"Horizonate" this soil profile!

By Paul Tietz, Graduate Student, University of Idaho Gordon Rees, Associate Professor, Cal Poly–San Luis Obispo Damon LeMaster, Graduate Student, West Virginia University and Jaclyn Fiola, Assistant Professor, Delaware Valley University Department of Soils and Environmental Science

July 30, 2026

At the Fifth International Soil Judging Contest, Team USA members compete in the group judging contest event. From left: Zie Goodman, Holden Mrizek, Sinclair Anderson (front), Cole Chapman (back). Photos courtesy of Paul Tietz/Team USA Soil Judging.

Have some soil science knowledge? Let’s see how well you’d do during a soil judging contest. Using photos and data from the Fifth International Soil Judging Contest, try naming the soil horizons from three different practice profiles.

At the Fifth International Soil Judging Contest, top soil science students from universities across the world were brought together in China to develop skills in soil description and classification. Participants used practice soil pits to test their knowledge on two soil classification systems—the World Reference Base (WRB) and USDA Soil Taxonomy—before teams competed for top honors.

Team USA won big. How do you think you would do? Here, we’ve submitted some photos of select practice pits and the surrounding landscapes, and we provided some additional data to see if you, too, could go toe to toe with the world’s best! Look at these three soil profiles and see if you can label each soil layer, based off the World Reference Base (WRB) descriptions for soil horizons. Answers at the end!

Profile 1

This first practice pit has 6 horizons, reaching a depth of 130 cm. Some extra details include:

Parent material: Alluvium.
Landscape: Floodplain bottom.
Notes: Surface cracks < 2 cm present, flooding/ponding occurs.
An image of Soil Profile 1 and a close-up view of soil from the practice pit.

Practice Pit 1
Horizon	Depth (cm)	Distinctness	% OC	pH	CEC	% Base saturation	Texture	Structure type
1	12	A	1.42	7.4	22.9	76.8	Silty clay	Cloddy
2	26	G	1.20	7.4	23.1	82.7	Silty clay	Prismatic
3	53	C	0.88	7.1	22.0	87.1	Silty clay loam	Prismatic
4	80	C	0.80	7.4	19.2	85.4	Silty clay	Stratified
5	105	G	0.85	7.4	18.5	81.3	Silty clay loam	Stratified
6	130+	--	0.80	7.4	18.0	80.2	Silty clay loam	Stratified

Horizon	Structure grade	Color hue	Color value	Color chroma	Effervescence class	Redox depletions	Redox concentrations
1	Structureless	10YR	3	3	--	--	Few
2	Moderate	10YR	3	3	--	--	Few
3	Moderate	10YR	3	3	Slightly	--	Common
4	Structureless	10YR	3	4	Slightly	Common	Common
5	Structureless	10YR	3	4	Slightly	Common	Common
6	Structureless	10YR	3	4	Slightly	Common	Common

Some of the landscape surrounding Practice Pit 1.

Profile 2

The second practice pit has 6 horizons, reaching a depth of 92 cm. Some extra details include:

Parent material: Alluvium.
Landscape: Alluvial fan floodplain in a crop field.
Notes: No surface cracks, flooding/ponding occurs, human artifacts in first horizon.

Practice Pit 2
Horizon	Depth (cm)	Distinctness	% OC	pH	CEC	% Base saturation	Texture	Structure type
1	11	Clear	1.33	6.7	16.1	84.0	Silt loam	Granular
2	25	Clear	1.04	7.1	15.6	87.4	Silt loam	Subangular blocky
3	35	Clear	0.80	7.5	14.9	90.1	Silt loam	Subangular blocky
4	59	Clear	0.43	7.6	11.8	93.7	Clay loam	Subangular blocky
5	75	Abrupt	0.34	7.7	7.7	96.0	Sandy clay loam	Subangular blocky
6	92	Clear	0.30	7.7	7.7	97.0	Sandy loam	Stratified

Horizon	Structure grade	Color hue	Color value	Color chroma	Effervescence class	Redox depletions	Redox concentrations
1	Moderate	10YR	3	3	--	--	Few
2	Moderate	10YR	3	3	--	Common	Common
3	Moderate	10YR	4	2	--	Many	Many
4	Moderate	10YR	4	2	--	Many	Many
5	Weak	10YR	4	2	--	Many	Many
6	Structureless	7.5YR	4	2	--	Many	Many

Some of the landscape surrounding Practice Pit 2.

Profile 3

The last practice pit has 6 horizons, reaching a depth of 130 cm. Some extra details include:

Parent materials: Human-transported over eolian.
Landscape: Anthropogenic backslope in a tea plantation.
Notes: No surface cracks, no flooding/ponding, human artifacts in the first two horizons.

Practice Pit 3
Horizon	Depth (cm)	Distinctness	% OC	pH	CEC	% Base saturation	Texture	Structure type
1	9	Clear	0.54	7.0	9.9	66.1	Silt loam	Subangular blocky
2	34	Clear	0.31	7.0	8.4	78.1	Silt loam	Subangular blocky
3	57	Gradual	0.31	6.7	12.5	81.0	Silt loam	Subangular blocky
4	83	Clear	0.24	6.6	13.5	88.1	Silty clay loam	Subangular blocky
5	103	Gradual	0.17	6.5	14.0	89.5	Silty clay loam	Subangular blocky
6	130+	--	0.10	6.4	15.1	90.1	Silty clay	Subangular blocky

Horizon	Structure grade	Color hue	Color value	Color chroma	Effervescence class	Redox depletions	Redox concentrations
1	Moderate	10YR	4	4	--	--	--
2	Moderate	7.5YR	4	4	--	Common	Common
3	Moderate	7.5YR	4	3	--	Many	Common
4	Moderate	7.5YR	4	3	--	Many	Common
5	Moderate	7.5YR	3	4	--	Many	Many
6	Moderate	7.5YR	3	4	--	Many	Many

Some of the landscape surrounding Practice Pit 3, along with a color value chart.

How did you do?

It's harder than you'd think! Congratulations again to all the winners for their hard work and incredible professional development. Check out the article about Team USA here, and make sure to look at the answer key below.

Answers Team USA More soil judging Back to issue

Text © . The authors. CC BY-NC-ND 4.0. Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.