نشریه آب و خاک
سال سی و سوم شماره 4 (پیاپی 66، مهر و آبان 1398)

During the last decades, arid and semi-arid regions has faced a severe problem of depletion of groundwater resources due to the over-exploitation of the aquifer. Moreover, groundwater and surface water are not isolated components of the hydrologic system, but instead interact in a variety of aspects in which development of one commonly affects the other. Additionally, the interaction is often complicated by agricultural activities including surface water diversion, groundwater pumping and irrigation. This study presents an integrated SWAT-MODFLOW model that couples land surface hydrology and groundwater hydrology to determine spatial groundwater percolation patterns considering allowable groundwater pumping rates for the Neishaboor watershed, Iran. Within the integrated model, the pumped groundwater is applied as irrigation to the cultivated fields within the SWAT model, with deep percolation from the soil profile bottom applied to the MODFLOW model as recharge. The model is tested against observed stream flow and water table elevation, with model output then used to assess and quantify spatial-temporal patterns of groundwater recharge to the aquifer.

The recently developed SWAT-MODFLOW modeling code simulates spatially-distributed hydrologic processes in the coupled land surface / aquifer system, with SWAT simulating land surface, soil zone, and stream flow routing processes and MODFLOW simulating groundwater flow and groundwater/surface water interaction processes. Modifications which is done to the modeling code includes: 1) Linking pumping from MODFLOW cells to SWAT HRUs for groundwater irrigation and 2) Imposing shallow water table percolation and lateral flow conditions for SWAT HRUs when the MODFLOW-simulated water table is within the soil profile of the HRU. The integrated SWAT-MODFLOW framework is tested in the Neishaboor watershed (9157 km2) for the 1998 to 2011 time period. Climate of the region is classified as semi-arid, with an average annual precipitation of 265 mm that varies considerably from one year to another. The mean annual temperatures changes from 13°C in the mountainous area to 13.8°C in the plain area and the annual potential evapotranspiration is about 2,335 mm. The main crops that are grown in the watershed is irrigated and rain fed wheat during fall and winter and corn silage during summer. Regarding previous studies, about 93.5% of the groundwater withdrawals in the Neishaboor watershed are consumed in agriculture, mostly for irrigation. Therefore, irrigation practices play a crucial role in the water resources balance in the study area. Within the integrated model, the pumped groundwater is applied as irrigation to the cultivated fields within the SWAT model, with deep percolation from the soil profile bottom applied to the MODFLOW model as recharge. The SWAT model was calibrated and tested in SWAT-CUP for the 2001-2009 and 2010-2011 periods, against stream flow and developed model was calibrated manually against groundwater level data.

Annual average recharge, calculated from the daily recharge values pass from SWAT to MODFLOW, demonstrating higher recharge rates in the alluvial fans and upland plain. Observed and simulated stream discharge in four hydrometric stations demonstrate good similarity results with the observed hydrograph. The NS values for monthly discharge rates are considered acceptable, however, the field-estimated stream flow estimates contain a high degree of uncertainty. Simulated cell-wise groundwater hydraulic head at the end of the simulation is compared with observation values with the highest water table elevation occurring in the north east and low water table elevation occurring in the outlet. Comparing observed and simulated average groundwater levels at the 48 monitoring wells, the deviation from the 45-degree line is less than 2.5 m for over 73% of the circles. The manual calibrated model can capture the main temporal trend. Overall, the model well captures the long-term characteristics of the regional groundwater level.

In this study, a new coupled model, referred to as SWAT-MODFLOW was used to model a dry and semi-arid region with a complicated irrigation system with groundwater pumping. A comprehensive model, will enable accurate simulations of stream flow and water table fluctuations in watersheds and aquifers respectably. In short, surface water infiltration is passed from SWAT to MODFLOW based on the contributing areas of the HRUs to the groundwater grid. Pumping agriculture water is then calculated and passed back to SWAT. The need for such a model is highlighted by the Neishaboor basin, where the agriculture is completely based on groundwater pumping. The case study in the Neishaboor basin demonstrated the applicability of the model for large, dry basins. The model will be used to determine best management practices for groundwater pumping in the region.

