Showing 67 results for Growth
Z Daneshvar Ran, M Esfahani, M Payman, M Rabiei, H Samie Zadeh,
Volume 12, Issue 46 (1-2009)
Abstract
The effects of tillage methods and residual management on yield and yield components of rapeseed (Brassica napus L. CV. Hyola308) were evaluated after rice harvest. The experiment was carried out during 2004-2005 cropping season in a factorical arrangement of treatments at Rice Research Institute of Iran (RRII) in Rasht, in a Complete Randomized Block Design with three replications. Treatments included tillage in three methods: a) conventional tillage b) minimum tillage, and c) no tillage, and rice residue management in two manners: a) removing residues, and b) not removing residues. Plant traits such as grain yield, oil percentage and yield, plant density, plant height, the lowest pody branch height from soil surface, number of pods per plant, plant and weed dry weight, leaf area index (LAI) and crop growth rate (CGR) were measured. Results indicated that grain yield was affected by the tillage type. Also, the effect of tillage type on plant height, number of pods per plant, the lowest pody branch height from soil surface, and oil yield was significant. The effect of residual management and residual management interaction and tillage were significant on none of the traits except for weed dry weight. Economic analysis indicated that rapeseed planting in a field with rice residual and minimum tillage had a relative advantage of less production cost in spite of nearly 15 percent yield decrease compared to other methods.
M Hojati, N Etemadi, B Bani Nasab,
Volume 13, Issue 47 (4-2009)
Abstract
This study was conducted to evaluate the effects of paclobatrazol and cycocel on some quantitative and qualitative traits of zinnia. Seedlings were transplanted on Horticulture Department Farm , College of Agriculture, Isfahan University of Technology. The experiment was carried out in the framework of randomized complete block with 3 replications. Triats which were studied included plant height, leaf and flower number, lateral shoot number, flower diameter, lateral shoot lenght, leaf chlorophyl content, the period of the flowering, root fresh and dry weight, leaf area, root number, diameter and length, root and shoot carbohydrate. Results showed that cycocel at 1000 and 2000 ppm reduced height. Cycocel 2000ppm caused most lateral shoot and flower number and the lowest lateral shoot length. The lowest root fresh and dry weight, root number and length and shoot carbohydrate were obtained by cycoel 2000 ppm. Paclobutrazel at 30ppm resulted in the most leaf chlorophyl content. There were no significant differences between treatments related to the period of the flowering, flower diameter, leaf number and area, root diameter and carbohydrate.
A Esfahani, A Hoseyn Zade, J Asghari, M Naghizadeh, B Rabiee,
Volume 13, Issue 48 (7-2009)
Abstract
In order to evaluate the effects of sulphur fertilizer sources and amounts on growth indices and yield of peanut (Arachis hypogaea L. CV. NC2), a field experiment was conducted in Bandar Kiaashahr, Guilan province, Iran in 2004. The experiment was laid out in a factorial arrangement with two factors including sulphur sources (gypsum and single super phosphate) and sulphur rates (0, 30, 60 and 90 kg.h-1) in a completely randomized block design with three replications. Results showed that sulphur application greatly enhanced peanut growth and yield. The application of 90 kg.h-1 sulphur (in both forms) performed significantly better than the rest. The highest pod yield and grain yield were obtained in 90 kg.h-1 sulphur in gypsum form (6400 and 5200 kg.h-1, respectively). The highest LAI (6.6), CGR (20.2 g.m-2.12GDD-1) and PGR (16 g.m-2.12GDD-1) were obtained in 90 kg sulphur in the form of gypsum after 1142, 1142 and 1289 of accumulation, respectively. According to the results of the present experiment, it could be concluded that sulphur may considerably increase peanut grain yield and yield components. Thus, it could be expected that the application of 90 kg sulphur per hectare in the form of gypsum may result in better growth indices and higher grain yield of peanut.
