نشریه مهندسی زراعی
سال چهل و یکم شماره 1 (بهار 1397)

Introduction 137Cs is an artificial radionuclide with a half-life of 30.2 years and strong gamma radiation that, due to nuclear explosions in the 1950s, and 1960s entered the earth's surface by the rain. The radionuclide has been widely used for the evaluation rates and patterns of soil erosion and deposition. 137Cs was rapidly adsorbed to fine particles of soil surface horizon and its distribution is basically accompanied by the physical processes of soil, such as erosion and tillage. 137Cs is distributed exponentially as a function of depth to a maximum depth ranging from 5 to 15 cm in the undisturbed soil. The basis of calculating of erosion by 137Cs method is based on comparison between the amount of 137Cs in studied soil and the reference site (local, flat, un-eroded, undisturbed and stable site) and 137Cs loss or gain, relative to the reference inventory, indicates soil erosion and deposition, respectively. So, the reliable and accurate reference estimate of 137Cs is essential. No attempt has been made to explore the variability of 137Cs inventory in the reference sites in Iran. Therefore, This study was conducted to evaluate variability of 137Cs inventory and its relationship with some soil properties at the reference site located in Fereydan district in western of Isfahan province.
Materials and Methods 96 soil samples were collected from 0-15 cm and 15-30 cm depths. Moreover, for evaluation of vertical distribution of 137Cs, two profiles were excavated and 8 soil samples were collected from 0-5, 5-15, 15-25 and 25-35 cm depths. Gamma-ray spectrometry device was used for 137Cs analysis. Magnetic susceptibility values were measured using Bartington susceptimeter at low (0.46 kHz) and high (4.6 kHz) frequencies and magnetic susceptibility dependent was calculated by low and high frequency values. Soil properties including total nitrogen, organic material, cation exchange capacity, calcium carbonate equivalent, EC, pH, texture, gravel and bulk density were determined. Descriptive statistics including mean, minimum, maximum, standard deviation (SD), coefficients of variation (CV), skewness, and kurtosis were calculated by SPSS software, v.16. The distribution of variables was evaluated using the Kolmogorov-Smirnov test. Pearson correlation coefficient and regression analysis were used to examine the relationships between 137Cs and soil properties.
Results and Discussion The coefficient of variation of 137Cs inventory were 15.05 and 14.05% in 0-15 cm and 15-30 cm depth respectively. The result indicated that 137Cs has uniformly distributed in studied reference site. The results of the study showed that OM, OM/Clay, CEC/Clay, EC, Sand, BD, χlf and χhf were correlated with 137Cs. The results of multiple regression analysis indicated that bulk density, clay content and magnetic susceptibility at low frequency explained 43% of total variability of 137Cs in the studied reference site.
Conclusions In the present study, variability of 137cs was investigated in a reference site in Ferydan district in Isfahan Province. The study showed that 137Cs had low variability. Among the soil physical and chemical properties, Soil pH, silt, gravel, nitrogen and calcium carbonate equivalent did not show significant correlation with 137Cs. The highest positive significant correlation was obtained for BD and 137Cs. Also, magnetic susceptibility at low and high frequencies showed significant correlations with 137Cs. In the multiple regression analysis, BD, clay content, and magnetic susceptibility were included in the model for explaining the 137Cs variability. It is suggested that similar study be done in the other reference sites in the western Iran

Introduction Soil quality has been defined as a “The potential of soil to play a positive relationship with the other parts of ecosystem”. Soil biological indicators provide insight into the living component of the soil. Similar to physical and chemical indicators, biological indicators have a relationship to soil functions and can evaluate soil functions to assess soil quality. Between biological indicators, an index that can be measured quickly and easily is more useful to show the changes. In many studies an indicator of microbial respiration, microbial population, nitrogen mineralization and enzymes activity can be used. Special ability is required to measure quickly and show the quality of soil microorganisms and reaction to environmental changes. Soil health is defined by chemical and physical parameters such as soil texture, soil pH, electrical conductivity, etc., that are not quantifiable completely. Therefore, conservation practices planting and forestry may directly or indirectly affect a organism’s activities. The results of land-use systems without consideration of the consequences on soil quality have been environmental degradation. Agricultural management systems have been generally adopted without attending to soil conservation and soil quality, and this therefore causes significant decline in agricultural soil health worldwide. Different methods of soil conservation have been proposed to prevent erosion and improve soil quality destructive phenomena. In Golestan province due to topographical and climatic conditions and less soil sensitivity to erosion, more attention should be given to this issue. But it remains unclear how far this conservation practice can take to prevent damage. This study aimed to investigate the role of conservative practices to improve the soil quality indicators.
