Research Article
tayebe taherpour; bijan Ghahraman2; kamran davary
Abstract
Introduction: Finding out homogeneous watersheds based on their flood potential mechanisms, is needed for conducting regional flood frequency analysis. Similarity of watersheds based on flood potential severity depends on many factors such as physiographic and meteorological features of the watershed, ...
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Introduction: Finding out homogeneous watersheds based on their flood potential mechanisms, is needed for conducting regional flood frequency analysis. Similarity of watersheds based on flood potential severity depends on many factors such as physiographic and meteorological features of the watershed, geographical location and geological features. These criteria although are sound ones, they suffer from this concept that there is no attention to hydrological losses of runoff into the soil. As a result, current literature lacks for considering geological features into delineating homogeneous regions. The primary contribution of this paper is to include one geological criterion on flood regionalization. In a previous study we made a homogeneous classification for Khorasan Province of Iran without taking into consideration of infiltration features of the region. So, by taking geological features there may provide a sound comparison to regionalization issue.
Materials and Methods: To find out the effect of geological feature on delineation of homogeneous regions, 73 hydrometric stations at North-East of Iran with arid and semi-arid climate covering an average of 29 years of record length were considered. Initially, all data were normalized. Watersheds were clustered in homogeneous regions adopting Fuzzy c-mean algorithm and two different scenarios, considering and not considering a criterion for geological feature. Three validation criteria for fuzzy clustering, Kwon, Xie-Beni, and Fukuyama-Sugeno, were used to learn the optimum cluster numbers. Homogeneity approval was done based on linear moment’s algorithm for both methods. We adopted 4 common distributions of three parameter log-Normal, generalized Pareto, generalized extreme value, and generalized logistic. Index flood was correlated to physiographic and geographic data for all regions separately. To model index flood, we considered different parameters of geographical and physiological features of all watersheds. These features should be easily-determined, as far as practical issues are concerned. Cumulative distribution functions for all regions were chosen through goodness of fit tests of Z and Kolmogorov-Smirnov.
Results and Discussion: Watersheds were clustered to 6 homogenous regions adopting Fuzzy c-mean algorithm, in which fuzziness parameter was 1.9, under the two different scenarios, considering and not considering a criterion for geological feature. Homogeneity was approved based on linear moment’s algorithm for both methods, although one discordant station with the lowest data was found. For the case with inclusion of genealogic feature, 3-parameter lognormal distribution was selected for all regions, which is a highly practical result. On the other hand, for not considering this feature there were no unique distribution for all regions, which fails for practical usages. As far as index flood estimation is concerned, a logarithmic model with 4 variables of average watershed slope, average altitude, watershed area, and the longest river of the watershed was found the best predicting equation to model average flood discharge. Determination coefficient for one of the regions was low. For this region, however, we merged this region to other regions so that reasonable determination coefficient was found; the resulting equation was used only for that specific region, however. By comparing the distributions of stations and also two evaluation statistics of median relative error and predicted discharge to estimated discharge ration corresponding to 5 different return periods (5, 10, 20, 50, and 100 years). Both perspectives showed acceptable results, and including geological feature was effective for flood frequency studies. With considering the geological feature for regionalization, Besides, Log normal 3 parameters distribution was found appropriate for all of the regions. From this point of view, geological feature was useful. Median of relative error was lower for small return periods and gradually increased as return period was increased. Median of relative error was between 0.21 to 00.45 percentages for the first method, while for the second method it varied between 0.21 to 0.49 percentages. These errors are quite smaller than those reported in literature under the same climatic region of arid and semi-arid. The probable reason may due to the fact that we made a satisfactory regionalization via fuzzy logic algorithm., We considered another mathematical criterion of “predicted discharge to the observed discharge”. The optimum range for this criterion is between 0.5 and 2. While under-estimation and over-estimation are found if this criterion is lower than 0.5 and higher than 2, respectively. Based on this premise, 75 to 95 percentages of stations were categorized as good estimation under the first method of analysis. On the other hand, 78 to 97 percentages of stations were considered good for the second approach.
Research Article
Saeed Salehi; Kazem Esmaili
Abstract
Introduction: Today, always some occurrences threat the earth. One of the most important of this event is seepage from earth dam. It can wash interior body of earth dam that finally might ruins whole the earth dam. For investigating these events in this research some experiments for expressing some alternatives ...
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Introduction: Today, always some occurrences threat the earth. One of the most important of this event is seepage from earth dam. It can wash interior body of earth dam that finally might ruins whole the earth dam. For investigating these events in this research some experiments for expressing some alternatives to solve this problem in earth dam with clay core were investigated. In first step has been introduced new design in earth dam that it includes earth dam with clay core.
Materials and Methods: In order to determine the height of the filter after the vertical clay core in non-homogeneous earth dam,3 experimental model with length 2/4 meter and a height of one meter and Body slope 1H: 2V was prepared. This model made in Shahrekord University. In flume that has 0.6 meter with, 6-meter length and 1-meter height. This flume has a drain in downstream which determine the discharge through earth dam. Front of flume made glass for visual inspection and behind flume made by steal sheet that was welded. Also, for embankment model, two types of fine-grained and coarse-grained soils were used that determine the range of hydraulic conductivity of soils was performed with Using aggregation experiments model and Soil Mechanics hydrometer. For embankment model use layer have 0.1meter height and this layer was impacted after an after. Finally, dam was built. The slope of models was elected in reference that had normal range and had economical cases. In the first downstream the dam crest was used fine-grained soil and upstream of the dam crest was used coarse-grained soil finally experiment done. In models 2 and 3 with cutting fine grained soil from the toe of the dam to the dam crest vertical clay core was created. The parameter a /L was introduced. A is thickness of clay core and L is the Length base of the dam although in the second model and the third model was selected. Level of water in pound was performed in 3 water height 80 and 55 and 30 and in 3 level of water determinate pressure with 30 embedded piezometers and this data was used in method model .as well as phreatic line was determinate by using of wells and 30 embedded piezometers in the model. Seven holes were instated in body of earth dam in 3 models for visual inspection of phreatic line. In 3 model of earth dam decline clay core in laboratory for show this effect in discharge and phreatic line use Method model. Then the rates of decline in clay core in the laboratory with modeling in software PLAXIS V8.5 were compared. The rate of high filter after the clay core with safety factor 1.2 (Encounter Line Leak with 20% of the bottom filter) was introduced. Finally use SAS software to compare the result of data in filth and software after that comparing show can use software for continue the experiment with Method Model. With change the permeability in PLXIS V8.5 modeling another state. Permeability, this modeling showed that tackiness and permeability of vertical core soil effect in height of vertical filter in downstream. So, can decline this case with choose non-permeability in core. That show in result of this paper. With the class of soil and permeability and change the tackiness of core can estimate height of filter in downstream.
Results and Discussion: Finally, Analysis and comparison between water Failure in interface of fine-grained and coarse-grained soils, both of Software model and laboratory model have a relatively well fit. To obtain the height of Suggested filter, the software model was used to simulate the experiments and Subtracting the thickness of the fine-grained. By applying safety factor of 1.2, Height was designed to filter and after that the clay core was introduced. Software model results show that by increasing clay core thickness the angle of broken-seepage line is increased. Also, the experimental model can emphasize this matter. Finally, by using vertical clay core against the clay core with slop can improve the application of earth dam and by using his plan can improve and diminish the seepage from the earth dam body that this design process was expressed in this research.
Research Article
Hossein Dehghanisanij; Elahe Kanani; samira akhavan
Abstract
Introduction: Partitioning of evapotranspiration (ET) into evaporation from the soil (E) and transpiration through the stomata of plants (T) is important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally, T is the desired component with the water ...
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Introduction: Partitioning of evapotranspiration (ET) into evaporation from the soil (E) and transpiration through the stomata of plants (T) is important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally, T is the desired component with the water being used to enhance plant productivity; whereas, E is considered a source of water loss or inefficiency, and is the basis of the management and organization of water resources. The present investigation was carried out with the objectives evaluation of corn evapotranspiration and its components and relationship between leaf area index and components in surface and subsurface drip irrigation systems.
Materials and Methods: The pilot farm were located in the water and soil department of the ministry of agriculture in Karaj, Iran (latitude of 51°38 ˊN and longitude of 35°21ˊ W, 1312.5 m above sea level). For implementation project was placed 8 volume micro-lysimeters in the soil, which were filled with soil excavated from the study site. The soil inside of micro-lysimeter and the soil of the surrounding study had the same physical-chemical characteristics. The corn was irrigated with surface drip (DI) and subsurface drip irrigation (SDI) system, that was installed just prior to planting in 2014 in a field that was planted to sprinkler-irrigated corn. Daily crop actual evapotranspiration (ETc) of each micro-lysimeter was calculated by applying the water balance method and soil evaporation was measured with micro-lysimeters. Finally, plant transpiration was calculated from difference between the actual evapotranspiration value and amount of evaporation from the soil surface. Leaf area index (LAI), was measured, and it was measured with the electronic leaf area-meter, CI – 202 seven times during the growing season. This method provides an indication of the plant growth.
