Journal of Agricultural Sciences and Natural Resources
Year:2002 | Volume:9 | Issue:3|Papers Count:22

The aim of this research is evaluation of proper length of record for estimation of mean annual sediment yield, its relation with climate, geology as well as vegetation cover and finding the optimum statistical period for suspended sediment sampling. In this research, it is tried to define actual (or best) mean annual sediment yield. For this study, 15 watersheds with sediment gauging station were selected around the country (Iran). Suspended sediment yields were calculated from 1 to n years (n is the most recent available data) for each station by suitable equations and water-discharge data. For determination of the proper lengths of record for each station and the length of time after which mean annual sediment yield stabilizes in each station, mean annual sediment yields were compared with the most recent annual mean (n year) as the most valid mean. Then, the variations from mean (standard deviation of the best mean) were calculated and each year that its variation was less than 10% was chosen as the optimum statistical period of data for that station. After that, the relationship between optimum statistical period and climate, geology and vegetation cover of the watershed was studied. The results have shown that the optimum statistical period for 13 stations is between 9 to 25 years. With increase of the area, percentage of annual sediment yield variation, percentage of sensitive and semi-sensitive geological formations and decrease of annual rainfall and De martin climatologic index, optimum statistical period also increases.

In this research, the effects of water spreading on physical and chemical characteristics of soil including EC, pH, the percent of sand, silt, clay and soil water saturation were studied. The research was conducted at two close areas: the control and the spreading area. Water spreading was designed, so that the flood water was transported by transition channel to the first diffusion channel and to the next spreading channel. The experiment was performed based on CRD design and the means compared by Duncan's multiple rang test. The samples were randomly gathered from 0-30 centimeter depth from the control area and adjacent water spreading area then physical and chemical characteristics were analyzed for each sample. The analysis of variance indicated that there is a significant difference between flood spread and control areas at 0.05 and 0.01 levels. Also, mean comparison tests showed that the maximum variation percentage is related to the first diffusion channel. The difference decreases when far from of the first spreading channel. So that at the first flood area all factors showed a significant difference in comparison with controls area. While no significant difference observed between the control area and the fifth flood area.

Nowadays, thermal springs are very important from economic, geology medicine and tourism. Thermal spring of Ziarat is the unique thermal water of Golestan Province, which are undergone chemical and isotopic studies for determination of its properties and origin as well as its potential for other applications. This water springs with annual flow of about 52 lit/sec and means temperature of 30°C has hydrochemistry facies in limit of Na+Cl- and Na+CO3-. Dominated cation is sodium while dominatedanion is chloride. Hydrochemistry properties and geothermometery of this spring indicate that the feed system and input to reservoir are scatter and dispersive while output system is conduit and under pressure. So that, it is not considered as a hydrothermal spring. The high temperature of this spring is due to thermal gradient. Isotopic studies reveal that the origin of water is not old and traces of new precipitation are very low. The feeding of this spring is from precipitation of highest part of watershed. The flowage occurs at depth and is not related to surrounding springs.

Monthly and annual precipitation data in Iran were explained by a variety of statistical distributions. For a certain station precipitation distribution had been reported differently by different researchers. Range of annual precipitation in Iran was from 25 mm for Shahdad to 2000 mm for Tawalesh-e Gilan in coast of Caspian Sea. In this paper, normal, two parameter lognormal, three-parameter lognormal, two parameter gamma, Pearson type III, log Pearson type III and type I extremal (Gumbel) distributions were fitted to the monthly and annual precipitation data of the oldest stations in Iran including Bushehr, Isfahan, Mashhad, Tehran and Jask. To test the goodness of fit of distributions Kolmogrov-Smirnov test, mean relative deviation, and mean square relative deviation were used and among which the log-Pearson type III was the best for fitting to monthly precipitations and we couldn't choose a unique distribution for fitting to annual precipitations.

