Answer: Ammonification and nitrogen fixation.
Step-by-step explanation:
Ammonification is the process where by organic nitrogen is converted ammonia in the soil by bacteria. These occur when bacteria breakdown the remains of dead plants and animals to release organic nitrogen and it is converted to ammonia.
Nitrogen fixation it is the process where atmospheric nitrogen is converted to ammonia or nitrate in the soil, in a way it is absorbed by plants. It is fixed by bacteria in root nodules of leguminous plants or by lightening.