THE SCIENTIFIC JOURNAL OF AGRICULTURE (SJA)
Year:2004 | Volume:27 | Issue:1|Papers Count:16

Internet is a powerful and effective tool for education and learningin the information era. It is considered as a key for tomorrow"s education. Internet is not an information resource but it is a collection of human experiences and research findings.The present research is a descriptive and correlational research that surveys the opinion of 95 graduate students of Agricultural College in University of Tehran about using internet and its effectivenessin their study and research activities. The findings show that the internet use of graduate students for producing scientific writings is low and in research activities is moderate. There is a significant correlation between educational level, language skills, owning personal computer, occupation status, field of study, and number of hours using computer with the amount of using internet. Graduate students at Ph.D. level and full-time students, and those having scholarship use internet more than other students. Regression analysis shows that about 67 percent of the differencesin the amount of using internet is predicted by following variables: Educational level, language skills, and the amount of producing scientificwritings.

Preimaginal development and mortality, longevity, fecundity, sex ratio and life table parameters of Bemisia tabaci on aubergine (variety Black beauty) were studied at different constant temperatures. Preimaginal development were 29.35, 24.87 and 14.95 days and preimaginalmortalitywere 15.5, 10.3 and 11.9 at 20, 25 and 30° C, respectively.Adult longevity were 12.71, 9.78, 5.92 and 3.57 days for males and 18.14, 13.14 and 7 days for females at 20, 25, 30 and 35°C, respectively.Average daily eggs were 3.91, 5.08, 5.81 and 2.48 and,total eggs were 78.66, 71.33, 51.8 and 19.5 at the same four temperatures, respectively. By increasing temperature from 20 to 30 °C sex ratio increased in favour of females. Intrinsic rates of increase at 20, 25 and 30°C were 0.08183, 0.0927 and 0.1413, respectively. It was revealed that 30 °C was an optimum temperature for population increase of Bemisia tabaci.

Water deficit can reduce seed yield in development stages of soybean plant. Tolerance to drought conditions in soybean depends on planting date. Maturity group of cultivars, time and duration of drought conditions. To evaluate the response of 25 genotypes of soybean to drought stress during reproductive developmental stage, two experiments were conducted using a 5x5 lattice design under stress and non-stress conditions. Results of analysis of variance showed- significant differences among cultivars for most of agronomic traits in both stress and non-stress conditions. Significant differences were found among cultivars for seed yield only in stress conditions, Williams and Probest cultivars had the maximum and minimum seed yield content respectively (2350.6 and 1048-.1kg/ha). The highest damage due to drought stress was found on branch hollow pod (-57.53%) and drought stress decreased the seed yield about (37.70%). In non-stress conditions, the majority of traits had significant correlation with seed yield (r=0.318) whereas in stress conditions, only number of branch seed and 100-seed weight had significant correlation with above-mentioned trait (r = -0.344). Based on the results of traits correlations, step wise regression and path analysis in non-stress condition, harvest index, number of plant pods, the distance of first pod trom earth surface, blooming duration branch seed weight, and in stress conditions, the number of days until end of blooming seems to be desirable characters in selectionof cultivarswith high seed yield.

To investigate the competition between wild mustard and winter wheat in response to the amount and timing of nitrogen application, an experiment was conducted in 2001 at Research Farm of Mashhad, College of Agriculture. Split-plot design with three replications was used with factorial of weed density (0, 8, 16, and 32 plant/m2) and nitrogen (low=I00,optimum=150, and high= 225 Kg/ha) as main plot .The sub-plot included nitrogen split pattern (P1=I:3 at planting time+2:3 at tillering, P2= 1:3 at planting time + 1:3 at tillering+ 1:3 at Shooting).Our results indicatedthat nitrogen-split pattern had no significant effect on growth parameters of wild mustard and wheat. Growth indices of two species showed that the leaf area index (LAI) and dry matter (DM) of winter wheat decreased with increasing in LAI and DM of wild mustard. Increasing nitrogen amount, especially at high rates, stimulated wild mustard competitiveness on changing wheat growth indices. In this experiment, the key characters resulted in successful competition of wild mustard were the higher height of wild mustard, due to high stem relative growth rate (SRGR) and high leaf area relative growth rate (LRGR) during wheat stem elongation.

