1) What is soil?
The unconsolidated mineral or organic material on the immediate surface of the earth
that serves as a natural medium for the growth of plants.
2) What are the differences between the solum and regolith?
Solum: the upper and most weathered part of the soil profile, the A,E and B horizons.
Regolith: the unconsolidated mantle of weathered rock and soil material on the earth
surface. Loose earth materials above solid rock.
3) What are the six main ways soils function in natural and managed landscapes?
Describe each briefly. Medium
for plant growth, recycling system for nutrients and organic wastes, modifier of the
atmosphere, habitat for soil organisms, engineering medium, system for water supply
4) What five factors influence soil development?
1) Parent materials
5) define the term soil profile
- soil scientists often dig a large hole called soil pit, usually several meters deep and
about a meter wide to expose soil horizons for study. The vertical section exposing a set
of horizons in the wall of a pit
6) what are the five soil horizons most commonly found in humid forested regions of
1) O-organic layer at soil surface, organic materials formed from fallen leaves
and other plants and animals remains accumulating on the surface that undergo varying
degrees of physical and chemical breakdowns and transformation, so these layers of
older, partially decomposed materials may underlie , the freshly added debris
2) A- soils animals and percolating water move some of these organic materials
downward to intermingle with mineral grains of the regolith. These join the decomposing
remains of plant roots to form organic matter that darken the upper mineral layers, also
because weathering tends to be most intense nearest the soil surface, in many soils the
upper layers loose some of their clay or other weathering products by leaching to
horizons below A horizons are the layers nearest the surface that are dominated by
mineral particles but have been darkened by the accumulation of organic matter.
3) E- intensely weathered and leached horizons that have not accumulated
organic matter occur in the upper part of the profile, usually just below A horizon 4) B- varying amounts of silicate clays, iron, Al, oxides, gypsum, calcium
carbonate may accumulate in here, washed down from horizons above, formed thru
5) C-plant roots and microorganisms often extend below B, especially in humid
regions causing chemical changes in soil water, some biochemical weathering of the
regolith, the formation of C horizons=least weathered part of the profile.
7) in an ideal loam soil, what is the relative volume occupied by major constituents?
-organic matter 5%
-air and water 20-30% for each
8) what soil particles contribute to soil texture designations?
Sand clay silt
9)how does soil organic matter affect soil texture?
-physical chemical difference
10) define an essential element.
-organic matter binds mineral particles into a granular soil structure that is largely
responsible for bose, easily managed conditions of productive soils.
-imp for stabilizing granules
-(+) amount of water a soil can hold
abundant OM including plant roots helps create physical conditions favourable for
growth of higher plants and microbes contrasting, soils low in OM, especially high in silt
and clay are often cloddy and not suitable for optimal plant growth
-essential element: constant replenishment
-absorb nutrients in solution
-bulk of nutrients locked up in structural framework of primary minerals, org matter, clay,
11) Where is the pedosphere located relative to the atmosphere, lithosphere,
atmosphere and biosphere?
a) at km scale, soil participates in global cycles and the life of terrestrial ecosystems,
b) at m scale, soil forms a transition zone between the hard rock below and the
atmosphere above-a zone thru which surface water and groundwater flow and in which
plants and other living organisms thrive- biosphere
c) mm, mineral particles form the skeleton of the soil that defines pore space, some
filled with air and some with water, in which tiny creatures lead there livesd) micronanometer scakes, soil minerals (litho) provide charges, reactive surfaces that
adsorb water and cations dissolve in water (hydrosphere) gases (atmos), bacteria and
complex humus (macromoecues, biosphere
1) how were the following parent materials formed, transported or deposited?
Till: materials deposited directly by ice
Loess:wind blown material, main sources were the great barren expanses of till and out
wash left in Missouri and Mississippi river valleys by the retreating glaciers of the last
Outwash plains: in valleys and on plains where the glacial waters were able to flow
Lacustrine: when ice came to a stand still, where there was no ready escape for the
water, pounding began, ultimately large lakes were formed
Marine: over time sediment builds up on ocean floor
Colluvium: made up of poorly sorted rock fragments detached from the heights above
and carried downslope, mostly by gravity
Aeolian: very fine particles,
Residual: developed from weathering of the underlying rock
Alluvium: from streams that leave a narrow valley in an upland area and suddenly
descend to a mu