ABSTRACT
Organic matter that has fully broken down into stable residues is referred to as humus.
Three classes of humic substances are distinguished: fulvic acid, humic acid, and humin. Humic substances are produced through biological and chemical degradation, and through the activities of soil microbes. Fulvic acid is smaller and less stable than humic acid or humin. Organic matter in landscapes includes both materials that are incorporated into the soil, which are grouped under the heading of amendments, and those that are applied to the surface, or mulch. Vermicompost is a composting system that uses earthworms in a specially designed bin system. Under trees, the area of mulch that should be applied is the circumference of the canopy. This is sometimes referred to as the dripline of the tree, because it indicates where rainfall would drip directly from above.
