Agro-biological production is creating extraordinary interest worldwide because it is seen as a more environmentally friendly alternative. It also has the potential to reduce costs by reducing fertilizer consumption and improving yields by creating healthier plants. The aforementioned interest has led several international companies such as Bayer, BASF as well as others such as Agricen (USA), Liventia (Mexico) to develop their own product lines.
The following are the benefits that microorganisms bring to the soil:
1) Soil Improvement
Bacteria are responsible for nitrogen fixation, transforming the atmospheric nitrogen into ammonium, so that it can be incorporated into the rhizosphere and in turn the nitrifying bacteria make it into nitrates (NO3) that can be assimilated to plants. It also improves the soil, through the bioconversion of organic solid waste, improving the availability of carbon sources.
Nitrogen-fixing bacteria form symbiotic associations with the roots of legumes like clover and lupine, and trees such as alder and locust. Visible nodules are created where bacteria infect a growing root hair. The plant supplies simple carbon compounds to the bacteria, and the bacteria convert nitrogen (N2) from air into a form the plant host can use. When leaves or roots from the host plant decompose, soil nitrogen increases in the surrounding area.
Nitrifying bacteria change ammonium (NH4+) to nitrite (NO2-) then to nitrate (NO3-) – a preferred form of nitrogen for grasses and most row crops. Nitrifying bacteria are suppressed in forest soils, so that most of the nitrogen remains as ammonium.
Some examples of bacteria that fix nitrogen are: Azotobacter, Mycorrhizae, Rhizobium Actinomycetes and Bacillus.
2) Phosphate and other chemicals degrading microorganisms
Bacteria solubilizes phosphorus compounds and other elements, regenerate saturated soils due to the excessive handling of fertilization. Microorganisms are adjuvants in the administration of chemical or organic fertilization. The use of phosphate solubilizing bacteria as inoculants simultaneously increases phosphorous uptake by the plant and crop yield. Strains from the genera Pseudomonas, Bacillus and Rhizobium
are among the most powerful phosphate solubilizers. An important group of bacteria the Actinomycetes decompose a wide array of substrates, but are especially important in degrading recalcitrant (hard-to-decompose) compounds, such as chitin and cellulose, and are active at high pH levels. Fungi are more important in degrading these compounds at low pH. Other bacteria demonstrate a very diverse metabolism, including the ability to degrade organic solvents such as toluene. This ability has been put to use in bioremediation, or the use of microorganisms to degrade environmental pollutants.
For example: Pseudomonas fluorescens and putida, Bacillus subtilis and licheniformis.
3) Bio-enhancers or Phyto-stimulant
Bacteria that Promote Plant Growth
Help restore soil biology and stimulate the growth of species of native microorganisms.. They may also produce compounds (growth factors) that directly increase plant growth. Plant Growth Promoting Bacteria (BPCP), which form a symbiotic association with plants to promote plant development through mechanisms such as the excretion of phytohormones and the biological fixation of nitrogen. It has a direct effect on the root zone of the plants, promoting a greater volume and generation of absorbent pellets.
These plant growth-enhancing bacteria occur naturally in soils, but not always in high enough numbers to have a dramatic effect.
For example: Mycorrhizae, Azospirillum, Pseudomonas, Bacillus, etc.
4) Biocontrol agents or Anti-phytopathogen
They are antagonists of plant pests, parasites or diseases. They may produce a compound that inhibits the growth of pathogens or reduces invasion of the plant by a pathogen. For example: many antibiotics are produced by actinomycetes such as Streptomyces.
For example: Streptomyces, Pseudomonas, Enterobacter, etc.