Question

how do replenishment of nutrients like nitrogen and phosphorus take place in the soil ?

Answer 1

The plant nutrients like nitrogen,phosphorus and potassium and present in the soil naturally. When the plants are grown, they absorb thenutrients from the soil due to which the amount of plant nutrients in thesoil goes on decreasing.
The decaying plants tend to slowly break down into the basic soil nutrients over a period of time. Nutrients are replenished by certain different microorganism that are found in the soil or also by the death of certain plants such as the rhizobium bacteria.