Results and Discussion: The obtained results indicated that actual corn evapotranspiration was 377 and 371.92 mm for surface drip and subsurface drip irrigation systems, respectively. The value of corn evapotranspiration under surface drip and subsurface drip irrigation increased from initial, to middle season stages. The maximum daily values of ETc occurred on 48 days after planting in middle season stages. The total value of transpiration plant was 5.88, 76.82 and 118.21 mmd-1 for surface drip irrigation system and 12.78, 81.31 and 118.95 mmd-1 for subsurface drip irrigation system in the initial, advance, and middle season stages, respectively. Sum evaporation from the soil surface and crop transpiration was 200.81 and 176.02 mm for surface drip irrigation system and 213.04 and 158.81 mm for subsurface drip irrigation system. So, amount of evaporation from the soil surface was 73.02, 65.73 and 37.32 mm for surface drip irrigation system and 65, 58.83 and 34.98 mm for subsurface drip irrigation system in the initial, advance, and middle season stages, respectively. In surface drip and subsurface drip irrigation was allocated approximately 93 and 83 percent of evapotranspiration to evaporation from the soil surface respectively. The minimum daily values of E/ETc were 37 and 34 mm for surface drip and subsurface drip irrigation systems respectively, and occurred in middle season stages. Amount of transpiration was 5.88, 76.82 and 118.21 mm for surface drip irrigation system 12.78, 81.31 and 118.95 mm for subsurface drip irrigation for the initial, advance and middle season stages, respectively. The relationship between T/ETc and LAI was fitted to a polynomial equation with significant correlation coefficients, R2 = 0.95 and 0.89 for surface drip and subsurface drip irrigation systems, respectively. T/ETc started from 0 at sowing, and reached to its maximum at the middle growth stage or when LAI reached to about 3.0. Also, the relationship between E/ETc and LAI was fitted to a polynomial equation with significant correlation coefficients, R2 = 0.97 and 0.88 for surface drip and subsurface drip irrigation systems respectively, and reached to its minimum at the middle growth stage. Also the results showed that subsurface drip irrigation systems have higher biological yield and higher values for plant parameters in compared to surface drip irrigation system that it shows subsurface drip irrigation system due to evaporation reduction, better weed control and direct transport of water to the developmental zone has a significant role in increasing corn yield.
Conclusion: The results of this study indicated that soil evaporation losses in subsurface drip irrigation system had lower than surface drip irrigation system. Also, had higher transpiration in the growth season. This could perform important role on yield of crop. These results should help the precise planning and efficient management of irrigation for these crops in this region.
Research Article
Darush Yarahmadi; Hamid Mirhashemi
Abstract
Introduction: Forecasting and modeling of river flow is an essential step towards planning, designing and utilizing water resources management system which is subject to issues such as droughts and destructive floods in river basins. The river flow deficit and excess could result in financial and human ...
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Introduction: Forecasting and modeling of river flow is an essential step towards planning, designing and utilizing water resources management system which is subject to issues such as droughts and destructive floods in river basins. The river flow deficit and excess could result in financial and human losses. Such predictions of river flow not only provide the necessary warning signals about the flood risk, but also help to adjust the water outflows during low level of water flows which help to the water resource management. Due to the importance of river flows and its fluctuations in short and long term on different aspects of human lives, understanding its behavior and performance is crucial (necessary). Thus, with discovering its dynamic behavior, it is possible to predict its future performance. The aim of this study is to explore and simulation of Kashkan River’s performance using the statistical intelligent methods to provide models with lower uncertainty in order to improve the planes based on Kashkan’s River flows.
Materials and Methods: For this study, the series of daily discharge data from Poldokhtar- Kashkan station (located in the coastal river) over 1370-1393 were used as the primary input. Methods used in this study were based on memory uses the Hurst exponent of long memory time series. Runoff is the dynamics of the series. The current state of these series is dependent on its historical states. The delay time (lag time) of 1, 3, 5, 7, 10 and 15 days before the runoff were calculated. The amount of runoff was seen as a function of the time series. Considering the above-mentioned six time series as input signals, time series modeling using statistical methods K- nearest neighbor (K-NN), and artificial neural network, combined wavelet - K-NN and combining the wavelet nervous.
Results and Discussion: Kashkan’s Memory river flow system, using the Hurst exponent within 10 days and mid-4200 based on the amount of 0.6 was obtained (Figure 2). This amount indicates a non-linearly behavior and a dynamic learning system. In addition, it shows the presence of long memory in the river flow time series. Then, by allocating 80% of the data for training and the remaining 20 percent for testing the model and adopting ranges from 1 to 10 nearest neighbor and a range of 1,000 to 50,000 particles (for data on education) Model K-NN were prepared. Using the criteria to assess the efficiency and accuracy of a model in each performance of the mentioned domains, the best model with the 6 neighbors structure and 15,000, was obtained. In this model stimulated the runoff with the correlation of 0.90 and a 4.6 error was obtaied. On the other hand, artificial neural network architecture to simulate runoff with 6 input neurons in a hidden layer neurons and considering 3 to 20 and an output neurons leading to the 6-8-1 structure as the best model was fitted. This model has a correlation of 0.89 and the forecast error of 5.8 in the process of runoff simulation. Then using wavelet function, mortality, time-series signal runoff into 4 levels, including 8 under high frequency and low frequency signal was decomposed where high-frequency signals and low-frequency signal of 4 level were considered as the original signal for the input surface runoff. In this regard, the hybrid model K-NN-WT with runoff time series prediction error of 2.7 percent and the hybrid model ANN-WT with the correlation of 0.99 the estimation error of 1.2 were simulated.
Conclusion: Running 4 Artificial Neural Network (ANN), K-nearest neighbor (K-NN) and combining the wavelet analysis of the two models (ANN-WT and K-NN-WT) to predict the time series of runoff river showed that due to the existence of multiple time frequencies in the time series of the river signals, its decomposition it using wavelet analysis results in extraction of hidden information that are not available through the original signal. This information is the daily, monthly, quarterly and annual fluctuations. The hybrid models performance indicated higher accuracy and improved outcomes relative to individual models. In fact, the analysis of the original runoff signal by wavelet analysis in the process of simulation results in an appropriate weighting given to long-term and short term dynamic of runoff which led to significant lower error in modeling
Research Article
Mohammad Reza Goodarzi; Alireza Faraji; Mahdi Komasi
Abstract
Introduction: Uncertainty estimation of climate change impacts has been given a lot of attention in the recent literature, However, uncertainty in downscaling methods have been given less attention. Today many studies have been done about the future impact of climate change on human life and water resources. ...
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Introduction: Uncertainty estimation of climate change impacts has been given a lot of attention in the recent literature, However, uncertainty in downscaling methods have been given less attention. Today many studies have been done about the future impact of climate change on human life and water resources. Urban development, water conflicts, and Green House Gases increasing will intensify this event in future and will alter rivers flow. Basin catchment has faced to flow recession and also runoff decreasing in few last decades. At this field the climate change effects will intensify this conditions in future decades too. The first step of climate change impacts studies is the projection of future climate variables (e.g precipitation and temperature). GCMS models and their outputs are useful tools for this projection. The main problem is the mismatch of spatial scale between the scale of global climate models and the resolution needed for impacts assessments.
Materials and Methods: The Gharesou River Basin is located in the west of Iran. Its area is approximately equal to 5793km2, and the maximum and minimum of its heights are 1237 and 3350 m, respectively. The average of annual rainfall varies from 300 to 800mm. This study focuses on various climate models from IPCC fourth and fifth reports and has been used two downscaling methods including the statistical and proportional downscaling methods and also scenarios and different climate models for considering different uncertainty. The new scenarios as Representative Concentration Pathways (RCPs) of greenhouse gasses have been used in fifth assessment reports (AR5) of IPCC. The Representative Concentration Pathways describe four different 21st-century pathways of greenhouse gas (GHG) emissions and atmospheric concentrations, air pollutant emissions and land use. The RCPs represent the range of GHG emissions. Different kinds of downscaling method include 1) Proportional downscaling that is adding coarse-scale climate changes to higher resolution observations (the delta approach); 2) Statistical method (eg SDSM model; CLIGEN; GEM; LARS-WG and etc); 3) Dynamical method that is application of regional climate model using global climate model boundary conditions (e.g, RegCM3; MM5 and PRECIS). statistical downscaling method processes establish relating large scale climate features (e.g., 500 MB heights), predictors, to local climate (e.g, daily, monthly temperature at a point), predictands. The SDSM software reduces the task of statistically downscaling daily weather series into seven discrete processes that are consist of quality control and data transformation; screening of predictor variables; model calibration; weather generation (observed predictors); statistical analyses; graphing model output and scenario generation (climate model predictors). HEC-HMS (Hydrologic Modeling System) has been designed by HEC (Hydrologic Engineering Center) for simulation of precipitation-runoff processes in a drainage basin. The HEC-HMS simulation methods represent - Watershed precipitation and evaporation: These describe the spatial and temporal distribution of rainfall on and evaporation from a watershed. - Runoff volume: These address questions about the volume of precipitation that falls on the watershed: How much infiltrates on pervious surfaces? How much runoff of the impervious surfaces? When does it run off? - Direct runoff: including overland flow and interflow. These methods describe what happens as water that has not infiltrated or been stored on the watershed moves over or just beneath the watershed surface. Baseflow: simulate the slow subsurface drainage of water from a hydrologic system into the watershed’s channels.- Channel flow: These so-called routing methods simulate one-dimensional open channel flow, thus predicting time series of downstream flow, stage, or velocity, given upstream hydrographs. HEC-HMS includes several models for calculation of cumulative precipitation losses but only the SMA module is continuous (a module that simulates the losses for both wet and dry weather conditions). Other loss models are event based.