Subsurface drip irrigation is one of the sub-surface irrigation methods which, despite its high costs, has become increasingly important today. The water distribution pattern is not visible in this system. However, a survey on water distribution model allows it to achieve the expected pattern with the design and operation management predicted. However, the mismatch of water distribution with a subsurface drip irrigation system may be due to many factors such as pressure changes, changes in emitter production, emission sensitivity to clogging, temperature effects and others cases are relevant, but hydraulic properties are the most important. Evaluation of a drip irrigation system under field conditions is important in order to ensure uniform distribution of droplets and to prevent them from clogging and uniformity of growth in the field.  It can also be effective in optimizing water use.

A study was conducted to evaluate the performance of the subsurface drip irrigation and its effect on the growth parameters of olive trees in Isfahan province during 2010-2013. Therefore a manifold system was randomly selected from the irrigation system and four emitter laterals were located along it; one near the inlet, two near the third points, three near the two- thirds points and the fourth near the outer end. Every year, the selected lateral pipes were uncovered and the water flow rates of all the emitters (108 emitters) were measured to calculate average emitter discharge (qavg), Christiansen uniformity coefficient (CU), emission uniformity (EU), manufacturer’s variation coefficient (CV). To calculate the volume of water consumed, potential evapotranspiration (ETo) was determined using daily meteorological data and by the FAO Penman-Monteith method. Then, using olive crop coefficient (Kc) at different growth seasons for Isfahan region, the amount of irrigation water was calculated based on plant water requirement. To measure the performance of garden trees, In addition to 16 trees mentioned above, 32 other trees were selected from the other two semi-main tubes and their yield was measured (48 trees in total). Soil sampling was carried out to study the moisture distribution in the irrigation system at three points, beginning, middle and end of a sub-tube, 36 hours after irrigation, and the samples were transferred to the laboratory to calculate soil moisture content.The results of emitter flow rate measurements indicated that approximately 6 to 10% of the emitters in every lateral were clogged. The reason for this was the rooting of the mulberry trees and rose shrubs, which were planted sporadically among the olive trees. Hence, the foregoing indices were calculated for two conditions; with and without the clogged emitters.

Considering the clogged emitters, the average values of three years of Qavg, CU, EU, and CV indices were 3.8 Lit/ h, 78, 72 and 16.4 % respectively, and in the case of clogged emitters were equal to 4 Lit/ h, 82.5, 75.5 and 15% respectively, and according to ASAE classification, the latter measurements (i.e. excluding the clogged emitters) were evaluated as “acceptable. The moisture distribution profiles indicate that the soil moisture has lasted to a depth of approximately 90 cm, and a higher accumulation of moisture was observed  at a lower depth due to the lighter soil texture in the upper layer (up to a depth of 60 cm) compared to the lower layer (8% clay versus 21% clay). Also changes in moisture to a distance of about 70 cm from the lateral in different depths is almost the same (the lines with the same moisture are parallel to each other), but from this point on, moisture decreases. The effect of moisture radius was observed to a distance of 60 to 70 cm of the emitter. The results related to growth parameters indicated that in contrast to the data of the first year, the average height, trunk diameter, canopy perimeter and area for the third year were 34, 57, 24.5, and 54% larger, respectively. In the present study, the percentage of increase in height and diameter of the tree in the seventh year of growth was 17% and 22%, respectively.

It is concluded that the olive trees have shown an increasing trend in vegetative growth under the subsurface drip irrigation system. The average efficiency of olive water consumption during the three years of the experiment was estimated at 0.4 kg/m3. Given that the trees were young this amount can increase under good management conditions in the coming years. The evaluation indicators showed that the observed defects in the design resulted from the three main factors of the design, implementation and incorrect use of the system.

The average of irrigation efficiency is less than the global average due to improper irrigation systems and traditional water management practices in the field. The use of modern irrigation systems is one of the most important ways to cope with the water shortage crisis in Iran. However, it is necessary to evaluate the effective factors on performance of irrigation system. In present study, a zoning map of suitable land for implementation of sprinkle irrigation system was prepared using AHP method with considering the criteria such as chemical characteristics of water, soil properties, topography, climate, social and economic factors in the Zanjan plain. 

