Biostimulants are natural substances applied to plants or the rhizosphere to enhance nutrient uptake, nutrient use efficiency, and crop quality.
Fertilizers provide substances to the soil to ensure proper plant growth and increased agricultural productivity. They are essential for the production of food and forages, especially when using high-yield varieties that provide a positive response to nitrogen fertilizers rich in phosphorus and potassium. However, this solution has also become a problem given that the yields of these crops have decreased as a result of poor planning in soil care, an unbalanced application of fertilizers and a continued reduction of organic matter, in addition to poor cultural and/or agronomic practices derived from modern agriculture, also known as Green Revolution.
It is noted that nitrogen is the main limitation to increase productivity in the soil, this coupled with a higher economic value and environmental cost; therefore, currently the agricultural sector is looking for other options that guarantee greater efficiency and better use of nutrients, as a result the so-called biofertilizers (BF) have emerged, which have been generated from biotechnological methods and are introduced to the market as an excellent option.
Today, biofertilizers are recognized under different names, such as bacterial fertilizers, phytostimulants, biopesticides, bioinoculants, among others. But the fact is that they do not have the function of a fertilizer as such, since they do not work directly on the nutrition of the plants, instead they are microorganisms such as bacteria, fungi, and green and blue algae that are packaged in an inert material (vehicle).
BF are microbial inoculants that can be found in solid or liquid formulations, containing live or latent cell strains that are efficient for the fixation of nitrogen, phosphate solubilizers, or celolytic microorganisms used in the application of seeds or roots in order to increase these microorganisms and accelerate microbial processes that increase root growth, and also to provide the availability of nutrients.
In this regard, the availability of nutrients occurs through two main actions: the production of hormones and the suppression of pathogens. When applied to seeds, on the surface of plants, or directly to the soil, BF colonize the rhizosphere or the interior part the plant (endophytes), thus stimulating growth by increasing the supply or availability of nutrients.
Biological nitrogen fixers such as Rhizobium sp, Bradyrhizobium sp, Azobacter sp, and Azospirillum
Phosphorous solubilizers such as Bacillus sp, Pseudomonas sp, Penicillium
sp, Trichoderma sp, and Aspergillius sp.
Phosphate mobilizers such as endomycorrhizal or arbuscular mycorrhizal fungi (AMF), emphasizing Rhizophagus sp, Endogone sp, Gigaspora sp, Acualospora sp, and Scutellispora
Plant Growth Promoting Bacteria (PGPV) or Plant Growth Promoting Rhizobacteria (PGPR) such as Pseudomonas sp, Agrobacterium sp, Bradyrhixobium sp, Azobacter sp, Azospirillum, Streptomyces sp, and Xhanthomonas
The techniques related to biofertilizers are not new; however, they are little known and widespread and, particularly, little standardized; an example of this can be seen in the use of beneficial microorganisms.
It is worth mentioning that microorganisms used in the application of BF play a crucial role since they minimize the impacts of conventional fertilization and ensure the permanence of sustainable agriculture, especially in cases where priority is given to implement conservation measures and reduce environmental impact.
By using microbial BF (mycorrhizae), not only sustainability and agricultural productivity with low environmental impact is ensured, but also an increase in production is achieved, soil fertility is improved, and populations of phytopathogenic microorganisms are reduced. With these contributions, savings are obtained in fertilizers and agrochemical products, thus minimizing costs while implementing components that contribute to the sustainability of agriculture. Undoubtedly, this type of product is a feasible alternative for the partial or total substitution of mineral fertilizers with high environmental costs.