Despite advances in instrumentation for direct determination of SO 2‐ 4 , many investigators analyzing saline soils continue to estimate SO 2‐ 4 by difference between the sums of major cations and anions and to measure gypsum by methods that avoid direct SO 2‐ 4 determination. The present study compares SO 2‐ 4 in saturation extracts as estimated by difference with SO 2‐ 4 measured by single‐column ion chromatography for saline Aeric Calciaquolls and Typic Haplaquolls in eastern North Dakota. Results should be applicable throughout the Northern Great Plains. For extracts of sulfatic, saline soils, estimation of SO 2‐ 4 by difference compared favorably with SO 2‐ 4 determined directly. Results were more variable for highly chloridic soil extracts because errors from other methods were large relative to the amount of SO 2‐ 4 present. Gypsum was determined by using a sufficiently dilute extract to completely dissolve the gypsum present in the soil sample. Gypsum content was calculated in two ways, based either on Ca 2+ or SO 2‐ 4 measured in the dilute extract. For highly chloridic soils, gypsum contents based on Ca 2+ determination were essentially equal to the results based on SO 2‐ 4 data. For sulfatic soils, gypsum contents were lower when Ca 2+ values were used due to loss of Ca 2+ to the exchange complex during the extraction process.
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Skarie et al. (1987) studied this question.