Enrichment · Cultural Studies

Sand, silt, clay.
Name the soil.

Type the percentages, enter your jar test readings or work through the feel key, and the page names the USDA texture class, plots it on the triangle and says what it means for a garden bed.

Open the calculatorWhat you get

The calculator

The worked example is a made-up home garden with four samples. Everything saves in this browser as you go.

Loading the calculator. If nothing appears, turn on JavaScript.

What you get

Enrichment · Cultural StudiesFree

What you finish with
The texture class of each soil sample, plotted on the USDA triangle, with what it means for drainage, watering and digging; a log of samples you can print or open in a spreadsheet.
Who it is for
Students in earth science, environmental science and agriculture classes, school and home gardeners, garden clubs and families doing a soil project.
Format
Browser tool with four tabs: percentages, a jar test calculator, a texture-by-feel key and a sample log. Prints the log with the triangle; downloads a spreadsheet (.csv) and a file you can import later.
Access
Free. No account or sign-in. It runs in your web browser on a phone, tablet or computer. Everything you type stays in this browser and is saved there as you go; nothing is sent to Caveat.
Where it lives
The Cultural Studies space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Load the worked example to see four samples from one garden, or start blank.
  2. If you have numbers from a lab report, type sand, silt and clay. If not, do a jar test and enter the three heights, or use the feel key with a handful of moist soil.
  3. Read the class and the garden notes. Tap the triangle to see how close a sample sits to the next class.
  4. Name the sample and save it to the log. Repeat for each bed or site.
  5. Print the log or download the spreadsheet for a lab report or garden plan.

Open the calculator

How the class is worked out

The same twelve classes soil scientists use.

The triangle

Every mineral soil is some mix of sand (0.05 to 2 mm), silt (0.002 to 0.05 mm) and clay (under 0.002 mm). The USDA triangle splits all possible mixes into twelve texture classes. This page uses the published class boundaries, for example: loam is 7 to 27% clay, 28 to 50% silt and 52% sand or less. A point exactly on a boundary goes to the class the USDA rule assigns it.

Percentages here are of the fine earth only: gravel and stones are removed first, and organic matter is not counted.

How accurate each method is

A lab report (hydrometer or pipette method) gives the most reliable numbers. A jar test is a good classroom estimate: layers settle unevenly, some clay stays suspended and organic matter floats, so treat the result as a range of a class or two. Texture by feel, using the ball-and-ribbon key from Thien (1979), takes practice; check yourself against a jar test or a sample with known numbers.

The garden notes describe tendencies. Structure, organic matter and compaction change how any soil behaves.

Sources

  1. Soil Science Division Staff (2017). Soil Survey Manual, USDA Handbook 18. U.S. Department of Agriculture, Natural Resources Conservation Service. Particle-size classes and the soil texture triangle.
  2. USDA Natural Resources Conservation Service. Soil texture calculator and the definitions of the twelve texture classes.
  3. Thien, S. J. (1979). A flow diagram for teaching texture-by-feel analysis. Journal of Agronomic Education, 8, 54–55.
  4. Brady, N. C., and Weil, R. R. (2017). The Nature and Properties of Soils (15th ed.). Pearson. Texture and its effects on water, air and nutrients.

The example samples are made up. Jar test and feel results are estimates; for decisions about drainage, construction or contaminated ground, use a laboratory test. Support: team@caveatacademic.com.