Transcript Environmental Requirements

Environmental
Requirements
Soil
n
composed of sand, silt, and
clay, organic matter, living
organisms, and pore spaces
Soil
n
classified according to
percentage of sand, silt, and
clay they contain.
Soil Particles
vary greatly in size
n sand is the largest
n silt - medium
n clay - smallest
n
Clay
n
particles hold moisture and
plant food elements more
effectively than larger
particles.
Soil Profile
consists of 3 basic layers
n topsoil
n subsoil
n soil bedrock
n
Topsoil
n
represents depth normally
plowed
Subsoil
n
deep rooting plants send
roots down into subsoil
Sandy Soil
silt and clay make up less
than 20% by weight
n drain well
n little water holding capacity
n
Clayey Soil
must contain at least 30%
clay
n holds more moisture than is
good for plants
n poor drainage
n
Loamy Soil
most desirable soil
n equal parts sand, silt and
clay
n
Soil Improvement
n
Drainage
– change soil structure
–add organic matter to
encourage earth worms
Worms
n
their tunnels and castings
result in better soil structure
- aggregation - clinging
together
Drainage
drainage tiles
n raise planting beds
n ditching between beds
n
Moisture retention
adding organic matter (o.m.)
n sources of o.m.
n animal manure
n green manure - crop grown
and plowed under to
improve the soil
n
Sources of O.M.
peat moss
n sawdust
n mulches - compost or wood
chips
n
Mulches
placed on the surface to help
retain moisture
n reduce runoff and
evaporation
n reduce weeds
n
Moisture retention
n
irrigation
Fertilizing
n
fertilize according to soil test
results
Diseases
plant resistant varieties
n chemicals
n soil pasteurization
n
–heat to 180 degrees F for 30
minutes.
Nutritional deficiencies
show on leaves of plants
n Nitrogen - pale green leaves
n Phosphorus - purple color on
underside of leaves
n
Planting Media Mixes
Soil less mixes
n advantages include :
uniformity - doesn’t vary in
pH, fertility or texture
n
advantages
sterile
n lightweight
n good moisture retention and
drainage
n free of weed seeds
n
disadvantages
light weight - pots tip in
strong wind
n minor elements are missing
n transplants may not adjust
well to new media
n
Content of mixes
perlite
n improve aeration
n volcanic origin
n
Vermiculite
exploded Mica
n improves aeration
n
Plant food and
fertilizers
divided into two groups
n Major elements (macro)
n Nitrogen - N
n Phosphorus - P
n Potassium - K
n
minor elements (micro)
Calcium - Ca
n Magnesium - mg
n Sulfur - S
n Iron - Fe
n
minor elements (micro)
Manganese - Mn
n Boron - B
n Copper - Cu
n Zinc - Zn
n
Plant requirements
large amounts of major
elements
n relatively small amounts of
minor elements
n
Commercial fertilizers
n
shows % or pounds per cwt.
(100#) of the three major
elements in large numbers
on the container or bag.
Commercial fertilizers
5-10-5
n 5% N, 10% P, 5% K
n remaining 80% is filler
n NP&K are always listed in
that order.
n
Soil tests
n
determine amount of
elements needed for various
plants.
Nitrogen
generally purchased in one
of four forms
n Nitrate of soda
n ammonium nitrate
n
Nitrogen
ammonium sulfate
n urea formaldehyde
n
Nitrogen
has most noticeable effect
on plants
n encourages above ground
vegetative growth
n regulates use of other
elements
n
Too much N
lower disease resistance
n weaken stem because of
long soft growth
n lower fruit quality
n
Too much N
delay maturity
n increase winter damage to
plants
n
Not enough N
yellow or light green color
n stunted root and top growth
n
N lost easily from soil
leaching - being filtered
down through soil with water
n not held by soil particles,
dissolved in water
n O.M. holds insoluble N for
slow release
n
Don’t use excess N
quickly lost through leaching
n can damage plants
n
Phosphorous
held tightly by soil particles
n not easily leached
n
Phosphorous
effects plants in several
ways
n encourage cell division
n
Phosphorous
flowers and seeds don’t form
without it
n hastens maturity, offsetting
quick growth caused by N.
n
Phosphorous
encourage root growth
n makes K more available
n increase disease resistance
n improves quality of grain,
root and fruit crops
n
Phosphorous
container plants can be
damaged by excess P
n increases soluble salt
content of medium
n causes dehydration of roots
n
Phosphorous
Insufficient P
n purple color on underside of
leaf
n reduced flower fruit and
seed production
n
Insufficient P
susceptibility to cold injury
n susceptibility to plant
diseases
n poor quality fruit and seeds
n
Potassium
modifies both fast soft
growth of N and early
maturity of P
n is essential
n
Potassium
increase disease resistance
n encourages healthy root
systems
n essential for starch formation
n
Potassium
development of chlorophyll
n efficient use of CO2
n
Insufficient K
n
leaves appear dry and
scorched with irregular
yellow areas on the surface
Lime
CaCO3- Calcium Carbonate
n acts as a plant food
n affects soil acidity
n soil acidity affects availability
of plant food elements
n
Lime
n
furnishes Calcium
pH
measure of acidity or
alkalinity
n pH scale - runs from 0 - 14
n most plants grow best from
5.6-7.0
n
pH
7.0 is neutral
n pH of 7 or above is alkaline
or basic
n pH below 7 is acidic
n
pH
as numbers decrease,
solution becomes more
acidic.
n As numbers increase,
solution becomes more
basic or alkaline
n
pH
if soil is too acidic, lime is
added to raise the pH
n if soil is too alkaline, sulfur is
added
n
Above ground
environment
temperature
n some plants prefer cool
weather
n some plants prefer warm
weather
n
Temperature
there are temperatures
above and below which
plants stop growth
n generally, plant growth rate
increases as temps increase
up to about 90 degrees
n
Light
must be present before
plants can manufacture food
n plants vary in light
requirement
n effects flowering
n
Photoperiodism
n
response to different periods
of day and night in terms of
growth and maturity
Photoperiodism
short day plants
n chrysanthemum and
Christmas Cactus
n bloom when days are short
and nights are long
n
Photoperiodism
long day plants
n lettuce and radishes
n bloom when days are long
and nights are short
n
Photoperiodism
day length indifferent
n do not depend on length of
light or darkness
n African Violet and tomato
n
Phototropism
n
plants appear to grow
towards the sun or light
source
Humidity
moisture level of the air
n most plants grow best in 4080% RH
n Relative Humidity
n
Humidity
n
too high humidity may cause
the spread of fungus
diseases
Plant diseases and
Insects
reduce production
n lower fruit and vegetable
quality
n
Gases and Air Particles
CO2 is vital to plants for Ps
n Air pollutants can cause
damage
n
Air Pollutants
Sulfur Dioxide - SO2 - from
burning coal
n Carbon Monoxide - CO exhaust from cars
n
Carbon Monoxide
reduces plant growth
n can kill plants
n