Question Bank • QB_SWCE_ADV_158 NAT • 1 Mark

Section 4: Soil and Water Conservation Engineering

Soil and Water Erosion

Subtopic: Soil loss estimation

Question Statement:

Under the Universal Soil Loss Equation, adopting a dense cover crop with residue mulching reduces the crop management factor $C$ from $0.40$ to $0.10$. Assuming all other parameters ($R, K, LS, P$) remain strictly constant, the percentage reduction in annual soil loss is ________ $\text{\%}$ (answer in integer).

Answer Key:

75

Step-by-Step Solution & Explanation

1. In USLE, soil loss is directly proportional to $C$: $A_1 \propto C_1 = 0.40, \quad A_2 \propto C_2 = 0.10$ 2. Percentage reduction in soil loss: $\text{Reduction (\%)} = \frac{A_1 - A_2}{A_1} \times 100\% = \frac{C_1 - C_2}{C_1} \times 100\%$ $\text{Reduction} = \frac{0.40 - 0.10}{0.40} \times 100\% = \frac{0.30}{0.40} \times 100\% = 75\%$
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