environmental requirements soil composed of sand, silt, and clay, organic matter, living organisms,...

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

Carbon Monoxide

reduces plant growthcan kill plants