Research Article
MohammadAmin Amini; Ghazaleh Torkan; Saeid Eslamian; Mohammad Javad Zareian; Ali Asghar Besalatpour
Abstract
Introduction: Understanding the concept of water balance is one of the most important prerequisites for sustainable management of water resources in the watersheds. Therefore, the components of water resources in a catchment system should be compared at different time periods, and also the effect of ...
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Introduction: Understanding the concept of water balance is one of the most important prerequisites for sustainable management of water resources in the watersheds. Therefore, the components of water resources in a catchment system should be compared at different time periods, and also the effect of each of them should be identified on varied hydraulic components of the hydrological systems. The SWAT model is an example of a physically based hydrologic model which can be used for large-scale simulating and monitoring of water cycle processes based on the characteristics of the catchment area and its climatic conditions. The main object of this study is the hydrologic simulation and water balance estimation for the period 2000-2009 in the Zayandeh-Rud River Basin.
Materials and Methods: The Zayandeh-Rud River Basin is located in the arid and semi-arid central region of Iran. This area is very variable in terms of rainfall. As well as the state of water resources and water consumption is very complicated in this catchment. In the present study, the soil and water assessment tool (SWAT) used to simulate water balance in the Zayandeh-Rud River Basin. The input required data included digital elevation model, land use map, soil texture map and meteorological information including daily rainfall data and minimum and maximum temperature data were introduced to the model and the model was implemented with these data. The sensitivity of the flow-effective parameters was determined using the p-value and t-state criteria by the SUFI2 algorithm in the SWAT-CUP program. The model was calibrated monthly and validated with the selected parameters in the sensitivity analysis using the Nash-Sutcliff criteria and the coefficient of determination by the application of the data of six stations including. Calibration of the model was conducted for 2000-2006 and validation of the model for the years 2007-2009.
Results and Discussion: The results of sensitivity analysis showed that considering the characteristics of the study area, the SWAT model is more sensitive to the 17 effective parameters on runoff. The selected parameters also confirm the results of previous research carried out in the region. The sensitive parameters selected in the sensitivity analysis step were used to calibrate the model. In the next step, the parameters of SWAT-CUP software were entered. After that, these parameters were repeated 1000 times with the SUFI2 algorithm, and the optimal value for each parameter was determined. The Nash-Sutcliff coefficient and the coefficient of determination in the six hydrometric stations are greater than 0.56 and 0.69 in calibration and verification periods respectively, which indicates that the model has a satisfactory ability to run in runoff simulation. The contribution of the components of the water balance including evapotranspiration, surface runoff, lateral flow, groundwater flow, and deep aquifer recharge was calculated from annual basin precipitation. The amount of extracted water from the hydrological components indicated that the largest share of the water balance was related to actual evapotranspiration, the range of variations in the type of precipitation in the study area ranged from 60.1% (2000) to 92.7 % (2007). After evapotranspiration, surface runoff with a change of 22.2% (2005) to 8.6% (2009) and groundwater flow with a change of 14.2% (2000) to 20.5% (the year 2007) had relatively high fluctuations and a large share in the basin balance. These results indicate that the lateral flow with a range of 3.1 to 1.9% had no significant change in these years. Also, the deep aquifer recharge with the range of 1.2 to1.5% was the lowest in 2003 and 2009, respectively.
Conclusion: The results showed that the calibrated model for the Zayandeh-Rud River Basin had a desirable performance for both calibration and validation periods. Therefore, the SWAT model has acceptable performance for simulating the water balance of the area. In addition, the results of this study showed that 65.98% of the total annual precipitation in the basin is in form of evapotranspiration, which compares to the other water balance components has the highest part. As well as surface runoff with 15%, groundwater flow with 13.7%, lateral flow with 1.5%, and deep aquifer recharge with 0.8% have other parts of the water balance components in Zayandeh-Rud River Basin. The results also indicate that the highest water losses in the soil and groundwater resources of the basin are due to evapotranspiration. Therefore, serious measures to prevent the loss of water through evapotranspiration in the region to be necessary. The results of this research can be used to predict the effects of climate change and the applicable management practices in the region, which are presented in scenarios to the model.
Research Article
reza saeidi; abbas Sotoodehnia; Hadi Ramezani Etedali; Bizhan Nazari; Abbas Kaviani
Abstract
Introduction: Estimating the actual evapotranspiration of the crops, is so important for determining the irrigation needs. Typically, the climatic, vegetative and management parameters are effective on actual evapotranspiration. If the crops are exposed to salinity, fertility and other stresses, reduce ...
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Introduction: Estimating the actual evapotranspiration of the crops, is so important for determining the irrigation needs. Typically, the climatic, vegetative and management parameters are effective on actual evapotranspiration. If the crops are exposed to salinity, fertility and other stresses, reduce actual evapotranspiration and yield. The correct estimation of the actual evapotranspiration of crop will allow agricultural planners to the better agricultural water management. Previous researches show water stress and soil nitrogen deficiency (as management stresses), effect on increasing of stomatal resistance and reducing of crops evapotranspiration. Thus, goal of this study was to investigate the effect of salinity and soil nitrogen deficiency on the amount of Ks coefficient and readily available water of maize.
Materials and Methods: This study was conducted in research farm at University of Imam Khomeini International, Qazvin, Iran during June to November 2017. In this research, the effects of saline water and soil nitrogen deficiency on Maize (SC 704) evapotranspiration, were investigated. The applied treatments included irrigation with saline water (in four levels: 0.5 (S_0), 1.2 (S_1), 3.5 (S_2) and 5.7 (S_3) dS/m) and soil fertility (in four levels: nitrogen fertilizer consumption at 100 (N_0), 75 (N_1), 50 (N_2) and 25% (N_3)). The experimental design used in this research was a completely randomized block design with three replications. In this experiment, maize seeds were cultivated in the plots with Length and width of 3×3 meters. The prometer device (Model: AP4) was also used to measure stomatal resistance of maize leaf. Determining the irrigation schedule, was based on the soil moisture reached to the limit of RAW (Readily Available Water). At the same time, with increasing stomatal resistance, RAW was calculated and irrigation was done. Evapotranspiration of the under stress plants were ET_(c-adj) and evapotranspiration of S_0 N_0 treatment was ET_c. The stress factor (K_s ) is calculated by ET_(c-adj)/ET_c. The values of RAW and K_s were analyzed by SPSS software. K_s coefficient was modeled with amounts of salinity stresses and soil nitrogen deficiency.
Results and Discussion: The results of this study showed that the interaction between two factors of salinity stress and nitrogen deficiency on the K_s and RAW parameters (in level: 1%) are significant. K_s coefficient at the levels of S_1, S_2 and S_3, were 0.95, 088 and 0.77, respectively. In saline water of 0.5 (dS/m), the K_s coefficient of N_1, N_2 and N_3 were 0.98, 0.96 and 0.95, respectively. With increasing the 1(dS/m) salinity of water and 25% reduction in nitrogen consumption, decreased the K_s amount about 4.5% and 1.7%, respectively. The reason of results is that with increasing of water salinity, decreases the osmotic potential of water in the soil and the crop needs to consume more energy to obtain water. Thus, amount of crop transpiration is reduced and soil water content is remained. The linear, exponential, logarithmic, polynomial and power functions were fitted between N_i/N_0 and S_i/S_0 data. The ability of the above functions to estimate the K_s coefficient value was evaluated. The polynomial function has a good function for estimating the K_s coefficient. In the S_0، S_1، S_2 and S_3 treatments, by changing the fertility value from N_0 to N_3, amounts of RAW were 63.7, 58.7, 55.4 and 42% , respectively. Also in N_0، N_1، N_2 and N_3 treatments, with changing the salinity of water from S_0 to S_3, RAW values were 51.7, 46.3, 42.7 and 42%, respectively. Therefore, stresses that reduce crop evapotranspiration are effective on reducing the amount of RAW. In this situation, the actual water requirement of the crop is less than the potential evapotranspiration of the area.
