JWSS - Journal of Water and Soil Science

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Edible-oil flax (Linum usitatissimum L.) can be an alternate oil-seed crop in Isfahan region. Seeding date is very important in obtaining higher grain yields and a successful flax production. The present study was conducted at the research farm, Isfahan University of Technology in the year 2000 to determine the effect of seeding date and genotype on yield, yield components and maturity of edible-oil flax. In this study, a RCBD with three replications, in which the treatments were organized as a split-plot experiment, was used. Seeding dates (Oct. 17, Nov. 16, March 15, April 13, May 14, June 13, July 15) and genotypes (four breeding lines of edible-oil flax) were considered as the main and the subfactor, respectively. The number of capsules per plant, seeds per capsule, 100-seed weight and seed yield were highest for all genotypes in the first seeding date. Average seed yield in the first seeding date was almost twice, triple and eight times as much as the second, third and the last three seeding dates, respectively. In the second seeding date there was no emergence because of low temperature. The genotype and seeding date interaction on seed yield and maturity was significant. In general, delayed seeding was accompanied by reduction of emergence, number of days to maturity, yield and yield components in all genotypes, with the exception that the last seeding date led to increased number of days to maturity and seeds per capsule. Based on regression analysis, seed weight, number of seeds per capsule and number of seedlings/m2 were the most important components that contributed in seed yield variation, respectively. But, most of the variations in seed yield per plant was affected by number of copsules per plant and number of seeds per capsule, and in that order.

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Genetic variation of 300 genotypes of durum wheat comprising CIMMYT/ICARDA and Iranian germplasm was evaluated in 1999-2000 at Researh Farm of College of Agriculture, Isfahan University of Technology located at Lavark, NaJaf-Abad. Days to heading, days to maturity, plant height, spike length, grain weight per spike, number of grain per spike, number of spikes per m², 1000-grain weight, test weight, grain yield, biological yield, and harvest index were recorded. Coefficients of correlation, step-wise regression, factor analysis and cluster analysis of characters and genotypes were conducted using the studied traits. Results indicated that considerable genetic variations exist for the traits and, in particular for grain yield, harvest index, number of spikes per unit area and number of grain per spike. Grain yield had a positive and significant correlation with days to heading, days to maturity, number of grain per spike and grain weight per spike. Factor analysis for the genotypes detected 6 factors, which explained 76.7 percent of the total variation among data. These factors basically involved potential of assimilate distribution, different aspects of plant storage, source-sink relationships, plant height and tillering potential. Cluster analysis was similar to factor analysis in grouping the characters. According to cluster analysis, the genotypes were calssified into 6 clusters with significant differences among all groups. Mean comparisons of traits in these groups showed that genotypes of groups 5 and 6 were superior in grain yield and harvest index and are beneficial to the local durum breeding objectives.

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Planting density, through its impact on the level of available environmental factors may have significant impacts on grain yield in safflower (Carthamus tinctorius L.). In order to investigate the impacts of plant density on grain yield, yield components and growth characteristics of safflower, a randomized complete block design field experiment with four replicates was conducted in spring-summer, 2000, at Lavark Research Farm (Lat. 32⁰ 32^, N and Long. 51⁰ 23^, E), College of Agriculture, Isfahan University of Technology, Isfahan, Iran. Arak-2811 and Kouseh safflower genotypes were seeded at 16.6, 22.2, 33.3 and 50 plants/m². For establishing these plant densities, plants were seeded in 12, 9, 6 and 4 cm distances, respectively, on ten 8-m-long rows spaced 50 cm apart in each plot. Plant density had no impact on plant growth stages with the exception of button formation. Genotype had significant effects on days to seedling emergence, button formation, and 50% flowering. While both number of days and accumulated growing degree-days for all growth stages decreased with an increase in plant density, Arak-2811 was earlier than Kouseh for most growth stages. Number of branches and heads per plant, number of heads per branch, number of seeds per head and harvest index showed significant decreases with increasing plant density. The decrease in the mentioned grain yield attributes was mainly negated by greater number of plants per m², leading to no significant variation in grain yield between plant densities of the two genotypes. Arak-2811 produced a significantly greater number of heads per branch and 1000-grain weight however, these differences did not lead to any greater grain yield compared to Kousehdue, mainly due to the greater number of branches in the latter. Neither of the leaf area index, leaf area duration, and crop growth rate varied significantly with plant density and between two genotypes, suggesting no difference in dry matter production capabilities of the two genotypes under environmental conditions of the present study.

