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Andisol soil was collected from a native p … Andisol soil was collected from a native pasture in Tsuruoka, Yamagata Prefecture, Japan. Ammonium sulfate, superphosphate, and potassium sulfate were added to the air-dried Andisol soil at rates of 4.76, 5.88, and 1.85 g/kg of the soil, respectively. The pH (H2O) of the soil was adjusted to 5.80 by adding lime at the rate of 8.93 g/kg. Two kilograms of the fertilized Andisol soil were transferred to a 1:5000-A Wagner pot. Six mullite ceramic tubes (50mm x 0.6 mm) and a Teflon tube (200mm x 0.7 mm) were embedded into the fertilized soil. Rice (Oryza sativa L.) seeds were sown around the tubes and three seedlings were grown around each tube. The plants were grown in a glasshouse at the Yamagata University, Tsuruoka, Japan, from August 17 to August 28, 2009. Pots without rice plants were also prepared. Following the apparatus setup used by Tawaraya et al., a plastic syringe (5 mL) was connected to a Teflon tube 11 days after the rice seeds were sown, and 1mL of the soil solution was collected in the syringe. Of the collected soil solutions, 96 mL was mixed with 4 mL of 5-mM internal standard (200 mM at final concentration) and then purified on the SPE columns.<br /> n purified on the SPE columns.<br />
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