What process converts nitrogen into ammonium (NH4) and nitrate (NO3) for plant use?

The process that converts nitrogen gas from the atmosphere into ammonium (NH4) and nitrate (NO3) forms that plants can readily utilize is nitrogen fixation. This process is primarily carried out by certain bacteria, including those that live in the root nodules of legumes, as well as by free-living soil bacteria. These microorganisms convert atmospheric nitrogen (N2), which is not directly usable by plants, into compounds that can be assimilated.

Nitrogen fixation is crucial for the nitrogen cycle, as it enriches the soil with these forms of nitrogen, making them available for plant uptake, which is essential for producing proteins and nucleic acids in plants. Without nitrogen fixation, plants would suffer from nitrogen deficiency, leading to poor growth and reduced agricultural yields.

The other options refer to different processes: nutrient cycling involves the recycling of nutrients within the ecosystem, photosynthesis is the process by which plants convert sunlight into energy, and decomposition involves the breakdown of organic matter, returning nutrients to the soil but not specifically converting atmospheric nitrogen.