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Flax (Linum usitatissimum L.), an oilseed crop, is widely adapted and grown in many regions of the world. Oil from regular flaxseed is used as an industrial drying oil because of the high level of linolenic acid (>50 %). However, the oils from new mutant genotypes of flax with a very low linolenic acid concentration (<2 %) are edible. Yellow seed colour can be used as a visual marker to distinguish edible-oil genotypes of flax from those of industrial type that are usually brown-seeded. In this study, different lines of flax with two seed colours (yellow and brown) in combination with two levels of linolenic acid (high and low) were evaluated in a randomized complete block design for agronomic traits, especially seed yield and its components. The results indicated that lines with high linolenic acid concentration had significantly higher seed yield than those with low linolenic acid. However, other characteristics including those of seed yield components were not siginficantly affected by linolenic acid concentration. Seed colour had a significant effect on number of seedling/m², basal branches, capsules per plant and seed yield per plant. Although seedling emergence was lower in yellow-seeded lines, they had more basal branches, capsules per plant and seed yield per plant. Higher seed yield per plant in yellow-seeded lines can be attributed to higher number of capsules per plant as a result of lower seedling emergence and plant density. Seed yield was not significantly different between brown and yellow-seeded lines. Thus, the effect of lower plant density in yellow-seeded lines was compensated by their higher basal branches and number of capsules per plant.

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Planting pattern through changing vegetative growth and utilization of environmental resourses affects yield components and seed yield. These effects were studied in the spring of 2000 at the Agricultural Research Station, Isfahan University of Technology, using a randomized complete block design with a split plot layout and three replications. Main plots consisted of three row distances (30 cm flat, and 45 and 60 cm on bed), and sub-plots included three planting densities (30, 40, and 50 plants m^-2). The experiment was planted on March 13 using local safflower variety of Isfahan, named Koseh. Increase in row distance and plant density enhanced most developmental stages of safflower. Leaf area index was not significantly affected by row distance but increased as planting density increased. Up to the 50% flowering stage, 30 cm row distance produced highest plant dry weight, but had the least dry weight at the end of the growing season, probably due to the strong shedding of leaves. Up to the end of flowering stage, 50 plants m^-2 treatment produced the highest plant dry weight, but ranked lower as compared to 30 plants m^-2 treatment at the physiological maturity, probably due to the shedding of leaves. Row distance had no significant effect on number of branches per plant and per square meter, number of heads per branch, number of seeds per head, 1000-seed weight and harvest index. But number of heads per plant and per square meter as well as seed yield per plant and per square meter significantly decreased as planting distance increased. Plant density had no significant effect on number of branches per plant, number of heads per square meter, number of seeds per head, 1000-seed weight and seed yield. Increase in planting density increased number of branches per square meter, but reduced number of heads per branch and per plant, seed yield per plant and harvest index. The highest seed yield (4769 kg ha^-1) was obtained with 30 cm row distance and 40 plants m^-2 treatment. On average, 397 kg ha^-1 petal was harvested, which has a large economic value. However, petal clipping, over all treatments, reduced seed yield by about 7.4%. Considering the advantages of uniform distribution of plants and adaptation of safflower to flat planting, 30 cm row distance with 40 plants m^-2 might be appropriate for planting safflower under conditions similar to this experiment.

