Journal of Soil Management and Sustainable Production
Year:2016 | Volume:6 | Issue:1|Papers Count:15

Background and Objectives: Zinc (Zn) is one of the most important essential nutrients that plants require it for their physiological and generation functions. The low bioavailability of Zn is in calcareous and saline soil, therefore the study of chemical forms and bioavailability of Zn in these soils is necessary to estimate the potential availability. The objective of this study was to evaluate the effect of plant growth promoting rhizobacteria and mycorrhizae fungi inoculation on the chemical forms of Zn in a calcareous soil at different salinity levels after harvesting corn by a sequential extraction method.Materials and Methods: In order to do this study, apporpirate amount of surface soil (0-30 cm) that had low organic matter and electerical conductivity, was collected and then, selected physicochemical properties of soil were measured by laboratory standard methods. A factorial experiment as a completely random design with three replications was conducted in greenhouse conditions. The first factor consisted of three salinity levels (0, 15 and 30 Meq salt kg-1 soil) and the second factor was microbial inoculation (without inoculation, Glumus Intraradices, Pesudomonas bacteria and fungi+bacteria). After applying treatments, corn seeds (Zea mays L.) were planted in plastic pots and held for 10 weeks. Sequential extraction procedure of Sing et al. (1988) was used to measure chemical forms of Zn in soil after corn harvesting. The Zn was separated into 7 fractions by this method that include WsEx-Zn, Car-Zn, Om-Zn, MnOx-Zn, AFeOx-Zn, CFeOx-Zn and Res-Zn.Results: The results showed that increasing salinity levels increased the concentrations of soluble+exchangeable, carbonatic and manganese oxide fractions and the concentrations of residual and organic fractions decreased. By application of all microbial treatments, the concentration of soluble+exchangeable, carbonatic and manganese oxide fractions increased and the concentration of residual fraction declined. The higher increase of concentrations of soluble+ exchangeable (101%), carbonatic (59.3%) and manganese oxide (100%) fractions were observed in co-inoculation of bacteria and fungi treatment. There were positive and significant correlation between soluble+exchangeable, carbonatic and manganese oxide fractions with DTPA extractable Zn which indicates the role of these fractions in the supply of Zn to plant.Conclusion: Results showed that the biological treatments caused the redistribution of Zn from low available fractions to high available fractions in soil. Also, increasing soil salinity levels caused the redistribution of Zn from insoluble fractions to more soluble fractions and therefore, the mobility of Zn in soil increased.

Background and objectives: The phosphorus is second limiting nutrient in soil for crop production after nitrogen. Mobility and availability of phosphorus (P) in soils is affected by phosphorus desorption characteristics. Information about the effect of organic matter on kinetics and thermodynamics of P desorption in calcareous soils of East Azerbaijan province is limited.The objective of this study was to evaluate the effect of organic matter on phosphorus desorption kinetics and thermodynamics parameters. P desorption kinetics and thermodynamic was studied in 4 soil samples (0-30 cm) collected from East Azerbaijan province before and after organic matter removal by NaOCl.Materials and Methods: To study general characteristics, 4 soil composite samples (0-30) were selected so that as much as possible had a wide range of SOM, available P and sand and clay content. Soil samples were air dried, to pass a 2 mm sieve and some physical and chemical properties analysed. Desorption kinetics of P was studied at 100 mg P L-1 solution as initial concentration with CaCl2 0.01 M solution before and after SOM removal. Statistical analysis using SPSS software and fitting nonlinear kinetics equations were performed by using Data fit software.Results: The P desorption kinetics were best described by a simple Elovich equation (r2≥0.94).The mean values of constant “lnas“ was 9.69 before organic matter removal and 8.05 was after organic matter. According to the results, P desorption pattern based on the simple Elovich equation revealed that the rate of P desorption was higher in the first 2 hours followed by a slower release rate, which may suggest two different mechanisms are involved. To evaluate temperature effects, desorption thermodynamics of P was studied at various temperatures of 10, 20, 30 and 40 0C. Results suggested that the P desorption, before and after SOM removal, was a spontaneous and endothermic process. The positive values of enthalpy for the retention of P, indicated that the retention process was endothermic. The mean values of DG0 ranged from -32.12 to -39.3 KJmol-1 in NaOCl untreated soils, while it ranged from -33.05 to -40.21 KJmol-1 in NaOCl treated soils when temperature increased from 100C to 400C.Conclusion: Regarding the rate of P retention by soil and decreasing P desorption after SOM removal, application of organic matter, or at least prevent its loss can increase efficiency and rate of P release to soil solution.

