Low temperature ashing was used to determine the organic matter content of soils by weight loss. This technique utilizes oxygen excited by radiofrequency energy to effect oxidation at relatively low temperatures. Ashing at 375C was used for samples high in organic matter. Corrections were applied for weight loss of inorganic constituents and for incomplete oxidation of organic matter. The following regression equation was developed to convert organic carbon percent to organic matter percent in Pennsylvania surface soils: Percent organic matter = 0.35 + 1.80 X percent organic carbon.
Soil columns from two Typic Glossoboralfs were dissected to separate albic tongues and argillic B horizon material. Tongues and B horizon material have similar coarse/fine (50‐20µ/20‐2µ) silt ratios in the upper B horizon indicating that tongues could have been formed in place by eluviation of clay from certain zones of the B horizon.Lower in the B horizon the tongues consistently have different coarse/fine silt ratios than does adjacent B horizon material. Mineralogical analysis of silts gave no indication of differential weathering of quartz, alkali feldspars, or mica which together make up 85 to 90% of the fine silt (20‐2µ). The particle‐size distribution of silts in the lower albic tongues is taken to indicate that translocation of silts and sands has been involved in the formation of these tongues.Higher proportions of quartz, feldspars and mica in the coarse clay (2‐.2µ) of upper albic tongues indicate that montmorillonite, vermiculite, pedogenic chlorite and kaolinite have been preferentially removed. This, and the mineralogical similarity of fine clay (<0.2µ) between eluvial and illuvial zones, indicate that clay translocation in these soils is accomplished primarily by movement of clay particles in suspension without appreciable dissolution of crystal structures.Spodic horizons have begun to form in the albic horizons of some Glossoboralfs of the study area and Spodosols are common in coarser parent materials. Processes of illuviation inferred from this investigation, however are greatly different from those generally considered typical of Spodosols.
Bleached prism faces are a common feature of soil fragipan horizons. Particle size and chemical and clay mineralogy data indicate these zones are areas of accumulation of material from horizons above. The data also indicates that two processes are active in the movement of material into the prism face area. These processes result in bimodal distribution of particle sizes in the prism face areas. The exact nature of the processes is unclear and may involve both deposition and some stripping.
Soils sampled for laboratory characterization in Pennsylvania were separated into those profiles with fragipans and those without fragipans to determine statistically the soil properties consistently related to fragipan occurrence. Fragipans occurred in the following five parent material groups: aeolium, fluvium, lacustrine deposits, glacial till, and colluvium. Comparisons were made with horizons from comparable depths from nonfragic soils in these same parent material groups, except for colluvial soils, which in every case contained fragipans. Data were analyzed from 773 samples from 254 soil profiles. Fragipan bulk densities of the <2‐mm material were significantly higher at the 1% level than nonfragipan horizons within till and fluvial parent materials, but were not significantly different within aeolian and lacustrine deposits. Multiple regression analyses using 16 soil variables indicated no relationships between these variables and bulk density. Plots of soil textures showed clustering of fragipan samples in loam and silt loam textural classes, whereas nonfragipan samples were more widely spread over other textural classes. Fragipans had significantly lower organic carbon, lower Ca:Mg ratios, and higher mean base saturations with less alteration of illite to vermiculite than nonfragipan horizons. Chemical and mineralogical data indicate that fragipans are less leached and less weathered than comparable nonfragipan horizons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.