The present study was carried out using collected data from Zanjan plain that located in northwest of Iran and east of Ghezel Ozan River. The total study area is about 4705 km2 and the average rainfall and temperature in region are 259 mm and 10.9 °C, respectively. The first step in the AHP method is to create a hierarchical structure. For this purpose, each of the criteria was rated 1 to 9 based on paired comparisons done by experts and then classification maps were prepared for each of them. In order to provide zoning maps for water and soil factors, data of more than 2000 wells and 111 soil samples were collected, respectively. In addition, data of 13 Meteorological stations were used to prepare zoning maps of climatic factors such as wind speed and temperature. In this research, a topographic map with a scale of 1/25000 was used to investigate the ground slope effect. More than 60 interview forms were completed to produce maps related to socio-economic factors. Zoning maps were prepared using the Kriging interpolation method in ArcGIS software. Finally, the weight of each criteria was calculated according to the scores that obtained in the previous stage and then land classification map was produced by applying the obtained weights on each criteria. In order to evaluate the situation of sprinkle irrigation projects, location of 52 farms equipped with sprinkle irrigation system obtained from the agricultural organization of Zanjan province.  

Regarding the quality of water resources, 40.3% and 21.0% of area were classified in most suitable and suitable classes, respectively and about 10.4% was evaluated in the inappropriate class in order to implementation of sprinkler irrigation. In terms of the soil physical and chemical properties, about 38.4% of plain were classified as "most suitable", 22.8% as "suitable" and 24.7% as "inappropriate" class. In relation to topographic criteria, it can be stated that about 85% of area are in good condition, so that the ground slope in most of the lands is less than 10%. Based on climate criteria and specifically wind speed factor, about 61% of the plain was classified as "good" and "very good", while about 39% was in medium and low class. In terms of social and economic criteria, most of area were found to have a good rating, so there is no particular limitation in this regard. The results of the paired comparisons between criteria showed that, social and climatic criteria have the lowest and highest weight, respectively. The value of the inconsistency rate was calculated about 0.07, which indicated the acceptability of the gained weights. An examination of land feasibility map showed, about 33.4% of the region is suitable for implementing sprinkle irrigation system. About 29.5% and 25.8% were evaluated without limitation and low limitation, respectively. Also, about 10.3% was not recommended for use of sprinkle irrigation. The assessment of the location of implemented projects showed that 44.2% of the projects were in suitable or perfectly suitable classes of land. The rest of the projects (55.8%) were implemented in medium or unsuitable classes.

The results obtained from the AHP method showed that wind speed factor has the most weight and importance in selecting sprinkle irrigation system. Generally, in most farms of the region, there is no significant limitation on the implementation of sprinkler irrigation system. Due to low water quality and high wind speed in a small part of the study area that located in northern and eastern, the use of these systems is not recommended. The results showed that some of the sprinkle irrigation projects have been implemented in lands with low-class and it is essential to improve or change these systems.

Crude oil is one of the most important sources of energy and its large scale production, transmission, consumption and disposal, making it one of the most important and common types of environmental pollution worldwide. Oil extraction and various oil products have led to spread of pollution in the soils around oil extraction and refining sites. During the production and transportation of crude oil, unsuitable operation and leakage may result in contamination of soil with petroleum hydrocarbons. Great concern in this case is the environmental risks of these pollutants. During the past decades, bioremediation of petroleum contaminated soil has been a hot issue in environmental research, and many bioremediation strategies have been developed and improved to clean up petroleum polluted soil. The aim of this study was to compare the effects of co-using of different bioremediation strategies on remediation of crude oil contaminated soil.

In order to investigate the effects of co-using phytoremediation and bioremediation in a crude oil contaminated soil, a factorial experiment in completely randomized design with three replications was conducted. The factors were three levels of crude oil contamination (0 wt% (C0), 2 wt% (C1) and 4 wt% (C2() and four treatments of remediation (Grass (B1), Alfalfa (B2), Grass + Pseudomonas Putida+ Phanerochaete Chrysosporium (B3), Alfalfa + Pseudomonas Putida+ Phanerochaete Chrysosporium (B4), control (B0)). For amendment of contaminated soil, soil samples were artificially contaminated with crude oil (from Tabriz Oil Refinery) and blended to soil (10% total quantity of soil spiked) then spiked soils were progressively mixed with unpolluted soil and homogenized. After preparation of the crude oil-spiked soil microbial inoculation were done and then the samples were packed into soil columns and then plants cultivation was done in soil columns (P.V.C pipes). At the end of growth period, some parameters were measured including residual Total Petroleum Hydrocarbons (TPHs) concentration, microbial basal respiration and dry weight of root and shoot. 

