Iranian Journal of Soil Research
Year:2013 | Volume:26 | Issue:4|Papers Count:14

Recently, concerns about conversion of agricultural lands to brick factories have come to the fore. In Iran, few studies have been focused on this issue. This study was conducted to (1) determine the areal extent and magnitude of agricultural lands which have been converted to brick factories in Marvdasht and Kavar plains in Fars Province, and (2) investigate the environmental consequences of brickworks. The aerial photos of the study areas acquired in 1993 and 1955 were used to verify the status of land under brick factories in the past. Google Earth facilities were used to locate the brick factories and map their geographic distribution in 2011. To determine the capacity of the converted lands, several soil profiles were studied in the converted agricultural lands. Data integration was done using Arc GIS software. The number of brick factories and the land areas they occupy have grown dramatically in recent years. Currently, the land swallowed by brick factories covers 560 and 740 ha in Marvdasht and Kavar plains, respectively. The converted land areas show a three-time growth in Marvdasht plain and an eight-time growth in Kavar plain since 1993. Soil survey investigations during fieldwork revealed that most of the converted surfaces belong to class II land with slight limitations for farming. The opportunity to annually produce about 8000 tons of wheat on about 1300 ha of the converted lands has been lost, as a result of improper land use change in Marvdasht and Kavar plains. Land use change by brick factories is a threat to agricultural production in Fars Province. Moreover, intensified brick production has increased adverse environmental effects by augmenting land, water and air pollution. If continued, brickworks not only will consume vast areas of prime agricultural lands, but also, the added value of the agricultural lands will persuade the farmers to sell their lands and immigrate to big cities.

Environmental pollution is one of the main problems of human societies. Plants are able to affect the mobility of heavy metals in the rhizosphere due to root exudates and other mechanisms resulting in a change in their phytoextraction ability. One of the methods for reclaiming contaminated soils, called phytoremediation, makes use of plants. Phytoremediation has a lower cost, is compatible with nature, and requires less equipment and facilities. Khoozestan province not only has many oil wells but also many industries that are causing soil contamination. Therefore, there are several sources of soil pollution in the date palm orchards in Khoozestan province necessitating research on reclamation. This study was carried out with three replications in randomized block design in greenhouse at the Date Palm and Tropical Fruit Research Institute in Ahvaz with the following treatments: 1-control (only date treess), 2- only corn, 3-only alfalfa, 4-only Sunflower, 5-corn intercropped with date palm, 6-alfalfa intercropped with date palm, 7- sunflower intercropped with date palm. After the crops were grown for one growth period, they were removal from the soil, and then were weighed. Concentrations of nitrogen, phosphorus, potassium, copper, manganese, and lead in soil and plant were measured. Uptake index was calculated. The results showed that alfalfa intercropped with date palm recorded significantly higher amount of fresh and dry weight than corn intercropped with date palm in pot. Sunflower and alfalfa grown alone recorded the highest and lowest lead uptake index, respectively.The highest rate of lead translocation factor belonged to alfalfa intercropped with date palm. In other words, alfalfa translocations of lead from root to shoot while intercropped with date palm was more than the other treatments.

Study of the distribution of Cu in the soil allows investigating its mobility and bioavailability. In this research, available fractions of Cu in some calcareous soils treated and untreated with sewage sludge were investigated. After incubation of the soils for 1 month, different forms of Cu including exchangeable Cu and the forms/ fractions associated with carbonates, organic matter, Fe and Mn oxides and residual Cu were determined and wheat was planted in these soils. After 8 weeks, plants were harvested and Cu concentration, Cu uptake, and yield indices were determined. Available fractions of wheat were determined using correlation coefficient between plant responses and Cu fractions. Results showed that all Cu fractions and plant indices were increased by usage sewage sludge. Results of pot experiment indicated significant correlation between Cu concentration in wheat with exchangeable (r=0.66*), Cu associated with Fe and Mn oxides (r=0.75*), and residual (r=0.75*) in untreated soils. Moreover, significant correlations were found between Cu uptake with residual fraction (r=0.64*) in untreated soils.Also Results showed that Cu concentration in wheat was significantly correlated with exchangeable (r=0.89*), Cu associated with Fe and Mn oxides (r=0.65*). Therefore exchangeable Cu and the forms associated with Fe and Mn oxides and residual fractions in untreated soils, and exchangeable Cu and the forms associated with Fe and Mn oxides fractions in the soilstreated with sewage sludge, could be considered as available fractions for wheat.

