Environmental Requirements
Mar 26, 2015
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
n vary greatly in sizen sand is the largestn silt - mediumn clay - smallest
Clay
n particles hold moisture and plant food elements more effectively than larger particles.
Soil Profile
n consists of 3 basic layersn topsoiln subsoiln soil bedrock
Topsoil
n represents depth normally plowed
Subsoil
n deep rooting plants send roots down into subsoil
Sandy Soil
n silt and clay make up less than 20% by weight
n drain welln little water holding capacity
Clayey Soil
n must contain at least 30% clay
n holds more moisture than is good for plants
n poor drainage
Loamy Soil
n most desirable soiln equal parts sand, silt and
clay
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
n drainage tilesn raise planting bedsn ditching between beds
Moisture retention
n adding organic matter (o.m.)n sources of o.m.n animal manuren green manure - crop grown
and plowed under to improve the soil
Sources of O.M.
n peat mossn sawdustn mulches - compost or wood
chips
Mulches
n placed on the surface to help retain moisture
n reduce runoff and evaporation
n reduce weeds
Moisture retention
n irrigation
Fertilizing
n fertilize according to soil test results
Diseases
n plant resistant varietiesn chemicalsn soil pasteurization
–heat to 180 degrees F for 30 minutes.
Nutritional deficiencies
n show on leaves of plantsn Nitrogen - pale green leavesn Phosphorus - purple color on
underside of leaves
Planting Media Mixes
n Soil less mixesn advantages include :
uniformity - doesn’t vary in pH, fertility or texture
advantages
n sterilen lightweightn good moisture retention and
drainagen free of weed seeds
disadvantages
n light weight - pots tip in strong wind
n minor elements are missingn transplants may not adjust
well to new media
Content of mixes
n perliten improve aerationn volcanic origin
Vermiculite
n exploded Mican improves aeration
Plant food and fertilizersn divided into two groupsn Major elements (macro)n Nitrogen - Nn Phosphorus - Pn Potassium - K
minor elements (micro)
n Calcium - Can Magnesium - mgn Sulfur - Sn Iron - Fe
minor elements (micro)
n Manganese - Mnn Boron - Bn Copper - Cun Zinc - Zn
Plant requirements
n large amounts of major elements
n relatively small amounts of minor elements
Commercial fertilizers
n shows % or pounds per cwt. (100#) of the three major elements in large numbers on the container or bag.
Commercial fertilizers
n 5-10-5n 5% N, 10% P, 5% Kn remaining 80% is fillern NP&K are always listed in
that order.
Soil tests
n determine amount of elements needed for various plants.
Nitrogen
n generally purchased in one of four forms
n Nitrate of sodan ammonium nitrate
Nitrogen
n ammonium sulfaten urea formaldehyde
Nitrogen
n has most noticeable effect on plants
n encourages above ground vegetative growth
n regulates use of other elements
Too much N
n lower disease resistancen weaken stem because of
long soft growthn lower fruit quality
Too much N
n delay maturityn increase winter damage to
plants
Not enough N
n yellow or light green colorn stunted root and top growth
N lost easily from soil
n 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
Don’t use excess N
n quickly lost through leachingn can damage plants
Phosphorous
n held tightly by soil particlesn not easily leached
Phosphorous
n effects plants in several ways
n encourage cell division
Phosphorous
n flowers and seeds don’t form without it
n hastens maturity, offsetting quick growth caused by N.
Phosphorous
n encourage root growthn makes K more availablen increase disease resistancen improves quality of grain,
root and fruit crops
Phosphorous
n container plants can be damaged by excess P
n increases soluble salt content of medium
n causes dehydration of roots
Phosphorous
n Insufficient Pn purple color on underside of
leafn reduced flower fruit and
seed production
Insufficient P
n susceptibility to cold injuryn susceptibility to plant
diseasesn poor quality fruit and seeds
Potassium
n modifies both fast soft growth of N and early maturity of P
n is essential
Potassium
n increase disease resistancen encourages healthy root
systemsn essential for starch formation
Potassium
n development of chlorophylln efficient use of CO2
Insufficient K
n leaves appear dry and scorched with irregular yellow areas on the surface
Lime
n CaCO3- Calcium Carbonaten acts as a plant foodn affects soil acidityn soil acidity affects availability
of plant food elements
Lime
n furnishes Calcium
pH
n measure of acidity or alkalinity
n pH scale - runs from 0 - 14n most plants grow best from
5.6-7.0
pH
n 7.0 is neutraln pH of 7 or above is alkaline
or basicn pH below 7 is acidic
pH
n as numbers decrease, solution becomes more acidic.
n As numbers increase, solution becomes more basic or alkaline
pH
n if soil is too acidic, lime is added to raise the pH
n if soil is too alkaline, sulfur is added
Above ground environmentn temperaturen some plants prefer cool
weathern some plants prefer warm
weather
Temperature
n there are temperatures above and below which plants stop growth
n generally, plant growth rate increases as temps increase up to about 90 degrees
Light
n must be present before plants can manufacture food
n plants vary in light requirement
n effects flowering
Photoperiodism
n response to different periods of day and night in terms of growth and maturity
Photoperiodism
n short day plantsn chrysanthemum and
Christmas Cactusn bloom when days are short
and nights are long
Photoperiodism
n long day plantsn lettuce and radishesn bloom when days are long
and nights are short
Photoperiodism
n day length indifferentn do not depend on length of
light or darknessn African Violet and tomato
Phototropism
n plants appear to grow towards the sun or light source
Humidity
n moisture level of the airn most plants grow best in 40-
80% RHn Relative Humidity
Humidity
n too high humidity may cause the spread of fungus diseases
Plant diseases and Insectsn reduce productionn lower fruit and vegetable
quality
Gases and Air Particles
n CO2 is vital to plants for Psn Air pollutants can cause
damage
Air Pollutants
n Sulfur Dioxide - SO2 - from burning coal
n Carbon Monoxide - CO - exhaust from cars
Carbon Monoxide
n reduces plant growthn can kill plants