You can put a normal trampoline in the ground, but it is not advisable. Putting an above-ground trampoline in the ground means that you will not be able to see damage or wear and tear. Plus, it can actually increase deterioration due to contact with damp soil. Finally, removing the safety net can cause springs or other bits to be exposed. In-ground trampolines do minimize the risk of injury from falling, but safety nets are a perfectly good solution!