SSC LONG QUIZ Flashcards
Properties that are influenced by soil
texture include
PPISW
porosity, permeability, infiltration, shrink-swell rate, water-holding
capacity
the only soil in which neither sand, silt nor clay
predominates is called
loam
The mineral
constituents of a loam soil
40% sand
40% silt
20% clay
Sand is least active, having the least specific surface area, followed by silt; clay is
the most active.
SSC
SAND>SILT>CLAY
USDA STANDS FOR?
UNITED STATED DEPARTMENT of AGRICULTURE
REVIEW TEXTURAL TRIANGLE
The clumping of the soil textural components of sand, silt and clay
causes
AGGREGATE
to form and the further association of those aggregates into
larger units creates
SOIL STRUCTURE/PEDS
Soil structure affects
AWCPR
aeration, water movement, conduction of heat, plant root
growth and resistance to erosion
RESEMBLES COOKIE CRUMBS AND USUALLY LESS THAN 0.5 CM IN DIAMETER. COMMONLY FOUND IN SURFACE HORIZONS WHERE ROOTS HAVE BEEN GROWING
GRANULAR
IRREGULAR BLOCKS THAT ARE USUALLY 1.5-5.0 CM IN DIAMETER
BLOCKY
VERTICAL COLUMNS OF SOIL THAT MIGHT BE A NUMBER OF CM LONG. USUALLY FOUND IN LOWER HORIZONS
PRISMATIC
VERTICAL COLUMNS OF SOIL THAT HAVE A SALT CAP. AT THE TOP. FOUND IN SOILS OF ARID CLIMATE
COLUMNAR
THIN, FLAT PLATES OF SOIL THAT LIE HORIZONTALLY. USUALLY FOUND IN COMPACTED SOIL
PLATY
SOIL IS BROKEN INTO INDIVIDUAL PARTICLES THAT DO NOT STICK TOGETHER. ALWAYS ACCOMPANIES A LOOSE CONSISTENCE COMMONLY FOUD IN SANDY SOILS
SINGLE GRAINED
Peds are flattened one atop the other 1–10 mm thick. Found in the Ahorizon of forest soils and lake sedimentation.
PLATY
Prismlike peds are long in the vertical dimension,
10–100 mm wide. Prismatic peds have flat tops, columnar peds have rounded
tops. Tend to form in the B-horizon in high sodium soil where clay has
accumulated.
PRISMATIC and Columnar
Blocky peds are imperfect cubes, 5–50 mm, angular
have sharp edges, subangular have rounded edges. Tend to form in the Bhorizon where clay has accumulated and indicate poor water penetration.
Angular and Subangular
Spheroid peds of polyhedrons, 1–10 mm, often found in
the A-horizon in the presence of organic material. Crumb peds are more
porous and are considered ideal.
Granular and Crumb
: Is a measure of the degree of development or cementation within
the peds that results in their strength and stability.
Grades
Weak cementation allows peds to fall apart into the three textural constituents,
sand, silt and clay.
WEAK
: Peds are not distinct in undisturbed soil but when removed they break into
aggregates, some broken aggregates and little unaggregated material. This is
considered ideal.
MODERATE
PEDS are distinct before removed from the profile and do not break apart easily
STRONG
Soil is entirely cemented together in one great mass such as slabs of clay
or no cementation at all such as with sand.
STRUCTURELESS
Soil ______ is typically 2.60 to 2.75 grams per cm3 and is usually
unchanging for a given soil. ______ with high organic
matter content, and is higher for soils with high iron-oxides content.
PARTICLE DENSITY
Soil ________ is equal to the dry mass of the soil divided by the volume of the
soil; i.e., it includes air space and organic materials of the soil volume. Thereby soil
bulk density is always less than soil particle density and is a good indicator of soil
compaction.
Bulk Density
The soil bulk density of cultivated loam is about
1.1 to 1.4 g/cm3
(for comparison
water is 1.0 g/cm3
).
The more _______ the soil is the the greater is the bulk density value and the less _____ it is.
COMPACT and POROUS
FORMULA FOR BULK DENSITY IS
BD=Ws/Vt
1.0-1.3
Normal Soil
> 1.3
Compacted Soil, poor soil structure
> 1.0
Very loose Soil
Sandy soils have ____ because the particles tend to lie close
HIGHER BULK DENSITY
of soils is the mass (dry weight) per unit volume of soil excluding the pore spaces within that soil volume
PARTICLE DENSITY
Particle density (2.65g/cm^3) indicate the
mineral ancestry of soil
A higher particle density that (2.70g/cm^3) may mean that the soil could have been derived from?
Heavy minerals like iron bearing minerals
A low particle density (less than 2.50 g/cm^3) may indicate that the soil is ?
high in humus
The equation for determining soil particle density is?
PD=Ws/Vs
the quality or degree of having minute spaces or holes through which liquid or air may pass.
POROSITY
is that part of the bulk volume of soil that is not occupied by either
mineral or organic matter but is open space occupied by either gases or water. In a
productive, medium-textured soil the total pore space is typically about 50% of
the soil volume.
PORE SPACE
PORE SIZE
CRYPTOPORES>ULTRAMICROSPORES>MICROPORES>MESOPORES>MACROSPORES
The higher its bulk density the lower its _____
Porosity
SOIL POROSITY FORMULA
%PS = [1-BD/PD] X 100
is the ability of soil to stick to itself or to other objects
(cohesion and adhesion, respectively) and its ability to resist deformation and
rupture.
CONSISTENCY
A soil’s resistance to fragmentation and crumbling is assessed in the dry state by
rubbing the sample. Its resistance to shearing forces is assessed in the moist state
by thumb and finger pressure.
CONSISTENCY
depends on the ratio of the energy absorbed to that lost. Soil has
a temperature range between -20 to 60 °C, with a mean annual temperature from
-10 to 26 °C according to biomes.
SOIL TEMPERATURE
- Soils can process and hold considerable amount of water. They can take in water,
and will keep doing so until they are full, or until the rate at which they can
transmit water into and through the pores is exceeded. Some of this water will
steadily drain through the soil (via gravity) and end up in
the waterways and streams, but much of it will be _______
RETAINED(SOIL WATER RETENTION)
The maximum amount of water that a given soil can retain is called
Field Capacity
whereas a soil so dry that plants cannot liberate the remaining moisture from the
soil particles is said to be at
wilting point
The process by which soil absorbs water and water drains downwards is
called
Percolation
Soil water retention is essential to life. It provides an ongoing supply of water to
plants between periods of replenishment
Infiltration
SOIL MOISTURE CONTENT( θ) FORMULA
θ%=[(FW-ODW)] X 100
VOLUMETRIC MOISTURE CONTENT
Vw/Vt=θ
SOIL WATER DEPTH (HW)
Hw = Ov x Ht
a measure of the energy state of water in the soil
SOIL MOISTURE TENSION(SMT)
Moisture Content when pore spaces are fully-filled up with water
SATURATION(SAT)
Moisture content of the previously saturated soil
FIELD CAPACITY
The moisture content of turgid plants begin to wilt permanently
PERMANENT WILTING COEFFICIENT(PWC)
Air dry moisture content which is highly dependent on the relative humidity of the atmosphere
Hygroscopic coefficient (HC)
_________ condition involves putting the moist soil in an oven at 105-110 C for 24 hours
Oven drying (OD)
Gravitation Water (GW)
GW = SAT-FC
AVAILABLE WATER CONTENT (AWC)
AWC= FC-PWP