A Esmaeili, F Nasrnia,
Volume 13, Issue 48 (7-2009)
Abstract
Deforestation has been recognized as one of the biggest environmental problems in the world. It is also one of the main elements of land productivity changes and one of the biggest factors which threaten world's environmental diversity. In this study, based on environmental Kuznets theory, factors which may affect deforestation have been investigated. Results obtained from 71 studied countries show that environmental Kuznets curve was not true for them. Population growth helps the speed of deforestation while higher rate of GDP growth decreases its rate. Institutions which help with the improvement of democracy, individual assets, civil right and political liberty can decrease the pressure on natural recourses and deforestation.
Z Taraz, B Dastar,
Volume 13, Issue 48 (7-2009)
Abstract
This experiment was conducted to compare the effects of Roxarsone (Rox) and Bacitracin methylen disalicylat (BMD) on the performance of broiler chicks. A control corn-soybean meal diet without growth promoter was formulated according to NRC (1994) recommendation for starter (0-21d) and grower (22-42d) periods. The control diet was also supplemented with Rox (50 mg/kg diet ) BMD (55 mg/kg diet) as well as the combination of Rox (50 mg/kg diet ) and BMD (55 mg/kg diet) in order to prepare 4 dietary treatments. Five replicate groups of 15 Ross 308 broiler chicks were assigned to each dietary treatment. Data was analyzed in a completely randomized design. Results of experiment indicated that individual supplementing of diet with Rox as well as BMD led to improved body weight gain and feed conversion ratio compared to the basal diet. However, those birds fed diet containing the combination of these two compounds had significantly higher body weight gain and lower feed conversion than other groups ( P<0.05 ). Neither Rox nor BMD had any significant effect on feed intake. Birds fed diets supplemented with Rox or BMD had better carcass composition than those fed Basal diet. Based on the present results, supplementing broilers diets with Rox leads to improved body weight gain and feed conversion ratio in broilers. However, supplementing broiler diets with combination of Rox and BMD has a more positive effect on the performance and carcass composition in broiler chicks.
H.r. Memari, E. Tafazoli, A. Kamgar-Haghighi, A. Hassanpour, N. Yarami,
Volume 15, Issue 55 (4-2011)
Abstract
Many experiments have been carried out to decrease the negative effect of drought stress and obtain suitable growth under water deficit conditions. Application of plant growth regulators (especially growth retardants) is one of the proposed methods. This study was conducted to investigate the effect of Cycocel application on growth of two olive cultivars (Shengeh and Roghani) under water stress condition. The design of experiment was completely randomized with six replications (Factorial arrangement). Treatments included irrigation intervals (2, 4, 6, 8 weeks) and Cycocel concentrations (0, 500,1000,2000,4000 mg per litter). Some indices such as height, chlorophyll, leaf area, root, and shoot weight (fresh and dry) were measured. Results indicated that interaction of C.C.C treatment and irrigation intervals on height of olive cultivars was not significant, probably due to the response of these cultivars to concentrations of C.C.C. Although drought stress decreased the number of leaves in both cultivars, the application of CCC (500 mg per litter) thwarted the adverse effects of drought stress. Cycocel increased chlorophyll content significantly (500 mg per litter in Roghani and Shengeh and 6 weeks irrigation interval). Cycocel application decreased leaf area, but in Shengeh cultivar increased leaf area in 6 week irrigation interval. Overall, the results indicated that the application of Cycocel with concentration of 500 mg per litter in 6 week irrigation intervals in both cultivars (Roghani and Shengeh) was the best treatment for controlling the adverse effects of drought. Also, results indicated that such changes were dependent on Cycocel concentration and drought level.
