Question

How will nutrients be replenished in the soil?

Answer 1

Nutrients are replenished in soil by Natural and artificial means.
Natural means:
1) Action of micro-organisms

Nutrients are replenished by different microorganism that are found in the soil . They break down the dead and decaying matter, and convert them into nutrients. The decaying plants tend to slowly break down into the basic soil nutrients over a period of time.
Some micro-organisms also produce nutrients directly, like nitrogen fixing bacteria in soil

2) Plant - microbe interaction.

Plants like peas , with help of bacteria, can produce nutients and replenish soil. Rhizobium in roots of pea plant is an example.

3) Rains:
During lightening, Nitrogen is oxidised, and oxides of nitrogen comes down in rain water to replenish soil.

4) Natural calamities:
Floods bring a lot of fertile soil and nutrients with it.
Volcanic eruption brings a lot of nutrients from earth's inner layers.

Artificial means :

These are man made ways to replenish soil. Addition of fertilisers are an example.