Twenty two soil samples with various chemical and physical properties were collected from different sites of Khuzestan province and chemical forms of soil cadmium (Cd) were determined using a sequential extraction technique. A greenhouse study was conducted to evaluate the relationships between the chemical forms of cadmium and its availability for wheat plant. The results showed a positive correlation between soil DTPA-extractable Cd and electrical conductivity (EC) in the studied soils (r=0.65, p<0.01). The soluble+exchangeable form was lowest (5.1%) and the carbonate fraction was the highest (40%) cadmium fraction in these soils. Soluble+exchangeable fraction was positively correlated with soil DTPA-extractable Cd and electrical conductivity. Carbonate fraction showed a significant correlation between clay and active carbonate calcium content in the studied soils. The results also showed that cadmium concentration in wheat grain was not correlated with any soil physico-chemical properties as well as soil Cd fractions. Although comparing the results for soil total Cd with those reported as contamination threshold revealed that more than fifty percent of the studied soils were Cd contaminated, only 3.1% of the grain samples exceeded maximum permissible Cd concentration suggesting total Cd concentration is not an appropriate index for Cd uptake from soil.

Although there are different devices for rapid and low cost monitoring of some soil properties, extended field surveys, both in space and depth, seem to be necessary for mapping of these and other soil attributes. In this study, electromagnetic induction device (EM38) has been introduced as a tool for rapid and low cost measurement of soil salinity and other attributes. Main objective of this study was to test and evaluate capabilities of this device for monitoring soil cations and anions in addition to salinity in Azadegan plain, west of Iran. For this purpose, soil samples were taken at different locations and depth intervals, simultaneously with EM38 readings. Relationships between EM38 readings and anions, cations, salinity and Sodium Absorption Ratio (SAR) were investigated through statistical analysis approaches. Results of this study indicated significant correlations between EM38 readings and soil sodium measures as well as SAR. The mentioned result suggests this device as a rapid tool for measurement of soil sodium in different parts of the country.

Precise mapping of the spatial distribution of salt-affected soils is prerequisite for effective management of these soils. This study was carried out for mapping soil salinity of 78000 hectares of Ardakan soils (0-30 and 0-100 cm) using 151soil samples which were taken based on hyper cube method. The secondary variables used in co-kriging method were ETM data, terrain analysis and EM38 readings. The best model was selected by means of cross validation and error evaluation methods, such as RMSE and ME methods. Results showed that cokriging method with EM38 data as a secondary variable was the best method for prediction of soil salinity (69.1, 30.55, 48.8 and 20.41, respectively). Results recommended EM38 as secondary data for mapping soil salinity. Additionally, results showed the largest amount of soil salinity in the north of the area and the smallest values in the areas with more elevation. The concavely shaped plain could help to move soluble salts toward the north of area in which the soils with highest electrical conductivity are found.

Mismanagement of water in irrigated fields of Dasht-e-Azadegan (DA) in west of Khuzestan province, lower part of Karkheh river basin, with low slope and poor natural drainage, influences ground water table and also salinity of its adjacent soil profile, especially when the groundwater is saline. Such condition can contribute to reduction of crop yield and degradation of soil and water resources gradually in a long term period. The main objective of this study was to investigate and evaluate the salinity of soil profile in saline-waterlogged area of Azadegan plain through field surveys, laboratory measurement, and data interpretation. For this purpose eighty ground water and soil profile samples were collected from DA during August 2007. Samples were analyzed for ECe and, finally, relationships between ground water and soil salinities (ECgw and ECe) of different depth intervals were interpreted. Results of the study indicated that shallow/saline ground water significantly influenced the salinity of adjacent soil layers and the effect increased with increase in soil depth. Additionally, a simple relationship was obtained for ECe vs. ECgw as ECe=0.27ECgw+6.27 (R2=0.70).

