Soil color
can be used to indicate the organic content and fertility of a soil and/or the type of minerals and elements that are in the soil
Munsell Color Chart
use to determine the color of the soil through a chip which consists of hue, value, and chroma
chroma
intensity or brightness of a color
value
Darkness or lightness of a color
hue
redness or yellowness of a soil
Mottles
Usually the result of alternating periods of reduction and oxidation caused by seasonally fluctuating water tables.
soil texture
the soil quality that is based on the proportions of soil particles
coarse fragment
Not considered part of fine earth fraction which are commonly gravel, cobbles, and boulders
sand
visible without a microscope and are rounded or angular in shape. May appear white due to quartz and brown due to other minerals. Feels gritty and considered non-cohesive.
Silt
Not visible without microscope.Feels smooth and floury. Easily washed away by flowing water highly erosive
clay
Flat plates or tiny flakes. If suspended in water, will not settle. Pore spaces are very small and convoluted. Movement of water and air very slow.
Textural Profile
aid in looking for the translocation of clay.
Soil structure
The arrangement of primary particles into secondary particles, units or peds. Describes the clustering of soil particles into aggregates of certain size, shape and stability.
Single grain
A type of soil structure that shows little or no tendency to adhere to other particles.
Spheroidal
A type of soil structure which are composed of aggregates not over � inch in diameter. Lie loosely and are readily shaken apart. Characteristics of many surface soils
Granular
A type of spheroidal soil structure that is porous, may be separated from each other in a loosely packed arrangement
Crumb
A type of spheroidal soil structure that is very porous
Platy
A type of soil structure characterized by relatively thin horizontal peds or plates. Often inherited from the parent materials, especially those laid down by water or ice
Block-like
A type of soil structure that ranges from a fraction of an inch to 3 or 4 inches in thickness. Usually confined to the subsoil and their state of development and other characteristics have much to do with soil drainage, aeration and root penetration
Angular blocky
A type of blocky soil structure characterized with sharp edges of the blocks and the rectangular faces distinct
Sub-angular blocky
A type of blocky soil structure with the corners that are mostly rounded (sub rounding has occurred).
Prism-like
A type of soil structure characterized by vertically oriented aggregates or pillars that vary in length and may reach a diameter of 6 or more inches. Commonly occur in subsoil horizons in arid and semi-arid regions
Prismatic
A type of prism-like soil structure with tops of the prisms that are relatively angular and flat horizontally.
Columnar
A type of prism-like soil structure with pillars with distinct rounded tops
Massive
A type of soil structure that shows little or no tendency to break apart under light pressure into smaller units.
Flocculation
The mutual attraction clay and organic molecules
floccule
microscopic clumps of clay
Aggregate stability
The ability of soil aggregates to resist disruption when outside forces are applied (usually associated with water).
Density
It represents mass (weight) per unit volume of a substance
Particle Density
the mass per unit volume of the soil particles which are not affected by pore space and does not change easily
Bulk density
The mass of dry soil per unit volume, including the air space
Porosity
The percentage of the total volume of a rock or sediment that consists of open spaces.It directly influences soil water movement
Hydraulic conductivity
Property of soil that describes the ease with which water can move through pore spaces
Infiltration
Process by which water on the ground surface enters the soil
Macropores
Pores that are too large to have any significant capillary force. Full of air at field capacity.
Mesopores
Pores filled with water at field capacity
Micropores
Pores that are filled with water at permanent wilting point. Suction is required to remove water
Adsorbed water
also known as hygroscopic water. Held on the surface of the particle by powerful forces of electrical attraction and virtually in a solid-state of very small thickness. Cannot be removed by oven drying at 110 o C.
Water at permanent wilting point
Water that can be removed by oven drying but not by air drying
Capillary water
held by surface tension, generally removable by air drying
Gravitational water
Removable by drainage, can move in the voids between soil grains
Chemically-combined water
In the form of water of hydration within the crystal structure. Not generally removable by oven drying
Maximum retentive capacity
When all soil pores are filled with water, the
soil is saturated and it is at
Field capacity
Moisture content of the soil after gravity has removed all the water it can. Usually occurs 1-3 days after a rain
Permanent wilting point
Soil moisture percentage at which plants cannot obtain enough moisture to continue growing
Available water storage capacity
Amount of liquid water stored in the soil and subsequently released for use by the plants
Gravitational Potential
Water has a positive energy and can flow out of the soil through the large pores. A point when cohesive forces are not large enough to hold onto the water
Matric Potential
The potential energy of water attracted to soil solids
Soil Moisture tension
Tenacity with which soil holds water. It is a negative pressure and commonly expressed in units of bars
Hand feel method
Soil water content measurement which is a The faster method but is prone to error since it requires experience and can be subjective
Gravimetric method
A direct measurement of soil water content. A sample of moist soil is weighed and then dried in an oven at a
temperature of 105 o C for about 24 hours, and finally weighed again
Electrical Resistance Blocks method
block uses small blocks of porous gypsum, nylon,
or fiberglass, suitably embedded with electrodes. When placed in moist soil, it absorbs water in proportion to the soil moisture content
Neutron Scattering method
A neutron scattering probe contains a source of fast
neutrons and a detector for slow neutrons. When fast neutrons collide with H atoms, the neutrons slow down and scatter. The number of slow neutrons counted by a detector corresponds to the soil water co
Tensiometer method
is a water filled tube closed at the bottom with a porous ceramic cup and at the top with an airtight seal. Once placed in soil, water in the tensiometer moves through the porous cup into the soil until water potential is the same as the matric water pote
Soil consistency
Ability of soil to stick to itself or to other objects (cohesion and adhesion, respectively) and its ability to resist deformation and rupture
Stickiness
the ability of the soil material to adhere to other objects.
Plasticity
the ability of the soil material to change shape, but not
volume, continuously under the influence of an applied stress and to retain the impressed shape on removal
of the stress.
Atterberg Limits
The arbitrary limits which define the boundaries between the different states of rigidity or fluidity of fine-grained soils.
Liquid limit
The minimum moisture content, expressed as a percentage of the oven dry soil weight, at which the soil will begin to flow when subjected to a small shearing force.
Plastic limit
The minimum moisture content at which the soil can be rolled into a thread one-eighth of an inch in diameter without crumbling and is determined by trial and error.Soil can no longer behave as plastic
Shrinkage limit
Water content in which the soil no longer changes in
volume regardless of further drying
Plasticity Index
The difference between the liquid limit and the plastic limit.