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Soil erodibility in arid regions, particularly in less developed soils, greatly depends on parent material. The objectives of this study included comparison of the potential of runoff and sediment production in soils with different parent materials and identification of the highly sensitive parent materials in Golabad watershed, 60 km northeast of Isfahan, with about 160 mm of annual precipitation and various geological formations, as one of the highly erodible watersheds in Iran. Soils formed on twelve different parent materials were selected. Rainfall simulator was run for 80 minutes on three replicates of each soil. To have an idea about the rate of runoff and sediment generation with time, runoff loaded with sediment was collected every 10 minutes using plastic containers. After measuring the volume of each runoff sample, it was dried and the amount of sediment was measured. The mechanical parameters of the applied rain were: intensity about 40 mm/hr, rain drop average diameter: 6.56 mm plot size: 1 m² and kinetic energy of 13.7-17.2 J/m².mm. Based on the rainfall simulation experiments, soils formed on green andesite and slightly dissected alluvium derived from both sedimentary and igneous rocks created the highest amount of runoff. They also created runoff much more rapidly as compared to other soils. In contrast, soils developed on granodiorite and moderately undulating alluvium produced the least volume of runoff. Furthermore, maximum quantity of sediment was produced from the soils occurring on green andesite and shale. The least sediment yield was observed in soils developed on granodirite and moderately undulating alluvium. Soils formed on shale created the highest sediment concentration and no significant differences were observed among other soils. Based on the results obtained, soils were ranked according to sensitivity to erosion. It is concluded that soil parent materials have a high influence on the production of runoff and sediment yield in Golabad watershed.

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In order to investigate the effects of different nitrogen fertilizer levels and water stress during milky and dough stages on grain yield, yield components and water use efficiency of corn hybrid SC 704 (late maturing, non prolific and dent type), a field study was conducted. The factorial design of the study comprised of a randomized complete block with four replications. Four levels of nitrogen fertilizer (0, 92, 184 and 276 kg/ha nitrogen) along with three levels of irrigation (water stress imposed at milky stage, dough stage and a season-long optimum irrigation) were used as treatments. Results showed that water stress during milky and dough stages significantly decreased grain yield and thousand kernel weight. Also, effect of nitrogen fertilizer on grain yield, kernel number per ear, kernel weight per ear and thousand kernel weight was significant. Maximum grain yield was produced with 276 kg/ha nitrogen, although no significant differences were found among 92, 184 and 276 kg/ha nitrogen levels. Regarding water use efficiency during water stress, maximum efficiency was observed at milky stage but, as water stress declined with optimum irrigation, water use efficiency decreased.

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In order to study the effects of different levels of nitrogen fertilizer and plant density on grain yield and its components in sunflower, an experiment was conducted using 'Record' cultivar at the Research Farm of College of Agriculture, Isfahan University of Technology in 1996. Four levels of nitrogen (0, 75, 150 and 225 kg/ha) and four plant densities (65000, 75000, 85000 and 95000 plants/ha) were used in a split plot arranged in a randomized complete block design with three replications. Developmental stages, plant height, stem diameter, head diameter, number of head per m2, grain yield, biological yield, harvest index, 1000-grain weight, number of grains per head, grain oil percentage, oil yield and grain protein content were measured. The results indicated that N fertilizer caused an extension of the growth period and means of days to physiological maturity. It also increased plant height, stem diameter and head diameter. While increasing plant density had an incremental effect on plant height, it negatively affected stem diameter and head diameter. N fertilizer up to 150 kg/ha increased the grain yield and biological yield, whereas higher levels of N fertilizer decreased both. Plant density of 85000 plants per hectare was observed as a suitable plant density, whereas the higher plant density had a negative effect on grain yield. N fertilizer via increasing the number of grains per head, and plant density via increasing the number of heads per unit area and also decreasing the number of grains per head influenced the grain yield. One-thousand grain weight was not affected by neither N fertilizer nor plant density. Considering the superiority of 150 kg/ha of N fertilizer and plant density of 85000 plants/ha for grain yield and oil yield, it appears that they could be recommended for producing desirable yield in the regions similar to the study region.