Materials and Methods The watershed of Chehelchai is located between North latitudes 36° 59´ and 37° 13´ and Earth longitudes 55° 23´ and 55° 38´. The history of land use in the region shows that more than about 40 years ago, all the study area was covered by forest. Agricultural land use changes occurred on a large scale. With emphasis on conservation operation, parts of the agricultural land were changed to productive gardens, partly forested, partly pasture with native species. Different land uses were selected in loess formations, and slope of 41 %, with life operations was about 6 to 7 years. Protective Operations Garden species, terraces and forestry were selected and quality of soil was compared with agricultural land, pasture and natural forest. In this regard, 10 soil samples were taken. After preparation of the samples, physical, chemical and biological analysis were measured. Additionally, soil properties (pH, Electrical Conductivity, Calcium carbonate, organic matter, texture, bulk density, aggregate stability, microbial respiration, microbial biomass population count of micro- arthropods, biological soil quality) were analyzed. The data were analyzed using software SAS. Ver 9. and the results were compared in a randomized complete block design. Analysis of variance in the form of randomized complete block design was done using the LSD multiple comparison.
Results and Discussion Our results showed that the dominant soil texture class in land uses was silty loam. It seems that soil texture is less affected by the land use changes. The results showed that the changes of forest and pasture to agricultural lands have destroyed the soil quality. Soil quality indicators such as organic matter and aggregate stability have declined by 60 and 70 percent respectively. Like wise, biological indicators such as microbial respiration, microbial biomass carbon and QBS (biological soil quality indicators based on the population of micro- arthropods) and EMI (index dependence of soil to soil organisms) showed a similar trend. In contrast, the Conservation practices improved the indices. Biological indicators in the forestry and gardening showed an increase of 40 percent in EMI Microbial biomass carbon and 80 percent in microbial respiration. Terracing had less improvement than other operations in about 11 to 20 percent in EMI and microbial biomass carbon.
Conclusion Conservation operations had fewer effects on indicators such as aggregate stability and organic matter. Under estimation of effects in certain indicators maybe due to short time of conservation practices. It seems that these operations will show better results in the future

Introduction Tillage is a main operation for seedbed preparation and is one of the major items of energy and cost expenditure in crop production. In the conventional rotary tillers, using the L-shape blades has numerous problems such as severe vibrational problems, weeds wrapping around the blades, and lower performance due to the limited power of such small tillers. Therefore in order to overcome the addressed problems, design, fabrication and evaluation of a new rototiller adapted for small farms and gardens were considered in this research.
Materials and Methods To start the design, the power requirement was estimated using a semi-theoretical model for the given working depth, working width, forward and rotational speed of the machine. Then a suitable engine was chosen based on the estimated power. The estimated power was 3.4 kW (4.5 hp); therefore, according to the available engines in the market for single cylinder gasoline engines, a Kato engine with 5.5 hp power and maximum speed of 3600 rpm was chosen. By reducing the rotational speed of the engine in three stages, rotational speed of the rotor was obtained in the range of 140-260 rpm. To transmit the power from the engine to the rotary axis, first, a pulley and belt mechanism (two V-shaped belt, type B) and then two chain mechanisms (roller chains 40 and 60) were used. Rotary axis with the diameter of 2.5 cm was made from steel E295. The fabricated rototiller has a working width of 60 cm, working depth of 7 cm, rotational speed between 140-260 rpm, forward speed equal to the operator’s translational speed, and maximum power equal to 5.5 hp.
The maximum force exerted on each of the blades was calculated equal to 84.10 kgf (824.73 N) using the theoretical approach proposed by Bernacki (1972). In the next step, numerical simulation of blades, flanges and rotating shaft for stress and strain analysis was performed using the Ansys software.
