Understanding Growing Media Components

Lesson 4 - 2

Next Generation Science/Common Core Standards Addressed!

• WHST.9‐12.7 Conduct short as well as more sustained research projects to answer a question (including a self generated question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation. (HS‐LS1‐3)

• HSSIC. B.6 Evaluate reports based on data. (HS‐LS2‐6)

Bell Work!

1. Describe the components of soil.

2. List the components of a soilless mix.

3. Compare and contrast the use of soil versus a soilless mix.

Terms

• Clay• Inorganic• Loam• Mineral matter• Organic matter• Pasteurization• Peat Moss• Perlite

• Sand• Silt• Soil• Soil Amendment• Soilless Mix• Sterilization• Vermiculite

Don’t Judge a Soil by It’s Label!

• Never look gift soil in the label!

• What is in a soil?

• Don’t count your plants before they germinate!

What is Soil?

• Soil – outer layer of the earth that supports life.

• Recipe for Soil– 1cu. Air– 1cu. Water– 1 4/5 cu. Mineral matter– 1 tbl. organic matter– Mix thoroughly and let stand.

Soil is:

• 25% air

• 25% water

• 45% mineral matter

• 5% organic matter

Soil Composition

Mineral Matter• Non-living substances generally thought

of as weathered rock.• Soil particles have 3 general sizes• Sand – largest and increases drainage

(feels gritty)• Silt – medium size and gives a talc feel• Clay – smallest and higher water holding

capacity, feels slick.

Soil Particle Comparison

Organic Matter• Organic matter is living or dead plants

and animals.

• Organic matter is necessary for plant growth because of its high nutrient content.

• Higher O.M. generally increases productivity.

What’s in a soilless mix?

• A soilless mix is a combination of organic and inorganic substances that provide sufficient support for plant growth.

• A soilless mix does not contain topsoil.

Common components in a soilless mix are:

• Peat moss is plant material that originates in bogs. Peat moss has great moisture and nutrient holding capacity.

• Perlite is white in color and comes from heat-treated lava rock. Perlite is used in the soil mix to aerate the soil.

Components Continued:• Vermiculite comes from the mineral

mica and is shiny brown in color. It has high moisture holding capacity and is very lightweight.

• Choir is fibers from coconut hulls which is hollow and aids in water and air holding while remaining lightweight.

Components Continued:

• Sand large soil particles used to reduce overall water holding capacity

• Amendments are added to change the air / water relationship of a mix while reducing the cost

• Wetting Agents are soaps used to aid water uptake of the dry mix. Also aids in rewetting.

The advantages of a soilless mix are:

1. The mix is uniform. It does not vary in components, texture, or nutrients.

2. The mix is sterile. Sterilization is a process that eliminates all disease organisms, in-sects, or weed seeds. Soil mixes often contain these items and a grower who chooses to use a soil mix must pasteurize his or her soil before using it. Pasteurization is the process of heating soil to kill harmful diseases, weed seeds, and insects.

The advantages of a soilless mix are:

3. Soilless mixes can be manipulated to improve the drainage and moisture holding capacity of the mix.

4. A grower can personally mix the combination of components exactly to what he or she needs for their particular crop.

5. Soilless mixes are easier to ship and move because they are lightweight.

The disadvantages of a soilless mix are:

1. Fertilizers often need to be added more frequently to the mix because the mixes are lacking in minor plant food elements. Soil contains and holds many of these minor nutrients.

2. When plants are grown outdoors, the wind can blow dry pots over because the mix is very light.

The disadvantages of a soilless mix are:

3. It is sometimes difficult to transplant a plant from a soil mix to a soilless one. The roots often will not grow into the new media and the plant will die because it can not absorb any moisture.

4. There is a cost to the media

REVIEW

What are the ingredients of soil?

• Air

• Water

• O.M.

• Mineral Matter

What are the sizes of soil particles?

• Sand

• Silt

• Clay

What are the materials used for soilless mixes?

• Peat

• Perlite

• Vermiculite

• Choir

• Amendments – bark, rice hulls, …

• Sand

• Wetting Agents

What are the advantages of mixes?

• Uniform

• Sterile

• Light

• Amendable

What are the disadvantages of mixes?

• Light

• Need nutrients

• Cost

• Transplant issues

The End