Most beneficial microorganisms require good levels of oxygen to thrive. In fact, it could be argued that oxygen is the most important element in biological gardening. Aerobic soils are richly supplied with oxygen while anaerobic soils lack this element. Earthworms create pathways for oxygen to enter the soil and calcium opens up (flocculates) the soil to let it breath. Gypsum can break up heavy clay soils to sponsor better oxygen intake, while compost can improve you soil to create a highly desirable crumb structure. Light tillage with a fork can also help aerate soils.
