Geoscience Reference
In-Depth Information
soils over only 200 ha. Peasant farmers today apply four classes, and modern tax-
onomy ascribes
ve soil phases to the soils of this area. The 104 variants probably
represent 18 taxa and three separate class levels. Classi
cation of soils was done in a
multi-dimensional system. One important denominator was grain size, stony, sandy,
clayey, silty and the volcanic tepetate soil particular to the area were distinguished,
each of them is described in some detail. The distinction between material that could
be crushed in the hand and that which could not, a main difference in the classi
-
cation system, is an experimentally derived denominator for Aztec soil taxa.
Tepetate (best rendered as
) is a hardened volcanic tuff, which can be
found on the surface only after erosion has taken place. It is considered as marginal
land, but cultivable, if pulverized. A depiction of a man beating up tepetate soil is
preserved in a 16th century description made by the Franciscan friar Bernardino de
Sahag
'
soft rock
'
n, one of the main sources for Aztec agriculture. Loess soils, the result of
Pleistocene wind erosion, were denoted by a special glyph, which was described as
“
ú
that which swirls up, that which sweeps up
”
, possibly showing knowledge about
the Aeolian origin of these soils, but de
nitely about their inclination to wind ero-
sion. Soil classes between sand and clay, commonly called loams in English, are not
distinguished by special names, but rather by combining the names of the two
constituents, at least such conjunctures are used by Nahuatl speakers today. Each of
the main soil classes has several sub-classes, such as sandy clay or gravelly clay,
bother denoted by the combination of glyphs. Color does not play an important role
in the taxonomy of the Aztecs, but topography does, the soil on slopes has its own
name. Woodland and reedy soils are both characterized by their content of organic
matter, showing an understanding of its centrality for cultivation. The soil taxonomy
comprises a speci
c word for humus, tlazollali. It was understood to come from the
compost pile and to turn into fertile soil. Another term which bears witness to Aztec
understanding of soils as dynamic entities is a speci
c word for alluvial soils, those
that are the result of
uvial sediment deposition (atoctli), and again, several sub-
classes for this soil type are denoted. Moisture retention by soils, a particularly
important feature in arid or semi-arid lands such as those of the Aztecs, was included
in the nomenclature system, with two names for such soils. Even a notion for
anthrosols, soils which are co-created by humans, has come down to us in Nahuatl:
callalli denotes a soil where a house has been, it is considered to be fertile.
All classi
cation systems found in agricultural societies also include a concept of
infertile soils. The Nahuatl word for them is tequixquitlalli, described as
salty,
bitter, corrosive, leached of its salt, unwanted, undesirable, waste and disregarded
'
,
the latter two could hint at soils which have become infertile by bad agricultural
practices. Tlalzolli is another word for bad soil, which will not support any growth,
because it is worn out.
Unfortunately, we lack information as to soil tests in Aztec agriculture. They
must have had some means of determining e.g. salty and bitter soil, but the extant
sources do not give information on such tests apart from the knowledge of two
grasses as indicator plants for tequixquitlalli and ashen soil (nextlallili), two infertile
soil types to be avoided. While these soils were considered un
'
t for agriculture,
they played a role in indigenous medicine.
