AGROECOLOGY (بوم شناسی کشاورزی)
Year:2011 | Volume:3 | Issue:4|Papers Count:12

In order to determine the critical period of weed control in safflower (Carthamus tinctorius L.), a field study was conducted in the Agriculture Research Station of Yasouj, Iran, during 2008-2009. The experiment carried out in a Randomized Complete Block Design (RBCD) with 16 treatments and four replications. Treatments consisted of two series of treatments. The first group consisted of weed removal from planting to 5-leaf, stem elongation, mid period of stem elongation, lateral stem emergence, beginning of flowering, end of flowering, end of seed ripening stages and then weed retaining until harvest. The second group consisted of weed retaining from planting to mentioned stages and then weed removal until harvest. Two control treatments (weed free and weedy check) were also applied. In order to determine the critical period of weed control, curve fitting Gompertz equation (for weed free period) and Logistic equation (for weed infested period) were used. Results showed that seed yield (31.4%), number of heads per plant (61.5%) and number of seeds per head (23.9%) were significantly decreased by increasing the weed interference period, and by increasing weed-free period, these characteristics were increased significantly. With considering 10% acceptable yield losses, the critical period of weed control of safflower was 134-188 days after planting (between early stem elongation and lateral stem emergence).

In order to evaluation of freezing tolerance in viola (Viola gracilis L.) under controlled conditions, a trial carried out in completely randomized design with six replications at college of agriculture, Ferdowsi University of Mashhad, Iran, during 2008-2009. Seeds were planted in bed and seedlings were acclimated during natural conditions in autumn and at 5-7 leaves stage plants transferred to the thermo-gradient freezer to apply 12 freezing temperatures (0, -2, -4, -6, -8, -10, -12, -14, -16, -18, -20 and -22oC). Leaf cell’s membrane integrity was measured through electrolyte leakage (EL) after the freezing and survival percentage and plant recovery (e.g. plant height and dry weight, number of branches and flowers and flower’s diameter) were determined after three weeks of plant re-growth in the cold frame. As temperature decreased, EL% increased significantly and reached to the maximum in -20oC. Survival percentage did not affected by temperatures between 0oC to -18oC but all plants killed in -22oC. LT50el and LT50su were -20.0oC and -19.4oC, respectively. Decreasing the temperature lower than -18oC reduced plant dry matter severely and RDMT50 was -19.2°C.

Land use change of forest ecosystems in northern Iran changes the soil quality of Paresar (Gilan province) and Gorgan (Gorgan province) regions. In order to study changes in some biological soil quality indices due to land use change from forest to cultivated lands, composite soil samples from two depths (0-20 and 20-40 cm) were taken from Paresar and Gorgan regions and urease, alkaline and acid phosphatase, invertase and arylsulfatase enzymes activities besides some biological properties consisting of microbial biomass carbon and nitrogen, carbon and nitrogen mineralization and respiration due to substrate addition were measured. Results showed that land use change caused biomass carbon (44-82%), biomass nitrogen (30-200%) and their ratio (20-30%), carbon mineralization (11-67%), nitrogen mineralization (3-68%), respiration due to substrate (8-45%) and microbial enzymes activates to decrease in both regions (expect carbon and nitrogen mineralization in Paresar region). However, the metabolic coefficient (qCO2) in both regions increased due to land use change. Therefore, agricultural practices in forest lands cause oxygen availability to increase for soil microorganisms and this phenomenon stimulates the microbial activity and enhances organic matter decomposition and CO2-C emission from soil resulting in soil quality reduction. Also enhancement of carbon mineralization (microbial respiration), decreases soil organic matter concentration and reduces energy for microorganisms and this phenomenon caused soil microbial population to gradually decrease. According to the results it is recommended to reduce soil disturbance by using no-tillage or minimum tillage systems and planting perennial legumes can decrease greatly the harmful effects of cultivation.

This research was investigated to evaluate growth indices and competitive ability of two wheat (Triticum aestivum L.) cultivars in interference with two species of narrow and broad leaf weeds as two separated experiments based on a randomized complete block design with three replications at Agricultural Faculty of Bu-Ali Sina University, during 2008-2009. In both experiments, Alvand and Sayson cultivars were planted at 450 plants.m-2. In the 1st experiment, rye (Secale cereale L.) with densities of 0, 20, 40, 60 and 80 plants.m-2 were planted between wheat rows. In the 2nd experiment, wild mustard (Sinapis arvesis L.) with densities of 0, 8, 16, 24 and 32 plants.m-2 were planted. Results showed that increasing plant density in both weed species led to reduction of leaf area index, dry matter accumulation, crop growth rate, leaf area index duration, biomass duration, and yield of wheat cultivars. Mentioned traits and grain yield of Alvand showed less decrease in competition with both weed species. Sayson plant height was decreased with increasing weed density but such observation was not found in Alvand cultivar. Individual plant damage of wild mustard on two wheat cultivars was more than that of rye. Overall, Alvand compatibility against both weed species was more than Sayson.

