GT-0042 · Andisol
Acatenango Andisol
Volcanic ash turned into the soil of the finest coffee.
Soil profile
Tap a horizon to see its details.
O/A0–30 cm
A dark, spongy layer full of fine roots and life. This is where organic matter concentrates.
- Munsell colour
- 10YR 2/2
- Texture
- Loam
Bw130–60 cm
Ash begins to weather into minerals that hold water like a sponge.
- Munsell colour
- 7.5YR 3/3
- Texture
- Clay loam
Bw260–95 cm
Uniform brown colour. Coffee and shade-tree roots reach this deep.
- Munsell colour
- 7.5YR 4/4
- Texture
- Silty clay loam
BC95–125 cm
A transition zone. Barely weathered pumice fragments appear.
- Munsell colour
- 10YR 5/4
- Texture
- Silty clay
C125–150 cm
Nearly intact ash and pumice, the material the whole profile was born from.
- Munsell colour
- 10YR 6/4
- Texture
- Silt loam
Long ago, the volcano threw ash into the sky. The ash fell like a grey blanket and, little by little, rain, roots and tiny creatures turned it into dark soil as soft as chocolate cake. That is why such delicious coffee grows here!
This soil formed from volcanic ash (tephra) deposited over the last 10,000 years. As it weathers, the ash produces very fine minerals that hold a lot of water and organic matter, which is why the surface horizon is so dark and light. Andisols cover Guatemala's volcanic chain and sustain highland coffee growing, but on steep slopes they erode easily if they lose their cover.
Core idea: parent material (ash) and time explain this soil's properties. Suggested 35-minute activity: compare the density of an Andisol clod with a clay clod, by hand and on a scale, then observe how much water each absorbs. Guiding questions: why is it lighter? What happens to this soil on a slope without trees? Links to Natural Sciences, soil-forming factors.
Typic Hapludand developed on Holocene tephra under a udic, isothermic regime. A 30 cm umbric epipedon with 8.4% organic matter and andic properties throughout the solum; CEC falls from 42 to 18 cmol(+)/kg with depth. Moderately acid to neutral reaction (pH 5.8 to 6.8). High phosphate retention, typical of allophanic materials, shapes phosphorus fertiliser management. Moderate erosion risk on 15 to 25° slopes under shade-grown coffee.
- USDA Soil Taxonomy
- Typic Hapludand
- WRB 2022
- Silandic Andosol (Humic)
See the scientific data
Analytical data by horizon
| Horizon | Depth (cm) | Munsell colour | Texture | pH (H₂O) | O.M. % | CEC |
|---|---|---|---|---|---|---|
| O/A | 0–30 | 10YR 2/2 | Loam | 5.8 | 8.4 | 42 |
| Bw1 | 30–60 | 7.5YR 3/3 | Clay loam | 6.1 | 4.2 | 38 |
| Bw2 | 60–95 | 7.5YR 4/4 | Silty clay loam | 6.3 | 2.8 | 34 |
| BC | 95–125 | 10YR 5/4 | Silty clay | 6.5 | 1.4 | 28 |
| C | 125–150 | 10YR 6/4 | Silt loam | 6.8 | 0.6 | 18 |
CEC: cmol(+)/kg
- 5.8O/A
- 6.1Bw1
- 6.3Bw2
- 6.5BC
- 6.8C
- 8.4O/A
- 4.2Bw1
- 2.8Bw2
- 1.4BC
- 0.6C
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