Background and Objectives: Soil salinity and Zn deficiency are among the most important limiting factors for growth and yields of pistachio trees in many regions of Iran, especially in the Rafsanjan area. The use of plant growth promoting rhizobacteria (PGPR) is new strategies to reduce destructive effects of salinity and improvement of nutrient availability. This study investigated the interactive effect of the fluorescent pseudomonads rhizobacteria and Zn on the fractionation and availability of Zn in the rhizosphere soil and uptake of Zn by shoot of pistachio seedlings (cv. Badami) under salinity condition.Materials and Methods: A greenhouse experiment was conducted in a factorial experiment based on completely randomized design with three replications in order to evaluate the interactive effect of fluorescent pseudomonads rhizobacteria (pf0 (non-inoculated control), pf1, pf2 and pf3) and Zn application (0 and 5 mg Zn kg-1) on the Zn fractionation in the different levels of soil salinity (0 (1.46 dS m-1), 1000 (7.32 dS m-1) and 2000 (12.0 dS m-1) mg NaCl kg-1 soil) and its relationship with concentration and uptake of Zn in the pistachio seedlings (Pistacia Vera L. cv. Badami) shoot.Results: The results indicated that salinity and inoculation with fluorescent pseudomonads increased the DTPA- extractable Zn (DTPA-Zn) content and the forms of water soluble plus exchangeable (WSEXC) Zn, carbonate-bound (CA) Zn and organic matter-bound (OM) Zn, while decreased Fe-Mn oxide-bound (FeMnOX) Zn and residual (RES) Zn in the rhizosphere soil.Inoculation by fluorescent pseudomonads increased the DTPA-Zn, WSEXC-Zn, CA-Zn and OM-Zn contents by 52, 26, 29 and 35%, respectively but decreased FeMnOX-Zn and RES-Zn contents by 24 and 3%, respectively. Also, Zn application significantly increased all forms of Zn (except residual form) in the soil. The results showed that salinity reduced the concentration and uptake of Zn in the pistachio seedlings shoot, while inoculation with fluorescent pseudomonads and treatment with Zn incrased its contents at all salinity levels. However, the combined application of the fluorescent pseudomonads and Zn were more effective. There was a positive and significant correlation between Zn uptakes by shoot and DTPA-Zn, WSEXC-Zn, CA-Zn and FeMnOX-Zn. As well as, soil salinity and inoculation by fluorescent pseudomonads reduced pH value of rhizosphere soil from 7.73 to 7.46 and 7.59, respectively.Conclusion: The results showed that soil salinity increased Zn availability in the rhizosphere soil, while reduced the concentration and uptake of Zn by pistachio seedlings shoot due to reduction of root volume, water availability and high content of Na+ion. Thus, the use of superior isolates-especially Zn solubilizing bacteria- can effectively increase the availability of Zn in soil and uptake of Zn by plants through increasing root growth. However, WSEXC-Zn, CA-Zn and FeMnOX-Zn could be used as available fractions of pistachio seedlings.

