Nitrogen cycle

Question 1

After harvesting, the remains of crop plants are often ploughed into the soil.
Explain how microorganisms in the soil produce a source of nitrates from these remains.

Answer 1

1. Protein/amino acids/DNA into ammonium compounds / ammonia;
   Accept: any named nitrogen containing compound e.g. urea.
2. By saprobionts;
   Accept: saprophytes.
3. Ammonium/ammonia into nitrite;
4. Nitrite into nitrate;
5. By nitrifying bacteria/microorganisms;