Environmental Requirements for Good Plant Growth

1
Environmental Requirements for Good Plant Growth

• Unit 4

2
Objectives

• List 4 factors that affect the roots of plants
• Describe the differences between clay, sandy,and
  loamy soils and identify a sample of each
• Compose a balanced fertilizer program for 1 plant
  that is grown commercially in the area
• List 4 aboveground requirements for good plant
  growth
• List the 3 major plant food elements and 2
  functions of each

3
The Underground Environment

• Rizosphere 24 inches of soil just below the
  earths surface
• Soil Made of sand, silt, and clay, organic
  matter, living organisms, and pore spaces with
  water and air

4
Types of Water in the Soil

• Gravitational Water Soil is unable to hold this
  water against the force of gravity
• Become part of the groundwater or drains away in
  streams
• Larger soil pore spaces causes faster loss of
  water

5
Capillary Water

• Held against the force of gravity
• Held in small pore spaces of soil as a thin film
  of particles

6
Free moving Capillary Water

• Moves in all directions in the soil
• Soil must be saturated in low levels for water to
  move upward

7
Available Capillary water

• AKA Field Capacity
• The water left after capillary movement stops
• Water does not continue to move through the soil
  at this point
• Plant roots must continue to move in search of
  the soil
• Soil surrounding them is dried out by rot
  absorption
• Roots will not grow in air-dry soil where no
  moisture is present
• Field capacity is high in heavy soils (clay
  particles)
• More surface are smaller pore spaces for water
  to cling to
• Plants can use about ½ this water

8
Unavailable capillary water

• Not available to plants
• Held tightly as molecular film around soil
  particles
• Can only be moved as vapor