Potting Mixes for Certified Organic Production

[dankohzee]

The following is a list of potting mixes that meet "Certified Organic" specifications:

Classic soil-based mix

1/3 mature compost or leaf mold, screened
1/3 garden topsoil
1/3 sharp sand
Note: This mix is heavier than modern peat mixes, but still has good drainage. Compost promotes a healthy soil mix that can reduce root diseases. Vermiculite or perlite can be used instead of sand. Organic fertilizer can be added to this base.

Organic substitute for Cornell Mix

½ cu. yd. sphagnum peat
½ cu. yd. vermiculite
10 lbs. bonemeal
5 lbs. ground limestone
5 lbs. bloodmeal

The following four recipes were found in the March-April 1989 issue of the Ozark Organic Growers Association Newsletter. The formulas are credited to the Farm and Garden Project at the University of California—Santa Cruz.
Seedling mix for styrofoam seedling flats

2 parts compost
2 parts peat moss
1 part vermiculite, pre-wet

Sowing mix

5 parts compost
4 parts soil
1–2 parts sand
1–2 parts leaf mold, if available
1 part peat moss, pre-wet and sifted
Note: All ingredients are sifted through a 1/4-inch screen. For every shovelful of peat, add two tablespoons of lime to offset the acidity.

Prick-out mix for growing seedlings to transplant size

6 parts compost
3 parts soil
1–2 parts sand
1–2 parts aged manure
1 part peat moss, pre-wet and sifted
1–2 parts leaf mold, if available
1 6” pot bone meal

Special potting mix

1 wheelbarrow-load sifted soil
1 wheelbarrow-load aged manure
1 wheelbarrow-load sifted old flat mix
5 shovelfuls sifted peat
2 4” pots bone meal
2 4” pots trace mineral powder
2 4” pots blood meal

The following recipes are taken from John Jeavons's How to Grow More Vegetables…, Ten Speed Press, Berkeley, CA.
Classic planting mix

One part each by weight:
compost (sifted, if possible)
sharp sand
turf loam (made by composting sections of turf grass grown in good soil)
Note: the mixture should be placed in growing flats on top of a 1/8-inch layer of oak leaf mold to provide drainage. Crushed eggshells should be placed between the leaf mold and compost for calcium-loving plants like cabbages and carnations.

Simple soil flat mix

Equal parts by volume:
compost
bed soil (saved from a biointensive production bed during double-digging process)

The next three formulas are credited to the 1992 NOFA-NY Organic Farm Certification Standards.
Classic formula for horticultural potting mix

1/3 mature compost or leaf mold, sieved
1/3 fine garden loam
1/3 coarse sand (builder's sand)

Sterile peat-lite mix

shredded sphagnum peat moss 0.5 cu. yd.
horticultural vermiculite 0.5 cu. yd.
dried blood (12% N) 5 lbs.
steamed bonemeal 10 lbs.
ground limestone 5 lbs.

Recipe for soil blocks

black peat with ½ cup lime 20 qts.
sand or calcined clay 20 qts.
regular peat with 1 cup greensand,1 cup colloidal phosphate, & 1 cup bloodmeal 20 qts.
soil 10 qts.
compost 10 qts.
Note: all bulk ingredients should be sifted through a ½” screen.

The following four recipes are credited to Eliot Coleman. The first was published in the Winter 1994 issue of NOFA-NJ Organic News, in an article by Emily Brown-Rosen. The remaining three are adapted from Coleman's book The New Organic Grower (see .
Organic potting mix

1 part sphagnum peat
1 part peat humus (short fiber)
1 part compost
1 part sharp sand (builder's)
to every 80 qts. of this add:
1 cup greensand
1 cup colloidal phosphate
1½ to 2 cups crabmeal, or blood meal
½ c. lime

Blocking mix recipe

3 buckets (standard 10-qt. bucket) brown peat
½ cup lime (mix well)
2 buckets coarse sand or perlite
3 cups base fertilizer (blood meal, colloidal phosphate, and greensand mixed together in equal parts)
1 bucket soil
2 buckets compost
Mix all ingredients together thoroughly. Coleman does not sterilize potting soils; he believes that damp-off and similar seedling problems are the result of overwatering, lack of air movement, not enough sun, overfertilization, and other cultural mistakes.

