Instantiate a particle emitter when object touches ground.

I was wondering how I should approach making it when my "bullet" hits the ground that it instantiates a one shot particle emitter. Here is my code so far, but I dont want it to be on a trigger.

var explodePrefab : Transform;

function OnTriggerEnter(other : Collider)
{
    if(other.gameObject.name == "ground")
    {
        var explode = Instantiate(explodePrefab ,transform.position ,Quaternion.identity);
        Destroy (explode, 0.5); 
    }
}

Another option is to use OnCollisionEnter:

http://unity3d.com/support/documentation/ScriptReference/Collider.OnCollisionEnter.html