Which Traits of Humic Substances Are Investigated to Improve Their Agronomical Value?

Abstract

Humic substances (HSs) are chromogenic organic assemblies that are widespread in the environment, including soils, oceans, rivers, and coal-related resources. HSs are known to directly and indirectly stimulate plants based on their versatile organic structures. Their beneficial activities have led to the rapid market growth of agronomical HSs. However, there are still several technical issues and concerns to be addressed to advance sustainable agronomical practices for HSs and allow growers to use HSs reliably. First, it is necessary to elucidate the evident structure (component)–function relationship of HSs. Specifically, the core structural features of HSs corresponding to crop species, treatment method (i.e., soil, foliar, or immersion applications), and soil type-dependent plant stimulatory actions as well as specific plant responses (e.g., root genesis and stress resistance) should be detailed to identify practical crop treatment methodologies. These trials must then be accompanied by means to upgrade crop marketability to help the growers. Second, structural differences of HSs depending on extraction sources should be compared to develop quality control and assurance measures for agronomical uses of HSs. In particular, coal-related HSs obtainable in bulk amounts for large farmland applications should be structurally and functionally distinguishable from other natural HSs. The diversity of organic structures and components in coal-based HSs must thus be examined thoroughly to provide practical information to growers. Overall, there is a consensus amongst researchers that HSs have the potential to enhance soil quality and crop productivity, but appropriate research directions should be explored for growers’ needs and farmland applications.

Insights into the Applications of Extracellular Laccase-Aided Humification in Livestock Manure Composting

“…Compared with traditional composting, laccase-assisted LM composting produces more stable, beneficial, and harmless humified products. They have been confirmed to represent positive effects on the growth and development of plants. − It is because extracellular laccase-assisted composting effectively stimulates decomposition of biopolymers and then repolymerizes the formed small precursors, , consequently increasing the yield of humic substances. Furthermore, laccase-ameliorated composting also can create various humic-like organic fertilizers and lignin-like supramolecular assemblages through radical-initiated random assembly. , These products and humic substances have similar structural and physicochemical properties, especially their aromaticity and related hydroxyl and carboxylic groups, which can heighten the availability of nutrients for plants. ,, As previously reported, two close-knit humified precipitates were formed by continuous laccase-initiated polymerization, and the measured change of laccase activity was negligible .…”

Chemical Structure and Biological Activity of Humic Substances Define Their Role as Plant Growth Promoters

“…Among these strategies, the use of biostimulants is relevant, of which HS category is part [1][2][3]. Biostimulants by definition are substances that promote plant growth, nutrition and metabolism through modes of action that are challenging to decipher, but definitely different from those related to fertilizers [4].…”

Lignosulfonate Rapidly Inactivates Human Immunodeficiency and Herpes Simplex Viruses

“…Accordingly, two SI values were produced: SI-I (=CC 50 /EC 50 -I) and SI-II (=CC 50 /EC 50 -II). As a control, commercially available alkali-lignin, dealkali-lignin, and humic acid (chromogenic and structurally irregular organic assemblies that are widespread in soils, rivers, oceans, and coal-related natural resources) [ 40 ] were used.…”