Showing 5 results for Chemical Forms
M. Rajaie, N. Karimian,
Volume 11, Issue 1 (4-2007)
Abstract
Cadmium (Cd) and its rate in soil have received lots of attention because it is easily taken up by plant root, making it 20 times more toxic in comparison with other heavy metals. Knowledge about the factors affecting Cd availability and conversion of its chemical forms is, therefore, important. Sequential extraction has been used as a suitable method for identification of chemical forms and their relationship with plant availability, but in soils of Iran less attention has been paid to studying the change in chemical forms as affected by time. The present research was designed to study the change in Cd chemical forms as affected by application rate and time of incubation in two soil textural classes. A clay loam calcareous soil [Fine, mixed (calcareous), mesic Typic Calcixerepts] was converted to sandy loam soil by adding pure quartz sand and both soils were treated with 0, 5, 15, 30, and 60 mg Cd / kg soil as cadmium sulfate and incubated at room temperature near field capacity moisture. After 0, 1, 2, 4, 8, and 16 weeks, chemical forms of Cd were determined by sequential extraction. Results showed that, depending on the textural classes, about 82 and 87 % of applied Cd was converted to soluble+exchangeable, carbonate, and organic forms. In both soils carbonate fraction was dominant. Conversion of applied Cd to soluble+exchangeable and carbonate forms in sandy loam was higher than in clay loam. For organic, manganese oxide, amorphous iron oxide, and residual forms, the reverse was true. The crystalline iron oxide form was less than detection limit of atomic absorption in both textural classes. Increasing the application rate caused an increase in all forms of Cd but the percentage increase depended on the capacity of different soil components for Cd retention. Carbonate showed the highest capacity for retention. The effect of incubation time on conversion of Cd to different forms was significant. However, in almost all treatments more than 80 % of added Cd was converted to carbonate and organic forms immediately, and the proportion approximately stayed the same throughout the course of experiment.
M. Zolfi Bavariani , M. Maftoon ,
Volume 14, Issue 54 (1-2011)
Abstract
Due to low availability of zinc and copper in calcareous soils and the antagonism of these nutrients with each other, the study of their effects on growth and chemical composition of rice seems to have great importance. Also, the relations among different chemical forms of Zn and Cu and plant responses are very important, which can be used in investigation of antagonisms of these nutrients as well. Therefore, by application of different levels of Zn and Cu, their effects on plant growth and nutrient concentration in the plant were studied and different forms of these nutrients in soil were determined. Results showed that zinc application increased plant growth, Zn concentration and total uptake, but decreased Cu concentration in the plant. However, copper application showed no significant effects on the plant growth, but increased Cu concentration and total uptake and decreased Zn concentration in the plant. Also, the results showed an increase in carbonatic, adsorbed and exchangeable Zn forms and exchangeable Cu form by Zn application. Carbonatic form of zinc has maximum effects on concentration and total uptake of this element in the plant. Copper application increased carbonatic and organic forms of this nutrient in soil, and there was maximum correlation between organic form of Cu and its concentration and uptake in the plant
A. Kazemi, H. Shariatmadari, M. Kalbasi,
Volume 16, Issue 59 (4-2012)
Abstract
Iron deficiency is most widespread among plant nutrients. Nowadays, different materials such as inorganic salts, organic chelates, soil acidifying materials and industrial wastes are used to correct iron deficiency. Slag and convertor sludge of steel factories are among the industrials wastes for this purpose. These materials contain considerable amount of iron produced in large quantities every year. Application of slag and convertor sludge to soil may affect bioavailability and chemical forms of iron in soil. Sequential chemical extraction technique has been widely used to examine these chemical forms, and thus to better understand the processes that influence element availability. It was, therefore, the objective of this study to investigate the application effect of slag and convertor sludge of Esfahan Steel Mill on the chemical forms of iron, distribution of these forms and bioavailability of iron in surface (0-20cm) and subsurface (20-45cm) soil of three research fields. The results showed that more than 99% of the applied Fe occurred in residual, Fe oxide and hydroxide and free forms. Application of slag and convertor sludge for three consecutive years increased chemical forms and DTPA extractable iron in surface and subsurface soil of three fields.
H. R. Owliaie,
Volume 16, Issue 62 (3-2013)
Abstract
Iron and manganese oxides as well as hydroxide minerals are among active constituents in soils because they are sensitive to environmental changes and often move frequently along soil profile. Therefore, their chemical forms content and their ratios are used as a soil developmental criterion. The present study was conducted in order to evaluate the effects of topography and drainage conditions on chemical forms of Fe and Mn along a soil catena in Dasht-e- Roum plain, in Kohgilouye Province. According to the results, maximum pedogenic Fe and Mn (Fed and Mnd) was found in more stable geomorphic surfaces. Higher values of Fed and Mnd were mostly observed in surface horizons compared to soil depth. Aquic soils exhibited higher contents of poorly crystalline Fe and Mn (Feo and Mno) and higher contents of Fed and Mnd. A significant correlation between clay content and Feo, Mno, Fet and Mnt contents was found. In addition, aquic condition increased Feo/Fed, Mno/Mnd and Mnd/Fed, 3.1, 4.3 and 1.9 times respectively but decreased the Fe crystallinity index 2.6 times. Aquic soils seem to have more favorable conditions for the formation of pedogenic Mn compared to pedogenic Fe, hence higher content of Mnd/Fed was observed in these soils
S. Shakeri, A. Azadi, M. Saffari,
Volume 24, Issue 4 (2-2021)
Abstract
Determining the relative distribution of each chemical form of the elements and their relationship with the physical, chemical, and clay mineralogical properties of soils can help researchers to achieve the sustainable agricultural management. The present study was conducted to evaluate the chemical forms of four micronutrients (Zn, Cu, Fe and Mn) in some surface and subsurface soils of Kohgiluyeh and Boyer Ahmad province and their relationship with the physical, chemical and mineralogical properties of the soils. The results showed that the exchangeable and sorbed chemical forms of the studied elements were very low and negligible, but the residual, carbonate, and organic forms had the highest to lowest values of the chemical forms of these elements, respectively. Examination of the correlation of the chemical forms of these elements with soil properties showed the effective correlation of organic carbon values with the Zn chemical forms; also, there was a correlation between clay, silt, cation exchange capacity and calcium carbonate and the chemical forms of Cu, Fe and Mn. The correlation between the quantities of clay minerals and the chemical forms of these elements showed that the amounts of different forms of the studied elements were directly related to 2:1 clay silicate minerals (especially vermiculite). Evaluation of Fe and Mn chemical forms also showed that the amounts of these elements were higher in the soils with developed profiles (Alfisol and Mollisol), the wetter climate and zeric moisture regime rather than in soils with non-developed profiles (Entisols and Inceptisols) and a drier climate and a ustic moisture regime. In general, the results showed that variations of soil forming factors such as climate (as well as the total amount of each micronutrients), could be effective on the chemical forms of micronutrients (especially on Mn and Fe); these can be effective in the management of weakly to highly-developed soils orders.