Background and Objectives: Sequential extraction methods of Sposito et al. (method A) and Tessier et al. (method B) are distinguished from other methods by simplicity and popularity, respectively. Method B first was tested in two fluvial deposits and then widely used in all sediments, sludge compost and heavy metal contaminated soils. Method A basically was proposed for determination of chemical forms of metals in sludge, soils incubated with sludge and wastewater irrigated soils. However, thereafter the method was used in contaminated soils around of mines and smelters. Some researchers reported that washing heavy metal contaminated soils by strong complexing agents like EDTA lead to transformation of heavy metals from low-mobile to highmobile forms. There are several environmental concerns regarding abandoned contaminated soils after washing. Therefore, study of effective factors on removal of heavy metals from high-mobile forms is of importance for using of these complexing agents either in washing or phytoremediation.In the current study, attempts were made to investigate the distribution and mobility of Zn, Pb and Cd in contaminated soils before and after batch extraction by EDTA.Materials and Methods: Three soil samples with different heavy metal contents were taken from 0-20 cm depth of the zinc-lead smelting plant area in Zanjan. Some physical and chemical characteristics of the soils were determined. Thereafter, the chemical forms of Zn, Pb and Cd in the soils were determined before and after batch extractions by 0.1 mole of EDTA per one kilogram of soil using two methods of Sposito et al. (1982) (method A) and Tessier et al. (1979) (method B). The extraction percentage, form distribution, removal efficiency and mobility factor of the heavy metals were determined using two above mentioned methods and then compared.Results: The results indicated the higher effectiveness of hot nitric acid in extraction of Cd and in turn the higher effectiveness of aqua regia in extraction of Zn and Pb. The method A, particularly carbonate form, showed major removal after washing. The sum of different forms introduced carbonate and residual forms as dominant form for all three metals in all three soils. In addition, these forms of a given heavy metal obtained from the method A were greater than that of method B.Unlike the method A, in which the dominant removal of Pb by EDTA was from the carbonate form, this removal was from the oxide form in the method B. Also, unlike the method A, in which the exchangeable forms of the metals increased after washing, some severe decreases were observed in the method B. Also, the highest and lowest removal efficiencies were observed for Cd (using method A) and Pb (using method B), respectively. The mobility factor of Zn after batch extraction by EDTA intensely decreased. Additionally, the mobility factor of Pb after extraction significantly increased.The mobility factor of Cd after washing almost decreased.Conclusion: The results indicate the influence of residual amount of EDTA in washed soils on determination of chemical forms of heavy metals. Therefore, care in interpretation of data from determination methods of heavy metal chemical forms, particularly in washes soils is necessary.Both of two methods revealed the increased mobility of Pb in soils after washing. This emphasizes using auxiliary procedures such as phytoremediation for decontaminating soils after washing.

Background and Objectives: The interaction between microorganisms, especially fungi and bacteria can have very effective impacts on the growth and nutrition and improve the plants yield. This study was done to investigate the effect of arbuscular mycorrhizal fungi and bacteria Pseudomonas, Rhizobium interaction on growth, yield and plant nutrition of common beans.Materials and Methods: In order to investigate the effects of the inoculation with P. putida, R. leguminosarum bv. phaseoli and F. mosseae on yield and nutrient uptake of Common Bean (Phaseolus vulgaris L.), a greenhouse experiment in a completely randomized factorial design with 3 treatments including a: microorganism in four levels (no inoculation, P. putida, F. mosseae and mix inoculation of fungi and bacteria), B: Zn in two levels (0 and 10 mg.kg-1) and C: Nitrogen in two levels (inoculation with R. leguminosarum and adding 70 mg.kg-1 nitrogen in form of NH4NO3) with four replications was conducted.Results: The results of experiment indicated that the concentration of P, K, Zn, Cu and Mn in shoots of plants and shoot dry matter, shoot wet matter, seed dry weight, seed number and thousand seed weight affected by simultaneous inoculation of F. mosseae and P. putida. The concurrent inoculation of F. mosseae+P. putida+R. leguminosarum bv. phaseoli significantly increased the Mn concentration in shoots of plants and seed number. Uptake of N, P, K, Fe, Zn, Cu and Mn significantly affected by synchronous inoculation of F. mosseae and P. putida.The concurrent inoculation of F. mosseae+P. putida+R. leguminosarum bv. Phaseoli had no significant effect on nutrient uptake.Conclusion: Maximum thousand seed weight was obtained in rhizobium treatment which represents the role of effective and efficient rhizobium bacteria in reduction of nitrogen fertilizers use without yield loss.

