Science

Beneficial microbes are a large group of organisms that can be used as soil inoculants to increase the microbial diversity of soils, improve soil’s quality, health, and the growth, yield, and performance of crops. These microorganisms are sometimes unknown or not very well identified and the beneficial effects are difficult to predict.

The beneficial microorganisms can help improve the effect of management practices such as crop rotations, incorporation of organic amendments, conservation tillage, crop residue recycling, and biocontrol of pests.

Bacteria are only observable when they grow in colonies on nutrient agar or under the light and electronic microscopes. Bacteria carry out metabolic activities such as respiration, photosynthesis, and the synthesis of biological macromolecules. Bacteria have the ability to form a resting spore, which allow them to survive extreme periods of heat, cold, and desiccation.

How do beneficial microorganisms build soil structure?

Along with the fungi, bacteria are important decomposers in the ecosystem; they digest the organic matter in the soils into smaller nutrient components, which are then available to the plants. Bacteria produce enzymes that allow them to digest the different forms of organic matter compounds. The humic compounds and organic glues (extracellular polysaccharides), secreted by the microorganisms bind soil particles together into aggregates and in this way increase the soil porosity and soil structure. Soils with good structure and porosity will provide outstanding conditions for plant growth.

Plants use carbon dioxide for photosynthesis, but they also use oxygen for respiration, which is the process whereby plants break down stored sugars and starches to use as the energy for growth. Plants get their oxygen by absorbing it in the root zone. Soils that have a poor soil structure will not have enough oxygen to successfully carry out respiration activities and do their best.

Soils with poor structure can greatly improve when a Microbial Soil Conditioner is incorporated into the soil. The beneficial microbes will then break down soil compounds, release organic glues, and facilitate the soil particles to re-aggregate, improving the soil porosity and structure. In this way, soils with a good structure will provide plants with the necessary oxygen in the root zone, as there will be an abundance of spaces for oxygen. A good soil structure will promote root growth and distribution, aeration and water penetration into the root zone.

It can be especially valuable to add Bactivate Microbial Soil Conditioner to the soil to improve its porosity and build its structure as these two factors will improve the soil-plant relationship and gain a superior plant establishment.

How do beneficial microorganisms improve plant growth?

Many bacteria, called ‘Plant-growth promoting rhizobacteria’ can encourage plant growth. They encourage plant growth directly and/or indirectly by (1) producing plant regulators, (2) facilitating nutrient uptake, (3) accelerating mineralization, (4) reducing plant stress, (5) providing nitrogen fixation, (6) promoting other beneficial microorganisms such as ‘mycorrhizal fungi’, (7) suppressing plant diseases, and (8) functioning as nematicides and insecticides. Many of the ‘Plant-growth promoting rhizobacteria’ are fluorescent pseudomonads (Pseudomonas fluorescens), but other bacteria, Bacillus sp., are known as well.

Many wide-ranging beneficial Bacillus species have been formulated into Bactivate Microbial Soil Conditioner and are all set to help plants increase their growth and performance.

Additional mechanisms that play a role in plant growth

Increased plant growth also happens because bacteria produce gibberellins. Gibberellins are tetracyclic diterpenoid acids that are involved in a number of developmental and physiological processes in plants. These processes include seed germination, seedling emergence, stem and leaf growth, floral induction and flower and fruit growth. Gibberellins are also implicated in the promotion of root growth, root hair abundance, inhibition of floral bud differentiation in woody angiosperms, regulation of vegetative and reproductive bud dormancy and delay of senescence in many organs of a range of plant species. In most processes gibberellins act in combination with other plant hormones. Gibberellins seem to be secondary metabolites that may play a role as signaling factors towards the host plant.

Bacteria for Nitrogen fixing

Nitrogen is an essential plant nutrient and its input into the soil is essential to sustain agricultural productivity. However, most of the nitrogen is in the air and unavailable to plants.

Bacteria are microorganisms that have the capacity to take gaseous nitrogen and combine it with hydrogen to make ammonia, which is readily available to the plant.

Wide-range bacteria fix N2, and by increasing available nitrogen in the rhizosphere, they positively influence root growth and morphology.

The bacterium Bacillus licheniformis, which is present in Bactivate Microbial Soil Conditioner is regarded as a biofertiliser and has extensive colonisation and competitive abilities.

Bacteria for phosphate and potassium solubilisation

It is well known that under acidic or calcareous soil conditions, large amounts of phosphorus are fixed in the soil and are unavailable to the plants. Bacteria and fungi can make insoluble phosphorus become available to the plant. This solubilisation effect is generally due to the production of organic acids that lower the soil pH and bring about the dissolution of bound forms of phosphate. It has been reported that some bacteria may increase yields up to 200-500 kg/ha and thus, 30 to 50 kg of superphosphate fertilizer can be saved.

Two soil bacteria, Bacillus megatherium and Bacillus mucilaginosus, which are also present in Bactivate Microbial Soil Conditioner have attracted the attention of scientists for a long time, as both microorganisms are capable of mobilising phosphate and potassium from the soil minerals, besides fixing N2.

Bacillus megatherium is regarded as a ‘Phosphorus Solubiliser’ microbe. This bacterium produces organic acids, and enzymes that solubilise non-available phosphates into available forms of phosphorous for the plant, thereby improving its nutrition.

Bacillus mucilaginosus is regarded as a ‘Potassium-Decomposing’ bacterium with the ability to produce organic acids that degrade the potassium minerals present in soil such as silicates, apatites and phosphorites and release available forms of potassium . Chinese scientists have extensively studied this bacterium and reported potassium increases in soils of around 33-34%. B. mucilaginosus also produces exopolysaccahrides, which may act as sorbents of heavy metal ions (Nyanikova et al. 2001).

The incorporation of Bactivate Microbial Soil Conditioner containing the two microbes (Bacillus megatherium and Bacillus mucilaginosus) can facilitate a quick-acting phosphate and potassium in soils and make phosphorus and potassium available to the plants for easy uptake, reducing the use of chemical phosphate and potassium fertilizers.

How do beneficial microbes protect plants against plant root pathogens?

Three modes of action can contribute to the protective activity of beneficial microbes: (1) competition for nutrients in soil and the rhizosphere, (2) competition for infection sites and root colonization, and/or (3) induced systemic resistance.