I had an old trout in my freezer so I threw it in the shed for a day and then I cut it up and put it in 2 jars and buried it in the shade about 12 inches under the ground. What will result from this? I'm just trying to experiment and mess around some. Do I need a preservative?

my experience if fish will break down very fast compared to other bases. If you want to use it at a certain state you will need to use a preservative to stop the break down. But i think fish has a use at all the different states of decomposition. You have decide what the target animal and the type of reaction your going for.