Background and Objectives: Study of soil quality indicators are considered as a useful method in the land use management. Changing the land use affect soil hydrological processes such as water infiltration process. Spatial variation of water infiltration in soil plays a very important role in hydrologic processes. Variability of this process is affected by the inherent and non-inherent characters of the lands. In order to prevent land degradation and soil and water pollution, realizing the respective processes and quantifying their relationships is unavoidable.Infiltration process is one of the most important components of the hydrological cycle. Due to high changes in soil moisture, providing a suitable model for the accurate estimation of infiltration is important. The aim of this study is to evaluate the infiltration characteristics due to land use changes and to determine the best water infiltration model.Materials and Methods: Therefore, water infiltration into soil was measured in seven areas of Zanjan province and one area of Ardabil province at three agricultural, horticultural and bare land uses. Measurement of the water infiltration rate in each land use was conducted by double ring method with three replications and at times 0.16, 0.33, 0.5, 0.66, 0.83, 1, 2, 3, 4, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 110, 120, 135, 150, 165, 180, 195 and 210 minute. Also Kostiakov, Kostiakov-Lewis, Horton and Soil Conservation Service of America models were used to estimate soil water infiltration rate. In order to choose a suitable model, RMSE (root mean square error) and R2 (determination coefficient) criteria were determined for each model. Cumulative infiltration and final infiltration rate were determined for each land use.Results: The results showed that in all three users, all models used in this study could estimate cumulative infiltration water in the soil with acceptable accuracy and low RMSE and high R2.This study suggests estimation of infiltration using models and interpretation of them as logical for all areas study. Also the results showed that the estimated cumulative infiltration of the bare land use by Horton model had maximum R2 (0.999). But in cultivated and horticultural land use by Kostiakov-Lewis model maximum R2 (0.997) was achieved. According to results the cumulative infiltration and final infiltration rate in cultivated and horticultural land use were higher than those of bare lands. This was mainly due to role of plant, causing more disturbance of the soil surface layer, thus infiltration in the cultivated and horticultural land use is higher than bare lands (in which human factors were less effective).Conclusion: Generally the results of this study showed that cumulative infiltration means in cultivated and horticultural land use were higher than those of bare lands. Also estimation of infiltration using models and interpretation of them is suggested to be logical for all study areas and Horton model to the rest of the models with high accuracy.

Background and Objectives: The biological and chemical conditions of the rhizosphere are known to considerably differ from those of the bulk soil, as a consequence of a range of processes that are induced either directly by the activity of plant roots or indirectly by the stimulation of microbial population and activity in the rhizosphere. Information about phosphorus (P) fractionation in the rhizosphere soils amended with municipal sewage sludge (MSS) is limited. Thus, the objectives of this research was to evaluate the rhizospheric effects of wheat (Triticum aestivum L.) on the status of various inorganic P fractions, total organic P and some biological properties in 10 calcareous soils amended with 1% (W/W) municipal sewage sludge from the refinery of Shahrekord city under rhizobox conditions.Materials and Methods: Wheat was planted in completely randomized design with three replications. Eight weeks after germination, plants were harvested, rhizoboxes were dismantled and the rhizosphere and bulk soils were separated. P fractions were determined by modified Olsen and Sommers' sequential fractionation procedure. Also, acid (ACP) phosphatases, available P were measured.Results: The results showed that wheat rhizosphere showed a significant depletion of available P, non-occluded P, occluded P, organic P and residual P fractions and a significant increase of calcium phosphate fraction. Also, the results showed that the activity of acid phosphatas considerably increased in wheat rhizosphere soils when compared to the bulk soils. Simple correlation coefficients showed that plant indices have positive relationship with non-occluded P, occluded P and calcium phosphate fractions in the rhizosphere and bulk soils (p<0.05).Conclusion: The results indicated that in addition to Olsen P (labile-Pi) and non-occluded P, occluded P, calcium phosphate could also act as a short-term source of wheat-available P in the calcareous soils amended with MSS.

