Crop Production
Year:2010 | Volume:3 | Issue:3|Papers Count:15

In order to evaluate the effect of row space and weed management on weed population, chickpea yield and yield components, a factorial experiment based on RCBD with three replications was conducted at field research of Agriculture College of Lorestan University in cropping season of 2006-2007. In this research experimental factors were chickpea row spaces with four levels (15, 20, 30 and 40 cm with fixed density 50 bush/m2) and weed management in 5 levels (weedy control, single and double weeding, pyridate post-emergence application and Fomesafen pre-emergence application) . Results showed that with increase of planting row distance, biological, grain yield and yield components of chickpea reduced, but weed biomass enhanced. The lowest weed biomass belonged to weeding treatments, pyridate applied post-emergence and fomesafen applied preemergence, respectively. Also, the highest grain yield (1058 kglha) belonged to . double stage weeding. Fomesafen applied pre-emergence and current herbicide (pyridate applied post-emergence) had not significant difference in relation to weed biomass. Fomesafen applied pre-emergence had not unacceptable phototoxic effects on chickpea.

Understanding the seed germination response of cultivated genotypes to temperature is important, agronomically. The genotypes that germinate in lower temperatures could be useful for situations (such as late winter plantings) where temperatures are low in germination stage. Therefore, this experiment was conducted to study the cardinal temperatures, response to sub- or supra-optimal temperatures and thermal tolerance of seed germination in 12 wheat cultivars from the north of Iran. The effects of seven constant temperatures between 5 and 34°C on the seed germination characteristics were also evaluated. The base (Tb), optimum (To) and maximum or ceiling (Tc) temperatures for germination changed from 2.04 to 2.9°C, 31.81 to 32.42°C and 38.08 to 42.08°C, respectively. The analysis of variance revealed no significant differences between cultivars for cardinal temperatures. The effect of cultivar on thermal tolerance was not also significant, but differences between cultivars for thermal tolerance in supra-optimal temperatures were more than sub-optimal temperatures. Generally, all cultivars were more responsive to supra-optimal temperatures than sub-optimal temperatures. In the other hand, the slope of regression line of germination rate (GR) versus supra-optimal temperatures was more than that of sub-optimal temperatures. The difference between cultivars was significant in response to sub-optimal temperatures, only. The effect of cultivar, temperature and their interactions on germination characteristics including maximum germination (Gmax), time to 10% germination (D10), germination uniformity (GU) and germination rate were significant (p=0.01), statistically. The evaluated cultivars showed the greatest Gmax in 13 or 20, but the greatest GR in 32°C. Also, D10 and GU decreased as temperature increased to 25 or 32 and 32 or 34°C, respectively. The results showed that the difference between 5°C and higher temperatures for Gmax was very less than GR, D10 and Gu. This means high Gmax can be obtained in temperatures near to Tb under without soilborn pests conditions.

In order to study the radiation interception and red to far red light ratio variations in sunflower hybrids under drought stress, nine sunflower hybrids in three separate experiments were compared as randomized complete block designs with three replications at the Research Station of Seed and Plant Improvement Institute in Karaj in 2006. First experiment (control) was irrigated based on 60 millimeter evaporation from evaporation pan. The second and third experiments were irrigated at 120 and 180 millimeter evaporation from class A evaporation pan, respectively (medium and sever drought stresses, respectively) . Average of solar radiation intensity and red to far red light ratio in bottom canopy, Solar radiation interception, number of active leaves, total dry weight per plant at seed filling stage and seed yield showed significant difference among irrigation treatments. The intensity of drought stress increased the solar at the bottom of canopy and red to far red ratio by 35 and 45 percentages, whereas caused to decrease the radiation interception of control treatment as 0.95 to 0.88 in sever drought stress. Results indicated that Allstar hybrid with appropriate leaf area index (LAI) and number of active leaves and maximum radiation interception produced the highest dry weight and seed yield, in drought stress conditions.