Farm experiments were carried out as split plots in citrus gardens based on randomized complete block design with three replications. The soil moisture content as the main plot varied in two levels (13.5-21.9 and 21.9-30.3 percent based on dry weight) and the rotational speed of blades as subplots varied in three levels (140-170, 170-200 and 200-230 rpm).
The measured parameters consisted of clod mean weight diameter, soil relent percentage, soil bulk density and specific fuel consumption. To determine the diameter of aggregates, a set of standard sieves with the diameter ranging from 0.5 to 8 mm were used. Then a laboratory shaker was used to sift the samples. Each sample was shaken for 30 sec. To determine the fuel consumption during the experiments, the filled fuel tank method was used. Data analyses including analysis of variance (Anova), mean comparisons and interaction between the parameters were performed using the SPSS 16 software.
Results and Discussion The numerical stress analysis of the flange showed that the maximum van - Mises stress occurred in the position of the blade-flange connections, with a magnitude of 52.98 MPa for the given working conditions, including soil engineering properties, working depth and other important parameters. The experimental results obtained in this study indicated that influence of soil moisture and rotational speed of blades on the clod mean weight diameter, soil relent percentage and specific fuel consumption were significant (P<0.01). The clod mean weight diameter was measured equal to 8 mm at high rotational speed (200-230 rpm) and high soil moisture content (21.9%-30.3%) and equal to 15 mm at low rotational speed (140-170 rpm) and low soil moisture content (13.5%- 21.9%). The maximum soil relent percentage was obtained equal to 97% at high rotational speed (200-230 rpm) and high soil moisture content (21.9%-30.3%).
Regarding the results obtained in this study, the specific fuel consumption increased first in a light slop, then in a steep rise with increasing the blades rotational speed. The reason can be the higher relent percent of the soil at higher rotational speeds and higher moisture contents, albeit at the examined range of 21.9-30.3. The specific fuel consumption was maximum at higher soil moisture content, i.e., 30 %. The results indicated that the blades rotational speed and soil moisture content had no significant effect on the field efficiency of the examined rototiller. Reduction of the rotational speed of the rototiller from high-to-moderate speeds yields decreasing the fuel consumption of 17 liter/ha, which could be significant in a wide scale soil tillage operations. As a general result, reduction of the rotational speed has some considerable advantages such as reducing the power requirements, reducing the blade wearing and maintaining the soil structure.
Conclusion The stress analysis of the fabricated machine together with the experimental and field measurements indicated that the new proposed and fabricated blades were a suitable choice for construction of small rototillers. The fabricated machine with the new blades showed some additional advantages including less specific energy consumption, less weeds wrapping around the blades, and less vibrational problems

Zinc (Zn), an essential micronutrient for both plants and humans, is involved in a number of physiological and biochemical processes. Calcareous soils cover more than 30% of the earth’s land and are characterized by the high pH and low availability of plant nutrients. Zinc (Zn) that is freely available in acid soils is only sparingly available in calcareous soils, due to their poor solubility at high pH. Zinc deficiency in most of the world’s soils has resulted in significant loss of agricultural yields. Information about Zn availability in soils is very important in the view point of Zn nutritional status of plant and human. Several soil physicochemical properties including organic matter, CaCO3, pH, moisture and total Zn concentration affect soil Zn availability to plants. Under Zn deficiency, plants tend to release organic acid in the rhizosphere which in turn increases soil Zn availability. Oxalic acid is the simplest dicarboxylic acid with two pKa values, 1.23 and 4.19 and it occurs in sediments, forest soils, and agricultural soils, especially in the rhizosphere. Oxalic acid is able to chelate with the poorly soluble nutrients in the soil and consequently influence their bioavailability. It is known that Zn availability is controlled by adsorption, release, precipitation and dissolution reactions. Study of kinetic models is a useful method to describe the changes in the nutrient availability with time. A knowledge of desorption kinetics may provide important information concerning the nature of reaction and the rate of Zn supply to plants via soil solution.