Seed quality changes during development and ripening period and also environmental factors affect final seed quality. In order to determine the effects of drought stress (environment parameter), These cultivars and seven harvest times (development and ripening stages) on seed vigour variations, germination (percentage) and ripening stage of wheat with maximum seed quality, an experiment was carried out in 1999/2000 at Ramin Agricultural Research and Education Center of Shahid Chamran Univeristy, Ahvaz. The experiment was arranged in split-split plot design with 4 replications. Irrigation were levels the main plots, wheat cultivars were as subplots and the subsubplots were seven seed hervest times during ripening period. At final harvest, germination and seed vigour tests were carried out at the end of the experiment. Results indicated that only harvest times had affected germination percentage. The highest and the lowest germiantion percentages were obtained at the sixth (99.8%) and the first (76.2%) harvest, respectively. The effects of the cultivar and drougth stress on germination were not significant. Cultivars and harvest times were significantvariables affecting seedling dry weight. Durum wheat cultivarshad the highest seedling dry weight (328 mg) in comparison with other cultivars. The highest level of seed vigour and germination was obtained at physiological maturity (maximum seed dry weight) at 44 days after antheses. In this stage seed moisture was lower than 15% which is suitable for mechanicalharvestingy.rithoutdamageto seed quality.

The sand dunes of Khuzestan, with the area of 350,000 hectares, includes 5.3 percent of the whole province. 5790 ha. out of this area, have been mulched for primary sand stabilization and 8156 ha. have been planted for biological stabilization during 1995 - 1999. Tamarix aphylla, Calotropis procera and Prosopis juliflora are most three important plant species which were planted for stabilization of sand particles. One of the most important pests, which causes damages to these plants and may demolish them, is the sand termite, Psammotermes hybostoma. Percentages of infestation and damage were compared in seven different parts of the stabilized sand dunes.The results showed that the percentages of loss and infestation were significantly different in the studied areas. In addition, these three species were significantly different in resistance to the termite"s attack. The percentages of infestation to termite for Calotropis procera,Tamarix aphylla and Prosopis juliflora were 82.5, 57 and 22 respectively and the percentages ofloss were 55, 20 and 4 respectively. It is concluded that Prosopis juliflora is the most resistant species to termite"s attack among the three plant species. No significant difference between mulched and unmulched sand dunes due to infestation of Tamarix aphylla to termite damage was considered.

The structure ,ofthe flow at side-weiris very complicatedand in spite of numerous works on this topic, no general model exists for accurate estimation of the discharge. Irrigation canals are usually built in trapezoidal cross sections; however, most previous researches for side-weirs were carried out in canals with rectangular cross section. In particular, no .work was done on the effect of upstream side slope on side-weir discharge coefficient.In this study, to investigate the effect of side slope and weir height on discharge coefficient, a long physical model was built and a series of experimentaltests were carried outunder different flow conditions. The experimental model consists of a trapezoidal concrete canal with different side slopes as: 1:0, 1:0.5, 1:1 and 1:1.5, and constant base width of 0.4 m at all reaches. All side-weirs were set at constant height of 0.1 m, and constant length of 0.3 m. The experiments were carried out in different flow conditions and the discharge was measured using pre-calibrated standard right angle V-Notch. A mathematical model was developed to estimate discharge coefficients and overflow discharge over the side-weir.The mathematical model was compared with experimental data. To compare the developed model with some of the previous mathematical models, the results of those models were also compared with the experimentaldata. The results showed that the developed model gives better estimation of discharge coefficient,when compared with the previous models for open-end flow condition. Additionally, the experimental results for similarflow conditions showed that the side slope of 1:0.5 gave high discharge coefficientas comparedwith the other side slopes.

