The process through which soil bacteria convert nitrogen compounds in soil is called nitrogen fixation. Nitrogen fixation is the biological process by which certain bacteria, known as nitrogen-fixing bacteria or diazotrophs, convert atmospheric nitrogen (N2) into forms that can be utilized by plants, such as ammonium (NH4+) or nitrate (NO3-). This conversion is essential for maintaining an adequate supply of nitrogen in the soil, as atmospheric nitrogen is largely inaccessible to plants in its gaseous form.

Nitrogen-fixing bacteria form symbiotic relationships with leguminous plants (e.g., peas, beans, soybeans) through nodules that develop on the plant roots. Within these nodules, bacteria convert atmospheric nitrogen into ammonium, which is then utilized by the host plant for growth and development. This symbiotic relationship benefits both the bacteria and the plants, as the bacteria receive a source of energy and carbon compounds from the plants, while the plants receive a supply of fixed nitrogen.

Apart from symbiotic nitrogen fixation, there are also free-living nitrogen-fixing bacteria that can fix atmospheric nitrogen in the soil. These bacteria exist independently in the soil and can convert atmospheric nitrogen into forms that are accessible to plants. Examples of free-living nitrogen-fixing bacteria include species from the genera Azotobacter and Azospirillum.

Regarding the role of blue-green algae (cyanobacteria) in the nitrogen economy of Indian agriculture, they play a significant role in nitrogen fixation, particularly in paddy fields. In flooded paddy fields, blue-green algae (e.g., Anabaena, Nostoc, and Aulosira) form a symbiotic relationship with rice plants. The algae reside in the water-filled spaces between the rice plants and fix atmospheric nitrogen, providing a natural source of nitrogen to the rice crop. This reduces the reliance on synthetic nitrogen fertilizers, leading to more sustainable agricultural practices.

Blue-green algae contribute to the nitrogen economy of Indian agriculture in several ways:

The presence of blue-green algae in paddy fields is often encouraged through the practice of maintaining a flooded or waterlogged environment, as these algae thrive in such conditions. However, it is important to note that the effectiveness of blue-green algae in nitrogen fixation can be influenced by various factors, including nutrient availability, pH levels, and competition with other organisms. Therefore, proper management practices and maintaining suitable conditions are crucial to maximize the benefits of blue-green algae in the nitrogen economy of Indian agriculture.

Dr Md Abdullah Al Masud thank you for your contribution to the discussion

Nitrifying bacteria in the soil convert ammonia into nitrite (NO2-) and then into nitrate (NO3-). This process is called nitrification. Compounds such as nitrate, nitrite, ammonia and ammonium can be taken up from soils by plants and then used in the formation of plant and animal proteins. Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere. Dinitrogen gas (N2) is the ultimate end product of denitrification, but other intermediate gaseous forms of nitrogen exist. Denitrifying bacteria convert the nitrate back into nitrogen gas, which reenters the atmosphere. Nitrogen from runoff and fertilizers enters the ocean, where it enters marine food webs. Bacteria and fungi present in the soil convert nitrates into nitrogen gas which goes back into the atmosphere. This process is called denitrification. Nitrification is an essential process as it helps to provide nitrates to plants which act as a source of nitrogen. Denitrification is an important process that ensures the cyclic movement of nitrogen from the atmosphere to the soil, plants, and back to the atmosphere. When nitrogen nutrients have served their purpose in plants and animals, specialized decomposing bacteria will start a process called ammonification, to convert them back into ammonia and water-soluble ammonium salts. Nitrogen is thus an essential nutrient for all life-forms. The nitrogen molecules present in air can be converted into nitrates and nitrites by a biological process of nitrogen-fixing bacteria present in the soil. The process of biological fixation of nitrogen is called as nitrogen-fixation. Rhizobium is the type of bacteria which is found in the roots of leguminous plants and converts atmospheric nitrogen into nitrates.Nitrifying bacterium, plural Nitrifying Bacteria, any of a small group of aerobic bacteria that use inorganic chemicals as an energy source. They are microorganisms that are important in the nitrogen cycle as converters of soil ammonia to nitrates, compounds usable by plants. nitrifying bacterium, plural Nitrifying Bacteria, any of a small group of aerobic bacteria (family Nitrobacteraceae) that use inorganic chemicals as an energy source. They are microorganisms that are important in the nitrogen cycle as converters of soil ammonia to nitrates, compounds usable by plants.Nitrogen is converted from atmospheric nitrogen (N2) into usable forms, such as NO2-, in a process known as fixation. The majority of nitrogen is fixed by bacteria, most of which are symbiotic with plants. Recently fixed ammonia is then converted to biologically useful forms by specialized bacteria. BGA fix atmospheric nitrogen and supply it to plants thereby having the capacity to reduce the consumption of urea. When they fix carbon from carbon dioxide, some blue green algae fix dinitrogen from the atmosphere. They are called nitrogen-fixing blue green algae and are inclusive of symbiotic and free living forms. Blue green algae are photosynthetic; some can carry out nitrogen fixation. They are important in agriculture as they can metabolize molecular nitrogen, solubilise insoluble phosphates, improve physical and chemical nature of soil and also add organic matter to the soil. They also produce certain Plant Growth Regulators which has a positive effect on crop growth and crop yield. The propagation of blue green algae will not only enrich the nitrogen status of the soil by their fixation process but also provide organic matter and biologically potent substances for plant growth. These algae form a living constituent of the soil biotype and continue their activity year after year. Cyanobacteria play an important role in the management of the nutrient in the soil as they fix the free atmospheric nitrogen and also produce the organic substances and maintain the soil structure. They enrich the nitrogen content of the soil thus acting as a natural fertilizer. They replenish the soil with the nitrogenous compounds and hence are useful in agriculture.