The results showed that TPHs concentration in C1 crude oil level by B3 and B4 remediation treatments decreased by 59% and 57%, respectively, and in C2 level B3 and B4 remediation treatments decreased TPHs content by 41% and 39%, respectively. B3 remediation treatment had the highest shoot and root dry weight and the lowest root and shoot dry weight observed from B2 remediation treatment. Shoot and root dry weight decreased with increasing crude oil contamination levels. The highest basal respiration rate was observed in B3 and B4 remediation treatments. In all of crude oil levels, there was not significant difference between B1 and B2 remediation treatments and control (B0) in basal respiration rate. In the highest crude oil contamination level (C2) the amount of carbon produced as CO2 increased because this level has higher concentration of oil pollutants and therefore has more required substrate for the activity of microorganisms, and consequently more microbial activities increased CO2 production. Compared to the control, the levels of crude oil contamination (C1 and C2) decreased dry weight of root by 46% and 61%, respectively and dry weight of shoot by 53% and 63%, respectively. Considering that the high concentrations of oil contaminants in the soil can lead to toxicity for plants and microorganisms and also hydrophilic properties of these compounds can decrease the availability of moisture and nutrients for plants root, therefore the growth of root decreased in oil contaminated soil. In lower level of crude contamination (C1), remediation treatments have more effective role in refining crude oil. This results from more plant growth and then more plant roots which increase the bioavailability of hydrocarbons by reducing the volume of soil micro pores. Also plants root release organic compounds which would increase the population and activity of soil microbes and these cause to increase of oil compounds degradation and elimination.

Experimental results showed that remediation treatments which contained bacteria and fungi with plants caused to more oil compounds elimination, microbial basal respiration and dry weight of root and shoot. Therefore, it can be found the importance of the presence of microorganisms and the microbial activity with plants in order to degrade and remove the soil oil compounds.
Keywords: Bioremediation, Oil pollution, Residual oil compounds, Microbial basal respiration

Application of organic fertilizers such as vermicompost to agricultural calcareous soils with low organic matter content is a way to add nutrients to these soils. Different organic fertilizers have different effects on soil nutrient availability. Moreover, the study of nutrients distribution in the soil allows us to investigate their mobility and bioavailability. Zinc (Zn) deficiency is an important problem in many calcareous soils due to its effect on increasing the yield of agricultural products. Organic fertilizers can improve availability of Zn by impact on its fractionation. On the other hand, their interaction with chemical fertilizers requires careful consideration of availability and fractionation of Zn in soils treated with organic and chemical fertilizers. The aim of this research was to investigate the interaction effect of zinc sulphate, and vermicompost on availability and fractions of Zn in a calcareous clay soil.

This study was performed as a completely randomized factorial design including two levels of vermicompost (0 and 1% w/w) and three levels of Zn (0, 2, and 5 mg kg-1 as ZnSO4) with three replications. All treated soils were incubated for 120 days at 22 ± 1 0C and constant moisture (17% w/w). Zinc availability (DTPA-TEA) and other fractions (BCR method) were determined at the beginning of experiment, 60 days, and 120 days after incubation. The soil samples were sequentially extracted using an operationally defined sequential fractionation procedure, based on that employed by BCR in which increasingly strong extractants were used to release Zn associated with different soil fractions. Four Zn -fractions were extracted in the following sequence: Step 1: soluble, exchangeable, and associated with carbonates fraction (a 40 ml of 0.1 M CH3COOH for 16 h at room temperature), Step 2: iron-manganese oxides-associated fraction (40 ml of 1 M NH2OH.HCl in 1.5 M HNO3 for 16 h at 22 0C), Step 3: organic matter-associated fraction (50 ml of 1 M CH3COONH4 in 1.5M HNO3 for 16 h at 85 0C) and Finally step 4: residual fraction was determined using 4 M HNO3 (a 12.5 ml volume of 4 M HNO3, for 16 h at 80 0C). Concentrations of Zn in all extractants were determined by Atomic absorption spectroscopy..