Results and Discussion: The results of criteria and models weighting show that CANESM2 and HADCM3 are better than other models for future temperature and precipitation projection for statistical downscaling and HADCM3 for future precipitation and HADGEM for future temperature assessment for Proportional downscaling. According to various scenarios, future temperature and precipitation projection (2040-2069 period for the statistical and 2040-2052 period for Proportional downscaling) have downscaled and have given to HEC-HMS model for future flow projection. Already the rainfall-runoff model has calibrated and validated base on observed flow data in reference period that daily coefficient of determine was 0.7 for calibrated period and 0.6 for validated period. Finally, flow variation has investigated that Most of GCMS represent increases in winter flows and reductions in other season flows.
Research Article
Hamid Kardan Moghaddam; Mohammad ebrahim banihabib; Saman Javadi
Abstract
Introduction: Groundwater is predominantly a renewable resource, and when managed properly can ensure a long-term water supply for increasing water demand and for climate change impacted region. Surface water renews as part of the hydrologic cycle in an average time period ranging from approximately ...
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Introduction: Groundwater is predominantly a renewable resource, and when managed properly can ensure a long-term water supply for increasing water demand and for climate change impacted region. Surface water renews as part of the hydrologic cycle in an average time period ranging from approximately 16 days (rivers) to 17 years (lakes and reservoirs); however, the average renewal time for groundwater is approximately 1400 years for aquifers to millions years for some deep fossil groundwater. Groundwater depletion, which is the reduction in the volume of groundwater storage, can lead to land subsidence, negative impacts on water supply, reduction in surface water flow and spring discharges, and loss of wetlands. Water balancing strategy has been considered as one of the most effective options to mitigate the groundwater depletion, and thus the balancing scenarios are applied as main approach to manage ground water sustainably. The purpose of the water balancing strategy in aquifers management is that groundwater level to be returned to the primary water level and to compensate the water resources shortage of aquifers’ storage.
Materials and Methods:
1. Case study: Birjand aquifer with an area of 1100 square kilometers is situated in eastern part of Iran. The location of the aquifer is between 59o 45 and 58o 43 east longitude, and 33o 08 and 32o 34 north latitude.
2. Modeling: Laplace Equation is the basic equation for groundwater flow study in steady or unsteady states. In simulation by using numerical models, the boundary of the model, recharge and discharge resources, evaporation and recharge zones are important elements. After finding the key components of the conceptual model, the MODFLOW software was applied for simulation of groundwater. MODFLOW, which is a computer code that solves the groundwater flow equation and uses finite-difference method, is provided by the U.S. Geological Survey.
3. Sustainability Analysis: In order to achieve the objective of this study, water balancing scenarios should be evaluated for sustainability of the groundwater system using appropriate indices. Here, three indicators of reliability, vulnerability and desirability are proposed and were employed to assess the stability of groundwater system in different balancing scenarios in lumped and distributed forms. The aquifer sustainability index is expressed in Equation 4. In this equation, three indicators of aquifer reliability (Equation 1), aquifer vulnerability (Equation 2) and Desirability (Equation 3) have been used to assess the stability of groundwater system. The aquifer reliability index means in what extent the withdrawal scenario has been able to return the aquifer to its original state using the Equation 1 as follows:
(1)
In which the number of periods where the groundwater level is above the desired level (equilibrium balance) and the total number of time steps in simulation. The vulnerability index indicates the amount of shortage in the groundwater storage and expresses the severity of the system failures using the Equation 2 as follows:
(2)
In this equation, the desired groundwater level at time step t, the groundwater level simulated in t time period for each scenario, the groundwater level without scenarios and n the number of periods where the groundwater level is lower than the desired level. The index of the likelihood of returning the system to a favorable state is presented as an indicator of the desirability of the system using the Equation 3 as follows:.
(3)
In this equation, indicates the f ground water level after the depletion, is the desired level of groundwater and is the groundwater level (without the scenario). After estimating three indicators of reliability, vulnerability and desirability, the sustainability index for each scenario can be appraised using Equation 4.
(4)
In this equation, groundwater sustainability index, reliability index, desirability index and vulnerability index.
Results and Discussion: In this study, six water balancing strategies were employed to reduce 1, 1.5, 2, 2.5, 3 and 3.5 percent water withdrawing for agricultural water use. Results of the simulation of different water balancing strategies demonstrated that with reducing in water use, the stability index has been improved significantly. The improvement changes from 32% increase in the index for 1% water withdrawing reduction scenario to 88% increase in the index for the 3.5% water withdrawing reduction scenario. Moreover, the reviewing of the stability indices of the system in various scenarios reveals that a 2.5% reduction in water use will assistance the aquifer status achieve to a stable state.
Conclusion: In order to manage groundwater withdrawal, it is easier to assess the impact of the water balancing scenarios using the groundwater sustainability index. The review of sustainability indices in the studied aquifer shows that by reducing 1% of the water harvest, 32% of the system's stability increases, and if water harvest reduction reaches 3.5%, the index increases 88%. Considering the distributed potential and possibility of the investigation of different scenarios by proposed indices in this study, they can be applied to assess and manage other similar aquifers.
Research Article
Sheyda Kaboodi; farzin shahbazi; Nasser Aliasgharzad; nosratola najafi; naser davatgar
Abstract
Introduction: Understanding soil biology and ecology is increasingly important for renewing and sustainability of ecosystems. In all ecosystems, soil microbes play an important role in organic matter turnover, nutrient cycling and availability of nutrients for plants. Different scenarios of land use ...
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Introduction: Understanding soil biology and ecology is increasingly important for renewing and sustainability of ecosystems. In all ecosystems, soil microbes play an important role in organic matter turnover, nutrient cycling and availability of nutrients for plants. Different scenarios of land use may affect soil biological properties. Advanced information technologies in modern software tools such as spatial geostatistics and geographical information system (GIS) enable the integration of large and complex databases, models, tools and techniques, and are proposed to improve the process of soil quality and sustainability. Spatial distribution of chemical and biological properties under three scenarios of land use was assessed.
Materials and Methods: This study was carried out in Mirabad area located in the western part of Souldoz plain surrounded by Urmieh, Miandoab, Piranshahr and Naghadeh cities in the west Azerbaijan province with latitude and longitude of 36°59′N and 45°18′E, respectively. The altitude varies from 1310 to 1345 with average of 1325 m above sea level. The monthly average temperature ranges from -1.4 °C in January to 24.6 °C in July and monthly precipitation ranges from 0.9 mm in July to 106.6 mm in March. Apple orchard, crop production field and rich pasture are three selected scenarios in this research work. Soil samples were systematically collected at 65 sampling points (0-30 cm) on mid July 2010. Soil chemical and biological properties i.e. microbial community, organic carbon and calcium carbonate equivalent were determined. The ArcGIS Geostatistical Analyst tool was applied for assessing and mapping the spatial variability of measured properties. The experimental design was randomized complete blocks design (RCBD) with five replications. Two widely applied methods i.e. Kriging and Inverse Distance Weighed (IDW) were employed for interpolation. According to the ratio of nugget variance to sill of the best variogram model three following spatial dependence conditions for the soil properties can be considered: (I) if this ratio is less than 25%, then the variable has strong spatial dependence; (II) if the ratio is between 25% and 75%, the variable has moderate spatial dependence; and (III) otherwise, the variable has weak spatial dependence. Data were also integrated with GIS for creating digital soil biological maps after testing analysis and interpolating the mentioned properties.
Results and Discussion: Spherical model was the best isotropic model fitted to variograms of all examined properties. The value of statistics (R2 and reduced sum of squares (RSS)) revealed that IDW method estimated calcium carbonate equivalent more reliably while organic carbon and microbial community was estimated more accurately by Kriging method. The minimum effective range (6110 m) was found for microbial community which had the strong spatial dependence [(Co/Co+C)
Research Article
faeze lotfi; amir fotovat; reza khorasani; Mahdi Bahraini
Abstract
Introduction: The pollution of soils by heavy metals due to human activities poses a serious concern for human and environmental health. In order to evaluate the risks of heavy metal contamination such as cadmium in soil, it is necessary to understand its bioavailability which depends on its chemical ...
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Introduction: The pollution of soils by heavy metals due to human activities poses a serious concern for human and environmental health. In order to evaluate the risks of heavy metal contamination such as cadmium in soil, it is necessary to understand its bioavailability which depends on its chemical forms in the soil. According to Tessier (1979), heavy metals can be found in various chemical forms in soil including exchangeable, bound to carbonates, bound to iron and manganese oxides and bound to organic matter and residual. These fractions significantly influence the cadmium mobility and bioavailability. Distribution of metals in chemical forms in soil depends on soil pH, amount of organic matter, oxidation-reduction potential and ionic strength. Root exudation, soil texture, cation exchangeable capacity and amount of calcium carbonate may also impact chemical forms of cadmium. Many studies have showed that plant root may affect the chemistry of heavy metals in soil root zone. The objective of this study was to evaluate the effect of organic matter on the distribution of cadmium in corn root media.
