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CSS 200 – SOILS and PLANT NUTRITION - NOTES
WEEK #1
THE IMPORTANCE OF SOILS
SOILS ORIGIN AND DEVELOPMENT
INTRODUCTION and OVERVIEW
 Introduction (me and students)
 Syllabus (posted online and will go over in class)
 Handouts (posted online and will go over in class)
THE BIG PICTURE – THE EARTH (Show Ball)
 FINITE ECOSYSYTEM - BIOSPHERE
 CAUSE and EFFECT are all INTERCONNECTED
 EVERYTHING comes from the EARTH!
 EXCEPT for the SUN & ENERGY, MOON & STARS
 We tend to take this FOR GRANTED because we are so
REMOVED from BASIC PROCESSES of our own
EXISTENCE
 HOW MANY OF YOU...
 GROW some or all of your own FOOD?
 Have BUILT your own SHELTER?
 MADE or manufactured anything from RAW
MATERIALS?
 If EVERYTHING comes from the EARTH the
SIGNIFICANCE of CONSUMPTION and RECYCLING
becomes VERY IMPORTANT
 Can be looked at in TWO WAYS:
 REDUCE, REUSE, RECYCLE (Show overhead)
 PRECYCLING (Show overhead)
 Giving THOUGHT to what you NEED
 Making choices for the LEAST IMPACT on the
EARTH
 If buying new is the best option, consider the
PACKAGING and its IMPACT
 OLD SAYING: “USE it up, WEAR it out , MAKE
it do, or do WITHOUT”
 WHY REDUCE our IMPACT on the EARTH?
 US is 5% of WORLD POPULATION
 US PRODUCES 25% of WORLD’S WASTE!!!
 IMPERATIVE that we think how we can REDUCE
our IMPACT, because all that WASTE has got to go
SOMEWHERE (and more often than, not its back
into the ground)
 This is the BASIS for SUSTAINABILITY
 Our NATURAL SYSTEMS already do this
 MAN has created a problem through DISRUPTION of
NATURAL PROCESSES and needs to be RECTIFIED
THE IMPORTANCE of SOILS
SO... what does this have to do with SOILS???
 “SOIL is the most COMPLEX ECOLOGICAL SYSTEM on
the PLANET”
 MERITS our ATTENTION and PROTECTION for a number
of reasons:
 Important to CIVILIZATIONS (Show computer clip)
 SOILS can MAKE or BREAK CIVILIZATIONS
Example: Nile River – yearly flooding brought silt and
other rich deposits over the valley floor –
AGRICULTURE flourished and SUPPORTED a large
POPULATION
Example: Dust Bowl of the 1930’s – natural
DROUGHT and WIND, combined with MISUSE of
soil brought WIND EROSION and tremendous loss of
soil and destruction of the land and people on it
 GROWING POPULATIONS but LIMITED LANDS
 World population growing and doubling every 40
years
 Only 7% of EARTH is ARABLE (tillable) and
SUITABLE for AGRICULTURAL USE
 Of that ...some is LOST to DEGRADATION (poor
management practices) and/or URBANIZATION
(population pressures)
Example: Amazon River Basin – cleared for
agricultural use, without the ecosystem of the rain
forest, soils degrade rapidly and are unrecoverable
 SOIL - INTERFACE between ATMOSPHERE and
CRUST, important to MANY CYCLES on the earth
(Show overheads)
 CORE, MANTLE, CRUST (3-19 mi.), and THIN
LAYER of SOILS ( Show overheads)
Example: A GIGANTIC APPLE 200’ in diameter
but with the same layer of SKIN as a regular apple,
SKIN REPRESENTS the ratio of SOIL : EARTH
 SOIL LAYER is an INTERFACE that acts with
CRUST and ATMOSPHERE to CYCLE and
STORE various ELEMENTS rather than lose them
 TEMPERATURE – soils modulate temps
 Roots grow > 40 degrees
 Optimal 55 – 85 degrees
 All growth stops > 122 degrees
 CARBON CYCLE
 PHOTOSYNTHESIS – takes CO2
 RESPIRATION – takes O2
 plants incorporate in to tissues
 NITROGEN CYCLE
 ATMOSPHERIC N2 transformed into N
for plants to use by MICROBES in soils
 plants incorporate in to tissues
 OTHER MINERAL (NUTRIENT) CYCLES
 Nutrients come from ROCKS and
MINERALS that soils contain
