What process involves the conversion of atmospheric nitrogen into a usable form for plants?

The conversion of atmospheric nitrogen into a usable form for plants is known as nitrogen fixation. This process is critical because atmospheric nitrogen (N₂) is not directly usable by plants. Instead, nitrogen fixation transforms N₂ into ammonia (NH₃) or related compounds that plants can absorb and utilize for growth.

Nitrogen fixation can occur biologically, through certain bacteria and legumes, or abiotically, through natural phenomena such as lightning. The importance of nitrogen fixation lies in its role in overcoming the nitrogen limitation that many ecosystems face. Without this process, the availability of nitrogen to plants would be severely limited, impacting agricultural productivity and ecosystem health.

While other processes like nitrification, immobilization, and mineralization are essential components of the nitrogen cycle, they serve different functions. Nitrification refers to the conversion of ammonia into nitrites and then nitrates, which plants can also use but does not involve the conversion of atmospheric nitrogen. Immobilization involves the uptake of inorganic nitrogen by microorganisms, effectively locking it up in organic forms. Mineralization is the process by which organic nitrogen is converted back to inorganic forms after decomposition. Each of these processes plays a role in the broader nitrogen cycle but does not specifically address the initial conversion of atmospheric nitrogen into a plant-