(a(i))[1]
State the name given to this process in the nitrogen cycle.
(a(ii))[2]
In agriculture, this reaction may be harmful. Explain why.
(b(i))[1]
Name the process carried out by soil bacteria that produces nitrate ions.
(b(ii))[2]
Suggest how bacteria such as $\textit{Pseudomonas stutzeri}$ can be used in purifying water for drinking.
(c)[4]
In recent years, flooding of agricultural land worldwide has increased. Explain why crop yields are often much lower even after the flood water has gone.