Ms. Lacross April 2015 Agriscience and Technology I Introduction to Soil Science.
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Transcript of Ms. Lacross April 2015 Agriscience and Technology I Introduction to Soil Science.
Ms. LacrossApril 2015
Agriscience and Technology I
Introduction to Soil Science
After this unit you will be able to:
Identify and Identify and describe soildescribe soil
Describe the Describe the importance importance
of soil of soil Describe Describe
and draw a and draw a soil profilesoil profile
Soil Introduction
Soil Origin and Development
• Pedology: The study of soil formation
• V. V. Dokuchaev (Russian) is credited with laying the foundation of modern Pedology– published a careful study of
Russian Soils in 1883
• Hans Jenny (US) published the Factors of Soil Formation in 1941 developed 5 factors of soil formation
Soils Perform Several Vital Functions
Sustaining plant and Sustaining plant and animal life below and animal life below and above the surfaceabove the surface
Regulating and Regulating and partitioning water and partitioning water and
solute flowsolute flow
Filtering, buffering, Filtering, buffering, degradingdegrading, immobilizing, and , immobilizing, and detoxifyingdetoxifying
Storing and cycling Storing and cycling nutrientsnutrients
Providing Providing supportsupport to to structuresstructures
What is Soil?
Soil Components
The Soil Body
• Soil is a – collection of natural bodies of
the earths surface– contains living matter that is able
to support growth of plants
• Soil varies across the landscape• Pedon: Is a small section of soil
extending from the surface to the depth of root penetration
Soil Vs Dirt
Soil Dirt
Material which nourishes and supports growing plants
Soil out of place
Compilation of minerals, air, water, animals and other living matter
Unable to serve its original purpose
Contains an equal amount of Sand, Silt and Clay
Can not support plant life
Parent Material
• Soil Genesis = the process of creating soil from parent material
• Soils form directly from bed rock• Transported soils: developed from weathered
material and are transported from their place of original origin – glacial ice: carried parent materials over the northern
part of America– wind– water – gravity
Parent Material
• Soil Genesis = the process of creating soil from parent material
• Soils form directly from bed rock• Transported soils: developed from weathered
material and are transported from their place of original origin – glacial ice: carried parent materials over the northern part
of America– wind– water – gravity
Physical Properties of SoilColor, Texture, Structure and Horizons
Soil Components and Texture
• Soil Texture describes the portion of three sizes of soil particles– Sand – largest– Silt- medium– Clay- smallest
12 Texture Classes
• The United States Department of Agriculture (USDA) has identified 12 soil texture classes
Importance of Soil Texture
Texture is important because it affects:• Water-holding capacity—the ability of a soil to retain
water for use by plants• Permeability—the ease with which air and water may
pass through the soil• Soil workability—the ease with which soil may be
tilled and the timing of working the soil after a rain• Ability of plants to grow—some root crops like carrots
and onions will have difficulty growing in a fine-textured soil
Soil Texture Triangle
• Way of showing proportions of sand, silt and clay in the soil
• Texture determines practices that should be used.
Soil Texture by Feel
• Texture class can be determined by feel
• To determine texture a person MUST be familiar with the composition of soils
• Gather a bit of soil and add water droplets until the soil is moldable
Soil Particles
• Soil is made of solid particles• particles largely consist of
mineral matter and organic matter
• between these soil particles are open spaces called pore space
• the arrangement of the solid particles and the pore space is called the soil matrix
Soil Structure
Aggregate: clumps of soil particles held together by moist clay, organic matter, by organic compounds
Soil Color
• Described by comparing the color of a soil horizon with a Munsell color chart
• Soil horizons have several colors
• Dark colored horizons have MORE organic matter than lighter ones
Soil Color
• Dark = organic matter• Red = iron• Brown = well drained• Grey (gley) = poorly drained• Mottled: redoximorphic concentrations,
depletions = restricted aeration, poor drainage
Soil Horizons
• System for naming soil horizons
• A, B and C are the master horizons
• Each layer is identified by a code: O, A, E, B, C and R
Soil Profile
O: Organic MatterA: Top Soil
– Surface mineral layer where organic matter accumulates
E: Zone of Eluviation– depleted in clay, chemicals
and organic matter– light colored – many soils do not have this
horizon
Soil ProfileB: Subsoil
– “zone of accumulation”: where chemicals leached out of the A horizon accumulates. lower organic matter content than top soil
C: Weathered/aged parent material
– little touched by soil-forming processes
– soft, weathered bedrockR: Hard Bedrock
– limestone, sandstone or granite
Soil Taxonomy
Soils Taxonomy
• Soil is as variable as leaves so we use a system to name soils
• Soil Taxonomy: – Six categories: order, suborder, great group,
subgroup, family and series– Twelve orders in the world– More than 17000 series in the US
Soil Taxonomy: 6 Groups
• Soil orders are defined on the basis of horizons and materials– Suborder: based on soil moisture regimes– Great Group and Subgroup: based on the presence or
absence of certain kinds of soil horizons– Family: based on particle-size, temperature of subsoil
horizons– Soil Series: based on a wide set of properties and are
named for the local community in which the soil was first identified
Twelve Soil Orders
• Gellisols• Histosols• Spodosols• Andisols• Oxisols
• Vertisols
• Aridisols• Ultisols
• Mollisols• Alfisols
• Inceptisols• Entisols
Soil Orders
Alfisols•Soils with a subsoil accumulation of silicate clay that are moderately weathered•Abbreviation: ALF
Andisols•Soils formed from volcanic materials•Abbreviation: AND
Soil Orders
Aridisols•Soils of Arid Environments•Arid = dry, climates lacking vegetation •Abbreviation: AID
Entisols•Very weakly developed soils •Including sandy soils•Abbreviation: ENT
Soil Orders
Histosols•Soils formed from organic materials•Abbreviation: IST
Inceptisols•Weakly developed soils•Excluding sandy soils•Abbreviation: EPT
Soil Orders
Mollisols•Soils wit thick, dark surface horizons•They are high in organic matter•Abbreviation: OLL
Oxisols•Highly weathered soils or tropic areas•Are high in Iron and aluminum-oxide •Abbreviation: OX
Soil Orders
Spodosols•Soils with a subsoil accumulation or aluminum, organic matter and Iron•Abbreviation: OD
Ultisols•Soils with a subsoil accumulation of clay that are highly weathered•Abbreviation: ULT
Soil Orders
Vertisols•Soils that undergo shrinking and swelling•Abbreviation: ERT
Gellisols•Soils of a very cold
climates that contain permafrost within the
soils surface•Abbreviation: EL
Soil Quality
Soil Quality
• Soil Quality = the capacity of a specific soil to provided needed functions for human or natural ecosystems over the long term–can sustain plant and animal growth–can maintain air and water quality–support human health
Soil Quality
• Soil degradation = The loss of soil quality• Soil connects intimately to water this also
means water problems• How to fix it?
– BMP’s or Best Management Practices– involve keeping the soil covered as much as
possible– employing management methods like mulching
and cover cropping
Soil and Climate
• Carbon sequestration: the process of storing carbon in soils, plans and elsewhere