Materials and Methods: To investigate the effect of organic matter (cow manure) and root activity on chemical forms of cadmium, a greenhouse experiment was conducted using rhizobox. The contaminated soil sample used in the study was collected from Zanjan. This greenhouse experiment was conducted in a factorial design, with 2 replications, two levels of organic matter (0 and 1.5%) and three zones classified based on their distance from root. The soil samples were air dried and crushed to pass through a 2-mm sieve. The cultivation was conducted using a rhizobox. The rhizobox consisted of three parts: 1.central compartment (rhizosphere), 2.close to rhizosphere, and 3. soil bulk. Soil samples were mixed with fertilizer and packed in rhizobox. Eight pre-germinated maize seedlings were transferred to the central compartment and five days after germination, thinned to four plants. Ten weeks after planting, corn plants were harvested for analysis. The compartments of rhizobox were separated. The collected plant samples (root and shoot) were rinsed with deionized water and oven-dried at 70 °C. Soil samples were also measured for pH, CEC and total organic carbon. The chemical forms of cadmium in the soil and plant samples were identified by the sequential extraction procedure proposed by Tessier (1979). Bioavailable cadmium in soil was also extracted by DTPA-TEA.
Results and Discussion: Results showed that the highest amount of soil cadmium was found in carbonate fraction. Adding organic matter increased the soil pH, CEC and organic carbon amount, whereas none of chemical forms of cadmium were significantly affected by adding organic matter. Bioavailability of cadmium, however, decreased by adding organic matter to soil, It can be therefore concluded that increment in cadmium uptake due to increased organic matter led to decreased cadmium bioavailability. The exchangeable cadmium was negatively correlated to soil organic carbon, while bioavailable cadmium was negatively correlated to soil pH, CEC and amount of soil organic carbon. Moreover, our results indicated that the fractions of cadmium were not significantly affected by distance from the root. Moreover, adding organic matter insignificantly increased concentration of cadmium in shoots, roots and total plants.
Conclusion: In this study, among different chemical forms of cadmium, only bioavailable cadmium was significantly affected by adding organic matter to soil. Additionally, soil pH, CEC and organic carbon were significantly increased by adding organic matter. These results indicate that addition of organic matter to soil may indirectly influence chemical forms of cadmium through impacting soil properties (soil pH, CEC and organic carbon). The addition of organic matter had the most influence on carbonate fraction of cadmium which may be potentially available to plant. It seems that addition of organic matter (cow manure) may result in increase of cadmium concentration in plant. Therefore, it can be concluded that addition of cow manure to calcareous soils with neutral to slightly alkaline pH may lead to increased cadmium uptake by the plant (corn) and reduced soil cadmium concentration.
Research Article
elham sadeghi; fayez raiesi; Alireza Hosseinpour
Abstract
Introduction: Soil, as an important component of terrestrial ecosystems, plant growth media, and a habitat of diverse living organisms commonly encounters a variety of abiotic stresses. Soil microorganisms play an important role in maintaining soil quality and functioning, since they are responsible ...
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Introduction: Soil, as an important component of terrestrial ecosystems, plant growth media, and a habitat of diverse living organisms commonly encounters a variety of abiotic stresses. Soil microorganisms play an important role in maintaining soil quality and functioning, since they are responsible for the decomposition of dead organic material, nutrient cycling and degradation of hazardous organic pollutants. Metal toxicity and salinity are the major abiotic stresses affecting soil microbial activity and community structure in many areas of the world, in particular arid regions. Anthropogenic activities have increased the concentration of heavy metals and soluble salts in soil, resulting in a major constrain for soil microbial performance and functions. Furthermore, soil microbial activity and biochemical processes are often limited by substrate availability in arid areas due to the low organic inputs. Although the individual effects of salinity and metal toxicity stresses on soil biological activity are generally well-known, their combined effects on microbial growth, population and functions are largely uncertain. The main aim of this study was to investigate the interactive effects of salinity and cadmium (Cd) Pollution on microbial respiration and biomass in a calcareous soil treated with plant residue. It was hypothesized that salinity would increase mobility and availability of Cd with subsequent reductions in microbial activity and biomass, and that addition of plant residue would modify these salinity effects.
Materials and Methods: This study was conducted under controlled laboratory conditions at Shahrekord University. A factorial experiment with two levels of cadmium (0 and 30 mg kg-1), three levels of salinity (1.35, 7.5 and 10 dS m-1) and two levels of plant residue (with and without alfalfa residue) was conducted using a completely randomized design with four replications. Using cadmium chloride salt, the soil was contaminated, and subsequently amended with alfalfa residue (1%, w/w). After thorough mixing of soil and plant residue, salinity treatments were applied using NaCl salt. To reactivate the microbial population and for the aging effect, soil moisture was set at 70% of field capacity, and containers were pre-incubated at room temperature for 4 weeks. The samples were then incubated at 25±1 oC for 98 days. Soil carbon (C) mineralization (microbial respiration) was measured weekly, and available Cd and microbial biomass C were measured at monthly intervals. In this experiment, the Bliss independence model was used to determine the type and nature of the interaction between salinity and pollution (synergistic and antagonistic).
Results and Discussion: The results showed that NaCl salinity increased the concentration of soil available Cd in both polluted and unpolluted soils over the experimental period, and the increases were greater at high than low salinity levels. This effect of salinity was less pronounced in residue-amended and unamended soils. In general, a strong synergistic effect of both stresses upon Cd availability was observed in residue-unamended soils while this effect was mostly antagonistic in residue-amended soils. This indicates that addition of plant residue to enhance soil organic matter may indirectly repress or lower salinity effect on Cd toxicity. Soil salinity decreased microbial biomass C and respiration with subsequent increases in specific respiratory quotient due to the increases in Cd solubility and availability. However, the changes in microbial properties were much lower in residue-amended and unamended soils. Addition of plant residue decreased the negative effects of both the individual and combined salinity and Cd pollution on microbial biomass and respiration. The interactive effect of these two stresses was mainly synergistic in residue-treated soils while it was antagonistic in residue-untreated soils. Overall, a strong synergistic effect occurred when both stresses were combined in the absence of plant residue while this effect was antagonistic in the presence of plant residue.
Conclusion: This study provided evidence that salinity could synergistically increase the mobility, bio-availability, and toxicity of Cd in Cd-polluted soils with C limitation. This was reflected by synergistic reductions in soil microbial biomass and respiration. However, addition of plant residue to increase soil organic matter lowered this effect of salinity, resulting in the antagonistic effects of salinity and pollution on soil microbial biomass and respiration. The reason for increase in the microbial activity in soils treated with plant residue was the increase of available substrate. As a result, using the plant residue increased the stimulatory effect of microbial activity. These findings point to the importance of providing adequate organic residues to enhance soil microbial performance and agricultural sustainability in polluted soils under salinity stress. However, further information on responses of microbial indicators to the joint effect of salinity and Cd toxicity is required.
Materials and Methods: This study was conducted under controlled laboratory conditions at Shahrekord University. A factorial experiment with two levels of cadmium (0 and 30 mg kg-1), three levels of salinity (1.35, 7.5 and 10 dS m-1) and two levels of plant residue (with and without alfalfa residue) was conducted using a completely randomized design with four replications. Using cadmium chloride salt, the soil was contaminated, and subsequently amended with alfalfa residue (1%, w/w). After thorough mixing of soil and plant residue, salinity treatments were applied using NaCl salt. To reactivate the microbial population and for the aging effect, soil moisture was set at 70% of field capacity, and containers were pre-incubated at room temperature for 4 weeks. Next, the samples were incubated at 25±1 oC for 98 days. Soil C mineralization (microbial respiration) was measured weekly, and available Cd and microbial biomass carbon were measured at monthly intervals. In this experiment, the Bliss independence model was used to determine the type and nature of the interaction between salinity and pollution (synergistic and antagonistic).
Results and Discussion: The results showed that NaCl salinity increased the concentration of soil available Cd in both polluted and unpolluted soils over the experimental period, and the increases were greater at high than low salinity levels. This effect of salinity was less pronounced in residue-amended and unamended soils. In general, a strong synergistic effect of both stresses was observed on Cd availability in residue-unamended soils while this effect was mostly antagonistic in residue-amended soils. This indicates addition of plant residue to enhance soil organic matter may indirectly repress or lower salinity effect on Cd toxicity. Soil salinity decreased microbial biomass carbon and respiration with subsequent increases in specific respiratory quotient due to the increases in Cd solubility and availability. However, the changes in microbial properties were much lower in residue-amended and unamended soils. Addition of plant residue decreased the negative effects of both the individual and combined salinity and Cd pollution on microbial biomass and respiration. The interactive effect of these two stresses was mainly synergistic in residue-treated soils while it was antagonistic in residue-untreated soils. Overall, a strong synergistic effect occurred when both stresses were combined in the absence of plant residue while this effect was antagonistic in the presence of plant residue.
