Soil Composition

A successful organic kitchen garden can be grown almost anywhere. The key is to understand the soil you have and how to alter it to become fertile and loose.

Your soil is the foundation of your garden and your success. An understanding of your soil is probably the most important aspect of growing a successful organic vegetable garden. Every area of the country is different, so it is necessary to analyze your soil.

Soil is a combination of mineral particles mixed with living and dead organic matter. Soil types are determined by the soil particle size:

  • Clay – Small particle soils that are nutrient enriched and hold water well
  • Silt – Medium particles full of organic nutrients and good water holding capabilities.
  • Sand – Large particles for good aeration and drainage, but nutrients easily leach out and dry out fast.

An ideal soil is a mixture of all three mixed with a lot of organic amendments. Most soils are not perfect and need changes in there structure to set up an environment for roots to flourish. Mixing different size particles will create small air spaces between the particles necessary for good root growth.

Anatomy of Soil

Consists of 4 layers:

  • Top soil – 4-8 inches deep-usually contains most organic matter due to leaf fall.
  • Mineral subsoil – as deep as 30 inches, little organic matter, inhospitable to veggies unless deeply tilled and amended
  • Lowest soil – contains rock fragments broken off from bedrock below
  • Bedrock – inner layer of soil

Three tests can be done to help decide what kind of amendments to add:

  • Drainage test- dig a hole 10-12 inches deep and wide-pour 1 gal water in it- note how long it takes to drain- 5 min (sandy), 1-15 min (loam)(preferred), or 15+ (clay soil).
  • Crumb test- Best soil will hold loosely when damp if squeezed in your hand. Too loose, it’s too sandy, too firm, it’s contains too much clay.
  • pH test- Veggies like a slightly acid to neutral pH of 6.5 to 7. If pH is off, plants cannot absorb nutrients and fail.

A good all purpose recipe for good veggie garden soil if purchased is equal parts top soil, peat moss, and compost.
Bulk amendments, unlike fertilizer, are applied in copious amounts, for good veggie growth. From 20-50 % of the soil can be organic matter.

Amendments are available in 2 types


Pumice, perlite, and vermiculite- are permanent additions to the soil, do not break down or provide nutrients but provide aeration and texture to the soil. Work well in small scale gardens and containers.


  • Compost – the number one amendment, accomplishes numerous functions with its addition in copious amounts to the veggie patch. Made of any green and brown plant matter that has decayed into dark humus. It will neutralize soil that’s either too acid or too alkaline. Helps create a light loam texture with good water retention added to sandy soils and good aeration when added to clay soils. It has low amounts of N-P-K and lots of microorganisms and trace elements. You can make your own out of kitchen scraps and yard debris (CREATE), or you can purchase organic compost at any nursery or home improvement store for $2.00 a 40 lb. bag.
  • Manure – The fecal matter from farm animals, usually cow, horse or chicken. DO NOT use dog and cat feces as they are meat eaters and may contain harmful bacteria. May be applied fresh to garden beds in fall to be planted next season, or usually better to apply composted or dehydrated manure 3-4 weeks before planting, more pleasant! Also contains low amounts of N-P-K and aids the texture of any soil.
  • Peat Moss – Harvested moss with a very slow breakdown. It helps sandy soils to retain water and improve texture. It does not supply any nutrients but can be used to lower the pH of the soil.
  • Leaf mold – decomposed leaves, most yards have plenty in the fall. Pile up and leave it, you’ll have compost in 2-3 years. Or add leaves to the compost pile as brown matter.