The results of this study showed that the mean of Zn extracted by DTPA-TEA after vermicompost application increased significantly (P<0.05). The interaction between vermicompost and time on Zn extracted by DTPA-TEA was not significant (P>0.05). Zinc extracted by DTPA-TEA decreased with increasing incubation time. All forms of Zn increased by vermicompost application in soil samples treated with ZnSO4. Soluble, exchangeable, and bound to carbonates Zn and Zn associated to Fe-Mn oxides fractions (except vermicompost with 5 mg kg-1 Zn at 60 days after incubation) increased with increasing incubation time. Zinc associated to organic matter increased 60 days after incubation compared to the beginning of the experiment. However, difference between Zn associated to organic matter at 120 days after incubation and beginning of the experiment was not significant (except vermicompost with 5 mg kg-1 Zn at 60 days after incubation). The results of this study showed that residual Zn decreased with increasing incubation time. Results of this study demonstrated that the fractions of Zn in the soil samples treated with ZnSO4 were modified after vermicompost application and its availability increased. Therefore, the application of chemical fertilizers with organic fertilizers leads to increase Zn in the soil. The results of correlation study showed that the relation between available Zn and Zn associated to Fe-Mn oxides at 1 h (r=0.77 p<0.05), 60 days after incubation (r=0.95 p<0.05), and 120 days after incubation (r=0.95, p<0.05) was significant. There was a significant correlation between available Zn and Zn in forms of solution, exchangeable and associated with carbonates, associated with Fe-Mn oxides, and associated with organic matter, which indicate the effective role of these fractions in supplying the required Zn to plant.

Vermicompost application in calcareous soils increased available Zn and the effect of vermicompost was not dependent on time. Over time, there was a decrease in available Zn in the presence of chemical fertilizer. Vermicompost application in calcareous soils increased all Zn fractions. According to these results, the Zn fractions in the soil treated with zinc sulfate had been changed and its availability increased during incubation time. The results of this study demonstrated that the fractions of Zn in the soils treated with ZnSO4 and vermicompost were modified and its availability increased. Therefore, the application of chemical fertilizers with organic fertilizers can increase Zn in calcareous clay soils.

Environmental contamination by crude oil and its various processing products is becoming a common phenomenon which severely damages soil and groundwater resources. Among the constituents of oil waste, polycyclic aromatic hydrocarbons (PAHs) are of environmental concern because of their toxic, mutagenic and/or carcinogenic effects. Bioremediation involves the use of living microorganisms, bacteria or fungi, for detoxification of soil and water organic pollutants by biodegradation, biotransformation, and/or mineralization. Collaboration between different microbes under co-culture conditions such as co-metabolism or antagonism makes the system to perform better than a single microorganism. Total petroleum degradation is a result of a microbial consortium action, which is composed of different species with specific biochemical roles. On the other hand, the majority of components of petroleum products has low solubility in water and tends to bind to soil particles reducing their availability to  microorganisms for degradation. This has been well described as a major limitation to the bioremediation of hydrocarbon contamination. The surfactants can be employed to enhance hydrocarbon biodegradation by mobilization, solubilization, or emulsification. Some microorganisms synthesize a wide range of surface-active compounds, generally called biosurfactants, which increases the bioavailability of these compounds. The application of these microbial surfactants in the remediation of hydrocarbons aims to increase their bioavailability or mobilize and remove the contaminants by pseudo-solubilization and emulsification in a treatment process. This work aimed to investigate the impact of the biosurfactant producing consortium on the benzo(a)pyrene biodegradation.

Four gasoline contaminated soils were enriched in Bushnell-Hass mineral medium with Benzo(a)pyrene (200 mg/l) for three months at 30°C. After this time, to obtain Benzo(a)pyrene-degrading isolates, 0.1 ml of soil suspensions were plated on BH agar plates containing pollutant. Three colonies with different morphological distinct properties were purified on LB agar plates. The screening of the most potent surfactant strain was assayed quantitatively using measurement of surface tension by the Du Nouy ring method. For increasing the production of biosurfactant, medium conditions including pH (6, 7, 8), temperature (25, 30, 35) and carbon source (glucose, sucrose and ribose) were optimized with fractional factorial based on Taguchi. The capability of the isolates and consortium in hydrocarbon biodegradation was investigated in liquid medium of Bushnell-Hass with 150 ppm of Benzo(a)pyrene, during 14 days. Treatments included inoculation of isolates AP3 and BM1 and their consortium in presence and absence of extracted isolates biosurfactants and control (no isolate and biosurfactant). Based on the results of Benzo(a)pyrene degradation in the liquid medium, AP3 isolate, consortium and biosurfactant extracted from AP3 were selected for soil experiment. Four sets of biodegradation experiments were carried out with soil contaminated by 150 ppm of benzo(a)pyrene for 45 days, as follows: set 1: soil + AP3 isolate; set 2: soil + consortium; set 3: soil + consortium + AP3 biosurfactant and set 4: blank (soil). The residual concentrations of contaminant were extracted on days 15, 30 and 45 by dichloromethane solvent and analyzed using GC-FID.

