Clay Plaster on new Drywall

I am looking at covering my newly hung drywall with a local clay plaster: 1 part clay: 3 parts sand : 1 part fibre.
I have done experiments on some practice pieces to ensure it will adhere OK. Some with a flour/ sand and/or clay precoat to see which one adheres the plaster to the drywall best.
So I am wondering if it is necessary to tape my drywall joints since the plaster will be put on almost a half inch thick when finished the 3 coats or will cracks eventually show up at the joints if I don't tape them?

Decided not to risk it and taped the joints.

It's good that you taped the seams. The plaster will crack along the joints if you don't. Good surface preparation is key to any plaster.

You definately needed to tape the joints.  I would almost go as far as telling you that you probably should use stucco mesh wire as well.  Your plaster may or may not adhere properly, especially over time, when it is just smeared on basically a smooth surface such as drywall.  

I would experiment with scratching the surface of the drywall, to create a ' key' for your clay mix.

If you intend to coat the whole wall with clay it should stick fine.
We had a problem because on the seems they used regular plaster,
and the clay would not stick to it, too powdery.
Stuck to the rest of the drywall great.

Sift the sand so bigger pieces of sand don't cause problems with a smooth appearance.