Nutrient index between 1.5 and 2.5 is categorized as

Nutrient index (N. I.) is a measure of the nutrient supplying capacity of soils to plants. It makes it easy to compare soil fertility of different areas of soil as it obtains a single value for each nutrient. It is calculated as a low, medium and high ratings of soil nutrients.
A nutrient index value below 1.5 is categorized as low.
The nutrient index between 1.5 and 2.5 is categorized as Medium.
A nutrient index value greater than 2.5, refers to a fertility status being high.