In order to study the effect of irrigation on fatty acid composition, oil and protein content of sunflower cultivars included Azargol, Allstar, Alison and Euroflor, an experiment was conducted at Experimental Field of the Agricultural Faculty of Bu-Ali Sina University in 2007. Treatments were arranged on split plot based on randomized complete block with three replications. The irrigation treatments were full irrigation, deficit irrigation by withholding irrigation at heading, flowering, seed filling, at heading and seed filling and at flowering and seed filling stages. The results indicated that the highest protein percent was obtained from deficit irrigation treatments at seed filling period (23.2%) . The highest oil percent (40.9%) was obtained from full irrigation treatment same with deficit irrigation at heading stage (40.6%) . The lowest protein (22.2%) and oil (38.5%) were obtained from full irrigation and water deficit at flowering and grain filling, respectively. The highest protein (23.8%) and oil (41.8%) were observed at Euroflor. The highest seed yield (4805 kg ha-1) was obtained from all cultivars at full irrigation and Euroflor at water deficit on seed filling stage. Full irrigation (1985.8 kg ha-1) and Euroflor cv. (1707.9 kg ha-1) have the highest oil yield. Deficit irrigation treatments at seed filling period have the highest oleic acid to linoleic acid ratio. Euroflor cv. had the highest oleic acid content (44.4%) and oleic to linoleic acid ratio (0.98) and had the lowest linoleic acid content (45.1%) and saturated fatty acids (10.5%) . At all deficit irrigation at seed filling period produced the highest oil quality. The highest seed protein and oil percent and oil yield and quality belonged to Euroflor.

In order to study of combining ability and heterosis in cotton (Gossypium hirsutum L.), six hopeful genotypes were crossed in a half-diallel scheme at Gonbad Research Station. Fifteen F I hybrids along with six parents were grown in randomized complete block design with 3 replications, in 2004. Combining ability estimates were calculated according to method 2, model 1 of Griffing (1956a, b) .Relative importance of general combining ability (gca) and specific combining ability (sca) was estimated by the Baker (1978) ratio. Analysis of variance showed that differences due to genotypes were significant for yield, boll weight, monopodial branches number, middle sympodial branches length and node distance from main stem (P£0.01) .The mean of squares due to gca effect were significant (P£0.01) for all studied traits, and variances due to sca effect were significant for yield, boll weight and monopodial branches number. The results suggested that variation for number of monopodial branches, sympodial branches length and the distance between the first node on sympodial from the main stem, could be attributed to additive gene effects, whereas non additive gene effect accounts for seed cotton yield and boll weight is controlled by both additive and non additive gene effects. Among parents, tabladila and shirpan-603 had the highest GCA for seed cotton yield (P£0.05) . The highest heterosis for yield and boll weight was 23.6 and 15.8 percent, respectively. The results indicated the importance of heterosis breeding for effective utilization of non-additive genetic variance. The combinations with higher heterosis are sufficient for hybrid production in cotton breeding program.

Leaving crop residues on the soil surface may significantly affect the behavior and activity of herbicides. In order to study the effect of wheat residue and different rates of trifluralin (%48 EC) herbicide on the yield and oil content of sunflower (Helianthus annuus) a field experiment was done in Agricultural Research Station, The University of Birjand in summer 2008. Experimental design was randomized complete block design with three replications that arranged as factorial. Factors were included wheat residue rates with 4 levels (0, 1250, 2500 and 3750 kg ha-1) and trifluralin (%48 EC) rates with 4 levels (720, 1200, 1680 g ai.ha-1 and control (herbicide free)) . Result showed that using 2500 kg.ha-1 wheat residue increased head diameter, oil content, yield and yield components expect harvest index significantly; whereas, decreasing of measured indices were observed at residue rate of 3750 kg ha-1. The highest seed yield obtained from 1200 g ai ha-1 and residue rate of 2500 kg ha-1 residue treatment.

In order to investigate the contribution of ear photosynthesis and cytokinin in determining grain sink size, a pot study was conducted during January to June 2005 in Cereal Glasshouse of Faculty of Agriculture of Karaj, Iran. Experiment was conducted in a complete randomized design with a factorial arrangement of two factors, three replications and four pots in each plot. Factors included cultivar in four levels and treatments in three levels.Cultivars were: M80-7, Hull-less, Reihan and Walfajr. Treatments were control, removal of ear photosynthesis and removal of ear photosynthesis plus reducing ear transpiration. All treatments were made immediately after ear emergence. Results indicated that ear and 1000- grain weights were reduced by removal of ear photosynthesis in M80-7 and Hill-less and by reducing of ear transpiration in Reihan and Walfajr. Positive correlation between ear and 1000-grainweight suggested that treatments affected sink size via reduction in mean grain weight. Also, treatments increased protein concentration but had no effect on ear protein content. Since there was a negative correlation between 1000-grainweight and grain protein concentration, it was concluded that increased grain protein concentration was a consequence of decreased starch accumulation in grains. On the other hand, reduced ear transpiration did not induce any changes in stem mass; therefore stem remobilization did not compensate for reduction in final grain yield. It seems that ear photosynthesis and transpiration have significant role in determining sink size by providing photoassimilates and regulating cytokinin flux to developing kernels.

