Soil Properties



Soil Properties
Essential Standard 5.00- Explain
the role of nutrients and fertilizers.
Objective 5.01
■ Discuss Horticulture soils
Soils and growing media
■ Soils and growing media are made up of two
types of materials
– Organic matter
– Inorganic compounds
Growing Media
■ When growing plants in a greenhouse, dirt from the
ground cannot be used because it may contain:
■ Insects
■ Diseases
■ Weeds
■ Greenhouse plant growers will mix different soil-less
materials together to make a soil suitable for growing
plants inside of a greenhouse in containers.
Organic Soil-less Media Components
■ Media is
– any matter, excluding organic soil, used for
the production of horticultural plants.
– Soil-less media does not contain natural soil.
The soil is replaced by other materials
Organic Matter (OM)
■ Dead plant or animal tissue
■ contains carbon
■ usually has diseases or insects
Types of Organic Soil-less Media
Peat Moss
■ Organic and has a slightly acidic pH
■ Partially decomposed material mined from the
■ Has good moisture holding properties
Types of Organic Soil-less Media
• Decayed organic matter
• Compost is used for soil conditioning and fertilizer.
Types of Organic Soil-less Media
Sphagnum Moss
• Sphagnum is organic and is very acidic
• Dehydrated remains of acid bog plants
• Holds moisture
• Commonly used line wire hanging baskets
Types of Organic Soil-less Media
• Organic and slightly
acid pH
• Larger matter added
to some horticulture
media to promote
• Adding bark to a
soilless mix usually
makes the mix
• Widely used in tree
and shrub production
Additional Organic Materials
Used in Soil-less Media Mixes
■ Sawdust and Wood Shavings
– Have a high carbon to nitrogen ration
– Make nitrogen unavailable for plant use
■ Organic materials must be well rotted or decomposed to
avoid problems with nitrogen tie-up.
Inorganic compounds
■ Do not contain carbon
■ usually sterile
Types of Inorganic Soil-less Media
• A light-weight mica mineral matter commonly used
to start seed and cuttings.
• Inorganic and has a slightly alkaline pH
• Holds moisture
Types of Inorganic Soil-less Media
 A natural volcanic material
 Slightly alkaline pH
 Helps with soil aeration and drainage
Advantages of horticultural soils
pH is neutral.
Disease and weed free.
It is good for starting disease sensitive seeds
• Tomato
5. It is easy to control the nutrient content
6. Improves crop uniformity.
7. It is easy to create a horticulture soil for
particular plant needs.
It is light weight
Objective 5.02
■ Discuss the soil profile and soil sampling for
surface and subsurface layers
Soil Profile
■ Soil layers are
called horizons
■ All soil profiles do
not have the same
number of horizons
■ Most typical soils in
NC will have a
minimum of the A,
B, and C or R
Soil Profile
O Horizon
A Horizon
• Rich Soil found
where a plant cover
has been in place for
an extended time
• Is rich in Organic
• Dark in Color
• Most fertile layer
in the soil
• The topsoil and
most fertile in the
absence of an O
• Home to
earthworms and soil
• Brown in color
B Horizon
■ Subsoil
■ Clayey soil with high mineral
■ Brown to Reddish in Color
C Horizon
■ Parent Material
■ Mostly Clumps of unweathered rocks
R Horizon
■ Bedrock
■ Very few roots can penetrate
Soil Structure
■ How particles cluster together
– single grain
– granular (best for most plants)
– blocky
– platy
– massive
Soil Structure
■ Soil structure is more important to producers who
grow plants in natural soils
■ Producers of container grown plants add
ingredients to make growing media desirable
■ Granular soil structure is the best.
– Plants have good root development
– Water movement is at an appropriate rate
Soil Texture
■ Size of particles
■ Types of textures
– clayey
– loamy
– sandy
Clayey Texture
■ Small particles
■ Has a high water-holding capacity
■ most common texture in western NC
■ Medium sized particles
■ Good moisture and nutrient holding capacity
Loamy texture
■ About equal parts of sand, clay and silt
■ Ideal texture for most non-container outside plants
Sandy texture
■ Large particles
■ Low moisture-holding
■ Most common in eastern
Soil pH
■ Measurement of acidity or alkalinity
from 0 to 14
– Acid-less than 0-6.9
– Alkaline-more than 8-14
– Neutral - 7
■ Most organic matter is acid
■ Most artificial media is neutral
■ Ideal pH for most gardens is 5.5 to
■ Lime will raise the pH value in soils
■ Calcium or sulfur will lower the pH
Physical Properties of Soils
■ Permeability
– rate at which water moves through the soil
■ Water holding capacity
– ability of a soil to hold water for plant use
■ Porosity
– amount of air space between soil particles
Physical Properties of Soils
■ 50% of soil should be pore space
– 25% water space
– 25% air space.
■ 50% of soil should be soil
– 45% mineral matter
– 5% organic matter
Soil Sampling
■ Soil sampling and testing is essential for an
accurate fertilizer recommendation for growing
Soil Sampling Procedures
1. Create a visual grid of the area to be
• For gardens and landscapes, take 5-10 subsamples
• Sample before the growing season.
2. Use a stainless steel soil-sampling probe.
3. Take the surface sample to tillage depth
1. about 4inches for lawns
2. 6-8 inches for crops
4. Mix the soil samples together.
Soil Sampling Procedures
Remove any grass, rocks or other material besides soil.
Avoid unusual spots
• Problem areas need to be sent in a separate box.
7. Place soil samples in a box
• Obtain from the County Extension Office along with
Soil Sample Information sheet
8. Send the box and information to:
• Agronomic Division Soil Test Lab in Raleigh for a free
soil test.
FFA Land Judging CDE

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