Nitrification is one of the steps in the nitrogen cycle where ammonium is converted to nitrate. First, ammonium is converted to nitrite by specialised bacteria. Other bacterial species are responsible for the conversion of nitrite to nitrate. Nitrate is easily taken up by plants, but it is also susceptible to loss because it doesn’t stick to soil and is quite mobile. It is easily leached from the soil through rain.
University of Waikato