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 earth’s 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