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Azospirillum brasilense is one of the N2-fixing microorganisms which, in symbiosis with the roots of cereals and other graminae, enhances growth and development of plants. In this research, wheat seeds (Triticum aestivum) of three cultivars (Ghods, Roshan and Omid) were inoculated with Azospirillum strains (Sp7 and Dol). Inoculation increased growth parameters and yield of wheat cultivars, the effect being directly dependent on the strain-cultivar combination. Strain Sp7 induced the greatest grain yield, 1000-seed weight, number of grains per spike, root and shoot dry weight in Cv. Roshan, whereas strain Dol stimulated the best effect on these growth parameters in Cv. Ghods. The response of Cv. Omid was lower as compared to the other cultivars. Thus, it may be concluded that compatible strains are necessary for increasing yield and enhancing growth and development of wheat cultivars. These experiments also illustrated similar results regarding the effect of strains on N content of seeds. The observation of nitrogenase activity of Azospirillum strains in the In vitro experiments and the significant increases in N content in some inoculated cultivars support the hypothesis that biological nitrogen fixation by Azospirillum could be responsible for the observed beneficial effects on growth parameters. The comparison of nitrogenase activity of two strains showed that acetylene reduction rate for strain Dol was 1.5 times more than that for strain Sp7. Also strain Dol had more pronounced effects on growth parameters, yield and N content of grains than did strain Sp7. Strain Dol is a local strain whereas strain Sp7 is a Brazilian isolate thus, it may be concluded that the local isolates should be preferred to the foreign bacteria, as they are better suited to traditional cultivars, environment and soil conditions of the region.

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In order to investigate agronomic traits and yield potential of edible-oil flax (Linum usitatissimum L.) as a second crop in Isfahan region, different genotypes were evaluated in separate experiments in early spring (April, 7) and summer (July, 16) planting dates, using a Randomized Complete Block Design with three replications. The experiments were conducted in agricultural research farm, Isfahan University of Technology in the year 2000. The results showed that summer planting considerably and significantly reduced number of seedlings per unit area, days to 50% flowering, and seed yield. However, maturity of the plants was delayed because of summer planting. According to overall average obtained for genotypes, seed yield was 1472 and 213 kg/ha in the first and second planting dates, respectively. There was a significant difference between genotypes for number of seedlings per unit area, days to 50% flowering and maturity in both planting dates. However, genotypes were significantly different for seed yield in the first planting date. Summer planting also non-significantly reduced yield/plant, capsules/plant and 100-seed weight and increased seeds/capsule. The differences between genotypes for these traits in both planting dates and for seeds/capsule in the first planting date were significant. The significant interaction between genotypes and planting dates on seeds/capsule and 100-seed weight was because of increasing or decreasing levels of these traits in some genotypes when planting date was delayed. The results of regression analysis, correlation coefficients and path analysis showed that in both planting dates, capsules/plant followed by seeds/capsule and 100-seed weight were the major components of yield/plant. Capsules/plant had the most (approximately 80%) contribution in variation of yield/plant in both planting dates. The number of plants per unit area affected yield/plant via indirect and negative effect of capsules/plant.

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This experiment was conducted to study the effects of using cotton-seed meal on the performance and carcass yield of broiler chickens at different ages. The experiment was performed in a completely randomized design with four treatments and five replicates for each treatment. The experimental treatments included the levels of 0, 3.5, 7, and 10.5% of cotton-seed meal in diets fed to chickens at 7-21 days of age. Except for the control group, these levels for grower (21-42 d of age) was increased to 7, 14, and 21% and for finisher (42-56 d of age) to 14, 21, and 21%, respectively. For the purposes of this study, 260 day-old chicks were reared in litter until 7 days of age. On day 7, chicks were divided into 20 pens with 13 chicks in each pen. NRC (1994) recommendation was used in balancing experimental diets. The chickens were weighed weekly throughout the experimental period (7-56 d). The main observations were body gain, feed intake and feed conversion ratio. Physical analysis of carcass was done at the end of the experimental period and percentages of carcass, abdominal fat, liver, pancreas and digestive tract to live body weight were calculated. The use of cotton-seed meal and the increase of the levels through different ages had no significant effects on body weight, daily gain, feed intake, feed conversion ratio, and carcass components. Increasing the level of cotton-seed meal in the diet at 7-21 days of age had significant effects on feed intake (P<0.05) and increased it. The results of this experiment indicate that we can use cotton-seed meal at levels of 7,14, and 21% of diets, respectively, in starter, grower and finisher stages without having any adverse effects on the performance and carcass yield of broiler chickens.

