نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال هشتم شماره 4 (پیاپی 30، زمستان 1383)

The influence of the Sea Surface Temperatures (SSTs) on the seasonal precipitation over northern and southwestern parts of Iran was investigated. The warm, cold and base phases of the SSTs were defined and the median of precipitation during each of these phases (Rw, Rc and Rb, respectively) was determined. The magnitude of Rw/Rb, Rc/Rb and Rc/Rw were used as criteria for the assessment of the effects of the alternation of SST phases on seasonal precipitation. The results indicate that in association with cold SST phase, winter rainfall is above median over western and central parts of the coastal region, central and southern parts of Fars Province and all the stations studied in Khozestan Province. On the other hand, the prevalence of warm SST phase has caused about 20% decrease in winter precipitation over the Caspian Sea coastal area and northern parts of both Fars and Khozestan provinces. In association with warm SST phase in winter, precipitation during the following spring was found to be above normal for all the stations studied in the coastal region of the Caspian Sea. The highest sensitivity levels were found in Bandar- Anzali and Astara for which spring precipitation has increased by 80% due to the dominance of warm winter phase. However, the occurrence of boreal cold SST events causes shortage of precipitation in the eastern parts of the coastal areas along the Caspian Sea. A Possible Physical mechanisem justifying the influence of the Caspian Sea SST on the Precipitation variability was introduced. According to this mechanisem, temporal and spatial variability of the Siberian High is forced by the fluctuations in these SSTs.

Today, privatization of agricultural extension services is recognized as an appropriate approach to compensate for any weakness that the traditional extension system might have. The primary objective of this research was to study the attitude of the national top managers (including general managers, their deputies, and extension managers) of Jihad-e Keshavarzi Organizations (JKO), toward privatization of agricultural extension. Twenty JKOs from 20 provinces were randomly selected for study. A questionnaire was developed to the gather information needed and 107 general managers, deputies, and extension managers were randomly selected for this purpose. A pilot test was conducted on a similar population and reliability coefficients of (A Cronbach Alpha) 81%, and 89% were obtained for the attitude and managerial characteristics of the questionnaire respectively. The results showed that 93.83% of the subjects had either “positive” or “relatively positive” attitude toward privatization of agricultural extension. The majority of the subjects indicated that privatization of extension could provide a “supplementary means to complement the existing public extension services”. A hierarchical regression analysis indicated that the independent variables collectively are responsible for 17.4% (R2 =0.174) of the variation in dependent variables. This indicates that a considerable amount of variances in dependent variables are yet unaccounted for that could be explained by variables that were not investigated in this study (requiring further study).

Proline as a key osmoregulating solute in plants plays an overriding role in osmotic pressure adjustment of the cell under water stress conditions. In plant, a bifunctional enzyme delta-1-pyrroline-5-carboxylate synthetase (p5cs) promotes and directs proline synthesis during drought stress conditions. The activity of this enzyme is strongly induced to increase proline concentration within the cell to prevent the impact of water deficit. In this study, the sequence coded for p5cs enzyme under the control of the cauliflower mosaic virus 35S promoter was cloned into a plasmid containing gus and nptII genes. The construct pBI121-p5cs was then transferred into Agrobacterium tumefaciens C58 (pGV3101) and used for producing transgenic tobacco(Nicotiana tabacum cv. Xanthi) plants. The amplification of a 765 bp band within p5cs gene from transferred plants and forming deep blue color in leaf tissues of the explants indicated the successful introduction of p5cs construct into nuclear genome of tobacco plants through Agrobacterium-mediated transformation. The two-month old plants growing under normal condition besides the five-day seedlings under drought stress were subjected to determination of proline concentration. Comparison of P5cs product levels between control and water tolerated plants indicated an increase of proline of about 96.91 to 1330.891 mg/g and of 204.454 to 2039.77 mg/g in plants under normal irrigation and under drought stress, conditions respectively. The significant difference between the levels of proline product in control and transgenic plants under different growing conditions demonstrated the expression of targeted gene (p5cs) in engineered tobacco plants that may pave the way to overcome the water stress problem in agronomically useful crops.

Formation of the two- and six-rowed types in barley is predominantly controlled by alleles at a single locus (vrs1) which is located in long arm of chromosome 2H. This gene is a key character on the study of barley domestication and yield. Near-isogenic lines (NILs) of barley were produced from crosses between Kanto Nakate Gold (tow-rowed) and Azumamugi (six-rowed). The selected lines were used for screening of AFLP polymorphic bands which are linked to vrs1 locus. After screening of a total of 1792 primer combination, five polymorphic bands were identified. A construction of high resolution map around the vrs1 locus was made using recombinant inbred lines. These markers can be used for a map-based cloning of the genes at the vrs1 locus.

