103: The Importance Top Six Inches of Soil in Your Garden Bed

It’s the beginning of summer! Everyone gets excited to shop at Home Depot, Lowes, Walmart and Menards for garden soil, compost, etc., etc. When temperature favors the first thing we do is dump compose and start tilling the garden bed, STOP!

Know the importance of soil structure before you till your garden bed. 

While it take several years to build a good soil structure it takes few seconds to destroy it!

The soil structure consists of several layers meant for each microbial thriving. The top six inches of a garden soil is Aerobic and contains at least 90% of aerobic colonies of microbial life. This layer is extremely important since it holds 100s of different species of bacteria, Fungi, yeasts, protozoa, nematodes, etc. Aerobic mean those need air to thrive. The bacteria that breaks down organic matter at the top of the soil bed need oxygen. Humus (life of the soil), as the end-line result of decayed organic matter is concentrated in the top three to six inches of soil. However it is quite opposite in the subsoil i.e., 6 inches below the top layer. Sub soil is called Anaerobic layer where air free life thrives. Anaerobic layer is a habitat for micro algae with very minimal activity. The bacteria and other microbes go inactive or often die when exposed to this layer.

The reasons gardeners may till are:

  1. To get organic matter incorporated into the soil of a garden bed.
  2. To make soil loose and fluffy
  3. To improve water drainage

Remember, excessive / improper tilling puts aerobic life in airless chambers, and moves anaerobic life up to where there is air resulting in total loss of microbial life. You are actually doing more damage than better.

Whether to till, not to till, how much to till has been a debate for many years with no concrete result. Based on my experience I found no tilling or minimal tilling up to six inches is a best way. This is one of the main reason to better use raised beds.

Always be cognizant of your garden bed, understand soil biology, chemical and biological relations of microbes that affect the plant and soil life. If you are using raised beds then tilling is absolutely unnecessary. You can just add some soil amendments and gently mix it in the top 3 inches. Always follows best practice. Reach us if you would like to learn more about the best practices. We will try our best to educate you with the small amount of knowledge we have.


  • Clay soil after one feet shouldn’t be a problem at all. Alternatively you can do a raised bed. If clay soil at that level is still your concern then try amending with compost or a very little amount of gypsum.

  • I have a clay soil after 1 feet. What’s the best way to make that soil better. Water drainage was not good.

    Suma B Maineni

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