Abstract: The soils of the lower Mississippi Delta are derived from the Mississippi or Red River depositions or some combination of these two.
Profiles of the Iberia, Baldwin, Buxin, Sharkey, and Mhoon were selected for the study. The comparative results indicate that the Sharkey was highest in cation exchange capacity and exchangeable calcium and magnesium. Base saturation was highest in the Iberia and lowest in the Baldwin. The variation in cation exchange capacity was possibly due, in general, to the differences in texture, except for the Iberia. The clay fraction of the Iberia contained slightly larger quantities of high cation exchange capacity minerals than the other soil series of the study.
Silica was highest in the Baldwin while the oxides of aluminum, iron, magnesium, and potassium were highest in the Buxin. Iberia was highest in calcium oxide. Silica-sesquioxide and silica-ferric oxide ratios were highest in the Sharkey and lowest in the Buxin. The silica-alumina ratio was highest in the Baldwin and lowest in the Buxin. The comparison of the Buxin with soils of the Mississippi River deposition indicates that the Red River depositions were generally lower in silica-sesquioxide ratios and total calcium oxide and higher in total magnesia and potash.
The X-ray patterns indicate that montmorillonite and illite were the dominant clay minerals present. The greatest quantities of montmorillonite were generally found in the Iberia profiles, although this was not always true. Also, in general, the content of montmorillonite increased and illite decreased with profile depth. Secondary minerals were halloysite, kaolinite, vermiculite, and chlorite. The cation exchange capacity of the clay fraction also indicated the higher content of montmorillonite or associated minerals in the Iberia than in the Buxin, Baldwin, Sharkey or Mhoon soils.