Materials and methods Composite samples of the two soils were collected from 0-30 cm depth of agricultural areas in Kerman province, Eastern Iran. The samples were air dried, crushed and passed through a 2mm sieve. Some soil chemical and physical properties of soil sample including Particle size distribution, Electrical conductivity and pH, Organic carbon, carbonate calcium equivalent, cation exchange capacity, available Zn and Total content of Zn were done according to standard procedures. For the kinetic study, soil samples were weighed (1.5g), placed in a 20 mL centrifuge tube and then 15 mL of oxalic acid with two concentrations of 1.1 and 2.2 mµ L-1 was added. The tubes were shaken from 1 to 72h at 25±2°C. Two drops of toluene were added to each tube to inhibit microbial activity. After shaking, the solutions were centrifuged and filtered through Whatman filter paper No. 42. Zinc concentration was determined in the filtrate using a Vario atomic absorption spectrometer. Several kinetic equations including zero-, first-, second- and third order, parabolic diffusion, Power function and simple elovich were also fitted to experimental data.
Results and discussion Zn release by oxalic acid increased with time and the amount of Zn release differed between soils. The difference in the amount of Zn release may be attributed to differences in (i) the total amount of labile Zn which sorbed in the soil; (ii) types, quantities and relative proportions of the soil components by which the Zn is retained and (iii) other soil properties such pH and CEC. The release pattern of Zn included an initial fast reaction followed by a slow reaction that continued up to 72 h. The two phases of Zn release can be due to the heterogeneity of adsorption site with different adsorption affinities. The release kinetic of Zn in soils was poorly described by first- and second-order equations while Time dependent Zn release was best modeled by the simple Elovich, power function and parabolic diffusion equations. Based on the relatively higher values of r2 and the lower values of S.E., the simple Elovich showed the best fitness on the cumulative release of Zn. At each specified time, the lower dose of oxalic acid released Zn from soil more than the higher dose. Organic acids may increase the sorption of metal ions on soil particles through electrostatic interactions, ternary metal–ligand–surface complex formation or surface precipitation. It seems that Zn may interact with oxalic acid where adsorbed to solid phases and resulted in decreased Zn release. The rate parameters derived from the best-fitted model were used to compare Zn release by different concentrations of oxalic acid. The results showed that the rate parameters “ab”, Kp and β decreased with the oxalic acid concentration.
Conclusion From the present study, oxalic acid, especially at the lower rate, can increase Zn release and its bioavailability in calcareous soils.

Introduction Zinc is one of the imperative micronutrients required relatively in small concentrations in tissues for healthy growth and reproduction of plants. Zinc deficiency in plants leads to reduced membrane integrity and synthesis of carbohydrates, auxins, nucleotides, cytochromes, and chlorophyll and develops susceptibility to heat stress. The solubility of Zn is highly dependent upon soil pH and moisture and hence arid and semiarid areas are often zinc-deficient. The use of microorganisms with the aim of improving nutrients availability for plants is an important practice and necessary for agriculture. Zinc-solubilizing microorganisms can solubilize zinc from inorganic and organic pools of total soil zinc and can be utilized to increase zinc availability to plants. Therefore, the present study was carried out to isolate and characterize native zinc-solubilizing bacteria from Zea mays rhizosphere and evaluate their zinc-solubilizing potential and the effect of zinc solubilizing isolate on Zea mays growth.
Materials and Methods In vitro zinc solubilization assay of isolates was done using 0.1% zinc from zinc oxide in both plate and broth assays. Actively growing cultures of each isolates were spot-inoculated (7 µL) onto the agar and plates were incubated at 28°C for 120 h. The clearing zone around colony was recorded. Quantitative study of zinc solubilization was studied in 150 mL conical flasks containing 50 mL of liquid mineral salt medium. The broth was inoculated with 500 µL of overnight grown bacterial inoculum and incubated for 120 h at 160 rpm in an incubator shaker at 28°C. After incubation, the culture broth was centrifuged and the concentration of Zn in the supernatant was estimated in atomic absorption spectrophotometer. Among these isolates, 18 isolates with a solubility index of 1 and higher were selected based on morphological, biochemical and physiological characteristics for further studies. An isolate with more ability to dissolve zinc, phosphorus, potassium and auxin production was selected to investigate the effect of isolate on Zea mays growth. Maize seeds of cultivable variety were surface sterilized with 10% sodium hypochlorite for 10 min and washed several times with sterile distilled water. Seeds were treated with inoculum containing 108 cfu·ml−1 of isolate. A factorial experiment in a completely randomized design with five replications was conducted. The treatments included two levels of bacteria B1 (control), B2 (stenotrophomonas maltophilia) and zinc sulfate fertilizer at three levels of Zn0 (control), Zn20 (20 kg/ha) and Zn40 (40 kg/ha). After 20 days of sowing, plants were removed from the tubes carefully and biometric parameters like, Chlorophyll index, root length, shoot length and dry mass of plants were recorded as the indicative of plant growth.
