The Importance of Applying a High Quality Microbial Biostimulant

Microbial biostimulants are the newest group of agricultural inputs in agriculture, but also the most unknown product for farmers. They are a subgroup of the heterogeneous family of biostimulants.

A possible definition of microbial biostimulant is: a microorganism (or mix of microorganisms), whose function when applied to seeds, plants, or the rhizosphere, is to stimulate natural processes to enhance/benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, crop quality, and/or yield.


Although the category of microbial biostimulant is very novel for farmers (except for rhizobium inoculants-soybean, which is a separate case that I explain below), scientists have been aware of it for a long time.

The “old name” for microbial biostimulants was PGPR (Plant Growth Promoting Rhizobacteria), a name proposed for the first time by J.W. Kloepper in 1980, who used this term for a bacteria called Pseudomona fluorescens involved in the biological control of pathogens and enhancing plant growth. Later Y. Kapulnik (1981) extended this term to the rhizobacteria capable of promoting plant growth directly. Nowadays the term microbial biostimulant also includes fungi, especially mycorrhizal fungi, one of the most important microbes in agriculture.

I highlighted that soybean inoculants are of special significance amongst biostimulants because their importance was first noticed more than a century ago when imported soya seed grown in the U.S. was “inoculated” by rubbing the seed with soil from China, the home of soybeans. Nowadays every educated soybean farmer knows that the use of high-quality rhizobium inoculant in soybean is essential for high yields.

But the rhizobium-legumes case is exceptional, it is the only known case in nature of such a high direct relationship with crop yield-inoculation. The difference in applying high-quality inoculant or a low-quality is tons of yield per hectare.

But in non-legume crops, such as cereals or horticultural crops, there is also huge room for improvement. There are already microbial biostimulants in the market that can improve yield by 20%-30%.

But this new market has a big problem. There are a lot of “fake” products or “snake oil” products. Companies that do not know anything about microbiology or agronomy sell products in their catalogs claiming all kinds of benefits to crops (e.g., phosphate solubilization, nitrogen fixation, hormone production, biotic stress, abiotic stress), and all with one product, for every single crop… but without any scientific field data to show.

Also there are products that you can buy in online shops, that guarantee that they contain more than 20 different species of fungi and bacteria. Do you know how difficult and expensive it is to guarantee high quality in that kind of product?

To apply low quality products to your seeds or crops is very dangerous and not just for your pocket. Applying a “snake oil” will not help your crop or improve the quality of the crop. If the fermentation of the product is not controlled with a high-quality control process, it can result in contaminations of undesired microbes, that potentially can cause disease in your crop.

In Europe and EEUU new normatives have been approved recently. So we hope it will get these fake products out of the market soon… but for the rest of the world it will take more time.

As a conclusion, microbial biostimulants are products that in the near future will be a common product for farmers, but the industry has to be sure to provide the market with high quality and reliable inoculants.