What is nitrogen immobilization?

Nitrogen immobilization refers to the process where inorganic nitrogen, primarily ammonium (NH4+) and nitrate (NO3-), is converted into organic forms by soil microorganisms. This typically occurs during the decomposition of organic matter when microorganisms utilize available nitrogen for growth and metabolism.

When nitrogen is immobilized, it becomes temporarily unavailable to plants because it is now part of the microbial biomass. This process is crucial in nutrient cycling within the soil ecosystem, as it helps to retain nitrogen within the organic matter until it is mineralized back into inorganic forms that plants can uptake.

The other options do not accurately describe nitrogen immobilization. Converting nitrogen into soil forms can happen, but it doesn’t specifically address the microbial action central to immobilization. Loss of nitrogen through leaching pertains to nitrogen that is washed away from the soil, which is a different process. The increase of nitrogen in fertilizers simply relates to the application of nitrogen sources and does not capture the essence of what immobilization involves. Thus, the choice addressing the temporary retention of nitrogen in organic form correctly reflects the scientific understanding of nitrogen immobilization.