Blocking mix recipe for larger quantities

30 units brown peat
1/8 unit lime
20 units coarse sand or perlite
¾ unit base fertilizer (blood meal, colloidal phosphate, and greensand mixed together in equal parts)
10 units soil
20 units compost

Mini-block recipe

16 parts brown peat
¼ part colloidal phosphate
¼ part greensand
4 parts compost (well decomposed)
Note: If greensand is unavailable, leave it out. Do not substitute a dried seaweed product in this mix.

The next recipe and details come from John Greenier, of Stoughton, Wisconsin. They were published in the January 1996 issue of Growing for Market.
Seedling mix for soil blocks or seedling flats

Sphagnum peat moss: 2 3-gal. buckets
Lime: ¼ c.
Fertility mix: 1½ cups
Colloidal (rock) phosphate: 2 cups
Greensand: 2 cups
Blood meal: 2 cups
Bone meal: ½ cup
Kelp meal: ¼ cup
Vermiculite: 1½ buckets
Compost: 1½ buckets
Directions for mixing

• Add peat to cement mixer or mixing barrel.
• Spread the lime and fertility mix over the peat.
• Mix these ingredients thoroughly.
• Add the compost and vermiculite and mix well again. When done, examine the distribution of vermiculite to ensure that it has been mixed in evenly.

Note that all bulk ingredients should be screened through 1/4 -inch hardware cloth. Well matured, manure-based compost should be used (avoid poultry manure and wood-chip bedding).

The next two recipes were published in the September 1990 issue of Greenhouse Manager in an article entitled “Recipes for Success in Media Mixes,” by Kathy Z. Peppler.
Growing mix for packs

40 percent topsoil
40 percent Canadian-type Michigan peat
20 percent perlite
5 pounds lime per cubic yard
3 pounds dolomitic lime per cubic yard
Note: The topsoil and peat are sterilized early in the fall, then brought indoors to be blended with the other ingredients and stored inside.

Growing mixes for pots and baskets

30 percent topsoil
60 percent peat
10 percent perlite
5 pounds lime per cubic yard
3 pounds dolomitic lime per cubic yard
Note: The handling of this pot mix is the same as for pack mix.

The following recipes and instructions are from a workshop entitled “Getting Started in Organic Market Gardening,” which was offered as part of the March 2001 “Organic University” program sponsored by Midwest Organic and Sustainable Education Services (MOSES) in conjunction with its Upper Midwest Organic Conference. The first is credited to Tricia Bross, Luna Circle Farm, Gays Mills, WI; the second is credited to Steve Pincus, Tipi Produce, Madison, WI.
Luna Circle recipe

2 buckets black peat (1 bucket = 8 quarts)
1/2 bucket compost
Fertility mixture:
1 cup greensand
1 cup rock phosphate
1 cup kelp meal
2 buckets sphagnum peat moss
1 bucket sand
1 bucket vermiculite
Directions for mixing: Screen the peat and the compost and combine with the fertility mix. Mix well. Add the sphagnum, sand, and vermiculite. Mix well again.

Tipi Produce recipe

2 bales sphagnum peat moss (3.8 or 4.0 cu.ft. bales)
1 bag coarse vermiculite (4.0 cu.ft. bags)
1 bag coarse perlite (4.0 cu.ft. bags)
6 quarts of a fertilizing mixture comprised of:
15 parts steamed bone meal
10 parts kelp meal
10 parts blood meal
5-10 parts dolomitic limestone (80-90 mesh)
Note: This mix works well in small and medium plug trays and 1020 flats for growing lettuce, onions, leeks, peppers, tomatoes, melons, squash, cucumbers, and many flowers. When repotting small plugs into larger cells, add about 1/3 by volume of old leaf mold or compost and more fertilizing mixture. Continue to fertilize twice per week with soluble fish and seaweed fertilizer.

