What is the process known as when ammonium is converted to nitrate in soils?

The process when ammonium is converted to nitrate in soils is referred to as nitrification. This is a crucial part of the nitrogen cycle, where ammonia (NH₄⁺) is first oxidized to nitrite (NO₂⁻) by specific types of bacteria, and then further oxidized to nitrate (NO₃⁻) by other bacteria. Nitrate is a form of nitrogen that is readily utilized by plants for growth, making nitrification an essential process in agricultural and natural ecosystems.

This transformation occurs under aerobic conditions and is a key step in making nitrogen accessible to plants after its initial forms, such as ammonium, are produced through processes like decomposition (mineralization) or nitrogen fixation. By converting ammonium to nitrate, nitrification helps to enhance soil fertility and maintain the balance of nitrogen compounds in the environment. Thus, it plays a vital role in both nutrient cycling and agricultural productivity.