Garden & Greenhouse


Soil Microorganisms – The World You Can’t See

Posted March 26th, 2011 by Garden & Greenhouse in ,

Building high populations of beneficial microorganisms in the soil will dramatically increase growing success, soil and plant health, and help to increase satisfaction as a grower. Microorganisms are one major piece of the gardening puzzle. Microbes convert nutrients into (bio-available) forms that plants can use, including fixing nitrogen. A high percentage of nutrients applied to soils go unused, wasting valuable nutrients leading to groundwater contamination in areas with high water tables and wasting money. Microbes also produce

Microbes include bacteria, viruses, fungi, algae, yeast, amoebas, protozoa, nematodes, arthropods, insects, and earthworms. There are aerobic and anaerobic kinds. This means some require lots of air (aerobic) and other do not (anaerobic). In general people tend to think of anaerobic bacteria as pathogens and aerobic bacteria as beneficial, or non-pathogenic. However, there are pathogenic aerobic microbes and not all anaerobic microbes are pathogenic. Pathogens are called such because they produce various substances that can be toxic to humans, animals, and plants. Pathogens are generally associated with a putrefactive (rotting) pathway. The by-products of putrefaction are odorous and very often toxic to plants, humans and animals.

Microbes can be introduced in a variety of ways. These include making compost teas, buying inoculants such as such as EM•1 Microbial Inoculant, that contain a diverse species from several genera, and beneficial fungi such as mycchorizae. There is a trick when adding microbes though. There is a lot of mass and billions of microbes in the soil. It takes regular applications with very high populations of microbes and good land management to make changes. When the numbers of microbes from an inoculant are significant and certain methods are followed, they are able to suppress the growth of pathogens including the above-mentioned bacteria and microbes such as E. coli, Salmonella, Botulinum, etc. This process is also known as competitive exclusion and is very commonly practiced in food manufacturing.

Carbohydrates are food for the microbes and are converted to various beneficial compounds by lactic acid bacteria and yeasts such as trace minerals, vitamins, amino acids, and enzymes, which are utilized by other microbes and macrobes (worms and other insects). A typical conversion of sugar under the lactic acid bacteria type of fermentation will follow the following formulas:



Lactic acid bacteria and yeast both produce small amounts of carbon dioxide (CO2), Oxygen (O2), and hydrogen (H2). However, during anaerobic phases, the Lactic acid bacteria will not produce gas and the yeast will produce carbonic acid instead of alcohol. Several species of photosynthetic microbes grow and increase their biomass by absorbing carbon dioxide, but can also increase biomass by degrading organic compounds including such toxic compounds as 3chlorobenzoate to cellular building blocks. When oxygen is present, R. palustris generates energy by degrading a variety of carbon-containing compounds (including sugars, lignin monomers, and methanol) and by carrying out respiration. ( )

Anaerobic/pathogens produce methane, butyric acid, Hydrogen Sulfide, Ammonia, and promote the growth of pathogenic species. Aerobic/beneficials produce or release oxygen, hydrogen, carbon dioxide, enzymes, amino acids, trace minerals, bio-available vitamins, ammonium, and promote the growth of other beneficial microorganisms.

As you can see, there is a lot going on with microbes. And, this is only a small look into the world of microbes. With the billions of microbes that are in soil, we want to make sure the soil maintains high levels of beneficial microbes to promote healthy soils and plants. This is done through inoculating the soil with various amendments and good management of the soil. It can also be helped along with adding in various inoculants containing high populations of beneficial microorganisms and a diversity of species. From this we can also see the importance of preventing compacted (anaerobic) soils as most pathogens are anaerobic.

As one becomes a biological gardener/farmer, they tend to use their senses more and observations are used to address issues. Watch for compaction. Look at the surface after watering or heavy rains. See which areas drain quickly. Watch plants to see areas that tend to get attacked by pests and/or disease. Look for worms in the soil and look for pests and predators. As you explore this new world, think about what you cannot see and think about the billions of microbes in the soil that hard at work to make the nutrients you add available for you plants and how they affect the soil structure. Give them a little help by regularly sending in some reinforcements. Over time you will notice changes in the soil, drainage, plant health, pest infestation, and find that fruits and vegetables get sweeter and sweeter year after year.

Eric Lancaster is Executive Vice President of TeraGanix, Inc.