1. Soil & Soil Mediums
April 4, 2014

2. Soil
Soil is made up of sand, silt, clay, organic matter, living organisms, and pore spaces that hold water and air.
Soils vary greatly in composition based on their origin
Form as a result of rock breaking down over thousands of years
Form as a result of material deposited by wind or water
Soils are classified according to the percentage of sand, silt, and clay contained in the mixture
Soil particles vary greatly in size
Sand – silt – clay

3. Sandy Soil Sandy or light soil
In sandy soils, silt & clay make up less than 20% of the material
Soils have large pore space
Drain well because gravity forces water down through the pores
Little water holding capacity
Little capacity to hold plant nutrients
Warm up very quickly in the summer

4. Silt Soils Comprised of intermediate sized particles
Fairly fertile soils
Well-drained
But hold more moisture than sandy soils
Easily compacted

5. Clay Soils Heavy soil Poor drainage and aeration capabilities
Small poor space
Water and air have a hard time passing through
Water is held in the soil
Some clay tends to be good for plant growth because it holds moisture & nutrients
Takes a long time to warm up in the summer but dries out in high heat
Compact and become extremely hard

6. Loams Most desirable soil type Equal parts of sand, silt, and clay
Well-drained soils
Optimum moisture & nutrient holding capacity capacity

7. Soil Mediums

8. Planting Mediums
More and more growers are using planting mixes that contain little, if any soil
Advantages
The mix is uniform (does not vary in pH or texture)
The mix is sterile (containing no disease organisms, insects, or weed seeds)
Lighter in weight and easier to handle
Good moisture retention & drainage
Disadvantages
Needs to be stored
Some plants prefer natural soils
Added expense

9. Perlite Gray-white mineral of volcanic origin Used to improve aeration
Larger particles

10. PeaT MOSS
Partially decomposed vegetation that has been preserved underwater
Originates in marshes, bogs, or swamps
It has a VERY high moisture holding capacity

11. Vermiculite Made from mica (mineral) particles Very light material
Spongy
Neutral pH
pH scale is from 0…...7…..14
When vermiculite is heated it expands
High moisture holding capacity

12. Rockwool Manmade fibers made from natural or synthetic minerals
Used in hydroponic applications
Cultivating plants in mineral solutions (water with added minerals)
Has limited water holding capacity which allows water to circulate through the medium