Potting Soil Mix

From the University of Arizona Master Gardener's Manual.
http://ag.arizona.edu/pubs/garden/mg/indoor/media.html

Potting mix:

• 1 bushel shredded peat moss
• 2 bushels perlite or vermiculite
• 1/2 cup finely ground agricultural lime
• 1/3 cup 20% superphosphate
• 1/2 cup 8-8-8 or similar analysis mixed fertilizer
• 1 level teaspoon chelated iron

I believe I tailored this down correctly to a size most can deal with:

• 1.5 gallons shredded peat moss
• 1.5 gallons perlite
• 1.5 gallons vermiculite
• 1.5 Tablespoons garden lime
• 1 Tablespoon superphosphate
• 1.5 Tablespoons 8-8-8 fertilizer
• pinch chelated iron

I personally add "Bio-tone" by Espoma plus use more of organic "Garden-tone" 3-4-4 by Espoma since it is slow release organic fertilizer. Commercial potting mixes are now including composted pine bark, but I cannot find this anywhere locally, yet.

"Media
The potting soil, or media in which a plant grows, must be of good quality. It should be porous for root aeration and drainage, but also capable of water and nutrient retention. Most commercially prepared mixes are termed artificial, which means they contain no soil. High-quality artificial mixes generally contain slow-release fertilizers, which take care of a plant’s nutritional requirements for several months. However, commercial mixes are often misleading as to content, and unsatisfactory for proper plant health. It is better to mix your own if possible.

Preparing Artificial Mixes
Artificial mixtures can be prepared with a minimum of difficulty. Most mixes contain a combination of organic matter, such as peat moss or ground pine bark, and an inorganic material, like washed sand, vermiculite, or perlite. Materials commonly used for indoor plants are the peat-lite mixtures, consisting of peat moss and either vermiculite or perlite. Here are some comments concerning the ingredients for these mixes.

Peat Moss is readily available baled or bagged; sphagnum peat moss is recommended. Such materials as Michigan peat, peat humus, and native peat are usually too decomposed to provide necessary structural and drainage characteristics. Most sphagnum peat moss is acid in reaction, with a pH ranging from 4.0 to 5.0 It usually has a very low fertility level. Do not shred sphagnum peat moss too finely.

Vermiculite is a sterile, lightweight, mica product. When mica is heated to approximately 1800° F, its platelike structure expands. Vermiculite will hold large quantities of air, water, and nutrients needed for plant growth. Its pH is usually in the 6.5 to 7.2 range. Vermiculite is available in four particle sizes. For horticultural mixes, sizes 2 or 3 are generally used. If at all possible, the larger-sized particles should be used, since they give much better soil aeration. Vermiculite is available under a variety of trade names.

Perlite is a sterile material produced by heating volcanic rock to approximately 1800° F. The result is a very lightweight, porous material that is white in color. Its principal value in soil mixtures is aeration. It does not hold water and nutrients as well as vermiculite. The pH is usually between 7.0 and 7.5. Perlite can cause fluoride burn on some foliage plants, usually on the tips of the leaves. The burn progresses from the tip up into the leaf. Fluoride burns can be prevented by adding 1 1/2 times the recommended amount of lime when mixing the soil."


 Below:
Adapted and excerpted from:
George Kuepper, "Potting Mixes for Certified Organic Production," National Sustainable Agriculture Information Service (rev. 10/2010). 

More potting soil recipes. This was sent in the Florida Master Gardener email.

"Recipes
When making your own potting mix, working from a recipe is a good idea to start. Once you begin experimenting with your own blends, try small test batches to evaluate the mix’s quality. See the recipes below to get started making your own potting mixes.

Foliage Plants
2 parts peat; 1 part perlite; 1 part coarse sand
OR
1 part peat; 1 part pine bark; 1 part coarse sand

Succulents
2 parts soil; 1 part peat moss; 1 part perlite; 1 part coarse sand

Bromeliads
1 part peat; 1 part bark; 1 part coarse sand

Seedlings
2 parts compost; 2 parts peat moss; 1 part vermiculite (pre-wet)

Soil-Based Mix
This mix is heavier than peat-based mixes, but it has good drainage. Vermiculite or perlite can be used for sand.
1/3 compost; 1/3 topsoil; 1/3 sand

Blocking Mix
This mixture is for use as soil blocks for seedling/transplant growing. Mix all ingredients together thoroughly. Ingredients can be measured with a standard 10-quart bucket.
30 quarts brown peat
20 quarts sand or perlite
20 quarts compost
10 quarts soil
3 cups base fertilizer (equal parts blood meal, colloidal phosphate, greensand)
½ cup lime"