Agricultural Use of Natural Biostimulants - Humic Substances: a review

This work presents the characteristics of humic substances, with particular emphasis on the properties of agricultural importance, i.e., the improvement of soil structure, soil properties and the availability of nutrients. Attention was also paid to the methods of introducing given substances into the soil and the possibility of direct application to the plant surface. The mechanisms responsible for the stimulating and protective effect of humic substances on plant development were explained in detail, including phytohormonal regulation, the mitigation of biotic and abiotic stresses, antioxidant properties and the influence on seed germination and the development of the plant root system. The economic and environmental importance of the application of the substances in question was also emphasized, consisting of maintaining the health of the soil and the quality of plants while reducing the share of chemical fertilizers and reducing the amount of water used. It should be noted that humic substances, like any agricultural product, should be appropriately selected for the type of cultivation, i.e., the optimal dose and method of application should be determined.