Photo Caroline de Rauglaudre

by Caroline de Rauglaudre

Communication manager

Plants are naturally colonized by billions of microorganisms. The study of microbial communities associated with plants has enabled us to highlight many microorganisms of agronomic interest. Some can, for example, protect crops through biological control, improve plant nutrition through solubilization of mineral elements blocked in the soil, or stimulate root growth through the secretion of phytohormones.

More and more microbial preparations are offered to farmers with “stimulating”, fertilizing or phytopharmaceutical virtues.

How to make sense of the current offer? How to choose the right products?

1 - Can the microorganism you buy be easily identified?

First of all, when you buy a product, you must always be able to identify what you are buying.

Microorganisms are characterized by their genus, species and strain.

Genus, species, strain must always appear on the label.

2 - Why the notion of strain is essential

The quality of a microorganism is also influenced by its strain.

A few types : Lactobacillus, Bacillus, Pseudomonas, Trichoderma, Chlonostachys, Glomus..

Within the same genus there are then several species: Bacillus cereus, Bacillus subtilis

Within the same species one is able to distinguish the strain, generally it is a series of letters and numbers: Bacillus amyloliquefaciens IT45 ; Clonostachys rosea J1446

This notion has recently demonstrated its importance in the coronavirus crisis, where its significance regarding the transmissibility or virulence of the same virus can be demonstrated.

If you find efficacy in a product, you will not be able to replace it with a product containing a microorganism of the same genus or species, however, it could be replaced with a different strain.

Your manufacturer must always guarantee the same strain.

It is the strain that determines the efficacy and absence of toxicity of a microorganism.

3 - What concentration is optimal?

Microorganisms are everywhere. They can be found on our skin, in our body – for example we know today that our body hosts more microorganisms than the body cells (in our intestines, on our skin, and even in our saliva, which is also saturated with them at a rate of108 CFUs/milliliter of saliva) – they are found everywhere on earth, from the tops of the highest mountains to the depths of the oceans, in the clouds, the sand etc…

So saying that a product – let’s take a fertilizer as an example – contains microorganisms is intrinsic. It will always contain some.  The real question is, how much does it contain?

If we want to be able to influence an environment with a contribution of microorganisms of agronomic interest, it will be necessary to provide the right concentration.

The question is obviously complicated, because agronomy is not exactly a science and can vary according to different parameters, making it difficult to come up with a single answer. However, our experience of more than 10 years allowed us to note that below a contribution of 2.1012 CFU / ha (=7.10^11 CFU / ac), the results are too often random

Your supplier must always indicate the guaranteed microorganism content on the label.

What are Colonial Forming Units (CFUs)?

Microorganisms are not counted in kg or tone but in CFU /g: Colony Forming Units per gram of gross product. CFUs define the number of viable bacteria or fungi capable of multiplying (and thus forming a colony).

A little math?

To give an idea, a bacterial population at 106 CFU/g in a product can be considered a contaminant, i.e., a negligible quantity.

In microbiology, bacteria are most often expressed in billions of CFU/g (109)

The concentration must always be stated on the product label.

4 - How long can I keep the product?

Microorganisms are living beings and depending on their composition and are more or less sensitive to the environment (temperature, pressure, osmotic pressure, humidity, etc.).

For example, bacteria of the genus Bacillus and most of the structures that make up filamentous fungi are fragile and can hardly be kept for a long time in humid environments.  However, these microorganisms can adopt a form capable of resisting a wide variety of stresses: spores.

Current technologies allow us to produce high concentration of microorganisms in the form of spores, allowing us to preserve them for a longer period. They will only germinate when they are in favorable conditions and environment.

Beware of aqueous liquid forms which are often not very stable.

Find out from the supplier and check for yourself (on the internet or through your own knowledge) the storage sensitivity of the microorganism (genus, species, strain) you wish to purchase…

The shelf life or use-by date must be present on the label.

