Download Environmental Requirements for Good Plant Growth

Environmental Requirements for
Good Plant Growth
Unit 4
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
The Underground Environment
• Rizosphere – 24 inches of soil just below
the earth’s surface
• Soil – Made of sand, silt, and clay, organic
matter, living organisms, and pore spaces
with water and air
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
Capillary Water
• Held against the force of gravity
• Held in small pore spaces of soil as a thin
film of particles
Free moving Capillary Water
• Moves in all directions in the soil
• Soil must be saturated in low levels for
water to move upward
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
Unavailable capillary water
• Not available to plants
• Held tightly as molecular film around soil
particles
• Can only be moved as vapor