Soil Fertility and Microorganisms

Soil fertility isn't directly in the microorganisms themselves, but rather a consequence of their activities. These tiny inhabitants play a crucial role in maintaining and enhancing the ability of soil to nurture plant growth. They contribute to soil fertility in numerous ways, including:

• Nutrient cycling: Microorganisms decompose organic matter and release essential nutrients like nitrogen, phosphorus, and potassium, making them available for plants to absorb.
• Nitrogen fixation: Certain bacteria convert atmospheric nitrogen into a form usable by plants, fixing nitrogen in the soil.
• Improved soil structure: Microorganisms bind soil particles together, increasing aeration and water retention, both crucial for healthy plant growth.
• Production of growth hormones and antibiotics: Some microorganisms produce substances that stimulate plant growth and suppress harmful pathogens, promoting plant health.

Nitrogen Fixation Champions: Archaea and Bacteria

The majority of nitrogen fixation in soil is performed by a specific group of microorganisms called nitrogen-fixing bacteria. These include:

• Rhizobia: These bacteria form symbiotic relationships with legumes like beans and peas, fixing nitrogen directly in their root nodules.
• Free-living bacteria: These bacteria, such as Azospirillum and Azotobacter, live independently in the soil and fix atmospheric nitrogen.
• Cyanobacteria: These photosynthetic bacteria also contribute to nitrogen fixation, particularly in rice paddies and aquatic environments.

Additionally, a group of single-celled organisms called archaea also contribute to nitrogen fixation, particularly in extreme environments like salt marshes and hot springs.

So, while soil fertility itself isn't in the microorganisms, they are the invisible workhorses that keep the soil healthy and productive, with nitrogen-fixing bacteria and archaea taking the lead in providing plants with the vital element of nitrogen.

Dr Murtadha Shukur thank you for your contribution to discussion

Microorganism like some algae, bacteria fungi are present in the soil. Bacteria and fungi present in the soil feed on dead remains of animals and plants and forms humus (which is rich in nutrients and makes the soil fertile). Thus in this way microorganisms make the soil fertile.Soil microorganisms are responsible for most of the nutrient release from organic matter. When microorganisms decompose organic matter, they use the carbon and nutrients in the organic matter for their own growth. They release excess nutrients into the soil where they can be taken up by plants. Soil microorganisms encompass archaea, bacteria, fungi and protozoa. They are responsible for the majority of enzymatic processes in soil and store energy and nutrients in their biomass. Microbes can make nutrients and minerals in the soil available to plants, produce hormones that spur growth, stimulate the plant immune system and trigger or dampen stress responses. But based on the increased activities done by the bacteria in the soil for the absorption of nutrients by the plants we consider bacteria as the most important organism for soil fertility.Nitrogen fixation is carried out naturally in soil by microorganisms termed diazotrophs that include bacteria, such as Azotobacter, and archaea. Some nitrogen-fixing bacteria have symbiotic relationships with plant groups, especially legumes. Cyanobacterial diazotrophs (nitrogen-fixing organism) forms an important component of phytoplankton community in oligotrophic waters and, hence, contribute significantly in the primary production by fixing nitrogen and making it available for coexisting nondiazotrophic phytoplankton from the oligotrophic.Plants of the pea family, known as legumes, are some of the most important hosts for nitrogen-fixing bacteria, but a number of other plants can also harbour these helpful bacteria. Other nitrogen-fixing bacteria are free-living and do not require a host. They are commonly found in soil or in aquatic environments. Bacteria such as Rhizobium, Azotobacter, and certain blue-green algae present in the soil fix atmospheric nitrogen in the soil. But Rhizobium plays a vital role in nitrogen fixation. The majority of nitrogen fixation in soil is performed by a specific group of microorganisms called nitrogen-fixing bacteria. These include: Rhizobia: These bacteria form symbiotic relationships with legumes like beans and peas, fixing nitrogen directly in their root nodules.