Geoscience Reference
In-Depth Information
5.2 Brief history and soil classifi cation
A
In the United States, soil science and survey
began in the late nineteenth century, primarily
for agricultural purposes, and wet soils were
generally mapped in two categories (quoted
from Whitney 1909, pp. 116-117).
• Muck and peat - These soils are composed
largely of organic matter in various condi-
tions of decay, the muck representing an
advanced stage of change in peat areas. Of
relatively limited extent and poorly drained,
these soils are highly valued for their adapta-
tion to special crops, such as celery, onions,
peppermint and cabbage.
• Swamp, tidal swamp and marsh - Under
these heads are grouped areas covered with
water the greater part of the year and uni t
for agriculture except where drained and
protected from tidal or l uvial overl ow.
When reclaimed, much of this land will
become quite productive.
B
The need for reclamation, namely drainage,
was a recurring theme for productive use of
wetland soils. Furthermore, once drained,
wetland soils were thought to be highly valu-
able for crops and other agriculture (Bonsteel
1912a & b). Management of wetlands for non-
agricultural purposes hardly existed, and the
accepted practice was to drain all such areas
wherever economically feasible and to put
them into agricultural production. Even though
the chemical properties and texture of wetland
soils were not well suited to crop production,
drained wetlands with inputs of chemicals
allowed vast parts of the temperate latitudes
and tropics to be converted to agriculture
(Guthrie 1985). The costs associated with the
constant maintenance of proper drainage, fertil-
ity, and erosion control of wetland soils may
be quite high. Even so, rice is probably the
most ubiquitous crop grown on l oodplain and
coastal wetland soils across Asia (Fig. 5-7).
Meanwhile, sugarcane, soybean, corn, peanut,
cotton, and other forage crops are common
elsewhere including across North and South
America (Guthrie 1985).
Figure 5-1.
A. Weathering of granite along the Baltic
shore, island of Bornholm, Denmark. B. The fragmental
debris, called grus, has accumulated in layered deposits
nearby. Scale pole marked in 20-cm intervals. Photos
by J.S. Aber.
• Reduction - oxygen is depleted leading to
anaerobic conditions for microbes and
chemical reactions. Oxidation of organic
matter slows or is halted.
• Redoximorphic features - mobilization and
removal of ferrous (reduced) iron and depo-
sition of ferric (oxidized) iron as mottles,
streaks, and patches.
