1. Ammonia (NH₃): This is the primary product of nitrogen fixation. It is formed when atmospheric nitrogen gas (N₂) is converted into ammonia by nitrogen-fixing organisms.

2. Nitrate (NO₃⁻): Ammonia is further oxidized by nitrifying bacteria to form nitrite (NO₂⁻) and then nitrate (NO₃⁻). This form of nitrogen is readily absorbed by plants.

3. Organic nitrogen compounds: Plants and other organisms assimilate nitrate and other nitrogen compounds to create a variety of organic nitrogen compounds, such as proteins, nucleic acids, and amino acids.

Important note: While nitrogen fixation produces ammonia, it is not directly used by most plants. Ammonia needs to be converted into nitrate (NO₃⁻) before it can be readily absorbed by plants.