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Horizonte B latossolico (SiBCS Cap 2, p 57-59)

Source: R/diagnostics-horizons-sibcs.R
B_latossolico.Rd

The requirements of the book that the data of a profile can show (v0.9.241):

  • (d) texture francoarenosa or finer;

  • (g) cation exchange capacity below 17 cmolc per kg of clay, with no correction for carbon;

  • (e) a molecular ratio SiO2/Al2O3 (Ki) of 2.2 or less, where the sulfuric attack is recorded (sio2_sulfuric_pct, al2o3_sulfuric_pct): a layer with a Ki above 2.20 is no B latossolico (v0.9.243);

  • (h) cerosidade, if present, at most few and weak: a layer with a larger amount or a higher grade is no B latossolico (a range counts by its upper end, the requirement being a maximum);

  • (b) a thickness of 50 cm or more, of the horizon: of the adjoining sub-horizons that meet the other requirements, taken together;

  • it "nao apresenta caracteristicas diagnosticas de horizontes glei, B textural, B nitico e plintico": the layers of a B_textural, of a horizonte glei, of a horizonte plintico and of a B_nitico are no B latossolico. Since v0.9.249 they take out their own layers only: until then the glei and the plinthic horizon were those of WRB (gleyic properties, plinthic horizon), and one of them, or a B nitico, anywhere in the profile voided the B latossolico of the whole profile.

Where the designations are recorded, only B horizons are candidates: the B latossolico is a subsurface horizon below the A. Items (a) structure, (c) rock structure and (f) weatherable minerals are not tested.

Usage

B_latossolico(
  pedon,
  min_thickness = 50,
  max_cec_per_clay = NULL,
  engine = NULL,
  ...
)

Arguments

pedon

A PedonRecord.

min_thickness

Minimum thickness of the horizon, in cm (50).

max_cec_per_clay

CEC per kg clay the horizon must stay below. Defaults to NULL (engine-aware): 17 in soilkey engine (SiBCS Cap 2: "menor que 17 cmolc kg-1 de argila, sem correcao para carbono") or 20 in aqp engine (v0.9.68 regional tolerance for Embrapa lab methodology offset). Strict since v0.9.212: a value of exactly 17 is not latossolic, it is the B incipiente's "17 ou maior".

engine

One of "soilkey" (default) or "aqp"; NULL reads getOption("soilKey.diagnostic_engine").

...

Reserved for future arguments.

Value

A DiagnosticResult recording whether the diagnostic is present, the qualifying layers, and the supporting evidence.

Details

Until v0.9.240 the 50 cm were asked of each layer on its own, so that a B latossolico described as B1, B21 and B22 of 35 cm each was none; and since v0.9.61 a B textural did not exclude it unless its clay films were common or more, on a rule the comments attributed to Cap 18 of the book, which deals with families and series.

In the morphological mode a "Bw" or "Bo" of a tropical profile stands for the B latossolico when the data do not show it.