The following three recipes are adapted from a subchapter entitled “Using compost for container crops and potting mixes” in On-Farm Composting Handbook, by Robert Rynk, (ed.). 1992. Publication NRAES-54. Northeast Regional Agricultural Engineering Service, Cornell Cooperative Extension, Ithaca, NY. 186 p.
Vegetable transplant recipe

Equal parts by volume of: compost, peat moss, perlite, or vermiculite

Bedding plant recipe

25% compost
50% peat moss
25% perlite or vermiculite

Container mix for herbaceous and woody ornamentals

Equal parts by volume of: compost, coarse sand, peat moss, or milled pine bark

The following two simple recipes came from Mark Feedman, a practitioner of the Biodynamic- French Intensive system. The first mix was used with great success while doing development work in the Dominican Republic; the second is an adaptation used later in New Mexico.
Dominican Republic mix

Equal parts: fine loam soil, sharp horticultural sand, well-finished leaf mold

New Mexico mix
2 parts well-finished compost
2 parts good topsoil
1 part leaf mold

The remaining recipes in this appendix are of uncertain origin, but were published in earlier versions of ATTRA's Organic Potting Mixes.
Recipe #1

50 to 75 percent sphagnum peat moss
25 to 50 percent vermiculite
5 lbs. ground limestone per cu. yd. of mix

Recipe #2

6 gallons sphagnum peat moss ¼ cup lime
4.5 gallons vermiculite
4.5 gallons compost
1½ cups fertility mix made of: 2 cups colloidal (rock) phosphate, 2 cups greensand, ½ cup bonemeal, ¼ cup kelp meal

Recipe #3

10 gallons sifted 2-year-old leaf mold
10 gallons sifted compost
5 to 10 gallons sphagnum peat moss
5 gallons perlite
5 gallons coarse river sand
2 cups bloodmeal
6 cups bonemeal

Recipe #4

40 quarts sphagnum peat moss
20 quarts sharp sand
10 quarts topsoil
10 quarts mature compost
4 oz. ground limestone
8 oz. bloodmeal (contains 10% nitrogen)
8 oz. rock phosphate (contains 3% phosphorus)
8 oz. wood ashes (contains 10% potassium)

Recipe #5

9 quarts compost
1 cup greensand
3 quarts garden soil
½ cup bloodmeal
3 quarts sharp sand
½ cup bonemeal
3 quarts vermiculite

Recipe #6

1 part peat
1 part bonemeal
1 part perlite
1 part compost (or leaf mold)
1 part worm castings (optional)

Recipe #7

2 parts vermiculite
3 parts peat
2 parts perlite
2 parts cow manure
3 parts topsoil
½ part bonemeal

Recipe #8

15 qts. screened black peat
15 qts. brown peat
17 qts. coarse sand
14 qts. screened leaf compost
3 oz. pulverized limestone
9 oz. greensand
¾ cup dried blood
3 oz. alfalfa meal
3 oz. colloidal phosphate
9 oz. pulverized bonemeal

Recipe #9

10 pounds compost
30 pounds sphagnum peat moss
60 pounds white sand
8 pounds calcium carbonate
4 pounds soft rock phosphate
2 pounds sawdust

Recipe #10

70 pounds white sand
25 pounds sphagnum peat moss
5 pounds chicken manure
8 pounds calcium carbonate
4 pounds soft rock phosphate

[Cobain Killer]

sig check

[dankohzee]

Bump. I sure get a lot of questions about this...

[Corto Malteze]

Great stuff Dankohzee. I wish I 'd used this before messing up my start. We need this and your nube proof mix in a sticky imo.

[dankohzee]

Thanks Corto. In fact I'm going to put all the soil mix resources I have together and add content from the two threads you mention. I've heard too many bad soil stories already this year.

[Corto Malteze]

Yeah this is very important (like so many other things with growing ganja) and can really set you back and kill the seeds you paid for and had shipped at your home and all. Good luck to me with my new start and late grow...