Leaching requirement can be estimated by formula

Leaching is the process of loss of soluble substances and colloids from the top layer of soil by percolating precipitation.
In agriculture, leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation.
The leaching requirement of any soil can be estimated by the formula:
$${\text{LR}} = \frac{{{\text{E}}{{\text{C}}_{{\text{iw}}}}}}{{{\text{E}}{{\text{C}}_{{\text{dw}}}}}}$$