Present investigation was carried out to determinethe suitable variety and date of sowing with high seed and oil yield in Islamabad region of Kerman shah in 2000. In this study, four planting dates (September 9, 20 and 29 and October 9) and five canola genotypes (Orient, Talateh, Okapi, SLM046 and Colvert) were evaluated using a randomized complete block design with split-plot layout in 4 replications. Results showed that sowing dates effect was significant at .01 level of probability on yield components, plant height, biological yield, and number of secondary branches. Harvest index, oil content, oil yield, and number of plants/square meter, the first sowing date (Sept.9) showed the best results. Difference between varieties was significant at .01 level of probability for number of pods per plant, seeds number/ pod, l000-seed weight, number of plants/m2, harvest index, biological yield, oil yield, secondary branchs number and seed yield, but oil content was non-significant. Among the cultivars, the highest and the lowest seed yield belonged to SLM046 and Okapi with 2.59 and 1.77 t/ha, respectively. Results of oil yieldhad the same trend as adove. Reduction in seed yield for these canola cultivars were considered to be related to the coincidence of anthesis and ripening of pods and seed growth stages with higher temperatures prevailing at later planting dates. Nevertheless, the highest amount of the seed yield (4.08 t/ha) was obtained from SLM046 at the first planting date.

Resistance of five varieties of rapeseed oil,Mohican, Licord, Consule, Talayehand SLM046 and the wild weed Sinapis arvensis to cabbage aphid was evaluated in field and laboratory conditionsbetween years 2001-2002. Under the field condition, the infestation index (infested stem lengthx percentage of infested plants) was used for this evaluation. Results showed that Talayeh with the highest infestation index was very susceptible and Sinapis arvensis was the most resistant. The varieties SLM046 and Consul were susceptible and moderately susceptible, respectively.Licord and Mohican, as one group, were placed between two varieties SLM046 and Consul. In laboratory, the intrinsic rate of increase (rmm), pre- reproductive and reproductive period and the number of offspring were calculated. The mean rmin Talayeh, Licord, SLM046, Mohican and Consul were 0.343,0.309,0.276,0.269 and 0.239 , respectively.The mean pre-reproductive period of cabbage aphid was the longest in Talayehand Licord, and was the shortest in Consul.The longest and shortest reproductive periods of the aphid were calculated on Licord and Consul, respectively. All varieties were significantlydifferent in number of offsprings The highest number of offsprings was produced on Talayeh and the lowest was on consul. These two series of experiments showed that the most susceptible was Talayeh and the most resistant was Consul.

This experiment was conducted to investigate the effect of different levels of sulfur on the microbial protein production in male Raini goat. Fifteen Raini male goats with mean body weight of 32±.7kg and 13-14 month of age were used. The trial was carried out using completely randomized design with 5 dietary treatments containing either 0.14, 0.22, 0.28, 0.34 or 0.4% sulfur (DM basis). Each treatment had three replicates. The isocaloric and isonitrogenous diets were formulated according to AFRC (1998) recommendations. The metabolisable energy and the metabolisable protein of the diets were 9.57 (MJ/kg DM) and 8.42% respectively. Animals were kept in individual cages for 3 weeks and during the third week their urine sample were collected for the estimation of purine derivatives. The dry matter intake and live weight gain of the animals were measured. Additionally, the digestibilty of the dry matter and organic matter for the rations were determined. The in vivo digestibilityof dry matter and organic matter for the ration no.2 was the highest in comparisonto other diets. Also, the animals offered the level 0.22% sulfur had the highest live weight gain among all the treatments. Results showed that the effect of different levels of sulfur on microbial protein production and urinary purine derivatives were significant (P<0.01). Microbial protein production in the diet containing 0.22% sulfur was significantly (P<0.05)higher than other rations. Analysis of regression equations showed that there was a quadratic relationship between sulfur and microbial protein production. The best level of sulfur was 0.265%.