Crop rotation affects on crop nitrogen uptake and nitrogen use efficiency(NUE) Crop rotations with high NUE decrease energy use and increase level of sustainability in agro ecosystems. The objectives of this research were to determine the suitable double cropping system for enhancing NUE and evaluate the effects of crop rotation, N fertilizer rate and return of crop residue on NUE. This study was conducted under cold temperate climate condition in Khorasan-Razavi during 2006-2008 growing seasons. A randomized complete block design in split-split plot arrangement with three replicates was used. Main plots were crop rotation with five different rotations (wheat: wheat, potato: wheat, silage corn: wheat, clover: wheat and sugar beet: wheat) and sub plots were N fertilizer rates in preceding crop with four levels (without N (Control), 50% lower than optimum N rate, optimum N rate and 50% more than optimum rate) . The sub-sub plots were preceding crop residue return with two levels including no residue return (Control) and 50% return of crop residue. Results showed that nitrogen use efficiency, nitrogen uptake efficiency and nitrogen utilization efficiency were significantly affected by crop rotation and N fertilizer rates. The highest and lowest NUE recorded for Com: wheat and wheat: wheat rotations, respectively. The highly NUE in the com: wheat rotation is due to the higher NUtE in this rotation. NUE indices in all crop rotations reduced with increasing N fertilizer rate. NUE in potato: wheat rotation showed highest response to N fertilizer rate. Return of crop residue had no significant effect on NUE indices.

Breeding for environmental stress is one of the most important goals in plant breeding. Among stresses, drought stress has high influencing on limitation of wheat production. So, in order to find the best drought tolerant genotypes, 24 genotypes were planted in three separate experiments in Ardebil: one with optimum irrigation (control), another with water stress at pre-anthesis stage and the other with water stress at post-anthesis stage. RBCD experiment design with four replications was used. Stress Susceptibility Index (SSI), Mean Productivity (MP), Tolerance (TOL), Geometric Mean Productivity (GMP), Stress Tolerance Index (STI), Modified Stress Tolerance Index for optimum condition (K1STI) and Modified Stress Tolerance Index for water stress condition (K2STI) indices were used to evaluate susceptibility and tolerance of the genotypes. Results showed that, genotypes number 15 and 21 had higher grain yield than mean in all irrigation conditions. These genotypes had the highest STI and located at part of high yield potential and low sensitivity to drought i~ the biplot. According to TOL and STI, genotype number 15 had the highest water stress tolerant and highest yield in all studied conditions. Also, results of biplot analysis and correlation drought tolerant indices with Ys and Yp showed that STI, GMP and MP were the best indices for yield predicting. K1STI and K2STI along with STI were important indices to select genotype for control and stress conditions.

Partitioning of photoassimilates between the sinks is one of the most important physiological processes related to the yield of crops which are affected by drought stress. Therefore, the effect of drought stress in flowering and grain filling stages, on the percentage partitioning of photoassimilates among different organs was studied in 14 rapeseed cultivars in a split plot experiment based on completely randomized block design with 3 replications. Main plot included 3 regimes of irrigation and sub plot included 14 cultivars of rapeseed. Drought stress was imposed at two stages of flowering and grain filling stages by stopping irrigation.In the former treatment plots were rewatered when soil water potential reached -1.5 Mpa and in the latter plots were not ireirrigated until maturity. Seed yield, dry weight per plant, percentage dry weight of pod, leaf, stem and root measured after ripening and harvest. The results showed that drought stress at flowering and grain filling stages play an important influence in the partitioning of photoassimilates among different plant organs so that the stress at flowering stage decreased seed yield by 51 percent through increasing dry weight percent of leaf, stem and root or in other words percentage partitioning of photoassimilates to growing organs were more than reproductive organs. Drought stress in seed filling increased somewhat seed yield through remobilization of photoassimilates in leaves to other organs.However, this increase didn' t make significant changes on the yield. Among the cultivars studied, opera, Hayola308, Hayola420, P.F and Zarfam that before of flowering stage have high dry weight per plant and equal partitioning among organs, after ripening in normal condition have high seed yield by partitioning of photoassimilates to pods. In this study interaction of irrigation and cultivar on the partitioning of photoassimilates was not significant So that all cultivars with a similar process were affected by drought stress.