Conclusions: Increasing water salinity and nitrogen deficiency decrease evapotranspiration of maize and increase soil water content. By calculating the stress coefficient (K_s ), it is possible to estimate the actual evapotranspiration of maize, in Qazvin. Thus, the amount of irrigation water is adjusted according to the actual water requirement of maize. Under salt stress conditions with increasing the soil nitrogen, Can be increased the K_s coefficient and evapotranspiration of maize. Therefore, calculating the crop's water requirement based on the existence of strtesse, it will help to saving water.
Research Article
hossein dehghani; Hamidreza Haji Agha Bozorgi; ali asghar ghaemi
Abstract
Introduction: The main problem of salinity, in addition to reducing agricultural and horticulture products is the gradual decline of their cultivation area. Several factors such as climate and irrigation (precipitation, fraction of leaching), soil type and soil salinity, salinity of irrigation water, ...
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Introduction: The main problem of salinity, in addition to reducing agricultural and horticulture products is the gradual decline of their cultivation area. Several factors such as climate and irrigation (precipitation, fraction of leaching), soil type and soil salinity, salinity of irrigation water, uniform distribution of the system and irrigation with saline water affects the soil salinity changes. Therefore, in irrigated agriculture, soil salinity should be reduced and controlled to an optimal level of the economic production. Leaching with proper irrigation management is one of the effective ways to reduce soil salinity.
Materials and Methods: The study was conducted during 2012-2013 in as pistachio garden located in the Safaeieh region of Semnan province. The garden was 100 ha and 2 ha of that was selected for this study with 10 years old pistachio trees equipped to subsurface drip irrigation system. The treatments of this study were three irrigation regimes; control (I1), Irrigation based on irrigation requirement (I2) and I2 plus leaching requirement (I3), three soil depth of 25, 50, and 75 cm from soil surface and time before and after irrigation. The drip line laterals include emitters with 2.26 lph flow rate was buried in 40 cm soil depth. Soil samples to evaluation salt concentration were collected from 25, 50, and 75 soil depth before and after irrigation. To study the impact of different irrigation regimes, soil depth and time (before and after irrigation) and also their bilateral impact a factorial design in randomize block was applied.
Results and Discussion: The results showed that ECe and SAR accumulation decreased after development, growth stage and continued to end growth stage. The results showed that I2 and I3 irrigation regimes were more effective in reducing the amount of sodium from the root zone and the I2 irrigation regime showed better performance in comparison to I3 irrigation regime. Regarding the amount of magnesium in the soil, the I2 irrigation regime was more successful than the I1 and I3 regimens. In I1 irrigation regime, the amount of magnesium at the end growth stage increased compared to the beginning growth stage. Significant decrease in ECe level at the end growth stage compared to the beginning growth stage belonged to the I2 irrigation regime, which suggests that I2 irrigation regime was more successful in ECe leaching during the period of pistachio growth, which attributed to the potential for leaching from the soil surface to the depths below the soil surface. The results showed that excessive water application under saline conditions for any reason, such as leaching not only does not have a beneficial effect on the removal of salts from the root zone, but also may lead to accumulation of salts and damage to the plant. The highest amount of calcium in the soil was recorded 98 days after the first irrigation under the I2 and I3 irrigation regimes which was 52.5 and 58.1 Meq/l, respectively. The lowest amount of this element The I1 and I2 regimens were 40.8 meq/l, respectively, which were recorded in 152 days after the first irrigation. In terms of SAR, the lowest value in the I2 regime was more noticeable than other irrigation regimes. The effects of soil depth of time after the first irrigation showed that there was no significant difference at the depth of 25 cm and 75 cm at the end growth stage compared with the valued recorded in beginning growth stage, but at a depth of 50 cm there was a significant reduction in ECe. The highest ECe value equaled to 14.5 dS/m was recorded at a depth of 75 cm in 98 days after first irrigation. In the I1 irrigation regime at all three depths of 25, 50 and in the I3 irrigation regime at a depth of 75 cm the amount of SAR at the end growth stage were not less than that in beginning growth stage, however, the reduction in SAR was recorded in the I2 irrigation regime at all three depths.
Conclusions: Irrigation regime I2 was successful to control the SAR in different soil depth compared to the other two irrigation regimes, which is very important for the next irrigation season to moderate the harmful effects on blossoms. Moreover, it is suggested that in a field, equipped with a subsurface drip irrigation system, leaching water at the end of the season by surface irrigation or heavy subsurface drip irrigation during the rainfall to leach out the accumulated salt to lower soil layers.
Research Article
Morteza Shahmoradi; Amir Taebi; Hasti Hasheminejad
Abstract
Introduction: The industries of leather, plating, metal processing, wood production, painting, textile, steel making and bottling are the main industries for pollution of heavy metal chromium. Chromium in the two main oxidation states consists of chromium (VI) and chromium (III). Chromium (VI) is more ...
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Introduction: The industries of leather, plating, metal processing, wood production, painting, textile, steel making and bottling are the main industries for pollution of heavy metal chromium. Chromium in the two main oxidation states consists of chromium (VI) and chromium (III). Chromium (VI) is more dangerous, more cancerous and toxic for living organisms compared with chromium (III). In addition, low chromium (VI) concentration can cause health problems, including damage to the liver, as compared with chromium (III). In addition, lower concentrations of chromium (VI) can cause health problems including liver damage and skin cancer. Acceptable limits of chromium (VI) for discharging to surface water and drinkable water are 0.1 and 0.05 mg L-1, respectively. Therefore, wastewater treatment for reaching the desired level of chromium (VI) is essential. There are several methods including chemical oxidation-reduction, ion exchange, electro dialysis, electrochemical treatment, evaporation, solvent extraction, reverse osmosis, chemical treatment and adsorption to reduce chromium (VI) from aqueous and sewage solutions. The main drawback of many of these methods is the high operating cost and remaining sludge disposal problems. Among the techniques, the adsorption method is preferred because of its simplicity, medium-performance and economic conditions. In the adsorption process, the physical and chemical properties of adsorbent are very important for achieving high adsorption efficiency. In the present study, activated particles with sulfuric acid were used to improve the removal of chromium (VI) from aqueous solution. In the adsorption process, the removal of chromium (VI) metal depends on several process variables in a discrete system such as the initial concentration of chromium (VI) solution, adsorbent dose, solution pH, vibrational speed and contact time. Optimizing process variables is necessary to achieve the maximum process efficiency for removing pollutants. A laboratory statistical design approach is necessary to reduce the number of experiments, create an appropriate model for process optimization and also evaluate the effect of response variability. Recently, several types of test design methods have been used to optimize the multivariate chemical process. Response surface of methodology is a set of statistical and mathematical methods for designing experiments in this field. Nevertheless, no study has been carried out on the optimization of the removal of chromium (VI) by particles of the shell modified with sulfuric acid.
