There are many worlds within the earth below your garden: it is the stage of many complex chemical processes and interactions between processes. Soil is a mixture of tiny mineral particles of many kinds, organic matter in various states of decomposition, and water. Living things like fungi, bacteria, earthworms and insects live their lives there, contributing to soil aeration, its organic matter content, and sometimes playing a vital role in chemical cycles like the carbon, nitrogen, calcium, and phosphorous cycles. [...]