Red plastic table cloth for mulch...

[Tomatovator]

This is the first time I'm using plastic for mulch. I bought a roll of red plastic table cloth from the local food warehouse and so far so good. I've never used plastic before as I've used landscaping fabric that allowed the rain to penetrate. This plastic keeps most of the rain out. I do have a soaker hose under the plastic. How often and for how long should I run it? Any way to tell for sure?