Soil surveys: A window to the subsurface

Soils and underlying parent materials form a continuous system we must understand and manage in total. Numerous concerns (e.g., water quality, on-site waste disposal, landfill placement, and nutrient or pesticide movement) require an integrated knowledge and understanding of soil, the soil-to-substratum transition, and the deeper substratum. Soil C-horizons can exceed the thickness of the overlying A and B-horizons and contain unique morphological properties. The subsolum including C-horizons receives less descriptive emphasis than upper soil horizons. Soil scientists map and classify soils mainly on A and B-horizon properties. Soil forming and hydrologic processes that impart morphological features, however, extend considerably below these horizons. Precise adherence to Soil Taxonomy places an arbitrary constraint on field observations at 2 m. Soil scientists routinely observe C and R horizons and deeper underlying substrata in gravel pits, road cuts, barrow pits, foundation excavations, and drill cores, but provide less documentation than for upper horizons. Parent material and stratigraphy need more consideration in soil map unit design and delineation. Field observations by soil scientists below 2 m are crucial for understanding the subsolum (i.e., the morphology of, and relationships of solum to substratum). Soil surveys can convey concise and more descriptive soil-to-substrata information with little added effort or resources. Soil surveys can accomplish this end by use of block diagrams, parent material maps, and geomorphic maps that include both pedostratigraphic and lithostratigraphic detail. Soil surveys must develop soil and map unit descriptions linked to measured sections and named stratigraphic units, and describe and analyze soils and parent materials to greater depths (\u3e2 m). We use case examples to demonstrate these concepts. Soil-to-substrata documentation and presentation conveys crucial information to soil survey users. Soil-to-substrata relationships identified and recorded during a soil survey create a knowledge window to the subsurface

Relict periglacial soils on Quaternary terraces in the central Ebro Basin (NE Spain)

Pedofeatures associated with ancient cold climatic conditions have been recognized in soils on terraces in the Monegros area (central Ebro Basin, Spain), at a latitude of 41°49′N and an altitude of 300 m a.s.l. Eleven soil profiles were described on fluvial deposits corresponding to the most extensive terrace (T5) of the Alcanadre River, Middle Pleistocene in age (MIS8–MIS7). Each soil horizon was sampled for physical, chemical, mineralogical and micromorphological analyses. Macromorphological features related to pedocryogenic processes were described: involutions, jacked stones, shattered stones, detached and vertically oriented carbonatic pendents, fragmented carbonatic crusts, laminar microstructures, succitic fabric, silt cappings on rock fragments and aggregates, and irregular, broken, discontinuous and deformed gravel and sandy pockets. Accumulations of Fe–Mn oxides, dissolution features on the surface of carbonatic stones, and calcitic accumulations were identified related to vadose–phreatic conditions. The observed periglacial features developed under cold environmental conditions in exceptional geomorphic and hydrological conditions. This soil information may have potential implications in studies of paleoclimate in the Ebro Valley as well as in other Mediterranean areas

Comparison of Field Measured Soil Absorption Field Loading Rates and Loading Rates Estimated from Soil Morphologic Properties

Concerns from local health departments regarding premature septic system failure (less than 1 year from installation) has led to an investigation of septic system soil absorption field design parameters in northeast Indiana. The objective of this study was to compare the loading rate based on field measured saturated hydraulic conductivity (LRm) across a toposequence to the estimated allowable loading rate (LRe) based on soil morphological properties. Saturated hydraulic conductivity measurements were determined by a compact constant-head permeameter at five landscape positions, at four depths (surface horizon, upper argillic horizon, transition zone between the argillic horizon and till parent material, and till). Results showed that for all depths, the LRm was smaller than LRe. Results from this study suggest that the current method of using soil morphological properties to determine the loading rate may overestimate the ability of the soil to properly disperse septic system effluent