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Watermelon (Citrullus Lanatus) cv. Charleston Gray is one of the most important cultivars grown in Iran. It has some good quantitative and qualitative characteristics but unfortunately is sensitive to Blossom End rot. To solve this problem, this experiment was conducted in a factorial manner in randomized complete block design with four replications in Research Station and Laboratories of Department of Horticulture, College of Agriculture, the University of Tehran, during 1997 & 1998. In this experiment, black polyethylene mulch was used and calcium nitrate was foliar sprayed at concentrations of 0, 4, and 6 g/L. Results indicated that mulch could increase yield by 85% over two years due to weed growth suppression and conserving soil moisture for a longer time. Foliage fresh weight, number and average weight of fruits per plant and precocity were also significantly affected by black polyethylene mulch. Furthermore, mulch reduced the number and weight of fruits affected by Blossom End rot by about 13% and 12.5% (average of two years), respectively. Calcium nitrate addition during both years had no significant effect on the measured fruit characteristics nor on Blossom End rot.

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Despite its economic importance, not much information exists on growth and productivity of durum wheat in Iran and Isfahan. In order to evaluate growth, grain yield, and attributes in three durum wheat genotypes, Osta/Gata, Dipper-6, and PI40100, with five planting densities of 200, 275, 350, 425 and 500 seeds/m², a four-replicate RCBD field study with a spilt-plot layout was carried out in winter 2000 to spring 2001 at Lavark Research Farm, College of Agriculture, Isfahan University of Technology. Genotypes were the main-plots and planting densities, the sub-plots. Each plot contained six rows, spaced 25cm apart, each 6m in length. While Osta/Gata produced a greater spikes/m², 1000-grain weight and grain yield, PI40100 indicated a greater height, leaf area index (LAI) and biological yield, and Dipper-6 produced a larger number of grains per spike and harvest index, compared to the other two genotypes. Increasing plant density led to an increase in LAI, spikes/m², grain yield, biological yield and harvest index but a decrease in grains/spike and 1000-grain weight. Grain yield was positively correlated with spikes/m², grains/spike and 1000-grain weight, despite negative correlations with LAI and plant height. It may be concluded that with environmental conditions such as those encountered in Isfahan in 2000-2001, Osta/Gata can be planted at approximately 425 seeds/m², if an acceptable grain yield is to be achieved.

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Although safflower is known to be a cool-season crop, it is usually planted as a summer crop in Isfahan. Thus, an experiment was conducted in 2000 at the Agricultural Research Station, Isfahan University of Technology, to study the effects of date of planting on growth, yield components, and seed yield of safflower. Five planting dates (March 12, April 12, May 10, June 8, and July 12) and four safflower genotypes (Arak 2811, local variety Koseh, Nebraska 10, and Veramin 295) were evaluated using a randomized complete block design with split-plot layout in three replications. Date of planting was considered as the main plot and cultivars were randomized in sub-plots. Delay in planting from March 12 to may 10 reduced plant dry weight per unit area, number of heads per plant, number of seeds per head, seed yield per unit area, harvest index and petal yield. The above traits increased as planting was further delayed from May 10 to June 8. Highest seed oil and lowest seed protein contents were also obtained for this planting date. Plants of July 12 planting date did not reach physiological maturity. Among the genotypes evaluated and over planting dates, the highest and lowest number of heads per plant, 1000-seed weight, and seed yield were produced byArak 2811 and Veramin 295 (mean of the first and second planting dates), respectively. Highest seed yield (4512 kg ha

^-1) was produced by local variety Koseh in June 8 planting date. It might be concluded that this variety has adapted to the summer planting conditions of Isfahan by natural selection.

