فصلنامه دانش کشاورزی
سال هجدهم شماره 2 (پیاپی 70، تابستان 1387)

In this study, time variation of scour depth around bridge pier was investigated under clear water condition. It was revealed that more than 80% of the maximum scour depth took place at the first hour of the experiments and then the rate of the scour process decreased sharply. A new definition was introduced for equilibrium time of the scour depth and compared with previous works. The results showed that the previous definitions mostly gave smaller equilibrium time. There was agood agreement between equilibrium scour depth obtained at different conditions with other relationships. The empirical relationship was given to time variation of scour depth and comparison of this relationship with other's showed a good agreement.

In general, there are two sets of methods for flood routing calculations in rivers. These methods are classified as hydraulic and hydrologic scheme. Flood routing is of great importance to design, construct, and manage the flood preserved structures in order to study their effects on flood waves treatment in rivers, short time prediction of flood, prediction of river treatment after its situation changed and synthetic unit hydrograph generation are also accessible through flood routing. In this research, two approaches of flood routing i.e. Clark and Muskingum methods, were described and applied for a reach between Godarlandar and Gotvand gauging stations of Karoon river; then their functions were investigated and compared. Eleven input hydrographs in Godarlandar and their output hydrographs in Gotvand station were selected and the calibration of the study methods as well as their goodness of fit test performed through selected hydrographs using error analysis. The criteria used for models evaluation, included coefficient of determination (R2), standard error (SE), Nash- Sutcliffe efficiency (E), error in peak flow (QP%) and error in time to peak (TP%). The results showed that both Clark and Muskingum methods under estimated the peak and the time to peak as compared with the observed values whereas the result of evaluations showed that the simulation of output hydrographs with Muskingum method was closer to observed than that of Clark method.

Oilseed rape plants having 6-8 leaves, 8 milimeter of rosette diameter and 1.5 gram of plant dry weight, show better tolerance against winter cold. The effects of planting date on winter survival and seed and oil yield of oilseed rape, are very important. The purposes of this study were to determine suitable plant phenotype for better cold tolerance at winter and evaluate oil and seed yield and its components in superior winter oilseed rape genotypes. The experiment was conducted as factorial based on randomized complete block design with three replications. Factors were 1) planting date including normal (6 sept) and late (26 sept) planting dates and 2) genotype including six supeior winter oilseed rape genotypes. The experiment was carried out in Agricultural Research and Natural Resources Center of East Azarbaijan (46°C and 2″E, 37° and 58″ N) during 2003-4. The results indicated that the genotypes at the planting date of 26 sept had lesser leaves, rosette diameter and dry weight as compared with the planting date of 6 sept, when the mean air temperature reached below oilseed rape base temperature (5°C). The value of these characters at late planting were 3.8, 3.7mm and 0.58g, respectively, and at normal planting were 7, 5.9 mm and 2.4g, respectively. As the genotypes at late planting date did not have suitable rosette form during winter, indicated the frost damage was 19.7% compared with the normal planting date having the frost mortality of 8.4%. Grain and oil yield of genotypes in the late planting date (3775.5 and 1733.2 kg/ha seed and oil yield, respectively) were less than that of the normal planting date (4432.2 and 2058.3 kg/ha seed and oil yield, respectively) due to more cold stress condition. It seems that the genotypes under investigation, specially SL 046 and Okapi are suitable for winter planting in the studied area. Leaf number, rosette diameter and dry weight of oilseed rape plants, measured when the mean air temperature reaches below the base temperature, can be used to select for cold tolerant oilseed rape genotypes and determine suitable planting date.

In order to compare heat indices at various phonological stages of corn affected by different levels of densities and interference periods of sorghum, a factorial experiment was conducted on the basis of randomized complete block design with three replications in the growing season of 2002 at the Research Station of the Faculty of Agriculture, University of Tabriz, Iran. Studied factors consisted of different interference periods of sorghum (0, 14, 28, 42 days after corn emergence), and sorghum densities of 4, 8, and 12 plant/m2. Corn density was 7.8 plant/m2. Results showed that the best thermal indicator was the classical index to evaluate the effects of density levels and various interference periods of sorghum on corn phonological stages in Tabriz area. This index had the highest correlation with the grain yield at all corn phonological stages such as tasseling, silking and physiological maturity. Also, when winter crops were planted after corn harvesting or ripening or seed filling duration, it can be recommend to use general thermal heat index. If the aim of artifical pollination is to produce hybrid genotypes. Three indices of growth degree day, crop heat unit and heat unit can be used due to their similar results. Finally, if the aim is to determine the silking, it would be better to use crop heat unit or heat unit.