In order to study the effect of flaming on seed viability of Sinapis arvensis L., changes in microorganisms population and physicochemical characteristics of soil after canola (Brassica napus L.) harvesting, an experiment was carried out based on randomized complete block design with four replications and eight treatments at Karaj Research Center, Iran, during 2005-2006. After harvesting canola at the end of spring, wild mustard seeds were distributed evenly on the surface of the soil. In some plots, canola stubbles were left on the ground and in some plots canola stubbles were taken off. Under this condition, the following treatments were applied: Flaming under wet and dry soil condition, burning stubbles under wet and dry soil condition. In other plots canola stubbles were taken off the plots and then flaming was applied under wet and dry soil conditions. Check plots did not receive any treatment. Results indicated that all treatments reduced seed viability, and the highest loss in seedling density occurred in the flaming treatment on dry-soil. Flaming did not have any serious effect on soil microorganisms or on its other physiochemical aspects, however dry-soil treatments proved the safest.

In this study tried to calculate attributed-based index and measurement of farmer’s attention to wheat (Triticum aestivum L.) seed environmental, cropping and marketing attribute and evaluate social- economical factors influencing on this index. After this estimation, effective factors have selected. Related data to 102 Mashhad wheat producers, Iran were used for estimations Poisson regression. Results showed that in seed characteristics set; marketability and taste were more important factors. Also, results of this study corroborant previews study and only variables age and family number make difference. Also, education, farming and non-farming income, farming experience, farm area and loan receive have positive effect on these characteristics.

In order to study the effect of intensity and exposure duration magnetic field on wheat (Triticum aestivum L.) seed germination an experiment was conducted in laboratory of Ferdowsi University of Mashhad, Iran. The experiment was including 11 treatments as three level of magnetic field intensities (pretreatment of seeds with 50, 100 and 150 mT magnetic field) and three exposure durations (10, 20 and 30 minutes), permanent magnetic field with intensity 3 mT and control. Results indicated that the lowest mean germination time (MGT) was found in 100 mT magnetic field with 20 min exposure duration. MGT was reduced by 43 percent in comparison to control at 100 mT magnetic field with 20 min exposure duration. In contrast the highest and the lowest germination rate was showed in 100 mT magnetic field with 20 min exposure duration and 150 mT magnetic field with all of the durations respectively. Magnetic treatments not affected on seed germination. Magnetic field stimulated shoot growth more than root growth. The highest shoot length was achieved in 100 mT magnetic field with 10, 30 and 20 min exposure duration and the lowest was shown in control. Magnetic treatments increased shoot length by 27 percent comparing to control. Magnetic treatments not affected shoot, root, seedling dry matter, and vigor index II. It seems that low magnetic field intensities had a simulative effect on germination traits whereas high intensities had a negative effect.

In order to study the effect of different organic fertilizers on quantitative and qualitative characteristics of fenugreek forage, an experiment was conducted based on completely randomized block design with six treatments and three replications at Agricultural Research Station, College of Agriculture, Ferdowsi University of Mashhad, Iran, during 2006. The experimental treatments were four organic fertilizers (40 t.ha-1 cow manure, 30 t.ha-1 sheep manure, 20 t.ha-1 hen manure, and 30 t.ha-1 compost), chemical fertilizer (250 kg.ha-1 ammonium phosphate+100 kg.ha-1 urea) and control (no-fertilizer).The results showed that there were no significant differences between different fertilizer treatments in terms of all quantitative and qualitative characteristics. However, the highest fresh forage yield (5618 kg.ha-1) and dry forage yield were obtained in using chemical fertilizer treatment. The highest leaf dry matter and organic matter digestibility and the lowest stem dry matter and organic matter digestibilities were produced in hen manure treatment. Chemical fertilizer treatment produced the lowest leaf dry matter and organic matter digestibility and the highest stem dry matter and organic matter digestibility. Generally, within studied fertilizers, chemical fertilizer had relatively higher effect on quantitative studied criteria.