M. H.nazarifar, R. Momeni,
Volume 15, Issue 56 (7-2011)
Abstract
Deficit irrigation is one of the strategies used to obtain products with maximum profits in recent years. In this context, research on determining appropriate levels of deficit irrigation is essential. Since determining the different levels of performance through field experiments is difficult, the use of simulation models is a strategy through which we can examine the water balance data, simulate the growth process, and to study different managerial scenarios. The purpose of this study was validation and evaluation of CropSyst, a plant growth model, to determine suitable cropping patterns in deficit irrigation conditions. Applying three deficit irrigation scenarios in model, with values of 10%, 20% and 30% on six crops, fava bean, bean, wheat, potato, sunflower and rice, we concluded that the applied deficit irrigation of 10% to bean, potato and beans, 20% to sunflower and 30% to wheat had been suitable, and it is better not to apply deficit irrigation in rice. Also, since in final selection, the rate of water productivity is one of the basic criteria in each crop mentioned above, determining net benefit based on drop index (NBPD) per cubic meter showed that the most NBPD is related to bean with 6853 Rials per cubic meters and the lowest amount is related to sunflower with a value equal to 2809 Rials per cubic meters.
M. Rahmanian, H. Khodaverdiloo, M. H. Rasouli Sadaghiani, Y. Rezaie. Danesh, M. Barin,
Volume 15, Issue 58 (3-2012)
Abstract
Arbuscular mycorrhizae (AM) and Plant Growth Promoting Rhizobacteria (PGPR) associations are integral and functioning parts of plant roots. These associations have a basic role in root uptake efficiency as well as improvement of plant growth in degraded environments including heavy metals contaminated soils. This study was conducted to evaluate the effects of heavy metal-resistant soil microbe's inoculation on bio-availability of Pb and Cd in soil, plant growth as well as metal uptake by Millet (Pennisetum glaucum), Couch grass (Triticum repens) and wild alfalfa (Medicago sativa). A soil sample was treated by different levels of Pb and Cd (soil 1). Native microbial inoculums were obtained from alfalfa rhizosphere soils adjacent to Pb and Cd mines in Zanjan region (soil 2), then added with weight ratio of 1:5 (w/w) to soil 1. Host plants including millet, couch grass, and alfalfa were grown in pots and kept in greenhouse conditions. At the end of growing period, shoot dry matter and Pb and Cd concentrations in plant and soil were measured. Results indicated that plants yield and Pb uptake were significantly higher in non-inoculated treatments (p ≤ 0.05). However, Cd uptake by plants was greater in inoculated treatments (p ≤ 0.05). Couch grass showed the most accumulation potential of Cd and Pb among the studied plants.
M. Navabian, M. Aghajani,
Volume 16, Issue 60 (7-2012)
Abstract
In Guilan province, Sefidrud River, as the main source of irrigating rice in Guilan province, has been subjected to increasing salinity and a decreasing discharge because of decreasing in the volume of sefidrud dam, diverting water upstream and entering different sewages into the river. This research tries to determine optimum irrigation depth and intermittent periods in proportion to salinity resistance at different growth stages using optimization- simulation model. After calibration, Agro-hydrological SWAP model was used to simulate different growth stages of rice. Optimization results were obtained for managing fresh and saline intermittent water, 8-day intermittent period, for salinity of 0.747 dS/m in sensitive maturity stage and salinity of 3.36 dS/m in resistant vegetative, tiller and harvest growth stages. It is suggested that the depth of irrigation water be 1, 3, 3 and 5 cm for vegetative, tiller, maturity and harvest stages, respectively. Comparing managements of irrigation and saline based on the resistance of different growth stages to salinity and exploitation of irrigating water with a constant salinity during growth periods of the plant showed that irrigation management based on resistance of different growth periods of the plant to salinity causes rice yield to be improved by 23percent.