Background and Objectives: Rice is one of the oldest cultivated plants in the world and plays a significant role in feeding the people in world as in Iran. One of the soil management approaches in improving the low native soil fertility of soils is the application of municipal solid waste compost and biochar. As, the application of these two amendments in Iranian calcareous soil is not yet studied, the main objective of this research is to test the performance of concurrent application of biochar and compost in paddy field on rice leaves nutrient.Materials and Methods: The effects of different application rates of municipal solid waste compost (MSWC) and biochars derived from rice straw (RSB) and biochars derived from sugarcane bagasse (SBB) at 350 °C on the nutrients concentration (N, P, K, Cu, Zn, Fe and Mn) of rice leaves was investigated in a greenhouse experiment. The MSWC at four levels (0, 10, 20 and 30 g per kg soil) and biochars at three levels (0, 3 and 6 g biochars per kg soil) were incorporated to the soil. The experiment was conducted as factorial arrangement based on randomized complete block design with three replications.Results: The highest amount of nitrogen (4.05%) was observed in the treatment of 6 gr RSB+30 gr MSWC per kg soil, while the minimum amount of nitrogen was obtained in the control treatment. The P concentration in 6 gr SSB+30 gr MSWC per kg soil treatment was two times more than P in the control treatment. The P concentration of leaves increased with increasing the MSWC application in all applied biochar levels. The maximum and minimum concentrations of K were observed in the 6 gr RSB+30 gr MSWC per kg soil treatment and control treatment, respectively. The maximum concentration of Cu was observed in the treatment of 6 gr RSB per kg soil. The maximum concentration of Zn (27.49 mg kg-1 plant) was observed in the treatment of 20 gr MSWC+3 gr RSB per kg soil. The Fe concentration of rice leaves increased with increasing the biochar application in all applied MSWC levels. There was also maximum manganese in the treatment of 6 gr RSB per kg soil.Conclusion: Overall, this study showed that the co-application of MSWC and biochar (RSB and SBB) has a great impact on improvement of the rice leaves nutrients in the paddy calcareous soils.

Background and Objectives: Recently using microorganisms, including plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) for improving plant growth and nutrition has been widely considered. Plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi can enhance plant growth by increasing nutrient uptake. The effect of biofertilizers on growth and yield of medicinal plants was studied extensively in the world, but behavior of medicinal plants in such conditions has not been studied well in Iran. This research investigates the effect of PGPR and AMF on some morphological parameters (root colonization percentage, shoot and root dry weight), macro (nitrogen, phosphorus, potassium, calcium and magnesium) and micro (iron, zinc and copper) nutrients uptake, percentage of root colonization and some morphological factors of peppermint.Materials and Methods: The greenhouse experiment was conducted as a complete randomized design with nine replications by using the three species of AMF (Glomus fasciculatum, Glomus intraradices and Glomus mosseae) and three bacterial species treatment as PGPR (Azotobacter, Bacillus and group of Fluorescens Pseudomonas contain of Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida) and control (non bacterial-mycorrhizal) in gricultural college of aurmia university.Results: The results showed that the application of PGPR and AMF had significant effect (P≤0.05) on root and shoot dry weight and nutrients uptake compared to control. The highest values of root dry weight and root colonization percentage were seen in plants inoculated with Glomus fasciculatum. Maximum uptake of nitrogen (140 mg pot-1) was obtained at Azotobacter, while Maximum uptake of phosphorus, potassium and magnesium uptake (54.1, 731 and 280 mg pot-1, respectively) were observed at Pseudomonas treatment. The highest values of calcium, iron, zinc and copper uptake (418, 0.177, 0.048 and 0.050 mg pot-1, respectively) were achieved at Glomus fasciculatum treatment.Conclusion: The results showed that using of PGPR and AMF can have useful role in improving the absorption of nutrients and morphological parameters in peppermint. Based on the experimental results, it could be concluded that suitable status of PGPR and AMF plants was due to increased root absorption area and finally proper nutrition and better performance.Also, according to the results, PGPR and AMF could be used in greenhouse cultivation of medicinal herbs, especially peppermint.

