Growing of  crops year after year results in the depletion of certain nutrients. The soil becomes deficient every year. If these nutrients are not replenished, the soil will become unfit for cultivation and land may become barren. Hence, replenishment of soil is essential.

The two natural ways of soil replenishment are:

(i) Crop rotation i.e., rotation of crops. In this practice, different crops having varied requirements of nutrients are grown on the same land during different seasons. So that the soil is not depleted of any particular nutrient all the time, often a legume crop e.g., pea, gram, pulses etc. are grown alternately to replenish the soil.

(ii) Leaving the agricultural land uncultivated for one or two seasons.This helps the soil to regain its richness.