You need chapters describing the issues, the indices and why you chose a particular index in relation to the soils to which it was applied. Then results, discussion and conclusion. Can your supervisor not provide advice?

Here is a possible structure:

- Abstract (Write this last; summary and results in a nutshell)

- Introduction (For an educated stranger who doesn't know what you did)

- Materials and Methods (What you did and what you used in doing it)

- Results (What happened? What worked? What didn't work?)

- Conclusions (Therefore, we can conclude [what?] and [what] should be the next step in this research.