Nutrient index value (Parker, 1952) is calculated from the number of soil samples falling in the category of low (\(\text{N}_l\)), medium (\(\text{N}_m\)) and high (\(\text{N}_h\)) nutrient status and represented by expression as given below:
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To remember the weights, match the status with the numbers:
- Low \(\rightarrow 1\)
- Medium \(\rightarrow 2\)
- High \(\rightarrow 3\)
Sum the products of the sample counts and their weights, then divide by the total number of samples.
\(\text{Nutrient index value (NIV)} = (\text{N}_l + 3\text{N}_m + 2\text{N}_h) / (\text{N}_l + \text{N}_m + \text{N}_h)\)
\(\text{Nutrient index value (NIV)} = (\text{N}_l + 2\text{N}_m + 3\text{N}_h) / (\text{N}_l + \text{N}_m + \text{N}_h)\)
\(\text{Nutrient index value (NIV)} = (3\text{N}_l + 2\text{N}_m + \text{N}_h) / (\text{N}_l + \text{N}_m + \text{N}_h)\)
\(\text{Nutrient index value (NIV)} = (\text{N}_l + \text{N}_m + \text{N}_h) / (\text{N}_l + 2\text{N}_m + \text{N}_h)\)
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The Correct Option isB
Solution and Explanation
Step 1: Understanding the Concept:
The Nutrient Index Value (NIV) is used to evaluate the overall fertility status of a region or soil class based on a set of soil test samples. Step 2: Detailed Explanation:
1. Parker (1952) developed an index where soil samples are categorized into three levels of nutrient availability: Low, Medium, and High.
2. Numerical weights are assigned to each class to calculate a weighted average:
- Weight for Low category (\(\text{N}_l\)) = 1
- Weight for Medium category (\(\text{N}_m\)) = 2
- Weight for High category (\(\text{N}_h\)) = 3
3. The formula for the weighted average is:
\[ \text{NIV} = \frac{(1 \times \text{N}_l) + (2 \times \text{N}_m) + (3 \times \text{N}_h)}{\text{N}_l + \text{N}_m + \text{N}_h} \]
4. This formula corresponds to Option B. Step 3: Final Answer:
The correct expression is \(\text{Nutrient index value (NIV)} = (\text{N}_l + 2\text{N}_m + 3\text{N}_h) / (\text{N}_l + \text{N}_m + \text{N}_h)\).