In order to determine yield stability and evaluation of genotype x environment interaction, 20 spring bread wheat promising lines and varieties were studied in a randomized complete block design with three replications in four warm and dry stations (Ahwaz, Dezful, Darab, & khorramabad) during 2002-2004. Chamran cultivar was a check in two years trial. The results revealed that the grain yield of genotypes were different in studied environments. Combined analysis results conftrmed that the effects of location and year, and the interaction of location x year x genotype were signiftcant statistically in 5% and 1% levels respectively.Stability analysis for grain yield of genotypes based on Eberhart and Ressel linear regression coefftcient, Wrick's ecovalence, Shukla's stability variance, Index for simultaneous selection, non-parametric statistic method (mean rank of yield, standard deviation of rank of yield, and yield index ratio), AMMI and SHMM models, revealed that the genotypes No.1, 7 and 2 were the most stable genotypes.

Environmental issues have attracted many concerns in recent years. Life cycle assessment (LCA) is a method that evaluates all environmental effects of a product during its life cycle. The objective of this study was to introduce LCA [to Persian researchers] and to use it in assessment of environmental impact of wheat production in Gorgan, NE Iran compared to European counties. First, data were gathered regarding materials and processes in wheat production, the inventory analysis. Then, all resources and emissions per each ton of wheat grain were quantified. Finally, the impact of the emissions and resource usage were aggregated into some indicators: The results indicated that wheat production in Gorgan has important environmental impacts regarding depletion of non-renewable energy sources, global warming, eutrophication, photochemical oxidation, acidification and ozone layer depletion. There is a significant gap between Gorgan and European countries (optimum situation) that should be considered

A hydroponics study was carried out in order to understand the behavior of antioxidant enzymes, soluble protein content and its effect on cell death in different old leaves of durum wheat. Two month after planting, the different old leaves were sampled and the activity of super oxide dismutase (SOD), catalase, ascorbat peroxidase and guaiacol peroxidase were measured. Furthermore, the rate of cell death and total protein content were analyzed. In old leaves, SOD activity was diminished and amongst its isozimes, Cu/Zn-SOD was the one demonstrating a significant reduction in activity. Catalase and ascorbat peroxidase decreased in old leaves significantly, but reduction in Glutathione peroxidase activity was no significant. In general, aging caused reduction in soluble protein content.Accumulations of oxidative factors were seen by reduction of antioxidant enzymes activity. Subsequent, metabolic malfunctions led to higher cell death rate as leaves were aged.

Sowing date and plant density are important factors in grain yield of cow pea. In order to study effect of sowing date and plant density on yield and yield components of cow pea, an experiment was conducted in research farm of Ramin University of Agricultural and Natural Resources in 2008. The experimental design was split plots in randomized complete design with four replications. The experimental factors were sowing date (7 Jun., 22 Jun., 7 Jul. and 22 Jul.) in main plots and inter row spacing (-10, 15, 20 and 25 cm) in sub plots. The results showed that sowing date had significant effect on all of traits, in the other hands, inter row spacing had significant effect on number of pods in plant, number of grains in pod and grain yield, but had not significant effect on 1000 grain weight and harvest index. Interaction effect of sowing date and inter row spacing was significant only for grain yield. Also, comparison of means showed that with delay in sowing date and increase of inter row spacing, decreased the grain yield.

Genetic variation is necessary factor for continued breeding and increasing genetic gain from selection in crop plants. To evaluate genetic variation and genetic gain from selection in bread wheat, 45 genotypes consisting of 9 cultivars and their 36 crosses were grown in a randomized complete block design with three replications in research farm of Isfahan University of Technology. The phenotypic and genotypic coefficients of variation for grain yield (24.6% and 21.7%, respectively), grain number per main spike (19.6% and 19%), grain weight per spike (19.6% and 19.6%) and biological yield (18.6% and 16.5%) indicated that there is a great degree of variation for these traits in this study. The highest narrow sense heritabilities were belonged to grain number per spike (79%), spike length (62%), 1000 grains weight (58%) and spikeletes per spike (57%) . Due to magnitude of heritability of grain yield (18%), its genetic gain (9.12%) was relatively low compared with other traits. The genetic gain for grain number per spike (32.3%), 1000 grain weight (14.3%), and grain weight per spike (12.9%) was larger than other evaluated traits. In general, selection of superior genotypes based on grain number per spike and thousand grains weight could improve grain yield in breeding programs of wheat.