Background and Objectives: Primary and secondary soil salinization is one of the main reasons of land degradation and desertification in arid and semi-arid regions. Change detection of salt-affected soils, helps find salt distribution and salinization trends. Present study was arranged for monitoring soil salinity status of agricultural lands located on southeastern part of Bakhtegan Lake in Fars province, Iran using remote sensing techniques in last two decades.Materials and Methods: To fulfill the goal, electrical conductivity data from technical reports in years 1995 and 2007 was obtained and soil sampling was done on 2014. Composite and randomly 0-30 cm soil samples were collected. Electrical conductivity of 1: 2.5 soil: water extracts were measured. Landsat 5 data scanned in 1995 and 2007 and Landsat 8 data scanned in 2014 were used. Different indices and false color composite images were calculated with ILWIS 3.3 software. For year 2014, principal component analysis was done, too. Before correlation and regression analysis, digital number of satellite bands transformed to atmospheric reflectance.80 percent of data was used for classification of imagery data and 20 percent was used for validation the images for all procedures. Salinity maps was obtained, compared and the best model was chosen.Results: Results showed that the minimum Mahalanobis distance method (with overall accuracy of 62.5%) and maximum likelihood method (with overall accuracy of 44.8%) were the best approaches for mapping soil salinity for years 1995 and 2014, respectively, while for the year 2007, the linear regression model (with overall accuracy of 62.5%) increased the accuracy of image classification compared to other methods. Statistical description of soil EC showed that in 1995 more than 50 percent of studied area has Electrical Conductivity less than 2 dSm-1, while in 2014 more than 50 percent of the soils have EC more than 4 dSm-1. Results also showed that during 20 years, saline soils extended from soils around lake and center part of studied region to the Neyriz city.Conclusion: The present study showed that, during 20 years, the area of soils with salinity less than 4 dsm-1 reduced and the area of saline soils increased and salinity expansion was from Bakhtaran lake toward Neyriz city. According to soil salinization trend in studied site, it seems, on the case of continuation of the present land management in studied area, in a short time, the existing orchards would be out of economic cycle. Therefore, to prevent the soil salinization and the loss of farm and orchards in the region, serious efforts of authorities are required

Background and Objectives: Phytoremediation is a biological method by which plants are used to remove environmental pollution caused by toxic elements such as accumulation of cadmium, copper, lead, chromium, etc. from soil. Plants with high capability in the uptake of heavy elements and pollutants in this method are identified and introduced. Identification of nonedible plants or their organs is of higher importance in phytoremediation. Symbiosis of the mycorrhizal fungi (AMF) helps the plant to increase uptake and translocation of low mobility nutrients and also micronutrients. The aim of the present study was to investigate the capability of the marigold in uptake and transfer of cadmium and consequently the phytoremediation of the plant and the effect of symbiosis of mycorrhiza in uptake and refinement of cadmium.Materials and Methods: In this research, arbuscular mycorrhizal inoculant was produced through the isolation of fungi from the roots of marigold and its inoculation with clover and sorghum under greenhouse conditions. Moreover, the symbiotic effect of arbuscular mycorrhizal fungi on the concentration and transfer of cadmium from the roots to the shoots in Marigold was studied under greenhouse conditions. The experiment was conducted using a factorial design based on randomized complete blocks with five levels of Cd (0, 100, 200, 400, 800 mg kg-1 soil), using the soluble form of CdCl2.H2O and two levels of mycorrhizal inoculation (non- inoculated and inoculated) with four replications.Results: Greenhouse test results showed concentrations of cadmium in shoots ranges between 3.91 to 94.9 and in roots between 4.23 and 151 mg.kg-1, which causes toxicity in the plant, with more severe symptoms of toxicity in non-mycorrhizal plants. Also the effect of mycorrhiza and cadmium pollution on growth factors and uptake of cadmium in the root and phosphorous uptake in the root and shoot was statistically significant and mycorrhizal symbiosis caused higher concentration of cadmium in root and relative decrease in its transfer to shoot. On the other hand, the mutual effects of mycorrhizal fungus and cadmium in all the measured traits (except for chlorophyll) were statistically significant.Conclusion: In general, the results of the present study showed that inoculation of the marigold with mycorrhiza results in higher transfer of elements such as phosphorous to the shoot of the plant and caused higher concentration of cadmium in the root of the plant. Considerable increase of chlorophyll and graoth levels was other effects of mycorrhiza on marigold in the polluted conditions.