Fiftheen heads of buffalo for a period of 105 days were used in a latin square design (5 blocks, 5 periods and 5 diets). The diets contained 25 and 50% reed silage and 25 or 50 % dry reed grasses with molasses. Daily milk yield and milk compositions (fat and protein %) were measured. The mean of daily milk yield for the mentioned diets was 7.59, 7.62, 7.79, 7.58 and 7.73 kg, respectively.Fat percentagewas 6.14, 5.80, 5.74, 5.87 and 5.58, respectively. Protion percentage for the mentioned diets was 5.63, 3.62, 3.62, 3.81 and 3.98, respectively. The differencesbetween means of the mentioned variables were not significant (p>0.05). Results obtained show that consuming diets of dry reed enriched by molasses or ensiled by 50% did not affect the milk yield or milk component comparing with the control. From an economic point of view, the most economic diet was that with 50 % reed plus molasses. Accordingly, the of enriched reed by molasses (dry or silage) is a suitable replacement for combination of alfalfa and straw, and these diets could be suggested. To use a higher level or other preparation procedures, more investigationis needed.

The purpose of this research is to estimate the production function of cold water fishes in kohgiloyeh and Boirahmad provinces. By using the econometric methods, effects of various factors on production of cold water fishes were estimated and exmined. These factors were food, number of primary pieces, weight of primary pieces, area of pool, time, labour force, discharge of water and water temperature. Two kind of data, secondary and primary were required. The former was collected through the questionnaires and face to face interviews. Scope of the study includes all producers of cold water fishes in the province during 2000-2001. Cobb-Douglases production function was estimated by OLS technique. Results show that the amount of used food, discharge of water and water temperature have positive effects on production and by increasing these factors, the production will be increased. Another factors such as number of workers and primary pieces have negative effects on production and by decreasing these factors, the production will be increased. The findings also show that the return to scale is more than one. It follows that if all inputs double, the amount of production will increaseby more than twofold.

Effects of different preplanting treatments on yieldwere compared with burning the plant residue after harvest as traditional farming system(a6), and with no residuals left from previous crop (a8). Preplanting treatments were: mixing the total wheat straw produced by previous crop with soil (a3), mixing wheat crop residuals after taking out straws from the field (a4), sowing a plant (as green manure) with total wheat straw (aI, a5), and using green manure with previous crop residual after removing a part of straws from the field (a2, a7). These preplanting operations were combined with three levels of chemical fertilizers; i.e. b1 for high yielding potential (to produce 7 tons/ha grain yield), b2 for medium yielding potential (to produce 5 tonslha grain yield), and b3 for ordinary yielding potential (to produce 3 tons/ha grain yields). The experiment was conducted at the experimental farm, College of Agriculture, Charnran University, during planting season (1999-2000). The preplanting treatments were applied in early fall season and the main crop was planted in December. The following results were obtained from the analysis of the data included after harvesting in May. Mixing the whole straws with soil increased grain yield of wheat because of enough soil humidity for relative straw decomposition (52.2 mm rainfall in fall 1999 before sowing). The same situation was observed for medium level of fertilizer consumption. Mixing the .total straws with soil, despite common ideas, increased wheat grain yield because of its positive effect on the process of organic matter in the soil. The average amounts of organic matter in the soil varied between 0.511 and 0.713 percent five months after by applying different preplanting treatments compared to control treatment. These promising findings, if confirmed by additional studies in future, can be nominated as preplanting treatments and effectivetechniques for increasinggrain yield.

In order to decrease temperature by shading of corn on potato rows for potato planting, an experiment was conducted in early and middle September for two years (1999-2001) at Behbahaha Agriculture Research Station. A split-plot experiment in randomized compelet block design with three replications was used. In this experiment, potato and corn were grown as pure stands and intercrops through strip intercropping method. Plant date, considered as main factor, had three levels: 6,16 and 26 September and planting system as subfactor had five levels: pure stand of potato cultivation.in four rows, intercropping of three rows of potato and one row of corn, intercropping of two rows of potato and two rows of corn. ntercropping of one row of potato andthreerows of cornandpure standof corncultivationin four rows. Corn "hybrid 704" was planted in early August. Ajax and concord potato cnivars were planted in the first and second year respectively.Corn was harvested in pasty development stage in early October. In the first and second year, ITost occurred in Nov. 30 and Jan. 25 respectively and all potato foliages were killed. The obtained results showed that yield of corn in intercropping decreased as compared with pure stand. Potato yield was very low in both of purestand and intercrop in two years of experiment. Corn shading on potato rows didnot affect germination percent and potato yield, so intercropping of potato and corn in autumn planting is not advisable in Khouzestan province.