Download Soil Review Powerpoint - Liberty Union High School District

Soil Review
Powerpoint
Soil Characteristics
Understand what soil is and how it forms. Compare
and contrast the characteristics of different soils.
What type do you have around your house?
1) clay = “layer silicates that are formed as
products of chemical weathering of other
silicate minerals at the earth's surface. They
are found most often in shales, the most
common type of sedimentary rock.”
2) silt = rock worn into tiny pieces (coarser
than clay, but finer than sand). usually 1/20
millimeter or less in diameter
3) sand = quartz or silica worn down over
time. grains with diameters between 0.06 mm
to 2 mm
4) organic matter (humus)
5) Loam = soil containing a mixture of clay,
sand, silt and humus. Good for growing most
crops.
Soil Porosity and
Permeability
Porosity - volume of water that “fits between” the soil particles
Permeability - rate of flow of water through soil
% retention - how much water is “trapped” by soil
Porosity and Permeability are directly related; when one is high, the other
is high as well. % water retention is inversely related to both.
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1) Clay -  porosity  permeability,  retention
2) Silt -  porosity,  permeability, retention
3) Sand -  porosity,  permeability,  retention
4) Organic matter -  porosity,  permeability, 
retention
Soil Horizons
Soil Horizons
Soil Conservation
Explain what soil erosion is. Describe its
causes and effects. List and describe various
soil conservation methods.
•Soil moves….due to
water, wind, people
•Loss of topsoil…the
most fertile
•Soil ends up as
sediment in water
•Soil IS
renewable…WHERE
does it come from?
Irrigation
Salinization &
Waterlogging
Salinization &
Waterlogging
Desertification
Discussion:
List and describe some of the pros and
cons of using fertilizers. What different
sorts of fertilizers are available?
Organic…
manure adds N and soil bacteria & fungi
green manure
compost
mushroom spores
Inorganic…1/4th of the world’s crops depend
on this.
N, K, P
Experimental data comparing methods!
Soil Formation
Soil formation - Parent material is slowly broken down by biological,
chemical and physical weathering.
Biological - Respiration of plant roots and other organisms
produce CO2, which reacts with soil water to produce carbonic acid
(H2CO3).
Chemical - Acids crack rocks  water seeps in  breaks
down particles.
Physical - Weathering introduces water that breaks down
particles.
Time scale - Formation of 2.5 cm of topsoil takes 200 - 1000 yrs.
Soil Formation
Soil Composition
Soil Composition
45% Mineral particles (broken down pieces of rock)
5% Organic matter (humus - from dead organisms, worm castings, leaf litter)
25% Water (precipitation)
25% Air (More with sandy soil, less with clay soil)
Soil organisms - Millions in one teaspoon of fertile agricultural soil!
- bacteria, fungi, algae, microscopic worms.
provide ecological services such as worm castings,
decomposition to humus, breaking down of toxic
materials, cleansing water, nutrient cycling from
decomposers or upon death
Soil Composition
Soil Texture
Loam - ideal agricultural soil
40% sand (larger - structural support, aeration,
permeability)
40% silt (smaller - holds nutrient minerals and water)
20% clay (even smaller - holds nutrient minerals and
water)
Plants grown in sandy soils
More susceptible to mineral deficiencies and drought
Plants grown in clay soils
More susceptible to waterlogging, and oxygen depletion
(think small pore size, low porosity)
Soil Texture Triangle
Soil Acidity (pH)
pH - concentration of H+ ions
Scale - From 0 (very acidic) to 14 (very basic, or alkaline)
pH of most healthy soils - 4 - 8
pH matters because it affects solubility of nutrient minerals
Aluminum and Manganese are more soluble in low pH - roots
sometimes absorb too much (toxic levels)
Soil pH affects leaching - high pH increases leaching of
important ions such as K+
Causes of changes - acid rain, decomposition, leaf litter, mining (acid
sulfate soils)
Remediation
- Too high pH, add acidic leaf litter
- Too low pH, add lime
Soil Nutrients (NPK)
Soil Nutrients (NPK)
Organic - animal manure, bone meal, compost (slow-acting, long-lasting)
Delay in availability to plants, needs time for the organic
material to decompose
Delay causes low level of nutrient leaching
Improves water holding capacity
Inorganic - Manufactured from chemical compounds (fast-acting, short-lasting)
Highly soluble so immediately available to plants
High solubility also makes it leach quickly (pollutes water)
Suppresses growth of microorganisms
Source of nitrogen gases that increase air pollution
Production requires much energy from fossil fuels, increasing
CO2 emissions.
Inorganic Fertilizer
Organic Fertilizer