 plants incorporate in to tissues
 GAS EXCHANGE
 Exchange of O2 and CO2 from
ATMOSPHERE to SOIL and back
through SOIL PORES
 WATER CYCLE
 Rainfall, Run-off, infiltration and
percolation of water through SOIL
PORES
 Evaporation and transpiration of water Evapotranspiration
 All CYCLES IMPORTANT for LIFE, and our
EXISTENCE on this PLANET would end if not for
SOILS
 MEDIUM for PLANT GROWTH
 PLANTS DEPEND on SOILS for:
 ANCHORAGE
 Roots grow in the PATH of LEAST
RESISTANCE
 GOOD ANCHORAGE depends on
FAVORABLE SOILS
 WATER
 SOIL supplies nearly all WATER a plant uses
 Without moisture ROOTS DIE or DO NOT
GROW
 Water is AVAILABLE in SOIL PORES
 OXYGEN
 All life needs O2 to RESPIRE to release
ENERGY and GROW
 AIR provides O2 and is AVAILABLE in the
SOIL PORES we call this AERATION (0 –
21% O2 in air)
 SOILS are usually LOWER in O2 than the
atmosphere - O2 in CRITICAL supply as
ROOTS take in O2 and RESPIRE CO2
 AIR and WATER COMPETE for PORE
SPACE in SOILS
Example:
Waterlogged soil = 0 % O2
Aerated soil = 21 % O2
 NUTRIENTS – 17 ESSENTIAL
 C, H, O – come from WATER and AIR
 14 OTHERS come from the SOIL, from
ROCKS and MINERALS
 ROOTS absorb these as IONS in the SOIL
SOLUTION (water that ions dissolved in)
SOIL MATRIX
 3 – PHASE SYSTEM (Draw on board)
 ARRANGEMENT of SOLID particles and PORE SPACES
or RELATIONSHIP of SOLID, LIQUID, GAS in SOILS
 IDEAL for PLANT GROWTH
 ROOTS grow in the PORE SPACES of soils and ABSORB
WATER, NUTRIENTS and O2 from ROOT HAIRS
 ROOT HAIRS are at the tips of roots and absorb the
most water
 ROOTS grow best where there is OPTIMAL
CONDITIONS of adequate WATER, O2,
NUTRIENTS
 Draw tree canopy and root growth
Example: Tree roots in good conditions are
60-100% greater than canopy
 Top 12” of soil – for O2, H2O, nutrients
(primarily AERATION)
Example: Black plastic and effect on roots
and lack of O2
USES OF SOIL
 AGRICULTURAL USES
 CROPLAND
 Soil worked and crops planted, managed and harvested
 ANNUAL CROPS – require yearly soil preparation
 Concerns are weeds, fertilization and organic
matter
 ISSUE: Soil EROSION due to uncovered soil
 PERENNIAL CROPS – planted every 3-20 years
 Soil held in place by cover crops or Horticultural
crops
 ISSUES: control weeds, reduce erosion,
compaction, OM stability
 GRAZING LAND
 Loosely managed land
 Planted in native and non-native grasses, shrubs
 FOREST LAND
 Disturbs soil the least, planted with tree species
 ISSUES: Logging practices – less vegetation,
compacted soil, erosion, compromises new tree planting
 ORNAMENTAL PLANTS
 Landscaping plantings in heavily disturbed soils
 ISSUES: compaction, disturbed soil layers,
 NON-AGRICULTURAL USES
 RECREATIONAL
 Playgrounds, golf courses, parks, campgrounds, sports
fields, etc.
 ISSUES: compaction, shear resistance, grading,
drainage, hardness, maintenance
 FOUNDATIONS for BUILDINGS
 SHRINK - SWELL POTENTIAL – swell when wet
and shrink when dry - UNSTABLE for
FOUNDATIONS
 LOAD BEARING CAPACITY – soils high in clay or
organic matter have LOW load bearing capacity
because may shift and crack
 WASTE DISPOSAL
 Human sanitary waste uses soil to filter and break down
harmful substances
Example: Septic systems and drain fields
Example: Sewage Sludge used on crops, highly
regulated by government
 Hazardous waste – leaching is prime concern
 BUILDING MATERIALS
 Historically used:
 Sod (Dakotas – grass, soil and roots)
 Adobe (in the SW – sun dried blocks)
 Rammed earth and Cob house building
Example: Cob house by Building 3
 Engineered soils – to support a load or stress
