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131 Horizon designation

Dictionary: d_hori_disc

The horizon designation is a combination of several symbols:

  1. Discontinuity: A number that gives information about discontinuities, i.e. the number of materials in which the soil has formed, e.g. 1 for first material. This number is stored in the field HORIZON_DISCONTINUITY.

  2. Master horizon: One or several capital letters that designate the type of master horizon (e.g. A, B, E, C) or transitional horizon (e.g. ‘AB’). These letters are stored in the field HORIZON_MASTER. Common syntax and content-wise checks run during data submission to ensure data quality (more details in section below).

  3. Subordinate symbol: Lowercase letters that designate subordinate symbol of the horizon, e.g. ‘h’. These letters are stored in the field HORIZON_SUBORDINATE. Common syntax and content-wise checks run during data submission to ensure data quality (more details in section below).

  4. Vertical subdivisions: The number of vertical subdivisions, e.g. 1 for one vertical subdivision, is stored in the field HORIZON_VERTICAL.

Tests for master horizon

Based on the FAO guidelines 2006*, the tests check if following rules are respected:

  • For the master horizon’s designation following symbols are valid: A, B, C, E, H, O, R, which can be freely combined either in a series or separated by /. In addition, the symbols I, L, W can also be used, but as single letters only. Above these, following combinations are also valid: OL, OF, OFH, OLF, HF, HM and HS.
  • Always use capital letters and remove blank spaces.
  • A virgule (/) at the end without a letter hereinafter will rise an error.

“The master horizon symbol that is given first designates the kind of horizon whose properties dominate the transitional horizon. For example, an AB horizon has characteristics of both an overlying A horizon and an underlying B horizon, but it is more like the A than like the B. […] Horizons in which distinct parts have recognizable properties of two kinds of master horizons are indicated as above, but the two capital letters are separated by a virgule (/), such as E/B, B/E, B/C and C/R. Commonly, most of the individual parts of one of the components are surrounded by the other.” (FAO guidelines 2006*)

Tests for subordinate horizon

Based on the FAO guidelines 2006*, the tests check if following rules are respected:

  • In case of mineral soils, following symbols are valid: a, b, c, d, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z. This includes soils having a master horizon different than O or H, or otherwise in case of organic soils having a separated mineral part in the master horizon (indicated by /).
  • In case of organic soils, following symbols are valid: a, c, d, e, f, g, i, j, k, l, m, n, o, p, q, r, u, v, y, z, @. This includes soils having an O- or H-master horizon and also having no separated mineral part in it (indicated by /).
  • Always use lowercase letters and remove blank spaces.
  • Double letters one after another will rise an error

* Guidelines for soil description, Fourth edition, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, Rome, 2006 (https://www.fao.org/3/a0541e/a0541e.pdf, 27.04.2022)