The Microbial Revolution in Growing Plants
By Al Will - Professor Emeritus
Have you ever been in a wilderness area and wondered why the plants look so lush and green?
I'm sure you commented to yourself that mother nature has done a marvelous job creating all this
Then you may have thought, "why can't my plants look as good? I water and fertilize but,
it's not the same. What is mother nature doing that I'm not?"
Well, you're not the only on that has had these and similar thoughts. Some scientists have
had similar questions and, being scientists, they began searching for the answers. We have
known for centuries that if you have a good amount of organic matter in the soil, that plants
would grow better, even today we go out of our way to buy "good dirt", - organic matter, and
add it to our gardens. Unfortunately, we just can't afford the amount of organic matter it
would take to do our entire yard. Even if we could, would that solve all of our growing
problems? The answer is no.
Now a few scientists have come forward with some "new" old ideas. We have known for over
a hundred years that soil is made up of inorganic matter, organic matter, air, water,
pH (acidity/alkalinity) and soil organisms. Soil scientists have taught and practiced
soil chemistry for decades covering all aspects of soil make-up except for the last item
previously mentioned - soil organisms. Soil chemistry has brought us up to the point
where the United States can out produce most countries of the world in growing crops,
but at what price? Our soils are wearing out. Many soil scientists today have concluded
that our standard cultural practices are actually counterproductive. They have determined
that it is now necessary to apply more inorganic fertilizers and pesticides each year to
achieve the same results as the previous year. Eventually, these practices will no longer
be cost effective, not to mention the toll they take on the environment. In actuality these
standard cultural practices are counter productive, they negatively impact the naturally
occurring soil organisms.
Soil organisms? Composed primarily of microorganisms or, microbes are those microscopic
living parts of the soil that most of those early soil scientists knew were there but chose
to ignore in favor of soil chemistry. Which brings us to the subject of this article:
"The Microbial Revolution in Growing Plants." Using microbes is a unique
organic approach to plant care and is causing quite a stir in the horticultural and
agricultural industry. This "back to basics" approach to plant management is centered on
improving the biological activity in the soil through the use of microbial inoculates and
organic nutrient sources. It has been coined the "Microbial Revolution." More and more
professionals in the nursery, landscape, farming, and golf course industries as well as
homeowners are joining the revolution. This new organic approach has come to the forefront
of the mainstream horticulture.
Over the last 500 million years plants and beneficial soil microorganisms have developed a
symbiotic relationship. When a plant photosynthesizes, it produces food, photosynthates,
which are used for plant growth and development. About 30 to 40 percent of these
photosynthates are actually exuded from roots into the soil or rhizosphere [root zone].
The microbes in the rhizosphere surround the root to get this food source. This exudate
is used by the beneficial soil microorganisms as a source of food. The microorganisms in
turn, protect the plant from harmful nematodes and pathogens, recycle nutrients, improve
the surrounding soil structure, solubilize minerals for plant availability, and produce
natural plant hormones. As you can see, this natural approach is truly as beneficial
The microbial populations found in the soil are comprised of beneficial bacteria, fungi
and protozoans - "mother nature." These microscopic creatures perform a variety of
functions and are quite capable of maintaining plant life when left to their own devices.
Microbes have the capability of decomposing organic matter. These essential nutrients,
the same as provided by a good fertilizer, are slowly released which in turn promote healthy
plant growth. In layman's terms, microbes greatly reduce the need for supplemental fertilizer
Beneficial soil microorganisms, as mentioned earlier, have the capacity to reduce the
likelihood of root disease such as Pythium, Fusarium, Phytopthera and Rhizactonia.
This is accomplished by a process called competitive exclusion. The microorganisms
compete for the same food sources as pathogenic disease causing organisms, keeping
them in check through the process of natural selection. Many species of microorganisms
are also capable of producing an antibiotic that inhibits protein synthesis, and enzymes,
such as chitanase, which inhibits cell wall formation, both of which will cause the
pathogen to expire. Together, these processes provide beneficial soil microbes with
natural fungicidal properties.
Unfortunately, most of us don't live in a beautiful natural forest with "mother nature"
taking care of our plants. A forest may have existed at one time where we now have our
homes but, the forest has been destroyed and so have those wonderful beneficial microorganisms.
Nurserymen don't grow plants in a natural forest either, but in fields and pots where those
beneficial microorganisms have also been destroyed or never existed in the first place.
Pesticides, when applied to control insects and disease, kill non-target organisms as well.
When this occurs the vicious cycle is perpetuated.
Is it possible to break this cycle, reverse this process and reestablish "mother nature" in our home landscapes and in our commercial nurseries? The answer is yes! The first step is to apply a "true" organic fertilizer that will provide a food source for the microorganisms and your plants. Scientists have determined that a fish emulsion/kelp/blend is most suitable for that purpose. These types of fertilizers will provide a good foundation to expedite the establishment of your soil microorganisms. The second step is to supply a microbial innoculant to reestablish the beneficial bacteria and fungi that are no longer there. Scientists, through years of research, have been able to collect the naturally occurring missing microorganisms, reproduce them in laboratories, and produce a product that is now available for the home owner and nurseryman alike.
Innoculants are available in water soluble powders for hose end application and granular formulations that can be applied by any standard spreader. It is important to follow directions carefully to achieve optimum results. Microorganisms require a food source [organic fertilizer], oxygen, moisture and soil temperatures over 40 degrees farenheight in order to multiply and establish themselves. The beauty of this approach to plant management is that once you reestablish these microbial populations you can actually reduce the number of applications of innoculants. If it becomes necessary to supplement your applications with an insecticide, beneficial nematodes and/or Neem oil can be used without adversely affecting the microorganisms.
In general, microorganisms improve soil conditions and allow plants to thrive under extreme soil conditions such as heat, disease, drought and insect infestation. This is all accomplished naturally, without the addition of synthetic materials.
In the past, organics have been looked down upon. It has been said that they don't work or that it takes years to see results. This microbial approach has taken organics to the next level. You will see staggering results in the first year of this program. This "back to basic's" approach has worked for millions of years in our natural forests and meadows. It is effective and good for the environment, a great change in the way we grow our plants in our landscapes and nurseries!