This study was conducted in order to evaluate effects of phosphorous fertilizer (PF)s from sources of triple superphosphate (TSP) and di-ammonium phosphate (DAP) and organic fertilizer (OF)s from sources of cow dung manure (CDM) and municipal solid waste compost (MSWC) on phosphorous (P) fractions include aluminium-P (Al-P), iron-P (Fe-P), Reductant soluble-P (RS-P), calcium-P (Ca-P) and available-P (Olsen-P) fractions under rice cultivation condition. The trials were carried out in calcareous and acidic soils. PFs were added at three levels (10, 20 and 30 mg kg-1) and OFs was applied at the rate of 10 t.ha -1 . Results of this study showed that Ca-P was the predominant form of P in calcareous soil while Fe-P and Al-P were predominate in acidic soils. In calcareous soil, all forms of P under submerged conditions had been increased because of using PFs both alone and in combination with OFs. In acidic soil, significant amounts of P fractions were found only in Fe-P and RS-P fractions. Accordingly, Fe-P fraction increased in 10 mg kg -1 treatment and RS-P increased in MSWC treatment. Among the inorganic P fractions in calcareous soil, only RS-P; and in acidic soil, Ca-P and Fe-P significantly correlated to Olsen-P.

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Cadmium (Cd) is a critical environmental chemical in which sorption reactions control its entry into soil solution. The aim of the present study was to evaluate Cd sorption characteristics of some soils of the northern part of Iran with a wide range of physicochemical properties. Duplicates of each sample were equilibrated with solutions containing 5 to 500 mg Cd L -1 with 0.01 M CaCl 2 as background solution. The quantity of Cd retention was calculated as the difference between initial and equilibrated Cd concentration. Sorption isotherms including Freundlich, Langmuir, Temkin, Dubinin-Radushkevich, and Redlich-Peterson were used to evaluate the behavior of Cd sorption. Cadmium sorption data were well fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms. The constant of Freundlich equation (k F ) and adsorption maxima (b L ) of Langmuir equation were related to pH and cation exchange capacity (CEC). The maximum buffering capacity (K d ) was significantly correlated with pH (R 2 =0.52, p≤0.001) and calcium carbonate equivalent (CCE) (R 2 =0.63, p≤0.001).Redlich-Peterson constants (k RP and a RP ) were significantly correlated with pH (R 2 k RP =0.30, p≤0.007) and (R 2 a RP =0.27, p≤0.012). It seemed that pH, CEC, and CCE were the main soil properties regulating Cd retention behavior of the studied soils.