Almond is one of the most important horticultural crops in Chahar-Mahal and Bakhtiari. At the present time more than 4000 hectares of this region is under the cultivation of Almond. One of the problems in these orchards is the late chilling which causes 80% decrease yield in many years. Study of agroclimatic conditions, especially daily temperature in March, April and May helps determination of occurrence and return period of late chilling. In this study, absolute temperature and daily frost data were prepared from Shahrekord Synoptic Station form 1975 to 1996. Data were corrected for Saman region using temperature gradient and interpolation equation. Weibull formula was used to calculate probability occurrence and return period at different stages, i.e., flower initiation, full bloom and fruit setting. According to the results obtained, some recommendations are given in this paper; (a) suitable varieties (i. e., varieties with late blooming) should be used (b) gardeners should be trained, precisely informed and taught prevention and campaign methods against spring chilling.

Three cotton cultivars of Sahel, Siokra and Delta-Paine were sown in different dates, and their seeds were harvested at the stage of the opening of the boils. Then germination tests were conducted on these seeds. The percent of germination, the length of root and shoot and the dry weight of the root and shoot and the total seedling dry weight were measured. Results showed that the planting date did not have any significant effect on the germination percentage and the length of the root and shoot. But with delay in planting date, the dry weight of root and shoot and the total seedling dry weight in Delta-Paine decreased significantly. However, two other cultivars were not affected by planting date. These results show that under the condition of this experiment, the seeds of Delta-Paine cultivar that are produced from the earlier planting dates have more seedling growth rate compared with those produced seeds from the later planting dates. But the seedling growth rate was similar for other two cultivars obtained from different planting dates.

Effect of salinity (sodium chloride) on growth, biological nitrogen fixation (BNF) and salinity tolerance of five subterranean clover cultivars (Goss, York, Riverina, Denmark, and Golburn) was investigated using a factorial experiment in randomized complete blocks with three replicates. Salinity treatments were 0, 0.01, 0.02 m sodium chloride solutions. Sand culture with combination of Haugeland nutrient solution without nitrogen was used. Seedlings were harvested after 60 days and nodule number, leaf, root and shoot dry weights, leaf area, K+/Na+ ratio, nitrogen percentage and nitrogen yield were measured. Results showed that with increasing salinity, all the traits decrease, but specific leaf weight increases. Similar dry matter production was observed in saliniy treatments of 0 and 0.01 m sodium chloride. Mean comparison showed that cv. Goss is better than other cultivars with respect to nodule number, leaf area, dry weights, nitrogen percentage and nitrogen yield. Golburn was the worst. Highest and lowest decrease in K+/Na+ ratio was observed in Goss and Golburn, respectively. Calculation of sensitivity index showed that York and Golburn have the lowest tolerance to salinity. It seems that cv. Goss (with highest dry matter production) and York (with lowest sensitivity index) is promised for breeding efforts. A positive correlation was observed between all the traits and K+/Na+ ratio. It was concluded that regulation of K+/Na+ ratio is not the mechanism of salinity tolerance in cv. York.

A study was performed in 1997 on the experimental field of Faculty of Agriculture, Tabriz University, in order to study competition and find a model for intercropping of corn and soybean. The experiment was factorial based on randomized complete block design with 3 replications. Corn and soybean densities constituted the factors under study. In this experiment, the relationship of density with yield per plant and yield per meter square were obtained. The growth curve of corn responding to density was asymptotic but the curve for soybean felled at first by increasing density and finally became constant. Competitive models were also fitted by Spitters method. It was shown that inter-species competition of corn was greater than intra-species competition. In the basis of relative competitive ability of corn, the effect of one plant of corn on its reciprocal biological and grain yield was equal to the effect of 33.55 and 74.72 plants of soybean on the reciprocal biological and grain yield of corn. For soybean, each 0.122 and 0.0022 plants of corn had an effect equal to one plant of soybean reciprocal biological and grain yield of soybean, respectively.

