Staining My Deck

Last summer I built a large deck in my backyard using pressure treated wood. This spring I would like to stain the wood however I'm not sure if I'm required to sand the wood first before applying the stain or can i just use a pressure washer to remove the dirt, let it dry and apply the stain?

Because of the size of the deck there would be a lot of work involved to sand down the railings. I would prefer to avoid sanding but want the best results that will last the longest. What is the best approach to staining a deck for the first time?

Looking forward to some helpful suggestions...thanks!