Photo Caroline de Rauglaudre

by Caroline de Rauglaudre

Communication manager


Why use products made of microorganisms in agriculture when there are already billions of them in soil?

This is one of the questions that comes up regularly and to answer it correctly, we have chosen to present some scientific elements

While it is true that plants and microorganisms have lived in harmony since the dawn of time, these relationships took dozen or even hundreds of years to develop.
Without us realizing it, agriculture has disrupted (and is still disrupting) balances that took a long time to be established.

 

1 - To save time

Let’s take a tangible example, the nitrogen-fixing bacteria, Rhizobia leguminosarum.

Legumes have the ability to fix nitrogen from the air through their association with bacteria of the Rhizobium genus.

When starting with a legume crop, the soil will have little Rhizobium in it, as these bacteria had no partner to establish a symbiosis with before. Note that Rhizobia is different depending on each legume, for example a soy Rhizobia will not be able to establish a symbiosis with a pea (and vice versa).

Naturally, bacteria will eventually arrive, through contamination by seedlings for example, and if in a conducive environment, they will multiply. But this process will take time (tens to hundreds of years).

In this context, inoculating will save you time.

2 - To associate more efficient partners to crops.

 

Efficiency or competitiveness, why should you choose?

Since the 1980s, scientific publications have shown that native strains are often the most competitive but not necessarily the most efficient, namely those that will lead the plant to produce the most biomass.

The point of inoculating is to introduce competitive AND efficient strains to ensure that the crop is partnered with the best choice.

In the diagram below we can see that the turquoise strains are very competitive and they are often the ones that will succeed in establishing symbioses. On the other hand, they are less efficient than others in producing biomass.

Competitiveness / Efficiency of different microorganisms strains Example of difference in the ability to form nodules and efficiency of 5 strains of Rlv on 18 different pea varieties. Bourion et al,. 2018 Frontiers Plant Sci.

 

Microbiome evolution over the last 50 years

Another particularly interesting study from the University of Illinois published on March 10, 2021 presents the microbiome evolution regarding maze rhizosphere from 1949 to the present day.

In this study, we see that the microbiome has lost its capacity to fix atmospheric nitrogen, which is logical because when fed with mineral fertilizers, the plant requires less assistance from bacteria playing this role.

On the other hand, over the last 50 years, maze has been using denitrifying bacteria to release mineral nitrogen.

Microbiome evolution / maize varietal selection. avela, A., O. Bohn, M. & D. Kent, A. Maize germplasm chronosequence shows crop breeding history impacts recruitment of the rhizosphere microbiome. ISME J (2021). Published 10 March 2021

 

This study demonstrates the impact of agricultural practices over the past 50 years, which have favored and even selected a type of microbiome in soils.  This, without us being aware of it.

However, this microbiome will not necessarily be the most efficient in view of new practices, and it will take many years before it adapts again.

Today’s technologies allow us to offer microbial partners selected for their agronomic properties much more quickly, accelerating a process that would naturally take much longer to complete.

Accelerate a process that nature would carry out over a very long time

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