From the EGT’s Sustainable Landscaping Series, “The Ecological Benefits of the Not So Perfect Yard”

Bad Habit #10 – Tilling

• Don’t till seasonally.  If the condition of the soil bed requires it, till once at the beginning of the bed set up and then let it do its thing naturally.
• Tilling brings up weed seeds that are buried in the soil and setting them free to germinate and do their worst.
• Tilling destroys soil structure and small microorganisms that are a part of the living soil structure.  This means they are unable to produce nitrogen that benefits your plants.
• Tilling can create a thick, dense layer of compacted soil known as hardpan.  Hardpan can restrict the flow of nutrients and water through the soil. 
• Tilling releases carbon into the atmosphere that you should keep in your soil.

Kick the Habit Cover your soil with layers of mulch. Wood chips in particular, placed ON TOP OF THE SOIL, are an invaluable resource.  They are generally available for free and are used by organic gardeners to mulch their gardens. The chips eventually break down and feed the soil increasing its fertility, water retention, and the beneficial organisms in the food web.  Green mulch (plants) is even better.