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t for planting, a strenuous
task, after which organic matter was added to increase fertility. Planting was
sometimes done in holes, which served as sediment traps and collected rain or
irrigation water, as Barbara Williams suggests. Glyphs exist also to describe fal-
lowing and fertilizing the soil with a substance which could probably be nightsoil.
The fertilizing agents comprised
Aztec farmers pulverized tepetate soils to make them
'
refuse
'
, which cannot be identi
ed, nightsoil, bat
dung, organic ash and alluvium. Irrigation canals
lled with mud over time, and this
mud was brought back to the
elds as another form of fertilization. One glyph
suggests that soils were mixed; in particular a woodland soil with high organic
matter content was mixed with clay, a procedure that makes agricultural sense,
although it is not fertilization in the strict sense.
Aztex agriculturalists are most famous for the chinampas, ridges constructed in
swampy areas and shallow lakes from the mud on the bottom mixed with aquatic
vegetation, not unlike the Chinese
elds. These anthrosol garden beds were
highly fertile and supported the population concentrated in the Tenochititlan area
before Europeans conquered their state. Chinampas could be used for continuous
cropping, with seed beds (similar to those used in rice agriculture) saving space and
time. In contrast to these wetlands, drier soils had to be irrigated, and a multitude of
words exist in Nahuatl to describe irrigation related activities, implements and
constructions.
Salinization of soils was a problem in the northern part of the Basin of Mexico,
where salt production took place on the shores of saline lakes. Problems with
salinization increased after conquest. Farmers apparently had
oating
gured out that saline
soil is unproductive, but that the salt can be dissolved with freshwater. The farmers
of the early 19th century are reported to have dumped soil which had become saline
due to chinampas cultivation into Lake Texcoco, digging out fresh soil from
another spot. They would come back to the dumping spot after a while, when the
lake water had dissolved the unwanted sodium chloride, again ladling up the
cleaned soil for their gardens.
Taxation seems to have been dependent on soil quality, so soil knowledge was
not con
ned to farmers, but had to be possessed also by administrators. Like in all
other agricultural societies, soil knowledge was an integral part of everyday life, and
had cultic, medicinal and technical aspects. Only a very small part of this knowledge
system can be reconstructed from the scarce evidence left after conquest.
The Aztecs,
like so many other civilizations, built
irrigation networks and
agricultural
terraces,
thereby in
uencing pedogenesis, erosion and, of course,
fertility.
Terrace building is not con
ned to the Aztec peoples. In Middle America alone,
three common types of terraces can be distinguished. Firstly, one
eld
terraces, which span gentle hillsides and do not change much the angle of the slope.
They are built to retain soil behind the terrace wall, making it deeper, and to collect
moisture. These terraces also retain nutrients by retaining topsoil, which might be
washed away by rains. The second type of terraces are bench terraces, which are
made to produce leveled platforms along the contour. In Middle America, these
terraces were usually irrigated. Cross-channel terraces were built by placing check
nds sloping-
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