Question

Most plants assimilate nitrogen as nitrate ion. However, ammonia (NH3) is a popular and economical fertilizer. What essential role do bacteria play when ammonia is used as a fertilizer? Do you think any problems might occur when using ammonia in a waterlogged soil lacking oxygen?

Answer 1

Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that cannot fix nitrogen gas (N₂) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food.

The ability to fix nitrogen is found only in certain bacteria and archaea.

• Some live in a symbiotic relationship with plants of the legume family
• Some establish symbiotic relationships with plants other than legumes (e.g., alders).
• Some establish symbiotic relationships with animals, e.g., termites and "shipworms" (wood-eating bivalves).
• Some nitrogen-fixing bacteria live free in the soil.
• Nitrogen-fixing cyanobacteria are essential to maintaining the fertility of semi-aquatic environments like rice paddies.

• Biological nitrogen fixation requires a complex set of enzymes and a huge expenditure of ATP.

  Although the first stable product of the process is ammonia, this is quickly incorporated into protein and other organic nitrogen compounds

Meaning of water logged soil: Submerged soils are soils that are saturated with water for a sufficient long time in a year.The soil is intermittently saturated with water, oxidation of organic matter is slow.

.In submerged soils due to diffusion of oxygen in the water, the organic form nitrogen undergoes minaralization to form NH₄ to NO₂ and NO₂ to NO₃ takes place in the aerobic layer. But in an anaerobic layer the absence of oxygen inhibits the activity of the nitrosomnas microorganisms that oxidizes NH₄ and nitrogen mineralization stops at the ammonical form the accumulation of NH₄ on submerged soils take placed the NH₄ diffuse aerobic volatilization and nitrification the NO₃ nitrogen in aerobic layer diffuses into reduced zone undergoes denitrification to form N_2.The availability of N decreases on submerged conditions due to denitrification, volatilizations of ammonia, ammonium ions fixation by clay minerals leaching and runoff NO₃ and NH₃.