Lintz-Donawitz (LD) converter slag, a by-product of the iron and steel-making industry is produced in large quantities in Isfahan, Iran. The slag contains 52.8 and 2.2% (w/w) CaO and MgO, respectively. To determine the influence of LD slag on the chemical characteristics of three acid soils from Gilan, an incubation study was conducted. The soil samples were collected from 0-30 cm of rice and tobacco fields and a tea garden. Treatments were 0, 0.5, 1, 2, 4, 8 and 16 % (w/w) of converter slag/kg soil. The slag was thoroughly mixed with 500g soil in plastic pots. Soil moisture content was adjusted to near field capacity and changes in pH, EC and AB-DTPA-extractable Fe, Mn, Zn, P and K were determined at 1, 10, 30 and 60 days. Results showed that soil pH increased with increasing slag rates. Slag increased AB-DTPA-extractable P and Mn, the magnitude increase depend on the amount of slag applied. However, the effect of slag on AB-DTPA-extractable Fe depended on initial pH, initially decreasing at the pH range of 7.4 - 8.5 and then increasing at higher pH levels. Slag decreased AB-DTPA-extractable K especially in highly acid soil. In the present study, soil pH and AB-DTPA-extractable Fe decreased with time, though the effect of incubation time on pH was not significant. The effect of incubation time on AB-DTPA extractable Mn and P was different. Time effect on EC and AB-DTPA-extractable K was not significant. In general, soil chemical characteristics were more affected by slag rates than by incubation time. In conclusion, it seems that converter slag is a suitable amendment for acid soils. It is suggested that the effect of LD converter slag on plant growth and chemical characteristics of acid soils be studied under field conditions.

Peat is the best known and the most widely used rhizobial carrier, but unfortunately, it lacks of sufficient sources in Iran. This research aimed at using some inexpensive materials as carrier instead of peat for producing the rhizobial inoculant for alfalfa. For this purpose, the physical and chemical properties of some materials to be used as carriers were determined and the viability of Sinorhizobium meliloti on these carriers during 6 months at +4 ºC was evaluated. The selected carriers were 1) Peat (control) 2) Vermicompost 3) Bilogical Filter Waste (BFW) 4) Vermiculite+Vermicompost (1:1w/w), and 5) Vermiculite+BFW (1:1w/w). Also to determine the suitable moisture content of carriers on prolongation of bacterial survival, two matric potential levels including –10 and –30 kpa were applied on the carriers. The results showed that vermiculite+BFW (1:1w/w) not only maintained a standard number of bacteria compared to the other treatment, but also caused good nodulation on alfalf seedling at the end of the 6th month. Although BFW carrier maintained a high number of bacteria after six months storage, it can not be recommended as a suitable carrier because of its negative effect on nodulation. In this study, higher number of bacteria was maintained in the matric potential of –30 kpa than –10kpa.

In order to investigate variations of spore population, root colonization and also to determine mycorrhizal symbiosis in the root and rhizosphere of Pistachio trees (Pistacia vera) in natural forests, two study stations in Kalat (Chachaeh) and Sarakhs (Shorlogh) regions were selected. Sampling from soil and root of the trees were taken from under the canopy and from a depth of 30 cm. On a monthly basis. The roots were stained and the colonization rate and the variations of spore population were measured. Some soil characteristics including pH, moisture, organic material percentage and available phosphorus were determined, The correlation coefficients between the measured factors were calculated. The results indicated that vesicular – arbuscular mycorrhiza (VAM) was the only symbiotic mycorriza of pistachio trees. Average amounts of root colonization were 13% and 11% in Chahchaheh and Shorlogh stations, respectively. Also, average numbers of spores per 1 gram of dry soil in the above stations were 12 and 10, respectively. The correlation between the variation of spore population and colonization levels was positive but the correlation between spore population and soil moisture, organic material, available phosphorus and pH was negative.