Background and Objectives: The mobility, bioavailability and environmental fate of heavy metal ions in soil are controlled by sorption onto soil minerals and solid organic matter. The sorption is strongly affected by the presence of various low-molecular-weight organic acids.The main objective of this study was to investigate the effects of oxalic acid on sorption of Cd on clay fraction of a soil.Materials and Methods: The sorption of Cd on clay was studied as a function of pH and time of equilibrium (Cd concentration: 0.045 mM) in the range of 6-9.5 and as a function of metal concentration (Cd concentration in the range of 0.013-0.089 mM) in the absence and presence of oxalic acid with a fixed concentration of 500 mM at room temperature (23±2oC). The amounts of Cd sorbed on the adsorbent were calculated from the difference between the metal concentration in the blank and equilibrium concentration of Cd in the solutions.Results: The results of pH-dependent experiments showed that the oxalic acid decreased sorption of Cd onto the sorbent at all solution pHs. Experimental and modeling data from our kinetic reveal that the pseudo-second-order kinetic model gave the best fit. The Langmuir sorption model describes the interaction between Cd and the clay materials better than the Freundlich model. The value of Langmuir (KL) bonding constant was greater in suspensions without oxalic acid (26.6 Lg-1) as compared to suspensions containing this ligand (15.2 Lg-1).Also, the value of Freundlich (KF) bonding constants was greater in suspensions without oxalic acid (1.2 Lg-1) as compared to suspensions containing this ligand (1.8 Lg-1). These values are indication of low tendency of Cd for sorption on the clay surfaces in the presence of oxalic acid.In order to interpret the effect of oxalate on the sorption behavior of Cd onto the sorbent, knowledge of Cd speciation is essential. Species activities were estimated using the PHREEQC code. In the absence of oxalate, the predominant Cd (II) species is Cd2+over the pH range 3.0-9.0. In the presence of oxalate, Cd2+and Cd-Oxalate species were the major solution Cd (II) species at pH≤10. The formation of soluble complex of Cd-oxalate may be responsible for the inhibition of Cd sorption by the sorbent.Conclusion: In general, our results demonstrate that the oxalate could have negative effects on Cd sorption to clay fraction of soils. Thus, it may play an important role in Cd availability and transport in soil.

Background and Objectives: Soil moisture retention curve is the most important hydraulic function for modeling water flow and solute transport in porous media. Although the hydraulic properties are measured through the direct methods, they are time consuming, difficult and expensive. In last decades, considerable attention has been focused on the development of relationships between the soil water content and the matric potential using fractal geometry models. Fractal models based on mathematical and physical concepts described the geometry of solid porous media. Applications of fractal geometry has provided a useful tool to bridge the gap between the use of empirical models and physical interpretation of their parameters. Based on the fractal scaling of soil structure, different soil moisture retention curve models have been developed. There are also models based on the fractal scaling of particle size distribution or the pore phase of soils. To apply the models, one needs to determine the fractal dimensions. This research was performed to estimate soil hydraulic characteristics using fractal dimension of solid particles in 40 soil samples.Materials and Methods: 40 soil samples with various physical and chemical properties were collected from 40 km of southern Mashhad (Iran) to estimate soil hydraulic characteristics using fractal dimension of solid particles. Soil texture, bulk density and soil moisture at 9 pressure heads 0, 10, 30, 50, 100, 300, 500, 1000 and 1500 kPa were measured and used for determining the parameters of Van Genuchten equation (m and α) in RETC software. Also fractal dimension of solid particles was determined based on clay percentage and used for estimating the moisture contents in Brooks and Corey and Van Genuchten equations.Results: The results showed that correlation coefficient (r) values between measured and estimated soil moisture contents were slightly high (>0.86) in all soil texture classes, i.e. silty clay, loam and sandy loam and the precision of models in estimating soil moisture contents for silty loam class was higher than other classes. Also, using of fractal dimension for estimating the α parameter of Van Genuchten equation had the high precision (r>0.99 and RMSE<0.02) in all 3 soil textures. The precision of estimated m parametre in Van Genuchten equation by using of fractal dimension in sandy loam class was low (r=0.49; RMSE=0.066), but in loam (r=0.49; RMSE=0.06) and specially in silty clay (r=0.88; RMSE=0065) soil texture class was high.Conclusion: In general, the results of this research showed that using fractal dimension for estimation of the hydraulic characteristics has a high precision in moderate classes and as well as fine soil texturse is high and its efficiency is low in coarse textures.