The allelopathic effects of Amaranthus retroflexus L., Setaria viridis L., Acroptilon repens L., Chenopodium album L., Cirsium arvense L. Cynodon dactylon L., and Convolvulus arvensis L. in three allelopathic environments including shoots powder, roots powder, and rhizosphere soil of weeds, in three stages of vegetative, reproductive and maturity, on germination, lengths and weights of seedling, radicle and plumule of soybean (CV. Williams) was studied at the laboratory. For this purpose, a factorial experiment based on randomized complete block design with four replications was used. The results showed that the allelopathic materials of all weeds and all allelopathic environments had significant effects on all traits as compared to the control. But growth stage had only significant effect on germination percentage. A. retroflexus and C. arvense had the largest inhibitory effects on seedling growth, but, C. arvensis had largest inhibitory effects on germination percentage. Plumule growth was influenced more than radicle growth. Allelopathic factors at all growth stages of weeds had large amount of inhibitory effect on germination and seedling growth of soybean. The result of this study could be useful to recognize allelopathic effect of important weeds on decreasing germination and seedling growth of soybean.

Drought stress is one of the most important environmental factors which reduce growth, development and production of plants. In order to investigate the effects of drought stress on seed germination of sugar beet, a factorial experimental was conducted based on randomized complete block design (CRD) with three replications. The experimental factors were five sugar beet cultivars (IC, H5505, PP8,7233, BR1) and five levels of water stress (0,-2,-4,-6,-8 bar of polyethylene glycol 6000). The results showed that decreasing osmotic potential had a significant effects on germination, speed and uniformity of germination. Increasing osmotic potential decreased germination percentage, its amount was 8633% in the control treatment and 11% in the osmotic potential -8 bar. The highest germination percentage was belonged to cultivar7233 629%) and the lowes amount was in cultivar H5505 (4266%). Maximum uniformity of germination was obtained in the control treatment and the minimum amount was obtained in the osmotic potential 6 and -8 bar. Minimum uniformity of germination was obtained in the cultivar IC (with 53.47 hours) and the maximum uniformity belonged to the PP22 cultivar (with 36.21 hours). The higher levels of osmotic potential had more inhibition effect on plumule growth than on radical growth. Under water stress condition cultivar 7233 had longer radicle and higher proportion of radicle to plumule than other cultivars. Thus this cultivar was more resistant to water stress.

In order to study the influence of redroot pigweed interference with sunflower, Allstar RM hybrid, an experiment was carried out at research station of Islamic Azad University of Tabriz in 2004, with three different densities of 5, 15 and 25 plants per meter of row and three interference times of emerging with sunflower, 15 and 30 days after sunflower emergence in a distance of 15 cm from both side of the sunflower rows. The experiment was established as a factorial based on randomized complete block design. Analysis of variance indicated that stem height at the ripening stage, antodium diameter, seed number in each antodium, hollow seed percentage, 1000 kernels weight, grain yield, seed oil percentage and oil yield were affected by density and interference time of redroot pigweed. Interaction of density×interference time on stem height at the ripening stage, 1000 seeds weight, grain yield, seed oil percentage and oil yield were significant. The lowest and highest hollow seed percentage obtained from density of 5 plants per meter of row at 30 days after sunflower emergence and full season interference of 25 plants per meter of row, respectively. The highest seed number in each antodium was obtained in the second level of density. The highest 1000 seeds weight and grain yield observed from density of 5 plants m-1 of row and interference time of 30 days after sunflower emergence. Seed oil percentage in all treatments except density of 5 plants per meter of row and interference time of 30 days after sunflower emergence had significant difference in comparison with the control. It seems that, weed plant number has higher effect than weed interference time on seed oil percentage. This research showed that in studied cultivar, with the short height, lower leaf area and lower competition ability with redroot pigweed, yield loss is affected more by density than interference time.

Low temperature is one of the most important abiotic stresses which decrease the production and the yield of crops. It is important to identify the nature of genetic control for breeding of cold tolerance. In order to estimate the genetic parameters related to cold tolerance in bread wheat, seven cultivars, namely: Norstar, Capplle-Desprez, Morgan, Desconsoide, Sardari, Kohdasht and Zagros along with their 21 half diallel hybrids were evaluated under controled conditions in freezing temperatures and survival percentage and LT50 of genotypes in each temperature was recorded. Analysis of variance showed significant difference among genotypes. Therefore, diallel analysis was performed based on Griffing’s mixed model B of method II. Genetic analysis revealed significant general combining ability for plant survival percentage whereas specific combining ability was not significant. This indicated the role of additive the effects in control of cold tolerance. The high narrow heritability (87.08) and low degree of dominance (0.28) also showedthe small contribution of dominance effects in controlling this trait. Among parental genotypes, Norstar showed the highest general combining ability (0.402) and also maximum mean for survival percentage (88.2).

