Different soil compounds exist in the soil and as such tend to either accelerate or decelerate the rate of decomposition of human remains. Hence may alter a soft tissue forensic examination. This questions gears towards the proper understanding the effects of these compounds on both surface and buried remains.
This is a highly complex girls. There shirt answer is "everything" including, importantly, water.
But environmental conditions also factor in - temperature, relative humidity, hydrophilic/hydrophobic, etc.
In researching specific effects you would need to be extremely careful to control all other variables
@Jcu Downs, this is why I want run a test on the soil to ensure all factors are constant before the research study.
I wish to find out all possible soil factors that can decelerate the decomposition rate of any animal remains including humans.