module 8

-inventory of the soil resource describing the characteristics of the soils. classifies the soils. plots the boundaries of the soils on a map. makes predictions about the behavior of soils.

unit of publication

classifies the soils inches on the map represent inches on the ground

the map uses an _________ as
the base

3 Elements of a Soil Survey

inches on the map represent inches on the ground.

scale of 1:24,000

-very intensive (very detailed); experimental plots, building sites;
minimum size delineation is < 1 hectare

-intensive (detailed); general agriculture, urban planning; minimum delineation is 0.6 to 4has

-extensive; rangeland, community area planning; min delineation is 1.6 to 16has

-extensive (reconnaissance); for broad land use potential and general land management; min size delineation is 16 to 252 has

-exploratory; regional planning, national planning; min size delineation is
252 to 4,000has

refers to the system of classification developed by the USDA Soil Survey

basic guidelines

Reasons for Classifying Soils

presence or absence of major
diagnostic horizons

Subdivision of soil order based on moisture and temperature regime

Subdivision of Suborder based on differences, arrangement, and
degree of expression between horizons

integrates or transitional
orms to other orders, suborders, or great groups

Properties important for plant root growth; broad soil textural classes
averaged over control section or “solum”; mineralogical classes for dominant mineralogy
of solum; soil temperature classes

A class of soils and the basic units used to classify soils

Soil series in the Philippines

-distinct types of horizons that reflect nature of soil formation
-used for differentiating or classifying soil order level

a horizon
forms at or near the surface and in which most of the rock structure has been destroyed.

dark, soft, surface layer; thick greater than 10 inches; high base saturation of >50%; mineral soil; soils formed under prairie vegetation.

like mollic but
contains more than 250ppm of citric acid soluble
P2O5

like mollic, but low base saturation

organic soil (20-30% organic matter; saturated
with water

thin, light colored surface layers that do not fit any
of the above

man-made, surface horizon that is
greater than 50cm thick created by many years of addition of manure

very weathered layer of only Fe and Al oxides and 1:1 clay
minerals; low pH and not very fertile (found in tropical soils); Bo

light-colored, low % base-saturation and well-drained

thin, black to dark reddish pan
cemented by iron, iron and manganese or by iron-organic matter complex

subsoil cemented by silica

subsoil that is hard when dry but
brittle when moist

light colored subsoil that is hard where
clay and free iron oxides have been leached out

accumulation of CaCO3 or CaMg(CO3)2

accumulation of gypsum

cemented by CaCO3

slightly altered layer; not weathered enough to be
argillic; Bw horizon designation or development of color and or structure

no diagnostic subsurface horizon present

-dominant type of clay minerals

proportion of coarse fragments (2mm-74mm size particles) in
combination with fine fragments (<2mm size particles)

-mean annual soil temperature (MAT) measured at 50 cm from surface

mean annual temperature (MAT) is <0oC

MAT is 0oC-8oC

MAT is <8oC (warmer than cryic in summer)

MAT is 8oC-15oC

MAT is 15oC-22oC

MAT is >22oC

Prefix used if mean summer (June, July, August) and winter
(December, January, February) temperature differ by <5oC

MAT is <8oC

MAT is 8oC-15oC

MAT is 15oC-22oC

MAT is >22oC

-number of days when soil contains available water during the period
when soil temperature at 50cm below the surface is above 50C
-measured in terms of the absence or presence of water held at a tension of
<15 bars in the moisture control section by a period of one year
-soil moisture control section: 10-30cm in clayey soils; 20-60cm in loamy
soils; and 30-90cm in sandy soils

soil is saturated and no dissiolved
oxygen (reducing regime)

soil moisture control section is dry more than
half the time when soil temperature at 50cm is >5OC; moist for <3 months only

dry for >3months and continuously moist
for at least 3 months

soil is dry for <3 months only

soil is continuously dry 45 days after
summer and continuously moist 45 days after winter (dry summer-wet winter)

Naming Soil

very young soil showing very limited profile
development

young soil with moderate profile
development

limited change in parent material due to
dryness

young soils with little profile development;
presence of permafrost layer

soils with thick, dark, soft surface; soils of
the grassland

soils from volcanic ash and cinders

Acidic sandy soils with thick E
and red

argillic B horizon with high base saturation;
fertile forested soils with ochric and argillic

the B horizon has high amount of soft clay
but low base saturation; soils more weathered than Alfisols

highly weathered soil with B horizon
containing mainly 1:1 Kaolinte clays

shows large cracks upon drying due to
dominance of monmorillonite

organic soils; peat soils, organic
material

undecomposed to slightly decomposed organic matter in
waterlogged areas

highly decomposed organic matter

-soils are classified according to their capability for agricultural use or nonagricultural use with a primary aim of protecting the soil from erosion and degradation

good land that can be cultivated safe and extensively to most crops

good land that can be cultivated safely using easily applied
conservation practices

moderately good land that can be used regularly for cultivated crops

fairly good land that is best suited for pasture but which can be used
for agricultural crops in good rotation

Land that is flat but is too wet or stony

too steep, eroded or shallow for cultivation of regular
agricultural crops and is better left to pasture forestry.

very steep, eroded, rough, shallow or dry and is better
suited to pasture if handled carefully

level land that is wet most of the time and cannot be drained