Materials and Methods: Chromium (VI) solution was prepared by dissolving potassium dichromate (K2Cr2O7) in distilled water. It should be noted that the dominant form of chromium solution in terms of pH and chromium (VI) contaminant concentrations is (HCrO4) – and (CrO4) 2- in this study.
Preparation of modified tamarind fruit shell: Tamarind fruit shells were prepared from the central part of Iran (Isfahan province). The shells were washed with distilled water and placed in an oven at 110 °C for 4 hours. The dried shells were crushed and then passed through a filter with a size of 200 microns. The resultant particles were contacted with concentrated sulfuric acid (98 % w/w) for chemical activation and H+ ion saturation in a 1: 1 weight ratio and in an oven at 150 ° C for 24 hours. The particles were then washed with distilled water and placed in a 1% sodium bicarbonate solution for 2 days. The material was then washed with distilled water and dried at 100 ° C for 5 hours. With this activation operation, H+ ions are located on the adsorbent surface and increase the adsorption of chromium samples. In this study, chromium samples are more (HCrO4) - and (CrO4) 2- which have an electric charge. These negative samples are definitely adsorbed to the shells by placing H+ ions on the surface of the adsorbent.
Adsorption-Tests: The effect of 5 independent variables on chromium (VI) adsorption of aqueous solution was investigated by the particles of tamarind fruit shells in a discrete medium. All experiments were performed in accordance with the D-optimal matrix method. To adsorb chromium (VI) by tamarind fruit shells, different weights of the tamarind fruit shell (1-7 gr/L) were combined with 50 ml of chromium (VI) solution and different concentrations (50-150 mg/L). The chromium aqueous solution (VI) was prepared by dissolving preset amounts of K2Cr2O7 powder in distilled water. The pH of the solution was adjusted by a solution of 1 M hydrochloric acid or 1 M sodium hydroxide over the range of 1-10. The residual concentration of chromium ions (VI) in the soluble phase was determined by spectrophotometer detection of UV rays at 540 nm by the formation of diphenyl carbazide color. Adsorption Capacity (mg g-1) of the bimetallic system was calculated as follows:
where C0 and Ce are the primary and final concentrations of chromium (VI) (mg L-1), respectively. V and W represent the volume and mass of the solution containing the tamarind fruit shell particles, respectively.
Results: The adsorption of heavy metal chromium (VI) by the modified tamarind fruit shell as a sorbent was studied by changing the pH of the solution, the adsorbent dose, the initial concentration of chromium (VI), contact time and vibrational velocity (shaker). The design of the D-optimal experiment, along with the response surface procedure modeling, was used to maximize the removal of chromium (VI) from the aqueous solution by the particle of the tamarind fruit shell.
Research Article
Farsila Mahmoudian; Ali reza Karimi; Amir Lakzian
Abstract
1- Abdelkhalik Ibrahim M.A. 2011. Argillic horizons and clay-sized particles - an alternative interpretation of their dynamics in sola development and across catenas. Ph.D. Thesis, Iowa State University, 127p.
2- Bayat O., Karimzadeh H.R., Karimi A., Eghbal M.K., and Khademi H. 2013. Pedogeomorphic ...
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Research Article
mohsen barin; Ehsan Ehsan-Malahat; Farrokh Asadzadeh
Abstract
Introduction: Soil is a complex and dynamic biological system, and it still is difficult to determine the composition of microbial communities in soil. Most soil microorganisms are dormant, so their rate of respiration is low. However, their respiration can be stimulated by adding an easily decomposable ...
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Introduction: Soil is a complex and dynamic biological system, and it still is difficult to determine the composition of microbial communities in soil. Most soil microorganisms are dormant, so their rate of respiration is low. However, their respiration can be stimulated by adding an easily decomposable substrate. Also, by adding a simple organic matter, respiration may rapidly increase to a maximum and remains at a constant rate for more than 4 h. Glucose is commonly used as a substrate because most soil microorganisms can readily utilize it as a carbon source. The substrate-induced respiration (SIR) method was modified and adapted to measure fungal, bacterial and total microbial contributions to glucose-induced respiration and the potentially active microbial biomass on decaying plant residues of different composition. Decomposing residues from natural and agricultural ecosystems were chopped and sieved to include the >1 mm fraction for routine SIR analyses on a continuous flow-through respiration system. Substrate induced respiration is a main factor for the assessment of the soil microbial activity. This technique is already used widely in soil microbial studies. Different factors such as the source of carbon, temperature and incubation may play a significant role in the amount of SIR. Therefore, optimizing the test conditions is one of the important criteria for SIR determination. For this purpose, statistical methods such as central composite design (CCD) and response surface method can be used as a useful tool for determining optimal conditions. This study was carried out to model and compare the effect of carbon source (glucose), temperature and incubation time on the SIR of forest and agricultural soils.
Materials and Methods: In this research, 40 experiments were conducted for two soil types including agricultural soil (with relatively low organic matter content) and forest soil (with relatively high organic matter content). Soil samples were collected from the topsoil (0-20 cm) layer. In the laboratory, all visible roots were removed and the soil samples were divided into two parts. One part was kept in plastic bottles at 4°C for SIR analysis. And the rest was air dried in the shade at laboratory temperature for chemical and physical analysis. Electrical conductivity (EC) and pH were determined in saturated soil extract and organic carbon persent (%OC) was determined by di-chromate oxidation. Soil texture was determined using a Bouyoucos hydrometer in a soil suspension. Response surface methodology based on the central composite design was applied in modeling procedure. Different ranges of the independent variables including glucose (0.5-10 mg g-1), incubation time (1-10 hr), and temperature (15-30˚C) were used in central composite design experiments. Totally, 40 experiments based on the coded values of the independent variables were conducted for two soils.
Results and Discussion: Experimental results indicated that the SIR in forest soil is two times greater than the agricultural soil, which may be related to the higher organic matter content and more microbial activity in this soil. Results also revealed the efficiency of the central composite design in predicting the SIR of forest (R2= 0.823) and agricultural (R2=0.919) soils. Among the three independent variables, the linear effect of temperature on the SIR were significant for both soils. However, the substrate (glucose) content has more significant effect in forest soil in comparison with agricultural soil which may be associated with the higher decomposable organic matter content of the forest soil. Glucose enhancement didn’t have significant effect on SIR alteration rate which can be attributed to low organic matter content in agricultural soil. Totally, with increasing time and temperature, the amount of SIR was significantly increased, however with increasing glucose, SIR amount was not significantly increased especially in the agricultural soil. In the forest soil, the process of SIR changes is clearly distinct in response to independent variables compared to agricultural soil. Maximum levels of the SIR in forest soil is clearly associated to the highest time and glucose levels. This indicates that increasing glucose and sufficient time in the forest soil, which contains high amounts of digestible organic matter, can stimulate microorganisms to decompose more organic matter and it outcome is increasing SIR.
Conclusion: This study indicated the high efficiency of response surface methodology in SIR modeling for both forest and agricultural soils. However, the quantitative amounts of SIR were very different in two soils. The amounts of SIR in the forest soil were almost twice relative to agricultural soil. In the forest soil, the amounts of glucose and temperature were as the main variables in increasing SIR, while the temperature and time variables were more determinant in agricultural soil on it.
