現場に近い条件で土壌の硝酸保持能を直接測定する実験法

概要

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Experimental conditions for the direct measurement of nitrate retention of soils were investigated. The method is based on the recovery ratio for nitrate ion that was added to soils as diluted solution. The difference in concentration between the initial solution and supernatant after shaking and centrifuging is the amount of nitrate retained on soil particles. The investigation showed that addition of 7.5 mL of 5 mmol L^<-1> potassium nitrate solution to 5 g air-dried fine earth with 30 min shaking could achieve conditions of moisture and nitrate concentration similar to Japanese upland fields. The measurement could be completed within 3 h and the precision of replicated measurement was high. The value obtained by this method, tentatively called nitrate holding capacity (NHC), showed a clear positive relation with AEC value for 15 soil samples and 5 weathered tephra. However NHC values were smaller than AEC values in samples with large AEC values; this result indicates that only a part of the total positive charge works as nitrate retention sites in field conditions.
日本ペドロジー学会の論文
2008-12-31