Environmental Requirements for Good Plant Growth

1
Environmental Requirements for Good Plant Growth
2
Soil

• composed of sand, silt, and clay, organic matter,
  living organisms, and pore spaces
• classified according to percentage of sand, silt,
  and clay they contain.

3
Ideal Soil Composition

• 45 Mineral Matter
• 25 Water
• 25 Air
• 5 Organic Matter

4
Soil Particles

• vary greatly in size
• sand is the largest
• silt - medium
• clay - smallest

5
Soil Profile

• Consists of 3 basic layers
• Topsoil
• represents depth normally plowed
• Subsoil
• deep rooting plants send roots down into subsoil
• soil bedrock

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Water in Soil

• Gravitational Water
• Soil is unable to hold against the force of
  gravity
• Of little value to plant as it drains away
  quickly
• Seen more in soils with large pore space

7
Water in Soil

• Capillary Water
• Free moving capillary water
• Moves in all directions
• Available capillary water (field capacity)
• Remaining water after capillary movement stops
• Soil surface is dry and water is a thin film
  around soil
• Most important water for plants (half available)
• Unavailable capillary water
• Not available to plants
• Held tightly by soil particles and moved as vapor

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Types of Soil

• Sandy
• Clay
• Loamy

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Sandy Soil

• Silt and clay make up less than 20 by weight
• Drain well
• Little water holding capacity

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Clay Soil

• Must contain at least 30 clay
• Holds more moisture than is good for plants
• Poor drainage

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Loamy Soil

• Most desirable soil
• Equal parts sand, silt and clay
• If more sand, it is sandy loam
• If more clay, clay loam
• If more silt, silty loam

12
Soil less Planting Media Mixes

• Many greenhouses and nurseries use soil less
  mixes
• Advantages of soil less planting media
• Sterile
• Lightweight
• Easier to handle and ship
• Good moisture retention and drainage
• Free of weed seeds

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Soil less Planting Media Mixes

• Disadvantages
• Light weight - pots tip in strong wind
• Minor elements are missing
• Iron
• Sulfur
• Manganese
• Zinc
• Calcium
• Transplants may not adjust well to new media

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Soil less Media Options

• Perlite
• Gray-white material of volcanic origin
• Improve aeration
• Larger particles provide better drainage and
  aeration
• Vermiculite
• Exploded Mica
• Improves aeration
• Neutral pH

15
Plant food and fertilizers

• divided into two groups
• Major elements (macro)
• Nitrogen - N
• Phosphorus - P
• Potassium - K

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Plant requirements

• large amounts of major elements
• relatively small amounts of minor elements

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Commercial fertilizers

• shows or pounds per cwt. (100) of the three
  major elements in large numbers on the container
  or bag.

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Commercial fertilizers

• 5-10-5
• 5 N, 10 P, 5 K
• remaining 80 is filler
• NPK are always listed in that order.

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Soil tests

• determine amount of elements needed for various
  plants.

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Nitrogen

• has most noticeable effect on plants
• encourages above ground vegetative growth
• regulates use of other elements

21
Phosphorous

• held tightly by soil particles
• not easily leached
• effects plants in several ways
• encourage cell division

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Phosphorous

• flowers and seeds dont form without it
• hastens maturity, offsetting quick growth caused
  by N.
• encourage root growth
• makes K more available

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Phosphorous

• increase disease resistance
• improves quality of grain, root and fruit crops
• container plants can be damaged by excess P
• increases soluble salt content of medium
• causes dehydration of roots

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Potassium

• modifies both fast soft growth of N and early
  maturity of P
• is essential

25
Potassium

• increase disease resistance
• encourages healthy root systems
• essential for starch formation
• development of chlorophyll
• efficient use of CO2

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pH

• measure of acidity or alkalinity
• pH scale - runs from 0 - 14
• most plants grow best from 5.6-7.0

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pH

• 7.0 is neutral
• pH of 7 or above is alkaline or basic
• pH below 7 is acidic

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pH

• as numbers decrease, solution becomes more
  acidic.
• As numbers increase, solution becomes more basic
  or alkaline

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pH

• if soil is too acidic, lime is added to raise the
  pH
• if soil is too alkaline, sulfur is added

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Above ground environment

• temperature
• some plants prefer cool weather
• some plants prefer warm weather

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Temperature

• there are temperatures above and below which
  plants stop growth
• generally, plant growth rate increases as temps
  increase up to about 90 degrees

32
Light

• must be present before plants can manufacture
  food
• plants vary in light requirement
• effects flowering

33
Photoperiodism

• response to different periods of day and night in
  terms of growth and maturity

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Photoperiodism

• short day plants
• chrysanthemum and Christmas Cactus
• bloom when days are short and nights are long

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Photoperiodism

• long day plants
• lettuce and radishes
• bloom when days are long and nights are short

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Photoperiodism

• day length indifferent
• do not depend on length of light or darkness
• African Violet and tomato

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Phototropism

• plants appear to grow towards the sun or light
  source

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Humidity

• moisture level of the air
• most plants grow best in 40-80 RH
• Relative Humidity

39
Humidity

• too high humidity may cause the spread of fungus
  diseases

40
Plant diseases and Insects

• reduce production
• lower fruit and vegetable quality

41
Gases and Air Particles

• CO2 is vital to plants for Ps
• Air pollutants can cause damage

42
Air Pollutants

• Sulfur Dioxide - SO2 - from burning coal
• Carbon Monoxide - CO - exhaust from cars

43
Carbon Monoxide

• reduces plant growth
• can kill plants