Tenderness is one of the important characteristics of meat and desired to consumers. Calpastatin is one of the genes which affects meat quality and growth of the animals. The aim of this study was to determine genotypic variation of calpastatin gene in Iranian Moghani sheep breed using PCRRFLP. For conducting this study, the blood samples of 176 sheep were collected. After extraction of genomic DNA, the L region of exon 1 of calpastatin gene with 622 bp was amplified with specific primers. The MspI and NcoI restriction enzymes were used to cut the PCR products. The mentioned enzymes cut the amplicons in complementary manner and alleles of M and N with frequency of 0.54 and 0.46, respectively were produced. Genetic variation (heterozygosity) in the Moghani sheep breed was moderate (0.49) and the population was in Hardy-Weinberg equilibrium. The results confirmed that the PCR-RFLP can be used to identify different genotypic variation in this breed.

This experiment was conducted to evaluate the effects of microbial phytase and dietary calcium levels on performance, tibia ash percentage and some blood factors in male broiler chickens. Three hundred sixty male broiler chickens from Arbor Acres plus (AA+) strain were used in a completely randomized design as a 2×3 factorial with five replicates and 12 chickens in each floor pen. Broiler chickens were fed two levels of dietary calcium (NRC recommended level and 80% of it) and three levels of microbial phytase (0, 300, and 600 FTU/kg of diet) during 7-42 days of age. Experimental diets were formulated to be isoenergetic and isonitrogenous with similar nutrients with the exception of calcium and total phosphorus. During the experiment, body weight, body weight gain, feed consumption and feed conversion ratio were measured weekly. Tibia ash percentage and blood serum factors were measured on 28 days of age. Mortality rate was recorded daily through the experiment. Low dietary calcium level had no significant effect on body weight, daily weight gain, feed intake, feed conversion ratio, serum calcium concentration and tibia ash percentage, while phosphorus concentration of blood serum decreased and activity of serum alkaline phosphatase increased (p<0.05). Phytase level, significantly improved body weight, daily weight gain, feed conversion ratio, tibia ash percentage and serum phosphorus concentration (p<0.05). Serum alkaline phosphatase activity was decreased by phytase level (p<0.05). Phytase had no significant effect on feed intake and serum calcium concentration. There was no significant difference between the effects of 300 and 600 FTU on the performance of broiler chickens.

The objective of this study was to investigate the effect of some factors on postpartum anoestrus in dairy cows. Anoestrus cows were divided in four groups as inactive ovary, persistent follicle, persistent corpus luteum and ovarian cyst. Blood samples were obtained from 182 lactating cows and serum glucose, urea, total protein, phosphorus and β-hydoxybutyrate were measured by spectrophotometer and blood serum progesterone concentration was measured by ELISA method. Some impressive factors on postpartum anoestrus including calving season, parity, body condition score and milk production were also studied. Effects of calving season, blood serum total protein (P<0.05) and blood serum glucose (P<0.0001) were significant on animal status. The cows calving in warm season were willing to stay in persistent corpus luteum status. The results showed that with increasing serum glucose, cows trended to return normal status. While with increasing of serum total protein, cows trend to stay in persistent follicle status. As a whole, some biochemical and hormonal factors may play an important role in postpartum anoestrus.

Crosses among 10 homokaryotic isolates of Agaricus bisporus (parents) resulted in 45 offsprings. To measure some traits such as yield, ratio of cap length to stipe height, weight of single fruit body and total number of fruit bodies, a fruiting test was performed in a randomized complete block design with two replications. General and Specific combining ability (GCA and SCA) effects were calculated for each trait, according to the Griffing΄s method 4. The results showed that both GCA and SCA were significant for all traits. While genes action in relation to the ratio of cap length to stipe height and weight of single fruit body was both additive and non-additive, it was only additive in other traits. In accordance with the role in which additive effects play in governing the traits, it was found that the isolates 130-48 and 130-52 could be appropriate sources for increasing yield and the total number of fruit bodies, while the isolates 130-52 and A15-5 could be applied in order to increase weight of single fruit body and ratio of cap length to stipe height, respectively.

