Soil samples from a fertilized field were tested for ammonium (NH4+) and nitrate (NO3-) over six weeks after fertilizer application.
Which process best explains the inverse trends?
- A
Denitrification: nitrate is converted to N2 gas.
- B
Nitrogen fixation by legumes.
- Ccheck_circle
Nitrification: ammonium is oxidized to nitrate by soil bacteria.
- D
Ammonification: organic matter decomposes to ammonium.
Explanation
Nitrifying bacteria (Nitrosomonas, Nitrobacter) oxidize ammonium first to nitrite, then to nitrate, decreasing ammonium and increasing nitrate over time.