OMRI listed John & Bob’s Optimize Soil Optimizer consists of decomposed humus derived from leonardite found in the top layers of the earth’s surface. Humus is a food source for both plants and microorganisms that increases plant fertility and vitality with organic content. In addition, Optimize contains calcium and iron which work with humus to balance the soil, improve clay soils, and feed the beneficial micro-organisms that are necessary for a healthy growing system. This product is designed to work with John & Bob’s Penetrate Liquid Bio-Tiller , Maximize – Microbes and Minerals , and Nourish – BIOSOL . Shop All John & Bob’s Products here .