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 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