Question Bank • QB_SUB_IDE_0048 NAT • 2 Marks

Section 5: Irrigation and Drainage Engineering

Agricultural Drainage

Subtopic: Leaching requirement and salinity control

Question Statement:

Irrigation water with electrical conductivity $EC_w = 1.5\text{ dS/m}$ is applied to a crop having a soil salinity tolerance threshold of $EC_e = 4.0\text{ dS/m}$. Using the US Salinity Laboratory formula $LR = \frac{EC_w}{5 EC_e - EC_w}$, the Leaching Requirement (fraction, rounded to 3 decimal places) is:

Answer Key:

0.081

Step-by-Step Solution & Explanation

$LR = \frac{1.5}{5(4.0) - 1.5} = \frac{1.5}{20.0 - 1.5} = \frac{1.5}{18.5} = 0.081$
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