Background and Objectives: In recent decades, efforts to increase the production per area unit, unbalanced and high consumption of chemical fertilizers are consequences of environmental degradation. Using bio-fertilizers without worrying about environmental negative effects improve the soil physical, chemical and biological conditions by supplying a part of the plant requirement to nutrients. Azotobacter is one of the soil microorganisms with the ability of crop growth promoting. The bacterium affect the plant growth parameters directly and indirectly.This study aimed to collect different strains of Azotobacter in Golestan province, study its growth promoting properties and identify superior strains.Materials and Methods: The growth stimulating properties were measured including biological fixation of molecular nitrogen by use of acetylene reduction method, the quantitative solubility of phosphorus on the Sperber medium by colorimetric method by spectrophotometer, the quantitative solubility of mineral potassium on the Alexandrov medium by flame photometer, producing the auxin hormone in the LB-tryptophan medium by colorimetric method by spectrophotometer, ability of semi-quantitative producing siderophore on the CASAgar medium and ability of producing hydrogen cyanide on the TSA medium. The obtained data from each section were analyzed by SAS software using a completely randomized design and mean comparisons were performed using LSD (P<0.05).Results: Forthy-three Azotobacter strains were isolated from soil of Golestan province. The results showed that the highest biological fixation of molecular nitrogen belonged to isolate number 3 equals 276 nmol per hour in the tube, the highest power of quantitative solubility of phosphorus to isolate number 25 equals 232 milligrams per liter, the maximum power of quantitative solubility of mineral potassium to isolate number 23 equals 47 milligrams per liter, the highest power of producing the auxin hormone to isolate number 37 equals 98 milligrams per liter and the maximum ratio of halo diameter to colony about measuring ability of half quantitative producing siderophore belonged to isolates number 4, 9, 16, 18, 31, 37, 38, 40, 41 and 43. The ability of producing hydrogen cyanide was also measured and among all isolates only 4 isolates had this ability and the highest production of hydrogen cyanide belonged to isolate number 43.Conclusion: The results of this study showed the Azotobacter strains isolated from soil of Golestan province have different capabilities in terms of growth stimulating properties and the highest amounts of nitrogen biological fixation, phosphate and potassium dissolution, capable of producing siderophore and auxin were obtained in different isolates. According to the obtained results in different strains of Azotobacter, it seems that some isolates have the potential to be used as plant growth stimulant.

Background and Objectives: Soil maps are the major sources for lands management, natural resources and environmental aspects. Soil salinity is one of the most important factor of limiting product and soil clay also has important effects on soil fertility in Zahak city in Sistan plain.Accurate maps of soil salinity status and clay content could highly help to manage the proper of lands in this area. There are different techniques for prediction of soil characteristics in not sampled areas such as geostatistics and artificial neural networks (ANN) which were used in this study.Materials and Methods: This investigation were done to compare geostatistical and artificial neural networks (ANN) methods in predicting soil salinity and clay content in Zahak city in Sistan plain.121 soil samples were taken from the depth of 0-30 cm within the grid of 750×750 m and soil EC and clay percentage were determined.105 samples were used for training and 16 samples were used for validation in both models. The different models were fitted for each technique and the best models were selected and independent validation was used to determine accuracy of two techniques.Results: Results showed that soil was affected by salinity in study area. ANN with R2=0.59 and RMSE=10.2 comparing to geostatistics with R2=0.53 and RMSE=12.3 had more accuracy in soil salinity prediction. Also in predicting soil clay content, ANN estimated better compared to geostatistics with R2=0.67 and RMSE=6.18 against R2=0.62 and RMSE=8.2.Conclusion: The accuracy of neural network method to estimate the soil salinity and clay content was slightly higher than geostatistical method. In both techniques the accuracy of estimation for soil salinity was lower than clay content that can be related to management effect on soil salinity in study area. Irrigation and agricultural activities caused leaching salts and reducing soil salinity.