First cut of alfalfa crops with more than five years old is not economic for to produce forage production, but they are suitable for seed production. At the present alfalfa seed is produced from the second and third cuts of alfalfa crops with more than five years old, having high population of plant bugs, Lygus spp. and Adelphocoris lineolatos (Goeze). They cause flower shattering in seed production fields and unfortunately the damage is very high and seed production is not economically feasibl. Therefore, if alfalfa weevil, Hypera postica (Gyl.) and weeds can be controlled, then a suitable seed may be produced. In this regard, seven different integrated control methods of pests and weeds at first cuts of alfalfa crop were used. The treatments were including A) physical control (field blaming on 1st April), B) chemical control in early spring (1st April) + spraying at green buds stage to control Lygus bugs (spraying with insecticide), C) chemical control with herbicide (using the Gramaxone on 1st April to control weeds and destroying plant debris that contained over wintering eggs), D) applying herbicide (on 1st April) + using the insecticide in the green bud stage, E) early cutting (when alfalfa height was five cm) + using insecticide in the green buds stage, F. physical control (field blaming on st April + using the insecticide in the green bud stage, G. using the Gramaxone on 1st April + the insecticide in the green bud stage and H) control treatment. The experiment was carried out as random complete block design with four replications during 2006. Most of the control methods were effective in controlling pests of first cut in contrast to the control and the differences were significant in 1% probability level. Treatments F, E and G were more effective than other treatments in controlling major pests. Consequently, a proper alfalfa seed with higher yield can be produced from the first cuting of lucerne crops with more than five years of age. By bud stage controlling the alfalfa weevil and weeds, and spraying on Lygus bugs, in the green. In this condition a seed yield of about 370 grams per meter square (equal to 3700 kg per hectare), can be produced.

Morphological and biological studies of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) were conducted on Gossypium hirsutum at 24 ± 20C, 75±5% RH, and 14 h photoperiod. B. argentifolii has eight distinguishable life stages including egg, four nymphal instars, pre-pupa, pupa, and adult which were studied morphologically and suitable figures were drawn. The mean developmental period from egg to adult eclusion was determined 24.86±6.78 days, and separately was 6.21±2.06, 3.85±1.67, 3.24±0.87, 2.91±0.52, 2.68±0.35, 2.03±0.17, and 3.94±1.14 days from egg to pupa, respectively. Male and female longevity was 20.8±7.3 and 26.4±5.6 days, respectively. The number of egg deposited was not uniform throughout the female life, and the maximum number was observed at 8th and 9th days of the life and then decreased to zero. Unmated females produced male offsprings; therefore, B. argentifolii is an arrhenotokous parthenogenetic. Nearly 24 hours is necessary for maturity of emerged adults.

During the past few years, some investigations have been conducted at agricultural research centers and universities regarding the design or selection of suitable planters for sowing small seeds. Examination of different vacuum planters in Iran showed that the problem is the seed metering mechanism. Therefore, the main objective of the present research was the improvement of the existing vacuum-precision planters. A pneumatic seed knockout device was fabricated for these planters to improve them for sowing of the small seeds such as rapeseed. The new pneumatic seed knockout system was mounted for testing on the seed metering system of the vacuum precision planter made by Behkesht (Agrifarm) company. The objective of this test was the determination of pneumatic seed knockout effect on planter performance. Independent variables were: rotational velocity of seed plate at three levels (40, 68 and 99 rpm) and air velocity of the pneumatic seed knockout device at three levels (0, 7-8 and 15-16 m/s). Dependent or measured variables included: three types of seed damages, cell filling percentage, and seed viability. Result of the analysis of variance indicated that metering plate velocity had a significant effect on percent cell filling. Increasing the rotational velocity, results in a significant decrease in percent cell filling. Air velocity had a significant effect on mechanical damage in the form of seed splitting and breakages as well as in the form of seed coat scratching and moving and on the sum of these values. All types of mechanical damage decreased, as air velocity increased. None of the independent variables had a significant effect on seed viability.The interaction of rotational velocity and air velacity was hot significant. Test results indicated that not only the pneumatic seed knockout device decreased seed damage, but due to clearing the seed metering plate cells clogged by brocken seeds and plant debris, it increased the cell filling percentage and improved overall performance of the seed metering systems.

This research was performed on the basis of a field experiment to evaluate the effects of puddling in machine slipping with three treatments and four replications. In order to determine proper transplanting, the variables such as planting depth, number of pigweeds in hill drop, row distance, hill drop distance, number of total lost hill drops and actual field capacity in one, two, and three times of puddling were measured. The seed of Belpanta variety of rice was for field tillage, the tiller (Kubota- KRA- 75) with 1.35 m work width, 7.5 hp was used. The riding type transplanter machine (Yanmar-pr-400) had 4 rows with 30 cm distance between rows. Treatment means were compared by Duncan’s multiple range test. The results indicated that the number of puddlings increases slipping. There was no significant differences between five and three times of puddlings but the difference between three and one times puddlings was significant. One time of puddling was regarded the best conditions on the basis of transplanter performance but for weed burial three times of puddling was suggested. More than three times of pudding was not recommended because of technical and economical reasons.