Tracking Lead Sources

I use Zoho's web-to-lead forms. Right now, all of my web leads are tracked together, which means I can't tell what leads are coming from PPC campaigns vs. organic searches.

Is there a way for me to track this without separate landing pages/forms? For example, can i put a tracking code on my PPC links that will Zoho will capture? I believe SF offered this, but I don't see the ability in Zoho.

How do other people handle this?

Thanks!