rhizobium meliloti, were planted in April, May and June 2001 at experimental farm of Urmia University, and carried out for two subsequent years. A split plot in space and time design with four replications was used. Monthly samples were taken to determine individual shoot dry weight and nodule weight per plant. Plant dry weight and nodule weight was higher in the May sowing date. There were significant differences between alfalfa cultivars in their shoot and nodule dry weight, Hamadany was higher than others. All species had marked seasonal peaks in shoot and nodule dry weight in end of the summer before flowering. There-after a rapid decline in the number and weight of nodules and in shoot weight were occurred once of flowering and cutting and subsequently by frost in the end of the growing season. Build-up of nodules in the second growing season which followed the vegetative growth, demonstrated that Rhizobia of the nodules was survived at low temperature in the region during winter.  

In order to study the effect of plant density and nitrogen rate on yield and yield components of 10 hulless barley genotypes, an experiment was conducted in research farm of Tarbiat Modarres University, College of Agriculture, (Tehran, Iran) during 2001-2002. This experiment was based on split-split plot design arranging in a randomized complete block with three replications. The main plots included ten genotypes of hulless barley, the subplots included two levels of nitrogen fertilizer (90 and 120 kg nitrogen/ha) and the sub-subplots included three-plant densities (300, 400 and 500 plants/m2). The results showed that there were significant differences between genotypes and plant density interaction for grain yield and harvest index. The highest grain yield, spike number/m2 and seed number/spike were produced by barley genotype ALLSO'S'/CIO 3902-2 (500 plant/m2). Genotype FICC2595 showed the highest 1000 grain weight (45 gr) and genotype FICC1570 produced the highest spike number/m2(625 spike/m2).The mean comparison of protein yield in different plant densities showed that the 500-plants/m2 treatments produced the highest protein yield (with 58.48 gr/m2).  

The effect of light competition and nitrogen fertilizer on canopy structure of wheat and wild oat was studied by two experiments. The 1stexperiment which carried out at the field research station was an additive experiment using a split plot experiment, based on a randomized complete block design, with 4 replications. Amounts of nitrogen topdressing (25, 50, 75 and 100 kg N ha-I) were assigned to the main plots and wild oat plant densities (0, 30, 50 and 80 plant m-2) were assigned to the subplots. The population of wheat was 400 plant m-2. The 2ndexperiment which was conducted at the greenhouse was a replacement series experiment using a factorial experiment, based on a randomized complete block design, with 4 replications. Amounts of nitrogen topdressing were 0, 0.5, 1, 1.5 and 2 grams per pot, and relative densities of wheat and wild oat were 100:0, 75:25, 50:50, 25:75 and 0:100. The results of the additive experiment indicated that, by increasing wild oat plant density, the proportion of upper layer of wild oat canopy from shoot dry matter and leaf area index was increased. In pure stand of wheat light absorption was more than mixed canopy and light was extended at upper height of canopy. Vertical distribution of shoot dry matter in both species was not affected by nitrogen amounts. In the replacement series experiment leaf nitrogen content at alllaters of wheat pure stand canopy was less than mixed canopy, whereas wild oat pure stand had more leaf nitrogen content at all its layers.  

Water availability is one of the important environmental factors that affect plant growth and development. In Gorgan and dasht region, wheat grain filling period is faced with water shortage. Therefore, Knowledge about the effect of the drought stress on vigor of harvested seeds is important  And helpful. In this experiment 3 post- anthesis moisture regimes, i.e, control (80% of field capacity), irrigation at 1/2 and 1/3 of the control, and two wheat cultivars (Tajan and Zagros) were used. Treatments were arranged as factorials were compared in a complete block design with 8 replications. After harvest, seeds were evaluated for vigor. Results showed that the cultivars were significantly different with respect to shoot dry weight and 1000- seed weight. Shoot dry weight and 1000- seed weight in Zagros cultivar 9% and 13.5%were greater than Tajan cultivar, respectively. Seed weight in both cultivars decreased with increase in drought stress level, but the decline was faster in Tajan compared to Zagros. In seed vigor experiment, there was no significant effect of drought stress, in cultivars and their interaction on maximum germination, germination rate and uniformity.  

In this study, for partially frying potato, changes in fatty acids content of two oils used before and after were studied. The results of this study showed that palmitic acid content of hydrogenated oils of soy and cottonseed increased about 0.86% due to partially frying at temperature of oil at, 100ºc for 5 min, this means that the amount of changes were from 10.72% to 11.85% of fatty acids, which was predictable, while stearic acid and oliec acid showed minor changes. The changes evaluated were from 5.54%to 5.78% for stearic acid and 36.76% to 34.81% for oleic acid respectively. Linoleic acid of hard oil reduced from 4.43% to 3.54% but in the case of sunflower oil (liquid), the reduction in palmitic and oleic acids were 0.38% and 0.63% respectively. Content of linoleic acid of same oil used for partially potato frying, increased from 60.76% to 61.05%, but linolenic acid of the same oil decreased, from 0.94% to 0.63%. Therefore, due to minor changes occurred in unsaturated fatty acids (USFA), especially linolenic acid content of sunflower oil is considered suitable oil for partially frying of potato.  

