Biological nitrogen fixation Increased legume productivity through Innovative Symbiotic Agricultural Technology

Authors: Alicia Geyer (Head Microbiologist) & SB Coetzee (Plant pathologist)

Nitrogen – anything but lifeless

The element nitrogen was called “azote” by the French chemist  Antoine Lavoisie, meaning “without life”. On the contrary, it has been proven that everything with life does contain this element. Crop productivity is significantly affected by the availability of nitrogen to the plant.Nitrogen is an important macronutrient, which plays an important role in the growth and development of plants. All essential processes in the plant are associated with proteins and enzymes, of which nitrogen is a key building block. Nitrogen-like fertilizer production and over-utilization have a large economic and environmental cost due to the energy-intensive production process, the influence on air and water quality, soil and water acidification and climate change. There are significant potential gains to reduce our dependence on nitrogen fertilization in agriculture.

Biological nitrogen fixation – environmentally friendly solution to address nitrogen deficiencies and increase crop production

Emphasis is placed on environmentally sustainable agriculture, which draws attention to the use of renewable resources and therefore nitrogen obtained from a process called biological nitrogen fixation (BNF). BNF is the only natural process that converts atmospheric nitrogen into a biologically useful form. The ability of legumes to fix atmospheric nitrogen comes from the symbiotic (meaning “living together”) relationship that it forms with specialized soil-borne bacteria, called rhizobia. This symbiotic interaction is very host specific in that each rhizobium strain can only associate with a limited number of host plant species.This process requires the production of specific communication signaling molecules by both the bacteria and the plant and culminates in the formation of a highly specialized plant root structure called a root nodule.

Figure 1: The effect of symbiotic nitrogen bonding between rhizobium and soybean plants
a.) Above ground visual difference in the growth of soybeans, the untreated control is yellow and is stunted compared to the MBFi treated soybeans
b.) The underground difference between treated and untreated soybeans, note the difference in number and sizes of the nodules on the main and lateral roots.
Figure 2: The difference between technologically advanced inoculant versus low quality inoculant)
a.)Show sub-optimal nodulation on the side roots of low quality inoculant.
b.) Demonstrates excellent nodulation on the main and lateral roots of a technologically advanced inoculant containing signal generation and membrane protection technology.

This nodule creates a habitat for the nitrogen-fixing bacteria to convert atmospheric nitrogen into ammonia and in return the plant provides the bacteria with carbohydrates and protection. Under favorable conditions and limited soil nitrogen, this interaction can lead to hundreds of nodules on the root system, which provide the host legume with enough nitrogen to complete the life cycle.To ensure good nitrogen fixation, it is necessary to inoculate the legume with the correct bacterial strain before planting the seeds. However, rhizobium inoculants face several obstacles that can drastically affect their effectiveness. 

Factors affecting the effectiveness of rhizobium inoculants.

Rhizobium survival on seed is affected by dehydration, toxic seed coat factors, poor adhesion, and high seed storage temperatures. Once incorporated into the soil, conditions such as soil pH, temperature and salinity greatly affect the survival of rhizobium.To reach the full potential of bacterial inoculants, the product must 1) contain the correct rhizobium strain, 2) be free from unwanted microbial contamination, 3) have a long shelf life, 4) have a high concentration contain bacteria, 5) be appropriately packaged and stored and 6) have the ability to survive under adverse conditions.

Biotechnologically advanced range of inoculants – reliable results in a changing environment

MBFi has developed a range of bacterial inoculants that give the farmer flexibility and peace of mind when planting under different environmental conditions. Various technologies have been incorporated into this product range, providing the producer with robust products that deliver a high concentration of viable bacteria to each seed and ensure maximum efficiency.These technologies prevent the bacteria from being affected by adverse environmental conditions to provide excellent performance for the farmer. These technologies include: 

  • OSMO protection technology: The inclusion of OSMO preservatives enables the bacteria to survive longer on the seed surface and leads to better adaptation in different agricultural environments once incorporated into the soil. This is due to the higher tolerance of the cells to adverse conditions such as water and chemical stress, that the bacteria survive better. A higher survival rate ensures maximum nitrogen fixation, which improves crop yield and seed protein content
  • Signal generation technology: This technology allows for increased generation of molecular communication signals between the bacteria and legumes, which leads to a rapid start of communication between rhizobia and the legume.  This means less time to form nodules as well as less time spent in the harsh soil environment. Biological nitrogen fixation is not only facilitated, but the resistance of plants to diseases is improved, the tolerance of the crop to stressful conditions is increased and seed germination and plant development is stimulated.
  • Microbial membrane protection technology (MMP): Professional seed inoculation by commercial seed coaters offers producers a convenient and useful product. However, the biggest problem facing the seed coating industry is the poor survival of the inoculant on the seed. With MMP technology, seeds can be treated up to 60 days before sowing, even when used in combination with traditional chemical fungicides and insecticides. This technology enables the seed industry to reassure the producer to sow high quality seed.
  • O2 packaging: All MBFi inoculants are placed in O2 packaging to ensure that the rhizobia metabolically remain active during the storage period of the product. Waste gases such as carbon dioxide can be released from the packaging and oxygen needed for respiratory purposes can enter the packaging and be used by the active rhizobia for metabolic activities.All these separate technological advances play a major role in protecting the rhizobia during packaging, storage and survival leading to improved nodulation and ultimately increased efficiency and yields for the farmer.

All these separate technological advances play a major role in protecting the rhizobia during packaging, storage and survival leading to improved nodulation and ultimately increased efficiency and yields for the farmer.