Possible differences in soil characteristics between ortstein and nonortstein Spodosols were studied. Organic C, fine particles (silt plus clay), and extractable Al by dithionite‐citrate, pyrophosphate, acid NH4 oxalate, and NaOH were all higher in Bh than other horizons, except silt plus clay contents in Btg horizons of the St. Lucie County soils. While dithionite‐citrate‐extractable Si was higher at the surface, larger amounts of Fe seemed to occur in lower horizons. Both contents were much lower than extractable Al with the exception of Si in the A and E horizons. Quartz, gibbsite, kaolinite, and hydroxy‐Al interlayered vermiculite were dominant clay‐size minerals. In general, no consistent differences were found in soil properties between the paired ortstein and nonortstein Spodosols except that the ortstein horizons contained more clay and more extractable Al. The cementing materials were shown to dissolve in reagents commonly used for Al and Fe extractions. The dithionite‐citrate reagent was the most effective extractant. The amounts of extractable Al and Fe by dithionite‐citrate, acidic oxalate, and NaOH were small after the ortstein samples were treated with pyrophosphate. These findings suggested that Al in the cementing materials was likely in organic complex form. Ratios of pyrophosphate‐extractable Al to oxalate‐extractable Al and the percentage of maximum Al‐organic complexes supported this assumption. Higher fulvic‐C contents and higher fulvic‐C to humic‐C ratios in ortstein than in nonortstein spodic horizons indicated the complex probably was an Al‐fulvate form.

Five pairs of ortstein and nonortstein spodic horizons of Haplaquods were studied in an attempt to identify the nature of cementing materials. The ortstein horizons had significantly larger amounts of dithionite‐citrate‐extractable Al, significantly higher silt plus clay contents, and significantly higher bulk density values than did nonortstein spodic horizons. Moist and air‐dried ortstein samples had similar shear strengths, but the strength significantly decreased by 14 to 82% for oven‐dried samples. The strength had a significant correlation with the dithionite‐citrate‐extractable Al. Energy‐dispersive spectra showed that Si and Al were major constituents of both ortstein and nonortstein samples. Ortstein samples had stronger Al peaks, however. More cementing materials were observed in the ortstein than nonortstein samples in scanning electron micrographs. These cementing materials consisted of gel‐like substances and fine particles. Cracks in dry gel‐like substances between coarse particles were also observed. Electron‐dot pictures revealed that the gel‐like substances were Al‐dominated.