In order to find the high-yielding and adaptable cultivars in different environments, eight cotton genotypes including two early maturity hybrids were studied and compared with the Varamin cultivar as control in a randomized complete block design with four replications in six regions in 1997 and 1998. Using Barttlet test, some of the environments were eliminated from statistical analysis. Therefore, combined analysis of variance and other statistical calculations were carried out based on environment (Year×Location) on the assumption that environment was randomized and cultivars remained constant during the entire study. In combined analysis of variance, genotypic effect (in yield) was significant at 1% probability level. Combined analysis of variance also showed significant differences for the main effect of environment and genotype×environment intreaction at 1% probability level. To select the best genotype with a high and stable yield, parametric statistics of stability including type 1 stability (S2i,CVi), type II stability (bi,σi2, w2i), type III stability (Sd2i) as well as non-parametric statistics such as mean of genotypic rank (R), standard deviation of rank (SDR), and simultaneous selection of parametric and nonparametric statistics for yield and stability (Ysi) were calculated. Overall, considering the important agronomic and technological characteristics of genotypes such as yield, earliness, span length, fiber strength, percentage of uniformity, and micronariae index, the hybrid Coker×Bulgar was selected as high-yielding and stable cultivar to be substituted for Varamin cultivar across the planting area.

Digestible lysine and sulfur amino acid (SAA) requirements of Ross male broilers were determined during the starter period in two experiments. Broilers were fed a control corn-soy diet (3200 kcal MEn/kg and 23% CP) for 6 days and then randomly assigned to dietary treatments until 16 days of age. The basal diet containing 19% CP was prepared in order to be deficient in lysine for experiment 1 and SAA for experiment 2. Seven graded increment levels of L-lysine HCl or Dl-methionine were added in absences of starch in experiment 1 and 2, respectively. All diets contained 3200 kcal MEn/kg and all essential amino acids, except for the test amino acid, were 10% higher than the NRC (1991) recommendations. The digestible lysine requirements of broilers based on broken-line and exponential models were 1.04 and 1.01%, respectively. The digestible SAA requirements for the mentioned models were 0.846 and 0.841%, respectively.

Two hundred Arian broiler chicks were used to investigate the effect of contents of dietary glucosinolates on performance of broiler chicks during starter (0-21 days of age) and grower periods (22-42 days of age) in a completely randomized design. The dietary glucosinolates contents in the starter period were 0 (S1), 7.5 (S2), 15 (S3), 22.5 (S4), 30 (S5) µmol/g and in the grower period they were 0 (G1), 5.7 (G2), 11.4 (G3), 17.1 (G4), 22.8 (G5) µmol/g. Feed intake during the grower period was affected (P<0.05) by different levels of glucosinolates in the diets and the lowest feed intake was observed in the G5 treatment. The lowest body weight gains were observed in the S5 and G5 treatments during the starter and grower periods, respectively (P<0.05). The feed conversion ratio (FCR) in the S5 treatment for the starter and the G5 treatment for the grower period were significantly different (P<0.05) from other treatments. The correlation between the body weight gain and level of dietary glucosinolates or glucosinolate consumption was high during the starter (r = -95.3% and -94.7%, respectively) and relatively high (r = -69.5% and -72.4%, respectively) during the grower period. This experiment showed that the amount of glucosinolates in the diets of broiler chicks for the periods of starter and grower feeding system should not be more than 11.36 and 8.11µmol/g diet, respectively. Also during the starter and grower feeding periods, the highest level of rapeseed meal could be used in the broiler diets are 13 and 8 percent, respectively.

In order to determine the effects of fetal growth rate on plasma concentrations of glucose, triglyceride, total protein, and urea in ewes, this experiment was conducted at Animal Research Station of Tehran University Agricultural College. Sixteen pregnant Varamini ewes were allocated to 4 groups (n=4). During the breeding season, ewes of group 1 were mated by Varamini ram, animals in groups 2, 3 and 4 were mated by Moghani, Afshari and Shall rams, respectively. Because of the different genetic capacities of sires, fetal growth rate was expected to be different in various groups. Ewes in all groups were fed the same ration, so it was expected that differences in fetal growth rates would affect the mobilization of maternal fat and protein storage and blood levels of their metabolites. Blood samples were collected from jugular veins of ewes during the last 8 weeks of pregnancy and first week after lambing. Plasma levels of glucose, cholestrol, and triglycerid were not different among 4 groups. Total plasma protein in ewes carrying heavier fetuses was lower than in ewes with lighter fetuses (p<0.05). Conversely, plasma urea concentrations in ewes with heavier fetuses were higher than in ewes with lighter fetuses.