In order to investigate the effect of seed rate on seed yield and yield components of three rapeseed varieties, a split-plot experiment was conducted in randomized complete block design with four replicates during 2008-2009 at Baykola Agricultural Research Station, Neka, Mazandaran province. In this experiment four seed rates (5, 7, 9 and 11 kg.ha-1) as main plots, three rapeseed cultivars (Hyola 401, RGS-003 and Sarigol) as sub plots were assessed. Each plot was included six lines with five meter length and distance between lines was 30 cm. Results showed that the effect of seed rates on seed yield and number of pods per plant was significant. The highest grain yield (4829 kg.ha-1) was related to the lowest seed rates. The effect of varieties on the secondary branch number, 1000-seed weight of pods per plant and seed yield were significant. Hyola 401 with 5033 kg.ha-1 was performed better than RGS-003 and Sarigol (PF) with 4357 and 4066 kg.ha-1 seed yield, respectively. Significant positive correlation of seed yield with 1000-seed weight, number of pods per plant, number of seed per pod indicating that Hyola 401 with highest yield components at the different plant density had the highest seed yield.

In order to investigate the effects of seed inoculation with plant growth promoting rhizobacteria (PGPR) on germination components and seedling growth of corn (Zea mays L.), a factorial experiment based on randomized complete block design with three replications was conducted at the seed technology laboratory of Mohaghegh Ardabili University, Iran, during 2008. Studied factors were: corn cultivars in four levels (SC-434, Kenez, DC-370 and SC-301) and seed inoculation with plant growth promoting rhizobacteria in three levels (no inoculation, seed inoculation with Azetobacter chorchorum strain 5, Azosprilium lipoferum strain OF). The results showed that seed inoculation with PGPR had significant effect on growth seedling, uniformity of germination, Radicle and plumule dry weight, germination percentage of corn. Cultivars had different response to germination indices and seed inoculation with plant growth promoting rhizobacteria. Seed inoculation with PGPR increased germination indices. Seed inoculation with Azosprilium lipoferum strain OF increased proportion of radicle to plumule, longer radicle and plumule compared with inoculation with Azetobacter chorchorum strain 5 and no inoculation. Thus, in order to increasing of germination indices and seedling growth, it can be suggested that seeds inoculation of SC-434 was applied with Azosprilium lipoferum strain OF.

Having special ecological condition, Kish Island has a restricted range of native species of ornamental plants. Expansion of urban green space in this Island is great of importance due to its outstanding touristy position in the South of Iran. The purpose of this study was to investigate the growth and development of groundcover plants planted in four different regions of Kish Island and to recommend the most suitable and adaptable species for each region. Ten groundcover species included Festuca ovina L., Glaucium flavum Crantz., Frankenia thymifolia Desf., Sedum spurium Bieb., Sedum acre L., .Potentilla verna L., Carpobrotus acinaciformis (L.) L. Bolus., Achillea millefolium L., Alternanthera dentata Moench. and Lampranthus spectabilis Haw. Evaluation of growth and development had been made by measurement of morphological characteristics such as height, covering area, leaf number and area, dry and fresh total weights and visual scoring. Physiological traits included proline and chlorophyll contents evaluated. This study was designed in factorial layout based on completely randomized blocks design with six replicates. Results showed that in terms of indices such as covering area, visual quality, height, total weight, and chlorophyll content, Pavioon and Sadaf plants had the most and the worst performances, respectively in comparison to other regions’ plants. Based on evaluated characteristics, C. acinaciformis, L. spectabilis and F. thymifolia had the most expansion and growth in all quadruplet regions and are recommend for planting in Kish Island and similar climates.

Water and nutrient availability are two major constraints to forage maize production in arid and semi-arid areas; however, the effect of different N levels from organic and inorganic sources on nutrient (i.e., N and P) efficiency under drought stress conditions is not well known for maize faming. Thus, a field study was conducted with the objective of determining the effect of N fertilization and drought stress on N and P efficiencies in maize (cv. SC 704) crop. The experimental setting consisted of four rates of N application (0, 100, 200 and 300 kg.ha-1 N) as urea and broiler litter and two irrigation regimes (full irrigation and irrigation stop at tasseling stage lasted only for two weeks) that carried out at the Research Station of Agricultural Faculty, Shahrekord, Iran, during 2008-2009. Results indicated that no significant difference in N and P efficiencies between the two irrigation regimes. Although the effects of fertilizer treatments on N agronomic efficiency, N physiological efficiency, P agronomic efficiency and aboveground dry matter were significant, but N and P recovery efficiencies and P physiological efficiency were not significantly affected by N treatments. The highest aboveground dry matter (32289 kg ha-1) and N agronomic efficiency (62.7 kg.kg-1) were observed with 300 kg.ha-1 N from broiler litter, but this efficiency did not differ from all urea N levels. The application of 100 kg.ha-1 N from broiler litter resulted in the greatest N and P physiological efficiencies (141 and 114 kg.kg-1, respectively) and these efficiencies were significantly different from all urea N levels. It is concluded that broiler litter application have had higher N agronomic and physiological efficiencies than urea application, and that short-term drought stress at tasseling stage apparently does not have an influence on the response of nutrient efficiencies to different N rates and sources.