Conclusions: This study provided evidence that salinity could synergistically increase the mobility, bio-availability, and toxicity of soil Cd in Cd-polluted soils with carbon limitation. This was reflected by synergistic reductions in soil microbial biomass and respiration. However, addition of plant residue to increase soil organic matter lowered this effect of salinity, resulting in the antagonistic effects of salinity and pollution on soil microbial biomass and respiration. The reason for increase in the microbial activity in soils treated with plant residue was the increase of available substrate. As a result, using the plant residue increased the stimulatory effect of microbial activity. These findings point to the importance of providing adequate organic residues to enhance soil microbial performance and agricultural sustainability in polluted soils under salinity stress. However, further information on responses of microbial indicators to the joint effect of salinity and Cd toxicity is required.
Research Article
Solmaz Kazemalilou; Nosratollah Najafi; adel reyhanitabar
Abstract
Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the ...
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Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the water conservation and increasing of water use efficiency through good management including integrated application of organic and chemical fertilizers and balanced nutrition of plants are necessary. One of the negative effects of water deficit stress is impaired uptake of nutrients such as phosphorus (P) by plants and a decrease in plant yield. It has been found that use of P can reduce the negative effects of drought stress on plants that means the tolerance of plants to drought stress increases with optimal nutrition of P. In Iran, due to the lack of organic matter and the high cost of chemical fertilizers, farmers tend to use organic wastes such as sewage sludge that can have an important contribution in the improvement of soil fertility and plant nutrition and lead to an increase in water use efficiency. Also, integrated and suitable nutrition of plants is a method of sustainable management of soil fertility under environmental stresses. Therefore, this study aimed to evaluate the effects of sewage sludge (SS) and triple superphosphate (TSP) on sunflower (Helianthus annuus L. cv. Farrokh) seed yield and its components and determining the optimal levels of their consumption under optimum and limited irrigation conditions.
Materials and Methods: This experiment was conducted as a split-plot factorial arrangement in a randomized complete block design in Agricultural Research Station of Khoy under field conditions for two years. Experimental factors were irrigation time at two levels (irrigation after 60 and 150 mm evaporation from class A evaporation pan), triple superphosphate at three levels (0, 100 and 200 kg/ha), sewage sludge at four levels (0, 14.2, 28.4 and 56.7 t/ha) and year at two levels (2014 and 2015) with three replications. The 1000 seed weight of sunflower, weight and number of seeds per plant, the percentage of empty achenes, head diameter and seed yield were measured at the end of plant growth period. Statistical analysis of the data was performed using MSTATC software and means comparison was done by Duncan’s multiple range test at 5% probability level.
Results and Discussion: The combined analysis of variances showed that the effect of year was significant for weight of seeds per plant, head diameter and seed yield but it is not significant for 1000 seed weight, number of seeds per plant and percentage of empty achenes. Although water deficit stress significantly increased the percentage of empty achenes but 1000 seed weight, weight and number of seeds per plant, head diameter and seed yield significantly decreased compared to optimum irrigation conditions. The application of integrated application of 200 kg TSP and 56.7 tons SS per ha increased yield and yield components significantly compared to the control treatment. The interaction effects of TSP×SS×irrigation were significant for all studied characteristics. Under optimum irrigation condition, the highest 1000 seed weight (64 g), weight of seeds per plant (85 g), number of seeds per plant (1513), head diameter (22 cm) and seed yield (5576 kg/ha) were observed in intergrated treatment of 200 kg TSP+56.7 tons SS/ha. Under limited irrigation condition, the highest 1000 seed weight (57 g), seeds weight per plant (81 g), seeds number per plant (1494), head diameter (19.6 cm) and seed yield (5322 kg/ha) were obtained from 56.7 tons SS/ha treatment which showed no significant difference with 100 kg TSP+56.7 tons SS/ha treatment. Under optimum and limited irrigation conditions, the percentage of empty achenes were significantly decreased by integrated treatments of 200 kg TSP+56.7 tons SS/ha and 100 kg TSP+56.7 tons SS/ha (70 and 81 percent, respectively) compared to the control.
Conclusion: The results of this study indicated that integrated application of triple superphosphate and sewage sludge can mitigate negative effects of drought stress; therefore in order to reduce the use of chemical fertilizers, increasing sunflower seed yield and development of sustainable agriculture, integrated treatments of 200 kg TSP+56.7 tons SS/ha under optimum irrigation and 100 kg TSP+56.7 tons SS/ha under limited irrigation can be recommended at similar conditions (from the aspect of soil, plant, sewage sludge and climate).
Research Article
reza mohajer; MOHAMMAD HASSAN Salehi
Abstract
Introduction: Increasing demand for an international classification system as a unique language in soil science has caused development of different classification systems. Soil classification is a useful tool for understanding and managing soils. In recent decades, the role of human in soil formation ...
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Introduction: Increasing demand for an international classification system as a unique language in soil science has caused development of different classification systems. Soil classification is a useful tool for understanding and managing soils. In recent decades, the role of human in soil formation has become a matter of great concern among soil scientists. Human is now considered as a soil-forming factor and anthrosolization is recognized as a soil-forming process that consists of a collection of geomorphic and pedological processes resulting from human activities. Industrial developments, mines and their activities and intensive agriculture led to soil changes in urban areas. One of the important missions of soils classification is to identify important properties which have effect on management purposes. In recent years, the importance of human impact on soil properties considered in soil classification systems like American Soil Taxonomy (2014) and World Reference Base (2015) and some revisions and changes have been made in this regard. In this study, the efficiency of American Soil Taxonomy and WRB soil classification systems soils were compared to describe the pollution of soils to heavy metals in Lenjanat region of Isfahan, Iran.
Materials and Methods: Agricultural lands located in Lenjanat region of Isfahan province were selected as the study area. Lenjanat is an industrial region in which intensive agriculture surrounded by different industries like steel and cement making factories and lead mining. Agricultural lands which consisted of five soil map units (Khomeini Shahr, Nekooabad, Isfahan, Lenjan and Zayandehroud) were selected and 400 topsoil samples were randomly collected. Six soil profiles were excavated in each map unit (totally 30 soil profiles) and after describing soil, the classification of soils was determined in the field. Then, representative pedons were chosen for each unit and routine soil morphological, physical and chemical properties were determined using common methods. Finally, the soil profiles were classified according to criteria of Soil Taxonomy up to family level and (WRB) at the second level. The amount of heavy metals was studied in some agricultural crops of the region and livestock muscles in the region. Total Cd and Pb were extracted from the soil samples using concentrated HNO3. Cadmium and lead of plant samples were prepared according to the procedure of Dry-ashing. Heavy metals were extracted by 3 N HCl. The metal contents of soil and plant samples were determined by flame atomic absorption spectrometry (FAAS). Descriptive statistics including mean, variance, maximum, minimum, and coefficient of variation (CV) were calculated using STATISTICA 6.0 software.
Results and Discussion: According to WRB (2015) classification, the soils were classified as 3 reference groups: Cambisols, Gleysols and Calcisols. The soils were also categorized as Aridisols and Inceptisols in Soil Taxonomy system. In this study, the environmental standards based on Swiss Federal Office of Environmental, Forest and Landscape were used for the threshold values of heavy metals pollution in the soils (VBBo). The results also indicate that the amount of cadmium in most of the soil samples was higher than the threshold limit. The amount of lead in soils was below the threshold limit. The results also indicated that all the crops had a lead average higher than the maximum of tolerance. The average of lead in cow and sheep livestock was also above Iran and Europe Union’s permissible limit. Despite American soil taxonomy classification system in the last version has a class (Anthraltic, Anthraquic, Anthrodensic, Anthropic) to show human impacts on soils at family level, it could not show the contamination of soils to heavy metals. However, WRB soil classification system defined qualifier “toxic” (Anthrotoxic, Ecotoxic, Phytotoxic, Zootoxic) which can be used in these conditions. Both systems had serious shortcomings to show poor drained soils in this area. Defining the Aquids suborder for Aridiosols in American Soil Taxonomy and revision of the definition of Gleysols, Anthrosols and also aquic conditions in WRB soil classification system are highly recommended.
Conclusion: The results indicated that WRB soil classification system could explain the soils pollution and also their effects on human health for the studied soils. Definition of some quantitative sub qualifiers for toxic can be useful to improve the efficiency of WRB for classifying polluted soils. Incorporating some criteria for pollution hazards in American Soil Taxonomy should be considered in early future.
Materials and Methods: To find out the effect of geological feature on delineation of homogeneous regions, 73 hydrometric stations at North-East of Iran with arid and semi-arid climate covering an average of 29 years of record length were considered. Initially, all data were normalized. Watersheds were clustered in homogeneous regions adopting Fuzzy c-mean algorithm and two different scenarios, considering and not considering a criterion for geological feature. Three validation criteria for fuzzy clustering, Kwon, Xie-Beni, and Fukuyama-Sugeno, were used to learn the optimum cluster numbers. Homogeneity approval was done based on linear moment’s algorithm for both methods. We adopted 4 common distributions of three parameter log-Normal, generalized Pareto, generalized extreme value, and generalized logistic. Index flood was correlated to physiographic and geographic data for all regions separately. To model index flood, we considered different parameters of geographical and physiological features of all watersheds. These features should be easily-determined, as far as practical issues are concerned. Cumulative distribution functions for all regions were chosen through goodness of fit tests of Z and Kolmogorov-Smirnov.
