Composting

During the composting process, the material oxidizes, breaking down into proteins and carbohydrates. The proteins break down into peptides and amino acids, then into ammonium compounds. These compounds are changed by certain bacteria into nitrates, a form of nitrogen which can be used by plants to make chlorophyll and essential proteins. The carbohydrates break down into simple sugars, organic acids, and carbon dioxide.

Nutrients in humus enter plant tissues by a process called base exchange. In this process, hydrogen ions in the fine root hairs of plants are exchanged for the nutrient ions in the soil moisture. The nutrients are then free to move up into the plant.