Geoscience Reference
In-Depth Information
ground becomes so hot from the sun that it chars the roots of plants); and soil if it is
mixed with any part of the said substances,
is e.g. called chalky, as well as
55
Like all other terminological systems the Ancient Mediterranean ones were
made to aid agricultural practice. They are therefore all concerned with combina-
tions of soils and plants
according to other differences as mixed.
”
there is, in fact, no bad soil, only a badly treated one,
writes Columella in one instance, probably slightly overstating his case. Xenophon
was the
—
rst to make clear that there are suitable soils, suitable for a speci
c plant
c circumstances of cultivation.
56
or, more generally, under speci
In the centuries
after him, authors tried to de
ne what makes a soil good and/or suitable. Some
authors re
ned the determination of soil qualities in order to be able to give suit-
ability descriptions which are inter-subjective. Others took into account that plants
will grow optimally at a particular site, but might still be grown elsewhere, thus
developing a plant-relative quality measure.
The Roman authors are most explicit about the methods needed to test a soil for
its quality. They describe the same test which we have encountered already in
China and India, a test for structural stability of soils. After digging a hole into the
ground, one tries to re
ll the hole. If the earth has increased in volume, leaving a
small hill, it is fertile. If the volume has not changed and the hole can be
lled
evenly, the earth is of middle quality. The soil quality is meager if the soil volume
has decreased due to digging and the earth leaves a trough.
57
According to Colu-
mella, this test is not applicable to black soils. Land cover of pristine land has been
important in assessing soil suitability in several of the agricultural civilizations.
Indicator species are named that allow one to distinguish between sweet and saline
grounds, and especially between grounds
t for grain or not. Columella gives a long
list of plants
58
; Pliny remarks generally on the possibility of plant cover as a soil
quality indicator
59
and refers to a list of plants that Cato had already given. Col-
umella, who is generally the most cautious author, warns against relying on plant
cover as the sole indicator.
Like the B
Ivoire, like Ancient Chinese and probably also like the
Aztecs, Roman agriculturalists relied on their senses to determine soil quality.
Nowadays it is known that the typical smell of earth is due to the activity of fungi,
in particular Actinomyces. Fungi play a crucial role in soil biology, and a soil that
exhibits the typical earthly odor is obviously healthy even by modern standards.
Pliny
60
already mentions soil smell as an indicator of overall fecundity, which
according to him is strongest when rain wettens a surface that has dried out, and
also becomes stronger when the soil is worked. Taste was likewise employed. As it
é
t
é
of Cote d
'
55
Varro (
1996
-
1997
).
56
Xenophon (
1992
).
57
Columella (
1982a
), Vergilius
5
(
1987a
).
58
Columella (
1982b
).
59
Plinius Secundus (
1995
).
60
Plinius Secundus (
1994a
).
