Empowering Soil Microbiology through Liquid Biological Amendments

Any soil that can support plant growth, even if highly degraded, will contain some level of microbial population. Existing microbial communities can be grown through bio-stimulation, which is the process of adding microbial foods to the soil. Molasses, kelp, humic acid, fulvic acid, and fish hydrolysate are all excellent food sources to promote microbial growth. Poorer soils devoid of larger microbial communities, however, may also require bio-augmentation, or the addition of beneficial microbes in the form of liquid biological amendments to the soil ecosystem.

There are three broad categories of liquid biological amendments. Many commercial amendments, often referred to as “bugs in jugs”, focus on specific types or species of micro-organisms, such as mycorrhizal fungi or Azospirillum bacteria, or contain a broader cocktail of microbes. Specific bacteria can also be isolated and propagated through yeast fermentation in a process known as effective micro-organisms (EM). Such targeted amendments are often used to treat specific conditions at the behest of consultants and represent the most expensive category.

At the other end of the spectrum, another form of amendments centers around the home garden and kitchen. Collecting, fermenting and processing local plant wastes and leaf molds creates concentrates of indigenous micro-organisms (IMO) and plant-produced minerals. Many of these processes were developed by Ju-Young Cho and Youngsang Cho, and are sometimes referred to as Korean Natural Farming (KNF) or JADAM practices. Nigel Palmer’s The Regenerative Grower’s Guide to Garden Amendments contains a broad range of tips and recipes for small-scale homemade extracts and ferments.


The third and most versatile form of liquid biological amendments are extracted from compost, which, if well-produced, contains a host of beneficial microbes. Thermophilic composting eliminates weed seeds and many pathogens through high temperatures, but can be harmful to some microbes, especially fungi. Compost can be produced efficiently and inexpensively in a variety of methods at any scale or sourced locally. 

Specific methods, such as the Johnson-Su bioreactor and Edwin Blosser's humus composting, enrich the microbial density of the finished compost.  Any partially or fully composted material can be processed by worms in a vermicomposting system, inoculating additional microbes and adding further benefits such as natural microbial bio-stimulants, soil aggregate-building mucus, and plant growth hormones, for the low price of maintaining a worm bin. Any form of compost can be verified as biologically complete according to standards set by the Soil Food Web network, which will yield the best results.

Liquid compost extract (LCE) is created by rinsing off and suspending microbiology from the solid compost material, which can be recycled into the composting operation. If no aeration is used as part of the process, the microbes will remain in a static condition without multiplying, allowing  the extract to be stored under the right conditions. Injecting oxygen into the liquid will convert it to activated compost extract (ACE), also known as “compost tea”, which will stimulate population growth and will need to be applied within 12-48 hours.

Of the three categories of liquid biological amendments, compost extract is perhaps the most promising. Efficient and cost-effect composting operations can be designed around producing a biologically complete product and scaled to any size of operation, particularly with the inclusion of vermicomposting. This process can also be used to balance soil chemistry, by adding deficient micro-nutrients and excluding excessive macro-nutrients contained in bulk compost, such as nitrogen, from the liquid extract. Organic wastes are recycled on-site and local, adaptable microbes are propagated. Commercial and / or home cultured amendments can be used as supplements to an effective base system of compost extract production.

Liquid biological amendments can be applied to both soil and plants in a variety of ways. Existing irrigation systems can be used for fertigation, as long as the liquid is not overly pressurized, which will damage the microbes. Off-season soil drenches build microbial communities in the rhizosphere, while in-season foliar sprays arm the plants’ leaves with beneficial microbes and ward off pathogens and pests. Application systems should be designed to protect microbiology, such as using a diaphragm pump and low-pressure, high-volume flow. Amendments can also be used to coat seeds or be injected into the soil at planting, encouraging healthy germination and early growth.


The Hiwassee Bio-Extractor is capable of producing thousands of gallons of liquid biological amendments in a single day. 

Hiwassee Bio-Extractor



For a recommended source on liquid biological amendments, please refer to the work of Dr. Elaine Ingham and her Soil Food Web School.