what are the five basic processes involved in nitrogen cycle? Please explain..

Your friend is correct,

The main steps of nitrogen cycle are as follows:

Nitrogen fixation:

There are methods that change atmospheric nitrogen into usable forms through the process of nitrogen fixation. Two such methods are given below.

[1]. During lightning and thunder, the high temperature and pressure in the air convert atmospheric nitrogen into oxides of nitrogen that can dissolve in water to produce nitric and nitrous acids. These fall along with rain.

[2]. Certain forms of bacteria are able to convert atmospheric nitrogen into usable forms such as nitrates and nitrites. Such nitrogen fixing bacteria are commonly found in the roots of legumes (plants of pulses) inside special structures called root nodules.

Assimilation:

The plants further absorb the nitrogen from the soil in the form of ammonium or nitrate ions. These plants in turn are eaten by animals resulting in the transfer of the components of nitrogen from plants to animals.

Ammonification:

The death of an animal or a plant returns back this nitrogen in the form of organic matter which is further converted into ammonia because of the action of bacteria or fungi. This process of conversion of organic matter into ammonia is termed as ammonification.

Nitrification:

This ammonia is further converted in the form of nitrates or nitrates by soil-living and other nitrifying bacteria. This process is particularly referred to as nitrification.

Denitrification:

The process of denitrification then returns back these nitrates into the atmosphere in the form of inert nitrogen gas by bacteria such as Pseudomonas, Clostridium etc.

@pooja...Good answer...Keep posting!