Y. Habibzadeh, M. R. Zardoshti, A. Pirzad, J. Jalilian,
Volume 16, Issue 60 (7-2012)
Abstract
To evaluate effect of different irrigation regimes and mycorrhizal fungi on the growth and yield of mungbean NM92 [Vigna radiata (L.) Wilczk], a field experiment was conducted in split plot arrangements using randomized complete block design (Irrigation after 50, 100, 150 and 200 mm evaporation from pan class A as main plots and mycorrhiza species, Glomus mosseae, G. intraradices and a non-inoculated treatment as sub-plots) with three replications at the Research field of Urmia university in 2009. Results showed that irrigation after 50mm evaporation from pan class A, and plant inoculated with G. intraradices produced the highest grain yield (1678.5 kg/ha and 1537.6 kg/ha, respectively), total dry weight, leaf dry weight, leaf area index, crop growth rate, relative growth rate and net assimilation rate. In Contrast, irrigation after 200 mm evaporation from class A pan and non-inoculated treatment produced the lowest grain yeild (1159.2 and 1301.9 kg/ha, respectively). Reducing the irrigation distance led to an increase in total dry weight, leaf dry weight, leaf area index, crop growth rate, relative growth rate and net assimilation rate. Despite lower grain yield in water deficit condition, AM fungi inoculation significantly reduced the effect of stress on grain yield. All inall, both mycorrhizae species significantly (P 0.05) increased the grain yield of mungbean under well-watered and water deficit conditions
H. Alinezhad Jahromi, A. Mohammadkhani, M. H. Salehi,
Volume 16, Issue 60 (7-2012)
Abstract
Nowadays, due to drought and water shortage, use of unconventional waters, particularly sewage, has become usual in agriculture whereas they often contain heavy metals. The present study was employed to evaluate the effect of urban wastewater of Shahrekord on growth, yield and accumulation of heavy metals (lead and cadmium) in balm (Melissa officinalis) as a medicinal plant with five treatments (0, 25, 50, 75 and 100 percent wastewater) and three replications in a completely randomized experimental design. The results showed that the highest shoot length, stem diameter and stem number, number of leaves and tillers are achieved in the treatment of 100 percent. The wet and dry weight of shoots and roots was highest in 100 % of wastewater. Oil percentage of the leaves was also the highest amount (1.23 %) in 100 % of wastewater. Accumulation of lead in roots and aerial parts and its transmission factor was not significant for the treatments. However, the highest concentration of lead in root (0.057 mg/kg) and shoots (0.013 mg/kg) was observed in 100 % of wastewater and the lowest one was related to zero percent of wastewater treatment. The lead concentration was less than the critical limit for all the treatments. The amount of cadmium was undetectable in all the plant samples. The results of this study demonstrated that urban wastewater of Shahrekord, in addition to providing water, increases plant growth and essential oil.
S. Eskandari , V. Mozafari,
Volume 16, Issue 60 (7-2012)
Abstract
A greenhouse experiment was conducted to study the effects of soil copper (Cu) and salinity on growth and chemical composition of two pistachio cultivars. A factorial experiment was carried out as a completely randomized design with three replications. Treatments consisted of four Cu levels (0, 2.5, 5, and 7.5 mg Kg-1soil as CuSO4.2H2O), five salinity levels (0, 800, 1600, 2400, and 3200 mg NaCl Kg-1 soil) and two pistachio cultivars (Badami-e-Zarand and Ghazvini). Results showed that salinity significantly decreased growth parameters. Application of 3200 mg NaCl Kg-1 soil decreased shoot and root dry weights, leaf area and stem height by 67, 72, 45 and 76 % respectively. Application of 7.5 mg Cu Kg-1 soil increased shoot dry weight and leaf area by 24 and 26% respectively. Morever, there was no significant difference between growth parameters of two pistachio cultivars, except for leaf area index. Salinity stress significantly decreased shoot and root P, k and Cu total uptake, and increased that of Na and Cl. Application of 5 mg Cu Kg-1 soil significantly increased shoot Cu uptake. Since total uptake of all elements for Badami cultivar was significantly higher than the Ghazvini, it could be concluded that the latter cultivar is probably more resistant to the saline conditions.
