Soil organic matter (Humus) is a mixture of dark brown organic substances formed by decomposition of plant residues. Microorganisms further break it down into Humic Acid. It plays a major role in soil fertility, both in physical as well as chemical aspects. Physically, it helps the soil to retain moisture and encourages the formation of good soil structure. Chemically, it has many active sites which bind to nutrients ions, making them more available. For comparison see soil particle with and without humus (Fig. 1. Bare soil Particle & Fig. 2. Soil particle with Agrisol EARTH BOOSTER/ROOT CARE).