Results and Discussion: Watersheds were clustered to 6 homogenous regions adopting Fuzzy c-mean algorithm, in which fuzziness parameter was 1.9, under the two different scenarios, considering and not considering a criterion for geological feature. Homogeneity was approved based on linear moment’s algorithm for both methods, although one discordant station with the lowest data was found. For the case with inclusion of genealogic feature, 3-parameter lognormal distribution was selected for all regions, which is a highly practical result. On the other hand, for not considering this feature there were no unique distribution for all regions, which fails for practical usages. As far as index flood estimation is concerned, a logarithmic model with 4 variables of average watershed slope, average altitude, watershed area, and the longest river of the watershed was found the best predicting equation to model average flood discharge. Determination coefficient for one of the regions was low. For this region, however, we merged this region to other regions so that reasonable determination coefficient was found; the resulting equation was used only for that specific region, however. By comparing the distributions of stations and also two evaluation statistics of median relative error and predicted discharge to estimated discharge ration corresponding to 5 different return periods (5, 10, 20, 50, and 100 years). Both perspectives showed acceptable results, and including geological feature was effective for flood frequency studies. With considering the geological feature for regionalization, Besides, Log normal 3 parameters distribution was found appropriate for all of the regions. From this point of view, geological feature was useful. Median of relative error was lower for small return periods and gradually increased as return period was increased. Median of relative error was between 0.21 to 00.45 percentages for the first method, while for the second method it varied between 0.21 to 0.49 percentages. These errors are quite smaller than those reported in literature under the same climatic region of arid and semi-arid. The probable reason may due to the fact that we made a satisfactory regionalization via fuzzy logic algorithm., We considered another mathematical criterion of “predicted discharge to the observed discharge”. The optimum range for this criterion is between 0.5 and 2. While under-estimation and over-estimation are found if this criterion is lower than 0.5 and higher than 2, respectively. Based on this premise, 75 to 95 percentages of stations were categorized as good estimation under the first method of analysis. On the other hand, 78 to 97 percentages of stations were considered good for the second approach.
Research Article
Farzad Mondani
Abstract
Introduction: The DSSAT consists of a series of popular and widely used process-based crop growth simulation models. The models have been used worldwide to simulate crop biomass and yield, and soil nitrogen leaching under different management practices and various climatic conditions. The DSSAT has also ...
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Introduction: The DSSAT consists of a series of popular and widely used process-based crop growth simulation models. The models have been used worldwide to simulate crop biomass and yield, and soil nitrogen leaching under different management practices and various climatic conditions. The DSSAT has also proven to be a useful tool for selecting improved agricultural practices. Among all management agronomic factors, nitrogen fertilizer and crop species are major effective aspects impacting crops production. Although limited use of nitrogen fertilizer seems likely to reduce crop yield, high application rates of nitrogen causes serious adverse environmental effects. Thus, management of nitrogen fertilizer consumption decreases production costs and environmental pollution in agroecosystems. Therefore, the objectives of the present study were: (1) to determine the genetic coefficients and calibrate the CERES-Maize model (2) to evaluate the performances of the CERES-Maize model in simulating maize cultivars growth, development and grain yield for different fertilizer nitrogen application rates under Kermanshah climate condition.
Materials and Methods: This experiment was carried out in a split-plot design with 5 levels of nitrogen fertilizer application (0, 138, 238, 350 and 483 kg ha-1 urea) as main plots, 3 current maize cultivars SC-704, BC-678 and Simon as sub plots, and 4 replications in 2014. The required model inputs describe field management, daily weather condition, soil profile characteristics, and cultivar characteristics. The cultivar coefficients were obtained under optimum conditions (i.e., minimum stress in weather and nutrients). The genetic coefficients (P1, P2, P5, G2, G3 and PHINT) of the maize cultivars i.e. SC-704, BC-78 and Simon were determined using the GenCal software of DSSAT v 4.6 for 350 kg Urea ha-1 treatment (optimum nitrogen fertilizer amount based on the results of soil library). Model performance was evaluated by comparing simulated and measured values of maize cultivars phonological development stages (DVS), leaf area index, total dry weight and grain yield for independent nitrogen fertilizer treatment (0, 138, 238 and 483 kg Urea ha-1) by root mean square error (RMSE), normalized RMSE (nRMSE) and index of agreement (d).
Results and Discussion: The coefficients of P1, P2, P5, G2, G3 and PHINT ranged between 275 to 286 °C day, 0.576 to 1.80 days hr-1, 910 to 950 °C day, 940 to 990 number per plant, 7.0 to 7.9 mg day-1 and 51.70 to 51.97 °C day , respectively, for all cultivars. The CERES-Maize model was able to accurately simulate growth, development stages and yield for maize cultivars. For both simulated and measured conditions, leaf area index, total dry weight and grain yield were improved by increasing the application of nitrogen fertilizer. Simon cultivar had higher simulated (9925 kg.ha-1) and measured (10467 kg.ha-1) grain yield in respect to other cultivars. The validation results also indicated that the CERES-Maize model gave a reliable estimate of growth, development stages and grain yield for maize cultivars in the different fertilizer nitrogen application rates. The value of RMSE and nRMSE for leaf area index of SC-704, BC-78 and Simon cultivars were 0.56, 0.46 and 0.36 and 25.5%, 21.8% and 16.3%, respectively. The index of agreement (d) for leaf area index ranged from 0.94 to 0.98. The RMSE and nRMSE magnitudes for total dry weight of SC-704, BC-78 and Simon cultivars were 440.1, 569.6 and 419.7 and 6.2%, 8.2% and 5.8%, respectively. The index of agreement (d) for total dry weight ranged from 0.94 to 0.95. The RMSE and nRMSE values for SC-704, BC-78 and Simon grain yield were equal to 163.7, 345.2 and 314.4 and 4.3%, 11.4% and 8.1%, respectively. The index of agreement (d) for grain yield ranged from 0.93 to 0.98.
Conclusion: The results indicated that the CERES-Maize was parameterized reliably for three maize cultivars under Kermanshah climate conditions. The results of validation also showed that the CERES-Maize model was able to give an accurate simulation of all studied traits of maize cultivars except leaf area index in different fertilizer nitrogen application rates.
Research Article
Marjan Nekokhoo; Seyfollah Fallah; Rahim Barzegar
Abstract
Introduction: Water resources are very limited for agricultural production. Therefore, optimal use of available water resources and increased water use efficiency in agriculture are necessary. Application of poly ethylene mulch is one of the approaches that can be effective in increasing water use efficiency. ...
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Introduction: Water resources are very limited for agricultural production. Therefore, optimal use of available water resources and increased water use efficiency in agriculture are necessary. Application of poly ethylene mulch is one of the approaches that can be effective in increasing water use efficiency. The water deficient trend is increasing in agricultural lands of the Iran and, on the other hand, the yield components of hull-less seed pumpkin are sensitive to drought stress. Therefore, the aim of this study was to determine the effect of transparent polyethylene mulch on the performance and water use efficiency of hull-less seed pumpkin under different irrigation rates.
Materials and Methods: This experiment was carried out in the central part of Isfahan, Northern Baraan (320 and 32/N, 510 and 52/ E, and 1534 m above sea level) in a randomized complete block design with three replications, during 2016. Treatments consisted of full irrigation+ poly ethylene mulch (M+FW), 0.75% full irrigation+ poly ethylene mulch (M+0.75FW), 0.50% full irrigation+ poly ethylene mulch (M+0.5 FW), and full irrigation without mulch (FW). In April, the cultivation operations include mechanical planting, mulch were done. The spacing of the rows was 150 cm and the spacing between plants was 70 cm. The irrigation was applied until the plant was fully established and then drought stress was begun based on above irrigation treatments. The studied traits were number of fruits per plant, average fruit weight (kg), fruit yield (ton ha-1), number of seeds per fruit, fruit diameter (cm), 1000 grains weight (g), grain yield (kg ha-1), water use efficiency (kg m-3), oil content (%) and oil yield (kg ha-1). Statistical analysis was performed using SAS software and comparisons of the means were made using the least significant difference (LSD) test at the 5% probability level.
Results and Discussion: The highest number of fruits per plant belonged to M+FW treatment (with an average of 3.22) and the lowest was recorded in M+0.5FW treatment (with an average of 2.44). This difference between treatment FW and M+0.75FW can be due to the high moisture under the poly ethylene mulch. The highest fruit weight (3.60 kg) was obtained in M+FW treatments, which had a significant difference with other treatments. The difference weight of fruit in M + FW treatment was 14% compared to FW irrigation treatments. The highest fruit yield (95.72 ton ha-1) belonged to M+FW treatment and the lowest one (79.78) belonged to M+0.5FW treatment. The difference in fruit yield in M+0.75FW compared to FW treatment was 6%, but it was not significant. The number of seeds per fruit in M+0.75FW compared to FW and M+0.5FW treatments showed a difference of 13% and 17%, respectively which they were significant only with M+0.5FW treatment. With increasing drought stress, the amount of photosynthetic assimilate decreased, which reduced the number of seeds per fruit. The highest 1000 grains weight (173.13 g) belonged to M+FW treatment and the lowest one belonged to M+0.5FW (156.18 g). 1000 seeds weight in FW treatment was not significant compared to M+0.75FW treatment. Drought stress during plant development decreased the leaf area index in the plant. Application of plastic mulch reduces the effect of drought stress on leaf growth and its photosynthesis by decreasing water loss by evapotranspiration and transpiration. The difference grain yield between two treatments M+0.75FW with FW was 7% and this difference was not significant. Only significant difference was observed among M+0.5FW treatment with other treatments. The effect of different levels of moisture on water use efficiency was significant at 1% probability level. The highest water use efficiency was recorded in M+0.5FW treatment and the lowest was recorded in FW treatment. The difference in water use efficiency between M+0.75FW with full irrigation (FW) was 0.99 kg m-3, which was significant. Difference in water use efficiency between M+FW and FW was not significant for water use efficiency. The use of plastic mulch reduced water loss throughout the plant growth period and significantly increased water use efficiency. There was a significant difference among M+FW, M+0.75FW and FW for oil content. The highest and lowest oil contents belonged to M+FW and M+0.5FW, respectively. The maximum oil yield (558 kg ha-1) belonged to M+FW and the lowest one (412 kg ha-1) was obtained in M+0.5FW.
