environmental requirements soil composed of sand, silt, and clay, organic matter, living organisms,...
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Environmental Environmental RequirementsRequirements
Soil
composed of sand, silt, and clay, organic matter, living organisms, and pore spaces
Soil
classified according to percentage of sand, silt, and clay they contain.
Soil Particles
vary greatly in sizesand is the largestsilt - mediumclay - smallest
Clay
particles hold moisture and plant food elements more effectively than larger particles.
Soil Profile
consists of 3 basic layerstopsoilsubsoilsoil bedrock
Topsoil
represents depth normally plowed
Subsoil
deep rooting plants send roots down into subsoil
Sandy Soil
silt and clay make up less than 20% by weight
drain welllittle water holding capacity
Clayey Soil
must contain at least 30% clayholds more moisture than is
good for plantspoor drainage
Loamy Soil
most desirable soilequal parts sand, silt and clay
Soil Improvement
Drainage – change soil structure–add organic matter to encourage
earth worms
Worms
their tunnels and castings result in better soil structure - aggregation - clinging together
Drainage
drainage tilesraise planting bedsditching between beds
Moisture retentionadding organic matter (o.m.)sources of o.m.animal manuregreen manure - crop grown and
plowed under to improve the soil
Sources of O.M.
peat mosssawdustmulches - compost or wood
chips
Mulches
placed on the surface to help retain moisture
reduce runoff and evaporationreduce weeds
Moisture retention
irrigation
Fertilizing
fertilize according to soil test results
Diseases
plant resistant varietieschemicalssoil pasteurization
–heat to 180 degrees F for 30 minutes.
Nutritional deficiencies
show on leaves of plantsNitrogen - pale green leavesPhosphorus - purple color on
underside of leaves
Planting Media Mixes
Soil less mixesadvantages include :
uniformity - doesn’t vary in pH, fertility or texture
advantages
sterilelightweightgood moisture retention and
drainagefree of weed seeds
disadvantages
light weight - pots tip in strong wind
minor elements are missingtransplants may not adjust well
to new media
Content of mixes
perliteimprove aerationvolcanic origin
Vermiculite
exploded Micaimproves aeration
Plant food and fertilizers
divided into two groupsMajor elements (macro)Nitrogen - NPhosphorus - PPotassium - K
minor elements (micro)
Calcium - CaMagnesium - mgSulfur - SIron - Fe
minor elements (micro)
Manganese - MnBoron - BCopper - CuZinc - Zn
Plant requirements
large amounts of major elements
relatively small amounts of minor elements
Commercial fertilizers
shows % or pounds per cwt. (100#) of the three major elements in large numbers on the container or bag.
Commercial fertilizers
5-10-55% N, 10% P, 5% Kremaining 80% is fillerNP&K are always listed in that
order.
Soil tests
determine amount of elements needed for various plants.
Nitrogen
generally purchased in one of four forms
Nitrate of sodaammonium nitrate
Nitrogen
ammonium sulfateurea formaldehyde
Nitrogen
has most noticeable effect on plants
encourages above ground vegetative growth
regulates use of other elements
Too much N
lower disease resistanceweaken stem because of long
soft growthlower fruit quality
Too much N
delay maturityincrease winter damage to
plants
Not enough N
yellow or light green colorstunted root and top growth
N lost easily from soilleaching - being filtered down
through soil with waternot held by soil particles,
dissolved in waterO.M. holds insoluble N for
slow release
Don’t use excess N
quickly lost through leachingcan damage plants
Too much N!
Phosphorous
held tightly by soil particlesnot easily leached
Phosphorous
effects plants in several waysencourage cell division
Phosphorous
flowers and seeds don’t form without it
hastens maturity, offsetting quick growth caused by N.
Phosphorous
encourage root growthmakes K more availableincrease disease resistanceimproves quality of grain, root
and fruit crops
Phosphorous
container plants can be damaged by excess P
increases soluble salt content of medium
causes dehydration of roots
Phosphorous
Insufficient Ppurple color on underside of
leafreduced flower fruit and seed
production
Insufficient P
susceptibility to cold injurysusceptibility to plant diseasespoor quality fruit and seeds
Potassium
modifies both fast soft growth of N and early maturity of P
is essential
Potassium
increase disease resistanceencourages healthy root
systemsessential for starch formation
Potassium
development of chlorophyllefficient use of CO2
Insufficient K
leaves appear dry and scorched with irregular yellow areas on the surface
LimeCaCO3- Calcium Carbonateacts as a plant foodaffects soil aciditysoil acidity affects availability
of plant food elements
Lime
furnishes Calcium
pH
measure of acidity or alkalinitypH scale - runs from 0 - 14most plants grow best from
5.6-7.0
pH
7.0 is neutralpH of 7 or above is alkaline or
basicpH below 7 is acidic
pH
as numbers decrease, solution becomes more acidic.
As numbers increase, solution becomes more basic or alkaline
pH
if soil is too acidic, lime is added to raise the pH
if soil is too alkaline, sulfur is added
Above ground environment
temperaturesome plants prefer cool
weathersome plants prefer warm
weather
Temperaturethere are temperatures above
and below which plants stop growth
generally, plant growth rate increases as temps increase up to about 90 degrees
Light
must be present before plants can manufacture food
plants vary in light requirementeffects flowering
Photoperiodism
response to different periods of day and night in terms of growth and maturity
Photoperiodism
short day plantschrysanthemum and Christmas
Cactusbloom when days are short and
nights are long
Photoperiodism
long day plantslettuce and radishesbloom when days are long and
nights are short
Photoperiodism
day length indifferentdo not depend on length of
light or darknessAfrican Violet and tomato
Phototropism
plants appear to grow towards the sun or light source
Humidity
moisture level of the airmost plants grow best in 40-
80% RHRelative Humidity
Humidity
too high humidity may cause the spread of fungus diseases
Plant diseases and Insects
reduce productionlower fruit and vegetable
quality
Gases and Air Particles
CO2 is vital to plants for PsAir pollutants can cause
damage
Air Pollutants
Sulfur Dioxide - SO2 - from burning coal
Carbon Monoxide - CO - exhaust from cars