Iran is one of the worlds important areas for the production of pistachio nuts, the Ohadee variety of Iranian raw dry pistachio nuts was selected for the experiments. The method of Accelerated Shelf Life Testing (ASLT) used for storage and sensory properties (taste, texture and overall acceptability) of raw dried pistachio nuts were investigated at 21%, 8% & <2% O2 and different storage temperature (5, 20, 35 and 45ºC). Samples were experimented at 4, 6, 8, 10 and 12 weeks by use of split-plot design and estimate the modelling shelf of this product at various conditions. Results showed that the sensory attributes (taste and texture) under factors of time and O2% were significant (P<0.05) and maximum shelf life (284 days) for raw dried pistachio nuts determined at SC and <2% O2 based on overall acceptability. Linear regression second order function had a best fit with R2>98 at all levels of oxygen conditions (21%, 8% & <2% O2) for raw dried pistachio nuts.  

The brown spot disease is one of the seed-borne diseases of rice, which is found in all stages of its growth from nursery to farm. It causes qualitative and quantitative damage on rice. Although the disease can be found in all parts of the country where rice is cultivated, there is no precise information about its dispersal, species and the rate of damage. Therefore, this study carried out in order to identify the genus and species of the rice brown spot agent in Guilan. To do so, at first some samples were collected from 91 paddy fields in Guilan. In order to isolate the fungus from disease tissues the gathered samples were cultured on PDA and filter paper, and by this, 120 isolates were isolated. Isolates were cultured for sporulation on culture medium of TWA+wheat straw. In order to identify the taxonomy, conidium and conidiophore morphology and the process of conidium formation and pattern of its germination were studied. According to the results, the present isolates were belonged Bipolaris, which was divided into 3 species:  ipolaris oryzae, Bipolaris victoriae Nelson and Bipolaris sp. The total isolates were consisted of 15% Bipolaris oryzae, 75% Bipolaris victoriae and 10% Bipolaris sp. Pathogenicity test of isolates in these three species was applied on cultivar Khazar seedlings in desicator, which revealed the pathogenicity of the species and their ability to cause brown spot on rice.  

Antibiosis effects of 37 bacterial antagonistic isolated from rice paddy of the Guilan province were surveyed in vitro in preventation of the vegetative growth of the causal agent rice sheath blight (Rhizoctonia solani). Antagonistic strains caused a large changes on the pathogen include lysis and fragmentation, vacuolation, shriveling and swelling hyphal tip in the dual culture on PDA medium. In the test of production of antifungal volatile metabolites, effect of 15R (Pseudomonas fluorescense bv. 5) strain was the best than other (%77.16) in prevention of vegetative growth of the causal agent. None of the 37 antagonistic strains reduced inhibition zone in the test of production of siderophore in the different concentrations of iron added to King's B medium but among eight selective antagonistic strains, some strains increased the vegetative growth of the causal agent after removing bacteria and incubation in 60°C temperature on the King's B medium contained iron. In the test of extracellular exudates selective antagonistic strains in the different concentrations, effect of 133 (P. fluorescence bv. 5) strains in the %25 concentration was the best than other (47.50) in prevention of vegetative growth of the causal agent. Autoclaving (I21ºC, 1 at.) extracellular exudates of selective antagonistic strains in the %25 concentration influenced on the effects but this effect was little in prevention of vegetative growth of the causal agent by the extracellular exudates 23R (P. fluorescense bv. 5) strain.  

Verticillium wilt of olive by Verticillium dahliae kleb. Causes economic losses in olive orchards that are often greater than losses caused by any other diseases or pests. In this study, the effect of major salt of soil, NaCl evaluated on V. dahliae isolates from soil in Vitro. The limits of tolerance to NaCl (0-40 gr/l) was different among isolates and the isolates from high soil Ec had the highest salt tolerance (p< 0.05). NaCl resistance increased in NaCl -susceptible isolates after 11 times transferring to NaCl-medium and non-NaCl medium. The results show high probability adaptation of V. dahliae to salt changes in environment. To investigate of relationship between V. dahliae population in soil and soil EC on wilt severity in olive orchards, the population of V. dahliae in soil, soil EC and percent of disease in 44 olive orchards in Golestan province were assessed. Inoculum density and percentage of disease varied from 6-33 per gram of air-dried soil and 0.2 % - 6.2 % in olive orchards, respectively. The changes of Ec were between 2.5 to 12 mm/cm. The effect of inoculum density (propagules per gram of air-dried soil) and Ec of soils on disease (Y) were significant and fitted a Y=0.0247-0.28 Ec+0.163 Ms model with R2=0.66 and Significant F function (P< 0.0001).  