Conclusion: Transparent plastic mulch under water stress conditions can reduce the effect of drought stress on hull-less seed pumpkin by preserving water and other beneficial effects, including weeds reduction. Therefore, the use of this type of mulch is recommended for the cultivation of hull-less seed pumpkin in the central areas of the country facing the water crisis.
Research Article
Fatemeh Rakhsh; Ahmad Golcchin
Abstract
Introduction: Mobilization and stabilization of organic matter in soils represent a set of complex processes involving the processing and decomposition of organic matter by diverse communities of soil fauna and microorganisms, as well as chemical-physical interactions with mineral particles of soil. ...
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Introduction: Mobilization and stabilization of organic matter in soils represent a set of complex processes involving the processing and decomposition of organic matter by diverse communities of soil fauna and microorganisms, as well as chemical-physical interactions with mineral particles of soil. Clay minerals have high effects on the soil organic matter dynamics. Clay minerals with the physical protection of organic matter play an important role in reducing the rate of decomposition of organic matter. The effects of soil texture on the soil organic matter dynamics have been investigated in many studies, but the effects of exchangeable cations and clay types on mineralization of organic nitrogen and microbial biomass nitrogen have not been given much attention. For this reason, the aim of this study was to evaluate the effects of types and clay contents and exchangeable cations on the mineralization of organic nitrogen and microbial biomass nitrogen.
Material and Methods: Appropriate amounts of homoionic Na-, Ca- and Al- clays from Georgia kaolinite, Illinois illite and Wyoming montmorillonite were mixed with pure sand to prepare artificial soils with different clay contents, exchangeable cations, and clay types. The artificial soils have zero, 5 and 10% clay from Georgia kaolinite, Illinois illite and Wyoming montmorillonite that their clay minerals saturated with Ca, Na and Al. Alfalfa plant residues were incorporated into the artificial soils and the soils were inoculated with microbes from a natural soil and incubated for 60 days and concentration of NH4-N and NO3-N were measured every 15 days. In the artificial soil samples, microbial biomass nitrogen was measured by the fumigation-extraction method in the end time of incubation period.
Results and Discussion: The results of this study showed that the percentage of mineralized nitrogen in the two-month incubation period, was higher in the pure sand than in soils containing 5% and 10% clay, indicating that clay contents influence the capacity of soils to protect and store organic nitrogen. Microbial biomass nitrogen increased as the amount of clay in the soil increased. The highest and lowest amounts of microbial biomass nitrogen measured in soils with 10% clay (9.26 mg per 50 g dry soil) and pure sand (4.31 mg per 50 g dry soil), respectively. There was a significant influence of exchangeable cations on the percentage of mineralized nitrogen and microbial biomass nitrogen. The microbial biomass nitrogen and the percentage of mineralized nitrogen were highest in Ca-soils and lowest in Al-soils. The percentage of mineralized organic nitrogen in two months of incubation period was highest in soils with Georgia kaolinite clay and lowest in soil with Wyoming montmorillonite clay. The amounts of microbial biomass nitrogen in soils with Wyoming montmorillonite clay were lower than soils with Georgia kaolinite and Illinois illite clays. The percentage of mineralized organic nitrogen increased as the incubation period increased. The results of this study indicated that organic nitrogen mineralization rates and microbial biomass nitrogen were affected by types and clay contents and exchangeable cations and interaction of organic matter with clays and is an important process as it slows soil organic matter decomposition.
Conclusions: Mixing the alfalfa residues with artificial soils and incubation samples allowed to study the effects of types and clay contents and exchangeable cations on the percentage of NH4+-N, NO3--N, mineralized nitrogen, and microbial biomass nitrogen. Soils with different clay contents have different surface areas and cation exchange capacities; therefore, it is concluded that organic nitrogen storage of soils is, partly, controlled by the surface areas, cation exchange capacity and physical protection provided by the soils. Nitrogen mineralization and the amounts of microbial biomass nitrogen were different in soils with different exchangeable cations. It is concluded that exchangeable cations exert their influence on microbial biomass and hence nitrogen dynamics by controlling the size and activity of the microbial population through modifying the physicochemical characteristics of microbial habitats. Since various clay minerals have different specific surface areas and cation exchange capacity and the physicochemical changes induced in the soil environment as a result of variations of exchangeable cations is much greater in soils with higher cation exchange capacity and specific surface area. It seems the effects of clay mineralogy on the dynamics of organic materials and microbial biomass, in part, arise from the type of exchangeable cations present on the exchange sites of the clay minerals.
Research Article
Vida Hemmati; Hadi Asadi Rahmani; Shokofeh Rezaee
Abstract
Introduction: Wheat is one of the most important food crops. In modern agriculture, due to the increase in human population and the detrimental effects of pesticides such as environmental pollution, concerns about human and animal health, adapting suitable alternatives which have none of these dangerous ...
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Introduction: Wheat is one of the most important food crops. In modern agriculture, due to the increase in human population and the detrimental effects of pesticides such as environmental pollution, concerns about human and animal health, adapting suitable alternatives which have none of these dangerous effects would be necessary. This is possible by increasing the production of bio-fertilizers. Plant growth-promoting rhizobacteria (PGPR) are the beneficial rhizosphere bacteria that can enhance plant growth directly or indirectly through a wide variety of mechanisms. PGPR can stimulate plant growth directly by supplying nutrients such as phosphorous and nitrogen or by the production of phytohormones such as auxins, cytokinins (CK), gibberellins (GAs) or ACC deaminase synthesis. They can also promote plant development indirectly by the suppression of pathogens by different mechanisms such as biosynthesis of antimicrobial molecules or antibiosis induced systemic resistance (ISR), rhizosphere competition, cell wall degrading enzymes like chitinase and HCN production. In this study, amplified ribosomal DNA restriction analysis was performed for screening the bacterial isolates. Then phosphate solubilization, siderophore and auxin release activities and effect of bacterial isolates on wheat seed germination traits were studied.
Materials and Methods: In order to isolate wheat rhizosphere bacteria, soil samples were taken from the wheat rhizosphere of Tehran, Qazvin, Zanjan, West and East Azerbaijan, Kurdistan and Hamadan provinces. Genomic DNA of each isolate was extracted by using a modified cetyl trimethylammonium bromide (CTAB) method. Amplified ribosomal DNA restriction analysis with HpaII and RsaI restriction enzymes was done for genetic screening. Growth stimulating factors were evaluated by auxin production, siderophore production, and inorganic phosphate solubilizing activity. Siderophore production was determined by measuring the diameters of the colony (mm) and of any orange halo (mm) formed from the blue medium surrounding bacterial growth on CAS Blue Agar medium. To examine Pi solubilization capability, 2µ bacteria suspension was placed on the plates containing Sperber’s medium. Cultures were incubated at 25 ± 2 °, when the diameters of the colony and of the halo zone surrounding it were measured and the mean ± SE of the ratios of halo (mm)/colony (mm) calculated. In order to evaluate the production of auxin, isolates were grown in 100ml flasks containing 25ml TSB medium for 48h on a rotary shaker. 1 ml supernatant was mixed with 2ml of Salkowsky reagent after centrifugation at 10000g for 15min. The absorbance of the complex was read at 535nm in a Spectrophotometer. To investigate the effect of bacterial isolates on germination traits, radicle and plumule fresh and dry weight, radicle and plumule length, germination percentage, germination rate, and germination average rate were measured. The data were analyzed with using SAS 9.1. Mean comparisons were performed by LSD and main effective interaction was found significant at P < 0.05.
Results and Discussion: 20 isolates of wheat rhizosphere bacteria were subjected to amplified ribosomal DNA restriction analysis. The 16S rDNA region was amplified by polymerase chain reaction and PCR products were digested by HpaII and RsaI restriction enzymes. From each pattern, one sample was sent to sequencing. Different species including; Chryseobacterium ginsenosidimutans, C. lathyri, C. piperi, C. taiwanense, Novosphingobium aromaticivorans, Pedobacter duraquae, and Sphingomonas koreensis were identified from the wheat rhizosphere. Bacteria were tested for their plant growth promoting qualities. All of the strains produced auxin from 1.90 to 25.93. Mean comparison of the data showed that the highest level of auxin was produced with F1 and the lowest amount was observed by F18. Phosphate solubilization measured as a halo zone on Sperber’s medium was observed with F6 and F56 isolates. The ratio of the diameter of the halo zone to the colony diameter was 2.86 with F6. The highest level of siderophore production by wheat rhizosphere bacteria, observed as halo formation around colonies on CAS Blue Agar medium, was obtained with F46, followed by F45 and F3. The ratio of the diameter of the orange halo surrounding bacterial growth to the colony diameter was 2.86 with F46. The result showed that the effect of wheat rhizosphere bacteria on germination traits such as radicle fresh and dry weight, plumule fresh weight, radicle and plumule length, germination percentage, germination rate, and germination average rate was significant at the one percent level and the effect of wheat rhizosphere bacteria on plumule fresh weight was significant at the five percent level.