In order to investigate the effect of phytase and copper supplementaion on growth and carcass composition of common carp (Cyprinus carpio L.), in a completely randomized design with 3 ×2 factorial arrangement with three replicates the experimental diets including three levels of phytase 0, 500 and 1000 (FYT) kg-1 and two levels of copper 0 and 15 mg/kg were tested. Diets contained 0.72 percent total phosphorus. One hundred and forty four carps with a mean weight of 207±23 g were selected and allocated in eighteen cages (8 fish per cage). The experiment was carried out for 8 weeks and 2 weeks for acclimatization. Phytase supplementation caused no significant differences in weight gain (WG), feed conversion ratio (FCR), carcass index (CI), protein efficiency ratio (PER), liver, carcass and blood composition but increased apparent phosphorous digestibility (APD) significantly (P<0.04). Copper supplementation also caused no significant differences in WG, FCR, CI, PER, APD, liver copper, carcass composition, cholesterol (Ch), triglycride (TG), phosphorus of serum but decreased liver fat significantly (P<0.004) and increased high density lipoprotein (HDL) of serum (P<0.02). Interactions between phytase and copper on WG (P<0.01), FCR (P<0.04), PER (P<0.03), liver copper (P<0.02) and TG of serum (P<0.001) were significant. This experiment suggests the presence of antagonistic effect between phytase and supplemental copper. Phytase enzyme improved some parameters of growth and carcass composition of common carp without supplemental copper but addition of copper to the diets with phytase enzyme impaired the improved performance of carp.

Aqueous extraction of gum from flaxseed was optimized using Response Surface Methodology (RSM). In this study the effect of temperature (45-100 °C), pH (3-7) and water/seed ratio (4-24), on the dependent variables including: yield, protein and apparent viscosity of extracted gum were investigated. The results showed that temperature and pH are two major effective factors on yield and quality of extracted gum (purity and apparent viscosity), whereas water/seed ratio had minor effects. The optimized conditions of extraction were as follows: temperature 85- 90 oC pH 6.5- 7.0 and water/seed ratio 14. Apparent viscosities of extracted gums were determined and the effect of extraction conditions on rheological properties of flaxseed gum was investigated.

The egg parasitoids are the major natural enemies of sunn pest and application of selective insecticides is one of the strategies for conservation of natural enemies. The toxicity of five different insecticides used in cereal fields to the parasitized eggs was investigated under laboratory conditions. The insecticide solutions were made based on the recommended field rates. 3-, 5- and 8- day -old parasitized eggs were dipped into insecticide solutions. Among the treated developmental stages (except for the fenirothion), 3- and 8- day- old parasitized eggs showed the highest and the lowest emergence percentages, respectively. Deltamethrin had maximum effect on emergence percentage whereas phosalone had the least hazardous effects. There was a significant difference in parasitism percentage between 3- and 8- day- old parasitized eggs in each of the 4 treatments, viz trichlorphon, fenitrothion, deltamethrin and esfenvalerate. Adults emerging from 3- day- old eggs parasitised less eggs than those emerged from 8- day- old eggs in fenitrothion, and trichlorphon treatments. All tested insecticides were highly toxic to the adult parasitoid, causing 100% mortality when the adults were exposed to sprayed areas at recommended rates.

Elm leaf beetle were reared under controlled conditions (25± 2 oC, 70± 5%R.H. and 16L: 8D) to determine relationship between biological traits and the number of eggs per female on different hosts and to evaluate correlation between traits. U. carpinifolia, U .c. var. umbraculifera, U. glabra var. pendula and Celtis caucasica were examined as hosts. The biological traits consisted of 1st, 2nd and 3rd larval developmental times first, second, and third larval percent mortality rates prepupal and pupal developmental times male and female longevity and pre-ovipositional period recorded during experiments. The relationships between traits and the number of eggs per female were determined by multiple regression (Foreward selection and stepwise). The correlation between traits was evaluated, too. The results showed that the number of eggs per female were mostly affected by certain special traits such as 2nd and 3rd larval developmental time, pre-ovipositional period and male longevity which are distinct in different hosts and seasons.

Four different species of aphids belonging to the Aphididae family in four genera were collected and identified in Rape-seed fields in Sistan region during 2000-2001. Among them, Brevicoryne brassicae (Cabbage aphid) was the dominant species with an abundance of about 89% in area. The population fluctuation of Brevicoryne brassicae was studied simultaneously on fields in Sistan region (Zahak research station and her around fields). The research was conducted on a half hectare of each farm. Thirty leaves from each field at week intervals were randomly picked up and the aphids were collected and identified at the species level. The Brevicoryne brassicae had a peak of activity in early mid March to April at temperature and R.H. ranging between 22-28ºC and 45-65 R.H., respectively. Controlled conditions indicated that the Brevicoryne brassicae has a life cycle of 6-7 days and adult female longevity is 20-31 days (25±2 ºC and 75±5 R.H.). Rearing study also revealed that this species has the ability to reproduce up to 18-98 nymphs under laboratory conditions and an apterous female gives birth to 22-93 nymphs in her life time. Samplings for recognition of predators and parasitoids were also taken at 3-day intervals. Natural enemies in fields during the two years were identified to be 5 coccinellid (Col:Coccinellidae), 4 syrphid(Dip:Syrphidae) and 2 chrysopid species (Neu:Chrysopidae). Also in Hymenoptera, 2 parasitoids (Hym: Aphidiidae & Pteromalidae) were determined.