N. Besharat, A. Tajabadi Pour, V. Mozafari,
Volume 18, Issue 67 (6-2014)
Abstract
To study the effects of soil phosphorus (P) application on growth and water relations and nutrient concentration of pistachio seedlings (Badami-e-Zarand) under water stress, a greenhouse experiment was conducted. Treatments were arranged in a factorial manner as a completely randomized design with three replications. Treatments consisted of six P levels (0, 30, 60, 90, 120 and 150 mg P Kg-1 soil as H3PO4) and three irrigation intervals (2, 4 and 8 days). Results showed that as water stress increased, growth parameters significantly decreased. As irrigation interval was increased to 8 days, shoot and root dry weights, shoot/root ratio, leaf area and leaf number and stem height decreased. Photosynthesis parameters were significantly decreased by increasing water stress. Also, P and Zn concentrations decreased as irrigation interval increased. Analysis of variance indicated that P application had no significant effect on growth parameters, transpiration rate and photosynthesis. It seems that Olsen extractable P (5.35 mg kg-1 soil) was sufficient for optimum growth of pistachio seedlings and thus, no growth responses were observed from P application in this experiment. Application of phosphorus significantly increased P and decreased Zn concentrations.
Mh. Rasouli-Sadaghiani, S. Ejlali , S. Ashrafi Saeidlou,
Volume 19, Issue 73 (11-2015)
Abstract
Earthworms are an important component of soil fauna because of their fundamental impact on soil physical, chemical and biological properties. To evaluate the effects of earthworms on some soil chemical properties as well as plant growth indicators, an experiment was carried out in a completely randomized design in greenhouse conditions. The first factor involved the presence or absence of earthworms (Eisenia foetida), the second factor was different organic matter including control (no organic materials), pruning waste compost of apple and grape (PWC), wheat straw (WS), Herbal extracts waste (HE), pruning waste (PW) and the third factor was the presence or absence of corn plant for evaluating rhizosphere soil. At the end of growing period, some soil chemical properties including total nitrogen, organic carbon, ammonium, nitrate and plant growth indicators were measured. The results showed that application of organic matter and earthworm inoculation had significant effects on soil chemical properties. The pruning waste compost (PWC) treatment showed the largest impact on ammonium and nitrate content (1.7 and 3.3 times compared to control treatment, respectively). In pruning waste compost (PWC) treatment, organic carbon amount in rhizospheric soil increased from 0.9 at non-rhizosphere to 1.32 %. The presence of earthworm improved plant growth parameters including shoot and root dry weight by 34% and 30%, respectively, compared to earthworm absence condition. Soil ammonium and nitrate contents at earthworm presence increased 32% and 49%, respectively. Therefore, application of organic matter with earthworm inoculation had better results in comparison with no earthworm inoculation.
H. R. Eshghizadeh, M. Kafi, A. Nezami, A. H. Khoshgoftarmanesh, M. Karami,
Volume 19, Issue 73 (11-2015)
Abstract
This study was conducted to determine some mineral content concentrations in soils and plants of three elevation classes (1500, 2200 and 3000m) and two phenological stages of flowering and seedling in north facing slopes of Sabalan rangelands. Soil samples from the depth of 20cm and plant samples using 1×1m plots with 10 replications were collected. After sample preparation, the concentrations of minerals such as calcium, phosphorous, sodium, potassium, ion, copper, zinc and magnesium were determined using spectrophotometer and flame photometer. Data was analyzed by SAS9.1 software using a Completely Randomized Design with a Generalized Linear Model procedure. Results showed that elevation had a significant effect on Ca, Fe, Cu, Zn and Mn of soil and P, Na, K, Mg and Mn of plants in the study areas (P&le0.05). Growing stages had a significant effect on all elements of plants except Ca (P&le0.05). Moreover, results showed that in three elevation classes the high demand minerals' concentrations were higher at the starting seedling stage in comparison with the flowering stage. In contrast, the low demand minerals' concentrations in three elevation sites were higher in the flowering stage in comparison with seedling stage. Interaction effect of elevation and growing stage was also significant in relation to all elements except Ca (P&le0.05).
