Agriculture Reference
In-Depth Information
by indigenous people:
ÑTO RESCUE FOR HUMAN SOCIETY THE NATIVE VALUES OF
RURAL LIFE.Ò
The Bureau of Soils in the United States recognized the need to communicate soil science to
indigenous people with regard to how it interacted with various crops and management practices,
and produced practical reports that Ñdeal with everyday problems (of the indigenous farmer) and
are written with as little use of technical terms as possibleÒ (Whitney, 1905, p. 11).
While concerns for what a soil
for human endeavors to obtain sustenance dominated soil
mapping efforts in the United States, soil classiÝcation efforts sought to establish what
does
a natural
entity worthy of independent recognition. Perhaps the infant science of soil reached a status of
scientiÝc adulthood, independent of its geologic parent, with the widely read treatise of Jenny
(1941). The expression S =
is
(cl, pm, r, o, t) served to identify soil (S) as a distinct natural entity,
but identiÝed it in terms of climate (cl), parent material (pm), relief (r), organisms (o), and time
(t). Jenny (1941) concluded that the requirements necessary for establishing correlation of soil
formation factors to soil properties were possible only under controlled experimental conditions,
and in the Ýeld we must be satisÝed with approximations and general trends. When the soil-forming
factors are considered over time, each becomes a criterion that cannot be measured. Climate consists
of weather averages, but one extreme weather event may leave an indelible imprint in a soil. Parent
material may be the material below the soil, but incremental aerosol additions made to the soil are
often not represented. Tectonic movements and erosion alter relief. Organisms in and on the soil
change with natural succession, Ýre, wind, and human intervention. Jenny (1941) reasoned that the
use of soil-forming factors in classiÝcation was handicapped by an inability to determine the exact
composition of the initial (parent material) and the Ýnal (mature soil) stages of soil development.
However, in view of the many correlations between soil properties and soil-forming factors, many
soil classiÝcations identiÝed soils by association with soil-forming factors, i.e., forest soils, prairie
soils, tropical soils, tundra soils, etc.
f
PHILOSOPHY OF SELECTING A UNIT OF SOIL TO CLASSIFY
Cursory observation of a soil reveals a vertical arrangement of soil components that change,
often gradually, as one traverses the landscape. Our understanding of soil is limited without the
use of chemical, mineralogical, biological, and physical quantiÝcation of soil samples. Soil can be
dismembered, sampled, and autopsied, but only if we know where each soil sample is located
within a body of soil do the analyses help us understand both what a soil is and what a soil does.
IdentiÝcation of the depth and vertical arrangement of a soilÔs component parts through several
degrees of sophistication, i.e., topsoil, subsoil, generic horizon nomenclature, and diagnostic hori-
zons, is necessary in all attempts to classify soil.
Perhaps no single problem has plagued soil classiÝcation more than the identiÝcation of the
spatial boundaries of a soil individual on the landscape that is to be sampled for study and used
as a unit of classiÝcation. As soil science struggled to claim adulthood as an independent science,
a basis of identifying a soil individual suitable for classiÝcation was at the root of many
philosophies. Soil classiÝcation is closely allied with soil mapping, and most practitioners
intertwined pragmatic realities of mapping into their philosophies of identifying an appropriate
volume of soil for classiÝcation.
From the inception of soil surveys in the United States, three categories were employed in
classifying soils in the Ýeld: series, type, and phase. Series names were place names of cities,
towns, etc. in the area where the soil was Ýrst deÝned. Type identiÝed the texture of the surface
horizon, and phase referred to slope, rockiness, and other features of the area being identiÝed. The
grouping of soils into categories above series was not discussed in the 1937
Soil Survey Manual
(Kellogg, 1937). At that time, a series was deÝned as Ña group of soils having genetic horizons
similar as to differentiating characteristics and arrangement in the soil proÝle, and developed from
