Physical and Chemical Properties of Some Iowa Soil Profiles with Clay‐Iron Bands

Field and laboratory studies were made on some sandy soils of Iowa to determine the extent and nature of the clay‐iron bands which occur in some of these soils. Observations made in the field studies indicate that the iron and silicate clay enriched bands have a depth relation to the soil surface under virgin conditions. Also the bands occur often enough in loamy fine sand soils to indicate that the banding phenomenon is the usual rather than the exception in their genesis. Data obtained by fractionation of the < 2µ clay indicate differential movement of the clay fractions in 2 loamy fine sand profiles with iron and silicate clay enriched bands. In a sandy loam profile, no banding of iron and clay or movement of clay size particles was evident. Data from the chemical analyses indicate a very small quantity of bases held in the exchangeable form. Exchangeable base content of the iron band layers was of the order of twice as high as in the interband layers. Exchangeable Ca:Mg ratios were lower in the bands than in the interband layers. Exchangeable Ca:Mg ratios were higher in the profiles studied than those reported for other Gray‐Brown Podzolic and Brunizem soils which have developed from finer textured material. Total nitrogen was higher in the iron‐enriched bands than in the interband layers. In a laboratory experiment, iron bands were produced in a 1‐inch diameter, 4‐foot tube filled with iron containing fine sand by leaching with 0.01 N oxalic acid solution. Though visually evident, the bands were not sufficiently thick to sample for laboratory analysis. The development of bands in the laboratory is considered as additional proof that the bands of iron and clay enrichment observed in the field are the product of profile genesis. Upon drying, the sandy material in the upper part of the leaching tubes was quite strongly cemented.