Research Article
saeid hokmalipour; mehdi panahyankivi; manocher shiri janagard
Abstract
Introduction: The excessive uses of chemical fertilizers have generated several environmental problems. Some of these problems can be tackled by use of Biofertilizer, which are natural, beneficial and ecologically friendly. The Biofertilizers provide nutrients to the plants and maintain soil structure. ...
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Introduction: The excessive uses of chemical fertilizers have generated several environmental problems. Some of these problems can be tackled by use of Biofertilizer, which are natural, beneficial and ecologically friendly. The Biofertilizers provide nutrients to the plants and maintain soil structure. Biofertilizer is an alternative to mineral fertilizers for increasing soil productivity and plant growth in sustainable agriculture. Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that actively colonize plant roots and increase plant growth and yield. There is a widespread distribution of PGPR that flourishes in different geographical habitats. These rhizobacteria significantly affect plant growth not only by increasing nutrient cycling, also by suppressing pathogens by producing antibiotics and siderophores or by bacterial and fungal antagonistic substances and/or by other plant hormones. Inoculation of plants with Azospirillum could result in significant changes in various growth parameters, such as increase in plant biomass, nutrient uptake, tissue N content, plant height, leaf size and root length of cereals. Thus, it has been shown that Azospirillum and Pseudomonas have the potential for agricultural exploitation and can be used as natural fertilizers. The divers array of bacteria including Pseudomonas, Azospirillum, Azotobacter, Bacillus, Klebsilla, Entrobacter and Serratia seem to promote plant growth. These bacteria are important components of the rhizosphere of many plants, and are known to colonize the rhizosphere of wheat, potato, maize, grasses, pea and cucumber. Strains of Pseudomonas putida and Pseudomonas fluorescens could increase root and shoot elongation in wheat. Azospirillum, Pseudomonas and Azotobacter strains could affect seed germination and seedling growth
Materials and Methods: To investigate yield, yield components and some qualitative and quantitative characteristics of safflower at different planting dates, a factorial experiment was conducted based on randomized completed block design with three replications in 2016 at the laboratory of Agricultural University of Payam Noor, Kosar (Kivi) branch. The first factor consists of three sowing dates (5 March, 20 April and 5 May) and the second factor involves the seeds inoculation with plant growth promoting rhizobacteria (no inoculation, seed inoculation with Azotobacter chorchorum strain 5 and Azosprilium lipoferum strain OF). The climate of studied region is semi-arid with 1350 meters altitude from sea level. Based on the soil test, pH was about 7.1, soil texture was loamy-sand and the depth of top soil was 70 cm. The experimental unit included six ridges of 25 cm in 6 m length. The plant density was 40 plants per m2. Each 1 gram bacteria have 107 no, we therefore used about 7 gr from each bacterium for seed inoculation. We also used Arabic gum to adhere the bacteria to the seed.
Results and Discussion: The results showed that the planting date had a significant effect on all characteristics, except brain to grain ratio and the ratio of skin to grain. The effect of seed inoculation with plant growth promoting rhizobacteria was statistically significant on plant height, stem diameter, number of main and sub main branches, seed oil and protein percentage. The maximum number of boll per plant, number of grain per boll, 1000-grain weight, grain yield, biological yield, harvest index, plant height and protein percent were achieved on the first planting date (5 April). The lowest amounts of these traits were obtained on the third planting date (5 May). The maximum oil percentage, number of primary and secondary branches and stem diameter were obtained on the first planting date and seed inoculation by Azotobacter. The lowest rates of these traits were obtained on the third planting date and no inoculation. Thus, seed priming with Azotobacter and first date (5 March) planting are recommendable to increase number of grain per boll, 1000-grain weight, grain yield, biological yield, harvest index, plant height and protein percent and other traits.
Research Article
ali baliani; Ali Reza Vaezi
Abstract
IntroductionRainfall erosion results from the expenditure of the energy of falling raindrops and flowing water when these two agents act either singly or together. Soil erosion by rainfall is a serious ongoing worldwide environmental issue that contributes to soil and water quality degradation. Understanding ...
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IntroductionRainfall erosion results from the expenditure of the energy of falling raindrops and flowing water when these two agents act either singly or together. Soil erosion by rainfall is a serious ongoing worldwide environmental issue that contributes to soil and water quality degradation. Understanding raindrop-impact-induced erosion processes are key to design and apply soil management techniques that minimize and control soil erosion risk. Water erosion and especially raindrop-impact-induced erosion is the primary agents that cause soil erosion-induced degradation and has been identified as one of the major processes contributing to the soil and water quality degradation. Soil degradation caused by rainfall raindrops impacts the soil surface disperses and splashes the soil, and displaces particles from their original position. Raindrops striking the soil surface develop a raindrop-soil particle momentum before releasing their energy in the form of the splash. Other causes of soil degradation are including compaction and penetration resistance.
Materials and Methods: This study was conducted to investigate the raindrop-impact-induced erosion in relation to slope gradient (0, 10, 20, and 30%) and antecedent moisture content or AMC (air dried, quarter saturation, semi saturation, and saturation). Toward this, six soil texture classes were exposed to simulated rainfalls with 40 mm h-1 in intensity for 15-min in four slope gradients and four antecedent moisture contents. Rainfall was simulated using rainfall simulator from soil erosion laboratory of the University of zanjan with 3-meter height and surface of 2 m2. A total of 288 experimental soil boxes with 25 cm × 35 cm dimensions and 5-cm depth were investigated using the completely randomized block design with three replications. Data of soil erosion processes include splash erosion particles amount caused raindrop impact, soil resistance ratio after rainfall using penetrometer, and compaction percent using bulk density after and before rainfall was measured and then compared using Duncan's test among the slope steepness and antecedent moisture content
Results and Discussion: Significant relationships were found between the splash erosion rate, soil resistance ratio and soil compaction means (P<0.01. (The results showed that silt soil carried the highest mean value in splash erosion rate with 1574.93 gm-2 h-1, soil resistance ratio with 10.53 and soil compaction with 17.43 percent, while sand soil carried the lowest mean value in splash rate with 437.37 gm-2 h-1, soil resistance ratio with 2.66 and soil compaction with 0.25 percent. Soil erosion processes were significantly affected by slope gradient and AMC. Soil erosion processes showed a decreasing rate in 0 slope degree and increasing rate in 30 slope degree and also decreasing rate in air dried and increasing rate in semi saturation AMC. Significant correlations (P< 0.01 and 00.05) were found between soil erosion processes and sand, silt, geometric mean particle diameter, bulk density, saturated hydraulic conductivity, and calcium bicarbonate equivalent. among the physical properties of the studied soils, the sand percentage, bulk density, and Geometric mean diameter showed a negative significant correlation with splash erosion, soil compaction, and soil resistance, and the percentage of silt and calcium carbonate content with splash erosion, soil compaction, and soil resistance were positive significant correlated. The cause of this negative and positive correlation might be dependent on particles size and more percent of coarse particles, the transfer of particles from the soil mass is reduced due to raindrops and degradation processes occur with less intensity. In addition, destruction processes with more intensity occurred with increasing silt and lime percent.
