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Mrs. Long
Horticulture I
Fall 2013
The Dirt on Soil!An Introduction to Soil ChemistryThe Dirt on Soil!
An Introduction to Soil Chemistry
What is soil?What is soil?
Soil is the unconsolidated cover on the surface of the earth.
Soil is made up of mineral particles, organic particles, air and water.
Soil is capable of supporting plant growth.
Soil ComponentsThe 4 parts of soil
MineralMatter45%
SoilWater25%
SoilAir
25%
OrganicMatter
5%
About ½ of the soil volume is solid particles
About ½ of the soil volume is pore space
Anchor plant rootsSupply water to plant rootsProvide air for plant rootsFurnish nutrients for plant
growthRelease water with low levels
of nutrients
Anchor plant rootsSupply water to plant rootsProvide air for plant rootsFurnish nutrients for plant
growthRelease water with low levels
of nutrients
Functions of agricultural soils
Organic matter is the glue that holds the aggregates together
Large pores (spaces) between aggregates are filled with air in a moist soil.
Small pores are filled with water in a moist soil. Even smaller pores inside the aggregates (not shown) are also filled with water.
Soil StructureThe arrangement of sand, silt, and clay particles to form larger
aggregates. How they fit together!
1/10 inch
SandLoose
SiltyGranular
ClayeyPlaty or
Blocky
Soil Structure
The mineral part of soil consists of sand, silt, and clay particles
Sand – Largest particles – low moisture holding capacity
Silt – Medium particles – good moisture holding Clay – Smallest particles – Hold a lot of water Loam – equal parts sand, silt, clay – ideal texture!
Soil Texture
Sand0.1 – 0.002 in2 – 0.05 mm
Silt0.002 – 0.0001 in0.05 - 0.002 mm
ClayLess than 0.0001 inLess than 0.002 mm
1/100 in
Parent MaterialMechanical weathering – breaks down rock
into smaller pieces without changing soil chemistry
Chemical weathering – breaks down rocks into smaller pieces by chemical reaction
Biological weathering – results from activities of living organisms
Where does soil come from?
Mechanical Weathering
Chemical Weathering
Biological Weathering
Bring a small soil sample from your yard at home.Make sure its clean.Bring in a full quart-sized ziploc bag full of soilYOUR NAME has to be on it!!
Homework for 04/
5.02 Discuss the soil profi le and soil sampling for surface and subsurface layers.
10/31/12
Soil Sampling
Soil Particle Size Lab (Part I)Take your soil sample (1 per group)Place a cup full of soil into a jarFill the jar to the top with water and tighten
the lid.Shake for 3 minutes.Set to side (labeled) until tomorrow!
Before we start today:
Soil LayersSoil layers are called
horizons.Layers parallel to
earth’s surfaceDefined usually by
color, texture and physical features.
O horizonThe O horizon
contain Organic matter
Uppermost dark Colored
Most fertileMade of leaves,
twigs, waste, decaying matter
A horizonTopsoilPorous mix of humusJust below the OHome to earthworms
and microorganismsBrown in color
B horizonSubsoilClayey with high
mineral contentBrownish redReceives a lot of
leached material
C horizonParent materialClumps of
unweathered rocks
R horizonBedrockCannot be dug by
handVery few roots can
penetrate
PurposeDetermines levels of
fertility in soil Use this information
to make accurate fertilizer recommendations for growing plants
A soil test shows deficiencies, excesses and imbalances can be avoided.
The Soil Testing Laboratory
Kits are available at local garden centers
Submit samples to NC Dept of Agriculture and Consumer Service Agronomic Division
https://www.youtube.com/watch?v=vb5wtgaKGUs
Lime & Fertilizer Recommendations
Information from a soil test will help you select the proper liming and fertilization program to obtain optimal growth of lawn, garden and ornamental plants.
Step 1Create a visual grid
of the area to be planted.5-10 subsamples
from the siteSample before the
growing season
Step 2Use a stainless steel
soil-sampling probeTake the surface
sample to tillage depth4 inches for lawns6-8 inches for crops
Step 3Mix soil samples
together.
Step 4 Remove any:
GrassRocksAny other material
SOIL ONLY!!
Step 5Place soil samples in
a boxGet one from County
ExtensionAlso need Soil
Sample Information Sheet
Step 6Send soil tests to
RaleighFree for residents
NCDA&CS Agronomic Services DivisionMailing Address: 1040 Mail Service Center, Raleigh NC 27699-1040Physical Address: 4300 Reedy Creek Road, Raleigh NC 27607-6465Phone: (919) 733-2655; FAX: (919) 733-2837
Perform the: Soil Testing Webquest (Activity 5.02.02)
Classwork
Making “Dirt”Bedrock at bottom - RParent material - CSubsoil - BTopsoil - AOrganic matter – O
Today’s Lineup
Types of Horticulture Soils
Peat MossOrganicPartially decomposed
material from Swamps
Holds moisture
Perlite
InorganicNatural volcanic
materialHelps with soil
aeration and water holding capacity
Organic MatterDead plant or animal
tissueContains Carbon!
Decayed organic matter
Used for soil conditioning
Fertilizer
Organic
Compost
BarkOrganicLarger matterPromotes drainageMainly for trees and
shrubs
Sphagnum MossOrganicDehydrated bog
plantsHolds moistureVery acidicHanging baskets
AdvantagesSterilepH is neutralDisease and weed
freeGood for starting
plantsEasy to mixImproves plant
uniformity
ExpensiveLight weight
Horticulture Soils
Disadvantages
Hydroponics
The process of growing plants without soil.
No soil & problems associated with soil.Easy to control nutrient content of plants.
Advantage of Hydroponics
Plant support must be provided with strings, wires, or stakes.
Water quality must be high.Diseases spread through water.More moisture or humidity in air to cause
favorable environment for disease organisms.More expensive.
Disadvantages of Hydroponics
Background on Today’s Lab
Soil pH is a measure of the acidity or alkalinity of soils
pH ranges from 0-14, 7 being neutralIdeal pH is 5.5-7.5
pH
LimeRaises the soil pH Lowers the soil pH
pH
Calcium/Sulfur
Soil Texture TriangleGive names to soils
combosClay
Sandy ClaySilty ClayClay LoamSandy Clay LoamSilty Clay Loam
LoamSandy LoamSilty Loam
SandLoamy Sand
Silt
PermabilityRate at which water moves through the soil
Physical Properties of Soil
Water Holding CapacityAbility of soil to hold water for plant use
Physical Properties of Soil
PorosityAmount of air space between particles
Physical Properties of Soil
