Poster Number 503
Wednesday, 8 October 2008
George R. Brown Convention Center, Exhibit Hall E
A microcosm experiment was conducted to determine the influence of soil redox and pH on the potential metal and nutrient available in lowland rice soils. Soil suspensions, under controlled and uncontrolled pH environment, were incubated alternately from oxidizing to reducing and from reducing to oxidizing conditions. The water-soluble and ammonium acetate (NH4OAc)-extractable concentrations of Zn, Fe, Mn, P and Si were analyzed. In controlled pH condition, the highest concentrations of water-soluble and NH4OAc-extractable Zn, Fe and Mn were observed in soil suspension at pH 4.0, whereas the highest concentrations of water-soluble P and Si were recorded at pH 7.0. In uncontrolled pH experiment, the concentrations of water-soluble and NH4OAc-extractable Fe and Si in both soils varied, whereas the water-soluble and NH4OAc-extractable concentrations of Zn, Mn and P in both soils remained constant. The concentrations of Fe and Mn were greatly influenced by soil redox potential. The results suggested that availability of plant nutrients in lowland rice soils was associated with the oxidation-reduction and reduction-oxidation cycles.