The results revealed that strains AP3 and BM1 showed a significant potential to produce surface-active agents in the presence of Benzo(a)pyrene as substrate, reducing the surface tension to 43 and 46 mN/m, respectively. Taguchi experimental design method was applied in order to optimize the biosurfactant production by isolates. Results of experiments indicated that the optimum biosurfactant production conditions were found to be temperature of 35º C and  pH of 7, and glucose as water soluble carbon source. The produced biosurfactant reduced surface tension to 31/52 mN/m and 30/81 mN/m for BM1 and AP3, respectively. Biodegradation experiments of Benzo(a)pyrene in liquid cultures showed that the overall biodegradation efficiency of the individual isolates after 14 days was lower than consortium. Bacterial consortium enhanced degradation of contaminant to 87.3% (with addition of biosurfactant) compared to 27.6% of removal in presence of BM1 isolate. However, there was no statistically significant change in the degradation rates of contaminant in consortium with addition of AP3 and BM1 surfactant and surfactant free (87.3, 85.6 and 86.8%, respectively). The degradation of Benzo(a)pyrene was significantly enhanced in presence of AP3 biosurfactant at individual BM1 treatments (28.3 and 44.5 to 74.8%). Maximum degradation of Benzo(a)pyrene in contaminated soil was found (100%) in set 3: soil + consortium + AP3 biosurfactant. Based on GC-MS analyses, it degraded around 100% of penzo(a)pyrene, used as the sole carbon and energy source, at an initial concentration of 150 mg L-1, after 45 days of incubation, while alone consortium and isolate were able to remove 86% and 68% of hydrocarbon, respectively. Overall, these results provide evidence that consortium and AP3 biosurfactant could be potential candidates for further bioremediation.

The results revealed that the hydrocarbon removal efficiency of the consortium was higher than single species, and the final removal efficiency for the consortium could be reached in a considerably shorter time. The results suggest that biosurfactant-assisted bioremediation may be a promising practical bioremediation strategy for aged PAH-contaminated soils. It is evident from the results that the consortium alone and its producer species are both capable of promoting biodegradation to a large extent.

Zinc (Zn) is an important nutrient element for plants growth, which plays an important role in the metabolism of plant. Zn uptake by plants requires release of Zn adsorbed onto the soil constituents and even Zn containing minerals. The release of Zn from soil surface to the soil solution is an important factor that controls availability of Zn for growing plants. Kinetics of Zn release from soil could indicate ability of soil to Zn supply to plants. The purpose of present study was to investigate the effects of soil depth and canopy of three cultivars of palm including Shahani, Ghasab and Halavani on release kinetics of native Zn by AB-DTPA extractant.

In order to investigate the effects of depth and vegetation on the pattern of Zn release,  54 soil samples were collected from inside and outside canopy of different palm cultivars (Shahani, Halavani and Ghasab), three depths (0-20, 20-40 and 40-60 cm) with three replications. These samples were collected from village of Simakan, located in the city of Jahrom. Extraction was performed after eight shaking times (5, 15, 30, 60, 120, 240, 480, and 1440 min) with ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA). After each shaking time, samples were immediately centrifuged for 15 min, and then filtered through filter paper. The concentration of Zn in solutions were determined using an atomic absorption spectrophotometer (AA-67OG). Seven commonly used kinetics models in nutrient release studies were used to describe Zn release including zero-order, first-order, pseudo-first-order, pseudo-second-order, power function, parabolic diffusion, and simple elovich. Data analysis and drawing of charts were done by SAS software and Excel program, respectively. Relatively high value of coefficient of determination and low value of standard error of estimate were considered as criteria for the best fit.

The results of this study showed that the simplified Elovich, parabolic diffusion and power function equations well described the pattern of Zn release from soil as evidenced by higher coefficient of determination and lower values of the standard error of the estimate. The Zn release pattern in all soil samples consisted of a quick stage from the start of the experiment to 240 minutes and a slower stage at subsequent times. The correlation between the coefficients of the kinetic equations of the power function, simplified Elovich and parabolic diffusion showed that there was higher correlations between the coefficients of the equations obtained from the under canopy in comparison with those of out of canopy. Although soil is a major factor influencing vegetation growth and characteristics, plants could, in turn, also affect different soil properties. In addition, the palm root system and the rhizosphere exhibit a complex diversity, which could regulate the plant homeostasis. The interaction of root-microorganism in the rhizosphere can cause many of the physical, chemical and biological properties of the rhizosphere soil that are different from the bulk soil. Important changes in the soil properties of the rhizosphere environment include soil pH, soil oxidation-reduction reactions, soil moisture, and nutrient availability for microorganisms and plant. Root exudates also contribute to enhance of the availability of elements by reducing the pH of the rhizosphere and creating bioavailable Zn complex. Recent studies have shown that root exudates can act as an influential factor in extracting significant values of plant nutrients from calcareous soils. Our results showed that the amount of accumulated Zn released from the under canopy soils was more than the out of canopy soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar.