Results and Discussion A total of 50 bacterial isolates were isolated from corn rhizosphere. Of all, sixteen isolates showed solubilization halo on plate agar medium. Among the cultures, Z1, Z3 and Z16 showed the highest solubilisation zone in ZnO amended medium with maximum solubility index (1.3). Quantitative assay for zinc solubilisation revealed that Z13 was able to dissolve 44.8 ppm from ZnO in liquid medium while solubility index of this isolate was lower than above the mentioned isolates (1). Of all, isolate Z13 with the highest zinc solubilisation by broth assay was characterized and identified as Stenotrophomonas species based on Gram-negative reaction, endospore-forming cells, and other biochemical and physiological properties. This isolate was able to produce auxin and dissolve insoluble phosphorus and potassium from the source tricalcium phosphate and vermiculte, respectively. One of these strains (Z13), Stenotrophomonas, was used as inoculum in corn culture.
Seed bacterization of maize with zinc solubilising Stenotrophomonas enhanced the plant growth significantly after 15 days. Results indicated a significant interaction effect of bacterium and fertilizer on shoot dry weight and chlorophyll content (P<0.01). The maximum spad index and wet weight of aerial part was obtained in the presence of bacterium and without using of zinc sulfate. The main effect of bacterium on wet and dry weight of root and wet weight of aerial part, root length and shoot height was significant (P<0.01).The highest chlorophyll index and aerial part dry weight were related to bacterial treatments, which showed an increase of 34.7% and 87%, respectively, compared to control (without fertilizer and bacteria).
Conclusion PGPR is known as a group of useful rhizospheric bacteria that increase plant growth. Today, the increasing use of PGPRs in agriculture is an alternative to chemical fertilizers to prevent environmental contamination

Shortage of non-saline and high quality irrigation water is a serious problem in agricultural farms which limits crop productions. Proper nutrient management is one of the key solutions to decreasing the adverse effects of salinity. Zinc is an essential trace element that can alleviate the negative effects of toxic ions on plant growth under the saline environments. Therefore, in this study, the effect of zinc an enhancer agent of saline irrigation water of wheat farms was investigated.

A factorial experiment was conducted based on randomized completed block design with four replications. The Experiment was under the greenhouse condition located in Borazjan Research Institute of Agriculture and Natural Resources during 2012-2013. The first factor comprised four levels of salinity including 4 (control), 8, 12 and 16 dS.m-1. The second factor was application of four levels of zinc including 0, 10, 20 and 30 mg.kg-1 soil.

