Concepts of soil description and the approach to soil micromorphology have changed through the years as our knowledge base has grown and developed. Thus, definitions as used in this text may be different than used or outlined elsewhere. It is important, however, to stress that the definitions listed here are basic to understanding the full context of this handbook.

FABRIC: This term has been used in several ways by different investigators. Thus, there is no generally accepted definition for soil fabric. The following definitions will be used:

Soil Fabric deals with the totoal organization of a soil, expressed by the spatial arrangement of soil constituents (solid, liquid and gaseous), their shape, size and frequency, considered from a configurational, functional and genetic viewpoint.
A Pattern of soil constituents is concerned with the spatial arrangement of solid soil constituents and associated voids.
A Fabric Unit is a part of the soil material, homogeneous at the scale of observation and for the method of observation used. Several identical fabric units may occur in a soil material.
A Partial Fabric of a soil material comprises all fabric units that are identical at the scale of observation and for the method of observation used.

STRUCTURE: As with fabric, there have been many definitions over the years, some even conflicting with each other. The following definition of structure is applied to both aggregated and non- aggregated material.

Soil Structure is concerned with the size, shape, and arrangement of primary particles and voids in both aggregated and non-aggreagated material and the size, shape and arrangement of any aggregates present. Using this concept, no material is described as structureless.

c/f RATIO CONCEPT: the c/f ratio (coarse verses fine) is used in this handbook. This is a floating size limit between coarse and fine, to be determined for each individual case, and places no limitations on the natrue or complexity of the particles involoved. As such, this system is not restricted to the fabric of the matrix, but applies as well to the description of fabrics of higher order (e.g. arrangement of pedofeatures oro microstructure). The c/f concept is applied to the description of related distributions between coarse and fine elements. The fabric of the groundmass is partly dependent upon the proportion of fine material present. This can be quantitatively determined by point-count analysis or other optical techniques. More than one c/f ratio can be given if the groundmass contains particles belonging to clearly separated size classes, e.g. c/f 4 mm represents for a given section the ratio between grains coarser and finer than 4 mm. Although the boundary between coarse and fine material is flexible the boundary should, if possible, bne selected to coincide with internationally accepted limits used in particle size analysis.

BASIC COMPONENTS: This term is introduced to describe the simplest units (e.g. quartz grains, clay minerals) in a thin section. These constitute the building blocks of the micromass, groundmass, pedofeatures, struture and fabric. They are the particles that are inherited or the alteration of inherited materials.

Basic Components of soils are thus the individual particles that can be resolved with the optical microscope together with the fine material that is unresolvable into discrete individuals. These componets form the building blocks of more complex orgainizations of the soil material.

GROUNDMASS AND MICROMASS: The fine and coarse material which constitutes the partial fabric of the soil generally unaffected by pedological features.

Groundmass is a general term used for the coarse and fine material which forms the base material of the soil, other than that in pedological features except in the following two cases: (1) wherer pedofeatures have arisen through impregnation of the groundmass and the groundmass is still evident; (2) on the rather different level, when making a detailed description of a pedofeature, it is sometimes convenient to refer to the base material of the pedofeature as groundmass.
Micromass is a general term for the finer material in the groundmass.

PEDOFEATURES: discrete fabric units present in soil materials recognizable from an adjacent material by a differene in one or more components.

This page (http://www.ces.ncsu.edu/plymouth/programs/basic.html) created by
Vera MacConnell, Research Technician, I on January 23, 1998.
Last Updated on January 23, 1998.