The attractiveness potential of locally-made sex pheromone of striped stem borer, Chilo suppressalis Wlk. (SSB), consisting of (Z)-9-hexadecenal, (Z)-11-hexadecenal, and (Z)-13- octadecenal (in the ratio 1:10:1) was compared with imported one. Doses of 0.5, I and 2 mg of the pheromones were used in sticky traps in rice fields of Rasht and Sowmaea-sera county during 2001-2002. Analysis of variance showed that there were significant differences between treatments at the1% level. Mean comparison of treatments at different locations, and generations showed the best at 0.5mg dose. Also, changing sex pheromone rubber septa at different times showed best results on 0.5 mg dose. The results showed that the efficiency of the sex pheromone decreased significantly with increasing storage period and maintenance condition. Using fresh pheromones in a 20-day interval are suggested for monitoring and forecasting studies of the stem borer's population. Therefore, considering good number of moth catches and easier and cheaper production of locally-made pheromone compared with the imported one it could be a useful component of the pest monitoring and control in integrated pest management (IPM) program.    

In a faunal study of whiteflies predators in 1999-2003 at different areas of Mazandaran and Golestan provinces, 64 species of Hexapoda and Acarina were collected and identified. The species were confirmed by the authorized specialists. All mites belonged to Phytoseiidae of Mesostigmata, and the predatory insects Coleoptera, Hemiptera, Neuroptera, Diptera, and Thysanoptera. The predator beetles that belonged to Coccinellidae, contain 25 species, and for Hemiptera, Neuroptera, Diptera, and Thysanoptera were 21, 3, 5 and 4 species, respectively. Among the identified predators, 4 species of Hemiptera including: Anthocoris confusus Reuter, Anthocoris flavipes Reuter (Anthocoridae), Geocoris marduk Linnavuori, and Geocoris ningal Linnavuori(Lygaeidae), and also Diplosis aphidisuga (Diptera: Cecidomyiidae) are new record from Iran. In this study, feeding efficiency of predators was also determined on the different life stage of Bemisia tabaci Gennadius in laboratory conditions. The results of feeding tests indicated that among the different predators, Chrysoperla carnea(Stephens), Coccinella septempunctata (L.), Acletoxenus formosus Loew, and Nabis palifer Seidenstucker with 72.l±37.5, 68.2±55.4and 56.l±46.9 fed preys had the most feeding efficiency, respectively.  

For estimation of the snowmelt runoff and testing the precision of simulation model in Ziarat river watershed, the SRM model (Snow & Runoff Modeling) has been used. Climatic, hydrologic and snow cover data have been collected through four different events during February to April 2001. Then the SRM model has estimated the stream discharge and net snowmelt runoff. To compare the estimated runoff by SRM model and observed values by direct measurement and hydrograph, by T-test, has conducted that, there is not any significant difference between observed and estimated values. It is concluded that the SRM model can be used properly for estimation of snowmelt runoff and related flood flow in I watersheds. It is further concluded that the factors such as physical characteristics of catchments area and the precision of existed data can be very important in properly stimation of runoff.  

Plane tree (platanus orientalis) as a fast growing tree species is a suitable tree for planting in urban areas and a forestation. But it has problems in terms of propagation. So, an experiment conducted to investigate methods of propagation by different cuttings. For this experiment, cutting branches of two years age with different diameters size of 9>mm (small), 10-5(medium) and 16-25 (big), with two and three buds, were used from Troq nursery. Cuttings planted vertically into loamy soil, so that one bud was out of soil. Data were collected for eight periods from March 31 to August 6 of 2004. The first sproutings were observed 10 days after planting. The trend of sproutings were fast by about 10 May and then became slow and ceased. Measurement of sprouting was cumulative. The results of cutting sprouting percentage by the end of experiment showed significant differences between big and small diameters. Cutting of big, medium and small size produced 97%, 93% and 89% of sprouting, respectively. There were no significant differences between two and three cutting buds. Cuttings of three buds had 94% and cuttings of two buds had 92% sprouting. In general, all cuttings produced more than 80% sprouting, so in spite of importance of sprouting in plant propagation and better results in which obtained from big cuttings, it seems that sprouting is not a main problem for plane tree.  

Genetic variation of Stellate Sturgeon (Acipenser Stellatus) from the North (Volga river) and South (Sefidrud river) Caspian Sea was investigated using NADH 5/6 gene and PCR-RFLP analysis. In this Study a total of 60 samples of Stellate Sturgeon from the North (Volga river) and 13 samples from the Southern (Sefidrud river) Caspian sea were collected. MtDNA ND 5/6 gene was amplified by polymerase chain reaction (PCR). PCR-product digested using 31 endonucleases restriction enzyme. Five enzymes of 31 enzymes showed polymorphism (RsaI, HinfI, HpaII, HaeIII and MhoI). Totally 22 composite haplotypes among 73 samples were detected. Haplotypes AAAAA, BAAAA, ABABA from the Volga River showed 28.33% and 11.66% frequency, respectively, and from the Tajan river haplotypes AAAAA, ABBAA showed 38.46% and 15.40% frequency, respectively. Average haplotype and nucleotide diversity within populations in Volga river was 0.88±0.027and 0.0122 and in Tajan river was 0.86±0.089and 0.0093, respectively. Average nucleotide diversity and nucleotide divergence among populations of North and South Caspian Sea were 1.126 and 0.047, respectively. Monte-Carlo simulation using 1000 replication was shown nonsignificant difference between sampling site in the southern and northern Caspian Sea (X2=0.036±0.006).