Results of present study showed that the values of Zn released from the under canopy soils was higher than interspaces soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar. Such observations clearly indicate that palm trees are able to supply Zn absorption capacity under their own canopy soils. Therefore, it appears that higher rates of Zn release from the under canopy soils in comparison with interspaces could be attributed to higher root exudates which impact soil properties, microorganism activities and lower pH which, in turn, increase the amounts of metals including of Zn release and bioavailability. Further researches on the effect of palm root system on physical and chemical properties of soil, including organic matter, soil pH, which could cause great impacts on the amount of Zn release are highly recommended.

Among growth factors, proper nutrition plays an important role in increasing yield and the quality of wheat grain.  Wheat in most human societies is a strategic product and the main supplier of protein and calories needed by communities. Among growth factors, proper nutrition plays an important role in increasing yield and the quality of wheat grain. Potassium (K) is the most abundant cation in the cytoplasm of the plant and plays an important role in plant physiological functions. Its deficiency reduces the qualitative and quantitative yield of crops. It is an essential component in the basic stages of protein biosynthesis. Its deficiency results in a decrease in wheat protein. The results showed that a small amount of potassium was needed in the establishment and wintering stages of wheat and it was highly required at the later stages of plant growth and the plant requirement reached its maximum in flowering stage. This illustrates the importance of taking potassium partition. Among the low nutrient elements, Zinc (Zn) is the most important element that is clearly deficient in calcareous soils. Zinc is essential for enzymatic activities and increases the protein, carbohydrate and gluten of wheat grains.

In order to investigate the effect of different sources of potassium (K) fertilizers management on some qualitative and quantitative characteristics of wheat, two experiments were conducted in two fields with lower and higher critical level of K (Kava=125 and Kava= 412mg kg-1) in a randomized complete block design with five treatments and four replications in West Azarbayjan province in 2017-18. Treatments were as follows: T1 = control (use of all essential nutrients based on soil test except K-fertilizer) ; T2 = T1 + whole sulfate of potassium (SOP) before planting; T3 = T1 + consumption of 50% K from (SOP) before planting and 50% from muriate of potassium (MOP) in two topdressing; T4 = T1 + consumption of 50% K from SOP before planting and 50% from soluble sulfate of potassium (SSOP) in two topdressing; T5 = T1 + consumption of 50% K from SOP before planting and 50% from SSOP + Zn-EDTA in two topdressing periods during the first stem elongation and wheat heading. Basal elements based on soil analysis results were as follows: at site one, containing 250 kg ha-1 potassium fertilizer, 150 kg ha-1 triple superphosphate and 100 kg ha-1 pre-planting urea fertilizer, and at site two potassium and urea similar to site one and 75 kg ha-1 triple phosphate. Topdressing 120 kg urea ha-1 was used in two stages i.e. the first stem node and the emergence of cluster at both locations. The size of the plots was 4 m2 and the interval was 2 m. Mihan cultivar was planted at a density of 500 seeds m-2 and 180 kg ha-1 using a linear grain harvesting machine. After determination of yield parameters, soil and plant composite samples were prepared and taken to the laboratory. Physical and chemical analysis of soil was performed using conventional methods at the Soil and Water Research Institute. Statistical analysis of data for different traits at two locations was performed using SAS statistical software version 9.1. Mean comparisons were undertaken using Duncan's multiple range test at the 5% level of probability.

