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"Humic substances" is an umbrella term covering humic acid, fulvic acid and humin, which differ in solubility. By definition, humic acid (HA) is soluble in water at neutral and alkaline pH, but insoluble at acidic pH < 2. Fulvic acid (FA) is soluble in water at any pH. Humin is not soluble in water at any pH.
The formation of a humic lakes via organic runoff has a dramatic effect on the lake ecosystem. Increases in the lake’s acidity make it difficult for fish and other organisms to proliferate. The quality of the lake for use as drinking water also decreases as the carbon concentration and acidity increase.
The ability of plants to absorb humic substances with their roots and metabolize them has been long debated. [58] There is now a consensus that humus functions hormonally rather than simply nutritionally in plant physiology , [ 59 ] [ 60 ] and that organic sunstances exuded by roots and transformed in humus by soil organisms are an evolved ...
Fulvic acid is the genus that contains the matter that has the lowest molecular weight, is soluble in acids and alkalis, and is susceptible to microbial action. Humic acid is the genus that contains the intermediate matter that has medial molecular weight, is soluble in alkalis and insoluble in acids, and has some resistance to microbial action.
Potassium humate is used in agriculture as a fertilizer additive to increase the efficiency of fertilizers especially nitrogen- and phosphorus-based fertilizer inputs. Other salts of humic acid are manufactured, mainly sodium humate, which is used in animal health supplements. It also can be used in aquaculture.
Upon extreme drying, the ecosystem can undergo a state shift, turning the mire into a barren land with lower biodiversity and richness. Humic acid formation occurs during the biogeochemical degradation of vegetation debris and animal residue. [27] The loads of organic matter in the form of humic acid is a source of precursors of coal.
Soil consists of both mineral (inorganic) and organic components. The organic components can be subdivided into fractions that are soluble, largely humic acids, and insoluble, the humins. Humins make up about 50% of the organic matter in soil. [1]
Increasing the soil's pH increases the ability of naturally occurring humic substances to improve infiltration in hydrophobic soils. Humic acid is only water-soluble at a pH greater than 6.5, while fulvic acid is soluble at all pH ranges. Both resident acids have a property that enables them to reduce the surface tension of water when in solution.