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An experiment was conducted at Rasht Rice Research Institute, in 2001 to study trait relationships and to determine the direct and indirect effects of different characteristics on grain yield of rice (Orgza sativa L.). A 9x2 factorial experiment in complete randomized block design with 3 replications was used. The two factors were 9 cultivars, namely: Hashemi, Ali Kazemi, Binam, Sepeedroud, Nemat, Khazar, Taichung, Chanto, and Usen, and 2 planting patterns (15x15 cm and 30x30 cm). Significant differences were detected among cultivars, between planting patterns, and their interaction effects. The direct effect of the number of panicles/m² on grain yield was positive and significant in both planting patterns and their combined analysis. Heading date had a positive and significant direct effect on the number of panicles/m² in both planting patterns and their combined analysis. Only in 30x30 cm planting pattern, a positive correlation was found between biomass at heading date and the number of panicles/m². Grain weight per plant had a direct and positive effect on panicle weight in the 3 cases studied. Also, in all the cases studied, flag leaf area had positive direct effects on grain weight per plant. Grain filling rate and effective grain filling period increased in 30x30 cm planting pattern. Native cultivars demonstrated longer latent period. Grain filling rate and effective grain filling period showed positive direct effects on grain yield in both plantings. According to the results obtained, an increase in the number of panicles/m², rate of grain filling, and effective grain filling period would enhance grain yield. Selection for heading date, grain yield per plant, and flag leaf area would also indirectly increase grain yield.

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A diallel analysis of eight bread wheat (Ttriticum aestivum L.) cultivars was conducted to determine genetic parameters and the type of genetic control for yield and yield components. The parents and their F1 hybrids were evaluated in a randomized complete block design with 3 replications. General and specific combining ability effects were estimated by the method 2 of the Griffings model I, and the genetic parameters were estimated by the Jinks-Hayman method. According to the analysis of variance, the variances of parents and crosses were significant for all of the traits, except for the fertile tillers per plant in parents and harvest index in crosses. The variance of GCA was significant for almost all of the traits. GCA to SCA ratio indicated a large additive effects for all the traits, except for the number of fertile tillers, grain yield per plant and biological yield. Darab and Chamran cultivars were the excellent general combiners for days to heading. However, Falat for plant height, Arvand for number of fertile tillers, spike length and grain weight per spike, Qods and Arvand for spikeletes per spike, Falat and Arvand for grain yield per plant and Qods and Arvand cultivars for biological yield were the best general combiners. Based upon the Jinks-Hayman method, the average degree of dominance for grain weight per spike, 1000- grain weight, grain yield per plant and biological yield indicated that these traits might be controlled by over dominance effects and other traits by partial dominance. The correlation between Yr and (Wr + Vr) for the flag leaf length, spikeletes per spike, grains per spike and 1000-grain weight indicated that recessive allels enhanced these traits. But dominant allels had their contribution to enhance other traits. The narrow-sense heritability for grain yield per plant (4%) and biological yield (14%) and harvest index (37%) was lower. However, for other traits it was more than 50%. Therefore, it can be inferred that indirect selection of grain yield through selection for yield components such as spikeletes per spike, grains per spike and grain weight per spike with high heritability and correlation with grain yield can be more effective.

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In order to evaluate the effects of plant densities (10, 13, 20 and 40 plant/m² ) on the yield and yield components of two cultivars (Partow, Gohar) and a line (VC-1973A) of mungbean [Vigna radiata (L.) Wilczek] a field experiment was conducted at the Seed and Plant Improvement Institute (SPII) of Karaj in Summer 1998. This research carried out in a factorial experiment based on Randomized Complete Block Design (RCBD) with 4 replications. The results indicated that VC-1973A line had the highest grain yield. This line has superiority to other cultivars, due to the early and uniformity of seed maturity and easy mechanized harvest. Plant density has a significant effect (p<0.01) on the grain yield, in such a way that the densities of 20 and 10 plant/m² outyielded the highest (2221 kg/ha) and lowest (1650 kg/ha) grain yield respectively. Among the yield components, only the number of pods per plant indicated a significant difference due to the plant density. Correlation coefficient between attributes indicated that the plant height and height of first pod internode had a positive correlation with the plant density, while the correlation of the plant density with harvest index (HI), branch number and pod number per plant was negative. More over it seems that the pod number per plant is the most important components of mungbean’s yield, because it has a high (r = 0.88) and significant (p<0.01) correlation with the grain yield.