Conclusion: Increasing the slope gradient has an incremental effect on the amount of rainfall erosion processes i.e. sediment load, penetration ratio, and soil compaction value. However, antecedent moisture content in various soil textures has the different effect on the amount of rainfall erosion processes. Among the soil chemical properties, only calcium carbonate equivalent with splash erosion, density, and soil surface resistance was positively correlated and chemical properties such as a percentage of organic matter and exchangeable sodium percent no significant correlated with soil erosion processes. In other words, the physical nature of soil-forming particles such as particle size, as well as some of the chemical properties of soil particles such as organic matter, have a more effect on soil degradation, density, and soil resistance ratio. also the role of soil physical properties such as sand percent and calcium carbonate equivalent on the rainfall processes were more than soil chemical properties. In general, increasing the percent of silt and lime in the soil, unlike sand, was increased the sensitivity of the soil to the rainfall erosion and as a result increasing the splash erosion leads to increased soil compaction and soil resistance ratio.
Research Article
tahereh raiesi; bijan moradi; Behruz Golein
Abstract
Introduction: Citrus is the main fruit group grown in tropical as well as sub-tropical climate of more than 150 countries in the world. In Iran, the total area under citrus crops is 0.284 M ha with a production of 4.345 M ton and a productivity of 17 ton per ha. Citrus is also one of the most important ...
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Introduction: Citrus is the main fruit group grown in tropical as well as sub-tropical climate of more than 150 countries in the world. In Iran, the total area under citrus crops is 0.284 M ha with a production of 4.345 M ton and a productivity of 17 ton per ha. Citrus is also one of the most important horticultural products in Mazandaran, with 112,000ha devoted to its cultivation. Drought stress is frequent in Iran and is common in the dry summer periods in Mazandaran. Therefore, irrigation is essential during mentioned periods in this province. Irrigation scheduling and water requirement of the citrus crops are one of the main concerns of the citrus fruit production. Irrigating based on soil water potential (tensiometer) is one of the irrigation scheduling methodologies. In addition, fertilization is used to promote quantity and quality of fruit production. Potassium has a key role in the osmotic adjustment of plants and alleviate the effects of drought stress. Until now, studies on citrus to evaluate the effects of potassium fertilization to mitigate the negative effects of drought stress have not been conducted. In the present study, we hypothesised that K applications via soil could contribute to osmotic adjustment of citrus and alleviate the effects of drought stress. Thus, the objective of the present study was to evaluate the effects of different soil water potential and rate of potassium (K) application on biochemical indices and growth responses of Thomson navel (Citrus, sinensis (L.) osbeck) orange seedlings on Citrumelo rootstock.
Materials and Methods: This study site was located at the Citrus and Subtropical Fruit Research Center of Horticultural Science Research Institute (36°54′11″N, 50°39′30″E), with a mean annual rainfall of 1200 mm. Thomson navel trees (Citrus, sinensis (L.) were planted at 7 × 6m distances. Soil had a pH (soil-to-water suspension ratio of 1:2) of 6.2 and contained 14.3 g kg−1 organic C and CaCO3<1%. The texture of soil was clay loam. A two-year field study was conducted in a factorial experiment based on randomized complete block design with four selected ranges of soil water potential, two levels of K application, and four replicates. Irrigations were scheduled using soil moisture tensiometers. The irrigation treatments were scheduled when soil water tensions reached 20, 40, and 60 kilopascal (kPa) on the tensiometers per treatment and results were compared with control (none irrigation) treatment. Soil water tensions of 20, 40, and 60 kPa correspond to soil water depletions of 17, 35, and 52%, respectively, of the available soil water for the studied soil. Levels of K fertilizer were 50 (k1) and 100 (K2) g K × age of tree. Potassium fertilizer was broadcast below the tree canopy in March. At the end of each year, yield, available K and some growth indices were measured. In addition, in the last year, proline, ionic leakage and electrical conductivity were also measured. All data were represented as mean of four replicates. Differences in yield, canopy diameter and available K among fertilizer and irrigation treatments and sampling years were analyzed using general linear model two-way analysis of variance (ANOVA) in SAS 9.1. Since the mentioned attributes were measured during two years to take into account annual variation, we used ANOVA procedure for a combined analysis of data. The significance of differences between the mean of treatments were determined by using Duncan test. All the statistical analyzes were performed by SAS 9.2.
Results and Discussion: The results showed that irrigation increased the canopy diameter (P<0.05). Under K1 application, the tree yield was not significantly different (P≥0.05) between irrigation at different water potentials (I1, I2 and I3). However, the K effects on tree yield depended on soil water potential and the positive effects of K2 application were evident only in the I2 and I3 treatments. However, K2 application reduced the yield in irrigation treatments including I0 and I1 significantly (P<0.05) compared with K1 application. In addition, the results of the last year showed that proline and ionic leakage were increased (P<0.05) by reduce of water potential in irrigation time. However, double application of K (K2) increased (P<0.05) proline and decreased ionic leakage as compared with normal application of K (K1). Moreover, available K and electrical conductivity were increased (P<0.05) by excessive application of K and reduce of soil water potential.
Conclusion: In summary, regarding this experiment, irrigation at 60 kPa (depletion coefficient =52%) and potassium application rate of 50 g K × age of tree was the best treatment.
Research Article
Maryam Pourmorad; Mohammad Jafar Malakouti; Mohamad Tehrani
Abstract
Introduction: Optimum water consumption in agricultural production is of vital importance as one of the most important environmental factors affecting the growth and development of the plants, especially in arid and semi-arid regions such as Iran. On the other hand, drought stress, among other environmental ...
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Introduction: Optimum water consumption in agricultural production is of vital importance as one of the most important environmental factors affecting the growth and development of the plants, especially in arid and semi-arid regions such as Iran. On the other hand, drought stress, among other environmental stresses, is one of the most important factors that adversely affect the plant growth and yield. Due to the presence of hormonal compounds, organic acids (at low concentrations) can positively affect the production rate and the quality of agricultural products. Considering the water deficit and the necessity of saving water resources as well as the role of organic acids in reducing the negative effects of stress, in the present study attempts are made to investigate the effect of humic and fulvic acid on wheat yield (Triticum aestivum L.) under drought stress conditions.
Materials and Methods: The present study was carried out at the research farm of the national soil and water research institute located 15 km away from Karaj (with elevation of 1280 m) during the 1394-95 crop year. The experiment was a split-plot experiment based on randomized complete block design with three replications which included two main plots (full irrigation and stress) and 36 sub plots of Sivand cultivar. The treatments consisted of the main factor of irrigation regimes at full irrigation and stress levels (35% lower than water requirement) and a sub-factor including six control treatments (F0H0), no foliar application of fulvic acid, in-soil application of 20kg- ha of humic acid (F0H20), Foliar application of fulvic acid (F5H0), and no application of humic acid (F5H0), (F5H20), (F10H0) and treatment (F10H20). The wheat water requirement in the area was estimated by means of Netwat software and irrigation periods were determined based on weather forecast and soil moisture data. Irrigation was carried out using a system of drip irrigation with a specific pressure and discharge level. The stresses were applied from mid-April through consideration of different irrigation hours as compared to full irrigation time. After completion of the growth period, the plant water requirement was accurately estimated by Cropwat software and the percentage of applied stress was accurately calculated (approx. 35%). The Plant yield and some of its components were measured. Statistical analysis was performed through LSD method at 5% significance level using SAS software
Results: The mutual impact between irrigation and fulvic and humic acid applications on total and grain yield was not significant (P <0.05). The highest yield was related to the foliar application of fulvic acid (F10H0) with a total yield of 27331 kg/ha, which had no significant difference with treatment F5H20 (total yield of 25667 kg/ha). Under full irrigation conditions, treatments (F10H0, F5H20) led to 31.81% and 28.44% increase in grain yield (as compared to the treatment yield) respectively. Under low irrigation conditions, treatments (F10H0, F5H20) led to 46.66% and 34.33% increase in grain yield, respectively.