The results of this study revealed that in the field (1), K-fertilizers increased grain yield and protein content. In this field, T5 was the best treatment in comparison with the other treatments. Split application of SSOP+Zn-EDTA was the best treatment and increased potassium fertilizer efficiency (KUE). Topdressing of SSOP+Zn-EDTA compared to other K-fertilizers, due to having available K and Zn, increased the kernel, grain yield, grain protein, straw weight and Zn content. While KUE in T2 was 5 kg kg-1, it became 6 kg kg-1 in T3 and T4 , and increased up to 8 kg kg-1 in T5. However, in the field (2) due to its higher content of available K, application of K-fertilizers had no significant effects in all treatments. In the field (1), applying the optimum amount of fertilizer (T3), increased wheat yield by 1300 kg ha-1 compared to the control treatment. However, T5 increased the yield and fertilizer efficiency by 11% and 60%, respectively, even with respect to T3. Therefore, split application of K-fertilizers should be conducted based on the soil analysis result.

Topdressing of soluble sulfate potassium +Zn-EDTA compared to other K-fertilizers, due to having available K, Zn and SO4, increased grain yield, protein, straw weight and Zn content, and fertilizer efficiency.

Among the elements, potassium (K) is the third important macronutrient for plant nutrition that plays a significant role in plant growth and development. The development of intensively managed agriculture has led to the consumption of increasing amounts of K, low K supply has therefore become an important yield-limiting factor in agriculture. However, more than 98% of potassium in the soil exists in the form of silicate minerals such as illite and lattice K in K-feldspars which K cannot be directly absorbed by plants. Potassium and other minerals can be released when these minerals are weathered. Some microorganisms can play a role in releasing K from minerals. They solubilize K-bearing minerals through different mechanisms including chelation, acidolysis, pH reduction, exchange reaction, complexation, biofilm formation and secretion of organic acid and polysaccharides. Since the use of potassium solubilizing microorganisms (KSMs) as K-biofertilizers reduces the agrochemicals application and supports eco-friendly agriculture, so it is imperative to isolate the KSMs and optimize various growth parameters so as to improve their activity.

The present study was an attempt to model and evaluate the effects of pH, incubation time and different amounts of carbon source on K release by Pseudomonas fluorescens using Placket-Burman design and response surface methodology with a central composite design. At the first step, 12 experiments based on Placket-Burman design were carried out to screen and identify the effective carbon source in potassium release. According to the results of the first step, response surface methodology with the central composite design was employed to evaluate and model the effects of the coded independent variables including pH (3-10), incubation time (1-18 days) and carbon source (0.6-12 g L-1) on K release from feldspar and phlogopite. After the completion of each period, samples were centrifuged at 3000 rpm for 10 minutes and filtered using Whatman paper (No. 41). Potassium concentration of samples was measured by flame photometer. Used minerals in the experiment including feldspar and phlogopite were grounded and filtered through a 230 mesh sieve. In order to remove exchangeable K, the samples were saturated by calcium chloride solution (with a ratio of 2:1), after washing with HCl, samples were then dried at 105oC for 48 hours.

Results showed that there was no difference between carbon sources, applied at the first step of the experiment, so each can be employed as alternatives to each other in the culture medium. The central composite design showed R2 of 0.944 and 0.918 with RMSE of 0.82 and 1.47 for predicting K release of feldspar and phlogopite, respectively, indicating high efficiency. Sensitivity analysis of the central composite design revealed that the pH is the most important factor in K release. The highest concentration of the K was observed at the highest levels of pH. Incubation time also had an impact on potassium release. In the early stages of the incubation time, the trend of potassium release was increasing, in middle stages, K amount decreased but it was accelerated over long times of incubation. The maximum potassium release in presence of phlogopite and feldspar was 121.16 and 96/82 mg L-1, respectively, which was observed at pH= 10.36, sucrose amount= 6.5 g L-1 during 10 days. Potassium amount in this treatment hence increased by 31.52% as compared to feldspar. According to central composite design, maximum potassium release of feldspar and phlogopite was obtained at pH= 10.36 and 10.34, sucrose concentrations of 2.26 and 6.92 g L1 at 18 and 2 days, respectively.

Our results showed that pH had a significant impact on K release by Pseudomonas fluorescens using response surface methodology. Overall, increasing incubation time along with high pH leads to the high amounts of K release from minerals. Different minerals released different content of potassium. Application of soil K-bearing minerals in combination with efficient potassium solubilizing bacterial strains as biofertilizers is required to replace chemical fertilizers and reduce the crop cultivation cost. Many bacterial strains have been found to solubilize minerals and improve plant growth under laboratory and greenhouse conditions, but their ability under field conditions remains unexplored. The capability of these bacteria, considering the soil and plant type, and environmental factors, should be thus evaluated under field conditions.