Our results suggested that increase in zinc concentration could significantly alleviate negative effects of salinity stress on plant height. The highest plant height (84.13 Cm) was achieved by application of 30 mg.kg-1 soilzinc. Although increase in salinity stress reduced wheat growth potential there was no significant difference between 4 dS.m-1 (86.32 Cm) and 8 dS.m-1 (80.19 Cm) on the plant height. The lowest number of grain in spike (36.19) was observed in control treatment while the maximum number of grain in spike (53.44) was produced under 30 mg.kg-1 soil zinc. Increase of salinity from 4 to 16 dS.m-1 drastically reduced the number of grain in spike from 50 to 39.69. Application of 30 mg.kg-1 soilzinc resulted in higher RWC (85.02%) compared to control (69.30%). Increase in zinc concentrations led to a higher chlorophyll and carotenoid content. There was no significant difference between 10 and 20 mg.kg-1 soilzinc sulfate on chlorophyll content. Increasing salinity from 4 dS.m-1 to 12 dS.m-1 resulted in reduction of chlorophyll a from 2.58 to 2.08 mg.gr-1 fw, chlorophyll b from 0.79 to 0.59 mg.gr-1 fw and total chlorophyll from 3.76 to 2.90 mg.gr-1 fw. Zinc promoted synthesis of carotenoid. Carotenoid contents reached 8.43 mg.gr-1 fw by the application of 30 mg.kg soil-1. The maximum carotenoid content (9.30 mg.gr-1 fw) was observed at 8 dS.m-1 salinity while there was no significant difference with carotenoid content of 4 dS.m-1 (8.99 mg.gr-1 fw). However, by increasing salinity stress, the carotenoid content significantly reduced and the lowest carotenoid content (6.70 mg.gr-1 fw) was observed at 16 dS.m-1 salinity. Zinc content of leaf and grain of wheat significantly increase by the application of 30 mg.kg-1 soil zinc and in the highest concentration of fertilizer, zinc content of leaf and grain reached 32.07 and 63.76 mg.kgr-1 respectively. The highest wheat biological yield (1577.50 g.m-2) was observed in 4 dS.m-1 with 30 mg Zn kg-1 soil while the lowest biological yield (986.39 g.m-2) was observed at no added fertilizer and salinity of 16 dS.m-1. The maximum wheat grain yield (692.03 g.m-2) was observed in salinity of 4 dS.m-1 with 30 mg Zn kg-1 soil while the lowest grain yield (459.39 g.m-2) was observed at no added fertilizer treatment and salinity of 16 dS.m-1. Our results clearly proved that application of zinc could alleviate negative effects of salinity stress on wheat grain yield. Wheat biological yield at salinity of 16 dS.m-1 with no added fertilizer reached 986.39 g.m-2 while at the same salinity, application of 30 mg Zn kg-1 soil zinc enhanced biological yield to 1131.80 g.m-2. Although salinity level from 4 to 16 dS.m-1 significantly reduced wheat grain yield application of 30 mg.kg-1 soil zinc increase grain yield from 459.39 g.m-2 to 506.94 g.m-2 in 16 dS.m-1 salinity.

Wheat yield was significantly affected by the quality of irrigation water. The higher the concentrations of salinity, the lower wheat yield will be produced. However, our results revealed that application of zinc is an effective way of reducing salinity to restrict wheat grain yield. This trace element enhances plant production of photosynthetic pigments; therefore, physiological performance of the crop was improved under saline conditions. Application of 30 mg Zn kg-1 soil was highly recommended in farms with saline irrigation water

Introduction One of the objectives of land evaluation method is determining the land suitability degree and class in case of making any changes, including causing elimination or limitation. Thus, as an example, if it could be possible to predict changes in soil salinity for the future, any changes in land suitability class can be investigated based on the predicted variations over time.The most important crops in Neyriz area are wheat and barley. Unfortunately, over the past two decades, improper agricultural management caused reduction and salinization of irrigation water in this region. To this end, the present study was performed to investigate the possibility of changes in the class or degree of land suitability in case of variations in soil electrical conductivity due to irrigation with saline water in Neyriz, for the next 10 years.
Materials and Methods In three soil map units in three regions consisting of Deh-Fazel, Tal-Mahtabi and Nasir Abad, wheat and barley fields were selected and representative pedons were excavated, described and classified. Soil and water samples were obtained and necessary analyses and soil humidity and salinity, hydraulic conductivity and bulk density and water electrical conductivity were determined. Crop yields were evaluated by 1×1 quadrate, soil surface layer hydraulic conductivity was carried out by guelph permeameter and the volume of irrigation water was measured according to pipe discharge in each farm. Soil retention curve was calculated for all soil layers using sand box and pressure plate. van Genuchten equation parameters were gained using RETC software. Afterward, solute transport modeling was done using the software Hydrus and its results were validated using four statistical parameters including Coefficient of determination (R2), Root Mean Square Error (RMSE), Model efficiency (EF) and Coefficient of Residual Mass (CRM) to investigate the possible variation in soil salinity during the next 10 years, the data of the studied period of the crop year between 1392 and 1393 was repeated for 10 years. Qualitative and quantitative land evaluation was performed by standards methods. Finally, the Hydrus results were compared with salinity maps of Neyriz area which were calculated and obtained in the previous research from Landsat images bands for the past 20 years.