In order to determine the cotton irrigation time based on soil moisture allowed depletion and the effect on cotton quantity of siokra and 818-312 varieties, an experiment was conducted in 1999 and 2000 in a silty clay loam soil in Hashemabad Cotton Research Station as split plot with completely randomized blocks comparing four treatments and three replications. Irrigation treatments were: Irrigation after depletion of 40%, 60% and 80% of soil available moisture during growing season in every irrigation and the other 40% depletion before flowering and 60% after flowering. The results showed that the effect of irrigation treatments were not significant on total yield and boll weight in every years, but on earliness was only significant in the first year. The highest yield was in siokra variety that 818-312 was increased 11.7% and 5.6% in two years, respectively and its difference was only significant in the first year. The results of complex analysis showed that there wasn't significant difference on totally yield of years but it was on earliness. Irrigation treatments were not different in view of yield and earliness. The higher yield in two years with 3592 kg/ha belong to siokra that increased 10.2% than 818-312 and 818-312 was the more earliness. Ultimately the best irrigation treatment in view of management and decreasing of irrigation numbers were 80% soil moisture allowed depletion and the best variety was siokra.

Functional response of Trichogramma pintoi that reared on Ephestia kuehniella and Sitotroga cerealella was studied to different densities of eggs of mentioned hosts. Two main parameters (searching efficiency and handling time) in two experiments were compared. The main purpose of this study was to determine the effect type of laboratory host (in size and quality) on one of the most important behavioral characteristics (functional response). The study of this behavior is an important method for assessing the efficiency of natural enemies. Parasitoid wasps were reared on two different hosts until 15th generation and then were used for experiments. Different egg densities that were used in both experiments were 2, 4, 6, 8, 14, 20, 30, 40 and 50. Each of these egg densities were inserted inside the test tube and then exposed to a mated female for 24 hours. Analysis of functional response was conducted on two stages by SAS software. At the first stage, logistic regression of proportion of estimated parasitized eggs was used for determining type of functional response. At the second stage, nonlinear regression was used for estimating searching efficiency and handling time parameters. In both experiments functional response was type III and Holling disc model was used to estimate the parameters. Searching efficiency, handling time, estimated maximum number and percent of parasitized eggs for parasitoids that reared on E. kuehniella were 0.0048, 0.965, 22.88 and 84.29, respectively and for them that reared on S. cerealella were 0.0016, 1.169, 16.92 and 44.03, respectively. The high rate of searching efficiency and low rate of handling time of parasitoids that reared on E. kuehniella indicates the high efficiency of these wasps in comparison with those reared on S. cerealella.

In 2000-2001, a faunistic survey on hover flies of Mashhad region was carried out. During this period, 24 species belong to 15 genera and 2 subfamilies were collected and identified. Among the specimens, 14 species as follow are new report for Khorasan province and those with asterisk are first report from Iran. Chrysotoxum intermedium*, Dasysyrphus albostriatus F., Enistalis tenax L., E. arbustorum L., E. taeniopsis Wied., Eristalinus aenus Scopoli Eupeodes nuba Wied., Ischioder aegyptius Wied., Myathropa florea L., Paragus haemorrhous* Meig, P. quadrifasciatus* Meig., Scaeva selenitica , Meig., Sphaerophoria rueppellii Wied., Syritta pipiens L. An identification key to the genera is given.

This study was carried out in two periods: 1377 and 1378. During two periods of this study in which Persian sturgeon juveniles were released, the results showed that those juveniles which selected the estuary for their living for a short period of two days, depending on the water salinity, they started to feed on the gammaridae and chiromidae a day after the released. The mentioned feed items are used as the main bait by these juveniles generally. At this time stomachs and guts of the juveniles have an average weight in the order of 4.30±1.70 and 6.90±4.90 mg approximately. The estimated condition factors of juveniles were 0.347±0.03. Stomachs and guts weights as well as the condition factors of the juveniles were higher at the beginning of the spring at the time of release than the end of the releasing period, and as closing to the end of the period the trend of decrease in weight was higher than the starting period. Considering the average water salinity that measured to be about 6.75±3.02 g/l, it seems that the time needed for juveniles to reach the sea from the point of their release, it takes about 6 hours or something near 3 hours per km. approximately.