Salt-affected soils cover up to 20 million hectares of our country. The objective of this study was to derive PTFs of some salt-affected soils to predict the parameters of van Genuchten equation and water retention at a pre-defined potential from readily/easily obtainable soil characteristics. For this purpose, 68 soil samples were chosen from south part of Tehran (saline and saline-sodic soils). Moisture retention curve for these samples were determined at matric potential of 0, -10, -33, -100, -300, -500, -1000 and -1500 kPa. Particle size distribution, calcium carbonate, bulk density, organic carbon, EC and SAR were measured and RETC program was used to obtain the Van Genuchten equation parameters. As to the EC and SAR effect on pore size distribution of soil, these parameters were used in pedotransfer functions as predictor parameters. Also, performance of derived functions in estimation of moisture retention curve was compared with a number of functions (13 functions) that previously were provided by different researchers. Generally, the result of this study showed: 1- Water retention at a pre-defined potential and parameters of van Genuchten equation can be estimated by pedotransfer functions with reasonable accuracy (point transfer functions: 0.844³R2Adj³0.577 and 0.0296³RMSE (cm3/cm3) ³ 0.0121), 2- Sensitivity analysis results showed that the sensitivity of most point functions to changes in bulk density was more than the rest of the parameters and clay-silt ratio, EC, and sand were at the next levels, 3- Considering the coefficient of EC in the equations, partial coefficients of correlation, and results of sensitivity analysis, higher amounts of EC could somewhat affect pore size distribution and, consequently, the shape of moisture retention curve of the soils. This change, which is caused by swelling and shrinkage, to some extent can be predicted via introduction of EC and SAR parameters in developing the equations, 4- Comparison of previous functions with those obtained in this study show that derived functions in this research are the best functions for estimation of soil moisture retention curve.

In order to investigate the effects of plant growth promoting rhizobacteria (PGPR) at various levels of nitrogen and phosphorus fertilizers on phyllochron and leaf appearance rate of barley (Hordeum vulgar L.), an experiment was conducted at the Research Farm of Islamic Azad University of Ardabil during 2009 growing season. The combination of nitrogen fertilizer at three levels (0, 40, and 80 kg N/ha as urea) and phosphorus fertilizer (0, 30, and 60 kg P2O5/ha) were factorially assigned to the main plots and seed priming with plant growth promoting rhizobacteria (PGPR) at four levels (no priming, seed priming with Azetobacter chorchorum strain 5, Azospirillum lipoferum strain OF, and combination of seed priming with Azosprilium+Azetobacter) were assigned to the subplots. The results showed that phyllochron, leaf appearance rate, number of leaf per plant, leaf dry matter and leaf area index were significantly affected by nitrogen and phosphorus levels and seed priming with PGPR. With increasing nitrogen and phosphorus levels, the phyllochron decreased but rate of leaf appearance increased. Leaf appearance rate in seed priming with both Azospirillum+Azetobacter was more than Azospirillum or Azetobacter priming alone. Leaf dry matter was increased significantly in the combined treatment of seed priming with PGPR×levels of N and P fertilizers.Maximum leaf dry matter was obtained in the plots which had received the highest levels of nitrogen and phosphorus fertilizers in seed priming with Azospirillum compared to the control treatment. The highest number of leaf per plant and leaf area index were observed in seed priming with both Azospirillum +Azetobacter, and the least values of these parameters were recorded in no priming. Maximum number of leaf per plant and leaf area index were obtained at the highest levels of N and P fertilizers and the minima were observed in treatments with no fertilizer application. In all sampling stages, leaf area index in seed priming with PGPR was more than no priming (control). Thus, in order to increase leaf appearance rate, number of leaf per plant, and leaf area index, seeds priming with Azetobacter+Azospirillum at the highest levels of nitrogen and phosphorus fertilizers can be suggested.

Plant growth promoting rhizobacteria (PGPR) are considered to promote plant growth using one or more mechanisms. Pseudomonas bacteria, specially P.fluorescensand P. putida, are the most important kinds of PGPR. Production of auxin by PGPR is one of the main mechanisms that could promote growth and yield of plants. In this research, fifty strains of Fluorescent Pseudomonads selected from microbial culture collection of Soil and Water Research Institute were used. The ability of the strains for production of auxin compounds were evaluated by high performance liquid chromatography (HPLC). Results indicated that 36 isolates (72%) were able to produce at least one type of indolic auxin compounds including indole-3-acetic acid (IAA), indole-3- acetamid (IAM), and indole-3-lactic acid (ILM). None of the strains produced indole-3-butyric acid (IBA). A greenhouse experiment was conducted to evaluate the effects of inoculating canola seeds with IAA-producing strains on canola growth. The results showed that the strains significantly increased the height of the aerial parts (up to 15.5%), shoot dry weight (up to 58%) and root dry weight (up to 305%). Also vivid differences were seen in morphology and density of root hairs of plants inoculated by the strains. Hence, the studied strains have positive effects on canola plant growth indices through producing IAA.