リン酸緩衝液土壌抽出ろ液の吸光度測定による湛水培養可給態窒素量の簡易推定

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The effects of extracting temperature on the absorbance of soil extracted solution with neutral 1/15 mol L^<-1> phosphate-buffered solution were investigated. The efficiency of dividing soil samples into several groups by taxonomical group, soil chemical properties and history of soil management was also investigated to estimate more efficiently the amount of soil available nitrogen released under waterlogged conditions from the absorbance of soil extracted solution with phosphate-buffered solution. As the indicators of soil chemical properties, C/N ratio, phosphate absorption coefficient, amounts of free iron oxide, extractable iron and manganese with pH 3-ammonium acetate, and cation exchange capacity (CEC) were investigated. 1) The absorbance (420 nm) of soil extracted solution with phosphate-buffered solution increased as extracting temperature rised. However, Arrhenius's law could be applied to the increasing absorbance, and it was possible to convert absorbance at any extracting temperature within 10-30℃ into absorbance at standard temperature (i. e., 20℃) with the value of the activating energy (31.8 kJ mol^<-1>). So the absorbance of soil extracted solution should be represented by the converted value at 20℃ using Arrhenius's law. 2) The relationship between amount of available soil nitrogen released under waterlogged conditions and absorbance of soil extracted solution showed a higher correlation when we divided soil samples into 2 or 3 groups as follows. Andosol soil samples were divided into two groups by the phosphate absorption coefficient at 18 g kg^<-1>. Yellow soil samples were divided into two groups by CEC at 20 cmol(+)kg^<-1>. Gray Lowland soil samples were divided into 3 groups by the amount of free iron oxide (i. e., below 13 g kg^<-1> and 20 g kg^<-1> or over). Gley soil samples were divided into groups by the total amount of pH 3-ammonium acetate extractable iron and manganese oxidation-reduction equivalence (i. e., 4 mmol kg^<-1> or over). 3) From the above results, the amount of available soil nitrogen released under waterlogged conditions could be estimated simply and rapidly from the absorbance of soil extracted solution in the case of some series of soil groups without the decomposing soil extracted solution and without determining the amount of soil nitrogen in the soil extracted solution.
社団法人日本土壌肥料学会の論文
1998-08-05

リン酸緩衝液土壌抽出ろ液の吸光度測定による湛水培養可給態窒素量の簡易推定

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