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The distribution of inorganic P fractions and their relationships with soil properties was studied in 17 slightly acidic to slightly alkaline soils (pH range 5.37 to 7.61). The soils were selected from agricultural fields of the north of Iran. Inorganic P fractionation included successive extraction with NaOH (NaOH-P), citrate-bicarbonate (CB-P), citrate two times (C1-and C2-P), Citrate-ascorbate (CAs-P), citrate-dithionite-bicarbonate (CBD-P), sodium-acetate buffer (NaOAc-P) and HCl (HCl-P). Results showed that the abundance of P fractions was in the order NaOH-P (35.67 mg kg -1 ) , NaOAc-P (39 mg kg ), HCl-P (417 mg kg -1 ). Among soil properties, pH had almost a linear negative relationship with NaOH-P and a linear positive relationship with HCl-P; in addition, it significantly affected C1-P, CAs-P and NaOAc-P. Oxalate extractable Fe showed a significant positive correlation with NaOH-P and CAs-P, while calcium carbonate equivalent (CCE) had a significant positive correlation with NaOAc-P and HCl-P.

AbstarctIntroduction Vermicomposting could increase nutrients availability including phosphorus. During vermicomposting, a decomposition of organic substrates leads to the production of several organic acids, such as malonic, fumaric, succinic acids. Microorganisms both in the intestinal organ of the worms and the organic waste have the ability to convert insoluble P into soluble forms. Little information exists about the effects of vermicomposting on rock phosphate (RP) solubilization. Present study was conducted to evaluate the solubilization of powdered RP during vermicomposting. Results Vermicomposting and RP application increased NaHCO 3 -P i . Rock phosphate application in vermicomposting significantly increased NaHCO 3 -P o . Vermicomposting significantly increased NaOH-P i in all of the treatments. RP application and vermicomposting increased HCl-P i in both organic sources. Generally, vermicomposting increased HCl-P o . Vermicomposting decreased pH but its effect was more evident in the presence of RP. Vermicomposting increased EC in both organic sources. Conclusion Present study showed that vermicomposting helps to enhance the transformation of P from RP into various organic or inorganic P forms, which would be readily or moderately available, thus, increase the availability of P from both RPs.

Clay minerals of calcareous sedimentary rocks of southern Iran, part of the old Tethys area, were investigated in order to determine their origin and distribution, and to reconstruct the palaeoclimate of the area. Chemical analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and thin-section studies were performed on the 16 major sedimentary rocks of the Fars and Kuhgiluyeh Boyerahmad Provinces.Kaolinite, smectite, chlorite, illite, palygorskite and illite-smectite interstratified minerals were detected in the rocks studied. The results revealed that detrital input is possibly the main source of kaolinite, smectite, chlorite and illite, whilein situneoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks.The presence of a large amount of kaolinite in the Lower Cretaceous sediments and the absence or rare occurrence of chlorite, smectite, palygorskite and illite are in accordance with the warm and humid climate of that period. Smaller amounts of kaolinite and the occurrence of smectite in Upper Cretaceous sediments indicate the gradual shift from warm and humid to more seasonal climate. The occurrence of palygorskite and smectite and the disappearance of kaolinite in the late Palaeocene sediments indicate the increase in aridity which has probably continued to the present time.

Accumulated anthropogenic heavy metals in the surface layer of agricultural soils may be transferred through the food chain via plant uptake processes. The objectives of this study were to assess the spatial distribution of lead (Pb) in the soils and wheat plants and to determine the soil properties which may affect the Pb transferring from soil to wheat plants in Zanjan Zinc Town area, northwestern Iran. A total of 110 topsoil samples (0-20 cm) were systematically collected from an agricultural area near a large metallurgical factory for the analyses of physico-chemical properties and total and bioavailable Pb concentrations. Furthermore, a total of 65 wheat samples collected at the same soil sampling locations were analyzed for Pb concentration in different plant parts. The results showed that elevated Pb concentrations were mostly found in soils located surrounding the industrial source of pollution. The bioavailable Pb concentration in the studied soils was up to 128.4 mg kg(-1), which was relatively high considering the observed soil alkalinity. 24.6% of the wheat grain samples exceeded the FAO/WHO maximum permitted concentration of Pb in wheat grain (0.2 mg kg(-1)). Correlation analyses revealed that soil organic matter, soil pH, and clay content showed insignificant correlation with Pb concentration in the soil and wheat grains, whereas calcium carbonate content showed significantly negative correlations with both total and bioavailable Pb in the soil, and Pb content in wheat grains, demonstrating the strong influences of calcium carbonate on Pb bioavailability in the polluted calcareous soils.

There are relatively few comprehensive documents about the mineralogy of arid regions, and no study has been reported on the characteristics and mineralogical trends of the soils of arid regions in the Hormozgan Province, southern Iran. The objective of this study was to identify the variations in physical, chemical, and mineralogical composition of soils of the region lying between the southern part of Zagros and Persian Gulf to Oman Sea. X-ray diffraction, thin-section studies, and transmission electron microscopy with energy-dispersive X-ray spectroscopy were conducted to determine the relationship between mineral distribution and climate, along with an evaporate environment reflected by a variety of geological structures. On the basis of nature and composition, the soils can be classified into Alluvial soils rich in silt and Desert soils, sandy soils poor in organic carbon in which evaporate Tertiary Formations played an important role on the formation of contemporary minerals. The maximum portions of silt and sand fraction were composed of quartz and alkali-feldspars, whereas calcite and dolomite were elevated in soil samples without acid treatments. The clay mineralogy results revealed that detrital input and inheritance are possibly the main source of kaolinite, smectite, chlorite, and illite, whereas in situ neoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks. The chemical composition of clay suspension, determined by electron microprobe analysis, corresponds to that of Mg-rich predominant palygorskite, with a degree of tetrahedral substitution from almost less than 2 to 23%. In conclusion, the soil mineralogy did not vary systematically with depth but showed spatial variations, and the relative influence of mineral distribution in topsoils can be summarized as follows: parent rocks > geomorphological setting > water table position > climate > physiography and soil evolution. The soils, in general, contained moderate to high amounts of weatherable minerals, indicating their early to intermediate stages of development. Sites of studied pedons and rocks. (C) Soil moisture regime map. (D) Soil temperature regime map. No scale bar for the maps.

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