Example: Under sidewalks surrounding trees
LAND USE in the US
 Although MOST of our land (non-federal) is still in
AGRICULTURAL USE, it is rapidly being lost to URBAN
DEVELOPMENT and DEGRADATION
 URBAN DEVELOPMENT
 Urban Development - 7% and growing
Example: Urban growth boundary – one way to curb
growth and allow better decisions for urban planning than
using prime farm land
 Cropland – 25%
 Rangeland – 27%
 Pasture – 8%
 Forest land - 27%
 Conservation land – 2%
 SOIL QUALITY and DEGRADATION
 SOIL is basically NON-RENEWABLE in our
LIFETIMES
 SOIL QUALITY or HEALTH is important over the long
term
 SOIL DEGRADATION is the LOSS of QUALITY due to:
 Erosion
 Pollution
 Desertification –
 Changes in soil chemistry
 Salination – saltiness of soil
 Loss of OM
 BMP – BEST MANAGEMENT PRACTICES are
MAINTENANCE of SOIL QUALITY
 important to understand and implement
SOIL ORIGIN & DEVELOPMENT
 Soil is a SLOWLY RENEWABLE RESOURCE
 MANY YEARS to DEVELOP (100’s to 1000’s of years)
 NON-RENEWABLE in our LIFETIMES
 Still can GROW, CHANGE and DEVELOP over TIME
 ROCKS, MINERALS, and NUTRIENTS
 ROCK (solid bedrock of earth’s crust) is broken down to
PARENT MATERIAL (smaller rocks) and through the
process of WEATHERING is further broken down to SOIL
 DIFFERENCES between ROCK, MINERALS &
NUTRIENTS
 ROCK – Solid bedrock which is a mixture of MINERALS
of DIFFERENT KINDS and PROPORTIONS
 MINERALS – PURE INORGANIC ELEMENTS or
COMPOUNDS of a DEFINITE CHEMICAL
COMPOSITION usually CRYSTALLINE in form
 NUTRIENTS – Dissolved IONS in water called the SOIL
SOLUTION
 ROCKS are CLASSIFIED by:
 How they’re FORMED
 MINERAL COMPOSITION
 TEXTURE
 3 MAJOR CLASSIFICATIONS of ROCKS
 based on how they’re FORMED
 IGNEOUS ROCK – created by the COOLING and
SOLIDIFICATION of MOLTEN ROCK – LAVA
(extrusive) & MAGMA (intrusive)
 Covers ¼ surface of CRUST, but makes up ¾ of total
Examples: GRANITE – coarse texture, E. US
BASALT – fine texture, Cascades
OBSIDIAN – cooled rapidly, glassy, sharp,
Newberry Crater, Archeologist?
PUMICE – N. Crater Lake area @ Lemolo
Lake shores covered
 SEDIMENTARY ROCK – deposits of MUD and SAND
(through wind and water erosion) that are CEMENTED
together by CHEMICALS or PRESSURE
 Most formed in PREHISTORIC SEAS
 Covers ¾ surface of CRUST (over igneous)
Examples: LIMESTONE – finer, gives us ground lime
SANDSTONE - coarser
 METAMORPHIC ROCK - formed when either IGNEOUS
or SEDIMENTARY ROCK is subjected to GREAT HEAT
& PRESSURE
Examples: LIMESTONE >>>>> MARBLE
SANDSTONE >>>>> QUARTZITE
SHALE >>>>> SLATE
 SOIL is FORMED from the WEATHERING of ROCK
 ROCK (solid bedrock of earth’s crust) is broken down to
PARENT MATERIAL (smaller rocks) and through the
process of WEATHERING is further broken down to SOIL
 2 TYPES of WEATHERING
 PHYSICAL WEATHERING
 FRACTURING ROCK – physically breaking apart rock
 Freezing and thawing water in rock (frost wedging)
 Heating and cooling
 EROSION of ROCK – physically wearing rock away
 Rain and running water
 Wind
 CHEMICAL WEATHERING – changing rock chemically
 WATER (mildly acidic) DISSOLVES minerals in rock
into SOLUTION
 HYDROLYSIS – WATER reacts with minerals to create
NEW, SOFTER COMPOUNDS
Example: Limestone and vinegar or HCl Acid fizzes
 OXIDATION - O2 reacts with minerals to form NEW
COMPOUNDS
Example: Oxidation of Iron with O2 = rust
 PLANTS aid in PHYSICAL and CHEMICAL
WEATHERING too
 ROOT WEDGING - pries apart and fractures rock
 LICHENS – form mild acids that dissolve rock
FACTORS AFFECTING SOIL FORMATION
 PARENT MATERIAL
 CLIMATE
 LIFE
 TOPOGRAPHY
 TIME
 (HUMANS?)