R. Valizadeh Yonjalli, F. Mirzaei Aghjehgheshlagh, A. Ghorbani,
Volume 19, Issue 73 (11-2015)
Abstract
This study was conducted to determine some mineral content concentration in soil and plant of three elevation classes (1500, 2200 and 3000m) and two phenological stages of flowering and seedling start in north-facing slopes of Sabalan rangelands. Soil samples from the depth of 20cm and plant samples using 1×1m plots with 10 replications were collected. After sample preparation, the concentrations of minerals such as calcium, phosphorous, sodium, potassium, ion, copper, zinc and magnesium were determined using spectrophotometer and flame photometer. Data was analyzed by SAS9.1 software using Completely Randomized Design with a Generalized Linear Model procedure. Results showed that elevation had a significant effect on Ca, Fe, Cu, Zn and Mn of soil and P, Na, K, Mg and Mn of plants in the study areas (P&le0.05). Growing stages had a significant effect on all elements of plants except Ca (P&le0.05). Moreover, results showed that in three elevation classes the high demand minerals’ concentration was higher at the starting seedling stage in comparison with the flowering stage. In contrast, the low demand minerals’ concentration in three elevation sites was higher in the flowering stage in comparison with seedling stage. Interaction effect of elevation and growing stage was also significant in relation to all elements except Ca (P&le0.05).
M. H. Rasouli0-Sadaghiani, H. Khodaverdiloo, M. Barin, S. Kazemalilou,
Volume 22, Issue 1 (6-2018)
Abstract
The use of plants and soil microorganisms is a promising technique for the phytoremediation of heavy metal-contaminated soils. This study was carried out in order to evaluate the soil microbial potential with four Cd concentration levels (0, 10, 30 and 100 mg kg-1); the study also addressed the inoculation of arbuscular mycorrhizal fungi (AMF) species (a mixture of Glomus species including G. intraradices, G. mosseae and G. fasciculatum) as well as plant growth promoting rhizobacteria (PGPR) (a mixture of Pseudomonas species including P. putida, P. fluorescens, and P. aeruginosa) with the Centaurea cyanus plant. The soil sample was spiked uniformly with Cd nitrate salt to create different Cd concentrations. The contaminated soils were then sterilized and subsequently inoculated with AMF and PGPR. The results indicated that with increasing the soil Cd concentration, colonization percent, abundance of rhizobateria, shoot biomass, and shoot relative biomass were significantly decreased, while the proline content and the shoot Cd concentration were significantly increased (P≤0.05). The mean of Cd extracted in AMF and PGPR treatments was 1.8 and 2.8 and the translocation factor was 1.2 and 1.5 times higher, as compared to the corresponding control treatments, respectively. It could be concluded that microbial inoculation, in addition to improving plant growth, plays an important role in the Cd phytoremediation efficiency by plant.
M. Jahan, B. Amiri,
Volume 22, Issue 3 (11-2018)
Abstract
Factor analysis is one of the multivariate statistical techniques that considers the interrelationships between apparently irrelevant variables and helps researchers to find the hidden reasons for the occurrence of an event. In order to evaluate the effects of different irrigation levels and humic acid foliar application and identify the factors affecting water use efficiencies of sesame (Sesamum indicum L.), maize (Zea mays L.) and common bean (Phaseolus vulgaris L.), a split plots experiment based on RCBD design with three replications was conducted during the 2014-15 growing season, at the Research Farm of Ferdowsi University of Mashhad, Iran. Irrigation levels (50 and 100% of water requirement) and foliar application and non-application of humic acid were assigned to main and sub plots, respectively. The results showed that in sesame, the highest seed yield and biological yield were obtained from 100% of water requirement and humic acid spraying treatment. In maize, humic acid spraying under condition of supplying 50% of water requirement increased seed weight per plant, plant height, and leaf area index and soil pH In bean, the highest seed weight per plant, plant height, leaf area index, crop growth rate and soil phosphorous content were observed in the treatment of 100% of water requirement and humic acid spraying. Factor analysis results also showed that in sesame, the variables of seed yield, biological yield, seed weight per plant, plant height, leaf area index, crop growth rate, soil phosphorous and water use efficiency were assigned to the first factor and the variables of soil nitrogen, soil pH and EC were assigned to the second one. In maize, seed yield was assigned in the same group with the variables of biological yield, leaf area index, crop growth rate, soil phosphorous, EC and pH and water use efficiency; in bean, this was with the variables of seed yield and water use efficiency. In general, the research results revealed that identifying the effective variables in each factor and those logical nominations according to Eco physiological knowledge can lead to the direct management of effective variables with regard to associated factor, thereby leading to water efficiency improvement.
