How to examine and sample a soil profile?

Soil is a non-renewable natural resource vital for our existence. Soil produces 98.7% of the calories consumed by humans globally, holds more organic carbon in the surface 3 meters than the atmosphere and vegetation combined, and is home to 59% of the species on Earth, making it critical for global biodiversity (Kopittke et al., 2025). 

Soil Scientists study the soil using the soil profile. Soil profile, the vertical section of the soil from the surface to the bedrock below, is the basic unit of soil examination and sampling. A soil profile consists of soil layers called soil horizons. The characteristics of soil horizons depend on the dominant soil processes. They are influenced by soil-forming factors such as climate, relief (topography), organisms (vegetation, soil organisms, human activities, etc.), parent material (types of rocks), and time (duration of soil formation). 

A soil profile of Faraon clay, developed from limestone, in Baybay, Leyte.

To examine a soil profile, a pit measuring 1m x 1m to a depth of at least 1.5m (or to the bedrock or water table) is excavated. Recent road cuts and landslide faces generally offer good opportunities to examine and sample soil profiles. Soil profiles are examined and described using standard procedures. The global standard reference is the book “Guidelines for Soil Description” (4th edition), published by the Food and Agriculture Organization (FAO) of the United Nations in several languages. The book was co-authored by Reinhold Jahn (Martin Luther University, Germany), H.P. Blume (Kiel University, Germany), Victor B. Asio (Visayas State University, Philippines), Otto Spaargaren (ISRIC, Netherlands), and Peter Schad (Technical University Munich, Germany). 

The Guidelines for Soil Description published by FAO & its authors.

After the soil profile has been evaluated and described, approximately 1 kilogram of soil is collected from each soil horizon for laboratory physical, chemical, mineralogical, and biological analyses. The old and widespread practice is to collect 3 or more subsamples from each horizon and then mix them into a single representative sample for that horizon. 

A better method is the quantitative soil profile sampling method (or the Hohenheim soil profile quantitative sampling method) developed in the 1960s by Ernst Schlichting, the renowned professor and director of the Institute of Soil Science and Site Ecology at the University of Hohenheim, Stuttgart, Germany. The said sampling method was introduced in the influential book “Bodenkundliches Praktikum (Soil Science Practicum)” by Ernst Schlichting and his assistant, Hans-Peter Blume. 

Due to its widespread use in German-speaking countries, the book was revised by his former students, H.P. Blume and Karl Stahr, and published as 2nd edition in 1995. In 2011, the 3rd edition was published and authored by H.P. Blume, K. Stahr, and P. Leinweber. 

H.P. Blume, K. Stahr, and P. Leinweber are now retired professors of soil science at the University of Kiel, University of Hohenheim, and University of Rostock, Germany, respectively. H.P. Blume and K. Stahr were presidents of the German Society of Soil Science.

References

Kopittke, P. M., Harper, S. M., Asio, L. G., Asio, V. B., Batalon, J. T., Batuigas, A. M. T., ... & Sanchez, P. B. (2025). Soil degradation: An integrated model of the causes and drivers. International Soil and Water Conservation Research.

Schlichting, E. and Blume, H.P. (1966). Bodenkundliches Praktikum (Soil Science Practicum). Verlag Parey, Hamburg. 

Schlichting, E. Blume, H.P., and Stahr, K. (1995). Bodenkundliches Praktikum (Soil Science Practicum)(2. Auflage). Verlag Blackwell, Berlin.