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