Ashraf Aiad with a short post on how to fix the nParticle shadows in Maya when rendering with Mental Ray. The problem appears when we want to disable the nParticles shadow on the ground.

“When rendering particles or nParticles with mental ray for Maya, you will notice that the option to cast shadow has no effect on the render.
For example this scene have a group of objects and you will notice that the spot light with ray trace shadow is casting particle shadow on both cubes and tea pots.”