Effects of Humic Substances on Soil Microbes

By Richard Lamar, PhD
Senior Director of Humic Research
Bio Huma Netics, Inc.

Most of the work on agricultural applications of humic substances (HS) has focused on their biostimulant effects on plants. Far less work has been conducted on the effects of HS on soil microbial populations. It’s not surprising to learn, from the few studies that have been published, that HS also stimulate the growth of soil bacteria, even the bacteria that inhabit earthworm digestive tracts. One of the most important discoveries is that many species of soil bacteria are able to grow on humic acid (HA) as their sole carbon source (Tikhonov et al., 2010).

These findings have important implications for the roles played by soil bacterial communities—including those residing in the guts of soil fauna, such as earthworms—in the humification process (i.e., the process of conversion of dead plant tissues to humic substances). This means that these bacteria are consuming HS and modifying HS by metabolizing humic molecules and using the metabolized molecules to produce proteins, fats, and other types of molecules. When the bacteria die, they are in turn consumed by other microbes and those molecules created from metabolized humic molecules wind up being included as HS.

The other important piece of information that has come out of the work on bacterial-HS interactions is that, in addition to being potential carbon sources, HS can also act as soil bacterial growth stimulants or growth regulators (Tiknonov et al., 2010). This was demonstrated in a study in which a number of soil isolated bacterial species were grown on a medium that contained glucose as the carbon source (10 mg/ml) and humic acid (1 mg/ml). Thus, the humic acid was 10X lower than the glucose. Growth of the bacteria on this medium was compared with the growth of bacteria on a medium that did not contain the humic acid. The growth of 41% percent of the bacterial species (these were isolated from earthworm digestive tracts) were stimulated by the inclusion of the humic acid. The authors of the study concluded that, because the concentration of glucose was so high and the increase in available carbon from the addition of 1 mg/ml humic acid was insignificant, the humic acid acted as a growth stimulant to the 41% of bacteria whose growth was increased.

These types of studies have demonstrated that HS can stimulate the growth of plant-growth-promoting rhizobacteria (aka PGPR bacteria, for which the “rhizo” stands for rhizosphere or the area of soil that is intimately associated with plant roots). One of the most well-known PGPR bacteria are Pseudomonads, strains of which have been found to be able to solubilize phosphate, produce siderophores (important for Fe uptake), ammonia, and the plant-growth-regulator auxin (Gupta, 2008; Selvakumar et al., 2009).


Gupta, A. and M. Gopal. 2008. Siderophore production by plant growth promoting rhizobacteria. Indian J. Agric. Res. 42(2):153–156.

Salvakumar, G., P. Joshi, S. Nazim, P. K. Mishra, J. K. Bisht and H. S. Gupta. 2009. Phosphate solubilization and growth promotion by Pseudomonas fragi CS11RH1 (MTCC8984), a psychrotolerant bacterium isolated from a high-altitude Himalayan rhizosphere. Biologia, 64(2)239-245

Tikhonov, V. V., A. V. Yakushev, Y. A. Zavgorodnyaya, B. A. Byzov, and V. V. Demin. 2010. Effect of humic acids on the growth of bacteria.  European Soil Science, 43 (3):305–313.

Bio Huma Netics, Inc., and Mesa Verde Resources Form Strategic Alliance

Bio Huma Netics, Inc. (BHN)—an Arizona company that produces products under the Huma Gro®, Huma Gro® Turf, and Probiotic Solutions® brands—has recently formed an alliance with Reid Enterprises LLC, which does business as Mesa Verde Resources in New Mexico. Mesa Verde Resources is a humic substance mining company that produces, manufactures, and sells humic-acid and fulvic-acid products.

Other than access to a greater range of products, customers from the two companies should see no change in day-to-day operations. There will be no immediate change in personnel at either company, and the two companies will continue to operate separately under separate names for the immediate future.

This alliance is expected to facilitate a synergistic relationship between the BHN lines of agriculture, turf, and wastewater/soil remediation products and the Mesa Verde Resources line of humic and fulvic products for both domestic and international markets. While BHN has previously focused on a fraction of humic substances to extract the Micro Carbon Technology® used as a base for all its liquid products, the combined company will now offer its customers an even greater selection of dry and liquid products that includes MVR’s various formulations of humic and fulvic acids.

Bio Huma Netics has averaged over 20% growth per year over the last 10 years. With the Mesa Verde alliance, combined company sales are expected to increase by 30% in 2017.

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About Mesa Verde Resources 

Mesa Verde Resources (MVR) mines and manufactures high-quality New Mexico humates, with humic and fulvic acid products including granular products, powders for solution and suspension, and liquid humic and fulvic acids. MVR humates—mined from the Fruitland Formation of the San Juan Basin in Northwest New Mexico since 1975—are used extensively to increase crop quality and production and to improve and replenish depleted soils. Learn more at www.humates.com.

About Bio Huma Netics, Inc.

Founded as Sunburst Mining Company in Mesa, Arizona in 1973, Bio Huma Netics, Inc., (BHN) is a global leader in providing sustainable solutions to the world’s environmental challenges for agriculture (HUMA GRO®); horticulture, turf & ornamentals (HUMA GRO® TURF); and soil & wastewater remediation (PROBIOTIC SOLUTIONS®) through its constantly improving proprietary Micro Carbon Technology®. Learn more at www.bhn.us.

Media/Customer Contact: 1-800-961-1220

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