The effect of Bacillus thuringiensis var. kurstaki on different larval instars of Colorado potato beetle, Leptinotarsa decemlineata (Say) and the role of two plant materials, namely, caffeine and aqueous neem extract, in the enhancement of it’s efficiency was investigated under laboratory conditions. The experiments were conducted at 25±4 oC, 65±5 %(RH) and photoperiod of 16:8 (L:D).The larvae were provided from the colony established and maintained on host plant. The different larval instars were distinguished by measuring head capsule width.To evaluate susceptibility of different instar groups of larvae to B.thuringiensis, LC50 values on (1-4) instar groups were determined. LC50 values for 1st, 2nd, 3rd and 4th instar groups were, 183.86, 377.03 ,1297 and 3096 ppm, respectively. The synergistic effect of caffeine and aqueous neem extract with B.thuringiensis was investigated separately on 3rd larvae instar. A completely randomized design with 6 treatments and 4 replications was used. The results revealed that there was a striking synergistic effect of caffeine and neem on B.thuringiensis.The larval mortality percentage for mixture 618ppm of B.thuringiensis and 4000ppm of caffeine was 80% however, this was 10% and 20% for caffeine B. thuringiensis respectively when these compounds were used alone.The initiation of larval mortalitry in all mixtures was earlier than other treatments.Also the larval mortality for mixture B. thuringiensis with 35000 ppm of aqueous neem extract was 77.5% after 144 hours however, it was 22.5 % and 25 % for B.t. and neem alone, respectively. The mean weight of larvae treated with all synergists was significantly less than the control cohort, (p<0.05).

Representatives of fluorescent pseudomonad strains were assessed for their antagonistic activity against the blackleg of potato pathogen, Pectobacterium carotovorum subsp. atrosepticum. Tested strains belonged mainly to Pseudomonas fluorescens Biovars III, IV and V and they could produce inhibition zone on PDA medium against P. c. subsp. atrosepticum ranging from 1.5-5.5cm. Six selected strains were used in two concentrations 107-109 and 1010-1012 colony forming units to control potato blackleg disease caused by P. c. subsp. atrosepticum under greenhouse conditions. Results showed that all strains applied could reduce the disease ranging from 46 to 71 percent. There was no significant difference among strains and their two concentrations under greenhouse conditions. Most of the strains applied increased potato fresh weight and all of them produced antibiotic and siderophore compounds in vitro.

Differential lock is a means of improving tractor performance. This system causes the revolution of the axles to become equal. It, improves traction, decreases abrasion of drive tires, improves fuel consumption, and increases tractor work rate. Despite advantages of the system, differential lock has not been optimized in Iran. Thus, a semi-automatic differential lock system for MF-285 tractor was designed and developed. First of all, the different parts of the system were designed, selected, assembled. Under critical conditions, the designed system should disengage the differential lock. Critical conditions for engaging this system are: using of independent brake pedals, high forward speed, and turning the steering wheel. For sensing and measuring the critical conditions, proper sensors were selected. Output signals of these sensors were sent to a micro controller to decide the continuous engaging or disengaging. Finally, a MF-285 tractor was equipped with the designed system. The tractor performance in primary tillage was evaluated using a mounted moldboard plow with a width of 110 cm and a working depth of 25 cm. These tests showed that unbalanced weight distribution on wheels and unequal traction capacity under drive wheels cause the slip of one wheel to be 6 percent higher thananother. This system improves the unequal slip problem and decreases fuel consumption by 0.5 L/ha.

In addition to farm operations, power tillers in Iran are also engaged in load and passenger transportation. Inspite of their noise and adverse effects on power tiller drivers and bystanders, they have not been adequatly investigated. The initial survey in the present investigation on a 13-hp power tiller at 2200 rpm engine speed revealed that its noise was 92 dB(A), compared to the standard limit of 85 dB(A) which is disappointing. The test site was prepared according to international standards and the noise signals emitted from the system were measured and analyzed in time and frequency domains for audio frequency range (20 – 20000 Hz). The results showed that the noise intensity was higher by 7.74 to 10.75 dB(A) for the microphone position at driver’s ear compared to the bystanders position and that the engine speed played a great role in noise generation for power tiller. This is because the noise increases up to 8.5 dB(A) with engine speed variations. Finally, the power tiller prediction models of sound pressure levels at driver’s ear and bystanders were determined using the experimental data.