Conclusion: Plant growth promoting bacteria enhance the growth and development of plants with different ways. These bacteria affect the growth and development of crops by phosphate solubilization, production of hydrogen cyanide, siderophore, and hormones such as auxin, gibberellic acid and cytokinins. According to the result, due to growth promoting characteristics such as siderophore and auxin production, phosphate solubilization, and the improvement of the seed germination traits, it can be possible to prepare bacterial inoculant for the field experiment in order to increase the availability of nutrients and improve the growth of plants.
Research Article
Leili Neghadzamani; Mohammad Hady Farpoor; Azam Jafari
Abstract
Introduction: Genesis and development of soils are highly affected by soil forming factors and processes. Climate and topography (landform) are among the factors affecting weathering of parent material and genesis and development of soils in an area. Besides, various morphological, physical, and chemical ...
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Introduction: Genesis and development of soils are highly affected by soil forming factors and processes. Climate and topography (landform) are among the factors affecting weathering of parent material and genesis and development of soils in an area. Besides, various morphological, physical, and chemical properties, micromorphology, and clay mineralogy of soils at different geomorphic positions are usually affected by different soil forming factors including parent material and climate. The objectives of the present research were to study the effect of climate and geomorphology on physicochemical properties, micromorphology, and clay mineralogy of the soils in Rayen area, Kerman Province.
Materials and Methods: The study area starts from Hezar mountain elevations close to Rayen city (south east of Kerman Province) and extends to plateaus surfaces around Bam city. Quaternary and Neogene formations were found from geology point of view. Mean annual precipitation is in the range of 200-300 mm. Five landforms including rock pediment, mantled pediment, piedmont plain, plateaus, and valley were investigated during field work followed by topography, geology, and Google map studies in the area. According to 1:2500000 map provided by Soil and Water Research Institute, xeric and aridic soil moisture regimes together with mesic soil temperature regime were found in the area. Nine representative pedons were studied based on climatic regimes and different geomorphic surfaces. Pedons 1 and 2 were located on rock pediment with an aridic soil moisture regime. On the other hand, pedon 3 was located on the same surface, but with xeric moisture regime. Pedons 4 and 5 were also located on mantled pediment with aridic and xeric moisture regimes, respectively. Pedon 6 was located on piedmont plain and in the aridic moisture zone. Pedons 7, 8 (Plateaus), and 9 (Valley) were all in the aridic moisture zone. Physical and chemical properties, micromorphology, and clay mineralogy of soils were investigated and the soils were classified using USDA Soil Taxonomy (12th edition) and latest edition of World Reference Base for Soil Resources (WRB) systems.
Results and Discussion: Cambic, gypsic, argillic (or argic), calcic, and petrocalcic horizons were investigated during field and laboratory studies. Typic Haplocambids (pedons 1 and 2), Typic Calcixerepts (pedon 3), Typic Torriorthents (pedon 8), Calcic Petrocalcids (pedon 7), Typic Calcigypsids (pedon 6), Typic Xerorthents (pedon 5), Typic Haplocalcids (pedon 4), and Typic Calciargids (pedon 9) were classified using Soil Taxonomy (2014) and Gypsisols (pedon 6), Calcisols (pedons 3, 4, 7, and 9), Cambisols (pedons 1 and 2), and Regosols (pedons 5 and 8) Reference Soil Groups were determined using WRB (2015) system. Electrical conductivity increased from rock pediment toward valley and decreased from aridic toward xeric soil moisture regimes. Formation of argillic horizon in pedon 5 (Xeric moisture regime) was attributed to the climate of present time, but pedons 8 and 9 with aridic moisture regime could probably have experienced a climate with more available humidity for argillic horizon to be formed. Besides, petrocalcic horizon formation in pedon 7 was also attributed to a climate with more available humidity in the past. A buried soil (Btkb horizon) was determined in pedons 5 and 8 under the modern soil. Soil moisture regime change from aridic to xeric in rock pediment surface caused change of Aridisol to Inceptisol, but classification of soils in WRB system, was not affected. Secondary forms of calcium carbonate including powdery pocket, soft masses, and mycelium and secondary gypsum such as fine and coarse pendants were found during field studies. Calcite, gypsum, and clay coatings and infillings together with isolated gypsum crystals and gypsum interlocked plates were among dominant micromorphological pedofeatures investigated. Calcite coatings on aggregates and soil particles associated with clay coating prove the role of paleoclimate in soil formation. On the other hand, presence of manganaze nodules is an evidence of oxidation/reduction condition taken place in the xeric moisture conditions of pedon 5 (rock pediment). Illite, chlorite, kaolinite, and smectite were investigated in both rock and mantled pediments, but palygorskite was only found in mantled pediments. Climate also played a significant role in determining the source (pedogenic or geogenic) of clay minerals.
Conclusions: Results of this study clearly showed the close relationship among soil formation, topography (geomorphic surface) and climate. Soil physicochemical properties, micromorphology, clay mineralogy, and soil classification were highly affected by climate and geomorphology.
Research Article
sanaz ashrafi saeidlou; Mirhasan Rasouli-Sadaghiani; Abbas Samadi; mohsen barin; ebrahim sepehr
Abstract
Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most ...
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Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most soils. Regarding that low molecular weight acids (LMW) play an important role in improving the bioavailability of soil nutrients such as non-exchangeable K (NEK), and the release rate of NEK plays a significant role in supplying necessary K for plants, the purpose of this study was comparison of potassium release kinetic from K-bearing including feldspar, illite as well as phlogopite minerals and choose the best kinetic equation describing potassium release process, influenced by organic as well as mineral extractants.
Material and Methods: The experiment carried out in a completely randomized design with three replications. Experiment factors were including extractant type (0.01 mol l-1 oxalic acid, 0.01 mol l-1 calcium chloride, control (deionized water)), potassium mineral type (feldspar, illite and phlogopite) and incubation time (1, 2, 4, 8, 12, 16, 24, 32, 48, and 64 hours). Elemental composition of minerals identified by Fluorescence spectroscopy device (S4 Pioneer). Used minerals in the experiment including feldspar, phlogopite and illite were ground and filtered through a 230 mesh sieve. In order to remove exchangeable K, samples were saturated by calcium chloride solution (with a ratio of 2:1), after washing with HCl, samples were dried at 105 °C for 48 hours. 100 mg of washed minerals, was weighed carefully and transferred to centrifuge tubes. Then 20 ml of each of extractants (oxalic acid and calcium chloride 0.01M) was added to the tubes. After 15 minutes shaking, tubes containing a mixture of minerals-extractants was carried out in a controlled incubation chamber for periods of 1, 2, 4, 8, 12, 16, 24, 32, 48 and 64 hours at 25 °C. After each period, samples were centrifuged at 3000 rpm for 10 minutes and filtered using Whatman paper (No. 41). pH and potassium concentration of samples were measured by pH meter and flame photometer, respectively. Data related to potassium release was fitted by zero order, first order, second order, power function, parabolic diffusion and ellovich equations.
Results and Discussion: Results showed that the effect of extractant type was significant on kinetic of potassium release, so that potassium release amount in samples extracted with oxalic acid was 1.48 and 2.35 times higher than samples extracted with calcium chloride and control (deionized water), respectively. Also, different minerals released various amounts of potassium. K release from phlogopite was 1.99 and 2.95 times higher than feldspar and illite, respectively. The maximum potassium concentration (440 mg kg-1) was seen in phlogopite which was extracted with oxalic acid. So that, amount of potassium in this treatment was 3.15 times higher than control one. Furthermore, the effect of extraction time on K release was significant. So that, at the beginning of incubation period the release of potassium by different extractants was more, but its amount decreased over time and finally continued with a constant speed. Kinetic equation fitting showed that zero order, first order, power function, parabolic diffusion and ellovich equations are able to describe potassium release but second order model cannot justify it. Among these five equation, the power function and parabolic diffusion equations with the maximum coefficient of determination (R2) and the least standard error of estimate (SE), could reasonably describe the K release kinetics, so they are introduced as the best models for data fitting. The slope (b) and interception (a) of ellovich equation indicate interlayer and initial K release, respectively. Oxalic acid and phlogopite had the most amount of interception, it means that the impact of oxalic acid on initial and interlayer release rate of K in phlogopite, is more effective than calcium chloride.
Conclusions: It is concluded that different factors like mineral and extractant type influence kinetic of potassium release and organic extractant have more ability in extracting non-exchangeable potassium from minerals structure. Also, the adjustment of the results of this study with first order, parabolic diffusion and power function equations suggest that nonexchangeable potassium release from minerals can be affected by diffusion process from the surface of the study minerals, indicating that NEK release rate is controlled by K diffusion out of the mineral interlayer.
