pH level of soil.

Sweet, sour, or bitter? These are common terms to describe soil ph. Sweet soil is the mid range, or ideal pH levels for most plants. Sour soils are acidic soil, with a low pH level. Some plants prefer a slightly acidic soil. Bitter is used to describe alkaline soils or high pH soil.

Why do nutrients get "locked up" in the soil? The mid range of the pH scale is the optimal range for bacterial growth to promote decomposition, a process that releases nutrients and minerals, making them available to your plants. Mid range pH is also the ideal range for growth of soil microorganisms that convert nitrogen in the air into a form that your plants can use. Outside of the ideal range, both processes are increasingly inhibited.