chapter 9 Flashcards
objective of soil surveying and mapping
identify and delineate soil patterns formed within a homogenous soil forming environment
why would you want to classify soil?
the type of soil has a bearing on soil management and agricultural productivity.
soil is a
continuum
members of russian school
mendelejev, dokuchaev, sibirtsev, glinka
vasili dokuchaev
soil forming factors, soil forming processes, different soil
hans jenny
factors of soil formation (1941)
s= f(cl,o,r,p,t)
order
12 taxa
suborder
47 taxa
great groups
227 taxa
subgroups
> 1000
properties important to plant growth; broad textural classes averaged over control section or solum; mineralogical classes for dominant mineralogy of solum; soil temperature classes at 50 cm depth
family
kind and arrangement of horizons; color, texture structure, consistence, and reaction of horizons, chemical and mineralogical properties of the horizon
series
central concept taxa for great group and properties indicating intergradations to other great groups, suborders, and orders, extragradation to “not soil”
subgroups
subdivision of suborders according to similar kind, arrangement, and degree of expression of horizon; with emphasis on upper sequum; bass status; soil temperature and moisture regimes; presence or absence of diagnostic layers (plinthite, fragipan, duripan)
great groups
genetic homogeneity. subdivision of orders according to presence or absence of properties associated with wetness, soil moisture regimes, major parent material, and vegetational effects as indicated by key properties; organic fiber decomposition stage in histosols
suborder
soil forming processes as indicated by presence or absence of major diagnostic horizons
order
9 soil order recognized in the PH
alfisol
andisol
entisol
histosol
inceptisol
molisol
oxisol
ultisol
vertisol
12 soil orders
alfisol
entisol
inceptisol
oxisol
ultisol
vertisol
andisol
aridisol
gelisol
histosol
mollisol
spodosol
in semiarid to moist areas
result from weathering processes that leach clay minerals and other constituents out of the surface layer and into the subsoil, where they can hold and supply moisture and nutrients to plants. formed primarily under forest or mixed vegetative cover and are productive for most crops
10%
alfisol
show little to no evidence of pedogenic horizon development
occur in areas of recently deposited parent materials or in areas where erosion or deposition rates are faster than the rate of soil development; such as dunes, steep slopes, and flood plains.
16%
entisols
semiarid to humid that generally exhibits only moderate degrees of soil weathering and development
wide range in characteristics and occur in a wide variety of climates
17%
inceptisol
highly weathered soils of tropical and subtropical regions
dominated by low activity minerals, such as quartz, kaolinite, and iron oxides. indistinct horizons
occur on land surfaces that have been stable for a long time. low natural fertility as well as low capacity to retain additions of lime and fertilizer
8%
oxisol
soils in humid areas
fairly intense weathering and leaching processes that result in clay-enriched subsoil dominated by minerals, such as quartz, kaolinite, and iron oxides
acid soils in which nutrients are concentrated in the upper few inches
they have moderately low capacity to retain additions of lime and fertilizer
8%
ultisol
high content of expanding clay mineral
undergo pronounced changes in volume with changes in moisture. cracks that open and close periodically, show no evidence of soil movement in the soil profile
transmit water very slowly and undergone little leaching. fairly high in natural fertility
2%
vertisol
formed from weathering processes that generate minerals with little orderly crystalline structure
minerals can result in an unusually high water-holding capacity and nutrient-holding
highly productive soils, include weakly weathered soils with much volcanic glass as well as more strongly weathered soils. common in cool areas with moderate to high precipitation, esp. associated with volcanic materials
1%
andisols
too dry for the growth of mesophytic plants
lack of moisture greatly restricts the intensity of weathering processes and limits most soil development processes to the upper part of the soils
often accumulate gypsum, salt, calcium carbonate, and other minerals that are easily leached from soils in more humid environments
common in desert
12%
aridisols