 PARENT MATERIAL
 PARENT MATERIALS (broken up rocks) are derived from
ROCKS which are composed of MINERALS, all of which
directly influence the SOIL that develops
 3 TYPES of SOILS are formed (2 Mineral, 1 Organic)
 RESIDUAL SOILS – are soils FORMED IN PLACE
on top of existing BEDROCK
 Less common
 Form slowly from weathering
 TRANSPORTED SOILS – are soils that have been
TRANSPORTED and DEPOSITED from their
ORIGIN to a NEW AREA
 More common
 Form relatively quickly
 GLACIAL ICE - action of glacier moves soil
Examples: GLACIAL TILL – pebbles, rocks and
boulders moved and dropped in place
GLACIAL OUTWASH – sandy soils
along rivers and streams
LACUSTRINE DEPOSITS – finer
sediments in lakes
 WIND – wind moves FINE SAND or SILT
Examples: EOLIAN - sandy soil of Midwest
LOESS - silty soil of the Palouse (SE
WA and NE OR)
 WATER – water in rivers and streams moving
deposits called ALLUVIUM
Examples: FLOODPLAINS – like Nile river
DELTAS – river deposits when reach
ocean, very fertile
 GRAVITY – hilly, mountainous areas where
deposits move downhill by gravity are called
COLLUVIUM
Example: TALUS – deposits of rock and soil at
the bottom of hill, often seen hiking
 VOLCANIC SOILS – ash and pumice expelled
from active volcano and sometimes also carried
away by wind
Example: ASH & PUMICE – common in PNW,
Hawaii, Alaska
 CUMULOSE SOILS – soils that accumulate in one
spot
 ORGANIC DEPOSITS – plant debris breaks
down slowly to form deposits
 Organic soils contain > 20 % OM
 Formed under WATERLOGGED conditions
in lake or bog
 Decreased O2 > decreased decomposition of
OM > increased OM accumulation from
plants
 CLIMATE (Show handout)
 TEMPERATURE
 Incr. T >>> Incr. WEATHERING
 Incr. T >>> Incr. PLANTS >>> Incr.
DECOMPOSITION >>> decreases OM overall
 RAINFALL
 Incr. RAINFALL >>> Incr. LEACHING
 Lime, clay and nutrients move further down in
soil
 Incr. RAINFALL >>> Incr. PLANTS >>> Incr. OM
 LIFE - PLANTS & ANIMALS
 PLANTS – VEGETATION affects soil formation
 Grasslands high in OM because of root dieback every
year
 Forests low in OM because most of it above ground in
leaves
 SOIL BIOLOGY – all sorts of ORGANISMS in soils
 aid in mixing, OM decomposition, holding and
releasing of nutrients
 TOPOGRAPHY
 SLOPE – steepness
 ASPECT – where slope facing, N, S, E OR W
 Affects T and moisture
 Contrast bottom of hill to top
 TIME
 The LONGER the TIME, the MORE DEVELOPED the
SOIL PROFILE
 Developing 1’ of soil can take 100 – 100,000 YEARS
 0 YEAR – first EXPOSED to ATMOSPHERE
 (HUMANS?)
 some consider HUMANS as another FACTOR
 as we manipulate the landscape we TURN BACK
TIME to ZERO
 DESTROY horizons by plowing or grading, create
pans, deplete OM, create conditions for erosion
 BMP is crucial
THE SOIL PROFILE (Show overhead)
 To STUDY SOILS we DIG a PIT called a PEDON
 Usually 3’ x 3’ x 5’ DEEP
 SOILS CHANGE over TIME in response to 4 PROCESSES
 ADDITIONS
 OM, transported soils, pollution
 LOSSES (out of the profile)
 Deep leaching, erosion
 TRANSLOCATIONS – movement within the profile
 Leaching down
 Evaporation or Flooding up
 TRANSFORMATIONS – chemical alterations
 OM decay
 Weathering to smaller particles
 Chemical alterations
 Because of these processes, SOILS FORM LAYERS called
HORIZONS
 YOUNG soils have FEWER HORIZONS and
SHALLOWER PROFILES
 OLDER soils have more DISTINCT HORIZONS and
DEEPER PROFILES
 tend to acidic, leached, less productive soils
 SOIL PROFILE shows all HORIZONS from TOP to
UNWEATHERED PARENT MATERIAL (Show overhead)
 O – LITTERLAYER - OM, usually undisturbed soil
 A – TOPSOIL
 OM accumulates
 Darker color
 Best layer for plant growth
 E – ELUVIATION
 Leached (or washes out) layer within the A layer
 Light color
Example: Sandy forest soils with high rainfall
 B – SUBSOIL
 Low OM
 More clay
 Illuviation - Leachates accumulate (or washes in)
 C – PARENT MATERIAL
 Broken up rock
 Little weathering
 Roots can penetrate cracks
 R – BEDROCK
 Solid rock with some cracks
 LAYERS named by CODES identifies POSITION in PROFILE
and provides some INFORMATION about it
 SUBDIVISIONS of HORIZONS– transition layers between
soil horizons
 AB - between A & B with A DOMINANT
 LOWERCASE LETTERS (see Appendix #4)
 Denote a trait within a horizon
Example: p – plow layer, t - clay layer
 NUMBERS (see Appendix #4)
 Denote extra layers within horizons
Example: Bt1 & Bt2
LAB
 Work on WS1 – MINERALS, ROCKS, AND PARENT
MATERIALS
 Draw profile for WS2 – SOIL ORIGIN and DEVELOPMENT
 Due next week