O. Asadi Asadabad, S. H. Matinkhah, Z. Jafari, H. Karim Mojeni,
Volume 25, Issue 1 (5-2021)
Abstract
In order to investigate the effect of the type drip of irrigation methods, subsurface irrigation and furrow irrigation on the domestication of Hedysarum criniferum Boiss., an experiment with a randomized complete block design with three replications was implemented at Isfahan University of Technology for two years (2016 to 2018) . For this purpose, clay pipes were made and the plant was cultivated on the sides of clay pipes and types. Also, furrow irrigation treatment was applied as the control. During the experiment, all treatments received the same water and finally, some growth parameters were measured. The results of the study showed improvement in height (0.43 and 0.34), canopy cover (0.66 and 0.52), stem number (0.44 and 0.85), chlorophyll index (0.45 and 0.45), seed emergence (0.75 and 0.30), plant survival (0.78 and 0.55), yield (0.23 and 0.35), and water use efficiency (0.25 and 0.25) under type drip irrigation treatment, as compared to subsurface and furrow irrigation, respectively (P<0.05). In general, the type drip treatment is recommended in the early years of planting; however, since the maximum production potential of this plant is in the third year onwards, it is necessary to examine the results in the following years to recommend the proper irrigation method, especially the use of subsurface irrigation.
S. Parvizi, S. Eslamian, M. Gheysari, A.r. Gohari, S. Soltani Kopai, P. Mohit Esfahani,
Volume 26, Issue 3 (12-2022)
Abstract
Investigation of homogeneity regions using univariate characteristics is an important step in the regional frequency analysis method. However, some hydrological phenomena have multivariate characteristics that cannot be studied by univariate methods. Droughts are one of these phenomena their definition as univariate will not be effective for risk assessment, decision-making, and management. Therefore, in this study, the regional frequency analysis of drought was studied in multivariate methods using SEI (Standardized Evapotranspiration Index), SSI (Standardized Soil Moisture Index), and SRI (Standardized Runoff Index) indices in the Karkheh River basin from 1996 to 2019. The indices calculated probabilistic distribution between the variables of evapotranspiration, runoff, and soil moisture using multivariate L-moments method and Copula functions and considered meteorological, agricultural, and hydrological droughts simultaneously. The results of multivariate regional frequency analysis considering the Copula Gumbel as the regional Copula showed that the basin is homogeneous in terms of severity of SEI-SSI combined drought indices and is heterogeneous in terms of severity of SEI-SSI combined drought indices. However, after clustering the basin into four homogeneous areas in terms of characteristics of SPI (Standardized Precipitation Index), the basin is homogeneous in all areas in terms of univariate SEI, SSI, and SRI indices and is heterogeneous in the third and fourth clusters of SRI and SSI drought indices. Pearson Type (III), Pareto, normal, and general logistics distribution functions were found suitable to investigate the characteristics of SEI, SSI, and SRI drought indices in this case. Finally, large estimates of the types of combined droughts and their probability of occurrence showed that the northern and southern parts of the Karkheh River basin will experience short and consecutive droughts in the next years. Droughts in areas without meteorological data can be predicted in terms of joint probability using the multivariate regional frequency analysis method proposed in this study.
