Recipe For A Soil Block

WHAT IS A SOIL BLOCK?blocks in tray

A soil block is a block of growing medium that has been lightly compressed and shaped by a form.

A soil block serves as both a container and the soil for starting and growing seedlings, eliminating the need for plastic pots and trays for transplanted seedlings.

Seedlings grown in soil blocks form stronger root systems than those grown in containers due to increased oxygen to the roots and the soil block’s natural tendency to “prune” roots. This creates a substantial advantage when seedlings are transplanted into the field, because plants establish themselves more quickly and, because of lessened root disruption, they are less prone to transplant shock.

The key to making good soil blocks is to use a mix containing the correct proportions of peat, compost, soil, and sand or perlite. A “blocking” mix needs extra fibrous material—peat—to bind the material together and help the block retain moisture.

Some commercially available peat-lite mixes may work but often contain wetting agents and/or fertilizers that make it unsuitable for organic use. 



A standard 10-quart bucket is the unit of measurement for the bulk ingredients.

A standard cup measure is used for the supplementary ingredients.

This recipe makes approximately 2 bushels of mix.

Follow the steps in the order given.

3 buckets brown peat (standard peat moss, use a premium grade)

½ cup lime.

Mix ingredients together thoroughly.potting on

2 buckets coarse sand or perlite

3 cups base fertilizer (equal part mix blood meal, colloidal phosphate, and greensand).


1 bucket garden soil

2 buckets well-decomposed compost.

Mix ingredients together thoroughly.

From The New Organic Grower, by Eliot Coleman. Moisten the mix thoroughly using one part warm water for every three parts blocking mix.

Successful soil block making depends on the mix being wet enough, rather than wet like soil mix in traditional flats. The mix should have the consistency of soft putty or wet cement, so that a small amount of water oozes through small openings in the blocker as the blocks are made, and that the individual soil blocks cling to the blocker without falling out prematurely.




Blockers can be used on any flat work surface.

Push the prepared soil mix into a mound that is 1¼ to 1½ times deeper than the height of the soil blocker.

Push the blocker into the mix until it strikes the work surface.

Twist the blocker a quarter-turn and lift.

Set the blocker where you plan to grow your seedlings such as a wooden or plastic tray, push down on the handle while raising the blocker.

Rinse the blocker in warm water before making the next set of blocks.

Place the seed into the indentation of each block, and cover according to the culture information on your seed packet.

Prevent drying by covering blocks with Clear Acrylic Domes or a layer of plastic until the seeds have germinated.   


Where you can purchase the supplies -

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