5 - Quand et comment appliquer un produit à base de micro-organismes?

The instructions are crucial for the effectiveness of the product. An application at the right time in the right place and with the right amount of product will influence its effectiveness. For this you should pay special attention to the following points:

  • Preparation
  • Rate of application
  • The time of application (generally microorganisms like humid conditions and temperatures that are neither too cold nor too hot, in spring or fall)
  • Application mode / equipment
  • The area where to apply the product (area close to the roots, on the seeds, on the foliage…). To each microorganism its preferred place of life and therefore its lifespan.
  • Number of applications. Some microorganisms such as mycorrhizal fungi will become durably associated with the plant, while others have a more limited lifespan as they are quickly challenged by native microorganisms and repeated applications will be necessary.

Microorganisms are technical products, so it is essential that the preparation and application instructions are followed.

Rate and instructions for use should always be included on the label.

6 - What are the properties of microorganisms?

Microorganisms are not traditional active ingredients or fertilizers. They are genuine partners of crops that weave complex relationships with them that go far beyond the function for which they are selected.

But they cannot solve all problems on their own! Generally, they each have their own specificities.

For example, in order to mineralize organic matter, applying microorganisms is not enough. A group of factors come into play. Starting with fungi, actinomycetes and then bacteria.

At Lallemand, we carry out scientific partnerships all over the world, especially with universities and research institutes, in order to study many microorganisms, their function in the soil and their interaction with plants. We use genetic screening to select strains of agronomic interest and offer them to growers.

A microorganism's properties must be clearly stated on the label.

7 - Who produced them?

Producing high concentrations of specific desired microorganisms, ensuring their stability and efficiency without fermenting pathogens which may have been found there by accident, involves highly specialized processes.

Some specialized and recognized companies can offer quality inoculant. They are equipped with fermenters that allow all parameters to be adjusted as precisely as possible for optimal fermentation of each microorganism. Each microorganism has its own requirements that must first be discovered. Some like to multiply in atmospheres rich in oxygen (or not), some require specific nutrients (trace elements), a certain pressure, a certain brightness, etc…

They must then be prepared so that they last as long as possible, remain alive, stable, even when applied in the field.

It is a very specialized profession that cannot be improvised and unfortunately, there are producers, both small and industrial, who flout good practices and sometimes even regulatory requirements by marketing “snake oil” products that contribute to tainting the benefits of microorganisms.

At Lallemand we produce our microorganisms in our own plants around the world. Our laboratories and our pilot plant in Blagnac (31) allow us to formulate our microorganisms in order to offer the most concentrated products at a competitive price.

If you would like to know more, you can take a virtual tour of our factory in Salutagüse, Estonia:


The producer must be clearly indicated on the label.

8 - Since they are naturally present, why add microorganisms?

While it is true that plants and microorganisms have lived in harmony since the dawn of time, these relationships took around hundreds of years to develop.

By shaping the landscape and creating new biotopes on important territories, agriculture has disrupted all pre-existing balances. This is almost instantaneous on the scale of time required to set up a stable ecosystem (minimum 50 years according to IDDR) nothing compared against the time required to set up a symbiosis or mutualism by co-evolution which requires several thousand years!

It is unlikely that agricultural plants will ever be able to naturally recreate an optimal microbial ecosystem within a few months (or even a few years).

By offering farmers microorganisms that are of interest for crops, the aim is to complement certain functions of the plant in areas of nutrition and resistance to abiotic and biotic stresses.

By combining two types of genetics in the field we want to create a new hybrid organism (plant / microorganism) with the desire to obtain a heterosis effect.

But beyond possible inoculations, we believe that plant rotations and successions at the plot level must also be considered as an ecosystem. This approach acquires its full economic and technical value only if it is associated with a system of fertilization (mineral and organic), of soil tillage rotation, in order to better express the genetic potential of the plant and of the associated microorganism(s).

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Stay in the loop - part 2