The Weight of 1000 Grains The application of humic acid and fulvic acid alone did not significantly increase the weight of 1000 grains. But the combined application of fulvic acid (F5H0) and humic acid (20 kg /ha) significantly increased the weight of 1000 grains (8.5%). Under low irrigation conditions, the combined application of humic acid and fulvic acid (F10H0) increased the weight of 1000 grains (as compared to the control group) by 14.75%.
Shoot Height The highest shoot height (126.86 cm) was obtained in foliar application of fulvic acid (F5H0) with the in-soil application of humic acid in full irrigation conditions, which increased the shoot height by 22.68% (as compared to the control group). The lowest average shoot height (99.66 cm) was obtained through no application of fulvic acid and humic acid in stress conditions.
Spike Length The application of fulvic acid (F5H0) had no significant effect on spike length. However, the combined application of humic acid (20 kg/ ha-) and fulvic acid (F5H0) increased the mean spike length. Regardless of irrigation conditions, the highest mean spike length was 9.188, 9.105 cm for treatments (F5H20, F10H0) and the lowest mean spike length was 8.258, 8.293 cm, for treatments (F5H0, F0H0).
A number of Grains per Spike The combined application of humic acid and fulvic acid (F5H0) and the application of fulvic acid (F10H0) led to 10% increase in the number of grains per spike as compared to the control group.
Water Use Efficiency The main effect of irrigation and the use of humic acid and fulvic acid on water efficiency was significant at 1% level. The mean comparison at 5% level showed that tension caused 68% increase in water use efficiency. The use of humic acid and fulvic acid increased water use efficiency significantly. The maximum water use efficiency (3.86 kg / m 3) was in spraying the fulvic acid at a concentration of 10 per thousand. Under full irrigation and low water use, the use of fulvic acid at a concentration of 10 per thousand increased water use efficiency as 43.34% and 62.25%
Conclusion: The results of this study showed that the combined application of fulvic acid (F5H0) and humic acid (F5H20) significantly increased all the traits under study. The application of humic acid in drought stress conditions led to 9.09 percent increase in grain yield as compared to the control groups in the full irrigation condition, and the application of humic acid and fulvic acid (F5H0), as well as foliar application of fulvic acid alone (F10H0) under stress conditions led to 23.86% and 24.9% improvement in grain yield respectively ( as compared to control treatments under full irrigation conditions) while foliar application of fulvic acid (F10H0) in drought stress conditions resulted in a 2.65% reduction in grain yield as compared to the same treatment under full irrigation conditions. The results showed that the application of fulvic and humic acid in low irrigation conditions can increase wheat yield and water use efficiency.
Research Article
Zahra Habibi; Mehdi Rahmati; Ali Asghar Alilou; Esmaeil Karimi
Abstract
Introduction: The use of soil amendments more specifically bio-polymers is increasing nowadays. Arabic Gum is also one of the hydrogels that are capable for soil modification. It seems that the main usage of amendments in soils is to improve the structure of intended soils. Saline-sodic soils are among ...
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Introduction: The use of soil amendments more specifically bio-polymers is increasing nowadays. Arabic Gum is also one of the hydrogels that are capable for soil modification. It seems that the main usage of amendments in soils is to improve the structure of intended soils. Saline-sodic soils are among the poorly structured soils. The use of soil amendments in these soils may be of the most concern. The different conditions of saline-sodic soils in terms of microbial activity and sodium concentration imply that there should be differences in effects of different soil amendments in saline-alkaline and non-saline-alkaline soils. There is no report (up to our knowledge) about the application of Arabic gum in saline soils. However, it seems that the effects of Arabic gum in saline-sodic soils may differ from what in non-saline-alkaline soils due to the interactions between Arabic gum, salinity, and sodium. Therefore, the current research was aimed to investigate the effects of Arabic gum as an analogue of exopolysaccharides on several soil characteristics of saline-sodic and non-saline-sodic soils collected from Lake Urmia catchment, northwest of Iran.
Materials and Methods: The current research was carried out using loam soil samples collected from Qareh Chopogh village located on the southeastern border of Lake Urmia, Bonab plain, Northwest of Iran. In order to evaluate the effects of Arabic gum on properties of salin-sodic and non-saline-sodic soils, a factorial experiment based on completely randomized design (CRD) with two factors (salinity - sodicity levels and Arabic gum) and three replications was carried out. Salinity - sodicity levels, as first factor, included EC = 1 dSm-1 and SAR = 1.3 (non-saline-sodic soil), EC = 6 dSm-1 and SAR = 16 (saline - sodic soil), and EC = 30 dSm-1 and SAR = 58 (severely saline-sodic soil). When soils were sampled from each salinity-sodicity classe and transformed to laboratory, pots were prepared and treated with different levels of Arabic gum including 0, 5, and 10 g kg-1 and incubated for one month with varying soil water content between around 0.5FC and FC. After incubation time, disturbed and undisturbed soil samples were collected from pots and were prepared for further analysis. Undisturbed soil samples were used to determine bulk density of pots (Db), volumetric (θv) and gravimetric (θm) saturated soil water contents, and saturated hydraulic conductivity (Ks). Disturbed soil samples were also used to determine wet-aggregate stability (WAS), mean weight diameter (MWD), and mass fractal dimension (Dm) of soil aggregates, soil pH, soil organic carbon (OC), soil cation exchange capacity (CEC), and soil respiration. Finally, results were subjected to analysis of variance in SAS software based on applied design.
Results and Discussion: The interaction of Arabic gum and soil salinity-sodicity was significant for organic carbon, microbial activity and soil structural characteristics (MWD, WAS, and mass fractal dimension). Arabic Gum improved biological soil properties even in saline-sodic soils. The higher microbial activity (16 to 443 mg CO2 kg-1 soil day-1 in higher amount of Arabic gum vs. 3 to 109 mg CO2 kg-1 soil day-1 in blank soil) and organic carbon content (0.31 to 0.36 % in higher amount of Arabic gum vs. 0.14 to 0.22 % in blank soil) were obtained in higher amount of Arabic gum in saline-sodic and non-saline soils. While, the stability (0.88 to 60 vs. 0.9 to 13 %), mean weight diameter (0.06 to 2.53 vs. 0.009 to 0.46 mm), and mass fractal dimensions (0.935 to 2.09 vs. 0.75 to 2.45) of soil aggregates were affected by Arabic gum in non-saline-sodic soils rather than saline-sodic soils. The main effect of soil salinity-sodicity was significant for soil cation exchange capacity, soil pH, gravimetric and volumetric soil water contents, and pots bulk density. The higher amounts of CEC (21 vs. 9 Cmole+.kg-1), pH (8.0 vs. 7.4), volumetric (53 vs. 41 %) and gravimetric (43 vs. 30 %) water contents, and the lower pots bulk density (1.23 vs. 1.37 g.cm-3) were recorded in severely saline-sodic soil compared to non-saline-sodic soil. The main effect of Arabic gum was significant for soil saturated hydraulic conductivity and soil pH where the higher rate of saturated hydraulic conductivity (0.06 cm.min-1 in higher amount of Arabic gum vs. 0.04 cm.min-1 in blank soil) and the lower pH (7.9 in higher amount of Arabic gum vs. 8.2 in blank soil) were recorded in 10 g.kg-1 Arabic gum.