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The Genetic basis of grain yield and related characteristics were studied by a generation mean analysis in five crosses of winter wheat (Triticum aestivum L.). “Roshan”, “Mahdavi”, “Inia”, “Atila” and “Goscoyin” cultivars along with their F₁, F₂, BC₁ and BC₂ populations were evaluated by a split-plot design with crosses as the whole plot in a randomized complete block design with two replications and generations were applied as the subplots. Analysis of variance revealed significant differences among generations for studied characteristics including the grain yield per plant, the number of spikelet per plant, the number of spikelet per spike and grain weight per spike. For the majority of traits and crosses, F/DH^1/2 was less than one, indicating that the sign and magnitude of gene actions were different. Estimates of broadsense and narrow sense heritabilities were low for the grain yield per plant compared with other traits, rating from 28.5% to 58.6% and 24% to 48,5% for the five crosses, respectively. Genetic components of generation means were calculated by fitting different models and choosing the best model indicated that the impact of additive, dominance and epistasis genetic components in controlling the traits depend on the cross and the trait under study.

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This study was conducted to evaluate the effects of four levels of irrigation (irrigation of plants after I₁ = 40, I₂ =60, I₃ = 80 , and I₄ = 100mm of evaporation from class A pan) and four plant densities(D₁ = 30, D₂ = 40, D₃ = 50 and D₄ = 60 plants/m²) on the seed yield and seed quality in three soybean cultivars(V₁=Hobit, V₂=Williams and V₃=Hill) in a split factorial design, based on the completely randomized blocks, with three replication for two years(2001 and 2002). The Irrigation treatments were assigned to the main plots, and the plant densities and cultivars to the sub plots. Results indicated that soybean seed yield was influenced by the different irrigation and plant density levels in the both years. Irrigation levels I₂ produced the highest and I₄ the lowest seed yield. It was also revealed that the plant density D₃ produced the highest and D₁ the lowest seed yields. Among the cultivars under investigation, V₂ produced the highest and V₃ the lowest seed yield . Seed oil and its protein contents both were affected significantly by the irrigation levels, plant densities and cultivars in both years. The plants receiving I₁ treatment had the highest and those having I₄, the lowest percentages of seed oil. Changes in the plant densities also affected seed oil and protein content. The plant density of D₁ caused the seeds to have the highest oil and lowest protein percentages. However, D₄ decreased oil and increased protein percentages. The highest water use efficiency was obtained from I₃ and that of the lowest value from I₁. The results also indicated that D₄ had the highest and D₁ the lowest water use efficiencies. Therefore, it could be concluded that the water use efficiency can be increased by increasing the plant density per unit area. The highest efficiency for biological and grain yield belonged to V₂ and V₁ respectively where as the lowest efficiency for those two mentioned characters belonged to V₁ and V₃, respectively. However, the treatment I₂V₂D₂ is recommended for higer the seed yield production per unit area.

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Under irrigation and in double-cropping system, a large amount of plant residue remains after harvest that along with the limited time for residue decomposition and complete seedbed preparation, necessitates reduced tillage and special residue management. In the present study, the effects of various seedbed preparation methods on vegetative growth, yield components and seed and oil yields of sunflower (Euroflor hybrid) were studied in a barley-sunflower cropping system during 2001 at the Agricultural Research Station, Isfahan University of Technology. Three residue management treatments (standing, partly removed and burned) along with five tillage systems (moldboard + disk chisel + disk disk moldboard and furrower as the minimum tillage) were laid out in a split-block design with three replications. Burning residue treatment significantly increased plant dry weight at various developmental stages and also head diameter. Number of seeds per head, 1000 seed weight, harvest index, and oil yield were non-significantly higher in the burned residue treatment. Seed yield was significantly higher in the burned and partly removed residue treatments. Moldboard + disk and chisel + disk treatments significantly produced higher plant dry weight at various developmental stages, head diameter and seed yield. Number of seeds per head, 1000 seed weight, harvest index, and oil yield were non-significantly higher in these treatments. Minimum tillage ranked the lowest for these traits. The results of this experiment indicate that chisel + disk treatment with the partly removed residues might be an appropriate seedbed preparation method in a barley-sunflower double planting under conditions similar to this experiment.