An ozone containing gas is injected into soil, preferably relatively dry and approximately uniform in consistency, to kill biological life forms. The method and apparatus for ozone treatment of soil suitable for plant growth purposes can be used in conjunction with other agricultural methods such as irrigation (801), tilling (802), and fertilization (805). For example, soil is irrigated (801) to ensure proper moisture for tilling (802) and afterwards is allowed to dry (803) by exposure to the sun or is dried artifically with heated air. Then, after an ozone treatment step (804) the soil is fertilized (805) for receiving seeds or seedlings (806). The plants from seeds or seedlings experience enhanced growth due to absence of detrimental biological organisms that were killed by ozone treatment (804). The soil is once again irrigated (807) and pesticides or herbicides applied (808), as needed. After harvesting (809), the steps can be repeated for another season.