INTRODUCTION
In the early versions of Soil Taxonomy micromorphology held a more significant place than it does now. One has only to read the descriptions of the spodic and argillic horizons in the 7th Approximation and the 1996 Keys to Soil Taxonomy to see the change. Two reasons for the change follow. First of all W.L. Kubiena, Roy Brewer, J.R. sleeman, along with others (A. Jongerius and R.W. Fitzpatrick for example) were developing the tools and terms for description of soil fabrics during the time Soil Taxonomy was developing. Others like John Cady and Klaus Flach were conversant in both endeavors and thus were in position to influence the direction of Soil Taxonomy toward micromorphic techniques. Secondly with time it became more and more apparent that it was more practical to classify soils based on properties that could be observed in the field. Only hand specimen- verifiable microfabric features survived the changes in Soil Taxonomy. With experience soil morphologists are able to 'identify' soil fabrics in hand specimen as well as in thin section. Using this approach fewer profiles were reclassified later when laboratory data became available.

However, there are still a few Soil Taxonomy criteria that require microfabric description. There are still other diagnostic horizons that may be identified using microfabric descriptions. Finally there are some general relationships between the soil fabrics and kinds of soil orders. In the case of Spodosols the range in kinds of fabrics is narrow, whereas in Inceptisols and Entisols the range is broad. In the slides I will show at the conference I will present some of teh observations Dr. Douglas Wysocki and I have made relating soil fabrics and soil taxa.

DIAGNOSTIC HORIZONS THAT HAVE SOME MICROFABRIC CRITERIA

1. Mollic epipedon--Absence of fine stratification.
2. Umbric epipedon--Absence of fine stratification.
3. ochric epipedon--Absence of fine stratification and absence of rock structure.
4. Plaggen epipedon--Presence of artifacts.
5. Agric horizon--Specified % of area of mixtures of organic matter, silt, and clay.
6. Argillic or natric horizon--1% cross sectional area of clay skins in specific situations. Some clay skins in the lowest part of the horizon in certain conditions.
7. Calcic horizon--5% or more by volume of identifiable secondary carbonates under certain conditions.
8. Duripan--Presence of opal or other forms of silica as a cement.
9. Oxic horizon--Less than 5% of horizon is made up of rock structure or sesquioxide coated lithorelics.

DIAGNOSTIC HORIZONS THAT INCLUDE MICROFABRIC DESCRIPTION AS SUPPLEMENTARY (NON-DIAGNOSTIC) CRITERIA

1. Anthropic epipedon--Presence of bones, shells, man made objects, and or evidence of disturbance.
2. Histic epipedon--Presence of sphagnum fibers.
3. Albic horizon--Absence of unaltered parent materials.
4. Cambic horizon--Absence of cementation and presence of soil structure, evidence of alteration, juvenile, or development toward argillic, kandic, oxic, or spodic horizons.
5. Fragipan--Evidence of pedogenesis such as silt flow, argillans, or soil structure.
6. Glossic horizon--Presence of both albic materials and ped remnants.
7. Kandic horizon--Absence of fine stratification.
8. Sombric horizon--Presence of organic matter on ped faces or in soil pores rather than in the soil matrix.
9. Spodic horizon--Presence of silt or sand size pellets and cracked coatings of spodic materials on sands.

CONCLUSIONS
the most effective soil scientists are able to see across the scale gap between morphologic features in hand specimen and the features as observed in thin section or with the scanning electron microscope. Such knowledge comes through experience. Some soil scientists have preferred to describe the soil features using descriptive sentences. Others prefer well accepted therms. The terms' approach seems best suited to storage and retrieval of information and statistical analysis of data.

This page (http://www.ces.ncsu.edu/plymouth/programs/diagnostic.html) created by
Vera MacConnell, Research Technician, I on March 9, 1998.
Last Updated on March 9, 1998.