Download HORTICULTURE_files/Unit 8

SOIL
• Medium: The soil mixture is
the plant’s source for
food, water, and support
▫ The soil mix will have
effect on the health,
vitality, and appearance
of a plant or crop
SOIL FORMATION
• Begins as rock that is broken into
smaller particles
▫ Snow, ice, wind, and rain
• Parent material: The original rocky
material before weathering has
taken place
• Lower plant forms such as lichens,
moss, and fungi grow on rock
matter
• Organic matter: The decay of plants
and animals which is essential for soil
formation
WEATHERING
• Changes the consistency, chemical makeup,
moisture, content, and general composition of
a soil
▫ Physical and chemical weathering
• Physical: Caused by heating and cooling,
freezing and thawing, wind and water
• Chemical: Reaction and
interaction of water, oxygen,
carbon dioxide, and other
substances
TOPOGRAPY
• The surface features of a region
including hills, valleys, rivers, lakes,
and mountains
• Causes particles to move up
or down slopes and relocates
the parent material
• Soil is ever changing
because of:
▫ Particle structures, sizes,
types, amounts or organic
and inorganic content,
layers of soil, and pH values
SOIL COMPOSITION
• Minerals: The inorganic
material in a soil
▫ Usually 64 elements
• Organic matter is
comprised of decayed
or decaying plants or
animals
• Porous fraction of soil
contains water and air
▫ Ideal ration is 50:50
SOIL PARTICLES
• Particles are classed according to size
• Coarse (largest particle size)
▫ Sand and gravel
• Medium
▫ Silt
• Fine (smallest particle size)
▫ Clay
SOIL TEXTURE
• Refers to the size of individual
particles
• Soil is a mixture of:
▫ Sand, silt, and clay
• The percentage of each
particle determines the
soil’s ability to drain
and hold water
• Loam: Contains a
percentage of sand, silt, clay,
and organic matter
ORGANIC MATTER
SOIL TEXTURE TRIANGLE
SOIL WATER
• Leaching: Movement of water
and nutrients away from plant
roots
• Capillary water: Held by the
soil and available to plant
through their roots
• Gravitational water: Moves
down and away from the
surface by gravity, not used by
plant roots
• Hygroscopic water: Held so
tightly by soil it is unavailable to
plants
SOIL pH
• pH value: The acidity or alkalinity
of a soil
▫ Plants have a preferred pH range
▫ pH scale = 0 – 14
 Acidic: Below 7
 Alkaline (basic): Above 7
 Neutral: 7
• Soluble: Ability to dissolve
• Microorganisms: Microscopic
plant or animal life that
decompose organic matter in
soil or media
PLANT MEDIUM
• Requirements for a good plant medium:
▫ Moisture and nutrient retention
▫ Good porosity
▫ Provide support for the
plant
▫ Shrinking and swelling
▫ Must be sterilized in
greenhouses
▫ Has to be reproducible
• Porosity: The air space (pores) between solid
particles of soil or medium
• Aeration: Movement of air through the soil
SOIL MEDIA MATERIALS
• Organic matter: Decomposing
remains of plants and animals
▫ Loosens texture and holds water
 Compost: Dark soil of decomposed
organic matter used as a fertilizer
 Peat Moss: Partially decomposed
plant matter that has high water
retention
 Sphagnum Moss: Dehydrated
stems and leaves of acidic bog
plants
 Pine Bark: ¼ inch or smaller pieces
of bark which absorbs nutrients
and releases them slowly
NATURAL SOILS
• Topsoil is the uppermost layer
of soil and consists of:
▫
▫
▫
▫
Air
Water
Minerals
Organic Matter
• The heaviest media material
used is MASONRY OR
PLASTER SAND which has
sharp, coarse particle
INORGANIC MEDIA MATERIALS
• Inorganic matter: Media which
contains no organic (plant or
animal) particles
▫ Perlite: VOLCANIC rock crushed and
heated to 1800 degrees Fahrenheit
 Improves aeration and water holding
capacity
▫ Vermiculite: Mica compound
heated to 2000 degrees Fahrenheit
 Improves moisture retention
▫ Wetting Agents: Chemicals which
change the properties of water or
other liquids
SOILLESS MIXTURES
• Artificial soils are media mixtures where soil
has been replaced with other materials
▫ Developed because of the shortage of good
horticultural-grade soils
▫ Agricultural and roadside soils have been
treated and are harmful to plants
 Pesticides
 Construction materials
 Mineral salts
SOILLESS MIXTURES
• Extra consistency
▫ Maintained from batch to batch
• Easy to use and cost less
• Good drainage and aeration
• Hydroponics: Growing method
which uses a mineral-nutrient
water solution instead of soil
▫ Growing solution can be
easier than soil
▫ Can be expensive to set up and
maintain