In this study, heritability was estimated in black Karakul sheep by restricted maximum likelihood procedure from data collected in Sarakhs Sheep Breeding Station (Korasan province). Model I of DF REML software was fitted. Heritability of pelt score and birth, weaning, 6, 9 and 12 month weights were 0.19 (±0.05), 0.50 (±0.50), 0.53 (±0.07), 0.42(±0.09), 0.28(±0.08) and 0.36 (±0.09) respectively. Age of dam, sex of lamb, birth type (single and twin born) and year were fixed effects in the fitted animal model. Heritability in this research was high. Therefore, individual selection will be effective based on weaning and 12 month weights.

The aim of this study was to investigate the effect of induction of heat shock at early age to improve thermotolerance at advanced age in commercial broiler chickens. At the age of 1 day, 480 male broiler chickens (Arian breeds) were randomly distributed into four experimental groups (four treatments × six replicates) with 20 birds per replicates. The experiment was included four treatments; 1) an unexposed control group (T1); 2) chickens exposed to 38±1°C at age of 3 and 4 day for 48 h (T2); 3) chickens exposed to 38±1°C at age of 4 and 6 days for 48 h (T3); and 4) chickens exposed to 38±1°C at age of 3, 4 and 6 days for 72 h (T4). At 1week of age, the body weight gain of exposed chicks was significantly lower (p≤0.05) than unexposed control group while gradually in the following weeks compwastory growth were observed in T2, T3 and T4 groups. At the age of 42 days, the T2 and T4 groups showed significantly higher body weight gain and lower feed conversion rate than control group (p≤0.05) Abdominal fat pads as percentage of body weight were significantly (P≤0.05) lower in all previously exposed treatment groups than in control group. Exposure to high temperature (38±1°C) at day 42 for 4 h resulted in significantly lower mortality in the previously treatment groups than in the control group (P≤0.01). The result of the present study showed that an early age temperature conditioning resulted in a significant improved thermotolerance, final performance and survival rate in broiler during the heat stress at advanced ages. From the practical point of view, this may be used as an efficient method for broiler rising in hot climate regions.  

When surface-active chemicals of surfactants are used in low grade boiling, they tend to reduce the viscosity of last masseuites. By reducing the viscosity of massecuite, we expect to reduce the purity of molasses and produce better quality sugar. Sugar beet composition and quality changes during operation period can affect these beneficial effects. In this study, three different dosages (50, l00, 150 ppm) of two surfactants namely uranus CB9 and isopropylmyristate were added separately to the last massecuites of sugar factory. Then the effects of these surfactants on third boiling sugar color, sugar ash and purity of molasses were investigated and compared. The results showed that after using these agents, sugar color, sugar ash and molasses purity reduced but these effects were not similar in the first and the second half operation periods.

In preparation for pulp paper reinforced-HDPE composites, two types of paper pulp which named Neutral Sulfite Semi-Chemical (NSSC) and Chemical Mechanical pulp (CMP) were mixed with HDPE at four different levels of wt% of 10, 20, 25 and 30. Vinyl tri-ethoxy silane was used at 0, 1 and 2 wt% as coupling agent. The prepared composites were compared mechanically with samples made from HDPE matrix. Grafting of polymer with silane agent was studied using FT-IR and contact angle measurements. The results have shown that by increasing both types of paper pulps in composite, a reduction in elongation at break and an increase in elastic modulus are achieved. However, no significant change in tensile strength was observed when untreated HDPE was used as the matrix. Composites prepared from silane treated polymer show an increase in tensile strength. Compositions having 30% CMP fibers and 2% of coupling agent showed a higher tensile strength and elastic modulus in comparison with other systems. Compositions having 10% CMP fibers and 1% of silane coupling agent showed a higher impact strength when they were compared with other samples. The results have shown that compositions containing CMP fibers have better mechanical properties than ones having NSSC fibers.