Question

Parker et al. (1951) introduced the concept of Nutrient Index Value (NIV) to describe the fertility status of soils for the purpose of mapping. The NIV value of medium nutrient status is:

• A. 0.5-1.0
• B. 1.0-1.5
• C. 1.5-2.0
• D. 1.5-2.5

Hint:

Remember NIV can only run from 1 (all low) to 3 (all high), so a band below 1 cannot be right.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The Nutrient Index Value (NIV) is a way of scoring how fertile a set of soil samples is, using a weighted count of how many samples fall in the low, medium, and high nutrient categories. We need to know which band of NIV values counts as medium fertility.

Step 2: Key Formula or Approach:
NIV is calculated as:
\[ NIV = \frac{(N_L \times 1) + (N_M \times 2) + (N_H \times 3)}{N} \]
where \(N_L, N_M, N_H\) are the number of samples tested low, medium, and high, and \(N\) is the total number of samples. Because of this weighting, NIV can only range from 1 (every sample low) to 3 (every sample high).

Step 3: Detailed Explanation:
Values close to 1 mean most samples are low in that nutrient, and values close to 3 mean most are high.
The medium fertility class sits in the middle stretch of this 1 to 3 scale, and soil fertility mapping practice places this medium band at 1.5 to 2.5.
Option 1 (0.5-1.0) falls below the possible range of the index altogether, so it cannot be right. Option 2 (1.0-1.5) and option 3 (1.5-2.0) both describe bands that are narrower than, or shifted below, the accepted medium range.

Step 4: Final Answer:
The NIV band for medium nutrient status is 1.5 to 2.5.
\[ \boxed{1.5-2.5} \]