Results and Discussion Based on the results, climate suitability class in Neyriz area was suitable (S1) for wheat and relatively suitable (S2) for barley. The limiting factor for barley was the average of maximum temperature in the coldest month for barley. The soil suitability class was suitable (S1) for both crops (wheat and barley) in all farms. Therefore, the land suitability in the studied farmlands was S1 for the wheat and S2 for the barley. Results also revealed that the values for potential production were 10723 and 8677.5 Kg(grain)ha-1 for wheat and barley and for critical production were 1167 and 1297.6 Kg(grain) ha-1 for wheat and barley, respectively in the farms. Amongst the farmlands, only a barley farm which was located in Tal-Mahtabi had the S1 quantitative suitability class and others had S2. The results also showed that if all other conditions like volume and the quality of the irrigation water, precipitation, temperature and evaporation remain constant over the next 10 years, land suitability class will not change but land suitability degree will decrease gradually over time. The validation of the Hydrus model, based on the RMSE values, revealed that the predicted soil salinity and the observed value were very similar and the model had good ability in estimating and modeling soil salinity in the studied area. Comparing the results of modeling and soil salinity maps over the last 20 years have confirmed this trend. Based on the satellite salinity maps, the soil salinity of the studied fields has increased slightly from 2 to 4 dSm-1 between the years 1374 and 1393. Hence it can be concluded that the prediction of Hydrus model about gradual rise in predicted soil salinity and land suitability degree during the next 10 years is acceptable.
Conclusion The present study showed that climate and land suitability class in Neyriz area was suitable and relatively suitable for wheat and barley, respectively. Solute transport modeling showed that land suitability degree will decrease gradually and soil quality will decline over time by assuming constant irrigation and precipitation condition over the next 10 years. Therefore, preventing the expansion of soil salinity and degrading agricultural lands require serious considerations of the authorities in the crisis Managements

Introduction Dust storms or sand storms are some of the meteorological phenomena that demonstrate differences with one another terminologically. These kinds of storms usually occur under arid and semiarid areas in circumstances which the blowing speed of a gale is higher than the erosion threshold. In other words, Dust and sand storms are persistent problems in the Middle East Region. The regional dust storms have bad effects on the health of human life which can cause asthma, bronchitis and lung diseases, due to their carrying micro-organisms (such as bacteria, fungi, spores, viruses and pollen) and their sharp edged particles. Several studies researches have shown that microorganisms mobilized into the atmosphere along with desert soils are capable of surviving long-range transport on a global scale. Dust-borne microorganisms in particular can.
directly impact human health via pathogenesis,exposure of sensitive individuals to cellular components. The chemical components of dust are affecting the microbial life besides the precipitation, wind direction, time of day, season and atmosphere inversion conditions, all affecting the survival of total bacteria communities associated with dust particles, and the microbes are capable of surviving long distance transport. Dust storms have become a major environmental concern during the last decades in the oil- and gas-rich Khuzestan province in the southwestern Iran. Dust storms frequently occur in Khuzestan mainly during summer, and intense dust storms are particularly associated with easterly-blowing winds. High frequency (10-15%) and health outcomes of local dust storms in Khuzestan province, requires an extensive study on various factors of local storms such as heavy metal geochemistry and its environmental consequences are very important. In this paper, we present an overview of the geochemical and geo-environmental characteristics of dust storms in Khuzestan.
Materials and Methods Information about dust storms of source and coverage was obtained from meteorological stations in Khuzestan province. In this study, airborne dust samples were collected to obtain TSP and PM10 by using the high-volume air (HVA) sampler model TCR. The geochemistry of airborne dust samples was analyzed at the Actlabs (Canada). The concentration of V, Co, Ni, As, Cd, Pb and Zn was determined in Actlab, Canada, using ICP-MS method.
