Effects of phosphorus and organic fertilizers on phosphorus fractions in submerged soil
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 avail-able-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.