Conclusion: Based on the results, we conclude that although the effectiveness of the Arabic gum is decreased in saline-sodic soils, it significantly affects different soil characteristics. However, it seems that we need to apply higher amount of Arabic gum (higher than 10 g.kg-1) to gain the considerable effects of Arabic gum in saline – sodic soils. Since gradual drying of Urmia Lake, located in northwest of Iran, is leaving behind wide areas of saline and saline-sodic soils which is threatening habitant’s health, modification of these salt-affected areas using Arabic gum can be a useful strategy. Although, improving vegetation density seems to be main key for this aim, application of soil amendments (more specifically Arabic gum) may support the establishment of vegetation in area. Our objective observation also points to this fact that Arabic gum (specifically in higher amount of 10 g.kg-1) resulted in a crust like layer in soil surface specially in dry state that can prevent the removal of salt particles by the wind. However, the effectivity of Arabic gum in preventing the removal of salt particle by the wind (which is a common issue in area) needs to be evaluated through wind tunnel experiments.
Research Article
Hojat Dialami
Abstract
Introduction: Date palm is considered as one of the important fruit trees in Iran. According to agriculture statistic book of Iran (2015-2016), mature date plantation area and production of Iran are 230000 hectares and more than 1000000 tons, respectively. This crop usually is planted in south of Iran ...
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Introduction: Date palm is considered as one of the important fruit trees in Iran. According to agriculture statistic book of Iran (2015-2016), mature date plantation area and production of Iran are 230000 hectares and more than 1000000 tons, respectively. This crop usually is planted in south of Iran where the soils are calcareous with high pH. The high soil pH causes reduction of nutrient elements absorption and yield. Thus, finding a solution for this problem is necessary. The investigations indicate that application of elemental sulfur along with Thiobacillus inoculant in soil reduces local pH in rhizosphere area due to sulfur oxidation. The reduced pH of calcareous soil can increase the availability of other essential nutrients resulting in an increase in the nutrient uptake by plants. In addition, uncontrolled use of chemical fertilizers destroys soil structure and decreases organic matter resulting in a more dense soil. This research was conducted to assess the effects of sulfur along with manure on yield improvement and fruit quality as well as the consumption amount of chemical fertilizers.
Materials and Methods: In order to evaluate the effect of elemental sulfur along with Thiobacilli bacteria and manure on quantitative and qualitative characteristics of date fruit, an experiment was carried out in randomized completed block design (RCBD) with six treatments and four replications on 24 fruitful, 25 years old date palm (cv. Barhee), in Ahwaz (Khuzestan Province). The treatments were: T1= Control (without any fertilizer), T2= (application of chemical fertilizer based on soil test for each date palm), T3= (application of 30 kg manure based on general recommendation for each date palm), T4= T3 + (application of elemental sulfur mixed with Thiobacillus inoculant) as 5% of manure, T5= T3 + (application of elemental sulfur mixed with Thiobacillus inoculant) as 10% of manure and T6= T3 (application of elemental sulfur mixed with Thiobacillus inoculant) as 15% of manure. Before the treatments application, soil and water were sampled and analyzed. In second treatment, macronutrient chemical fertilizers were also applied. Source of nitrogen, phosphorus and potassium were urea, triple super phosphate and potassium sulfate, respectively. The nitrogen fertilizer was split and applied in February and May (the next year). Furthermore, all phosphorus and potassium fertilizers were used in February. These treatments were carried out along with manure (30 kg) and chemical micronutrient fertilizers applied based on general recommendation (i.e. 150 g of zinc sulfate, iron sulfate, copper sulfate and manganese sulfate). In third treatment, manure (30 kg) was applied based on general recommendation for each date palm. In T4, T5 and T5 treatments, 500g of Thiobacillus inoculant was mixed with 25 kg of elemental sulfur and then consumed base on 5, 10 and 15% of manure, respectively. All treatments were undertaken during winter by local placement method (Chalkood). Agro-technical practices such as pollination, thinning and irrigation were done according to local practice. Each year, in May, 20-25 leaflets from middle of leaf in second row were picked up, and their mineral nutrients were analyzed. At harvesting time, yield, average of weight, length, diameter and volume of fresh fruit, weight of stone and weight ratio of fruit pulp to its stone, pH, acidity, brix, total and reducing sugars in fruits were determined. The obtained data were analyzed with MSTATC statistical program and mean comparison was conducted using the Duncan’s Multiple rang test.
Results and Discussion: The results showed that using sulfur along with Thiobacillus bacteria and manure had significant effect on leaf phosphorus concentration at the 1% level and on yield and some quantitative characteristics such as weight, length, diameter, volume and pulp weight of fruit fresh and concentration of nitrogen at the 5% level. Sulfur application did not, however, significantly affect the leaf potassium concentration, stone weight, weight ratio of fruit pulp to its stone, pH, acidity, brix, reducing sugar and total sugar of fruit. As a result, application of 1500 g elemental sulfur (mixed with Thiobacillus inoculant) along with 30 kg manure for each date palm is recommended to improve yield and fruit quality and to reduce chemical fertilizer application.
Research Article
Mojtaba Shokouhi; Seied Hosein Sanaei-Nejad; Mohammad Bannayan Aval
Abstract
Introduction: Achieving sustainable practices of mitigation and adaptation to climate change requires accurate projections of climate change in each region. In this regard, Coupled Model Inter-comparison Project (CMIP) over the past 20 years has shown a good performance. Therefore, new CMIP5 climate ...
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Introduction: Achieving sustainable practices of mitigation and adaptation to climate change requires accurate projections of climate change in each region. In this regard, Coupled Model Inter-comparison Project (CMIP) over the past 20 years has shown a good performance. Therefore, new CMIP5 climate models are expected to be bases for many climate change studies. These models use a new set of emission scenarios called Representative Concentration Pathway (RCP) to project climate change. Climate change is expected to impact wheat production and food security in Iran. So far, no study has not been conducted to regionally project climate change based on new CMIP5 models and RCP scenarios over the major wheat-producing areas in Iran. Our objective was to evaluate the performance of CMIP5 climate models in simulating temperature and precipitation in these areas. In addition, different combinations of climate models were evaluated to select appropriate models in these areas.
Materials and Methods: According to the latest data, nearly 60% of rainfed wheat is produced within our study area. The mean monthly temperature and precipitation data were provided by Meteorological Organization of Iran for synoptic stations. Period of 1975-2005 was considered as a historical period (baseline period). We evaluated outputs from 21 GCMs from CMIP5 climate models for monthly values of total precipitation and mean surface air temperature. One in ten ensembles of each GCM model was evaluated as available. We used model outputs for two emission scenarios i.e. RCP-2.6 and RCP-8.5, for the future periods of 2045–2065 and 2080-2100 to project temperature and precipitation changes. We assigned the models into two groups, high resolution (models less than 2° latitude/longitude, high-re; 11 models) and low resolution (models greater than 2° latitude/longitude, low-re, 10 models). Output GCM models were used for a grid in which recorded data are available. We applied the equidistant quintile-based mapping method (EDCDF) to correct bias of monthly precipitation and temperature simulated by models in the historical period (1975-2005) and, then in the future periods. We also used the root mean square error (RMSE), the coefficient of correlation and the skill scores (SS) to evaluate the model performance.