Results and Discussion The obtained results showed that Pb concentration in TSP samples ranges between 8.11 and 197 ppm with an average and median value of 23.6 and 11.15 ppm, respectively. The zinc content in PM10 samples, ranges between 4670 and 5000 ppm. Also, Ni has high concentration that ranges between 5.8 - 43.2 in PM10 samples. Lowest concentration of Cobalt is present in PM10 samples that ranges between 0.6 and 4.7 ppm. Vanadium has the highest concentration in Ahvaz samples. Also, PM10 samples include higher Arsenic concentration than TSP samples. Finally, Cd has the lowest concentration in all of the studied heavy metals with the mean value of 0.12 ppm. Positive correlation (0.9) between Cu with V, Co and Ni shows probably a similar source for these elements. Investigation of heavy metals concentration in various dust storms confirms that arsenic has a higher concentration in local storms. Seasonal studies show that V, Co and As have high concentrations in warm periods and Pb has the highest frequency in the cold season, in Khuzestan province. Based on the study of Contamination Factor (CF), the mean CF of heavy metals was in the order Pb > Zn > Cd >As > Ni > Co> V. Also, Degree of Contamination (DC) factor of the studied heavy metals in PM10 samples with mean value of 40 ppm is higher than TSP samples with average value of 10 ppm. In relation to the Enrichment Factor (EF) for V, Co, Ni, As, Cd, Pb and Zn, the EF mean of these metals was in the order Cd > Zn > Ni > Pb > As > V > Co. The highest Arsenic enrichment factor can be seen in PM10 samples.
Conclusion The obtained results from calculation of Integrated Pollution Index (IPI) in PM10 samples showed that, V, Co, Ni and Pb are non-polluted. Also, Cadmium, Arsenic and Zinc showed a low, medium and high levels of pollution, respectively. Furthermore, based on IPI data in TSP samples, Co, As and V were non-pollution and Pb, Ni, Zn showed low level of contamination. Finally, Cadmium in TSP samples in dicated a high level of Integrated Pollution Index

Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that these sediments have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Extensive sedimentological and chronological studies have been carried out on the middle to upper Pleistocene loess during the past decades, but it is necessary to do a comparative research on the older loess deposits. So, this study aimed to conduct a mineralogical and physicochemical investigation on the early Pleistocene loess and to compare it with modern loess soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan.
Materials and Methods The study area is located in a hot and dry climate in loess Plateau east Golestan. According to the previous studies, a total of six profiles were excavated and studied. Then, physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Clay separation was carried out with a specific method to separate the clay as well as identification of clay minerals. After preliminary field observations and determining the horizons for each profile in the region, soil classification was done based on soil taxonomy and WRB. Then, soil samples were prepared from each horizon for physicochemical and mineralogical studies in sufficient quantities.
Results and Discussion Comparing the results of physicochemical properties (such as color, lime percentage, the cation exchange capacity and the ratio of iron, etc.) in paleosol and modern loess soils indicates that in paleosol soils, soil forming processes have passed several stages. Clay mineralogy is a good indicator for past climate change studies in loess.The existence of the arglic horizons and the evolved calcic in paleosols and their absence, in comparison with the modern soils in which they are present, indicate the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region, this color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Decrease in the amount of annual precipitation in the region, compared to the past, has led to decreased smectit and increased chlorite. Therefore, presence of smectit cannot be attributed to the present situation of the region. The presence of these clay minerals in paleosols can be due to wet weather conditions as well as weathering of clay mineral deposits. On the other hand, the dominance of less weathered clay minerals such as illite and chlorite in the late Pleistocene modern loess soils is correlated with the present dry climatic conditions.
Conclusion The simultaneous presence of modern and old loess soils in the studied areas demonstrates the general evolution of geographical and climatic conditions during the Pleistocene period which has altered the properties of these layers and ultimately left out the effects of high clay conditions, which is a combination of climatic evidence and intermittent pedogenic soil formation processes. The presence of early Pleistocene loess soils between late Pleistocene loess sediments in Golestan province and the conditions of the study provided pedological and mineralogical comparisons of modern and paleosols in these areas and the results clarified a part of the climate change in northern Iran. The past climate study allows for prediction of the current and future climate change process. Therefore, a more accurate study of clay minerals as the key to all soil behaviors and past climate change in different parts of the eastern Golestan plateau can be very useful in completing studies of evidence of past climate change in paleosol soils