During aerobic and anaerobic decomposition of plant and animal reside a complex aggregate of brown to dark coloured amorphous substances is obtained which is called as Humus. It includes humic substances and resynthesizes products of microorganisms. These products are stable and a part of the soil. Humus is categorised according to their molecular weights and solubility into humus, humic acids and fulvic acids. Humic substances are the organic material naturally present in soil. Humic substances positively effect’s soil quality and fertility by increasing its water holding capacity, stabilisation of soil structure, soil microbial activity, plant physiology. It also influence nutrient uptake and root architecture act like phytohormones for phosphorus acquisition, and improving plant adaptation to saline condition. Humus is the primary microhabitat for microorganism such as dictyostelids, myxomycetes, some species of protostelids, members of the genus Copromyxella etc. Other than that auxin like activity of Humic Substances has also been demonstrated in recent studies. The research suggested that it could be the main biological factor that exhibits positive effect on plant physiology. Based on that fertiliser factory also trying to produce are bio- stimulants, based on humic substances and other organic compounds.
Part of the book: Humus and Humic Substances