Environmental Requirements. Soil n composed of sand, silt, and clay, organic matter, living...

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