Result and Discussion: Average of all ensembles of an individual model outperformed the other ensembles in simulating the historical climate. This superiority is largely caused by the cancellation of offsetting errors in individual ensembles of a model, and also reduces the effects of natural internal climate variability in simulations. Taylor diagram showed, contrary to a simulation of temperature, simulations of precipitation have great variability than observations and the standard deviation of simulated precipitation values was less than that of observations for most used models. The models simulated temperature much better than precipitation across the region. Contrary to precipitation, the simulated temperature did not show a significant difference among the models. Several combinations of models resulted in an improvement in precipitation and temperature simulations. Therefore, a combination of models can be used in regional climate change assessment studies. The models performance for simulating the historical climate was evaluated based on skill score (SS) and Δ (the Euclidian distance from perfect skill, point (1, 1, 1, . . . , 1)). Many different combinations of 21 GCM models were evaluated, which combination of 7 models as selected models yielded a lower Δ and higher skill scores. For multimodal ensemble (MME) mean (All, high-re, low-re and Selected, models) Δ value was less than that for individual models. SS values in the simulation of precipitation were more than -3 for 75% of models during the high precipitation months. Uncertainty in the simulation of precipitation during the low precipitation months was more than that of high precipitation months and it was even much more in southern areas (especially in August and September). Uncertainties in temperature and precipitation changes projections were affected by the scenario, the time period and models selected. All models showed biases indicating the fact that direct use of such models in climate change studies (without bias correction) is not recommendable. Although the use of statistical methods for bias correction resulted in a significant reduction of nonsystematic biases, systematic biases were not considerably influenced. Precipitation will increase in northern areas toward the end of the century and a higher reduction in precipitation is anticipated in the southern areas. The average, long-term (2080–2100) temperature increase was 5.5°C under RCP-8.5. Further, temperature increase will be greater in the southern regions.
Conclusion: Performance of 21 GCMs from CMIP5 climate models were evaluated in major rainfed wheat-production areas in Iran and temperature and precipitation changes were projected under RCP-2.6 and RCP-8.5. Taking into account all GCM’s initial conditions (if they are available) leads to a better performance. Simulations of models exhibited biases, so models output must be corrected before they can be used in regional climate change assessment studies. Although bias correction resulted in a significant reduction of nonsystematic biases, systematic biases were not significantly affected. The MME (All, high-re, low-re and Selected, models) consistently outperformed individual models for both precipitation and temperature suggesting that a smaller group of models can be used in regional climate change assessment. We recognized a subset of 21 models (7 selected models) based on performance that combination of them can provide the best performance and plausible future projections.
Research Article
Hossein Mohammadzadeh; Toba Soleymani valikandi
Abstract
Introduction: Tritium is the only radioactive isotope of hydrogen, with a half-life of about 12.3 years, in water molecule which can be used to determine the age of water in a hydrological cycle. Although hydrogen bomb tests entered a lot of tritium into the atmosphere and then into the hydrological ...
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Introduction: Tritium is the only radioactive isotope of hydrogen, with a half-life of about 12.3 years, in water molecule which can be used to determine the age of water in a hydrological cycle. Although hydrogen bomb tests entered a lot of tritium into the atmosphere and then into the hydrological cycle, but at the moment the average amount of tritium concentration in global precipitations is reaching to about 5 TU. The purpose of this paper is to investigate the tritium concentrations in precipitations of the Middle East countries and to determine the tritium concentration in Iran precipitation (especially in precipitations of the west of Kermanshah province) and to determine the relative age of groundwater resources in Paveh, Javanrood, Ravansar and Sarpule Zahab areas using tritium radioisotope.
Materials and Methods: The required tritium data for the Iran and neighbors and for the global precipitations were retrieved from the Global Networks of Isotopes in Precipitation (GNIP) site of the International Atomic Energy Agency (IAEA). To measure the amount of tritium in Kermanshah precipitations, samples were collected from three rain stations, three wells and from nine springs in Paveh, Javanrood, Ravansar and Sarpule zahab areas during fall 2015 and 600 ml in 600 ml water polyethylene containers, all water samples were analysed at Waterloo University Isotope Laboratory.
Results and Discussion: The amount of tritium concentration in precipitations depends on latitude, longitude, temperature, altitude and the vapor mass. The higher amount of vapor and the lower temperature or the higher altitude, decreases the concentration of tritium. In areas such as Karachi, Bahrain and Adena, due to its proximity to the sea and the higher amount of vapor in the atmosphere, the tritium concentration in precipitation is low. In this paper, the tritium concentration in precipitation and groundwater resources of the west of Kermanshah province was measured at the University of Waterloo-Environmental Isotope Laboratory (UW-EIL). Then the average relative age of groundwater was determined. Results indicate that the tritium concentration in precipitation of the west of Kermanshah is about 6.0 TU and it is much lower in groundwater resources. Based on water age division using tritium concentration, the water of precipitations in the west of Kermanshah is modern and the water of groundwater resources are mixture of modern (recently recharge water) and sub modern water (the waters fed before 1950). By determining the amount of electrical conductivity (EC) and the concentration of tritium in the waters of the region, it is concluded that in the direction of flow, with increasing EC and decreasing the amount of tritium, the water age increases. By examining the EC and the relative age of the waters, it can be concluded that in the Sarpule Zahab area, in Ghaleh Shahin plain, groundwater recharge to the alluvial aquifer in Qaleh Shaheen spring area and then it flow in the direction toward Sarabgarm spring. However, in Boshive plain, the groundwater flow from Marab spring towards the Gandab spring. Tritium has a correlation with the air temperature. The higher the temperature, the more the concentration of tritium in the abundant water resources, and the older age for the water sample. In the study area, the average annual air temperature in the Paveh, Javanrood and Ravansar areas are about 15.1, 15.0 and 14.9 degrees Celsius, respectively, and it is about 19.9 degrees Celsius for Sarpule Zahab area. The average concentration of tritium in Pave and Javrroud is about 3.4 TU, however, in Ravansar and Sarpule Zahab areas are about 1.4 TU and 1.1 TU, respectively Therefore, it is evident that the relative age of groundwater is younger in the Paveh region and it is the oldest in Sarpule Zahab region.
Conclusions: The concentration of tritium is associated with the age of water. The lower the amount of tritium is the oldness of the water. The geology and rocks are affected by the movement of water, which is why the age of groundwater resources in the Paveh region due to the development of karst and the rapid transfer of groundwater is less than the Sarpule Zahab and Ravansar areas. On a global scale, the concentration of tritium in the northern hemisphere’s precipitations is much higher than that of in the southern hemisphere, and in the polar regions’ precipitations it is approximately 4 times of the tropical region’s precipitations. By investigating the concentration of tritium in the rain of neighboring countries of Iran it is concluded that the proximity to the sea and the increase of water vapor in the atmosphere have reduced the amount of tritium concentration.
